Merge pull request #366 from OxygenCobalt/dev

Version 3.0.3

.github/workflows/android.yml

@@ -11,22 +11,16 @@ jobs:
     runs-on: ubuntu-latest
     
     steps:
-    - uses: actions/checkout@v3
+    - name: Clone repository
+      uses: actions/checkout@v3
+    - name: Clone submodules
+      run: git submodule update --init --recursive
     - name: Set up JDK 11
       uses: actions/setup-java@v3
       with:
         java-version: '11'
         distribution: 'temurin'
         cache: gradle
-    - name: Set up NDK r21e
-      uses: nttld/setup-ndk@v1.2.0
-      id: setup-ndk
-      with:
-        ndk-version: r21e
-        add-to-path: false
-    - run: python3 prebuild.py
-      env:
-        ANDROID_NDK_HOME: ${{ steps.setup-ndk.outputs.ndk-path }}
     - name: Grant execute permission for gradlew
       run: chmod +x gradlew
     - name: Test app with Gradle

.gitignore

@@ -3,8 +3,6 @@
 local.properties
 build/
 release/
-srclibs/
-libs/
 
 # Studio
 .idea/

.gitmodules

@@ -0,0 +1,4 @@
+[submodule "ExoPlayer"]
+	path = ExoPlayer
+	url = https://github.com/OxygenCobalt/ExoPlayer.git
+	branch = auxio

CHANGELOG.md

@@ -1,5 +1,37 @@
 # Changelog
 
+## 3.0.3
+
+#### What's New
+- Added support for disc subtitles
+- Added support for ALAC files
+- Song properties view now shows tags
+- Added option to control whether articles like "the" are ignored when sorting
+
+#### What's Improved
+- Will now accept zeroed track/disc numbers in the presence of non-zero total
+track/disc fields
+- Music loading has been made slightly faster
+- Improved sort menu usability
+- Fall back to `TXXX:RELEASETYPE` on ID3v2 files
+- Switches and checkboxes have been mildly visually refreshed
+
+#### What's Fixed
+- Fixed non-functioning "repeat all" repeat mode
+- Fixed visual clipping of shuffle button shadow
+- Fixed SeekBar remaining in a "stuck" state if gesture navigation was used
+while selecting it.
+
+#### Dev/Meta
+- Started using dependency injection
+- Started code obsfucation
+- Only bundle audio-related extractors with ExoPlayer
+- Switched to Room for database management
+- Updated to MDC 1.8.0 alpha-01
+- Updated to AGP 7.4.1
+- Updated to Gradle 8.0
+- Updated to ExoPlayer 2.18.3
+
 ## 3.0.2
 
 #### What's New

ExoPlayer

@@ -0,0 +1 @@
+Subproject commit 268d683bab060fff43e75732248416d9bf476ef3

README.md

@@ -2,8 +2,8 @@
 <h1 align="center"><b>Auxio</b></h1>
 <h4 align="center">A simple, rational music player for android.</h4>
 <p align="center">
-    <a href="https://github.com/oxygencobalt/Auxio/releases/tag/v3.0.2">
+    <a href="https://github.com/oxygencobalt/Auxio/releases/tag/v3.0.3">
-        <img alt="Latest Version" src="https://img.shields.io/static/v1?label=tag&message=v3.0.2&color=0D5AF5">
+        <img alt="Latest Version" src="https://img.shields.io/static/v1?label=tag&message=v3.0.3&color=0D5AF5">
     </a>
     <a href="https://github.com/oxygencobalt/Auxio/releases/">
         <img alt="Releases" src="https://img.shields.io/github/downloads/OxygenCobalt/Auxio/total.svg">
@@ -68,12 +68,12 @@ precise/original dates, sort tags, and more
 
 ## Building
 
-Auxio relies on a custom version of ExoPlayer that enables some extra features. So, the build process is as follows:
+Auxio relies on a custom version of ExoPlayer that enables some extra features. This adds some caveats to
-
+the build process:
-1. `cd` into the project directory.
+1. The project uses submodules, so when cloning initially, use `git clone --recurse-submodules` to properly
-2. Run `python3 prebuild.py`, which installs ExoPlayer and it's extensions.
+download in the external code.
-    - The pre-build process only works with \*nix systems. On windows, this process must be done manually.
+2. You are **unable** to build this project on windows, as the custom ExoPlayer build runs shell scripts that
-3. Build the project normally in Android Studio.
+will only work on unix-based systems.
 
 ## Contributing
 

app/build.gradle

@@ -4,16 +4,24 @@ plugins {
     id "androidx.navigation.safeargs.kotlin"
     id "com.diffplug.spotless"
     id "kotlin-parcelize"
+    id "dagger.hilt.android.plugin"
+    id "kotlin-kapt"
+    id 'org.jetbrains.kotlin.android'
 }
 
 android {
     compileSdk 33
+    // NDK is not used in Auxio explicitly (used in the ffmpeg extension), but we need to specify
+    // it here so that binary stripping will work.
+    // TODO: Eventually you might just want to start vendoring the FFMpeg extension so the
+    //  NDK use is unified
+    ndkVersion = "23.2.8568313"
     namespace "org.oxycblt.auxio"
 
     defaultConfig {
         applicationId namespace
-        versionName "3.0.2"
+        versionName "3.0.3"
-        versionCode 26
+        versionCode 27
 
         minSdk 21
         targetSdk 33
@@ -21,14 +29,13 @@ android {
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 
-    // ExoPlayer, AndroidX, and Material Components all need Java 8 to compile.
     compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_8
+        sourceCompatibility JavaVersion.VERSION_11
-        targetCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_11
     }
 
     kotlinOptions {
-        jvmTarget = "1.8"
+        jvmTarget = "11"
         freeCompilerArgs += "-Xjvm-default=all"
     }
 
@@ -42,17 +49,17 @@ android {
             minifyEnabled true
             shrinkResources true
             proguardFiles getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro"
+
+            dependenciesInfo {
+                includeInApk = false
+                includeInBundle = false
+            }
         }
     }
 
     buildFeatures {
         viewBinding true
     }
-
-    dependenciesInfo {
-        includeInApk = false
-        includeInBundle = false
-    }
 }
 
 dependencies {
@@ -66,7 +73,7 @@ dependencies {
 
     // General
     // 1.4.0 is used in order to avoid a ripple bug in material components
-    implementation "androidx.appcompat:appcompat:1.4.0"
+    implementation "androidx.appcompat:appcompat:1.6.1"
     implementation "androidx.core:core-ktx:1.9.0"
     implementation "androidx.activity:activity-ktx:1.6.1"
     implementation "androidx.fragment:fragment-ktx:1.5.5"
@@ -75,6 +82,7 @@ dependencies {
     implementation "androidx.recyclerview:recyclerview:1.2.1"
     implementation "androidx.constraintlayout:constraintlayout:2.1.4"
     implementation "androidx.viewpager2:viewpager2:1.1.0-beta01"
+    implementation 'androidx.core:core-ktx:+'
 
     // Lifecycle
     def lifecycle_version = "2.5.1"
@@ -93,30 +101,38 @@ dependencies {
     // Preferences
     implementation "androidx.preference:preference-ktx:1.2.0"
 
+    // Database
+    def room_version = '2.5.0'
+    implementation "androidx.room:room-runtime:$room_version"
+    kapt "androidx.room:room-compiler:$room_version"
+    implementation "androidx.room:room-ktx:$room_version"
+
     // --- THIRD PARTY ---
 
-    // Exoplayer
+    // Exoplayer (Vendored)
-    // WARNING: THE EXOPLAYER VERSION MUST BE KEPT IN LOCK-STEP WITH THE PRE-BUILD SCRIPT.
+    implementation project(":exoplayer-library-core")
-    // IF NOT, VERY UNFRIENDLY BUILD FAILURES AND CRASHES MAY ENSUE.
+    implementation project(":exoplayer-extension-ffmpeg")
-    implementation("com.google.android.exoplayer:exoplayer-core:2.18.2") {
-        exclude group: "com.google.android.exoplayer", module: "exoplayer-extractor"
-    }
-
-    implementation fileTree(dir: "libs", include: ["library-*.aar"])
-    implementation fileTree(dir: "libs", include: ["extension-*.aar"])
 
     // Image loading
-    implementation "io.coil-kt:coil:2.1.0"
+    implementation 'io.coil-kt:coil-base:2.2.2'
 
     // Material
-    // Locked below 1.7.0-alpha03 to avoid the same ripple bug
+    // TODO: Stuck on 1.8.0-alpha01 until ripple bug with tab layout can be worked around
-    implementation "com.google.android.material:material:1.7.0-alpha02"
+    // TODO: Exactly figure out the conditions that the 1.7.0 ripple bug occurred so you can just
+    //  PR a fix.
+    implementation "com.google.android.material:material:1.8.0-alpha01"
 
-    // Development
+    // Dependency Injection
-    debugImplementation "com.squareup.leakcanary:leakcanary-android:2.9.1"
+    def dagger_version = '2.45'
+    implementation "com.google.dagger:dagger:$dagger_version"
+    kapt "com.google.dagger:dagger-compiler:$dagger_version"
+    implementation "com.google.dagger:hilt-android:$hilt_version"
+    kapt "com.google.dagger:hilt-android-compiler:$hilt_version"
+    // Testing
+    debugImplementation 'com.squareup.leakcanary:leakcanary-android:2.10'
     testImplementation "junit:junit:4.13.2"
-    androidTestImplementation 'androidx.test.ext:junit:1.1.4'
+    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
-    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.0'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
 }
 
 spotless {

app/src/main/java/org/oxycblt/auxio/Auxio.kt

@@ -22,15 +22,9 @@ import android.content.Intent
 import androidx.core.content.pm.ShortcutInfoCompat
 import androidx.core.content.pm.ShortcutManagerCompat
 import androidx.core.graphics.drawable.IconCompat
-import coil.ImageLoader
+import dagger.hilt.android.HiltAndroidApp
-import coil.ImageLoaderFactory
+import javax.inject.Inject
-import coil.request.CachePolicy
 import org.oxycblt.auxio.image.ImageSettings
-import org.oxycblt.auxio.image.extractor.AlbumCoverFetcher
-import org.oxycblt.auxio.image.extractor.ArtistImageFetcher
-import org.oxycblt.auxio.image.extractor.ErrorCrossfadeTransitionFactory
-import org.oxycblt.auxio.image.extractor.GenreImageFetcher
-import org.oxycblt.auxio.image.extractor.MusicKeyer
 import org.oxycblt.auxio.playback.PlaybackSettings
 import org.oxycblt.auxio.ui.UISettings
 
@@ -38,16 +32,22 @@ import org.oxycblt.auxio.ui.UISettings
  * A simple, rational music player for android.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class Auxio : Application(), ImageLoaderFactory {
+@HiltAndroidApp
+class Auxio : Application() {
+    @Inject lateinit var imageSettings: ImageSettings
+    @Inject lateinit var playbackSettings: PlaybackSettings
+    @Inject lateinit var uiSettings: UISettings
+
     override fun onCreate() {
         super.onCreate()
         // Migrate any settings that may have changed in an app update.
-        ImageSettings.from(this).migrate()
+        imageSettings.migrate()
-        PlaybackSettings.from(this).migrate()
+        playbackSettings.migrate()
-        UISettings.from(this).migrate()
+        uiSettings.migrate()
         // Adding static shortcuts in a dynamic manner is better than declaring them
         // manually, as it will properly handle the difference between debug and release
         // Auxio instances.
+        // TODO: Switch to static shortcuts
         ShortcutManagerCompat.addDynamicShortcuts(
             this,
             listOf(
@@ -61,22 +61,6 @@ class Auxio : Application(), ImageLoaderFactory {
                     .build()))
     }
 
-    override fun newImageLoader() =
-        ImageLoader.Builder(applicationContext)
-            .components {
-                // Add fetchers for Music components to make them usable with ImageRequest
-                add(MusicKeyer())
-                add(AlbumCoverFetcher.SongFactory())
-                add(AlbumCoverFetcher.AlbumFactory())
-                add(ArtistImageFetcher.Factory())
-                add(GenreImageFetcher.Factory())
-            }
-            // Use our own crossfade with error drawable support
-            .transitionFactory(ErrorCrossfadeTransitionFactory())
-            // Not downloading anything, so no disk-caching
-            .diskCachePolicy(CachePolicy.DISABLED)
-            .build()
-
     companion object {
         /** The [Intent] name for the "Shuffle All" shortcut. */
         const val INTENT_KEY_SHORTCUT_SHUFFLE = BuildConfig.APPLICATION_ID + ".action.SHUFFLE_ALL"

app/src/main/java/org/oxycblt/auxio/IntegerTable.kt

@@ -31,8 +31,8 @@ object IntegerTable {
     const val VIEW_TYPE_ARTIST = 0xA002
     /** GenreViewHolder */
     const val VIEW_TYPE_GENRE = 0xA003
-    /** HeaderViewHolder */
+    /** BasicHeaderViewHolder */
-    const val VIEW_TYPE_HEADER = 0xA004
+    const val VIEW_TYPE_BASIC_HEADER = 0xA004
     /** SortHeaderViewHolder */
     const val VIEW_TYPE_SORT_HEADER = 0xA005
     /** AlbumDetailViewHolder */

app/src/main/java/org/oxycblt/auxio/MainActivity.kt

@@ -20,17 +20,19 @@ package org.oxycblt.auxio
 import android.content.Intent
 import android.os.Bundle
 import android.view.View
+import androidx.activity.viewModels
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.app.AppCompatDelegate
 import androidx.core.view.WindowCompat
 import androidx.core.view.updatePadding
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import org.oxycblt.auxio.databinding.ActivityMainBinding
 import org.oxycblt.auxio.music.system.IndexerService
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.playback.state.InternalPlayer
 import org.oxycblt.auxio.playback.system.PlaybackService
 import org.oxycblt.auxio.ui.UISettings
-import org.oxycblt.auxio.util.androidViewModels
 import org.oxycblt.auxio.util.isNight
 import org.oxycblt.auxio.util.logD
 import org.oxycblt.auxio.util.systemBarInsetsCompat
@@ -50,8 +52,10 @@ import org.oxycblt.auxio.util.systemBarInsetsCompat
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class MainActivity : AppCompatActivity() {
-    private val playbackModel: PlaybackViewModel by androidViewModels()
+    private val playbackModel: PlaybackViewModel by viewModels()
+    @Inject lateinit var uiSettings: UISettings
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -81,17 +85,16 @@ class MainActivity : AppCompatActivity() {
     }
 
     private fun setupTheme() {
-        val settings = UISettings.from(this)
         // Apply the theme configuration.
-        AppCompatDelegate.setDefaultNightMode(settings.theme)
+        AppCompatDelegate.setDefaultNightMode(uiSettings.theme)
         // Apply the color scheme. The black theme requires it's own set of themes since
         // it's not possible to modify the themes at run-time.
-        if (isNight && settings.useBlackTheme) {
+        if (isNight && uiSettings.useBlackTheme) {
-            logD("Applying black theme [accent ${settings.accent}]")
+            logD("Applying black theme [accent ${uiSettings.accent}]")
-            setTheme(settings.accent.blackTheme)
+            setTheme(uiSettings.accent.blackTheme)
         } else {
-            logD("Applying normal theme [accent ${settings.accent}]")
+            logD("Applying normal theme [accent ${uiSettings.accent}]")
-            setTheme(settings.accent.theme)
+            setTheme(uiSettings.accent.theme)
         }
     }
 

app/src/main/java/org/oxycblt/auxio/MainFragment.kt

@@ -33,6 +33,7 @@ import androidx.navigation.fragment.findNavController
 import com.google.android.material.bottomsheet.BackportBottomSheetBehavior
 import com.google.android.material.shape.MaterialShapeDrawable
 import com.google.android.material.transition.MaterialFadeThrough
+import dagger.hilt.android.AndroidEntryPoint
 import kotlin.math.max
 import kotlin.math.min
 import org.oxycblt.auxio.databinding.FragmentMainBinding
@@ -52,11 +53,12 @@ import org.oxycblt.auxio.util.*
  * high-level navigation features.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class MainFragment :
     ViewBindingFragment<FragmentMainBinding>(),
     ViewTreeObserver.OnPreDrawListener,
     NavController.OnDestinationChangedListener {
-    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val playbackModel: PlaybackViewModel by activityViewModels()
     private val navModel: NavigationViewModel by activityViewModels()
     private val selectionModel: SelectionViewModel by activityViewModels()
     private val callback = DynamicBackPressedCallback()

app/src/main/java/org/oxycblt/auxio/detail/AlbumDetailFragment.kt

@@ -26,28 +26,36 @@ import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.LinearSmoothScroller
 import com.google.android.material.transition.MaterialSharedAxis
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentDetailBinding
 import org.oxycblt.auxio.detail.recycler.AlbumDetailAdapter
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.playback.PlaybackViewModel
+import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.*
 
 /**
  * A [ListFragment] that shows information about an [Album].
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class AlbumDetailFragment :
     ListFragment<Song, FragmentDetailBinding>(), AlbumDetailAdapter.Listener {
     private val detailModel: DetailViewModel by activityViewModels()
+    override val navModel: NavigationViewModel by activityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
     // Information about what album to display is initially within the navigation arguments
     // as a UID, as that is the only safe way to parcel an album.
     private val args: AlbumDetailFragmentArgs by navArgs()
@@ -143,14 +151,19 @@ class AlbumDetailFragment :
         openMenu(anchor, R.menu.menu_album_sort) {
             val sort = detailModel.albumSongSort
             unlikelyToBeNull(menu.findItem(sort.mode.itemId)).isChecked = true
-            unlikelyToBeNull(menu.findItem(R.id.option_sort_asc)).isChecked = sort.isAscending
+            val directionItemId =
+                when (sort.direction) {
+                    Sort.Direction.ASCENDING -> R.id.option_sort_asc
+                    Sort.Direction.DESCENDING -> R.id.option_sort_dec
+                }
+            unlikelyToBeNull(menu.findItem(directionItemId)).isChecked = true
             setOnMenuItemClickListener { item ->
                 item.isChecked = !item.isChecked
                 detailModel.albumSongSort =
-                    if (item.itemId == R.id.option_sort_asc) {
+                    when (item.itemId) {
-                        sort.withAscending(item.isChecked)
+                        R.id.option_sort_asc -> sort.withDirection(Sort.Direction.ASCENDING)
-                    } else {
+                        R.id.option_sort_dec -> sort.withDirection(Sort.Direction.DESCENDING)
-                        sort.withMode(unlikelyToBeNull(Sort.Mode.fromItemId(item.itemId)))
+                        else -> sort.withMode(unlikelyToBeNull(Sort.Mode.fromItemId(item.itemId)))
                     }
                 true
             }

app/src/main/java/org/oxycblt/auxio/detail/ArtistDetailFragment.kt

@@ -25,19 +25,23 @@ import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import com.google.android.material.transition.MaterialSharedAxis
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentDetailBinding
 import org.oxycblt.auxio.detail.recycler.ArtistDetailAdapter
 import org.oxycblt.auxio.detail.recycler.DetailAdapter
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.playback.PlaybackViewModel
+import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.collect
 import org.oxycblt.auxio.util.collectImmediately
 import org.oxycblt.auxio.util.logD
@@ -48,9 +52,13 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * A [ListFragment] that shows information about an [Artist].
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class ArtistDetailFragment :
     ListFragment<Music, FragmentDetailBinding>(), DetailAdapter.Listener<Music> {
     private val detailModel: DetailViewModel by activityViewModels()
+    override val navModel: NavigationViewModel by activityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
     // Information about what artist to display is initially within the navigation arguments
     // as a UID, as that is the only safe way to parcel an artist.
     private val args: ArtistDetailFragmentArgs by navArgs()
@@ -159,15 +167,20 @@ class ArtistDetailFragment :
         openMenu(anchor, R.menu.menu_artist_sort) {
             val sort = detailModel.artistSongSort
             unlikelyToBeNull(menu.findItem(sort.mode.itemId)).isChecked = true
-            unlikelyToBeNull(menu.findItem(R.id.option_sort_asc)).isChecked = sort.isAscending
+            val directionItemId =
+                when (sort.direction) {
+                    Sort.Direction.ASCENDING -> R.id.option_sort_asc
+                    Sort.Direction.DESCENDING -> R.id.option_sort_dec
+                }
+            unlikelyToBeNull(menu.findItem(directionItemId)).isChecked = true
             setOnMenuItemClickListener { item ->
                 item.isChecked = !item.isChecked
 
                 detailModel.artistSongSort =
-                    if (item.itemId == R.id.option_sort_asc) {
+                    when (item.itemId) {
-                        sort.withAscending(item.isChecked)
+                        R.id.option_sort_asc -> sort.withDirection(Sort.Direction.ASCENDING)
-                    } else {
+                        R.id.option_sort_dec -> sort.withDirection(Sort.Direction.DESCENDING)
-                        sort.withMode(unlikelyToBeNull(Sort.Mode.fromItemId(item.itemId)))
+                        else -> sort.withMode(unlikelyToBeNull(Sort.Mode.fromItemId(item.itemId)))
                     }
 
                 true

app/src/main/java/org/oxycblt/auxio/detail/Detail.kt

@@ -1,50 +0,0 @@
-/*
- * Copyright (c) 2022 Auxio Project
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
- 
-package org.oxycblt.auxio.detail
-
-import androidx.annotation.StringRes
-import org.oxycblt.auxio.list.Item
-import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.storage.MimeType
-
-/**
- * A header variation that displays a button to open a sort menu.
- * @param titleRes The string resource to use as the header title
- * @author Alexander Capehart (OxygenCobalt)
- */
-data class SortHeader(@StringRes val titleRes: Int) : Item
-
-/**
- * A header variation that delimits between disc groups.
- * @param disc The disc number to be displayed on the header.
- * @author Alexander Capehart (OxygenCobalt)
- */
-data class DiscHeader(val disc: Int) : Item
-
-/**
- * The properties of a [Song]'s file.
- * @param bitrateKbps The bit rate, in kilobytes-per-second. Null if it could not be parsed.
- * @param sampleRateHz The sample rate, in hertz.
- * @param resolvedMimeType The known mime type of the [Song] after it's file format was determined.
- * @author Alexander Capehart (OxygenCobalt)
- */
-data class SongProperties(
-    val bitrateKbps: Int?,
-    val sampleRateHz: Int?,
-    val resolvedMimeType: MimeType
-)

app/src/main/java/org/oxycblt/auxio/detail/DetailViewModel.kt

@@ -17,12 +17,11 @@
  
 package org.oxycblt.auxio.detail
 
-import android.app.Application
-import android.media.MediaExtractor
-import android.media.MediaFormat
 import androidx.annotation.StringRes
-import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -30,30 +29,32 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.yield
 import org.oxycblt.auxio.R
-import org.oxycblt.auxio.list.Header
+import org.oxycblt.auxio.detail.recycler.SortHeader
+import org.oxycblt.auxio.list.BasicHeader
 import org.oxycblt.auxio.list.Item
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.MusicStore
+import org.oxycblt.auxio.music.metadata.AudioInfo
-import org.oxycblt.auxio.music.library.Library
+import org.oxycblt.auxio.music.metadata.Disc
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.music.metadata.ReleaseType
-import org.oxycblt.auxio.music.storage.MimeType
+import org.oxycblt.auxio.music.model.Library
-import org.oxycblt.auxio.music.tags.ReleaseType
 import org.oxycblt.auxio.playback.PlaybackSettings
 import org.oxycblt.auxio.util.*
 
 /**
- * [AndroidViewModel] that manages the Song, Album, Artist, and Genre detail views. Keeps track of
+ * [ViewModel] that manages the Song, Album, Artist, and Genre detail views. Keeps track of the
- * the current item they are showing, sub-data to display, and configuration. Since this ViewModel
+ * current item they are showing, sub-data to display, and configuration.
- * requires a context, it must be instantiated [AndroidViewModel]'s Factory.
- * @param application [Application] context required to initialize certain information.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class DetailViewModel(application: Application) :
+@HiltViewModel
-    AndroidViewModel(application), MusicStore.Listener {
+class DetailViewModel
-    private val musicStore = MusicStore.getInstance()
+@Inject
-    private val musicSettings = MusicSettings.from(application)
+constructor(
-    private val playbackSettings = PlaybackSettings.from(application)
+    private val musicRepository: MusicRepository,
-
+    private val audioInfoProvider: AudioInfo.Provider,
+    private val musicSettings: MusicSettings,
+    private val playbackSettings: PlaybackSettings
+) : ViewModel(), MusicRepository.Listener {
     private var currentSongJob: Job? = null
 
     // --- SONG ---
@@ -63,9 +64,9 @@ class DetailViewModel(application: Application) :
     val currentSong: StateFlow<Song?>
         get() = _currentSong
 
-    private val _songProperties = MutableStateFlow<SongProperties?>(null)
+    private val _songAudioInfo = MutableStateFlow<AudioInfo?>(null)
-    /** The [SongProperties] of the currently shown [Song]. Null if not loaded yet. */
+    /** The [AudioInfo] of the currently shown [Song]. Null if not loaded yet. */
-    val songProperties: StateFlow<SongProperties?> = _songProperties
+    val songAudioInfo: StateFlow<AudioInfo?> = _songAudioInfo
 
     // --- ALBUM ---
 
@@ -136,11 +137,11 @@ class DetailViewModel(application: Application) :
         get() = playbackSettings.inParentPlaybackMode
 
     init {
-        musicStore.addListener(this)
+        musicRepository.addListener(this)
     }
 
     override fun onCleared() {
-        musicStore.removeListener(this)
+        musicRepository.removeListener(this)
     }
 
     override fun onLibraryChanged(library: Library?) {
@@ -155,7 +156,7 @@ class DetailViewModel(application: Application) :
 
         val song = currentSong.value
         if (song != null) {
-            _currentSong.value = library.sanitize(song)?.also(::loadProperties)
+            _currentSong.value = library.sanitize(song)?.also(::refreshAudioInfo)
             logD("Updated song to ${currentSong.value}")
         }
 
@@ -180,7 +181,7 @@ class DetailViewModel(application: Application) :
 
     /**
      * Set a new [currentSong] from it's [Music.UID]. If the [Music.UID] differs, [currentSong] and
-     * [songProperties] will be updated to align with the new [Song].
+     * [songAudioInfo] will be updated to align with the new [Song].
      * @param uid The UID of the [Song] to load. Must be valid.
      */
     fun setSongUid(uid: Music.UID) {
@@ -189,7 +190,7 @@ class DetailViewModel(application: Application) :
             return
         }
         logD("Opening Song [uid: $uid]")
-        _currentSong.value = requireMusic<Song>(uid)?.also(::loadProperties)
+        _currentSong.value = requireMusic<Song>(uid)?.also(::refreshAudioInfo)
     }
 
     /**
@@ -234,86 +235,24 @@ class DetailViewModel(application: Application) :
         _currentGenre.value = requireMusic<Genre>(uid)?.also(::refreshGenreList)
     }
 
-    private fun <T : Music> requireMusic(uid: Music.UID) = musicStore.library?.find<T>(uid)
+    private fun <T : Music> requireMusic(uid: Music.UID) = musicRepository.library?.find<T>(uid)
 
     /**
-     * Start a new job to load a given [Song]'s [SongProperties]. Result is pushed to
+     * Start a new job to load a given [Song]'s [AudioInfo]. Result is pushed to [songAudioInfo].
-     * [songProperties].
      * @param song The song to load.
      */
-    private fun loadProperties(song: Song) {
+    private fun refreshAudioInfo(song: Song) {
         // Clear any previous job in order to avoid stale data from appearing in the UI.
         currentSongJob?.cancel()
-        _songProperties.value = null
+        _songAudioInfo.value = null
         currentSongJob =
             viewModelScope.launch(Dispatchers.IO) {
-                val properties = this@DetailViewModel.loadPropertiesImpl(song)
+                val info = audioInfoProvider.extract(song)
                 yield()
-                _songProperties.value = properties
+                _songAudioInfo.value = info
             }
     }
 
-    private fun loadPropertiesImpl(song: Song): SongProperties {
-        // While we would use ExoPlayer to extract this information, it doesn't support
-        // common data like bit rate in progressive data sources due to there being no
-        // demand. Thus, we are stuck with the inferior OS-provided MediaExtractor.
-        val extractor = MediaExtractor()
-
-        try {
-            extractor.setDataSource(context, song.uri, emptyMap())
-        } catch (e: Exception) {
-            // Can feasibly fail with invalid file formats. Note that this isn't considered
-            // an error condition in the UI, as there is still plenty of other song information
-            // that we can show.
-            logW("Unable to extract song attributes.")
-            logW(e.stackTraceToString())
-            return SongProperties(null, null, song.mimeType)
-        }
-
-        // Get the first track from the extractor (This is basically always the only
-        // track we need to analyze).
-        val format = extractor.getTrackFormat(0)
-
-        // Accessing fields can throw an exception if the fields are not present, and
-        // the new method for using default values is not available on lower API levels.
-        // So, we are forced to handle the exception and map it to a saner null value.
-        val bitrate =
-            try {
-                // Convert bytes-per-second to kilobytes-per-second.
-                format.getInteger(MediaFormat.KEY_BIT_RATE) / 1000
-            } catch (e: NullPointerException) {
-                logD("Unable to extract bit rate field")
-                null
-            }
-
-        val sampleRate =
-            try {
-                format.getInteger(MediaFormat.KEY_SAMPLE_RATE)
-            } catch (e: NullPointerException) {
-                logE("Unable to extract sample rate field")
-                null
-            }
-
-        val resolvedMimeType =
-            if (song.mimeType.fromFormat != null) {
-                // ExoPlayer was already able to populate the format.
-                song.mimeType
-            } else {
-                // ExoPlayer couldn't populate the format somehow, populate it here.
-                val formatMimeType =
-                    try {
-                        format.getString(MediaFormat.KEY_MIME)
-                    } catch (e: NullPointerException) {
-                        logE("Unable to extract mime type field")
-                        null
-                    }
-
-                MimeType(song.mimeType.fromExtension, formatMimeType)
-            }
-
-        return SongProperties(bitrate, sampleRate, resolvedMimeType)
-    }
-
     private fun refreshAlbumList(album: Album) {
         logD("Refreshing album data")
         val data = mutableListOf<Item>(album)
@@ -323,11 +262,11 @@ class DetailViewModel(application: Application) :
         // songs up by disc and then delimit the groups by a disc header.
         val songs = albumSongSort.songs(album.songs)
         // Songs without disc tags become part of Disc 1.
-        val byDisc = songs.groupBy { it.disc ?: 1 }
+        val byDisc = songs.groupBy { it.disc ?: Disc(1, null) }
         if (byDisc.size > 1) {
             logD("Album has more than one disc, interspersing headers")
             for (entry in byDisc.entries) {
-                data.add(DiscHeader(entry.key))
+                data.add(entry.key)
                 data.addAll(entry.value)
             }
         } else {
@@ -341,7 +280,7 @@ class DetailViewModel(application: Application) :
     private fun refreshArtistList(artist: Artist) {
         logD("Refreshing artist data")
         val data = mutableListOf<Item>(artist)
-        val albums = Sort(Sort.Mode.ByDate, false).albums(artist.albums)
+        val albums = Sort(Sort.Mode.ByDate, Sort.Direction.DESCENDING).albums(artist.albums)
 
         val byReleaseGroup =
             albums.groupBy {
@@ -367,7 +306,7 @@ class DetailViewModel(application: Application) :
         logD("Release groups for this artist: ${byReleaseGroup.keys}")
 
         for (entry in byReleaseGroup.entries.sortedBy { it.key }) {
-            data.add(Header(entry.key.headerTitleRes))
+            data.add(BasicHeader(entry.key.headerTitleRes))
             data.addAll(entry.value)
         }
 
@@ -385,7 +324,7 @@ class DetailViewModel(application: Application) :
         logD("Refreshing genre data")
         val data = mutableListOf<Item>(genre)
         // Genre is guaranteed to always have artists and songs.
-        data.add(Header(R.string.lbl_artists))
+        data.add(BasicHeader(R.string.lbl_artists))
         data.addAll(genre.artists)
         data.add(SortHeader(R.string.lbl_songs))
         data.addAll(genreSongSort.songs(genre.songs))

app/src/main/java/org/oxycblt/auxio/detail/GenreDetailFragment.kt

@@ -25,20 +25,24 @@ import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import com.google.android.material.transition.MaterialSharedAxis
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentDetailBinding
 import org.oxycblt.auxio.detail.recycler.DetailAdapter
 import org.oxycblt.auxio.detail.recycler.GenreDetailAdapter
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.ListFragment
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Genre
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.playback.PlaybackViewModel
+import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.collect
 import org.oxycblt.auxio.util.collectImmediately
 import org.oxycblt.auxio.util.logD
@@ -49,9 +53,13 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * A [ListFragment] that shows information for a particular [Genre].
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class GenreDetailFragment :
     ListFragment<Music, FragmentDetailBinding>(), DetailAdapter.Listener<Music> {
     private val detailModel: DetailViewModel by activityViewModels()
+    override val navModel: NavigationViewModel by activityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
     // Information about what genre to display is initially within the navigation arguments
     // as a UID, as that is the only safe way to parcel an genre.
     private val args: GenreDetailFragmentArgs by navArgs()
@@ -158,14 +166,19 @@ class GenreDetailFragment :
         openMenu(anchor, R.menu.menu_genre_sort) {
             val sort = detailModel.genreSongSort
             unlikelyToBeNull(menu.findItem(sort.mode.itemId)).isChecked = true
-            unlikelyToBeNull(menu.findItem(R.id.option_sort_asc)).isChecked = sort.isAscending
+            val directionItemId =
+                when (sort.direction) {
+                    Sort.Direction.ASCENDING -> R.id.option_sort_asc
+                    Sort.Direction.DESCENDING -> R.id.option_sort_dec
+                }
+            unlikelyToBeNull(menu.findItem(directionItemId)).isChecked = true
             setOnMenuItemClickListener { item ->
                 item.isChecked = !item.isChecked
                 detailModel.genreSongSort =
-                    if (item.itemId == R.id.option_sort_asc) {
+                    when (item.itemId) {
-                        sort.withAscending(item.isChecked)
+                        R.id.option_sort_asc -> sort.withDirection(Sort.Direction.ASCENDING)
-                    } else {
+                        R.id.option_sort_dec -> sort.withDirection(Sort.Direction.DESCENDING)
-                        sort.withMode(unlikelyToBeNull(Sort.Mode.fromItemId(item.itemId)))
+                        else -> sort.withMode(unlikelyToBeNull(Sort.Mode.fromItemId(item.itemId)))
                     }
                 true
             }

app/src/main/java/org/oxycblt/auxio/detail/SongDetailDialog.kt

@@ -17,30 +17,40 @@
  
 package org.oxycblt.auxio.detail
 
+import android.content.Context
 import android.os.Bundle
 import android.text.format.Formatter
 import android.view.LayoutInflater
 import androidx.appcompat.app.AlertDialog
-import androidx.core.view.isInvisible
+import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogSongDetailBinding
+import org.oxycblt.auxio.detail.recycler.SongProperty
+import org.oxycblt.auxio.detail.recycler.SongPropertyAdapter
+import org.oxycblt.auxio.list.adapter.BasicListInstructions
+import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.metadata.AudioInfo
+import org.oxycblt.auxio.music.resolveNames
 import org.oxycblt.auxio.playback.formatDurationMs
 import org.oxycblt.auxio.ui.ViewBindingDialogFragment
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.collectImmediately
+import org.oxycblt.auxio.util.concatLocalized
 
 /**
  * A [ViewBindingDialogFragment] that shows information about a Song.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class SongDetailDialog : ViewBindingDialogFragment<DialogSongDetailBinding>() {
-    private val detailModel: DetailViewModel by androidActivityViewModels()
+    private val detailModel: DetailViewModel by activityViewModels()
     // Information about what song to display is initially within the navigation arguments
     // as a UID, as that is the only safe way to parcel an song.
     private val args: SongDetailDialogArgs by navArgs()
+    private val detailAdapter = SongPropertyAdapter()
 
     override fun onCreateBinding(inflater: LayoutInflater) =
         DialogSongDetailBinding.inflate(inflater)
@@ -52,48 +62,72 @@ class SongDetailDialog : ViewBindingDialogFragment<DialogSongDetailBinding>() {
 
     override fun onBindingCreated(binding: DialogSongDetailBinding, savedInstanceState: Bundle?) {
         super.onBindingCreated(binding, savedInstanceState)
+        binding.detailProperties.adapter = detailAdapter
         // DetailViewModel handles most initialization from the navigation argument.
         detailModel.setSongUid(args.itemUid)
-        collectImmediately(detailModel.currentSong, detailModel.songProperties, ::updateSong)
+        collectImmediately(detailModel.currentSong, detailModel.songAudioInfo, ::updateSong)
     }
 
-    private fun updateSong(song: Song?, properties: SongProperties?) {
+    private fun updateSong(song: Song?, info: AudioInfo?) {
         if (song == null) {
             // Song we were showing no longer exists.
             findNavController().navigateUp()
             return
         }
 
-        val binding = requireBinding()
+        if (info != null) {
-        if (properties != null) {
-            // Finished loading Song properties, populate and show the list of Song information.
-            binding.detailLoading.isInvisible = true
-            binding.detailContainer.isInvisible = false
-
             val context = requireContext()
-            binding.detailFileName.setText(song.path.name)
+            detailAdapter.submitList(
-            binding.detailRelativeDir.setText(song.path.parent.resolveName(context))
+                buildList {
-            binding.detailFormat.setText(properties.resolvedMimeType.resolveName(context))
+                    add(SongProperty(R.string.lbl_name, song.zipName(context)))
-            binding.detailSize.setText(Formatter.formatFileSize(context, song.size))
+                    add(SongProperty(R.string.lbl_album, song.album.zipName(context)))
-            binding.detailDuration.setText(song.durationMs.formatDurationMs(true))
+                    add(SongProperty(R.string.lbl_artists, song.artists.zipNames(context)))
-
+                    add(SongProperty(R.string.lbl_genres, song.genres.resolveNames(context)))
-            if (properties.bitrateKbps != null) {
+                    song.date?.let { add(SongProperty(R.string.lbl_date, it.resolveDate(context))) }
-                binding.detailBitrate.setText(
+                    song.track?.let {
-                    getString(R.string.fmt_bitrate, properties.bitrateKbps))
+                        add(SongProperty(R.string.lbl_track, getString(R.string.fmt_number, it)))
-            } else {
+                    }
-                binding.detailBitrate.setText(R.string.def_bitrate)
+                    song.disc?.let {
-            }
+                        val formattedNumber = getString(R.string.fmt_number, it.number)
-
+                        val zipped =
-            if (properties.sampleRateHz != null) {
+                            if (it.name != null) {
-                binding.detailSampleRate.setText(
+                                getString(R.string.fmt_zipped_names, formattedNumber, it.name)
-                    getString(R.string.fmt_sample_rate, properties.sampleRateHz))
+                            } else {
-            } else {
+                                formattedNumber
-                binding.detailSampleRate.setText(R.string.def_sample_rate)
+                            }
-            }
+                        add(SongProperty(R.string.lbl_disc, zipped))
-        } else {
+                    }
-            // Loading is still on-going, don't show anything yet.
+                    add(SongProperty(R.string.lbl_file_name, song.path.name))
-            binding.detailLoading.isInvisible = false
+                    add(
-            binding.detailContainer.isInvisible = true
+                        SongProperty(
+                            R.string.lbl_relative_path, song.path.parent.resolveName(context)))
+                    info.resolvedMimeType.resolveName(context)?.let {
+                        SongProperty(R.string.lbl_format, it)
+                    }
+                    add(
+                        SongProperty(
+                            R.string.lbl_size, Formatter.formatFileSize(context, song.size)))
+                    add(SongProperty(R.string.lbl_duration, song.durationMs.formatDurationMs(true)))
+                    info.bitrateKbps?.let {
+                        add(SongProperty(R.string.lbl_bitrate, getString(R.string.fmt_bitrate, it)))
+                    }
+                    info.sampleRateHz?.let {
+                        add(
+                            SongProperty(
+                                R.string.lbl_sample_rate, getString(R.string.fmt_sample_rate, it)))
+                    }
+                },
+                BasicListInstructions.REPLACE)
         }
     }
+
+    private fun <T : Music> T.zipName(context: Context) =
+        if (rawSortName != null) {
+            getString(R.string.fmt_zipped_names, resolveName(context), rawSortName)
+        } else {
+            resolveName(context)
+        }
+
+    private fun <T : Music> List<T>.zipNames(context: Context) =
+        concatLocalized(context) { it.zipName(context) }
 }

app/src/main/java/org/oxycblt/auxio/detail/recycler/AlbumDetailAdapter.kt

@@ -19,6 +19,7 @@ package org.oxycblt.auxio.detail.recycler
 
 import android.view.View
 import android.view.ViewGroup
+import androidx.core.view.isGone
 import androidx.core.view.isInvisible
 import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.IntegerTable
@@ -26,13 +27,15 @@ import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.ItemAlbumSongBinding
 import org.oxycblt.auxio.databinding.ItemDetailBinding
 import org.oxycblt.auxio.databinding.ItemDiscHeaderBinding
-import org.oxycblt.auxio.detail.DiscHeader
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
 import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.areRawNamesTheSame
+import org.oxycblt.auxio.music.metadata.Disc
+import org.oxycblt.auxio.music.resolveNames
 import org.oxycblt.auxio.playback.formatDurationMs
 import org.oxycblt.auxio.util.context
 import org.oxycblt.auxio.util.getPlural
@@ -60,7 +63,7 @@ class AlbumDetailAdapter(private val listener: Listener) : DetailAdapter(listene
         when (getItem(position)) {
             // Support the Album header, sub-headers for each disc, and special album songs.
             is Album -> AlbumDetailViewHolder.VIEW_TYPE
-            is DiscHeader -> DiscHeaderViewHolder.VIEW_TYPE
+            is Disc -> DiscViewHolder.VIEW_TYPE
             is Song -> AlbumSongViewHolder.VIEW_TYPE
             else -> super.getItemViewType(position)
         }
@@ -68,7 +71,7 @@ class AlbumDetailAdapter(private val listener: Listener) : DetailAdapter(listene
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
         when (viewType) {
             AlbumDetailViewHolder.VIEW_TYPE -> AlbumDetailViewHolder.from(parent)
-            DiscHeaderViewHolder.VIEW_TYPE -> DiscHeaderViewHolder.from(parent)
+            DiscViewHolder.VIEW_TYPE -> DiscViewHolder.from(parent)
             AlbumSongViewHolder.VIEW_TYPE -> AlbumSongViewHolder.from(parent)
             else -> super.onCreateViewHolder(parent, viewType)
         }
@@ -77,7 +80,7 @@ class AlbumDetailAdapter(private val listener: Listener) : DetailAdapter(listene
         super.onBindViewHolder(holder, position)
         when (val item = getItem(position)) {
             is Album -> (holder as AlbumDetailViewHolder).bind(item, listener)
-            is DiscHeader -> (holder as DiscHeaderViewHolder).bind(item)
+            is Disc -> (holder as DiscViewHolder).bind(item)
             is Song -> (holder as AlbumSongViewHolder).bind(item, listener)
         }
     }
@@ -88,7 +91,7 @@ class AlbumDetailAdapter(private val listener: Listener) : DetailAdapter(listene
         }
         // The album and disc headers should be full-width in all configurations.
         val item = getItem(position)
-        return item is Album || item is DiscHeader
+        return item is Album || item is Disc
     }
 
     private companion object {
@@ -99,8 +102,8 @@ class AlbumDetailAdapter(private val listener: Listener) : DetailAdapter(listene
                     return when {
                         oldItem is Album && newItem is Album ->
                             AlbumDetailViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
-                        oldItem is DiscHeader && newItem is DiscHeader ->
+                        oldItem is Disc && newItem is Disc ->
-                            DiscHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
+                            DiscViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is Song && newItem is Song ->
                             AlbumSongViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
 
@@ -135,7 +138,7 @@ private class AlbumDetailViewHolder private constructor(private val binding: Ite
 
         // Artist name maps to the subhead text
         binding.detailSubhead.apply {
-            text = album.resolveArtistContents(context)
+            text = album.artists.resolveNames(context)
 
             // Add a QoL behavior where navigation to the artist will occur if the artist
             // name is pressed.
@@ -172,7 +175,7 @@ private class AlbumDetailViewHolder private constructor(private val binding: Ite
             object : SimpleDiffCallback<Album>() {
                 override fun areContentsTheSame(oldItem: Album, newItem: Album) =
                     oldItem.rawName == newItem.rawName &&
-                        oldItem.areArtistContentsTheSame(newItem) &&
+                        oldItem.artists.areRawNamesTheSame(newItem.artists) &&
                         oldItem.dates == newItem.dates &&
                         oldItem.songs.size == newItem.songs.size &&
                         oldItem.durationMs == newItem.durationMs &&
@@ -182,18 +185,22 @@ private class AlbumDetailViewHolder private constructor(private val binding: Ite
 }
 
 /**
- * A [RecyclerView.ViewHolder] that displays a [DiscHeader] to delimit different disc groups. Use
+ * A [RecyclerView.ViewHolder] that displays a [Disc] to delimit different disc groups. Use [from]
- * [from] to create an instance.
+ * to create an instance.
  * @author Alexander Capehart (OxygenCobalt)
  */
-private class DiscHeaderViewHolder(private val binding: ItemDiscHeaderBinding) :
+private class DiscViewHolder(private val binding: ItemDiscHeaderBinding) :
     RecyclerView.ViewHolder(binding.root) {
     /**
      * Bind new data to this instance.
-     * @param discHeader The new [DiscHeader] to bind.
+     * @param disc The new [disc] to bind.
      */
-    fun bind(discHeader: DiscHeader) {
+    fun bind(disc: Disc) {
-        binding.discNo.text = binding.context.getString(R.string.fmt_disc_no, discHeader.disc)
+        binding.discNumber.text = binding.context.getString(R.string.fmt_disc_no, disc.number)
+        binding.discName.apply {
+            text = disc.name
+            isGone = disc.name == null
+        }
     }
 
     companion object {
@@ -206,13 +213,13 @@ private class DiscHeaderViewHolder(private val binding: ItemDiscHeaderBinding) :
          * @return A new instance.
          */
         fun from(parent: View) =
-            DiscHeaderViewHolder(ItemDiscHeaderBinding.inflate(parent.context.inflater))
+            DiscViewHolder(ItemDiscHeaderBinding.inflate(parent.context.inflater))
 
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =
-            object : SimpleDiffCallback<DiscHeader>() {
+            object : SimpleDiffCallback<Disc>() {
-                override fun areContentsTheSame(oldItem: DiscHeader, newItem: DiscHeader) =
+                override fun areContentsTheSame(oldItem: Disc, newItem: Disc) =
-                    oldItem.disc == newItem.disc
+                    oldItem.number == newItem.number && oldItem.name == newItem.name
             }
     }
 }

app/src/main/java/org/oxycblt/auxio/detail/recycler/ArtistDetailAdapter.kt

@@ -30,10 +30,7 @@ import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
-import org.oxycblt.auxio.music.Album
+import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.Artist
-import org.oxycblt.auxio.music.Music
-import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.util.context
 import org.oxycblt.auxio.util.getPlural
 import org.oxycblt.auxio.util.inflater
@@ -122,7 +119,7 @@ private class ArtistDetailViewHolder private constructor(private val binding: It
             // Information about the artist's genre(s) map to the sub-head text
             binding.detailSubhead.apply {
                 isVisible = true
-                text = artist.resolveGenreContents(binding.context)
+                text = artist.genres.resolveNames(context)
             }
 
             // Song and album counts map to the info
@@ -168,7 +165,7 @@ private class ArtistDetailViewHolder private constructor(private val binding: It
             object : SimpleDiffCallback<Artist>() {
                 override fun areContentsTheSame(oldItem: Artist, newItem: Artist) =
                     oldItem.rawName == newItem.rawName &&
-                        oldItem.areGenreContentsTheSame(newItem) &&
+                        oldItem.genres.areRawNamesTheSame(newItem.genres) &&
                         oldItem.albums.size == newItem.albums.size &&
                         oldItem.songs.size == newItem.songs.size
             }

app/src/main/java/org/oxycblt/auxio/detail/recycler/DetailAdapter.kt

@@ -19,12 +19,13 @@ package org.oxycblt.auxio.detail.recycler
 
 import android.view.View
 import android.view.ViewGroup
+import androidx.annotation.StringRes
 import androidx.appcompat.widget.TooltipCompat
 import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.RecyclerView
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.databinding.ItemSortHeaderBinding
-import org.oxycblt.auxio.detail.SortHeader
+import org.oxycblt.auxio.list.BasicHeader
 import org.oxycblt.auxio.list.Header
 import org.oxycblt.auxio.list.Item
 import org.oxycblt.auxio.list.SelectableListListener
@@ -52,21 +53,21 @@ abstract class DetailAdapter(
     override fun getItemViewType(position: Int) =
         when (getItem(position)) {
             // Implement support for headers and sort headers
-            is Header -> HeaderViewHolder.VIEW_TYPE
+            is BasicHeader -> BasicHeaderViewHolder.VIEW_TYPE
             is SortHeader -> SortHeaderViewHolder.VIEW_TYPE
             else -> super.getItemViewType(position)
         }
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
         when (viewType) {
-            HeaderViewHolder.VIEW_TYPE -> HeaderViewHolder.from(parent)
+            BasicHeaderViewHolder.VIEW_TYPE -> BasicHeaderViewHolder.from(parent)
             SortHeaderViewHolder.VIEW_TYPE -> SortHeaderViewHolder.from(parent)
             else -> error("Invalid item type $viewType")
         }
 
     override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
         when (val item = getItem(position)) {
-            is Header -> (holder as HeaderViewHolder).bind(item)
+            is BasicHeader -> (holder as BasicHeaderViewHolder).bind(item)
             is SortHeader -> (holder as SortHeaderViewHolder).bind(item, listener)
         }
     }
@@ -74,7 +75,7 @@ abstract class DetailAdapter(
     override fun isItemFullWidth(position: Int): Boolean {
         // Headers should be full-width in all configurations.
         val item = getItem(position)
-        return item is Header || item is SortHeader
+        return item is BasicHeader || item is SortHeader
     }
 
     /** An extended [SelectableListListener] for [DetailAdapter] implementations. */
@@ -105,8 +106,8 @@ abstract class DetailAdapter(
             object : SimpleDiffCallback<Item>() {
                 override fun areContentsTheSame(oldItem: Item, newItem: Item): Boolean {
                     return when {
-                        oldItem is Header && newItem is Header ->
+                        oldItem is BasicHeader && newItem is BasicHeader ->
-                            HeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
+                            BasicHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         oldItem is SortHeader && newItem is SortHeader ->
                             SortHeaderViewHolder.DIFF_CALLBACK.areContentsTheSame(oldItem, newItem)
                         else -> false
@@ -117,8 +118,15 @@ abstract class DetailAdapter(
 }
 
 /**
- * A [RecyclerView.ViewHolder] that displays a [SortHeader], a variation on [Header] that adds a
+ * A header variation that displays a button to open a sort menu.
- * button opening a menu for sorting. Use [from] to create an instance.
+ * @param titleRes The string resource to use as the header title
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+data class SortHeader(@StringRes override val titleRes: Int) : Header
+
+/**
+ * A [RecyclerView.ViewHolder] that displays a [SortHeader], a variation on [BasicHeader] that adds
+ * a button opening a menu for sorting. Use [from] to create an instance.
  * @author Alexander Capehart (OxygenCobalt)
  */
 private class SortHeaderViewHolder(private val binding: ItemSortHeaderBinding) :

app/src/main/java/org/oxycblt/auxio/detail/recycler/SongPropertyAdapter.kt

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.detail.recycler
+
+import android.view.View
+import android.view.ViewGroup
+import androidx.annotation.StringRes
+import androidx.recyclerview.widget.RecyclerView
+import org.oxycblt.auxio.databinding.ItemSongPropertyBinding
+import org.oxycblt.auxio.list.Item
+import org.oxycblt.auxio.list.adapter.BasicListInstructions
+import org.oxycblt.auxio.list.adapter.DiffAdapter
+import org.oxycblt.auxio.list.adapter.ListDiffer
+import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
+import org.oxycblt.auxio.list.recycler.DialogRecyclerView
+import org.oxycblt.auxio.util.context
+import org.oxycblt.auxio.util.inflater
+
+/**
+ * An adapter for [SongProperty] instances.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class SongPropertyAdapter :
+    DiffAdapter<SongProperty, BasicListInstructions, SongPropertyViewHolder>(
+        ListDiffer.Blocking(SongPropertyViewHolder.DIFF_CALLBACK)) {
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
+        SongPropertyViewHolder.from(parent)
+
+    override fun onBindViewHolder(holder: SongPropertyViewHolder, position: Int) {
+        holder.bind(getItem(position))
+    }
+}
+
+/**
+ * A property entry for use in [SongPropertyAdapter].
+ * @param name The contextual title to use for the property.
+ * @param value The value of the property.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+data class SongProperty(@StringRes val name: Int, val value: String) : Item
+
+/**
+ * A [RecyclerView.ViewHolder] that displays a [SongProperty]. Use [from] to create an instance.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class SongPropertyViewHolder private constructor(private val binding: ItemSongPropertyBinding) :
+    DialogRecyclerView.ViewHolder(binding.root) {
+    fun bind(property: SongProperty) {
+        val context = binding.context
+        binding.propertyName.hint = context.getString(property.name)
+        binding.propertyValue.setText(property.value)
+    }
+
+    companion object {
+        /**
+         * Create a new instance.
+         * @param parent The parent to inflate this instance from.
+         * @return A new instance.
+         */
+        fun from(parent: View) =
+            SongPropertyViewHolder(ItemSongPropertyBinding.inflate(parent.context.inflater))
+
+        /** A comparator that can be used with DiffUtil. */
+        val DIFF_CALLBACK =
+            object : SimpleDiffCallback<SongProperty>() {
+                override fun areContentsTheSame(oldItem: SongProperty, newItem: SongProperty) =
+                    oldItem.name == newItem.name && oldItem.value == newItem.value
+            }
+    }
+}

app/src/main/java/org/oxycblt/auxio/home/EdgeFrameLayout.kt

@@ -22,6 +22,7 @@ import android.util.AttributeSet
 import android.view.WindowInsets
 import android.widget.FrameLayout
 import androidx.annotation.AttrRes
+import androidx.core.view.updatePadding
 import org.oxycblt.auxio.util.systemBarInsetsCompat
 
 /**
@@ -38,7 +39,7 @@ constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr
 
     override fun onApplyWindowInsets(insets: WindowInsets): WindowInsets {
         // Prevent excessive layouts by using translation instead of padding.
-        translationY = -insets.systemBarInsetsCompat.bottom.toFloat()
+        updatePadding(bottom = insets.systemBarInsetsCompat.bottom)
         return insets
     }
 }

app/src/main/java/org/oxycblt/auxio/home/HomeFragment.kt

@@ -23,6 +23,7 @@ import android.view.MenuItem
 import android.view.View
 import androidx.activity.result.ActivityResultLauncher
 import androidx.activity.result.contract.ActivityResultContracts
+import androidx.core.view.MenuCompat
 import androidx.core.view.isVisible
 import androidx.core.view.iterator
 import androidx.core.view.updatePadding
@@ -37,6 +38,7 @@ import androidx.viewpager2.widget.ViewPager2
 import com.google.android.material.appbar.AppBarLayout
 import com.google.android.material.tabs.TabLayoutMediator
 import com.google.android.material.transition.MaterialSharedAxis
+import dagger.hilt.android.AndroidEntryPoint
 import java.lang.reflect.Field
 import kotlin.math.abs
 import org.oxycblt.auxio.BuildConfig
@@ -48,11 +50,13 @@ import org.oxycblt.auxio.home.list.ArtistListFragment
 import org.oxycblt.auxio.home.list.GenreListFragment
 import org.oxycblt.auxio.home.list.SongListFragment
 import org.oxycblt.auxio.home.tabs.AdaptiveTabStrategy
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.selection.SelectionFragment
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.library.Library
+import org.oxycblt.auxio.music.model.Library
-import org.oxycblt.auxio.music.library.Sort
 import org.oxycblt.auxio.music.system.Indexer
+import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.ui.MainNavigationAction
 import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.*
@@ -62,9 +66,12 @@ import org.oxycblt.auxio.util.*
  * to other views.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class HomeFragment :
     SelectionFragment<FragmentHomeBinding>(), AppBarLayout.OnOffsetChangedListener {
-    private val homeModel: HomeViewModel by androidActivityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
+    private val homeModel: HomeViewModel by activityViewModels()
     private val musicModel: MusicViewModel by activityViewModels()
     private val navModel: NavigationViewModel by activityViewModels()
     private var storagePermissionLauncher: ActivityResultLauncher<String>? = null
@@ -98,7 +105,10 @@ class HomeFragment :
 
         // --- UI SETUP ---
         binding.homeAppbar.addOnOffsetChangedListener(this)
-        binding.homeToolbar.setOnMenuItemClickListener(this)
+        binding.homeToolbar.apply {
+            setOnMenuItemClickListener(this@HomeFragment)
+            MenuCompat.setGroupDividerEnabled(menu, true)
+        }
 
         // Load the track color in manually as it's unclear whether the track actually supports
         // using a ColorStateList in the resources
@@ -207,11 +217,18 @@ class HomeFragment :
                 // Junk click event when opening the menu
             }
             R.id.option_sort_asc -> {
-                item.isChecked = !item.isChecked
+                item.isChecked = true
                 homeModel.setSortForCurrentTab(
                     homeModel
                         .getSortForTab(homeModel.currentTabMode.value)
-                        .withAscending(item.isChecked))
+                        .withDirection(Sort.Direction.ASCENDING))
+            }
+            R.id.option_sort_dec -> {
+                item.isChecked = true
+                homeModel.setSortForCurrentTab(
+                    homeModel
+                        .getSortForTab(homeModel.currentTabMode.value)
+                        .withDirection(Sort.Direction.DESCENDING))
             }
             else -> {
                 // Sorting option was selected, mark it as selected and update the mode
@@ -264,6 +281,7 @@ class HomeFragment :
                 // Only allow sorting by name, count, and duration for artists
                 MusicMode.ARTISTS -> { id ->
                         id == R.id.option_sort_asc ||
+                            id == R.id.option_sort_dec ||
                             id == R.id.option_sort_name ||
                             id == R.id.option_sort_count ||
                             id == R.id.option_sort_duration
@@ -271,6 +289,7 @@ class HomeFragment :
                 // Only allow sorting by name, count, and duration for genres
                 MusicMode.GENRES -> { id ->
                         id == R.id.option_sort_asc ||
+                            id == R.id.option_sort_dec ||
                             id == R.id.option_sort_name ||
                             id == R.id.option_sort_count ||
                             id == R.id.option_sort_duration
@@ -286,7 +305,10 @@ class HomeFragment :
             // Check the ascending option and corresponding sort option to align with
             // the current sort of the tab.
             if (option.itemId == toHighlight.mode.itemId ||
-                (option.itemId == R.id.option_sort_asc && toHighlight.isAscending)) {
+                (option.itemId == R.id.option_sort_asc &&
+                    toHighlight.direction == Sort.Direction.ASCENDING) ||
+                (option.itemId == R.id.option_sort_dec &&
+                    toHighlight.direction == Sort.Direction.DESCENDING)) {
                 option.isChecked = true
             }
 

app/src/main/java/org/oxycblt/auxio/home/HomeModule.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Auxio Project
+ * Copyright (c) 2023 Auxio Project
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -15,17 +15,15 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.extractor
+package org.oxycblt.auxio.home
 
-/**
+import dagger.Binds
- * Represents the result of an extraction operation.
+import dagger.Module
- * @author Alexander Capehart (OxygenCobalt)
+import dagger.hilt.InstallIn
- */
+import dagger.hilt.components.SingletonComponent
-enum class ExtractionResult {
+
-    /** A raw song was successfully extracted from the cache. */
+@Module
-    CACHED,
+@InstallIn(SingletonComponent::class)
-    /** A raw song was successfully extracted from parsing it's file. */
+interface HomeModule {
-    PARSED,
+    @Binds fun settings(homeSettings: HomeSettingsImpl): HomeSettings
-    /** A raw song could not be parsed. */
-    NONE
 }

app/src/main/java/org/oxycblt/auxio/home/HomeSettings.kt

@@ -19,6 +19,8 @@ package org.oxycblt.auxio.home
 
 import android.content.Context
 import androidx.core.content.edit
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.home.tabs.Tab
 import org.oxycblt.auxio.settings.Settings
@@ -40,39 +42,30 @@ interface HomeSettings : Settings<HomeSettings.Listener> {
         /** Called when the [shouldHideCollaborators] configuration changes. */
         fun onHideCollaboratorsChanged()
     }
+}
 
-    private class Real(context: Context) : Settings.Real<Listener>(context), HomeSettings {
+class HomeSettingsImpl @Inject constructor(@ApplicationContext context: Context) :
-        override var homeTabs: Array<Tab>
+    Settings.Impl<HomeSettings.Listener>(context), HomeSettings {
-            get() =
+    override var homeTabs: Array<Tab>
-                Tab.fromIntCode(
+        get() =
-                    sharedPreferences.getInt(
+            Tab.fromIntCode(
-                        getString(R.string.set_key_home_tabs), Tab.SEQUENCE_DEFAULT))
+                sharedPreferences.getInt(
-                    ?: unlikelyToBeNull(Tab.fromIntCode(Tab.SEQUENCE_DEFAULT))
+                    getString(R.string.set_key_home_tabs), Tab.SEQUENCE_DEFAULT))
-            set(value) {
+                ?: unlikelyToBeNull(Tab.fromIntCode(Tab.SEQUENCE_DEFAULT))
-                sharedPreferences.edit {
+        set(value) {
-                    putInt(getString(R.string.set_key_home_tabs), Tab.toIntCode(value))
+            sharedPreferences.edit {
-                    apply()
+                putInt(getString(R.string.set_key_home_tabs), Tab.toIntCode(value))
-                }
+                apply()
-            }
-
-        override val shouldHideCollaborators: Boolean
-            get() =
-                sharedPreferences.getBoolean(getString(R.string.set_key_hide_collaborators), false)
-
-        override fun onSettingChanged(key: String, listener: Listener) {
-            when (key) {
-                getString(R.string.set_key_home_tabs) -> listener.onTabsChanged()
-                getString(R.string.set_key_hide_collaborators) ->
-                    listener.onHideCollaboratorsChanged()
             }
         }
-    }
 
-    companion object {
+    override val shouldHideCollaborators: Boolean
-        /**
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_hide_collaborators), false)
-         * Get a framework-backed implementation.
+
-         * @param context [Context] required.
+    override fun onSettingChanged(key: String, listener: HomeSettings.Listener) {
-         */
+        when (key) {
-        fun from(context: Context): HomeSettings = Real(context)
+            getString(R.string.set_key_home_tabs) -> listener.onTabsChanged()
+            getString(R.string.set_key_hide_collaborators) -> listener.onHideCollaboratorsChanged()
+        }
     }
 }

app/src/main/java/org/oxycblt/auxio/home/HomeViewModel.kt

@@ -17,15 +17,15 @@
  
 package org.oxycblt.auxio.home
 
-import android.app.Application
+import androidx.lifecycle.ViewModel
-import androidx.lifecycle.AndroidViewModel
+import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import org.oxycblt.auxio.home.tabs.Tab
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.MusicStore
+import org.oxycblt.auxio.music.model.Library
-import org.oxycblt.auxio.music.library.Library
-import org.oxycblt.auxio.music.library.Sort
 import org.oxycblt.auxio.playback.PlaybackSettings
 import org.oxycblt.auxio.util.logD
 
@@ -33,12 +33,15 @@ import org.oxycblt.auxio.util.logD
  * The ViewModel for managing the tab data and lists of the home view.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class HomeViewModel(application: Application) :
+@HiltViewModel
-    AndroidViewModel(application), MusicStore.Listener, HomeSettings.Listener {
+class HomeViewModel
-    private val musicStore = MusicStore.getInstance()
+@Inject
-    private val homeSettings = HomeSettings.from(application)
+constructor(
-    private val musicSettings = MusicSettings.from(application)
+    private val homeSettings: HomeSettings,
-    private val playbackSettings = PlaybackSettings.from(application)
+    private val playbackSettings: PlaybackSettings,
+    private val musicRepository: MusicRepository,
+    private val musicSettings: MusicSettings
+) : ViewModel(), MusicRepository.Listener, HomeSettings.Listener {
 
     private val _songsList = MutableStateFlow(listOf<Song>())
     /** A list of [Song]s, sorted by the preferred [Sort], to be shown in the home view. */
@@ -92,13 +95,13 @@ class HomeViewModel(application: Application) :
     val isFastScrolling: StateFlow<Boolean> = _isFastScrolling
 
     init {
-        musicStore.addListener(this)
+        musicRepository.addListener(this)
         homeSettings.registerListener(this)
     }
 
     override fun onCleared() {
         super.onCleared()
-        musicStore.removeListener(this)
+        musicRepository.removeListener(this)
         homeSettings.unregisterListener(this)
     }
 
@@ -130,7 +133,7 @@ class HomeViewModel(application: Application) :
     override fun onHideCollaboratorsChanged() {
         // Changes in the hide collaborator setting will change the artist contents
         // of the library, consider it a library update.
-        onLibraryChanged(musicStore.library)
+        onLibraryChanged(musicRepository.library)
     }
 
     /**

app/src/main/java/org/oxycblt/auxio/home/list/AlbumListFragment.kt

@@ -23,6 +23,7 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.activityViewModels
+import dagger.hilt.android.AndroidEntryPoint
 import java.util.Formatter
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
@@ -30,25 +31,32 @@ import org.oxycblt.auxio.home.HomeViewModel
 import org.oxycblt.auxio.home.fastscroll.FastScrollRecyclerView
 import org.oxycblt.auxio.list.*
 import org.oxycblt.auxio.list.ListFragment
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
 import org.oxycblt.auxio.list.adapter.ListDiffer
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.recycler.AlbumViewHolder
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.playback.formatDurationMs
 import org.oxycblt.auxio.playback.secsToMs
+import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.collectImmediately
 
 /**
  * A [ListFragment] that shows a list of [Album]s.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class AlbumListFragment :
     ListFragment<Album, FragmentHomeListBinding>(),
     FastScrollRecyclerView.Listener,
     FastScrollRecyclerView.PopupProvider {
     private val homeModel: HomeViewModel by activityViewModels()
+    override val navModel: NavigationViewModel by activityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
     private val albumAdapter = AlbumAdapter(this)
     // Save memory by re-using the same formatter and string builder when creating popup text
     private val formatterSb = StringBuilder(64)

app/src/main/java/org/oxycblt/auxio/home/list/ArtistListFragment.kt

@@ -22,22 +22,26 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.activityViewModels
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
 import org.oxycblt.auxio.home.HomeViewModel
 import org.oxycblt.auxio.home.fastscroll.FastScrollRecyclerView
 import org.oxycblt.auxio.list.*
 import org.oxycblt.auxio.list.ListFragment
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
 import org.oxycblt.auxio.list.adapter.ListDiffer
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.recycler.ArtistViewHolder
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.playback.formatDurationMs
+import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.collectImmediately
 import org.oxycblt.auxio.util.nonZeroOrNull
 
@@ -45,11 +49,15 @@ import org.oxycblt.auxio.util.nonZeroOrNull
  * A [ListFragment] that shows a list of [Artist]s.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class ArtistListFragment :
     ListFragment<Artist, FragmentHomeListBinding>(),
     FastScrollRecyclerView.PopupProvider,
     FastScrollRecyclerView.Listener {
     private val homeModel: HomeViewModel by activityViewModels()
+    override val navModel: NavigationViewModel by activityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
     private val artistAdapter = ArtistAdapter(this)
 
     override fun onCreateBinding(inflater: LayoutInflater) =

app/src/main/java/org/oxycblt/auxio/home/list/GenreListFragment.kt

@@ -22,33 +22,41 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.activityViewModels
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
 import org.oxycblt.auxio.home.HomeViewModel
 import org.oxycblt.auxio.home.fastscroll.FastScrollRecyclerView
 import org.oxycblt.auxio.list.*
 import org.oxycblt.auxio.list.ListFragment
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
 import org.oxycblt.auxio.list.adapter.ListDiffer
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.recycler.GenreViewHolder
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.Genre
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.playback.formatDurationMs
+import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.collectImmediately
 
 /**
  * A [ListFragment] that shows a list of [Genre]s.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class GenreListFragment :
     ListFragment<Genre, FragmentHomeListBinding>(),
     FastScrollRecyclerView.PopupProvider,
     FastScrollRecyclerView.Listener {
     private val homeModel: HomeViewModel by activityViewModels()
+    override val navModel: NavigationViewModel by activityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
     private val genreAdapter = GenreAdapter(this)
 
     override fun onCreateBinding(inflater: LayoutInflater) =

app/src/main/java/org/oxycblt/auxio/home/list/SongListFragment.kt

@@ -23,6 +23,7 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.activityViewModels
+import dagger.hilt.android.AndroidEntryPoint
 import java.util.Formatter
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
@@ -30,28 +31,35 @@ import org.oxycblt.auxio.home.HomeViewModel
 import org.oxycblt.auxio.home.fastscroll.FastScrollRecyclerView
 import org.oxycblt.auxio.list.*
 import org.oxycblt.auxio.list.ListFragment
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
 import org.oxycblt.auxio.list.adapter.ListDiffer
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.recycler.SongViewHolder
+import org.oxycblt.auxio.list.selection.SelectionViewModel
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.playback.formatDurationMs
 import org.oxycblt.auxio.playback.secsToMs
+import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.util.collectImmediately
 
 /**
  * A [ListFragment] that shows a list of [Song]s.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class SongListFragment :
     ListFragment<Song, FragmentHomeListBinding>(),
     FastScrollRecyclerView.PopupProvider,
     FastScrollRecyclerView.Listener {
     private val homeModel: HomeViewModel by activityViewModels()
+    override val navModel: NavigationViewModel by activityViewModels()
+    override val playbackModel: PlaybackViewModel by activityViewModels()
+    override val selectionModel: SelectionViewModel by activityViewModels()
     private val songAdapter = SongAdapter(this)
     // Save memory by re-using the same formatter and string builder when creating popup text
     private val formatterSb = StringBuilder(64)

app/src/main/java/org/oxycblt/auxio/home/tabs/TabCustomizeDialog.kt

@@ -22,6 +22,8 @@ import android.view.LayoutInflater
 import androidx.appcompat.app.AlertDialog
 import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.RecyclerView
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import org.oxycblt.auxio.BuildConfig
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogTabsBinding
@@ -34,10 +36,12 @@ import org.oxycblt.auxio.util.logD
  * A [ViewBindingDialogFragment] that allows the user to modify the home [Tab] configuration.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class TabCustomizeDialog :
     ViewBindingDialogFragment<DialogTabsBinding>(), EditableListListener<Tab> {
     private val tabAdapter = TabAdapter(this)
     private var touchHelper: ItemTouchHelper? = null
+    @Inject lateinit var homeSettings: HomeSettings
 
     override fun onCreateBinding(inflater: LayoutInflater) = DialogTabsBinding.inflate(inflater)
 
@@ -46,13 +50,13 @@ class TabCustomizeDialog :
             .setTitle(R.string.set_lib_tabs)
             .setPositiveButton(R.string.lbl_ok) { _, _ ->
                 logD("Committing tab changes")
-                HomeSettings.from(requireContext()).homeTabs = tabAdapter.tabs
+                homeSettings.homeTabs = tabAdapter.tabs
             }
             .setNegativeButton(R.string.lbl_cancel, null)
     }
 
     override fun onBindingCreated(binding: DialogTabsBinding, savedInstanceState: Bundle?) {
-        var tabs = HomeSettings.from(requireContext()).homeTabs
+        var tabs = homeSettings.homeTabs
         // Try to restore a pending tab configuration that was saved prior.
         if (savedInstanceState != null) {
             val savedTabs = Tab.fromIntCode(savedInstanceState.getInt(KEY_TABS))

app/src/main/java/org/oxycblt/auxio/image/BitmapProvider.kt

@@ -20,10 +20,12 @@ package org.oxycblt.auxio.image
 import android.content.Context
 import android.graphics.Bitmap
 import androidx.core.graphics.drawable.toBitmap
-import coil.imageLoader
+import coil.ImageLoader
 import coil.request.Disposable
 import coil.request.ImageRequest
 import coil.size.Size
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
 import org.oxycblt.auxio.image.extractor.SquareFrameTransform
 import org.oxycblt.auxio.music.Song
 
@@ -38,7 +40,12 @@ import org.oxycblt.auxio.music.Song
  * @param context [Context] required to load images.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class BitmapProvider(private val context: Context) {
+class BitmapProvider
+@Inject
+constructor(
+    @ApplicationContext private val context: Context,
+    private val imageLoader: ImageLoader
+) {
     /**
      * An extension of [Disposable] with an additional [Target] to deliver the final [Bitmap] to.
      */
@@ -94,7 +101,7 @@ class BitmapProvider(private val context: Context) {
                     onSuccess = {
                         synchronized(this) {
                             if (currentHandle == handle) {
-                                // Has not been superceded by a new request, can deliver
+                                // Has not been superseded by a new request, can deliver
                                 // this result.
                                 target.onCompleted(it.toBitmap())
                             }
@@ -103,13 +110,13 @@ class BitmapProvider(private val context: Context) {
                     onError = {
                         synchronized(this) {
                             if (currentHandle == handle) {
-                                // Has not been superceded by a new request, can deliver
+                                // Has not been superseded by a new request, can deliver
                                 // this result.
                                 target.onCompleted(null)
                             }
                         }
                     })
-        currentRequest = Request(context.imageLoader.enqueue(imageRequest.build()), target)
+        currentRequest = Request(imageLoader.enqueue(imageRequest.build()), target)
     }
 
     /** Release this instance, cancelling any currently running operations. */

app/src/main/java/org/oxycblt/auxio/image/ImageModule.kt

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.image
+
+import android.content.Context
+import coil.ImageLoader
+import coil.request.CachePolicy
+import dagger.Binds
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+import org.oxycblt.auxio.image.extractor.AlbumCoverFetcher
+import org.oxycblt.auxio.image.extractor.ArtistImageFetcher
+import org.oxycblt.auxio.image.extractor.ErrorCrossfadeTransitionFactory
+import org.oxycblt.auxio.image.extractor.GenreImageFetcher
+import org.oxycblt.auxio.image.extractor.MusicKeyer
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface ImageModule {
+    @Binds fun settings(imageSettings: ImageSettingsImpl): ImageSettings
+}
+
+@Module
+@InstallIn(SingletonComponent::class)
+class CoilModule {
+    @Singleton
+    @Provides
+    fun imageLoader(
+        @ApplicationContext context: Context,
+        songFactory: AlbumCoverFetcher.SongFactory,
+        albumFactory: AlbumCoverFetcher.AlbumFactory,
+        artistFactory: ArtistImageFetcher.Factory,
+        genreFactory: GenreImageFetcher.Factory
+    ) =
+        ImageLoader.Builder(context)
+            .components {
+                // Add fetchers for Music components to make them usable with ImageRequest
+                add(MusicKeyer())
+                add(songFactory)
+                add(albumFactory)
+                add(artistFactory)
+                add(genreFactory)
+            }
+            // Use our own crossfade with error drawable support
+            .transitionFactory(ErrorCrossfadeTransitionFactory())
+            // Not downloading anything, so no disk-caching
+            .diskCachePolicy(CachePolicy.DISABLED)
+            .build()
+}

app/src/main/java/org/oxycblt/auxio/image/ImageSettings.kt

@@ -19,6 +19,8 @@ package org.oxycblt.auxio.image
 
 import android.content.Context
 import androidx.core.content.edit
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.settings.Settings
 import org.oxycblt.auxio.util.logD
@@ -35,53 +37,46 @@ interface ImageSettings : Settings<ImageSettings.Listener> {
         /** Called when [coverMode] changes. */
         fun onCoverModeChanged() {}
     }
+}
 
-    private class Real(context: Context) : Settings.Real<Listener>(context), ImageSettings {
+class ImageSettingsImpl @Inject constructor(@ApplicationContext context: Context) :
-        override val coverMode: CoverMode
+    Settings.Impl<ImageSettings.Listener>(context), ImageSettings {
-            get() =
+    override val coverMode: CoverMode
-                CoverMode.fromIntCode(
+        get() =
-                    sharedPreferences.getInt(getString(R.string.set_key_cover_mode), Int.MIN_VALUE))
+            CoverMode.fromIntCode(
-                    ?: CoverMode.MEDIA_STORE
+                sharedPreferences.getInt(getString(R.string.set_key_cover_mode), Int.MIN_VALUE))
+                ?: CoverMode.MEDIA_STORE
 
-        override fun migrate() {
+    override fun migrate() {
-            // Show album covers and Ignore MediaStore covers were unified in 3.0.0
+        // Show album covers and Ignore MediaStore covers were unified in 3.0.0
-            if (sharedPreferences.contains(OLD_KEY_SHOW_COVERS) ||
+        if (sharedPreferences.contains(OLD_KEY_SHOW_COVERS) ||
-                sharedPreferences.contains(OLD_KEY_QUALITY_COVERS)) {
+            sharedPreferences.contains(OLD_KEY_QUALITY_COVERS)) {
-                logD("Migrating cover settings")
+            logD("Migrating cover settings")
 
-                val mode =
+            val mode =
-                    when {
+                when {
-                        !sharedPreferences.getBoolean(OLD_KEY_SHOW_COVERS, true) -> CoverMode.OFF
+                    !sharedPreferences.getBoolean(OLD_KEY_SHOW_COVERS, true) -> CoverMode.OFF
-                        !sharedPreferences.getBoolean(OLD_KEY_QUALITY_COVERS, true) ->
+                    !sharedPreferences.getBoolean(OLD_KEY_QUALITY_COVERS, true) ->
-                            CoverMode.MEDIA_STORE
+                        CoverMode.MEDIA_STORE
-                        else -> CoverMode.QUALITY
+                    else -> CoverMode.QUALITY
-                    }
-
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_cover_mode), mode.intCode)
-                    remove(OLD_KEY_SHOW_COVERS)
-                    remove(OLD_KEY_QUALITY_COVERS)
                 }
-            }
-        }
 
-        override fun onSettingChanged(key: String, listener: Listener) {
+            sharedPreferences.edit {
-            if (key == getString(R.string.set_key_cover_mode)) {
+                putInt(getString(R.string.set_key_cover_mode), mode.intCode)
-                listOf(key, listener)
+                remove(OLD_KEY_SHOW_COVERS)
+                remove(OLD_KEY_QUALITY_COVERS)
             }
         }
-
-        private companion object {
-            const val OLD_KEY_SHOW_COVERS = "KEY_SHOW_COVERS"
-            const val OLD_KEY_QUALITY_COVERS = "KEY_QUALITY_COVERS"
-        }
     }
 
-    companion object {
+    override fun onSettingChanged(key: String, listener: ImageSettings.Listener) {
-        /**
+        if (key == getString(R.string.set_key_cover_mode)) {
-         * Get a framework-backed implementation.
+            listener.onCoverModeChanged()
-         * @param context [Context] required.
+        }
-         */
+    }
-        fun from(context: Context): ImageSettings = Real(context)
+
+    private companion object {
+        const val OLD_KEY_SHOW_COVERS = "KEY_SHOW_COVERS"
+        const val OLD_KEY_QUALITY_COVERS = "KEY_QUALITY_COVERS"
     }
 }

app/src/main/java/org/oxycblt/auxio/image/PlaybackIndicatorView.kt

@@ -26,6 +26,8 @@ import androidx.annotation.AttrRes
 import androidx.appcompat.widget.AppCompatImageView
 import androidx.core.widget.ImageViewCompat
 import com.google.android.material.shape.MaterialShapeDrawable
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import kotlin.math.max
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.ui.UISettings
@@ -41,6 +43,7 @@ import org.oxycblt.auxio.util.getDrawableCompat
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class PlaybackIndicatorView
 @JvmOverloads
 constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr: Int = 0) :
@@ -52,6 +55,7 @@ constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr
     private val indicatorMatrix = Matrix()
     private val indicatorMatrixSrc = RectF()
     private val indicatorMatrixDst = RectF()
+    @Inject lateinit var uiSettings: UISettings
 
     /**
      * The corner radius of this view. This allows the outer ImageGroup to apply it's corner radius
@@ -61,7 +65,7 @@ constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr
         set(value) {
             field = value
             (background as? MaterialShapeDrawable)?.let { bg ->
-                if (UISettings.from(context).roundMode) {
+                if (uiSettings.roundMode) {
                     bg.setCornerSize(value)
                 } else {
                     bg.setCornerSize(0f)

app/src/main/java/org/oxycblt/auxio/image/StyledImageView.kt

@@ -29,9 +29,12 @@ import androidx.annotation.StringRes
 import androidx.appcompat.widget.AppCompatImageView
 import androidx.core.content.res.ResourcesCompat
 import androidx.core.graphics.drawable.DrawableCompat
-import coil.dispose
+import coil.ImageLoader
-import coil.load
+import coil.request.ImageRequest
+import coil.util.CoilUtils
 import com.google.android.material.shape.MaterialShapeDrawable
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.image.extractor.SquareFrameTransform
 import org.oxycblt.auxio.music.Album
@@ -53,10 +56,14 @@ import org.oxycblt.auxio.util.getDrawableCompat
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class StyledImageView
 @JvmOverloads
 constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr: Int = 0) :
     AppCompatImageView(context, attrs, defStyleAttr) {
+    @Inject lateinit var imageLoader: ImageLoader
+    @Inject lateinit var uiSettings: UISettings
+
     init {
         // Load view attributes
         val styledAttrs = context.obtainStyledAttributes(attrs, R.styleable.StyledImageView)
@@ -81,7 +88,7 @@ constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr
         background =
             MaterialShapeDrawable().apply {
                 fillColor = context.getColorCompat(R.color.sel_cover_bg)
-                if (UISettings.from(context).roundMode) {
+                if (uiSettings.roundMode) {
                     // Only use the specified corner radius when round mode is enabled.
                     setCornerSize(cornerRadius)
                 }
@@ -120,13 +127,16 @@ constructor(context: Context, attrs: AttributeSet? = null, @AttrRes defStyleAttr
      * field for the name of the [Music].
      */
     private fun bindImpl(music: Music, @DrawableRes errorRes: Int, @StringRes descRes: Int) {
+        val request =
+            ImageRequest.Builder(context)
+                .data(music)
+                .error(StyledDrawable(context, context.getDrawableCompat(errorRes)))
+                .transformations(SquareFrameTransform.INSTANCE)
+                .target(this)
+                .build()
         // Dispose of any previous image request and load a new image.
-        dispose()
+        CoilUtils.dispose(this)
-        load(music) {
+        imageLoader.enqueue(request)
-            error(StyledDrawable(context, context.getDrawableCompat(errorRes)))
-            transformations(SquareFrameTransform.INSTANCE)
-        }
-
         // Update the content description to the specified resource.
         contentDescription = context.getString(descRes, music.resolveName(context))
     }

app/src/main/java/org/oxycblt/auxio/image/extractor/Components.kt

@@ -27,15 +27,17 @@ import coil.fetch.SourceResult
 import coil.key.Keyer
 import coil.request.Options
 import coil.size.Size
+import javax.inject.Inject
 import kotlin.math.min
 import okio.buffer
 import okio.source
+import org.oxycblt.auxio.image.ImageSettings
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Genre
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.library.Sort
 
 /**
  * A [Keyer] implementation for [Music] data.
@@ -57,9 +59,13 @@ class MusicKeyer : Keyer<Music> {
  * @author Alexander Capehart (OxygenCobalt)
  */
 class AlbumCoverFetcher
-private constructor(private val context: Context, private val album: Album) : Fetcher {
+private constructor(
+    private val context: Context,
+    private val imageSettings: ImageSettings,
+    private val album: Album
+) : Fetcher {
     override suspend fun fetch(): FetchResult? =
-        Covers.fetch(context, album)?.run {
+        Covers.fetch(context, imageSettings, album)?.run {
             SourceResult(
                 source = ImageSource(source().buffer(), context),
                 mimeType = null,
@@ -67,15 +73,17 @@ private constructor(private val context: Context, private val album: Album) : Fe
         }
 
     /** A [Fetcher.Factory] implementation that works with [Song]s. */
-    class SongFactory : Fetcher.Factory<Song> {
+    class SongFactory @Inject constructor(private val imageSettings: ImageSettings) :
+        Fetcher.Factory<Song> {
         override fun create(data: Song, options: Options, imageLoader: ImageLoader) =
-            AlbumCoverFetcher(options.context, data.album)
+            AlbumCoverFetcher(options.context, imageSettings, data.album)
     }
 
     /** A [Fetcher.Factory] implementation that works with [Album]s. */
-    class AlbumFactory : Fetcher.Factory<Album> {
+    class AlbumFactory @Inject constructor(private val imageSettings: ImageSettings) :
+        Fetcher.Factory<Album> {
         override fun create(data: Album, options: Options, imageLoader: ImageLoader) =
-            AlbumCoverFetcher(options.context, data)
+            AlbumCoverFetcher(options.context, imageSettings, data)
     }
 }
 
@@ -86,20 +94,23 @@ private constructor(private val context: Context, private val album: Album) : Fe
 class ArtistImageFetcher
 private constructor(
     private val context: Context,
+    private val imageSettings: ImageSettings,
     private val size: Size,
     private val artist: Artist
 ) : Fetcher {
     override suspend fun fetch(): FetchResult? {
         // Pick the "most prominent" albums (i.e albums with the most songs) to show in the image.
-        val albums = Sort(Sort.Mode.ByCount, false).albums(artist.albums)
+        val albums = Sort(Sort.Mode.ByCount, Sort.Direction.DESCENDING).albums(artist.albums)
-        val results = albums.mapAtMostNotNull(4) { album -> Covers.fetch(context, album) }
+        val results =
+            albums.mapAtMostNotNull(4) { album -> Covers.fetch(context, imageSettings, album) }
         return Images.createMosaic(context, results, size)
     }
 
     /** [Fetcher.Factory] implementation. */
-    class Factory : Fetcher.Factory<Artist> {
+    class Factory @Inject constructor(private val imageSettings: ImageSettings) :
+        Fetcher.Factory<Artist> {
         override fun create(data: Artist, options: Options, imageLoader: ImageLoader) =
-            ArtistImageFetcher(options.context, options.size, data)
+            ArtistImageFetcher(options.context, imageSettings, options.size, data)
     }
 }
 
@@ -110,18 +121,20 @@ private constructor(
 class GenreImageFetcher
 private constructor(
     private val context: Context,
+    private val imageSettings: ImageSettings,
     private val size: Size,
     private val genre: Genre
 ) : Fetcher {
     override suspend fun fetch(): FetchResult? {
-        val results = genre.albums.mapAtMostNotNull(4) { Covers.fetch(context, it) }
+        val results = genre.albums.mapAtMostNotNull(4) { Covers.fetch(context, imageSettings, it) }
         return Images.createMosaic(context, results, size)
     }
 
     /** [Fetcher.Factory] implementation. */
-    class Factory : Fetcher.Factory<Genre> {
+    class Factory @Inject constructor(private val imageSettings: ImageSettings) :
+        Fetcher.Factory<Genre> {
         override fun create(data: Genre, options: Options, imageLoader: ImageLoader) =
-            GenreImageFetcher(options.context, options.size, data)
+            GenreImageFetcher(options.context, imageSettings, options.size, data)
     }
 }
 

app/src/main/java/org/oxycblt/auxio/image/extractor/Covers.kt

@@ -24,6 +24,7 @@ import com.google.android.exoplayer2.MediaMetadata
 import com.google.android.exoplayer2.MetadataRetriever
 import com.google.android.exoplayer2.metadata.flac.PictureFrame
 import com.google.android.exoplayer2.metadata.id3.ApicFrame
+import com.google.android.exoplayer2.source.DefaultMediaSourceFactory
 import java.io.ByteArrayInputStream
 import java.io.InputStream
 import kotlinx.coroutines.Dispatchers
@@ -31,6 +32,7 @@ import kotlinx.coroutines.withContext
 import org.oxycblt.auxio.image.CoverMode
 import org.oxycblt.auxio.image.ImageSettings
 import org.oxycblt.auxio.music.Album
+import org.oxycblt.auxio.music.AudioOnlyExtractors
 import org.oxycblt.auxio.util.logD
 import org.oxycblt.auxio.util.logW
 
@@ -42,13 +44,14 @@ object Covers {
     /**
      * Fetch an album cover, respecting the current cover configuration.
      * @param context [Context] required to load the image.
+     * @param imageSettings [ImageSettings] required to obtain configuration information.
      * @param album [Album] to load the cover from.
      * @return An [InputStream] of image data if the cover loading was successful, null if the cover
      * loading failed or should not occur.
      */
-    suspend fun fetch(context: Context, album: Album): InputStream? {
+    suspend fun fetch(context: Context, imageSettings: ImageSettings, album: Album): InputStream? {
         return try {
-            when (ImageSettings.from(context).coverMode) {
+            when (imageSettings.coverMode) {
                 CoverMode.OFF -> null
                 CoverMode.MEDIA_STORE -> fetchMediaStoreCovers(context, album)
                 CoverMode.QUALITY -> fetchQualityCovers(context, album)
@@ -102,7 +105,9 @@ object Covers {
      */
     private suspend fun fetchExoplayerCover(context: Context, album: Album): InputStream? {
         val uri = album.songs[0].uri
-        val future = MetadataRetriever.retrieveMetadata(context, MediaItem.fromUri(uri))
+        val future =
+            MetadataRetriever.retrieveMetadata(
+                DefaultMediaSourceFactory(context, AudioOnlyExtractors), MediaItem.fromUri(uri))
 
         // future.get is a blocking call that makes us spin until the future is done.
         // This is bad for a co-routine, as it prevents cancellation and by extension

app/src/main/java/org/oxycblt/auxio/list/Data.kt

@@ -24,6 +24,16 @@ interface Item
 
 /**
  * A "header" used for delimiting groups of data.
- * @param titleRes The string resource used for the header's title.
+ * @author Alexander Capehart (OxygenCobalt)
  */
-data class Header(@StringRes val titleRes: Int) : Item
+interface Header : Item {
+    /** The string resource used for the header's title. */
+    val titleRes: Int
+}
+
+/**
+ * A basic header with no additional actions.
+ * @param titleRes The string resource used for the header's title.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+data class BasicHeader(@StringRes override val titleRes: Int) : Header

app/src/main/java/org/oxycblt/auxio/list/ListFragment.kt

@@ -21,7 +21,8 @@ import android.view.MenuItem
 import android.view.View
 import androidx.annotation.MenuRes
 import androidx.appcompat.widget.PopupMenu
-import androidx.fragment.app.activityViewModels
+import androidx.core.internal.view.SupportMenu
+import androidx.core.view.MenuCompat
 import androidx.recyclerview.widget.RecyclerView
 import androidx.viewbinding.ViewBinding
 import org.oxycblt.auxio.MainFragmentDirections
@@ -39,7 +40,7 @@ import org.oxycblt.auxio.util.showToast
  */
 abstract class ListFragment<in T : Music, VB : ViewBinding> :
     SelectionFragment<VB>(), SelectableListListener<T> {
-    protected val navModel: NavigationViewModel by activityViewModels()
+    protected abstract val navModel: NavigationViewModel
     private var currentMenu: PopupMenu? = null
 
     override fun onDestroyBinding(binding: VB) {
@@ -238,6 +239,8 @@ abstract class ListFragment<in T : Music, VB : ViewBinding> :
         currentMenu =
             PopupMenu(requireContext(), anchor).apply {
                 inflate(menuRes)
+                logD(menu is SupportMenu)
+                MenuCompat.setGroupDividerEnabled(menu, true)
                 block()
                 setOnDismissListener { currentMenu = null }
                 show()

app/src/main/java/org/oxycblt/auxio/list/Sort.kt

@@ -15,15 +15,16 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.library
+package org.oxycblt.auxio.list
 
 import androidx.annotation.IdRes
 import kotlin.math.max
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.R
+import org.oxycblt.auxio.list.Sort.Mode
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.library.Sort.Mode
+import org.oxycblt.auxio.music.metadata.Date
-import org.oxycblt.auxio.music.tags.Date
+import org.oxycblt.auxio.music.metadata.Disc
 
 /**
  * A sorting method.
@@ -31,30 +32,30 @@ import org.oxycblt.auxio.music.tags.Date
  * This can be used not only to sort items, but also represent a sorting mode within the UI.
  *
  * @param mode A [Mode] dictating how to sort the list.
- * @param isAscending Whether to sort in ascending or descending order.
+ * @param direction The [Direction] to sort in.
  * @author Alexander Capehart (OxygenCobalt)
  */
-data class Sort(val mode: Mode, val isAscending: Boolean) {
+data class Sort(val mode: Mode, val direction: Direction) {
     /**
-     * Create a new [Sort] with the same [mode], but different [isAscending] value.
+     * Create a new [Sort] with the same [mode], but a different [Direction].
-     * @param isAscending Whether the new sort should be in ascending order or not.
+     * @param direction The new [Direction] to sort in.
-     * @return A new sort with the same mode, but with the new [isAscending] value applied.
+     * @return A new sort with the same mode, but with the new [Direction] value applied.
      */
-    fun withAscending(isAscending: Boolean) = Sort(mode, isAscending)
+    fun withDirection(direction: Direction) = Sort(mode, direction)
 
     /**
-     * Create a new [Sort] with the same [isAscending] value, but different [mode] value.
+     * Create a new [Sort] with the same [direction] value, but different [mode] value.
      * @param mode Tbe new mode to use for the Sort.
-     * @return A new sort with the same [isAscending] value, but with the new [mode] applied.
+     * @return A new sort with the same [direction] value, but with the new [mode] applied.
      */
-    fun withMode(mode: Mode) = Sort(mode, isAscending)
+    fun withMode(mode: Mode) = Sort(mode, direction)
 
     /**
      * Sort a list of [Song]s.
      * @param songs The list of [Song]s.
      * @return A new list of [Song]s sorted by this [Sort]'s configuration.
      */
-    fun songs(songs: Collection<Song>): List<Song> {
+    fun <T : Song> songs(songs: Collection<T>): List<T> {
         val mutable = songs.toMutableList()
         songsInPlace(mutable)
         return mutable
@@ -65,7 +66,7 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
      * @param albums The list of [Album]s.
      * @return A new list of [Album]s sorted by this [Sort]'s configuration.
      */
-    fun albums(albums: Collection<Album>): List<Album> {
+    fun <T : Album> albums(albums: Collection<T>): List<T> {
         val mutable = albums.toMutableList()
         albumsInPlace(mutable)
         return mutable
@@ -76,7 +77,7 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
      * @param artists The list of [Artist]s.
      * @return A new list of [Artist]s sorted by this [Sort]'s configuration.
      */
-    fun artists(artists: Collection<Artist>): List<Artist> {
+    fun <T : Artist> artists(artists: Collection<T>): List<T> {
         val mutable = artists.toMutableList()
         artistsInPlace(mutable)
         return mutable
@@ -87,7 +88,7 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
      * @param genres The list of [Genre]s.
      * @return A new list of [Genre]s sorted by this [Sort]'s configuration.
      */
-    fun genres(genres: Collection<Genre>): List<Genre> {
+    fun <T : Genre> genres(genres: Collection<T>): List<T> {
         val mutable = genres.toMutableList()
         genresInPlace(mutable)
         return mutable
@@ -97,32 +98,32 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
      * Sort a *mutable* list of [Song]s in-place using this [Sort]'s configuration.
      * @param songs The [Song]s to sort.
      */
-    private fun songsInPlace(songs: MutableList<Song>) {
+    private fun songsInPlace(songs: MutableList<out Song>) {
-        songs.sortWith(mode.getSongComparator(isAscending))
+        songs.sortWith(mode.getSongComparator(direction))
     }
 
     /**
      * Sort a *mutable* list of [Album]s in-place using this [Sort]'s configuration.
      * @param albums The [Album]s to sort.
      */
-    private fun albumsInPlace(albums: MutableList<Album>) {
+    private fun albumsInPlace(albums: MutableList<out Album>) {
-        albums.sortWith(mode.getAlbumComparator(isAscending))
+        albums.sortWith(mode.getAlbumComparator(direction))
     }
 
     /**
      * Sort a *mutable* list of [Artist]s in-place using this [Sort]'s configuration.
      * @param artists The [Album]s to sort.
      */
-    private fun artistsInPlace(artists: MutableList<Artist>) {
+    private fun artistsInPlace(artists: MutableList<out Artist>) {
-        artists.sortWith(mode.getArtistComparator(isAscending))
+        artists.sortWith(mode.getArtistComparator(direction))
     }
 
     /**
      * Sort a *mutable* list of [Genre]s in-place using this [Sort]'s configuration.
      * @param genres The [Genre]s to sort.
      */
-    private fun genresInPlace(genres: MutableList<Genre>) {
+    private fun genresInPlace(genres: MutableList<out Genre>) {
-        genres.sortWith(mode.getGenreComparator(isAscending))
+        genres.sortWith(mode.getGenreComparator(direction))
     }
 
     /**
@@ -133,8 +134,14 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
         // Sort's integer representation is formatted as AMMMM, where A is a bitflag
         // representing if the sort is in ascending or descending order, and M is the
         // integer representation of the sort mode.
-        get() = mode.intCode.shl(1) or if (isAscending) 1 else 0
+        get() =
+            mode.intCode.shl(1) or
+                when (direction) {
+                    Direction.ASCENDING -> 1
+                    Direction.DESCENDING -> 0
+                }
 
+    /** Describes the type of data to sort with. */
     sealed class Mode {
         /** The integer representation of this sort mode. */
         abstract val intCode: Int
@@ -143,37 +150,37 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
 
         /**
          * Get a [Comparator] that sorts [Song]s according to this [Mode].
-         * @param isAscending Whether to sort in ascending or descending order.
+         * @param direction The direction to sort in.
          * @return A [Comparator] that can be used to sort a [Song] list according to this [Mode].
          */
-        open fun getSongComparator(isAscending: Boolean): Comparator<Song> {
+        open fun getSongComparator(direction: Direction): Comparator<Song> {
             throw UnsupportedOperationException()
         }
 
         /**
          * Get a [Comparator] that sorts [Album]s according to this [Mode].
-         * @param isAscending Whether to sort in ascending or descending order.
+         * @param direction The direction to sort in.
          * @return A [Comparator] that can be used to sort a [Album] list according to this [Mode].
          */
-        open fun getAlbumComparator(isAscending: Boolean): Comparator<Album> {
+        open fun getAlbumComparator(direction: Direction): Comparator<Album> {
             throw UnsupportedOperationException()
         }
 
         /**
          * Return a [Comparator] that sorts [Artist]s according to this [Mode].
-         * @param isAscending Whether to sort in ascending or descending order.
+         * @param direction The direction to sort in.
          * @return A [Comparator] that can be used to sort a [Artist] list according to this [Mode].
          */
-        open fun getArtistComparator(isAscending: Boolean): Comparator<Artist> {
+        open fun getArtistComparator(direction: Direction): Comparator<Artist> {
             throw UnsupportedOperationException()
         }
 
         /**
          * Return a [Comparator] that sorts [Genre]s according to this [Mode].
-         * @param isAscending Whether to sort in ascending or descending order.
+         * @param direction The direction to sort in.
          * @return A [Comparator] that can be used to sort a [Genre] list according to this [Mode].
          */
-        open fun getGenreComparator(isAscending: Boolean): Comparator<Genre> {
+        open fun getGenreComparator(direction: Direction): Comparator<Genre> {
             throw UnsupportedOperationException()
         }
 
@@ -188,17 +195,17 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_name
 
-            override fun getSongComparator(isAscending: Boolean) =
+            override fun getSongComparator(direction: Direction) =
-                compareByDynamic(isAscending, BasicComparator.SONG)
+                compareByDynamic(direction, BasicComparator.SONG)
 
-            override fun getAlbumComparator(isAscending: Boolean) =
+            override fun getAlbumComparator(direction: Direction) =
-                compareByDynamic(isAscending, BasicComparator.ALBUM)
+                compareByDynamic(direction, BasicComparator.ALBUM)
 
-            override fun getArtistComparator(isAscending: Boolean) =
+            override fun getArtistComparator(direction: Direction) =
-                compareByDynamic(isAscending, BasicComparator.ARTIST)
+                compareByDynamic(direction, BasicComparator.ARTIST)
 
-            override fun getGenreComparator(isAscending: Boolean) =
+            override fun getGenreComparator(direction: Direction) =
-                compareByDynamic(isAscending, BasicComparator.GENRE)
+                compareByDynamic(direction, BasicComparator.GENRE)
         }
 
         /**
@@ -212,10 +219,10 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_album
 
-            override fun getSongComparator(isAscending: Boolean): Comparator<Song> =
+            override fun getSongComparator(direction: Direction): Comparator<Song> =
                 MultiComparator(
-                    compareByDynamic(isAscending, BasicComparator.ALBUM) { it.album },
+                    compareByDynamic(direction, BasicComparator.ALBUM) { it.album },
-                    compareBy(NullableComparator.INT) { it.disc },
+                    compareBy(NullableComparator.DISC) { it.disc },
                     compareBy(NullableComparator.INT) { it.track },
                     compareBy(BasicComparator.SONG))
         }
@@ -231,18 +238,18 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_artist
 
-            override fun getSongComparator(isAscending: Boolean): Comparator<Song> =
+            override fun getSongComparator(direction: Direction): Comparator<Song> =
                 MultiComparator(
-                    compareByDynamic(isAscending, ListComparator.ARTISTS) { it.artists },
+                    compareByDynamic(direction, ListComparator.ARTISTS) { it.artists },
                     compareByDescending(NullableComparator.DATE_RANGE) { it.album.dates },
                     compareByDescending(BasicComparator.ALBUM) { it.album },
-                    compareBy(NullableComparator.INT) { it.disc },
+                    compareBy(NullableComparator.DISC) { it.disc },
                     compareBy(NullableComparator.INT) { it.track },
                     compareBy(BasicComparator.SONG))
 
-            override fun getAlbumComparator(isAscending: Boolean): Comparator<Album> =
+            override fun getAlbumComparator(direction: Direction): Comparator<Album> =
                 MultiComparator(
-                    compareByDynamic(isAscending, ListComparator.ARTISTS) { it.artists },
+                    compareByDynamic(direction, ListComparator.ARTISTS) { it.artists },
                     compareByDescending(NullableComparator.DATE_RANGE) { it.dates },
                     compareBy(BasicComparator.ALBUM))
         }
@@ -259,17 +266,17 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_year
 
-            override fun getSongComparator(isAscending: Boolean): Comparator<Song> =
+            override fun getSongComparator(direction: Direction): Comparator<Song> =
                 MultiComparator(
-                    compareByDynamic(isAscending, NullableComparator.DATE_RANGE) { it.album.dates },
+                    compareByDynamic(direction, NullableComparator.DATE_RANGE) { it.album.dates },
                     compareByDescending(BasicComparator.ALBUM) { it.album },
-                    compareBy(NullableComparator.INT) { it.disc },
+                    compareBy(NullableComparator.DISC) { it.disc },
                     compareBy(NullableComparator.INT) { it.track },
                     compareBy(BasicComparator.SONG))
 
-            override fun getAlbumComparator(isAscending: Boolean): Comparator<Album> =
+            override fun getAlbumComparator(direction: Direction): Comparator<Album> =
                 MultiComparator(
-                    compareByDynamic(isAscending, NullableComparator.DATE_RANGE) { it.dates },
+                    compareByDynamic(direction, NullableComparator.DATE_RANGE) { it.dates },
                     compareBy(BasicComparator.ALBUM))
         }
 
@@ -281,25 +288,22 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_duration
 
-            override fun getSongComparator(isAscending: Boolean): Comparator<Song> =
+            override fun getSongComparator(direction: Direction): Comparator<Song> =
                 MultiComparator(
-                    compareByDynamic(isAscending) { it.durationMs },
+                    compareByDynamic(direction) { it.durationMs }, compareBy(BasicComparator.SONG))
-                    compareBy(BasicComparator.SONG))
 
-            override fun getAlbumComparator(isAscending: Boolean): Comparator<Album> =
+            override fun getAlbumComparator(direction: Direction): Comparator<Album> =
                 MultiComparator(
-                    compareByDynamic(isAscending) { it.durationMs },
+                    compareByDynamic(direction) { it.durationMs }, compareBy(BasicComparator.ALBUM))
-                    compareBy(BasicComparator.ALBUM))
 
-            override fun getArtistComparator(isAscending: Boolean): Comparator<Artist> =
+            override fun getArtistComparator(direction: Direction): Comparator<Artist> =
                 MultiComparator(
-                    compareByDynamic(isAscending, NullableComparator.LONG) { it.durationMs },
+                    compareByDynamic(direction, NullableComparator.LONG) { it.durationMs },
                     compareBy(BasicComparator.ARTIST))
 
-            override fun getGenreComparator(isAscending: Boolean): Comparator<Genre> =
+            override fun getGenreComparator(direction: Direction): Comparator<Genre> =
                 MultiComparator(
-                    compareByDynamic(isAscending) { it.durationMs },
+                    compareByDynamic(direction) { it.durationMs }, compareBy(BasicComparator.GENRE))
-                    compareBy(BasicComparator.GENRE))
         }
 
         /**
@@ -313,20 +317,18 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_count
 
-            override fun getAlbumComparator(isAscending: Boolean): Comparator<Album> =
+            override fun getAlbumComparator(direction: Direction): Comparator<Album> =
                 MultiComparator(
-                    compareByDynamic(isAscending) { it.songs.size },
+                    compareByDynamic(direction) { it.songs.size }, compareBy(BasicComparator.ALBUM))
-                    compareBy(BasicComparator.ALBUM))
 
-            override fun getArtistComparator(isAscending: Boolean): Comparator<Artist> =
+            override fun getArtistComparator(direction: Direction): Comparator<Artist> =
                 MultiComparator(
-                    compareByDynamic(isAscending, NullableComparator.INT) { it.songs.size },
+                    compareByDynamic(direction, NullableComparator.INT) { it.songs.size },
                     compareBy(BasicComparator.ARTIST))
 
-            override fun getGenreComparator(isAscending: Boolean): Comparator<Genre> =
+            override fun getGenreComparator(direction: Direction): Comparator<Genre> =
                 MultiComparator(
-                    compareByDynamic(isAscending) { it.songs.size },
+                    compareByDynamic(direction) { it.songs.size }, compareBy(BasicComparator.GENRE))
-                    compareBy(BasicComparator.GENRE))
         }
 
         /**
@@ -340,9 +342,9 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_disc
 
-            override fun getSongComparator(isAscending: Boolean): Comparator<Song> =
+            override fun getSongComparator(direction: Direction): Comparator<Song> =
                 MultiComparator(
-                    compareByDynamic(isAscending, NullableComparator.INT) { it.disc },
+                    compareByDynamic(direction, NullableComparator.DISC) { it.disc },
                     compareBy(NullableComparator.INT) { it.track },
                     compareBy(BasicComparator.SONG))
         }
@@ -358,10 +360,10 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_track
 
-            override fun getSongComparator(isAscending: Boolean): Comparator<Song> =
+            override fun getSongComparator(direction: Direction): Comparator<Song> =
                 MultiComparator(
-                    compareBy(NullableComparator.INT) { it.disc },
+                    compareBy(NullableComparator.DISC) { it.disc },
-                    compareByDynamic(isAscending, NullableComparator.INT) { it.track },
+                    compareByDynamic(direction, NullableComparator.INT) { it.track },
                     compareBy(BasicComparator.SONG))
         }
 
@@ -377,48 +379,47 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             override val itemId: Int
                 get() = R.id.option_sort_date_added
 
-            override fun getSongComparator(isAscending: Boolean): Comparator<Song> =
+            override fun getSongComparator(direction: Direction): Comparator<Song> =
                 MultiComparator(
-                    compareByDynamic(isAscending) { it.dateAdded }, compareBy(BasicComparator.SONG))
+                    compareByDynamic(direction) { it.dateAdded }, compareBy(BasicComparator.SONG))
 
-            override fun getAlbumComparator(isAscending: Boolean): Comparator<Album> =
+            override fun getAlbumComparator(direction: Direction): Comparator<Album> =
                 MultiComparator(
-                    compareByDynamic(isAscending) { album -> album.dateAdded },
+                    compareByDynamic(direction) { album -> album.dateAdded },
                     compareBy(BasicComparator.ALBUM))
         }
 
         /**
-         * Utility function to create a [Comparator] in a dynamic way determined by [isAscending].
+         * Utility function to create a [Comparator] in a dynamic way determined by [direction].
-         * @param isAscending Whether to sort in ascending or descending order.
+         * @param direction The [Direction] to sort in.
          * @see compareBy
          * @see compareByDescending
          */
         protected inline fun <T : Music, K : Comparable<K>> compareByDynamic(
-            isAscending: Boolean,
+            direction: Direction,
             crossinline selector: (T) -> K
         ) =
-            if (isAscending) {
+            when (direction) {
-                compareBy(selector)
+                Direction.ASCENDING -> compareBy(selector)
-            } else {
+                Direction.DESCENDING -> compareByDescending(selector)
-                compareByDescending(selector)
             }
 
         /**
-         * Utility function to create a [Comparator] in a dynamic way determined by [isAscending]
+         * Utility function to create a [Comparator] in a dynamic way determined by [direction]
-         * @param isAscending Whether to sort in ascending or descending order.
+         * @param direction The [Direction] to sort in.
          * @param comparator A [Comparator] to wrap.
          * @return A new [Comparator] with the specified configuration.
          * @see compareBy
          * @see compareByDescending
          */
         protected fun <T : Music> compareByDynamic(
-            isAscending: Boolean,
+            direction: Direction,
             comparator: Comparator<in T>
-        ): Comparator<T> = compareByDynamic(isAscending, comparator) { it }
+        ): Comparator<T> = compareByDynamic(direction, comparator) { it }
 
         /**
-         * Utility function to create a [Comparator] a dynamic way determined by [isAscending]
+         * Utility function to create a [Comparator] a dynamic way determined by [direction]
-         * @param isAscending Whether to sort in ascending or descending order.
+         * @param direction The [Direction] to sort in.
          * @param comparator A [Comparator] to wrap.
          * @param selector Called to obtain a specific attribute to sort by.
          * @return A new [Comparator] with the specified configuration.
@@ -426,14 +427,13 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
          * @see compareByDescending
          */
         protected inline fun <T : Music, K> compareByDynamic(
-            isAscending: Boolean,
+            direction: Direction,
             comparator: Comparator<in K>,
             crossinline selector: (T) -> K
         ) =
-            if (isAscending) {
+            when (direction) {
-                compareBy(comparator, selector)
+                Direction.ASCENDING -> compareBy(comparator, selector)
-            } else {
+                Direction.DESCENDING -> compareByDescending(comparator, selector)
-                compareByDescending(comparator, selector)
             }
 
         /**
@@ -545,6 +545,8 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
                 val INT = NullableComparator<Int>()
                 /** A re-usable instance configured for [Long]s. */
                 val LONG = NullableComparator<Long>()
+                /** A re-usable instance configured for [Disc]s */
+                val DISC = NullableComparator<Disc>()
                 /** A re-usable instance configured for [Date.Range]s. */
                 val DATE_RANGE = NullableComparator<Date.Range>()
             }
@@ -593,6 +595,12 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
         }
     }
 
+    /** The direction to sort items in. */
+    enum class Direction {
+        ASCENDING,
+        DESCENDING
+    }
+
     companion object {
         /**
          * Convert a [Sort] integer representation into an instance.
@@ -604,9 +612,9 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
             // Sort's integer representation is formatted as AMMMM, where A is a bitflag
             // representing on if the mode is ascending or descending, and M is the integer
             // representation of the sort mode.
-            val isAscending = (intCode and 1) == 1
+            val direction = if ((intCode and 1) == 1) Direction.ASCENDING else Direction.DESCENDING
             val mode = Mode.fromIntCode(intCode.shr(1)) ?: return null
-            return Sort(mode, isAscending)
+            return Sort(mode, direction)
         }
     }
 }

app/src/main/java/org/oxycblt/auxio/list/adapter/ListDiffer.kt

@@ -63,7 +63,7 @@ interface ListDiffer<T, I> {
     class Async<T>(private val diffCallback: DiffUtil.ItemCallback<T>) :
         Factory<T, BasicListInstructions>() {
         override fun new(adapter: RecyclerView.Adapter<*>): ListDiffer<T, BasicListInstructions> =
-            RealAsyncListDiffer(AdapterListUpdateCallback(adapter), diffCallback)
+            AsyncListDifferImpl(AdapterListUpdateCallback(adapter), diffCallback)
     }
 
     /**
@@ -75,7 +75,7 @@ interface ListDiffer<T, I> {
     class Blocking<T>(private val diffCallback: DiffUtil.ItemCallback<T>) :
         Factory<T, BasicListInstructions>() {
         override fun new(adapter: RecyclerView.Adapter<*>): ListDiffer<T, BasicListInstructions> =
-            RealBlockingListDiffer(AdapterListUpdateCallback(adapter), diffCallback)
+            BlockingListDifferImpl(AdapterListUpdateCallback(adapter), diffCallback)
     }
 }
 
@@ -113,7 +113,7 @@ private abstract class BasicListDiffer<T> : ListDiffer<T, BasicListInstructions>
     protected abstract fun replaceList(newList: List<T>, onDone: () -> Unit)
 }
 
-private class RealAsyncListDiffer<T>(
+private class AsyncListDifferImpl<T>(
     updateCallback: ListUpdateCallback,
     diffCallback: DiffUtil.ItemCallback<T>
 ) : BasicListDiffer<T>() {
@@ -132,7 +132,7 @@ private class RealAsyncListDiffer<T>(
     }
 }
 
-private class RealBlockingListDiffer<T>(
+private class BlockingListDifferImpl<T>(
     private val updateCallback: ListUpdateCallback,
     private val diffCallback: DiffUtil.ItemCallback<T>
 ) : BasicListDiffer<T>() {

app/src/main/java/org/oxycblt/auxio/list/recycler/ViewHolders.kt

@@ -24,7 +24,7 @@ import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.ItemHeaderBinding
 import org.oxycblt.auxio.databinding.ItemParentBinding
 import org.oxycblt.auxio.databinding.ItemSongBinding
-import org.oxycblt.auxio.list.Header
+import org.oxycblt.auxio.list.BasicHeader
 import org.oxycblt.auxio.list.SelectableListListener
 import org.oxycblt.auxio.list.adapter.SelectionIndicatorAdapter
 import org.oxycblt.auxio.list.adapter.SimpleDiffCallback
@@ -49,7 +49,7 @@ class SongViewHolder private constructor(private val binding: ItemSongBinding) :
         listener.bind(song, this, menuButton = binding.songMenu)
         binding.songAlbumCover.bind(song)
         binding.songName.text = song.resolveName(binding.context)
-        binding.songInfo.text = song.resolveArtistContents(binding.context)
+        binding.songInfo.text = song.artists.resolveNames(binding.context)
     }
 
     override fun updatePlayingIndicator(isActive: Boolean, isPlaying: Boolean) {
@@ -76,7 +76,8 @@ class SongViewHolder private constructor(private val binding: ItemSongBinding) :
         val DIFF_CALLBACK =
             object : SimpleDiffCallback<Song>() {
                 override fun areContentsTheSame(oldItem: Song, newItem: Song) =
-                    oldItem.rawName == newItem.rawName && oldItem.areArtistContentsTheSame(newItem)
+                    oldItem.rawName == newItem.rawName &&
+                        oldItem.artists.areRawNamesTheSame(newItem.artists)
             }
     }
 }
@@ -96,7 +97,7 @@ class AlbumViewHolder private constructor(private val binding: ItemParentBinding
         listener.bind(album, this, menuButton = binding.parentMenu)
         binding.parentImage.bind(album)
         binding.parentName.text = album.resolveName(binding.context)
-        binding.parentInfo.text = album.resolveArtistContents(binding.context)
+        binding.parentInfo.text = album.artists.resolveNames(binding.context)
     }
 
     override fun updatePlayingIndicator(isActive: Boolean, isPlaying: Boolean) {
@@ -124,7 +125,7 @@ class AlbumViewHolder private constructor(private val binding: ItemParentBinding
             object : SimpleDiffCallback<Album>() {
                 override fun areContentsTheSame(oldItem: Album, newItem: Album) =
                     oldItem.rawName == newItem.rawName &&
-                        oldItem.areArtistContentsTheSame(newItem) &&
+                        oldItem.artists.areRawNamesTheSame(newItem.artists) &&
                         oldItem.releaseType == newItem.releaseType
             }
     }
@@ -241,23 +242,23 @@ class GenreViewHolder private constructor(private val binding: ItemParentBinding
 }
 
 /**
- * A [RecyclerView.ViewHolder] that displays a [Header]. Use [from] to create an instance.
+ * A [RecyclerView.ViewHolder] that displays a [BasicHeader]. Use [from] to create an instance.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class HeaderViewHolder private constructor(private val binding: ItemHeaderBinding) :
+class BasicHeaderViewHolder private constructor(private val binding: ItemHeaderBinding) :
     RecyclerView.ViewHolder(binding.root) {
     /**
      * Bind new data to this instance.
-     * @param header The new [Header] to bind.
+     * @param basicHeader The new [BasicHeader] to bind.
      */
-    fun bind(header: Header) {
+    fun bind(basicHeader: BasicHeader) {
-        logD(binding.context.getString(header.titleRes))
+        logD(binding.context.getString(basicHeader.titleRes))
-        binding.title.text = binding.context.getString(header.titleRes)
+        binding.title.text = binding.context.getString(basicHeader.titleRes)
     }
 
     companion object {
         /** Unique ID for this ViewHolder type. */
-        const val VIEW_TYPE = IntegerTable.VIEW_TYPE_HEADER
+        const val VIEW_TYPE = IntegerTable.VIEW_TYPE_BASIC_HEADER
 
         /**
          * Create a new instance.
@@ -265,13 +266,15 @@ class HeaderViewHolder private constructor(private val binding: ItemHeaderBindin
          * @return A new instance.
          */
         fun from(parent: View) =
-            HeaderViewHolder(ItemHeaderBinding.inflate(parent.context.inflater))
+            BasicHeaderViewHolder(ItemHeaderBinding.inflate(parent.context.inflater))
 
         /** A comparator that can be used with DiffUtil. */
         val DIFF_CALLBACK =
-            object : SimpleDiffCallback<Header>() {
+            object : SimpleDiffCallback<BasicHeader>() {
-                override fun areContentsTheSame(oldItem: Header, newItem: Header): Boolean =
+                override fun areContentsTheSame(
-                    oldItem.titleRes == newItem.titleRes
+                    oldItem: BasicHeader,
+                    newItem: BasicHeader
+                ): Boolean = oldItem.titleRes == newItem.titleRes
             }
     }
 }

app/src/main/java/org/oxycblt/auxio/list/selection/SelectionFragment.kt

@@ -20,12 +20,10 @@ package org.oxycblt.auxio.list.selection
 import android.os.Bundle
 import android.view.MenuItem
 import androidx.appcompat.widget.Toolbar
-import androidx.fragment.app.activityViewModels
 import androidx.viewbinding.ViewBinding
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.ui.ViewBindingFragment
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.showToast
 
 /**
@@ -34,8 +32,8 @@ import org.oxycblt.auxio.util.showToast
  */
 abstract class SelectionFragment<VB : ViewBinding> :
     ViewBindingFragment<VB>(), Toolbar.OnMenuItemClickListener {
-    protected val selectionModel: SelectionViewModel by activityViewModels()
+    protected abstract val selectionModel: SelectionViewModel
-    protected val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    protected abstract val playbackModel: PlaybackViewModel
 
     /**
      * Get the [SelectionToolbarOverlay] of the concrete Fragment to be automatically managed by

app/src/main/java/org/oxycblt/auxio/list/selection/SelectionViewModel.kt

@@ -18,26 +18,27 @@
 package org.oxycblt.auxio.list.selection
 
 import androidx.lifecycle.ViewModel
+import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.MusicStore
+import org.oxycblt.auxio.music.model.Library
-import org.oxycblt.auxio.music.library.Library
 
 /**
  * A [ViewModel] that manages the current selection.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class SelectionViewModel : ViewModel(), MusicStore.Listener {
+@HiltViewModel
-    private val musicStore = MusicStore.getInstance()
+class SelectionViewModel @Inject constructor(private val musicRepository: MusicRepository) :
-
+    ViewModel(), MusicRepository.Listener {
     private val _selected = MutableStateFlow(listOf<Music>())
     /** the currently selected items. These are ordered in earliest selected and latest selected. */
     val selected: StateFlow<List<Music>>
         get() = _selected
 
     init {
-        musicStore.addListener(this)
+        musicRepository.addListener(this)
     }
 
     override fun onLibraryChanged(library: Library?) {
@@ -60,7 +61,7 @@ class SelectionViewModel : ViewModel(), MusicStore.Listener {
 
     override fun onCleared() {
         super.onCleared()
-        musicStore.removeListener(this)
+        musicRepository.removeListener(this)
     }
 
     /**

app/src/main/java/org/oxycblt/auxio/music/AudioOnlyExtractors.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music
+
+import com.google.android.exoplayer2.extractor.ExtractorsFactory
+import com.google.android.exoplayer2.extractor.flac.FlacExtractor
+import com.google.android.exoplayer2.extractor.mkv.MatroskaExtractor
+import com.google.android.exoplayer2.extractor.mp3.Mp3Extractor
+import com.google.android.exoplayer2.extractor.mp4.Mp4Extractor
+import com.google.android.exoplayer2.extractor.ogg.OggExtractor
+import com.google.android.exoplayer2.extractor.ts.AdtsExtractor
+import com.google.android.exoplayer2.extractor.wav.WavExtractor
+
+/**
+ * A [ExtractorsFactory] that only provides audio containers to save APK space.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+object AudioOnlyExtractors : ExtractorsFactory {
+    override fun createExtractors() =
+        arrayOf(
+            FlacExtractor(),
+            WavExtractor(),
+            Mp4Extractor(),
+            OggExtractor(),
+            MatroskaExtractor(),
+            // Enable constant bitrate seeking so that certain MP3s/AACs are seekable
+            AdtsExtractor(AdtsExtractor.FLAG_ENABLE_CONSTANT_BITRATE_SEEKING),
+            Mp3Extractor(Mp3Extractor.FLAG_ENABLE_CONSTANT_BITRATE_SEEKING))
+}

app/src/main/java/org/oxycblt/auxio/music/Music.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021 Auxio Project
+ * Copyright (c) 2023 Auxio Project
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -15,50 +15,43 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-@file:Suppress("PropertyName", "FunctionName")
-
 package org.oxycblt.auxio.music
 
 import android.content.Context
+import android.net.Uri
 import android.os.Parcelable
-import androidx.annotation.VisibleForTesting
 import java.security.MessageDigest
 import java.text.CollationKey
-import java.text.Collator
 import java.util.UUID
 import kotlin.math.max
 import kotlinx.parcelize.IgnoredOnParcel
 import kotlinx.parcelize.Parcelize
-import org.oxycblt.auxio.R
 import org.oxycblt.auxio.list.Item
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.music.metadata.Date
-import org.oxycblt.auxio.music.parsing.parseId3GenreNames
+import org.oxycblt.auxio.music.metadata.Disc
-import org.oxycblt.auxio.music.parsing.parseMultiValue
+import org.oxycblt.auxio.music.metadata.ReleaseType
-import org.oxycblt.auxio.music.storage.*
+import org.oxycblt.auxio.music.storage.MimeType
-import org.oxycblt.auxio.music.tags.Date
+import org.oxycblt.auxio.music.storage.Path
-import org.oxycblt.auxio.music.tags.ReleaseType
+import org.oxycblt.auxio.util.concatLocalized
-import org.oxycblt.auxio.util.nonZeroOrNull
+import org.oxycblt.auxio.util.toUuidOrNull
-import org.oxycblt.auxio.util.unlikelyToBeNull
-
-// --- MUSIC MODELS ---
 
 /**
  * Abstract music data. This contains universal information about all concrete music
  * implementations, such as identification information and names.
  * @author Alexander Capehart (OxygenCobalt)
  */
-sealed class Music : Item {
+sealed interface Music : Item {
     /**
      * A unique identifier for this music item.
      * @see UID
      */
-    abstract val uid: UID
+    val uid: UID
 
     /**
      * The raw name of this item as it was extracted from the file-system. Will be null if the
      * item's name is unknown. When showing this item in a UI, avoid this in favor of [resolveName].
      */
-    abstract val rawName: String?
+    val rawName: String?
 
     /**
      * Returns a name suitable for use in the app UI. This should be favored over [rawName] in
@@ -67,14 +60,14 @@ sealed class Music : Item {
      * @return A human-readable string representing the name of this music. In the case that the
      * item does not have a name, an analogous "Unknown X" name is returned.
      */
-    abstract fun resolveName(context: Context): String
+    fun resolveName(context: Context): String
 
     /**
      * The raw sort name of this item as it was extracted from the file-system. This can be used not
      * only when sorting music, but also trying to locate music based on a fuzzy search by the user.
      * Will be null if the item has no known sort name.
      */
-    abstract val rawSortName: String?
+    val rawSortName: String?
 
     /**
      * A [CollationKey] derived from [rawName] and [rawSortName] that can be used to sort items in a
@@ -85,62 +78,7 @@ sealed class Music : Item {
      * - If the string begins with an article, such as "the", it will be stripped, as is usually
      * convention for sorting media. This is not internationalized.
      */
-    abstract val collationKey: CollationKey?
+    val collationKey: CollationKey?
-
-    /**
-     * Finalize this item once the music library has been fully constructed. This is where any final
-     * ordering or sanity checking should occur. **This function is internal to the music package.
-     * Do not use it elsewhere.**
-     */
-    abstract fun _finalize()
-
-    /**
-     * Provided implementation to create a [CollationKey] in the way described by [collationKey].
-     * This should be used in all overrides of all [CollationKey].
-     * @return A [CollationKey] that follows the specification described by [collationKey].
-     */
-    protected fun makeCollationKeyImpl(): CollationKey? {
-        val sortName =
-            (rawSortName ?: rawName)?.run {
-                when {
-                    length > 5 && startsWith("the ", ignoreCase = true) -> substring(4)
-                    length > 4 && startsWith("an ", ignoreCase = true) -> substring(3)
-                    length > 3 && startsWith("a ", ignoreCase = true) -> substring(2)
-                    else -> this
-                }
-            }
-
-        return COLLATOR.getCollationKey(sortName)
-    }
-
-    /**
-     * Join a list of [Music]'s resolved names into a string in a localized manner, using
-     * [R.string.fmt_list].
-     * @param context [Context] required to obtain localized formatting.
-     * @param values The list of [Music] to format.
-     * @return A single string consisting of the values delimited by a localized separator.
-     */
-    protected fun resolveNames(context: Context, values: List<Music>): String {
-        if (values.isEmpty()) {
-            // Nothing to do.
-            return ""
-        }
-
-        var joined = values.first().resolveName(context)
-        for (i in 1..values.lastIndex) {
-            // Chain all previous values with the next value in the list with another delimiter.
-            joined = context.getString(R.string.fmt_list, joined, values[i].resolveName(context))
-        }
-        return joined
-    }
-
-    // Note: We solely use the UID in comparisons so that certain items that differ in all
-    // but UID are treated differently.
-
-    override fun hashCode() = uid.hashCode()
-
-    override fun equals(other: Any?) =
-        other is Music && javaClass == other.javaClass && uid == other.uid
 
     /**
      * A unique identifier for a piece of music.
@@ -192,6 +130,7 @@ sealed class Music : Item {
         private enum class Format(val namespace: String) {
             /** @see auxio */
             AUXIO("org.oxycblt.auxio"),
+
             /** @see musicBrainz */
             MUSICBRAINZ("org.musicbrainz")
         }
@@ -281,799 +220,156 @@ sealed class Music : Item {
             }
         }
     }
-
-    private companion object {
-        /** Cached collator instance re-used with [makeCollationKeyImpl]. */
-        val COLLATOR: Collator = Collator.getInstance().apply { strength = Collator.PRIMARY }
-    }
 }
 
 /**
  * An abstract grouping of [Song]s and other [Music] data.
  * @author Alexander Capehart (OxygenCobalt)
  */
-sealed class MusicParent : Music() {
+sealed interface MusicParent : Music {
-    /** The [Song]s in this this group. */
+    /** The child [Song]s of this [MusicParent]. */
-    abstract val songs: List<Song>
+    val songs: List<Song>
-
-    // Note: Append song contents to MusicParent equality so that Groups with
-    // the same UID but different contents are not equal.
-
-    override fun hashCode() = 31 * uid.hashCode() + songs.hashCode()
-
-    override fun equals(other: Any?) =
-        other is MusicParent &&
-            javaClass == other.javaClass &&
-            uid == other.uid &&
-            songs == other.songs
 }
 
 /**
- * A song. Perhaps the foundation of the entirety of Auxio.
+ * A song.
- * @param raw The [Song.Raw] to derive the member data from.
- * @param musicSettings [MusicSettings] to perform further user-configured parsing.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class Song constructor(raw: Raw, musicSettings: MusicSettings) : Music() {
+interface Song : Music {
-    override val uid =
-    // Attempt to use a MusicBrainz ID first before falling back to a hashed UID.
-    raw.musicBrainzId?.toUuidOrNull()?.let { UID.musicBrainz(MusicMode.SONGS, it) }
-            ?: UID.auxio(MusicMode.SONGS) {
-                // Song UIDs are based on the raw data without parsing so that they remain
-                // consistent across music setting changes. Parents are not held up to the
-                // same standard since grouping is already inherently linked to settings.
-                update(raw.name)
-                update(raw.albumName)
-                update(raw.date)
-
-                update(raw.track)
-                update(raw.disc)
-
-                update(raw.artistNames)
-                update(raw.albumArtistNames)
-            }
-    override val rawName = requireNotNull(raw.name) { "Invalid raw: No title" }
-    override val rawSortName = raw.sortName
-    override val collationKey = makeCollationKeyImpl()
-    override fun resolveName(context: Context) = rawName
-
     /** The track number. Will be null if no valid track number was present in the metadata. */
-    val track = raw.track
+    val track: Int?
-
+    /** The [Disc] number. Will be null if no valid disc number was present in the metadata. */
-    /** The disc number. Will be null if no valid disc number was present in the metadata. */
+    val disc: Disc?
-    val disc = raw.disc
-
     /** The release [Date]. Will be null if no valid date was present in the metadata. */
-    val date = raw.date
+    val date: Date?
-
     /**
      * The URI to the audio file that this instance was created from. This can be used to access the
      * audio file in a way that is scoped-storage-safe.
      */
-    val uri = requireNotNull(raw.mediaStoreId) { "Invalid raw: No id" }.toAudioUri()
+    val uri: Uri
-
     /**
      * The [Path] to this audio file. This is only intended for display, [uri] should be favored
      * instead for accessing the audio file.
      */
-    val path =
+    val path: Path
-        Path(
-            name = requireNotNull(raw.fileName) { "Invalid raw: No display name" },
-            parent = requireNotNull(raw.directory) { "Invalid raw: No parent directory" })
-
     /** The [MimeType] of the audio file. Only intended for display. */
-    val mimeType =
+    val mimeType: MimeType
-        MimeType(
-            fromExtension = requireNotNull(raw.extensionMimeType) { "Invalid raw: No mime type" },
-            fromFormat = null)
-
     /** The size of the audio file, in bytes. */
-    val size = requireNotNull(raw.size) { "Invalid raw: No size" }
+    val size: Long
-
     /** The duration of the audio file, in milliseconds. */
-    val durationMs = requireNotNull(raw.durationMs) { "Invalid raw: No duration" }
+    val durationMs: Long
-
     /** The date the audio file was added to the device, as a unix epoch timestamp. */
-    val dateAdded = requireNotNull(raw.dateAdded) { "Invalid raw: No date added" }
+    val dateAdded: Long
-
-    private var _album: Album? = null
     /**
      * The parent [Album]. If the metadata did not specify an album, it's parent directory is used
      * instead.
      */
     val album: Album
-        get() = unlikelyToBeNull(_album)
-
-    private val artistMusicBrainzIds = raw.artistMusicBrainzIds.parseMultiValue(musicSettings)
-    private val artistNames = raw.artistNames.parseMultiValue(musicSettings)
-    private val artistSortNames = raw.artistSortNames.parseMultiValue(musicSettings)
-    private val rawArtists =
-        artistNames.mapIndexed { i, name ->
-            Artist.Raw(
-                artistMusicBrainzIds.getOrNull(i)?.toUuidOrNull(),
-                name,
-                artistSortNames.getOrNull(i))
-        }
-
-    private val albumArtistMusicBrainzIds =
-        raw.albumArtistMusicBrainzIds.parseMultiValue(musicSettings)
-    private val albumArtistNames = raw.albumArtistNames.parseMultiValue(musicSettings)
-    private val albumArtistSortNames = raw.albumArtistSortNames.parseMultiValue(musicSettings)
-    private val rawAlbumArtists =
-        albumArtistNames.mapIndexed { i, name ->
-            Artist.Raw(
-                albumArtistMusicBrainzIds.getOrNull(i)?.toUuidOrNull(),
-                name,
-                albumArtistSortNames.getOrNull(i))
-        }
-
-    private val _artists = mutableListOf<Artist>()
     /**
      * The parent [Artist]s of this [Song]. Is often one, but there can be multiple if more than one
      * [Artist] name was specified in the metadata. Unliked [Album], artists are prioritized for
      * this field.
      */
     val artists: List<Artist>
-        get() = _artists
-
-    /**
-     * Resolves one or more [Artist]s into a single piece of human-readable names.
-     * @param context [Context] required for [resolveName]. formatter.
-     */
-    fun resolveArtistContents(context: Context) = resolveNames(context, artists)
-
-    /**
-     * Checks if the [Artist] *display* of this [Song] and another [Song] are equal. This will only
-     * compare surface-level names, and not [Music.UID]s.
-     * @param other The [Song] to compare to.
-     * @return True if the [Artist] displays are equal, false otherwise
-     */
-    fun areArtistContentsTheSame(other: Song): Boolean {
-        for (i in 0 until max(artists.size, other.artists.size)) {
-            val a = artists.getOrNull(i) ?: return false
-            val b = other.artists.getOrNull(i) ?: return false
-            if (a.rawName != b.rawName) {
-                return false
-            }
-        }
-
-        return true
-    }
-
-    private val _genres = mutableListOf<Genre>()
     /**
      * The parent [Genre]s of this [Song]. Is often one, but there can be multiple if more than one
      * [Genre] name was specified in the metadata.
      */
     val genres: List<Genre>
-        get() = _genres
-
-    /**
-     * Resolves one or more [Genre]s into a single piece human-readable names.
-     * @param context [Context] required for [resolveName].
-     */
-    fun resolveGenreContents(context: Context) = resolveNames(context, genres)
-
-    // --- INTERNAL FIELDS ---
-
-    /**
-     * The [Album.Raw] instances collated by the [Song]. This can be used to group [Song]s into an
-     * [Album]. **This is only meant for use within the music package.**
-     */
-    val _rawAlbum =
-        Album.Raw(
-            mediaStoreId = requireNotNull(raw.albumMediaStoreId) { "Invalid raw: No album id" },
-            musicBrainzId = raw.albumMusicBrainzId?.toUuidOrNull(),
-            name = requireNotNull(raw.albumName) { "Invalid raw: No album name" },
-            sortName = raw.albumSortName,
-            releaseType = ReleaseType.parse(raw.releaseTypes.parseMultiValue(musicSettings)),
-            rawArtists =
-                rawAlbumArtists.ifEmpty { rawArtists }.ifEmpty { listOf(Artist.Raw(null, null)) })
-
-    /**
-     * The [Artist.Raw] instances collated by the [Song]. The artists of the song take priority,
-     * followed by the album artists. If there are no artists, this field will be a single "unknown"
-     * [Artist.Raw]. This can be used to group up [Song]s into an [Artist]. **This is only meant for
-     * use within the music package.**
-     */
-    val _rawArtists = rawArtists.ifEmpty { rawAlbumArtists }.ifEmpty { listOf(Artist.Raw()) }
-
-    /**
-     * The [Genre.Raw] instances collated by the [Song]. This can be used to group up [Song]s into a
-     * [Genre]. ID3v2 Genre names are automatically converted to their resolved names. **This is
-     * only meant for use within the music package.**
-     */
-    val _rawGenres =
-        raw.genreNames
-            .parseId3GenreNames(musicSettings)
-            .map { Genre.Raw(it) }
-            .ifEmpty { listOf(Genre.Raw()) }
-
-    /**
-     * Links this [Song] with a parent [Album].
-     * @param album The parent [Album] to link to. **This is only meant for use within the music
-     * package.**
-     */
-    fun _link(album: Album) {
-        _album = album
-    }
-
-    /**
-     * Links this [Song] with a parent [Artist].
-     * @param artist The parent [Artist] to link to. **This is only meant for use within the music
-     * package.**
-     */
-    fun _link(artist: Artist) {
-        _artists.add(artist)
-    }
-
-    /**
-     * Links this [Song] with a parent [Genre].
-     * @param genre The parent [Genre] to link to. **This is only meant for use within the music
-     * package.**
-     */
-    fun _link(genre: Genre) {
-        _genres.add(genre)
-    }
-
-    override fun _finalize() {
-        checkNotNull(_album) { "Malformed song: No album" }
-
-        check(_artists.isNotEmpty()) { "Malformed song: No artists" }
-        for (i in _artists.indices) {
-            // Non-destructively reorder the linked artists so that they align with
-            // the artist ordering within the song metadata.
-            val newIdx = _artists[i]._getOriginalPositionIn(_rawArtists)
-            val other = _artists[newIdx]
-            _artists[newIdx] = _artists[i]
-            _artists[i] = other
-        }
-
-        check(_genres.isNotEmpty()) { "Malformed song: No genres" }
-        for (i in _genres.indices) {
-            // Non-destructively reorder the linked genres so that they align with
-            // the genre ordering within the song metadata.
-            val newIdx = _genres[i]._getOriginalPositionIn(_rawGenres)
-            val other = _genres[newIdx]
-            _genres[newIdx] = _genres[i]
-            _genres[i] = other
-        }
-    }
-
-    /**
-     * Raw information about a [Song] obtained from the filesystem/Extractor instances. **This is
-     * only meant for use within the music package.**
-     */
-    class Raw
-    constructor(
-        /**
-         * The ID of the [Song]'s audio file, obtained from MediaStore. Note that this ID is highly
-         * unstable and should only be used for accessing the audio file.
-         */
-        var mediaStoreId: Long? = null,
-        /** @see Song.dateAdded */
-        var dateAdded: Long? = null,
-        /** The latest date the [Song]'s audio file was modified, as a unix epoch timestamp. */
-        var dateModified: Long? = null,
-        /** @see Song.path */
-        var fileName: String? = null,
-        /** @see Song.path */
-        var directory: Directory? = null,
-        /** @see Song.size */
-        var size: Long? = null,
-        /** @see Song.durationMs */
-        var durationMs: Long? = null,
-        /** @see Song.mimeType */
-        var extensionMimeType: String? = null,
-        /** @see Music.UID */
-        var musicBrainzId: String? = null,
-        /** @see Music.rawName */
-        var name: String? = null,
-        /** @see Music.rawSortName */
-        var sortName: String? = null,
-        /** @see Song.track */
-        var track: Int? = null,
-        /** @see Song.disc */
-        var disc: Int? = null,
-        /** @see Song.date */
-        var date: Date? = null,
-        /** @see Album.Raw.mediaStoreId */
-        var albumMediaStoreId: Long? = null,
-        /** @see Album.Raw.musicBrainzId */
-        var albumMusicBrainzId: String? = null,
-        /** @see Album.Raw.name */
-        var albumName: String? = null,
-        /** @see Album.Raw.sortName */
-        var albumSortName: String? = null,
-        /** @see Album.Raw.releaseType */
-        var releaseTypes: List<String> = listOf(),
-        /** @see Artist.Raw.musicBrainzId */
-        var artistMusicBrainzIds: List<String> = listOf(),
-        /** @see Artist.Raw.name */
-        var artistNames: List<String> = listOf(),
-        /** @see Artist.Raw.sortName */
-        var artistSortNames: List<String> = listOf(),
-        /** @see Artist.Raw.musicBrainzId */
-        var albumArtistMusicBrainzIds: List<String> = listOf(),
-        /** @see Artist.Raw.name */
-        var albumArtistNames: List<String> = listOf(),
-        /** @see Artist.Raw.sortName */
-        var albumArtistSortNames: List<String> = listOf(),
-        /** @see Genre.Raw.name */
-        var genreNames: List<String> = listOf()
-    )
 }
 
 /**
  * An abstract release group. While it may be called an album, it encompasses other types of
  * releases like singles, EPs, and compilations.
- * @param raw The [Album.Raw] to derive the member data from.
- * @param songs The [Song]s that are a part of this [Album]. These items will be linked to this
- * [Album].
  * @author Alexander Capehart (OxygenCobalt)
  */
-class Album constructor(raw: Raw, override val songs: List<Song>) : MusicParent() {
+interface Album : MusicParent {
-    override val uid =
-    // Attempt to use a MusicBrainz ID first before falling back to a hashed UID.
-    raw.musicBrainzId?.let { UID.musicBrainz(MusicMode.ALBUMS, it) }
-            ?: UID.auxio(MusicMode.ALBUMS) {
-                // Hash based on only names despite the presence of a date to increase stability.
-                // I don't know if there is any situation where an artist will have two albums with
-                // the exact same name, but if there is, I would love to know.
-                update(raw.name)
-                update(raw.rawArtists.map { it.name })
-            }
-    override val rawName = raw.name
-    override val rawSortName = raw.sortName
-    override val collationKey = makeCollationKeyImpl()
-    override fun resolveName(context: Context) = rawName
-
     /** The [Date.Range] that [Song]s in the [Album] were released. */
-    val dates = Date.Range.from(songs.mapNotNull { it.date })
+    val dates: Date.Range?
-
     /**
      * The [ReleaseType] of this album, signifying the type of release it actually is. Defaults to
      * [ReleaseType.Album].
      */
-    val releaseType = raw.releaseType ?: ReleaseType.Album(null)
+    val releaseType: ReleaseType
     /**
      * The URI to a MediaStore-provided album cover. These images will be fast to load, but at the
      * cost of image quality.
      */
-    val coverUri = raw.mediaStoreId.toCoverUri()
+    val coverUri: Uri
-
     /** The duration of all songs in the album, in milliseconds. */
     val durationMs: Long
-
     /** The earliest date a song in this album was added, as a unix epoch timestamp. */
     val dateAdded: Long
-
-    init {
-        var totalDuration: Long = 0
-        var earliestDateAdded: Long = Long.MAX_VALUE
-
-        // Do linking and value generation in the same loop for efficiency.
-        for (song in songs) {
-            song._link(this)
-            if (song.dateAdded < earliestDateAdded) {
-                earliestDateAdded = song.dateAdded
-            }
-            totalDuration += song.durationMs
-        }
-
-        durationMs = totalDuration
-        dateAdded = earliestDateAdded
-    }
-
-    private val _artists = mutableListOf<Artist>()
     /**
      * The parent [Artist]s of this [Album]. Is often one, but there can be multiple if more than
      * one [Artist] name was specified in the metadata of the [Song]'s. Unlike [Song], album artists
      * are prioritized for this field.
      */
     val artists: List<Artist>
-        get() = _artists
-
-    /**
-     * Resolves one or more [Artist]s into a single piece of human-readable names.
-     * @param context [Context] required for [resolveName].
-     */
-    fun resolveArtistContents(context: Context) = resolveNames(context, artists)
-
-    /**
-     * Checks if the [Artist] *display* of this [Album] and another [Album] are equal. This will
-     * only compare surface-level names, and not [Music.UID]s.
-     * @param other The [Album] to compare to.
-     * @return True if the [Artist] displays are equal, false otherwise
-     */
-    fun areArtistContentsTheSame(other: Album): Boolean {
-        for (i in 0 until max(artists.size, other.artists.size)) {
-            val a = artists.getOrNull(i) ?: return false
-            val b = other.artists.getOrNull(i) ?: return false
-            if (a.rawName != b.rawName) {
-                return false
-            }
-        }
-
-        return true
-    }
-
-    // --- INTERNAL FIELDS ---
-
-    /**
-     * The [Artist.Raw] instances collated by the [Album]. The album artists of the song take
-     * priority, followed by the artists. If there are no artists, this field will be a single
-     * "unknown" [Artist.Raw]. This can be used to group up [Album]s into an [Artist]. **This is
-     * only meant for use within the music package.**
-     */
-    val _rawArtists = raw.rawArtists
-
-    /**
-     * Links this [Album] with a parent [Artist].
-     * @param artist The parent [Artist] to link to. **This is only meant for use within the music
-     * package.**
-     */
-    fun _link(artist: Artist) {
-        _artists.add(artist)
-    }
-
-    override fun _finalize() {
-        check(songs.isNotEmpty()) { "Malformed album: Empty" }
-        check(_artists.isNotEmpty()) { "Malformed album: No artists" }
-        for (i in _artists.indices) {
-            // Non-destructively reorder the linked artists so that they align with
-            // the artist ordering within the song metadata.
-            val newIdx = _artists[i]._getOriginalPositionIn(_rawArtists)
-            val other = _artists[newIdx]
-            _artists[newIdx] = _artists[i]
-            _artists[i] = other
-        }
-    }
-
-    /**
-     * Raw information about an [Album] obtained from the component [Song] instances. **This is only
-     * meant for use within the music package.**
-     */
-    class Raw(
-        /**
-         * The ID of the [Album]'s grouping, obtained from MediaStore. Note that this ID is highly
-         * unstable and should only be used for accessing the system-provided cover art.
-         */
-        val mediaStoreId: Long,
-        /** @see Music.uid */
-        val musicBrainzId: UUID?,
-        /** @see Music.rawName */
-        val name: String,
-        /** @see Music.rawSortName */
-        val sortName: String?,
-        /** @see Album.releaseType */
-        val releaseType: ReleaseType?,
-        /** @see Artist.Raw.name */
-        val rawArtists: List<Artist.Raw>
-    ) {
-        // Albums are grouped as follows:
-        // - If we have a MusicBrainz ID, only group by it. This allows different Albums with the
-        // same name to be differentiated, which is common in large libraries.
-        // - If we do not have a MusicBrainz ID, compare by the lowercase album name and lowercase
-        // artist name. This allows for case-insensitive artist/album grouping, which can be common
-        // for albums/artists that have different naming (ex. "RAMMSTEIN" vs. "Rammstein").
-
-        // Cache the hash-code for HashMap efficiency.
-        private val hashCode =
-            musicBrainzId?.hashCode() ?: (31 * name.lowercase().hashCode() + rawArtists.hashCode())
-
-        override fun hashCode() = hashCode
-
-        override fun equals(other: Any?) =
-            other is Raw &&
-                when {
-                    musicBrainzId != null && other.musicBrainzId != null ->
-                        musicBrainzId == other.musicBrainzId
-                    musicBrainzId == null && other.musicBrainzId == null ->
-                        name.equals(other.name, true) && rawArtists == other.rawArtists
-                    else -> false
-                }
-    }
 }
 
 /**
  * An abstract artist. These are actually a combination of the artist and album artist tags from
  * within the library, derived from [Song]s and [Album]s respectively.
- * @param raw The [Artist.Raw] to derive the member data from.
- * @param songAlbums A list of the [Song]s and [Album]s that are a part of this [Artist], either
- * through artist or album artist tags. Providing [Song]s to the artist is optional. These instances
- * will be linked to this [Artist].
  * @author Alexander Capehart (OxygenCobalt)
  */
-class Artist constructor(private val raw: Raw, songAlbums: List<Music>) : MusicParent() {
+interface Artist : MusicParent {
-    override val uid =
-    // Attempt to use a MusicBrainz ID first before falling back to a hashed UID.
-    raw.musicBrainzId?.let { UID.musicBrainz(MusicMode.ARTISTS, it) }
-            ?: UID.auxio(MusicMode.ARTISTS) { update(raw.name) }
-    override val rawName = raw.name
-    override val rawSortName = raw.sortName
-    override val collationKey = makeCollationKeyImpl()
-    override fun resolveName(context: Context) = rawName ?: context.getString(R.string.def_artist)
-    override val songs: List<Song>
-
     /**
      * All of the [Album]s this artist is credited to. Note that any [Song] credited to this artist
      * will have it's [Album] considered to be "indirectly" linked to this [Artist], and thus
      * included in this list.
      */
     val albums: List<Album>
-
     /**
      * The duration of all [Song]s in the artist, in milliseconds. Will be null if there are no
      * songs.
      */
     val durationMs: Long?
-
     /**
      * Whether this artist is considered a "collaborator", i.e it is not directly credited on any
      * [Album].
      */
     val isCollaborator: Boolean
-
+    /** The [Genre]s of this artist. */
-    init {
+    val genres: List<Genre>
-        val distinctSongs = mutableSetOf<Song>()
-        val distinctAlbums = mutableSetOf<Album>()
-
-        var noAlbums = true
-
-        for (music in songAlbums) {
-            when (music) {
-                is Song -> {
-                    music._link(this)
-                    distinctSongs.add(music)
-                    distinctAlbums.add(music.album)
-                }
-                is Album -> {
-                    music._link(this)
-                    distinctAlbums.add(music)
-                    noAlbums = false
-                }
-                else -> error("Unexpected input music ${music::class.simpleName}")
-            }
-        }
-
-        songs = distinctSongs.toList()
-        albums = distinctAlbums.toList()
-        durationMs = songs.sumOf { it.durationMs }.nonZeroOrNull()
-        isCollaborator = noAlbums
-    }
-
-    private lateinit var genres: List<Genre>
-
-    /**
-     * Resolves one or more [Genre]s into a single piece of human-readable names.
-     * @param context [Context] required for [resolveName].
-     */
-    fun resolveGenreContents(context: Context) = resolveNames(context, genres)
-
-    /**
-     * Checks if the [Genre] *display* of this [Artist] and another [Artist] are equal. This will
-     * only compare surface-level names, and not [Music.UID]s.
-     * @param other The [Artist] to compare to.
-     * @return True if the [Genre] displays are equal, false otherwise
-     */
-    fun areGenreContentsTheSame(other: Artist): Boolean {
-        for (i in 0 until max(genres.size, other.genres.size)) {
-            val a = genres.getOrNull(i) ?: return false
-            val b = other.genres.getOrNull(i) ?: return false
-            if (a.rawName != b.rawName) {
-                return false
-            }
-        }
-
-        return true
-    }
-
-    // --- INTERNAL METHODS ---
-
-    /**
-     * Returns the original position of this [Artist]'s [Artist.Raw] within the given [Artist.Raw]
-     * list. This can be used to create a consistent ordering within child [Artist] lists based on
-     * the original tag order.
-     * @param rawArtists The [Artist.Raw] instances to check. It is assumed that this [Artist]'s
-     * [Artist.Raw] will be within the list.
-     * @return The index of the [Artist]'s [Artist.Raw] within the list. **This is only meant for
-     * use within the music package.**
-     */
-    fun _getOriginalPositionIn(rawArtists: List<Raw>) = rawArtists.indexOf(raw)
-
-    override fun _finalize() {
-        check(songs.isNotEmpty() || albums.isNotEmpty()) { "Malformed artist: Empty" }
-        genres =
-            Sort(Sort.Mode.ByName, true)
-                .genres(songs.flatMapTo(mutableSetOf()) { it.genres })
-                .sortedByDescending { genre -> songs.count { it.genres.contains(genre) } }
-    }
-
-    /**
-     * Raw information about an [Artist] obtained from the component [Song] and [Album] instances.
-     * **This is only meant for use within the music package.**
-     */
-    class Raw(
-        /** @see Music.UID */
-        val musicBrainzId: UUID? = null,
-        /** @see Music.rawName */
-        val name: String? = null,
-        /** @see Music.rawSortName */
-        val sortName: String? = null
-    ) {
-        // Artists are grouped as follows:
-        // - If we have a MusicBrainz ID, only group by it. This allows different Artists with the
-        // same name to be differentiated, which is common in large libraries.
-        // - If we do not have a MusicBrainz ID, compare by the lowercase name. This allows artist
-        // grouping to be case-insensitive.
-
-        // Cache the hashCode for HashMap efficiency.
-        private val hashCode = musicBrainzId?.hashCode() ?: name?.lowercase().hashCode()
-
-        // Compare names and MusicBrainz IDs in order to differentiate artists with the
-        // same name in large libraries.
-
-        override fun hashCode() = hashCode
-
-        override fun equals(other: Any?) =
-            other is Raw &&
-                when {
-                    musicBrainzId != null && other.musicBrainzId != null ->
-                        musicBrainzId == other.musicBrainzId
-                    musicBrainzId == null && other.musicBrainzId == null ->
-                        when {
-                            name != null && other.name != null -> name.equals(other.name, true)
-                            name == null && other.name == null -> true
-                            else -> false
-                        }
-                    else -> false
-                }
-    }
 }
 
 /**
- * A genre of [Song]s.
+ * A genre.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class Genre constructor(private val raw: Raw, override val songs: List<Song>) : MusicParent() {
+interface Genre : MusicParent {
-    override val uid = UID.auxio(MusicMode.GENRES) { update(raw.name) }
-    override val rawName = raw.name
-    override val rawSortName = rawName
-    override val collationKey = makeCollationKeyImpl()
-    override fun resolveName(context: Context) = rawName ?: context.getString(R.string.def_genre)
-
     /** The albums indirectly linked to by the [Song]s of this [Genre]. */
     val albums: List<Album>
-
     /** The artists indirectly linked to by the [Artist]s of this [Genre]. */
     val artists: List<Artist>
-
     /** The total duration of the songs in this genre, in milliseconds. */
     val durationMs: Long
+}
 
-    init {
+/**
-        val distinctAlbums = mutableSetOf<Album>()
+ * Run [Music.resolveName] on each instance in the given list and concatenate them into a [String]
-        val distinctArtists = mutableSetOf<Artist>()
+ * in a localized manner.
-        var totalDuration = 0L
+ * @param context [Context] required
+ * @return A concatenated string.
+ */
+fun <T : Music> List<T>.resolveNames(context: Context) =
+    concatLocalized(context) { it.resolveName(context) }
 
-        for (song in songs) {
+/**
-            song._link(this)
+ * Returns if [Music.rawName] matches for each item in a list. Useful for scenarios where the
-            distinctAlbums.add(song.album)
+ * display information of an item must be compared without a context.
-            distinctArtists.addAll(song.artists)
+ * @param other The list of items to compare to.
-            totalDuration += song.durationMs
+ * @return True if they are the same (by [Music.rawName]), false otherwise.
+ */
+fun <T : Music> List<T>.areRawNamesTheSame(other: List<T>): Boolean {
+    for (i in 0 until max(size, other.size)) {
+        val a = getOrNull(i) ?: return false
+        val b = other.getOrNull(i) ?: return false
+        if (a.rawName != b.rawName) {
+            return false
         }
-
-        albums =
-            Sort(Sort.Mode.ByName, true).albums(distinctAlbums).sortedByDescending { album ->
-                album.songs.count { it.genres.contains(this) }
-            }
-        artists = Sort(Sort.Mode.ByName, true).artists(distinctArtists)
-        durationMs = totalDuration
     }
 
-    // --- INTERNAL METHODS ---
+    return true
-
-    /**
-     * Returns the original position of this [Genre]'s [Genre.Raw] within the given [Genre.Raw]
-     * list. This can be used to create a consistent ordering within child [Genre] lists based on
-     * the original tag order.
-     * @param rawGenres The [Genre.Raw] instances to check. It is assumed that this [Genre]'s
-     * [Genre.Raw] will be within the list.
-     * @return The index of the [Genre]'s [Genre.Raw] within the list. **This is only meant for use
-     * within the music package.**
-     */
-    fun _getOriginalPositionIn(rawGenres: List<Raw>) = rawGenres.indexOf(raw)
-
-    override fun _finalize() {
-        check(songs.isNotEmpty()) { "Malformed genre: Empty" }
-    }
-
-    /**
-     * Raw information about a [Genre] obtained from the component [Song] instances. **This is only
-     * meant for use within the music package.**
-     */
-    class Raw(
-        /** @see Music.rawName */
-        val name: String? = null
-    ) {
-        // Only group by the lowercase genre name. This allows Genre grouping to be
-        // case-insensitive, which may be helpful in some libraries with different ways of
-        // formatting genres.
-
-        // Cache the hashCode for HashMap efficiency.
-        private val hashCode = name?.lowercase().hashCode()
-
-        override fun hashCode() = hashCode
-
-        override fun equals(other: Any?) =
-            other is Raw &&
-                when {
-                    name != null && other.name != null -> name.equals(other.name, true)
-                    name == null && other.name == null -> true
-                    else -> false
-                }
-    }
-}
-
-// --- MUSIC UID CREATION UTILITIES ---
-
-/**
- * Convert a [String] to a [UUID].
- * @return A [UUID] converted from the [String] value, or null if the value was not valid.
- * @see UUID.fromString
- */
-private fun String.toUuidOrNull(): UUID? =
-    try {
-        UUID.fromString(this)
-    } catch (e: IllegalArgumentException) {
-        null
-    }
-
-/**
- * Update a [MessageDigest] with a lowercase [String].
- * @param string The [String] to hash. If null, it will not be hashed.
- */
-@VisibleForTesting
-fun MessageDigest.update(string: String?) {
-    if (string != null) {
-        update(string.lowercase().toByteArray())
-    } else {
-        update(0)
-    }
-}
-
-/**
- * Update a [MessageDigest] with the string representation of a [Date].
- * @param date The [Date] to hash. If null, nothing will be done.
- */
-@VisibleForTesting
-fun MessageDigest.update(date: Date?) {
-    if (date != null) {
-        update(date.toString().toByteArray())
-    } else {
-        update(0)
-    }
-}
-
-/**
- * Update a [MessageDigest] with the lowercase versions of all of the input [String]s.
- * @param strings The [String]s to hash. If a [String] is null, it will not be hashed.
- */
-@VisibleForTesting
-fun MessageDigest.update(strings: List<String?>) {
-    strings.forEach(::update)
-}
-
-/**
- * Update a [MessageDigest] with the little-endian bytes of a [Int].
- * @param n The [Int] to write. If null, nothing will be done.
- */
-@VisibleForTesting
-fun MessageDigest.update(n: Int?) {
-    if (n != null) {
-        update(byteArrayOf(n.toByte(), n.shr(8).toByte(), n.shr(16).toByte(), n.shr(24).toByte()))
-    } else {
-        update(0)
-    }
 }

app/src/main/java/org/oxycblt/auxio/music/MusicModule.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music
+
+import dagger.Binds
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+import org.oxycblt.auxio.music.system.Indexer
+import org.oxycblt.auxio.music.system.IndexerImpl
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface MusicModule {
+    @Singleton @Binds fun repository(musicRepository: MusicRepositoryImpl): MusicRepository
+    @Singleton @Binds fun indexer(indexer: IndexerImpl): Indexer
+    @Binds fun settings(musicSettingsImpl: MusicSettingsImpl): MusicSettings
+}

app/src/main/java/org/oxycblt/auxio/music/MusicRepository.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021 Auxio Project
+ * Copyright (c) 2023 Auxio Project
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,7 +17,8 @@
  
 package org.oxycblt.auxio.music
 
-import org.oxycblt.auxio.music.library.Library
+import javax.inject.Inject
+import org.oxycblt.auxio.music.model.Library
 
 /**
  * A repository granting access to the music library.
@@ -28,22 +29,13 @@ import org.oxycblt.auxio.music.library.Library
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
-class MusicStore private constructor() {
+interface MusicRepository {
-    private val listeners = mutableListOf<Listener>()
-
     /**
      * The current [Library]. May be null if a [Library] has not been successfully loaded yet. This
      * can change, so it's highly recommended to not access this directly and instead rely on
      * [Listener].
      */
-    @Volatile
+    var library: Library?
-    var library: Library? = null
-        set(value) {
-            field = value
-            for (callback in listeners) {
-                callback.onLibraryChanged(library)
-            }
-        }
 
     /**
      * Add a [Listener] to this instance. This can be used to receive changes in the music library.
@@ -51,11 +43,7 @@ class MusicStore private constructor() {
      * @param listener The [Listener] to add.
      * @see Listener
      */
-    @Synchronized
+    fun addListener(listener: Listener)
-    fun addListener(listener: Listener) {
-        listener.onLibraryChanged(library)
-        listeners.add(listener)
-    }
 
     /**
      * Remove a [Listener] from this instance, preventing it from receiving any further updates.
@@ -63,12 +51,9 @@ class MusicStore private constructor() {
      * the first place.
      * @see Listener
      */
-    @Synchronized
+    fun removeListener(listener: Listener)
-    fun removeListener(listener: Listener) {
-        listeners.remove(listener)
-    }
 
-    /** A listener for changes in the music library. */
+    /** A listener for changes in [MusicRepository] */
     interface Listener {
         /**
          * Called when the current [Library] has changed.
@@ -76,25 +61,28 @@ class MusicStore private constructor() {
          */
         fun onLibraryChanged(library: Library?)
     }
+}
 
-    companion object {
+class MusicRepositoryImpl @Inject constructor() : MusicRepository {
-        @Volatile private var INSTANCE: MusicStore? = null
+    private val listeners = mutableListOf<MusicRepository.Listener>()
 
-        /**
+    @Volatile
-         * Get a singleton instance.
+    override var library: Library? = null
-         * @return The (possibly newly-created) singleton instance.
+        set(value) {
-         */
+            field = value
-        fun getInstance(): MusicStore {
+            for (callback in listeners) {
-            val currentInstance = INSTANCE
+                callback.onLibraryChanged(library)
-            if (currentInstance != null) {
-                return currentInstance
-            }
-
-            synchronized(this) {
-                val newInstance = MusicStore()
-                INSTANCE = newInstance
-                return newInstance
             }
         }
+
+    @Synchronized
+    override fun addListener(listener: MusicRepository.Listener) {
+        listener.onLibraryChanged(library)
+        listeners.add(listener)
+    }
+
+    @Synchronized
+    override fun removeListener(listener: MusicRepository.Listener) {
+        listeners.remove(listener)
     }
 }

app/src/main/java/org/oxycblt/auxio/music/MusicSettings.kt

@@ -20,8 +20,10 @@ package org.oxycblt.auxio.music
 import android.content.Context
 import android.os.storage.StorageManager
 import androidx.core.content.edit
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
 import org.oxycblt.auxio.R
-import org.oxycblt.auxio.music.library.Sort
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.music.storage.Directory
 import org.oxycblt.auxio.music.storage.MusicDirectories
 import org.oxycblt.auxio.settings.Settings
@@ -40,6 +42,8 @@ interface MusicSettings : Settings<MusicSettings.Listener> {
     val shouldBeObserving: Boolean
     /** A [String] of characters representing the desired characters to denote multi-value tags. */
     var multiValueSeparators: String
+    /** Whether to trim english articles with song sort names. */
+    val automaticSortNames: Boolean
     /** The [Sort] mode used in [Song] lists. */
     var songSort: Sort
     /** The [Sort] mode used in [Album] lists. */
@@ -61,164 +65,158 @@ interface MusicSettings : Settings<MusicSettings.Listener> {
         /** Called when the [shouldBeObserving] configuration has changed. */
         fun onObservingChanged() {}
     }
+}
 
-    private class Real(context: Context) : Settings.Real<Listener>(context), MusicSettings {
+class MusicSettingsImpl @Inject constructor(@ApplicationContext context: Context) :
-        private val storageManager = context.getSystemServiceCompat(StorageManager::class)
+    Settings.Impl<MusicSettings.Listener>(context), MusicSettings {
+    private val storageManager = context.getSystemServiceCompat(StorageManager::class)
 
-        override var musicDirs: MusicDirectories
+    override var musicDirs: MusicDirectories
-            get() {
+        get() {
-                val dirs =
+            val dirs =
-                    (sharedPreferences.getStringSet(getString(R.string.set_key_music_dirs), null)
+                (sharedPreferences.getStringSet(getString(R.string.set_key_music_dirs), null)
-                            ?: emptySet())
+                        ?: emptySet())
-                        .mapNotNull { Directory.fromDocumentTreeUri(storageManager, it) }
+                    .mapNotNull { Directory.fromDocumentTreeUri(storageManager, it) }
-                return MusicDirectories(
+            return MusicDirectories(
-                    dirs,
+                dirs,
-                    sharedPreferences.getBoolean(
+                sharedPreferences.getBoolean(getString(R.string.set_key_music_dirs_include), false))
-                        getString(R.string.set_key_music_dirs_include), false))
+        }
-            }
+        set(value) {
-            set(value) {
+            sharedPreferences.edit {
-                sharedPreferences.edit {
+                putStringSet(
-                    putStringSet(
+                    getString(R.string.set_key_music_dirs),
-                        getString(R.string.set_key_music_dirs),
+                    value.dirs.map(Directory::toDocumentTreeUri).toSet())
-                        value.dirs.map(Directory::toDocumentTreeUri).toSet())
+                putBoolean(getString(R.string.set_key_music_dirs_include), value.shouldInclude)
-                    putBoolean(getString(R.string.set_key_music_dirs_include), value.shouldInclude)
+                apply()
-                    apply()
-                }
-            }
-
-        override val excludeNonMusic: Boolean
-            get() =
-                sharedPreferences.getBoolean(getString(R.string.set_key_exclude_non_music), true)
-
-        override val shouldBeObserving: Boolean
-            get() = sharedPreferences.getBoolean(getString(R.string.set_key_observing), false)
-
-        override var multiValueSeparators: String
-            // Differ from convention and store a string of separator characters instead of an int
-            // code. This makes it easier to use and more extendable.
-            get() = sharedPreferences.getString(getString(R.string.set_key_separators), "") ?: ""
-            set(value) {
-                sharedPreferences.edit {
-                    putString(getString(R.string.set_key_separators), value)
-                    apply()
-                }
-            }
-
-        override var songSort: Sort
-            get() =
-                Sort.fromIntCode(
-                    sharedPreferences.getInt(getString(R.string.set_key_songs_sort), Int.MIN_VALUE))
-                    ?: Sort(Sort.Mode.ByName, true)
-            set(value) {
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_songs_sort), value.intCode)
-                    apply()
-                }
-            }
-
-        override var albumSort: Sort
-            get() =
-                Sort.fromIntCode(
-                    sharedPreferences.getInt(
-                        getString(R.string.set_key_albums_sort), Int.MIN_VALUE))
-                    ?: Sort(Sort.Mode.ByName, true)
-            set(value) {
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_albums_sort), value.intCode)
-                    apply()
-                }
-            }
-
-        override var artistSort: Sort
-            get() =
-                Sort.fromIntCode(
-                    sharedPreferences.getInt(
-                        getString(R.string.set_key_artists_sort), Int.MIN_VALUE))
-                    ?: Sort(Sort.Mode.ByName, true)
-            set(value) {
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_artists_sort), value.intCode)
-                    apply()
-                }
-            }
-
-        override var genreSort: Sort
-            get() =
-                Sort.fromIntCode(
-                    sharedPreferences.getInt(
-                        getString(R.string.set_key_genres_sort), Int.MIN_VALUE))
-                    ?: Sort(Sort.Mode.ByName, true)
-            set(value) {
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_genres_sort), value.intCode)
-                    apply()
-                }
-            }
-
-        override var albumSongSort: Sort
-            get() {
-                var sort =
-                    Sort.fromIntCode(
-                        sharedPreferences.getInt(
-                            getString(R.string.set_key_album_songs_sort), Int.MIN_VALUE))
-                        ?: Sort(Sort.Mode.ByDisc, true)
-
-                // Correct legacy album sort modes to Disc
-                if (sort.mode is Sort.Mode.ByName) {
-                    sort = sort.withMode(Sort.Mode.ByDisc)
-                }
-
-                return sort
-            }
-            set(value) {
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_album_songs_sort), value.intCode)
-                    apply()
-                }
-            }
-
-        override var artistSongSort: Sort
-            get() =
-                Sort.fromIntCode(
-                    sharedPreferences.getInt(
-                        getString(R.string.set_key_artist_songs_sort), Int.MIN_VALUE))
-                    ?: Sort(Sort.Mode.ByDate, false)
-            set(value) {
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_artist_songs_sort), value.intCode)
-                    apply()
-                }
-            }
-
-        override var genreSongSort: Sort
-            get() =
-                Sort.fromIntCode(
-                    sharedPreferences.getInt(
-                        getString(R.string.set_key_genre_songs_sort), Int.MIN_VALUE))
-                    ?: Sort(Sort.Mode.ByName, true)
-            set(value) {
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_genre_songs_sort), value.intCode)
-                    apply()
-                }
-            }
-
-        override fun onSettingChanged(key: String, listener: Listener) {
-            when (key) {
-                getString(R.string.set_key_exclude_non_music),
-                getString(R.string.set_key_music_dirs),
-                getString(R.string.set_key_music_dirs_include),
-                getString(R.string.set_key_separators) -> listener.onIndexingSettingChanged()
-                getString(R.string.set_key_observing) -> listener.onObservingChanged()
             }
         }
-    }
 
-    companion object {
+    override val excludeNonMusic: Boolean
-        /**
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_exclude_non_music), true)
-         * Get a framework-backed implementation.
+
-         * @param context [Context] required.
+    override val shouldBeObserving: Boolean
-         */
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_observing), false)
-        fun from(context: Context): MusicSettings = Real(context)
+
+    override var multiValueSeparators: String
+        // Differ from convention and store a string of separator characters instead of an int
+        // code. This makes it easier to use and more extendable.
+        get() = sharedPreferences.getString(getString(R.string.set_key_separators), "") ?: ""
+        set(value) {
+            sharedPreferences.edit {
+                putString(getString(R.string.set_key_separators), value)
+                apply()
+            }
+        }
+
+    override val automaticSortNames: Boolean
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_auto_sort_names), true)
+
+    override var songSort: Sort
+        get() =
+            Sort.fromIntCode(
+                sharedPreferences.getInt(getString(R.string.set_key_songs_sort), Int.MIN_VALUE))
+                ?: Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+        set(value) {
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_songs_sort), value.intCode)
+                apply()
+            }
+        }
+
+    override var albumSort: Sort
+        get() =
+            Sort.fromIntCode(
+                sharedPreferences.getInt(getString(R.string.set_key_albums_sort), Int.MIN_VALUE))
+                ?: Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+        set(value) {
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_albums_sort), value.intCode)
+                apply()
+            }
+        }
+
+    override var artistSort: Sort
+        get() =
+            Sort.fromIntCode(
+                sharedPreferences.getInt(getString(R.string.set_key_artists_sort), Int.MIN_VALUE))
+                ?: Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+        set(value) {
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_artists_sort), value.intCode)
+                apply()
+            }
+        }
+
+    override var genreSort: Sort
+        get() =
+            Sort.fromIntCode(
+                sharedPreferences.getInt(getString(R.string.set_key_genres_sort), Int.MIN_VALUE))
+                ?: Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+        set(value) {
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_genres_sort), value.intCode)
+                apply()
+            }
+        }
+
+    override var albumSongSort: Sort
+        get() {
+            var sort =
+                Sort.fromIntCode(
+                    sharedPreferences.getInt(
+                        getString(R.string.set_key_album_songs_sort), Int.MIN_VALUE))
+                    ?: Sort(Sort.Mode.ByDisc, Sort.Direction.ASCENDING)
+
+            // Correct legacy album sort modes to Disc
+            if (sort.mode is Sort.Mode.ByName) {
+                sort = sort.withMode(Sort.Mode.ByDisc)
+            }
+
+            return sort
+        }
+        set(value) {
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_album_songs_sort), value.intCode)
+                apply()
+            }
+        }
+
+    override var artistSongSort: Sort
+        get() =
+            Sort.fromIntCode(
+                sharedPreferences.getInt(
+                    getString(R.string.set_key_artist_songs_sort), Int.MIN_VALUE))
+                ?: Sort(Sort.Mode.ByDate, Sort.Direction.DESCENDING)
+        set(value) {
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_artist_songs_sort), value.intCode)
+                apply()
+            }
+        }
+
+    override var genreSongSort: Sort
+        get() =
+            Sort.fromIntCode(
+                sharedPreferences.getInt(
+                    getString(R.string.set_key_genre_songs_sort), Int.MIN_VALUE))
+                ?: Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+        set(value) {
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_genre_songs_sort), value.intCode)
+                apply()
+            }
+        }
+
+    override fun onSettingChanged(key: String, listener: MusicSettings.Listener) {
+        // TODO: Differentiate "hard reloads" (Need the cache) and "Soft reloads"
+        //  (just need to manipulate data)
+        when (key) {
+            getString(R.string.set_key_exclude_non_music),
+            getString(R.string.set_key_music_dirs),
+            getString(R.string.set_key_music_dirs_include),
+            getString(R.string.set_key_separators),
+            getString(R.string.set_key_auto_sort_names) -> listener.onIndexingSettingChanged()
+            getString(R.string.set_key_observing) -> listener.onObservingChanged()
+        }
     }
 }

app/src/main/java/org/oxycblt/auxio/music/MusicViewModel.kt

@@ -18,6 +18,8 @@
 package org.oxycblt.auxio.music
 
 import androidx.lifecycle.ViewModel
+import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import org.oxycblt.auxio.music.system.Indexer
@@ -26,8 +28,9 @@ import org.oxycblt.auxio.music.system.Indexer
  * A [ViewModel] providing data specific to the music loading process.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class MusicViewModel : ViewModel(), Indexer.Listener {
+@HiltViewModel
-    private val indexer = Indexer.getInstance()
+class MusicViewModel @Inject constructor(private val indexer: Indexer) :
+    ViewModel(), Indexer.Listener {
 
     private val _indexerState = MutableStateFlow<Indexer.State?>(null)
     /** The current music loading state, or null if no loading is going on. */

app/src/main/java/org/oxycblt/auxio/music/cache/CacheDatabase.kt

@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.cache
+
+import androidx.room.Dao
+import androidx.room.Database
+import androidx.room.Entity
+import androidx.room.Insert
+import androidx.room.PrimaryKey
+import androidx.room.Query
+import androidx.room.RoomDatabase
+import androidx.room.TypeConverter
+import androidx.room.TypeConverters
+import org.oxycblt.auxio.music.metadata.Date
+import org.oxycblt.auxio.music.metadata.correctWhitespace
+import org.oxycblt.auxio.music.metadata.splitEscaped
+import org.oxycblt.auxio.music.model.RawSong
+
+@Database(entities = [CachedSong::class], version = 27, exportSchema = false)
+abstract class CacheDatabase : RoomDatabase() {
+    abstract fun cachedSongsDao(): CachedSongsDao
+}
+
+@Dao
+interface CachedSongsDao {
+    @Query("SELECT * FROM ${CachedSong.TABLE_NAME}") suspend fun readSongs(): List<CachedSong>
+    @Query("DELETE FROM ${CachedSong.TABLE_NAME}") suspend fun nukeSongs()
+    @Insert suspend fun insertSongs(songs: List<CachedSong>)
+}
+
+@Entity(tableName = CachedSong.TABLE_NAME)
+@TypeConverters(CachedSong.Converters::class)
+data class CachedSong(
+    /**
+     * The ID of the [RawSong]'s audio file, obtained from MediaStore. Note that this ID is highly
+     * unstable and should only be used for accessing the audio file.
+     */
+    @PrimaryKey var mediaStoreId: Long,
+    /** @see RawSong.dateAdded */
+    var dateAdded: Long,
+    /** The latest date the [RawSong]'s audio file was modified, as a unix epoch timestamp. */
+    var dateModified: Long,
+    /** @see RawSong.size */
+    var size: Long? = null,
+    /** @see RawSong */
+    var durationMs: Long,
+    /** @see RawSong.musicBrainzId */
+    var musicBrainzId: String? = null,
+    /** @see RawSong.name */
+    var name: String,
+    /** @see RawSong.sortName */
+    var sortName: String? = null,
+    /** @see RawSong.track */
+    var track: Int? = null,
+    /** @see RawSong.name */
+    var disc: Int? = null,
+    /** @See RawSong.subtitle */
+    var subtitle: String? = null,
+    /** @see RawSong.date */
+    var date: Date? = null,
+    /** @see RawSong.albumMusicBrainzId */
+    var albumMusicBrainzId: String? = null,
+    /** @see RawSong.albumName */
+    var albumName: String,
+    /** @see RawSong.albumSortName */
+    var albumSortName: String? = null,
+    /** @see RawSong.releaseTypes */
+    var releaseTypes: List<String> = listOf(),
+    /** @see RawSong.artistMusicBrainzIds */
+    var artistMusicBrainzIds: List<String> = listOf(),
+    /** @see RawSong.artistNames */
+    var artistNames: List<String> = listOf(),
+    /** @see RawSong.artistSortNames */
+    var artistSortNames: List<String> = listOf(),
+    /** @see RawSong.albumArtistMusicBrainzIds */
+    var albumArtistMusicBrainzIds: List<String> = listOf(),
+    /** @see RawSong.albumArtistNames */
+    var albumArtistNames: List<String> = listOf(),
+    /** @see RawSong.albumArtistSortNames */
+    var albumArtistSortNames: List<String> = listOf(),
+    /** @see RawSong.genreNames */
+    var genreNames: List<String> = listOf()
+) {
+    fun copyToRaw(rawSong: RawSong): CachedSong {
+        rawSong.musicBrainzId = musicBrainzId
+        rawSong.name = name
+        rawSong.sortName = sortName
+
+        rawSong.size = size
+        rawSong.durationMs = durationMs
+
+        rawSong.track = track
+        rawSong.disc = disc
+        rawSong.subtitle = subtitle
+        rawSong.date = date
+
+        rawSong.albumMusicBrainzId = albumMusicBrainzId
+        rawSong.albumName = albumName
+        rawSong.albumSortName = albumSortName
+        rawSong.releaseTypes = releaseTypes
+
+        rawSong.artistMusicBrainzIds = artistMusicBrainzIds
+        rawSong.artistNames = artistNames
+        rawSong.artistSortNames = artistSortNames
+
+        rawSong.albumArtistMusicBrainzIds = albumArtistMusicBrainzIds
+        rawSong.albumArtistNames = albumArtistNames
+        rawSong.albumArtistSortNames = albumArtistSortNames
+
+        rawSong.genreNames = genreNames
+        return this
+    }
+
+    object Converters {
+        @TypeConverter
+        fun fromMultiValue(values: List<String>) =
+            values.joinToString(";") { it.replace(";", "\\;") }
+
+        @TypeConverter
+        fun toMultiValue(string: String) = string.splitEscaped { it == ';' }.correctWhitespace()
+
+        @TypeConverter fun fromDate(date: Date?) = date?.toString()
+
+        @TypeConverter fun toDate(string: String?) = string?.let(Date::from)
+    }
+
+    companion object {
+        const val TABLE_NAME = "cached_songs"
+
+        fun fromRaw(rawSong: RawSong) =
+            CachedSong(
+                mediaStoreId =
+                    requireNotNull(rawSong.mediaStoreId) { "Invalid raw: No MediaStore ID" },
+                dateAdded = requireNotNull(rawSong.dateAdded) { "Invalid raw: No date added" },
+                dateModified =
+                    requireNotNull(rawSong.dateModified) { "Invalid raw: No date modified" },
+                musicBrainzId = rawSong.musicBrainzId,
+                name = requireNotNull(rawSong.name) { "Invalid raw: No name" },
+                sortName = rawSong.sortName,
+                size = rawSong.size,
+                durationMs = requireNotNull(rawSong.durationMs) { "Invalid raw: No duration" },
+                track = rawSong.track,
+                disc = rawSong.disc,
+                subtitle = rawSong.subtitle,
+                date = rawSong.date,
+                albumMusicBrainzId = rawSong.albumMusicBrainzId,
+                albumName = requireNotNull(rawSong.albumName) { "Invalid raw: No album name" },
+                albumSortName = rawSong.albumSortName,
+                releaseTypes = rawSong.releaseTypes,
+                artistMusicBrainzIds = rawSong.artistMusicBrainzIds,
+                artistNames = rawSong.artistNames,
+                artistSortNames = rawSong.artistSortNames,
+                albumArtistMusicBrainzIds = rawSong.albumArtistMusicBrainzIds,
+                albumArtistNames = rawSong.albumArtistNames,
+                albumArtistSortNames = rawSong.albumArtistSortNames,
+                genreNames = rawSong.genreNames)
+    }
+}

app/src/main/java/org/oxycblt/auxio/music/cache/CacheModule.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.cache
+
+import android.content.Context
+import androidx.room.Room
+import dagger.Binds
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface CacheModule {
+    @Binds fun cacheRepository(cacheRepository: CacheRepositoryImpl): CacheRepository
+}
+
+@Module
+@InstallIn(SingletonComponent::class)
+class CacheRoomModule {
+    @Singleton
+    @Provides
+    fun database(@ApplicationContext context: Context) =
+        Room.databaseBuilder(
+                context.applicationContext, CacheDatabase::class.java, "music_cache.db")
+            .fallbackToDestructiveMigration()
+            .fallbackToDestructiveMigrationFrom(0)
+            .fallbackToDestructiveMigrationOnDowngrade()
+            .build()
+
+    @Provides fun cachedSongsDao(database: CacheDatabase) = database.cachedSongsDao()
+}

app/src/main/java/org/oxycblt/auxio/music/cache/CacheRepository.kt

@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2022 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.cache
+
+import javax.inject.Inject
+import org.oxycblt.auxio.music.model.RawSong
+import org.oxycblt.auxio.util.*
+
+/**
+ * A repository allowing access to cached metadata obtained in prior music loading operations.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+interface CacheRepository {
+    /**
+     * Read the current [Cache], if it exists.
+     * @return The stored [Cache], or null if it could not be obtained.
+     */
+    suspend fun readCache(): Cache?
+
+    /**
+     * Write the list of newly-loaded [RawSong]s to the cache, replacing the prior data.
+     * @param rawSongs The [rawSongs] to write to the cache.
+     */
+    suspend fun writeCache(rawSongs: List<RawSong>)
+}
+
+class CacheRepositoryImpl @Inject constructor(private val cachedSongsDao: CachedSongsDao) :
+    CacheRepository {
+    override suspend fun readCache(): Cache? =
+        try {
+            // Faster to load the whole database into memory than do a query on each
+            // populate call.
+            CacheImpl(cachedSongsDao.readSongs())
+        } catch (e: Exception) {
+            logE("Unable to load cache database.")
+            logE(e.stackTraceToString())
+            null
+        }
+
+    override suspend fun writeCache(rawSongs: List<RawSong>) {
+        try {
+            // Still write out whatever data was extracted.
+            cachedSongsDao.nukeSongs()
+            cachedSongsDao.insertSongs(rawSongs.map(CachedSong::fromRaw))
+        } catch (e: Exception) {
+            logE("Unable to save cache database.")
+            logE(e.stackTraceToString())
+        }
+    }
+}
+
+/**
+ * A cache of music metadata obtained in prior music loading operations. Obtain an instance with
+ * [CacheRepository].
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+interface Cache {
+    /** Whether this cache has encountered a [RawSong] that did not have a cache entry. */
+    val invalidated: Boolean
+
+    /**
+     * Populate a [RawSong] from a cache entry, if it exists.
+     * @param rawSong The [RawSong] to populate.
+     * @return true if a cache entry could be applied to [rawSong], false otherwise.
+     */
+    fun populate(rawSong: RawSong): Boolean
+}
+
+private class CacheImpl(cachedSongs: List<CachedSong>) : Cache {
+    private val cacheMap = buildMap {
+        for (cachedSong in cachedSongs) {
+            put(cachedSong.mediaStoreId, cachedSong)
+        }
+    }
+
+    override var invalidated = false
+    override fun populate(rawSong: RawSong): Boolean {
+
+        // For a cached raw song to be used, it must exist within the cache and have matching
+        // addition and modification timestamps. Technically the addition timestamp doesn't
+        // exist, but to safeguard against possible OEM-specific timestamp incoherence, we
+        // check for it anyway.
+        val cachedSong = cacheMap[rawSong.mediaStoreId]
+        if (cachedSong != null &&
+            cachedSong.dateAdded == rawSong.dateAdded &&
+            cachedSong.dateModified == rawSong.dateModified) {
+            cachedSong.copyToRaw(rawSong)
+            return true
+        }
+
+        // We could not populate this song. This means our cache is stale and should be
+        // re-written with newly-loaded music.
+        invalidated = true
+        return false
+    }
+}

app/src/main/java/org/oxycblt/auxio/music/extractor/CacheExtractor.kt

@@ -1,468 +0,0 @@
-/*
- * Copyright (c) 2022 Auxio Project
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
- 
-package org.oxycblt.auxio.music.extractor
-
-import android.content.ContentValues
-import android.content.Context
-import android.database.sqlite.SQLiteDatabase
-import android.database.sqlite.SQLiteOpenHelper
-import androidx.core.database.getIntOrNull
-import androidx.core.database.getStringOrNull
-import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.parsing.correctWhitespace
-import org.oxycblt.auxio.music.parsing.splitEscaped
-import org.oxycblt.auxio.music.tags.Date
-import org.oxycblt.auxio.util.*
-
-/**
- * Defines an Extractor that can load cached music. This is the first step in the music extraction
- * process and is an optimization to avoid the slow [MediaStoreExtractor] and [MetadataExtractor]
- * extraction process.
- * @author Alexander Capehart (OxygenCobalt)
- */
-interface CacheExtractor {
-    /** Initialize the Extractor by reading the cache data into memory. */
-    fun init()
-
-    /**
-     * Finalize the Extractor by writing the newly-loaded [Song.Raw]s back into the cache, alongside
-     * freeing up memory.
-     * @param rawSongs The songs to write into the cache.
-     */
-    fun finalize(rawSongs: List<Song.Raw>)
-
-    /**
-     * Use the cache to populate the given [Song.Raw].
-     * @param rawSong The [Song.Raw] to attempt to populate. Note that this [Song.Raw] will only
-     * contain the bare minimum information required to load a cache entry.
-     * @return An [ExtractionResult] representing the result of the operation.
-     * [ExtractionResult.PARSED] is not returned.
-     */
-    fun populate(rawSong: Song.Raw): ExtractionResult
-}
-
-/**
- * A [CacheExtractor] only capable of writing to the cache. This can be used to load music with
- * without the cache if the user desires.
- * @param context [Context] required to read the cache database.
- * @see CacheExtractor
- * @author Alexander Capehart (OxygenCobalt)
- */
-open class WriteOnlyCacheExtractor(private val context: Context) : CacheExtractor {
-    override fun init() {
-        // Nothing to do.
-    }
-
-    override fun finalize(rawSongs: List<Song.Raw>) {
-        try {
-            // Still write out whatever data was extracted.
-            CacheDatabase.getInstance(context).write(rawSongs)
-        } catch (e: Exception) {
-            logE("Unable to save cache database.")
-            logE(e.stackTraceToString())
-        }
-    }
-
-    override fun populate(rawSong: Song.Raw) =
-        // Nothing to do.
-        ExtractionResult.NONE
-}
-
-/**
- * A [CacheExtractor] that supports reading from and writing to the cache.
- * @param context [Context] required to load
- * @see CacheExtractor
- * @author Alexander Capehart
- */
-class ReadWriteCacheExtractor(private val context: Context) : WriteOnlyCacheExtractor(context) {
-    private var cacheMap: Map<Long, Song.Raw>? = null
-    private var invalidate = false
-
-    override fun init() {
-        try {
-            // Faster to load the whole database into memory than do a query on each
-            // populate call.
-            cacheMap = CacheDatabase.getInstance(context).read()
-        } catch (e: Exception) {
-            logE("Unable to load cache database.")
-            logE(e.stackTraceToString())
-        }
-    }
-
-    override fun finalize(rawSongs: List<Song.Raw>) {
-        cacheMap = null
-        // Same some time by not re-writing the cache if we were able to create the entire
-        // library from it. If there is even just one song we could not populate from the
-        // cache, then we will re-write it.
-        if (invalidate) {
-            logD("Cache was invalidated during loading, rewriting")
-            super.finalize(rawSongs)
-        }
-    }
-
-    override fun populate(rawSong: Song.Raw): ExtractionResult {
-        val map = cacheMap ?: return ExtractionResult.NONE
-
-        // For a cached raw song to be used, it must exist within the cache and have matching
-        // addition and modification timestamps. Technically the addition timestamp doesn't
-        // exist, but to safeguard against possible OEM-specific timestamp incoherence, we
-        // check for it anyway.
-        val cachedRawSong = map[rawSong.mediaStoreId]
-        if (cachedRawSong != null &&
-            cachedRawSong.dateAdded == rawSong.dateAdded &&
-            cachedRawSong.dateModified == rawSong.dateModified) {
-            // No built-in "copy from" method for data classes, just have to assign
-            // the data ourselves.
-            rawSong.musicBrainzId = cachedRawSong.musicBrainzId
-            rawSong.name = cachedRawSong.name
-            rawSong.sortName = cachedRawSong.sortName
-
-            rawSong.size = cachedRawSong.size
-            rawSong.durationMs = cachedRawSong.durationMs
-
-            rawSong.track = cachedRawSong.track
-            rawSong.disc = cachedRawSong.disc
-            rawSong.date = cachedRawSong.date
-
-            rawSong.albumMusicBrainzId = cachedRawSong.albumMusicBrainzId
-            rawSong.albumName = cachedRawSong.albumName
-            rawSong.albumSortName = cachedRawSong.albumSortName
-            rawSong.releaseTypes = cachedRawSong.releaseTypes
-
-            rawSong.artistMusicBrainzIds = cachedRawSong.artistMusicBrainzIds
-            rawSong.artistNames = cachedRawSong.artistNames
-            rawSong.artistSortNames = cachedRawSong.artistSortNames
-
-            rawSong.albumArtistMusicBrainzIds = cachedRawSong.albumArtistMusicBrainzIds
-            rawSong.albumArtistNames = cachedRawSong.albumArtistNames
-            rawSong.albumArtistSortNames = cachedRawSong.albumArtistSortNames
-
-            rawSong.genreNames = cachedRawSong.genreNames
-
-            return ExtractionResult.CACHED
-        }
-
-        // We could not populate this song. This means our cache is stale and should be
-        // re-written with newly-loaded music.
-        invalidate = true
-        return ExtractionResult.NONE
-    }
-}
-
-/**
- * Internal [Song.Raw] cache database.
- * @author Alexander Capehart (OxygenCobalt)
- * @see [CacheExtractor]
- */
-private class CacheDatabase(context: Context) :
-    SQLiteOpenHelper(context, DB_NAME, null, DB_VERSION) {
-    override fun onCreate(db: SQLiteDatabase) {
-        // Map the cacheable raw song fields to database fields. Cache-able in this context
-        // means information independent of the file-system, excluding IDs and timestamps required
-        // to retrieve items from the cache.
-        db.createTable(TABLE_RAW_SONGS) {
-            append("${Columns.MEDIA_STORE_ID} LONG PRIMARY KEY,")
-            append("${Columns.DATE_ADDED} LONG NOT NULL,")
-            append("${Columns.DATE_MODIFIED} LONG NOT NULL,")
-            append("${Columns.SIZE} LONG NOT NULL,")
-            append("${Columns.DURATION} LONG NOT NULL,")
-            append("${Columns.MUSIC_BRAINZ_ID} STRING,")
-            append("${Columns.NAME} STRING NOT NULL,")
-            append("${Columns.SORT_NAME} STRING,")
-            append("${Columns.TRACK} INT,")
-            append("${Columns.DISC} INT,")
-            append("${Columns.DATE} STRING,")
-            append("${Columns.ALBUM_MUSIC_BRAINZ_ID} STRING,")
-            append("${Columns.ALBUM_NAME} STRING NOT NULL,")
-            append("${Columns.ALBUM_SORT_NAME} STRING,")
-            append("${Columns.RELEASE_TYPES} STRING,")
-            append("${Columns.ARTIST_MUSIC_BRAINZ_IDS} STRING,")
-            append("${Columns.ARTIST_NAMES} STRING,")
-            append("${Columns.ARTIST_SORT_NAMES} STRING,")
-            append("${Columns.ALBUM_ARTIST_MUSIC_BRAINZ_IDS} STRING,")
-            append("${Columns.ALBUM_ARTIST_NAMES} STRING,")
-            append("${Columns.ALBUM_ARTIST_SORT_NAMES} STRING,")
-            append("${Columns.GENRE_NAMES} STRING")
-        }
-    }
-
-    override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) = nuke(db)
-
-    override fun onDowngrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) = nuke(db)
-
-    private fun nuke(db: SQLiteDatabase) {
-        // No cost to nuking this database, only causes higher loading times.
-        logD("Nuking database")
-        db.apply {
-            execSQL("DROP TABLE IF EXISTS $TABLE_RAW_SONGS")
-            onCreate(this)
-        }
-    }
-
-    /**
-     * Read out this database into memory.
-     * @return A mapping between the MediaStore IDs of the cache entries and a [Song.Raw] containing
-     * the cacheable data for the entry. Note that any filesystem-dependent information (excluding
-     * IDs and timestamps) is not cached.
-     */
-    fun read(): Map<Long, Song.Raw> {
-        requireBackgroundThread()
-        val start = System.currentTimeMillis()
-        val map = mutableMapOf<Long, Song.Raw>()
-        readableDatabase.queryAll(TABLE_RAW_SONGS) { cursor ->
-            if (cursor.count == 0) {
-                // Nothing to do.
-                return@queryAll
-            }
-
-            val idIndex = cursor.getColumnIndexOrThrow(Columns.MEDIA_STORE_ID)
-            val dateAddedIndex = cursor.getColumnIndexOrThrow(Columns.DATE_ADDED)
-            val dateModifiedIndex = cursor.getColumnIndexOrThrow(Columns.DATE_MODIFIED)
-
-            val sizeIndex = cursor.getColumnIndexOrThrow(Columns.SIZE)
-            val durationIndex = cursor.getColumnIndexOrThrow(Columns.DURATION)
-
-            val musicBrainzIdIndex = cursor.getColumnIndexOrThrow(Columns.MUSIC_BRAINZ_ID)
-            val nameIndex = cursor.getColumnIndexOrThrow(Columns.NAME)
-            val sortNameIndex = cursor.getColumnIndexOrThrow(Columns.SORT_NAME)
-
-            val trackIndex = cursor.getColumnIndexOrThrow(Columns.TRACK)
-            val discIndex = cursor.getColumnIndexOrThrow(Columns.DISC)
-            val dateIndex = cursor.getColumnIndexOrThrow(Columns.DATE)
-
-            val albumMusicBrainzIdIndex =
-                cursor.getColumnIndexOrThrow(Columns.ALBUM_MUSIC_BRAINZ_ID)
-            val albumNameIndex = cursor.getColumnIndexOrThrow(Columns.ALBUM_NAME)
-            val albumSortNameIndex = cursor.getColumnIndexOrThrow(Columns.ALBUM_SORT_NAME)
-            val releaseTypesIndex = cursor.getColumnIndexOrThrow(Columns.RELEASE_TYPES)
-
-            val artistMusicBrainzIdsIndex =
-                cursor.getColumnIndexOrThrow(Columns.ARTIST_MUSIC_BRAINZ_IDS)
-            val artistNamesIndex = cursor.getColumnIndexOrThrow(Columns.ARTIST_NAMES)
-            val artistSortNamesIndex = cursor.getColumnIndexOrThrow(Columns.ARTIST_SORT_NAMES)
-
-            val albumArtistMusicBrainzIdsIndex =
-                cursor.getColumnIndexOrThrow(Columns.ALBUM_ARTIST_MUSIC_BRAINZ_IDS)
-            val albumArtistNamesIndex = cursor.getColumnIndexOrThrow(Columns.ALBUM_ARTIST_NAMES)
-            val albumArtistSortNamesIndex =
-                cursor.getColumnIndexOrThrow(Columns.ALBUM_ARTIST_SORT_NAMES)
-
-            val genresIndex = cursor.getColumnIndexOrThrow(Columns.GENRE_NAMES)
-
-            while (cursor.moveToNext()) {
-                val raw = Song.Raw()
-                val id = cursor.getLong(idIndex)
-
-                raw.mediaStoreId = id
-                raw.dateAdded = cursor.getLong(dateAddedIndex)
-                raw.dateModified = cursor.getLong(dateModifiedIndex)
-
-                raw.size = cursor.getLong(sizeIndex)
-                raw.durationMs = cursor.getLong(durationIndex)
-
-                raw.musicBrainzId = cursor.getStringOrNull(musicBrainzIdIndex)
-                raw.name = cursor.getString(nameIndex)
-                raw.sortName = cursor.getStringOrNull(sortNameIndex)
-
-                raw.track = cursor.getIntOrNull(trackIndex)
-                raw.disc = cursor.getIntOrNull(discIndex)
-                raw.date = cursor.getStringOrNull(dateIndex)?.let(Date::from)
-
-                raw.albumMusicBrainzId = cursor.getStringOrNull(albumMusicBrainzIdIndex)
-                raw.albumName = cursor.getString(albumNameIndex)
-                raw.albumSortName = cursor.getStringOrNull(albumSortNameIndex)
-                cursor.getStringOrNull(releaseTypesIndex)?.let {
-                    raw.releaseTypes = it.parseSQLMultiValue()
-                }
-
-                cursor.getStringOrNull(artistMusicBrainzIdsIndex)?.let {
-                    raw.artistMusicBrainzIds = it.parseSQLMultiValue()
-                }
-                cursor.getStringOrNull(artistNamesIndex)?.let {
-                    raw.artistNames = it.parseSQLMultiValue()
-                }
-                cursor.getStringOrNull(artistSortNamesIndex)?.let {
-                    raw.artistSortNames = it.parseSQLMultiValue()
-                }
-
-                cursor.getStringOrNull(albumArtistMusicBrainzIdsIndex)?.let {
-                    raw.albumArtistMusicBrainzIds = it.parseSQLMultiValue()
-                }
-                cursor.getStringOrNull(albumArtistNamesIndex)?.let {
-                    raw.albumArtistNames = it.parseSQLMultiValue()
-                }
-                cursor.getStringOrNull(albumArtistSortNamesIndex)?.let {
-                    raw.albumArtistSortNames = it.parseSQLMultiValue()
-                }
-
-                cursor.getStringOrNull(genresIndex)?.let {
-                    raw.genreNames = it.parseSQLMultiValue()
-                }
-
-                map[id] = raw
-            }
-        }
-
-        logD("Read cache in ${System.currentTimeMillis() - start}ms")
-
-        return map
-    }
-
-    /**
-     * Write a new list of [Song.Raw] to this database.
-     * @param rawSongs The new [Song.Raw] instances to cache. Note that any filesystem-dependent
-     * information (excluding IDs and timestamps) is not cached.
-     */
-    fun write(rawSongs: List<Song.Raw>) {
-        val start = System.currentTimeMillis()
-
-        writableDatabase.writeList(rawSongs, TABLE_RAW_SONGS) { _, rawSong ->
-            ContentValues(22).apply {
-                put(Columns.MEDIA_STORE_ID, rawSong.mediaStoreId)
-                put(Columns.DATE_ADDED, rawSong.dateAdded)
-                put(Columns.DATE_MODIFIED, rawSong.dateModified)
-
-                put(Columns.SIZE, rawSong.size)
-                put(Columns.DURATION, rawSong.durationMs)
-
-                put(Columns.MUSIC_BRAINZ_ID, rawSong.musicBrainzId)
-                put(Columns.NAME, rawSong.name)
-                put(Columns.SORT_NAME, rawSong.sortName)
-
-                put(Columns.TRACK, rawSong.track)
-                put(Columns.DISC, rawSong.disc)
-                put(Columns.DATE, rawSong.date?.toString())
-
-                put(Columns.ALBUM_MUSIC_BRAINZ_ID, rawSong.albumMusicBrainzId)
-                put(Columns.ALBUM_NAME, rawSong.albumName)
-                put(Columns.ALBUM_SORT_NAME, rawSong.albumSortName)
-                put(Columns.RELEASE_TYPES, rawSong.releaseTypes.toSQLMultiValue())
-
-                put(Columns.ARTIST_MUSIC_BRAINZ_IDS, rawSong.artistMusicBrainzIds.toSQLMultiValue())
-                put(Columns.ARTIST_NAMES, rawSong.artistNames.toSQLMultiValue())
-                put(Columns.ARTIST_SORT_NAMES, rawSong.artistSortNames.toSQLMultiValue())
-
-                put(
-                    Columns.ALBUM_ARTIST_MUSIC_BRAINZ_IDS,
-                    rawSong.albumArtistMusicBrainzIds.toSQLMultiValue())
-                put(Columns.ALBUM_ARTIST_NAMES, rawSong.albumArtistNames.toSQLMultiValue())
-                put(Columns.ALBUM_ARTIST_SORT_NAMES, rawSong.albumArtistSortNames.toSQLMultiValue())
-
-                put(Columns.GENRE_NAMES, rawSong.genreNames.toSQLMultiValue())
-            }
-        }
-
-        logD("Wrote cache in ${System.currentTimeMillis() - start}ms")
-    }
-
-    // SQLite does not natively support multiple values, so we have to serialize multi-value
-    // tags with separators. Not ideal, but nothing we can do.
-
-    /**
-     * Transforms the multi-string list into a SQL-safe multi-string value.
-     * @return A single string containing all values within the multi-string list, delimited by a
-     * ";". Pre-existing ";" characters will be escaped.
-     */
-    private fun List<String>.toSQLMultiValue() =
-        if (isNotEmpty()) {
-            joinToString(";") { it.replace(";", "\\;") }
-        } else {
-            null
-        }
-
-    /**
-     * Transforms the SQL-safe multi-string value into a multi-string list.
-     * @return A list of strings corresponding to the delimited values present within the original
-     * string. Escaped delimiters are converted back into their normal forms.
-     */
-    private fun String.parseSQLMultiValue() = splitEscaped { it == ';' }.correctWhitespace()
-
-    /** Defines the columns used in this database. */
-    private object Columns {
-        /** @see Song.Raw.mediaStoreId */
-        const val MEDIA_STORE_ID = "msid"
-        /** @see Song.Raw.dateAdded */
-        const val DATE_ADDED = "date_added"
-        /** @see Song.Raw.dateModified */
-        const val DATE_MODIFIED = "date_modified"
-        /** @see Song.Raw.size */
-        const val SIZE = "size"
-        /** @see Song.Raw.durationMs */
-        const val DURATION = "duration"
-        /** @see Song.Raw.musicBrainzId */
-        const val MUSIC_BRAINZ_ID = "mbid"
-        /** @see Song.Raw.name */
-        const val NAME = "name"
-        /** @see Song.Raw.sortName */
-        const val SORT_NAME = "sort_name"
-        /** @see Song.Raw.track */
-        const val TRACK = "track"
-        /** @see Song.Raw.disc */
-        const val DISC = "disc"
-        /** @see Song.Raw.date */
-        const val DATE = "date"
-        /** @see Song.Raw.albumMusicBrainzId */
-        const val ALBUM_MUSIC_BRAINZ_ID = "album_mbid"
-        /** @see Song.Raw.albumName */
-        const val ALBUM_NAME = "album"
-        /** @see Song.Raw.albumSortName */
-        const val ALBUM_SORT_NAME = "album_sort"
-        /** @see Song.Raw.releaseTypes */
-        const val RELEASE_TYPES = "album_types"
-        /** @see Song.Raw.artistMusicBrainzIds */
-        const val ARTIST_MUSIC_BRAINZ_IDS = "artists_mbid"
-        /** @see Song.Raw.artistNames */
-        const val ARTIST_NAMES = "artists"
-        /** @see Song.Raw.artistSortNames */
-        const val ARTIST_SORT_NAMES = "artists_sort"
-        /** @see Song.Raw.albumArtistMusicBrainzIds */
-        const val ALBUM_ARTIST_MUSIC_BRAINZ_IDS = "album_artists_mbid"
-        /** @see Song.Raw.albumArtistNames */
-        const val ALBUM_ARTIST_NAMES = "album_artists"
-        /** @see Song.Raw.albumArtistSortNames */
-        const val ALBUM_ARTIST_SORT_NAMES = "album_artists_sort"
-        /** @see Song.Raw.genreNames */
-        const val GENRE_NAMES = "genres"
-    }
-
-    companion object {
-        private const val DB_NAME = "auxio_music_cache.db"
-        private const val DB_VERSION = 2
-        private const val TABLE_RAW_SONGS = "raw_songs"
-
-        @Volatile private var INSTANCE: CacheDatabase? = null
-
-        /**
-         * Get a singleton instance.
-         * @return The (possibly newly-created) singleton instance.
-         */
-        fun getInstance(context: Context): CacheDatabase {
-            val currentInstance = INSTANCE
-
-            if (currentInstance != null) {
-                return currentInstance
-            }
-
-            synchronized(this) {
-                val newInstance = CacheDatabase(context.applicationContext)
-                INSTANCE = newInstance
-                return newInstance
-            }
-        }
-    }
-}

app/src/main/java/org/oxycblt/auxio/music/extractor/MediaStoreExtractor.kt

@@ -1,587 +0,0 @@
-/*
- * Copyright (c) 2022 Auxio Project
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
- 
-package org.oxycblt.auxio.music.extractor
-
-import android.content.Context
-import android.database.Cursor
-import android.os.Build
-import android.os.storage.StorageManager
-import android.os.storage.StorageVolume
-import android.provider.MediaStore
-import androidx.annotation.RequiresApi
-import androidx.core.database.getIntOrNull
-import androidx.core.database.getStringOrNull
-import java.io.File
-import org.oxycblt.auxio.music.MusicSettings
-import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.parsing.parseId3v2Position
-import org.oxycblt.auxio.music.storage.Directory
-import org.oxycblt.auxio.music.storage.contentResolverSafe
-import org.oxycblt.auxio.music.storage.directoryCompat
-import org.oxycblt.auxio.music.storage.mediaStoreVolumeNameCompat
-import org.oxycblt.auxio.music.storage.safeQuery
-import org.oxycblt.auxio.music.storage.storageVolumesCompat
-import org.oxycblt.auxio.music.storage.useQuery
-import org.oxycblt.auxio.music.tags.Date
-import org.oxycblt.auxio.util.getSystemServiceCompat
-import org.oxycblt.auxio.util.logD
-import org.oxycblt.auxio.util.nonZeroOrNull
-
-/**
- * The layer that loads music from the [MediaStore] database. This is an intermediate step in the
- * music extraction process and primarily intended for redundancy for files not natively supported
- * by [MetadataExtractor]. Solely relying on this is not recommended, as it often produces bad
- * metadata.
- * @param context [Context] required to query the media database.
- * @param cacheExtractor [CacheExtractor] implementation for cache optimizations.
- * @author Alexander Capehart (OxygenCobalt)
- */
-abstract class MediaStoreExtractor(
-    private val context: Context,
-    private val cacheExtractor: CacheExtractor
-) {
-    private var cursor: Cursor? = null
-    private var idIndex = -1
-    private var titleIndex = -1
-    private var displayNameIndex = -1
-    private var mimeTypeIndex = -1
-    private var sizeIndex = -1
-    private var dateAddedIndex = -1
-    private var dateModifiedIndex = -1
-    private var durationIndex = -1
-    private var yearIndex = -1
-    private var albumIndex = -1
-    private var albumIdIndex = -1
-    private var artistIndex = -1
-    private var albumArtistIndex = -1
-    private val genreNamesMap = mutableMapOf<Long, String>()
-
-    /**
-     * The [StorageVolume]s currently scanned by [MediaStore]. This should be used to transform path
-     * information from the database into volume-aware paths.
-     */
-    protected var volumes = listOf<StorageVolume>()
-        private set
-
-    /**
-     * Initialize this instance. This involves setting up the required sub-extractors and querying
-     * the media database for music files.
-     * @return A [Cursor] of the music data returned from the database.
-     */
-    open fun init(): Cursor {
-        val start = System.currentTimeMillis()
-        cacheExtractor.init()
-        val musicSettings = MusicSettings.from(context)
-        val storageManager = context.getSystemServiceCompat(StorageManager::class)
-
-        val args = mutableListOf<String>()
-        var selector = BASE_SELECTOR
-
-        // Filter out audio that is not music, if enabled.
-        if (musicSettings.excludeNonMusic) {
-            logD("Excluding non-music")
-            selector += " AND ${MediaStore.Audio.AudioColumns.IS_MUSIC}=1"
-        }
-
-        // Set up the projection to follow the music directory configuration.
-        val dirs = musicSettings.musicDirs
-        if (dirs.dirs.isNotEmpty()) {
-            selector += " AND "
-            if (!dirs.shouldInclude) {
-                // Without a NOT, the query will be restricted to the specified paths, resulting
-                // in the "Include" mode. With a NOT, the specified paths will not be included,
-                // resulting in the "Exclude" mode.
-                selector += "NOT "
-            }
-            selector += " ("
-
-            // Specifying the paths to filter is version-specific, delegate to the concrete
-            // implementations.
-            for (i in dirs.dirs.indices) {
-                if (addDirToSelector(dirs.dirs[i], args)) {
-                    selector +=
-                        if (i < dirs.dirs.lastIndex) {
-                            "$dirSelectorTemplate OR "
-                        } else {
-                            dirSelectorTemplate
-                        }
-                }
-            }
-
-            selector += ')'
-        }
-
-        // Now we can actually query MediaStore.
-        logD("Starting song query [proj: ${projection.toList()}, selector: $selector, args: $args]")
-        val cursor =
-            context.contentResolverSafe
-                .safeQuery(
-                    MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
-                    projection,
-                    selector,
-                    args.toTypedArray())
-                .also { cursor = it }
-        logD("Song query succeeded [Projected total: ${cursor.count}]")
-
-        // Set up cursor indices for later use.
-        idIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns._ID)
-        titleIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.TITLE)
-        displayNameIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DISPLAY_NAME)
-        mimeTypeIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.MIME_TYPE)
-        sizeIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.SIZE)
-        dateAddedIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DATE_ADDED)
-        dateModifiedIndex =
-            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DATE_MODIFIED)
-        durationIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DURATION)
-        yearIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.YEAR)
-        albumIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.ALBUM)
-        albumIdIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.ALBUM_ID)
-        artistIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.ARTIST)
-        albumArtistIndex = cursor.getColumnIndexOrThrow(AUDIO_COLUMN_ALBUM_ARTIST)
-
-        // Since we can't obtain the genre tag from a song query, we must construct our own
-        // equivalent from genre database queries. Theoretically, this isn't needed since
-        // MetadataLayer will fill this in for us, but I'd imagine there are some obscure
-        // formats where genre support is only really covered by this, so we are forced to
-        // bite the O(n^2) complexity here.
-        context.contentResolverSafe.useQuery(
-            MediaStore.Audio.Genres.EXTERNAL_CONTENT_URI,
-            arrayOf(MediaStore.Audio.Genres._ID, MediaStore.Audio.Genres.NAME)) { genreCursor ->
-            val idIndex = genreCursor.getColumnIndexOrThrow(MediaStore.Audio.Genres._ID)
-            val nameIndex = genreCursor.getColumnIndexOrThrow(MediaStore.Audio.Genres.NAME)
-
-            while (genreCursor.moveToNext()) {
-                val id = genreCursor.getLong(idIndex)
-                val name = genreCursor.getStringOrNull(nameIndex) ?: continue
-
-                context.contentResolverSafe.useQuery(
-                    MediaStore.Audio.Genres.Members.getContentUri(VOLUME_EXTERNAL, id),
-                    arrayOf(MediaStore.Audio.Genres.Members._ID)) { cursor ->
-                    val songIdIndex =
-                        cursor.getColumnIndexOrThrow(MediaStore.Audio.Genres.Members._ID)
-
-                    while (cursor.moveToNext()) {
-                        // Assume that a song can't inhabit multiple genre entries, as I doubt
-                        // MediaStore is actually aware that songs can have multiple genres.
-                        genreNamesMap[cursor.getLong(songIdIndex)] = name
-                    }
-                }
-            }
-        }
-
-        volumes = storageManager.storageVolumesCompat
-        logD("Finished initialization in ${System.currentTimeMillis() - start}ms")
-
-        return cursor
-    }
-
-    /**
-     * Finalize the Extractor by writing the newly-loaded [Song.Raw]s back into the cache, alongside
-     * freeing up memory.
-     * @param rawSongs The songs to write into the cache.
-     */
-    fun finalize(rawSongs: List<Song.Raw>) {
-        // Free the cursor (and it's resources)
-        cursor?.close()
-        cursor = null
-        cacheExtractor.finalize(rawSongs)
-    }
-
-    /**
-     * Populate a [Song.Raw] with the next [Cursor] value provided by [MediaStore].
-     * @param raw The [Song.Raw] to populate.
-     * @return An [ExtractionResult] signifying the result of the operation. Will return
-     * [ExtractionResult.CACHED] if [CacheExtractor] returned it.
-     */
-    fun populate(raw: Song.Raw): ExtractionResult {
-        val cursor = requireNotNull(cursor) { "MediaStoreLayer is not properly initialized" }
-        // Move to the next cursor, stopping if we have exhausted it.
-        if (!cursor.moveToNext()) {
-            logD("Cursor is exhausted")
-            return ExtractionResult.NONE
-        }
-
-        // Populate the minimum required columns to maybe obtain a cache entry.
-        populateFileData(cursor, raw)
-        if (cacheExtractor.populate(raw) == ExtractionResult.CACHED) {
-            // We found a valid cache entry, no need to fully read the entry.
-            return ExtractionResult.CACHED
-        }
-
-        // Could not load entry from cache, we have to read the rest of the metadata.
-        populateMetadata(cursor, raw)
-        return ExtractionResult.PARSED
-    }
-
-    /**
-     * The database columns available to all android versions supported by Auxio. Concrete
-     * implementations can extend this projection to add version-specific columns.
-     */
-    protected open val projection: Array<String>
-        get() =
-            arrayOf(
-                // These columns are guaranteed to work on all versions of android
-                MediaStore.Audio.AudioColumns._ID,
-                MediaStore.Audio.AudioColumns.DATE_ADDED,
-                MediaStore.Audio.AudioColumns.DATE_MODIFIED,
-                MediaStore.Audio.AudioColumns.DISPLAY_NAME,
-                MediaStore.Audio.AudioColumns.SIZE,
-                MediaStore.Audio.AudioColumns.DURATION,
-                MediaStore.Audio.AudioColumns.MIME_TYPE,
-                MediaStore.Audio.AudioColumns.TITLE,
-                MediaStore.Audio.AudioColumns.YEAR,
-                MediaStore.Audio.AudioColumns.ALBUM,
-                MediaStore.Audio.AudioColumns.ALBUM_ID,
-                MediaStore.Audio.AudioColumns.ARTIST,
-                AUDIO_COLUMN_ALBUM_ARTIST)
-
-    /**
-     * The companion template to add to the projection's selector whenever arguments are added by
-     * [addDirToSelector].
-     * @see addDirToSelector
-     */
-    protected abstract val dirSelectorTemplate: String
-
-    /**
-     * Add a [Directory] to the given list of projection selector arguments.
-     * @param dir The [Directory] to add.
-     * @param args The destination list to append selector arguments to that are analogous to the
-     * given [Directory].
-     * @return true if the [Directory] was added, false otherwise.
-     * @see dirSelectorTemplate
-     */
-    protected abstract fun addDirToSelector(dir: Directory, args: MutableList<String>): Boolean
-
-    /**
-     * Populate a [Song.Raw] with the "File Data" of the given [MediaStore] [Cursor], which is the
-     * data that cannot be cached. This includes any information not intrinsic to the file and
-     * instead dependent on the file-system, which could change without invalidating the cache due
-     * to volume additions or removals.
-     * @param cursor The [Cursor] to read from.
-     * @param raw The [Song.Raw] to populate.
-     * @see populateMetadata
-     */
-    protected open fun populateFileData(cursor: Cursor, raw: Song.Raw) {
-        raw.mediaStoreId = cursor.getLong(idIndex)
-        raw.dateAdded = cursor.getLong(dateAddedIndex)
-        raw.dateModified = cursor.getLong(dateAddedIndex)
-        // Try to use the DISPLAY_NAME column to obtain a (probably sane) file name
-        // from the android system.
-        raw.fileName = cursor.getStringOrNull(displayNameIndex)
-        raw.extensionMimeType = cursor.getString(mimeTypeIndex)
-        raw.albumMediaStoreId = cursor.getLong(albumIdIndex)
-    }
-
-    /**
-     * Populate a [Song.Raw] with the Metadata of the given [MediaStore] [Cursor], which is the data
-     * about a [Song.Raw] that can be cached. This includes any information intrinsic to the file or
-     * it's file format, such as music tags.
-     * @param cursor The [Cursor] to read from.
-     * @param raw The [Song.Raw] to populate.
-     * @see populateFileData
-     */
-    protected open fun populateMetadata(cursor: Cursor, raw: Song.Raw) {
-        // Song title
-        raw.name = cursor.getString(titleIndex)
-        // Size (in bytes)
-        raw.size = cursor.getLong(sizeIndex)
-        // Duration (in milliseconds)
-        raw.durationMs = cursor.getLong(durationIndex)
-        // MediaStore only exposes the year value of a file. This is actually worse than it
-        // seems, as it means that it will not read ID3v2 TDRC tags or Vorbis DATE comments.
-        // This is one of the major weaknesses of using MediaStore, hence the redundancy layers.
-        raw.date = cursor.getStringOrNull(yearIndex)?.let(Date::from)
-        // A non-existent album name should theoretically be the name of the folder it contained
-        // in, but in practice it is more often "0" (as in /storage/emulated/0), even when it the
-        // file is not actually in the root internal storage directory. We can't do anything to
-        // fix this, really.
-        raw.albumName = cursor.getString(albumIndex)
-        // Android does not make a non-existent artist tag null, it instead fills it in
-        // as <unknown>, which makes absolutely no sense given how other columns default
-        // to null if they are not present. If this column is such, null it so that
-        // it's easier to handle later.
-        val artist = cursor.getString(artistIndex)
-        if (artist != MediaStore.UNKNOWN_STRING) {
-            raw.artistNames = listOf(artist)
-        }
-        // The album artist column is nullable and never has placeholder values.
-        cursor.getStringOrNull(albumArtistIndex)?.let { raw.albumArtistNames = listOf(it) }
-        // Get the genre value we had to query for in initialization
-        genreNamesMap[raw.mediaStoreId]?.let { raw.genreNames = listOf(it) }
-    }
-
-    private companion object {
-        /**
-         * The base selector that works across all versions of android. Does not exclude
-         * directories.
-         */
-        const val BASE_SELECTOR = "NOT ${MediaStore.Audio.Media.SIZE}=0"
-
-        /**
-         * The album artist of a song. This column has existed since at least API 21, but until API
-         * 30 it was an undocumented extension for Google Play Music. This column will work on all
-         * versions that Auxio supports.
-         */
-        @Suppress("InlinedApi")
-        const val AUDIO_COLUMN_ALBUM_ARTIST = MediaStore.Audio.AudioColumns.ALBUM_ARTIST
-
-        /**
-         * The external volume. This naming has existed since API 21, but no constant existed for it
-         * until API 29. This will work on all versions that Auxio supports.
-         */
-        @Suppress("InlinedApi") const val VOLUME_EXTERNAL = MediaStore.VOLUME_EXTERNAL
-    }
-}
-
-// Note: The separation between version-specific backends may not be the cleanest. To preserve
-// speed, we only want to add redundancy on known issues, not with possible issues.
-
-/**
- * A [MediaStoreExtractor] that completes the music loading process in a way compatible from API 21
- * onwards to API 28.
- * @param context [Context] required to query the media database.
- * @param cacheExtractor [CacheExtractor] implementation for cache optimizations.
- * @author Alexander Capehart (OxygenCobalt)
- */
-class Api21MediaStoreExtractor(context: Context, cacheExtractor: CacheExtractor) :
-    MediaStoreExtractor(context, cacheExtractor) {
-    private var trackIndex = -1
-    private var dataIndex = -1
-
-    override fun init(): Cursor {
-        val cursor = super.init()
-        // Set up cursor indices for later use.
-        trackIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.TRACK)
-        dataIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DATA)
-        return cursor
-    }
-
-    override val projection: Array<String>
-        get() =
-            super.projection +
-                arrayOf(
-                    MediaStore.Audio.AudioColumns.TRACK,
-                    // Below API 29, we are restricted to the absolute path (Called DATA by
-                    // MedaStore) when working with audio files.
-                    MediaStore.Audio.AudioColumns.DATA)
-
-    // The selector should be configured to convert the given directories instances to their
-    // absolute paths and then compare them to DATA.
-
-    override val dirSelectorTemplate: String
-        get() = "${MediaStore.Audio.Media.DATA} LIKE ?"
-
-    override fun addDirToSelector(dir: Directory, args: MutableList<String>): Boolean {
-        // "%" signifies to accept any DATA value that begins with the Directory's path,
-        // thus recursively filtering all files in the directory.
-        args.add("${dir.volume.directoryCompat ?: return false}/${dir.relativePath}%")
-        return true
-    }
-
-    override fun populateFileData(cursor: Cursor, raw: Song.Raw) {
-        super.populateFileData(cursor, raw)
-
-        val data = cursor.getString(dataIndex)
-
-        // On some OEM devices below API 29, DISPLAY_NAME may not be present. I assume
-        // that this only applies to below API 29, as beyond API 29, this column not being
-        // present would completely break the scoped storage system. Fill it in with DATA
-        // if it's not available.
-        if (raw.fileName == null) {
-            raw.fileName = data.substringAfterLast(File.separatorChar, "").ifEmpty { null }
-        }
-
-        // Find the volume that transforms the DATA column into a relative path. This is
-        // the Directory we will use.
-        val rawPath = data.substringBeforeLast(File.separatorChar)
-        for (volume in volumes) {
-            val volumePath = volume.directoryCompat ?: continue
-            val strippedPath = rawPath.removePrefix(volumePath)
-            if (strippedPath != rawPath) {
-                raw.directory = Directory.from(volume, strippedPath)
-                break
-            }
-        }
-    }
-
-    override fun populateMetadata(cursor: Cursor, raw: Song.Raw) {
-        super.populateMetadata(cursor, raw)
-        // See unpackTrackNo/unpackDiscNo for an explanation
-        // of how this column is set up.
-        val rawTrack = cursor.getIntOrNull(trackIndex)
-        if (rawTrack != null) {
-            rawTrack.unpackTrackNo()?.let { raw.track = it }
-            rawTrack.unpackDiscNo()?.let { raw.disc = it }
-        }
-    }
-}
-
-/**
- * A [MediaStoreExtractor] that implements common behavior supported from API 29 onwards.
- * @param context [Context] required to query the media database.
- * @param cacheExtractor [CacheExtractor] implementation for cache optimizations.
- * @author Alexander Capehart (OxygenCobalt)
- */
-@RequiresApi(Build.VERSION_CODES.Q)
-open class BaseApi29MediaStoreExtractor(context: Context, cacheExtractor: CacheExtractor) :
-    MediaStoreExtractor(context, cacheExtractor) {
-    private var volumeIndex = -1
-    private var relativePathIndex = -1
-
-    override fun init(): Cursor {
-        val cursor = super.init()
-        // Set up cursor indices for later use.
-        volumeIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.VOLUME_NAME)
-        relativePathIndex =
-            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.RELATIVE_PATH)
-        return cursor
-    }
-
-    override val projection: Array<String>
-        get() =
-            super.projection +
-                arrayOf(
-                    // After API 29, we now have access to the volume name and relative
-                    // path, which simplifies working with Paths significantly.
-                    MediaStore.Audio.AudioColumns.VOLUME_NAME,
-                    MediaStore.Audio.AudioColumns.RELATIVE_PATH)
-
-    // The selector should be configured to compare both the volume name and relative path
-    // of the given directories, albeit with some conversion to the analogous MediaStore
-    // column values.
-
-    override val dirSelectorTemplate: String
-        get() =
-            "(${MediaStore.Audio.AudioColumns.VOLUME_NAME} LIKE ? " +
-                "AND ${MediaStore.Audio.AudioColumns.RELATIVE_PATH} LIKE ?)"
-
-    override fun addDirToSelector(dir: Directory, args: MutableList<String>): Boolean {
-        // MediaStore uses a different naming scheme for it's volume column convert this
-        // directory's volume to it.
-        args.add(dir.volume.mediaStoreVolumeNameCompat ?: return false)
-        // "%" signifies to accept any DATA value that begins with the Directory's path,
-        // thus recursively filtering all files in the directory.
-        args.add("${dir.relativePath}%")
-        return true
-    }
-
-    override fun populateFileData(cursor: Cursor, raw: Song.Raw) {
-        super.populateFileData(cursor, raw)
-        // Find the StorageVolume whose MediaStore name corresponds to this song.
-        // This is combined with the plain relative path column to create the directory.
-        val volumeName = cursor.getString(volumeIndex)
-        val relativePath = cursor.getString(relativePathIndex)
-        val volume = volumes.find { it.mediaStoreVolumeNameCompat == volumeName }
-        if (volume != null) {
-            raw.directory = Directory.from(volume, relativePath)
-        }
-    }
-}
-
-/**
- * A [MediaStoreExtractor] that completes the music loading process in a way compatible with at API
- * 29.
- * @param context [Context] required to query the media database.
- * @param cacheExtractor [CacheExtractor] implementation for cache functionality.
- * @author Alexander Capehart (OxygenCobalt)
- */
-@RequiresApi(Build.VERSION_CODES.Q)
-open class Api29MediaStoreExtractor(context: Context, cacheExtractor: CacheExtractor) :
-    BaseApi29MediaStoreExtractor(context, cacheExtractor) {
-    private var trackIndex = -1
-
-    override fun init(): Cursor {
-        val cursor = super.init()
-        // Set up cursor indices for later use.
-        trackIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.TRACK)
-        return cursor
-    }
-
-    override val projection: Array<String>
-        get() = super.projection + arrayOf(MediaStore.Audio.AudioColumns.TRACK)
-
-    override fun populateMetadata(cursor: Cursor, raw: Song.Raw) {
-        super.populateMetadata(cursor, raw)
-        // This extractor is volume-aware, but does not support the modern track columns.
-        // Use the old column instead. See unpackTrackNo/unpackDiscNo for an explanation
-        // of how this column is set up.
-        val rawTrack = cursor.getIntOrNull(trackIndex)
-        if (rawTrack != null) {
-            rawTrack.unpackTrackNo()?.let { raw.track = it }
-            rawTrack.unpackDiscNo()?.let { raw.disc = it }
-        }
-    }
-}
-
-/**
- * A [MediaStoreExtractor] that completes the music loading process in a way compatible from API 30
- * onwards.
- * @param context [Context] required to query the media database.
- * @param cacheExtractor [CacheExtractor] implementation for cache optimizations.
- * @author Alexander Capehart (OxygenCobalt)
- */
-@RequiresApi(Build.VERSION_CODES.R)
-class Api30MediaStoreExtractor(context: Context, cacheExtractor: CacheExtractor) :
-    BaseApi29MediaStoreExtractor(context, cacheExtractor) {
-    private var trackIndex: Int = -1
-    private var discIndex: Int = -1
-
-    override fun init(): Cursor {
-        val cursor = super.init()
-        // Set up cursor indices for later use.
-        trackIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.CD_TRACK_NUMBER)
-        discIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DISC_NUMBER)
-        return cursor
-    }
-
-    override val projection: Array<String>
-        get() =
-            super.projection +
-                arrayOf(
-                    // API 30 grant us access to the superior CD_TRACK_NUMBER and DISC_NUMBER
-                    // fields, which take the place of TRACK.
-                    MediaStore.Audio.AudioColumns.CD_TRACK_NUMBER,
-                    MediaStore.Audio.AudioColumns.DISC_NUMBER)
-
-    override fun populateMetadata(cursor: Cursor, raw: Song.Raw) {
-        super.populateMetadata(cursor, raw)
-        // Both CD_TRACK_NUMBER and DISC_NUMBER tend to be formatted as they are in
-        // the tag itself, which is to say that it is formatted as NN/TT tracks, where
-        // N is the number and T is the total. Parse the number while ignoring the
-        // total, as we have no use for it.
-        cursor.getStringOrNull(trackIndex)?.parseId3v2Position()?.let { raw.track = it }
-        cursor.getStringOrNull(discIndex)?.parseId3v2Position()?.let { raw.disc = it }
-    }
-}
-
-/**
- * Unpack the track number from a combined track + disc [Int] field. These fields appear within
- * MediaStore's TRACK column, and combine the track and disc value into a single field where the
- * disc number is the 4th+ digit.
- * @return The track number extracted from the combined integer value, or null if the value was
- * zero.
- */
-private fun Int.unpackTrackNo() = mod(1000).nonZeroOrNull()
-
-/**
- * Unpack the disc number from a combined track + disc [Int] field. These fields appear within
- * MediaStore's TRACK column, and combine the track and disc value into a single field where the
- * disc number is the 4th+ digit.
- * @return The disc number extracted from the combined integer field, or null if the value was zero.
- */
-private fun Int.unpackDiscNo() = div(1000).nonZeroOrNull()

app/src/main/java/org/oxycblt/auxio/music/metadata/AudioInfo.kt

@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.metadata
+
+import android.content.Context
+import android.media.MediaExtractor
+import android.media.MediaFormat
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
+import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.storage.MimeType
+import org.oxycblt.auxio.util.logD
+import org.oxycblt.auxio.util.logE
+import org.oxycblt.auxio.util.logW
+
+/**
+ * The properties of a [Song]'s file.
+ * @param bitrateKbps The bit rate, in kilobytes-per-second. Null if it could not be parsed.
+ * @param sampleRateHz The sample rate, in hertz.
+ * @param resolvedMimeType The known mime type of the [Song] after it's file format was determined.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+data class AudioInfo(
+    val bitrateKbps: Int?,
+    val sampleRateHz: Int?,
+    val resolvedMimeType: MimeType
+) {
+    /** Implements the process of extracting [AudioInfo] from a given [Song]. */
+    interface Provider {
+        /**
+         * Extract the [AudioInfo] of a given [Song].
+         * @param song The [Song] to read.
+         * @return The [AudioInfo] of the [Song], if possible to obtain.
+         */
+        suspend fun extract(song: Song): AudioInfo
+    }
+}
+
+/**
+ * A framework-backed implementation of [AudioInfo.Provider].
+ * @param context [Context] required to read audio files.
+ */
+class AudioInfoProviderImpl @Inject constructor(@ApplicationContext private val context: Context) :
+    AudioInfo.Provider {
+
+    override suspend fun extract(song: Song): AudioInfo {
+        // While we would use ExoPlayer to extract this information, it doesn't support
+        // common data like bit rate in progressive data sources due to there being no
+        // demand. Thus, we are stuck with the inferior OS-provided MediaExtractor.
+        val extractor = MediaExtractor()
+
+        try {
+            extractor.setDataSource(context, song.uri, emptyMap())
+        } catch (e: Exception) {
+            // Can feasibly fail with invalid file formats. Note that this isn't considered
+            // an error condition in the UI, as there is still plenty of other song information
+            // that we can show.
+            logW("Unable to extract song attributes.")
+            logW(e.stackTraceToString())
+            return AudioInfo(null, null, song.mimeType)
+        }
+
+        // Get the first track from the extractor (This is basically always the only
+        // track we need to analyze).
+        val format = extractor.getTrackFormat(0)
+
+        // Accessing fields can throw an exception if the fields are not present, and
+        // the new method for using default values is not available on lower API levels.
+        // So, we are forced to handle the exception and map it to a saner null value.
+        val bitrate =
+            try {
+                // Convert bytes-per-second to kilobytes-per-second.
+                format.getInteger(MediaFormat.KEY_BIT_RATE) / 1000
+            } catch (e: NullPointerException) {
+                logD("Unable to extract bit rate field")
+                null
+            }
+
+        val sampleRate =
+            try {
+                format.getInteger(MediaFormat.KEY_SAMPLE_RATE)
+            } catch (e: NullPointerException) {
+                logE("Unable to extract sample rate field")
+                null
+            }
+
+        val resolvedMimeType =
+            if (song.mimeType.fromFormat != null) {
+                // ExoPlayer was already able to populate the format.
+                song.mimeType
+            } else {
+                // ExoPlayer couldn't populate the format somehow, populate it here.
+                val formatMimeType =
+                    try {
+                        format.getString(MediaFormat.KEY_MIME)
+                    } catch (e: NullPointerException) {
+                        logE("Unable to extract mime type field")
+                        null
+                    }
+
+                MimeType(song.mimeType.fromExtension, formatMimeType)
+            }
+
+        extractor.release()
+
+        return AudioInfo(bitrate, sampleRate, resolvedMimeType)
+    }
+}

app/src/main/java/org/oxycblt/auxio/music/metadata/Date.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.tags
+package org.oxycblt.auxio.music.metadata
 
 import android.content.Context
 import java.text.ParseException

app/src/main/java/org/oxycblt/auxio/music/metadata/Disc.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.metadata
+
+import org.oxycblt.auxio.list.Item
+
+/**
+ * A disc identifier for a song.
+ * @param number The disc number.
+ * @param name The name of the disc group, if any. Null if not present.
+ */
+class Disc(val number: Int, val name: String?) : Item, Comparable<Disc> {
+    override fun hashCode() = number.hashCode()
+    override fun equals(other: Any?) = other is Disc && number == other.number
+    override fun compareTo(other: Disc) = number.compareTo(other.number)
+}

app/src/main/java/org/oxycblt/auxio/music/metadata/MetadataModule.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.metadata
+
+import dagger.Binds
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface MetadataModule {
+    @Binds fun tagExtractor(tagExtractor: TagExtractorImpl): TagExtractor
+    @Binds fun audioInfoProvider(audioInfoProvider: AudioInfoProviderImpl): AudioInfo.Provider
+}

app/src/main/java/org/oxycblt/auxio/music/metadata/ReleaseType.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.tags
+package org.oxycblt.auxio.music.metadata
 
 import org.oxycblt.auxio.R
 
@@ -125,7 +125,7 @@ sealed class ReleaseType {
     }
 
     /**
-     * A Mix-tape. These are usually [EP]-sized releases of music made to promote an [Artist] or a
+     * A Mix-tape. These are usually [EP]-sized releases of music made to promote an Artist or a
      * future release.
      */
     object Mixtape : ReleaseType() {
@@ -141,7 +141,7 @@ sealed class ReleaseType {
         /** A release consisting of a live performance */
         LIVE,
 
-        /** A release consisting of another [Artist]s remix of a prior performance. */
+        /** A release consisting of another Artists remix of a prior performance. */
         REMIX
     }
 

app/src/main/java/org/oxycblt/auxio/music/metadata/Separators.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.parsing
+package org.oxycblt.auxio.music.metadata
 
 /**
  * Defines the allowed separator characters that can be used to delimit multi-value tags.

app/src/main/java/org/oxycblt/auxio/music/metadata/SeparatorsDialog.kt

@@ -15,13 +15,15 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.parsing
+package org.oxycblt.auxio.music.metadata
 
 import android.os.Bundle
 import android.view.LayoutInflater
 import androidx.appcompat.app.AlertDialog
 import androidx.core.view.children
 import com.google.android.material.checkbox.MaterialCheckBox
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import org.oxycblt.auxio.BuildConfig
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogSeparatorsBinding
@@ -33,7 +35,10 @@ import org.oxycblt.auxio.ui.ViewBindingDialogFragment
  * split tags with multiple values.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class SeparatorsDialog : ViewBindingDialogFragment<DialogSeparatorsBinding>() {
+    @Inject lateinit var musicSettings: MusicSettings
+
     override fun onCreateBinding(inflater: LayoutInflater) =
         DialogSeparatorsBinding.inflate(inflater)
 
@@ -42,7 +47,7 @@ class SeparatorsDialog : ViewBindingDialogFragment<DialogSeparatorsBinding>() {
             .setTitle(R.string.set_separators)
             .setNegativeButton(R.string.lbl_cancel, null)
             .setPositiveButton(R.string.lbl_save) { _, _ ->
-                MusicSettings.from(requireContext()).multiValueSeparators = getCurrentSeparators()
+                musicSettings.multiValueSeparators = getCurrentSeparators()
             }
     }
 
@@ -59,7 +64,7 @@ class SeparatorsDialog : ViewBindingDialogFragment<DialogSeparatorsBinding>() {
         // the corresponding CheckBox for each character instead of doing an iteration
         // through the separator list for each CheckBox.
         (savedInstanceState?.getString(KEY_PENDING_SEPARATORS)
-                ?: MusicSettings.from(requireContext()).multiValueSeparators)
+                ?: musicSettings.multiValueSeparators)
             .forEach {
                 when (it) {
                     Separators.COMMA -> binding.separatorComma.isChecked = true

app/src/main/java/org/oxycblt/auxio/music/metadata/TagExtractor.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Auxio Project
+ * Copyright (c) 2023 Auxio Project
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -15,103 +15,87 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.extractor
+package org.oxycblt.auxio.music.metadata
 
 import android.content.Context
 import androidx.core.text.isDigitsOnly
 import com.google.android.exoplayer2.MediaItem
 import com.google.android.exoplayer2.MetadataRetriever
-import kotlinx.coroutines.flow.flow
+import com.google.android.exoplayer2.source.DefaultMediaSourceFactory
-import org.oxycblt.auxio.music.Song
+import dagger.hilt.android.qualifiers.ApplicationContext
-import org.oxycblt.auxio.music.parsing.parseId3v2Position
+import javax.inject.Inject
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.yield
+import org.oxycblt.auxio.music.AudioOnlyExtractors
+import org.oxycblt.auxio.music.model.RawSong
 import org.oxycblt.auxio.music.storage.toAudioUri
-import org.oxycblt.auxio.music.tags.Date
 import org.oxycblt.auxio.util.logD
 import org.oxycblt.auxio.util.logW
 
 /**
  * The extractor that leverages ExoPlayer's [MetadataRetriever] API to parse metadata. This is the
  * last step in the music extraction process and is mostly responsible for papering over the bad
- * metadata that [MediaStoreExtractor] produces.
+ * metadata that other extractors produce.
  *
- * @param context [Context] required for reading audio files.
- * @param mediaStoreExtractor [MediaStoreExtractor] implementation for cache optimizations and
- * redundancy.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class MetadataExtractor(
+interface TagExtractor {
-    private val context: Context,
-    private val mediaStoreExtractor: MediaStoreExtractor
-) {
-    // We can parallelize MetadataRetriever Futures to work around it's speed issues,
-    // producing similar throughput's to other kinds of manual metadata extraction.
-    private val taskPool: Array<Task?> = arrayOfNulls(TASK_CAPACITY)
-
     /**
-     * Initialize this extractor. This actually initializes the sub-extractors that this instance
+     * Extract the metadata of songs from [incompleteSongs] and send them to [completeSongs]. Will
-     * relies on.
+     * terminate as soon as [incompleteSongs] is closed.
-     * @return The amount of music that is expected to be loaded.
+     * @param incompleteSongs A [Channel] of incomplete songs to process.
+     * @param completeSongs A [Channel] to send completed songs to.
      */
-    fun init() = mediaStoreExtractor.init().count
+    suspend fun consume(incompleteSongs: Channel<RawSong>, completeSongs: Channel<RawSong>)
+}
 
-    /**
+class TagExtractorImpl @Inject constructor(@ApplicationContext private val context: Context) :
-     * Finalize the Extractor by writing the newly-loaded [Song.Raw]s back into the cache, alongside
+    TagExtractor {
-     * freeing up memory.
+    override suspend fun consume(
-     * @param rawSongs The songs to write into the cache.
+        incompleteSongs: Channel<RawSong>,
-     */
+        completeSongs: Channel<RawSong>
-    fun finalize(rawSongs: List<Song.Raw>) = mediaStoreExtractor.finalize(rawSongs)
+    ) {
+        // We can parallelize MetadataRetriever Futures to work around it's speed issues,
+        // producing similar throughput's to other kinds of manual metadata extraction.
+        val taskPool: Array<Task?> = arrayOfNulls(TASK_CAPACITY)
 
-    /**
+        for (song in incompleteSongs) {
-     * Returns a flow that parses all [Song.Raw] instances queued by the sub-extractors. This will
-     * first delegate to the sub-extractors before parsing the metadata itself.
-     * @return A flow of [Song.Raw] instances.
-     */
-    fun extract() = flow {
-        while (true) {
-            val raw = Song.Raw()
-            when (mediaStoreExtractor.populate(raw)) {
-                ExtractionResult.NONE -> break
-                ExtractionResult.PARSED -> {}
-                ExtractionResult.CACHED -> {
-                    // Avoid running the expensive parsing process on songs we can already
-                    // restore from the cache.
-                    emit(raw)
-                    continue
-                }
-            }
-
-            // Spin until there is an open slot we can insert a task in.
             spin@ while (true) {
                 for (i in taskPool.indices) {
                     val task = taskPool[i]
                     if (task != null) {
-                        val finishedRaw = task.get()
+                        val finishedRawSong = task.get()
-                        if (finishedRaw != null) {
+                        if (finishedRawSong != null) {
-                            emit(finishedRaw)
+                            completeSongs.send(finishedRawSong)
-                            taskPool[i] = Task(context, raw)
+                            yield()
-                            break@spin
+                        } else {
+                            continue
                         }
-                    } else {
-                        taskPool[i] = Task(context, raw)
-                        break@spin
                     }
+                    taskPool[i] = Task(context, song)
+                    break@spin
                 }
             }
         }
 
-        spin@ while (true) {
+        do {
-            // Spin until all of the remaining tasks are complete.
+            var ongoingTasks = false
             for (i in taskPool.indices) {
                 val task = taskPool[i]
                 if (task != null) {
-                    val finishedRaw = task.get() ?: continue@spin
+                    val finishedRawSong = task.get()
-                    emit(finishedRaw)
+                    if (finishedRawSong != null) {
-                    taskPool[i] = null
+                        completeSongs.send(finishedRawSong)
+                        taskPool[i] = null
+                        yield()
+                    } else {
+                        ongoingTasks = true
+                    }
                 }
             }
+        } while (ongoingTasks)
 
-            break
+        completeSongs.close()
-        }
     }
 
     private companion object {
@@ -120,26 +104,26 @@ class MetadataExtractor(
 }
 
 /**
- * Wraps a [MetadataExtractor] future and processes it into a [Song.Raw] when completed.
+ * Wraps a [TagExtractor] future and processes it into a [RawSong] when completed.
  * @param context [Context] required to open the audio file.
- * @param raw [Song.Raw] to process.
+ * @param rawSong [RawSong] to process.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class Task(context: Context, private val raw: Song.Raw) {
+private class Task(context: Context, private val rawSong: RawSong) {
     // Note that we do not leverage future callbacks. This is because errors in the
     // (highly fallible) extraction process will not bubble up to Indexer when a
     // listener is used, instead crashing the app entirely.
     private val future =
         MetadataRetriever.retrieveMetadata(
-            context,
+            DefaultMediaSourceFactory(context, AudioOnlyExtractors),
             MediaItem.fromUri(
-                requireNotNull(raw.mediaStoreId) { "Invalid raw: No id" }.toAudioUri()))
+                requireNotNull(rawSong.mediaStoreId) { "Invalid raw: No id" }.toAudioUri()))
 
     /**
      * Try to get a completed song from this [Task], if it has finished processing.
-     * @return A [Song.Raw] instance if processing has completed, null otherwise.
+     * @return A [RawSong] instance if processing has completed, null otherwise.
      */
-    fun get(): Song.Raw? {
+    fun get(): RawSong? {
         if (!future.isDone) {
             // Not done yet, nothing to do.
             return null
@@ -149,13 +133,13 @@ class Task(context: Context, private val raw: Song.Raw) {
             try {
                 future.get()[0].getFormat(0)
             } catch (e: Exception) {
-                logW("Unable to extract metadata for ${raw.name}")
+                logW("Unable to extract metadata for ${rawSong.name}")
                 logW(e.stackTraceToString())
                 null
             }
         if (format == null) {
-            logD("Nothing could be extracted for ${raw.name}")
+            logD("Nothing could be extracted for ${rawSong.name}")
-            return raw
+            return rawSong
         }
 
         val metadata = format.metadata
@@ -164,28 +148,29 @@ class Task(context: Context, private val raw: Song.Raw) {
             populateWithId3v2(textTags.id3v2)
             populateWithVorbis(textTags.vorbis)
         } else {
-            logD("No metadata could be extracted for ${raw.name}")
+            logD("No metadata could be extracted for ${rawSong.name}")
         }
 
-        return raw
+        return rawSong
     }
 
     /**
-     * Complete this instance's [Song.Raw] with ID3v2 Text Identification Frames.
+     * Complete this instance's [RawSong] with ID3v2 Text Identification Frames.
      * @param textFrames A mapping between ID3v2 Text Identification Frame IDs and one or more
      * values.
      */
     private fun populateWithId3v2(textFrames: Map<String, List<String>>) {
         // Song
-        textFrames["TXXX:musicbrainz release track id"]?.let { raw.musicBrainzId = it[0] }
+        textFrames["TXXX:musicbrainz release track id"]?.let { rawSong.musicBrainzId = it.first() }
-        textFrames["TIT2"]?.let { raw.name = it[0] }
+        textFrames["TIT2"]?.let { rawSong.name = it.first() }
-        textFrames["TSOT"]?.let { raw.sortName = it[0] }
+        textFrames["TSOT"]?.let { rawSong.sortName = it.first() }
 
-        // Track. Only parse out the track number and ignore the total tracks value.
+        // Track.
-        textFrames["TRCK"]?.run { first().parseId3v2Position() }?.let { raw.track = it }
+        textFrames["TRCK"]?.run { first().parseId3v2PositionField() }?.let { rawSong.track = it }
 
-        // Disc. Only parse out the disc number and ignore the total discs value.
+        // Disc and it's subtitle name.
-        textFrames["TPOS"]?.run { first().parseId3v2Position() }?.let { raw.disc = it }
+        textFrames["TPOS"]?.run { first().parseId3v2PositionField() }?.let { rawSong.disc = it }
+        textFrames["TSST"]?.let { rawSong.subtitle = it.first() }
 
         // Dates are somewhat complicated, as not only did their semantics change from a flat year
         // value in ID3v2.3 to a full ISO-8601 date in ID3v2.4, but there are also a variety of
@@ -200,30 +185,36 @@ class Task(context: Context, private val raw: Song.Raw) {
                 ?: textFrames["TDRC"]?.run { Date.from(first()) }
                     ?: textFrames["TDRL"]?.run { Date.from(first()) }
                     ?: parseId3v23Date(textFrames))
-            ?.let { raw.date = it }
+            ?.let { rawSong.date = it }
 
         // Album
-        textFrames["TXXX:musicbrainz album id"]?.let { raw.albumMusicBrainzId = it[0] }
+        textFrames["TXXX:musicbrainz album id"]?.let { rawSong.albumMusicBrainzId = it.first() }
-        textFrames["TALB"]?.let { raw.albumName = it[0] }
+        textFrames["TALB"]?.let { rawSong.albumName = it.first() }
-        textFrames["TSOA"]?.let { raw.albumSortName = it[0] }
+        textFrames["TSOA"]?.let { rawSong.albumSortName = it.first() }
-        (textFrames["TXXX:musicbrainz album type"] ?: textFrames["GRP1"])?.let {
+        (textFrames["TXXX:musicbrainz album type"]
-            raw.releaseTypes = it
+                ?: textFrames["TXXX:releasetype"] ?: textFrames["GRP1"])
-        }
+            ?.let { rawSong.releaseTypes = it }
 
         // Artist
-        textFrames["TXXX:musicbrainz artist id"]?.let { raw.artistMusicBrainzIds = it }
+        textFrames["TXXX:musicbrainz artist id"]?.let { rawSong.artistMusicBrainzIds = it }
-        (textFrames["TXXX:artists"] ?: textFrames["TPE1"])?.let { raw.artistNames = it }
+        (textFrames["TXXX:artists"] ?: textFrames["TPE1"])?.let { rawSong.artistNames = it }
-        (textFrames["TXXX:artists_sort"] ?: textFrames["TSOP"])?.let { raw.artistSortNames = it }
+        (textFrames["TXXX:artists_sort"] ?: textFrames["TSOP"])?.let {
+            rawSong.artistSortNames = it
+        }
 
         // Album artist
-        textFrames["TXXX:musicbrainz album artist id"]?.let { raw.albumArtistMusicBrainzIds = it }
+        textFrames["TXXX:musicbrainz album artist id"]?.let {
-        (textFrames["TXXX:albumartists"] ?: textFrames["TPE2"])?.let { raw.albumArtistNames = it }
+            rawSong.albumArtistMusicBrainzIds = it
+        }
+        (textFrames["TXXX:albumartists"] ?: textFrames["TPE2"])?.let {
+            rawSong.albumArtistNames = it
+        }
         (textFrames["TXXX:albumartists_sort"] ?: textFrames["TSO2"])?.let {
-            raw.albumArtistSortNames = it
+            rawSong.albumArtistSortNames = it
         }
 
         // Genre
-        textFrames["TCON"]?.let { raw.genreNames = it }
+        textFrames["TCON"]?.let { rawSong.genreNames = it }
     }
 
     /**
@@ -243,19 +234,19 @@ class Task(context: Context, private val raw: Song.Raw) {
                 ?: textFrames["TYER"]?.run { first().toIntOrNull() } ?: return null
 
         val tdat = textFrames["TDAT"]
-        return if (tdat != null && tdat[0].length == 4 && tdat[0].isDigitsOnly()) {
+        return if (tdat != null && tdat.first().length == 4 && tdat.first().isDigitsOnly()) {
             // TDAT frames consist of a 4-digit string where the first two digits are
             // the month and the last two digits are the day.
-            val mm = tdat[0].substring(0..1).toInt()
+            val mm = tdat.first().substring(0..1).toInt()
-            val dd = tdat[0].substring(2..3).toInt()
+            val dd = tdat.first().substring(2..3).toInt()
 
             val time = textFrames["TIME"]
-            if (time != null && time[0].length == 4 && time[0].isDigitsOnly()) {
+            if (time != null && time.first().length == 4 && time.first().isDigitsOnly()) {
                 // TIME frames consist of a 4-digit string where the first two digits are
                 // the hour and the last two digits are the minutes. No second value is
                 // possible.
-                val hh = time[0].substring(0..1).toInt()
+                val hh = time.first().substring(0..1).toInt()
-                val mi = time[0].substring(2..3).toInt()
+                val mi = time.first().substring(2..3).toInt()
                 // Able to return a full date.
                 Date.from(year, mm, dd, hh, mi)
             } else {
@@ -269,22 +260,27 @@ class Task(context: Context, private val raw: Song.Raw) {
     }
 
     /**
-     * Complete this instance's [Song.Raw] with Vorbis comments.
+     * Complete this instance's [RawSong] with Vorbis comments.
      * @param comments A mapping between vorbis comment names and one or more vorbis comment values.
      */
     private fun populateWithVorbis(comments: Map<String, List<String>>) {
         // Song
-        comments["musicbrainz_releasetrackid"]?.let { raw.musicBrainzId = it[0] }
+        comments["musicbrainz_releasetrackid"]?.let { rawSong.musicBrainzId = it.first() }
-        comments["title"]?.let { raw.name = it[0] }
+        comments["title"]?.let { rawSong.name = it.first() }
-        comments["titlesort"]?.let { raw.sortName = it[0] }
+        comments["titlesort"]?.let { rawSong.sortName = it.first() }
 
-        // Track. The total tracks value is in a different comment, so we can just
+        // Track.
-        // convert the entirety of this comment into a number.
+        parseVorbisPositionField(
-        comments["tracknumber"]?.run { first().toIntOrNull() }?.let { raw.track = it }
+                comments["tracknumber"]?.first(),
+                (comments["totaltracks"] ?: comments["tracktotal"] ?: comments["trackc"])?.first())
+            ?.let { rawSong.track = it }
 
-        // Disc. The total discs value is in a different comment, so we can just
+        // Disc and it's subtitle name.
-        // convert the entirety of this comment into a number.
+        parseVorbisPositionField(
-        comments["discnumber"]?.run { first().toIntOrNull() }?.let { raw.disc = it }
+                comments["discnumber"]?.first(),
+                (comments["totaldiscs"] ?: comments["disctotal"] ?: comments["discc"])?.first())
+            ?.let { rawSong.disc = it }
+        comments["discsubtitle"]?.let { rawSong.subtitle = it.first() }
 
         // Vorbis dates are less complicated, but there are still several types
         // Our hierarchy for dates is as such:
@@ -295,27 +291,27 @@ class Task(context: Context, private val raw: Song.Raw) {
         (comments["originaldate"]?.run { Date.from(first()) }
                 ?: comments["date"]?.run { Date.from(first()) }
                     ?: comments["year"]?.run { Date.from(first()) })
-            ?.let { raw.date = it }
+            ?.let { rawSong.date = it }
 
         // Album
-        comments["musicbrainz_albumid"]?.let { raw.albumMusicBrainzId = it[0] }
+        comments["musicbrainz_albumid"]?.let { rawSong.albumMusicBrainzId = it.first() }
-        comments["album"]?.let { raw.albumName = it[0] }
+        comments["album"]?.let { rawSong.albumName = it.first() }
-        comments["albumsort"]?.let { raw.albumSortName = it[0] }
+        comments["albumsort"]?.let { rawSong.albumSortName = it.first() }
-        comments["releasetype"]?.let { raw.releaseTypes = it }
+        comments["releasetype"]?.let { rawSong.releaseTypes = it }
 
         // Artist
-        comments["musicbrainz_artistid"]?.let { raw.artistMusicBrainzIds = it }
+        comments["musicbrainz_artistid"]?.let { rawSong.artistMusicBrainzIds = it }
-        (comments["artists"] ?: comments["artist"])?.let { raw.artistNames = it }
+        (comments["artists"] ?: comments["artist"])?.let { rawSong.artistNames = it }
-        (comments["artists_sort"] ?: comments["artistsort"])?.let { raw.artistSortNames = it }
+        (comments["artists_sort"] ?: comments["artistsort"])?.let { rawSong.artistSortNames = it }
 
         // Album artist
-        comments["musicbrainz_albumartistid"]?.let { raw.albumArtistMusicBrainzIds = it }
+        comments["musicbrainz_albumartistid"]?.let { rawSong.albumArtistMusicBrainzIds = it }
-        (comments["albumartists"] ?: comments["albumartist"])?.let { raw.albumArtistNames = it }
+        (comments["albumartists"] ?: comments["albumartist"])?.let { rawSong.albumArtistNames = it }
         (comments["albumartists_sort"] ?: comments["albumartistsort"])?.let {
-            raw.albumArtistSortNames = it
+            rawSong.albumArtistSortNames = it
         }
 
         // Genre
-        comments["genre"]?.let { raw.genreNames = it }
+        comments["genre"]?.let { rawSong.genreNames = it }
     }
 }

app/src/main/java/org/oxycblt/auxio/music/metadata/TagUtil.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.parsing
+package org.oxycblt.auxio.music.metadata
 
 import org.oxycblt.auxio.music.MusicSettings
 import org.oxycblt.auxio.util.nonZeroOrNull
@@ -96,7 +96,7 @@ fun List<String>.correctWhitespace() = mapNotNull { it.correctWhitespace() }
 
 /**
  * Attempt to parse a string by the user's separator preferences.
- * @param settings [Settings] required to obtain user separator configuration.
+ * @param settings [MusicSettings] required to obtain user separator configuration.
  * @return A list of one or more [String]s that were split up by the user-defined separators.
  */
 private fun String.maybeParseBySeparators(settings: MusicSettings): List<String> {
@@ -107,12 +107,45 @@ private fun String.maybeParseBySeparators(settings: MusicSettings): List<String>
 /// --- ID3v2 PARSING ---
 
 /**
- * Parse the number out of a ID3v2-style number + total position [String] field. These fields
+ * Parse an ID3v2-style position + total [String] field. These fields consist of a number and an
- * consist of a number and an (optional) total value delimited by a /.
+ * (optional) total value delimited by a /.
- * @return The number value extracted from the string field, or null if the value could not be
+ * @return The position value extracted from the string field, or null if:
- * parsed or if the value was zero.
+ * - The position could not be parsed
+ * - The position was zeroed AND the total value was not present/zeroed
+ * @see transformPositionField
  */
-fun String.parseId3v2Position() = split('/', limit = 2)[0].toIntOrNull()?.nonZeroOrNull()
+fun String.parseId3v2PositionField() =
+    split('/', limit = 2).let {
+        transformPositionField(it[0].toIntOrNull(), it.getOrNull(1)?.toIntOrNull())
+    }
+
+/**
+ * Parse a vorbis-style position + total field. These fields consist of two fields for the position
+ * and total numbers.
+ * @param pos The position value, or null if not present.
+ * @param total The total value, if not present.
+ * @return The position value extracted from the field, or null if:
+ * - The position could not be parsed
+ * - The position was zeroed AND the total value was not present/zeroed
+ * @see transformPositionField
+ */
+fun parseVorbisPositionField(pos: String?, total: String?) =
+    transformPositionField(pos?.toIntOrNull(), total?.toIntOrNull())
+
+/**
+ * Transform a raw position + total field into a position a way that tolerates placeholder values.
+ * @param pos The position value, or null if not present.
+ * @param total The total value, if not present.
+ * @return The position value extracted from the field, or null if:
+ * - The position could not be parsed
+ * - The position was zeroed AND the total value was not present/zeroed
+ */
+fun transformPositionField(pos: Int?, total: Int?) =
+    if (pos != null && (pos > 0 || (total?.nonZeroOrNull() != null))) {
+        pos
+    } else {
+        null
+    }
 
 /**
  * Parse a multi-value genre name using ID3 rules. This will convert any ID3v1 integer

app/src/main/java/org/oxycblt/auxio/music/metadata/TextTags.kt

@@ -15,13 +15,12 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.extractor
+package org.oxycblt.auxio.music.metadata
 
 import com.google.android.exoplayer2.metadata.Metadata
 import com.google.android.exoplayer2.metadata.id3.InternalFrame
 import com.google.android.exoplayer2.metadata.id3.TextInformationFrame
 import com.google.android.exoplayer2.metadata.vorbis.VorbisComment
-import org.oxycblt.auxio.music.parsing.correctWhitespace
 
 /**
  * Processing wrapper for [Metadata] that allows organized access to text-based audio tags.

app/src/main/java/org/oxycblt/auxio/music/model/Library.kt

@@ -15,11 +15,12 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.library
+package org.oxycblt.auxio.music.model
 
 import android.content.Context
 import android.net.Uri
 import android.provider.OpenableColumns
+import org.oxycblt.auxio.list.Sort
 import org.oxycblt.auxio.music.*
 import org.oxycblt.auxio.music.storage.contentResolverSafe
 import org.oxycblt.auxio.music.storage.useQuery
@@ -29,27 +30,89 @@ import org.oxycblt.auxio.util.logD
  * Organized music library information.
  *
  * This class allows for the creation of a well-formed music library graph from raw song
- * information. It's generally not expected to create this yourself and instead use [MusicStore].
+ * information. It's generally not expected to create this yourself and instead use
+ * [MusicRepository].
  *
  * @author Alexander Capehart
  */
-class Library(rawSongs: List<Song.Raw>, settings: MusicSettings) {
+interface Library {
-    /** All [Song]s that were detected on the device. */
+    /** All [Song]s in this [Library]. */
-    val songs = Sort(Sort.Mode.ByName, true).songs(rawSongs.map { Song(it, settings) }.distinct())
+    val songs: List<Song>
-    /** All [Album]s found on the device. */
+    /** All [Album]s in this [Library]. */
-    val albums = buildAlbums(songs)
+    val albums: List<Album>
-    /** All [Artist]s found on the device. */
+    /** All [Artist]s in this [Library]. */
-    val artists = buildArtists(songs, albums)
+    val artists: List<Artist>
-    /** All [Genre]s found on the device. */
+    /** All [Genre]s in this [Library]. */
-    val genres = buildGenres(songs)
+    val genres: List<Genre>
+
+    /**
+     * Finds a [Music] item [T] in the library by it's [Music.UID].
+     * @param uid The [Music.UID] to search for.
+     * @return The [T] corresponding to the given [Music.UID], or null if nothing could be found or
+     * the [Music.UID] did not correspond to a [T].
+     */
+    fun <T : Music> find(uid: Music.UID): T?
+
+    /**
+     * Convert a [Song] from an another library into a [Song] in this [Library].
+     * @param song The [Song] to convert.
+     * @return The analogous [Song] in this [Library], or null if it does not exist.
+     */
+    fun sanitize(song: Song): Song?
+
+    /**
+     * Convert a [MusicParent] from an another library into a [MusicParent] in this [Library].
+     * @param parent The [MusicParent] to convert.
+     * @return The analogous [Album] in this [Library], or null if it does not exist.
+     */
+    fun <T : MusicParent> sanitize(parent: T): T?
+
+    /**
+     * Find a [Song] instance corresponding to the given Intent.ACTION_VIEW [Uri].
+     * @param context [Context] required to analyze the [Uri].
+     * @param uri [Uri] to search for.
+     * @return A [Song] corresponding to the given [Uri], or null if one could not be found.
+     */
+    fun findSongForUri(context: Context, uri: Uri): Song?
+
+    companion object {
+        /**
+         * Create an instance of [Library].
+         * @param rawSongs [RawSong]s to create the library out of.
+         * @param settings [MusicSettings] required.
+         */
+        fun from(rawSongs: List<RawSong>, settings: MusicSettings): Library =
+            LibraryImpl(rawSongs, settings)
+    }
+}
+
+private class LibraryImpl(rawSongs: List<RawSong>, settings: MusicSettings) : Library {
+    override val songs = buildSongs(rawSongs, settings)
+    override val albums = buildAlbums(songs, settings)
+    override val artists = buildArtists(songs, albums, settings)
+    override val genres = buildGenres(songs, settings)
 
     // Use a mapping to make finding information based on it's UID much faster.
     private val uidMap = buildMap {
-        for (music in (songs + albums + artists + genres)) {
+        songs.forEach { put(it.uid, it.finalize()) }
-            // Finalize all music in the same mapping creation loop for efficiency.
+        albums.forEach { put(it.uid, it.finalize()) }
-            music._finalize()
+        artists.forEach { put(it.uid, it.finalize()) }
-            this[music.uid] = music
+        genres.forEach { put(it.uid, it.finalize()) }
-        }
+    }
+
+    override fun equals(other: Any?) =
+        other is Library &&
+            other.songs == songs &&
+            other.albums == albums &&
+            other.artists == artists &&
+            other.genres == genres
+
+    override fun hashCode(): Int {
+        var hashCode = songs.hashCode()
+        hashCode = hashCode * 31 + albums.hashCode()
+        hashCode = hashCode * 31 + artists.hashCode()
+        hashCode = hashCode * 31 + genres.hashCode()
+        return hashCode
     }
 
     /**
@@ -58,43 +121,13 @@ class Library(rawSongs: List<Song.Raw>, settings: MusicSettings) {
      * @return The [T] corresponding to the given [Music.UID], or null if nothing could be found or
      * the [Music.UID] did not correspond to a [T].
      */
-    @Suppress("UNCHECKED_CAST") fun <T : Music> find(uid: Music.UID) = uidMap[uid] as? T
+    @Suppress("UNCHECKED_CAST") override fun <T : Music> find(uid: Music.UID) = uidMap[uid] as? T
 
-    /**
+    override fun sanitize(song: Song) = find<Song>(song.uid)
-     * Convert a [Song] from an another library into a [Song] in this [Library].
-     * @param song The [Song] to convert.
-     * @return The analogous [Song] in this [Library], or null if it does not exist.
-     */
-    fun sanitize(song: Song) = find<Song>(song.uid)
 
-    /**
+    override fun <T : MusicParent> sanitize(parent: T) = find<T>(parent.uid)
-     * Convert a [Album] from an another library into a [Album] in this [Library].
-     * @param album The [Album] to convert.
-     * @return The analogous [Album] in this [Library], or null if it does not exist.
-     */
-    fun sanitize(album: Album) = find<Album>(album.uid)
 
-    /**
+    override fun findSongForUri(context: Context, uri: Uri) =
-     * Convert a [Artist] from an another library into a [Artist] in this [Library].
-     * @param artist The [Artist] to convert.
-     * @return The analogous [Artist] in this [Library], or null if it does not exist.
-     */
-    fun sanitize(artist: Artist) = find<Artist>(artist.uid)
-
-    /**
-     * Convert a [Genre] from an another library into a [Genre] in this [Library].
-     * @param genre The [Genre] to convert.
-     * @return The analogous [Genre] in this [Library], or null if it does not exist.
-     */
-    fun sanitize(genre: Genre) = find<Genre>(genre.uid)
-
-    /**
-     * Find a [Song] instance corresponding to the given Intent.ACTION_VIEW [Uri].
-     * @param context [Context] required to analyze the [Uri].
-     * @param uri [Uri] to search for.
-     * @return A [Song] corresponding to the given [Uri], or null if one could not be found.
-     */
-    fun findSongForUri(context: Context, uri: Uri) =
         context.contentResolverSafe.useQuery(
             uri, arrayOf(OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE)) { cursor ->
             cursor.moveToFirst()
@@ -106,18 +139,30 @@ class Library(rawSongs: List<Song.Raw>, settings: MusicSettings) {
             songs.find { it.path.name == displayName && it.size == size }
         }
 
+    /**
+     * Build a list [SongImpl]s from the given [RawSong].
+     * @param rawSongs The [RawSong]s to build the [SongImpl]s from.
+     * @param settings [MusicSettings] to obtain user parsing configuration.
+     * @return A sorted list of [SongImpl]s derived from the [RawSong] that should be suitable for
+     * grouping.
+     */
+    private fun buildSongs(rawSongs: List<RawSong>, settings: MusicSettings) =
+        Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+            .songs(rawSongs.map { SongImpl(it, settings) }.distinct())
+
     /**
      * Build a list of [Album]s from the given [Song]s.
      * @param songs The [Song]s to build [Album]s from. These will be linked with their respective
      * [Album]s when created.
+     * @param settings [MusicSettings] to obtain user parsing configuration.
      * @return A non-empty list of [Album]s. These [Album]s will be incomplete and must be linked
      * with parent [Artist] instances in order to be usable.
      */
-    private fun buildAlbums(songs: List<Song>): List<Album> {
+    private fun buildAlbums(songs: List<SongImpl>, settings: MusicSettings): List<AlbumImpl> {
         // Group songs by their singular raw album, then map the raw instances and their
         // grouped songs to Album values. Album.Raw will handle the actual grouping rules.
-        val songsByAlbum = songs.groupBy { it._rawAlbum }
+        val songsByAlbum = songs.groupBy { it.rawAlbum }
-        val albums = songsByAlbum.map { Album(it.key, it.value) }
+        val albums = songsByAlbum.map { AlbumImpl(it.key, settings, it.value) }
         logD("Successfully built ${albums.size} albums")
         return albums
     }
@@ -132,28 +177,33 @@ class Library(rawSongs: List<Song.Raw>, settings: MusicSettings) {
      * @param albums The [Album]s to build [Artist]s from. One [Album] can result in the creation of
      * one or more [Artist] instances. These will be linked with their respective [Artist]s when
      * created.
+     * @param settings [MusicSettings] to obtain user parsing configuration.
      * @return A non-empty list of [Artist]s. These [Artist]s will consist of the combined groupings
      * of [Song]s and [Album]s.
      */
-    private fun buildArtists(songs: List<Song>, albums: List<Album>): List<Artist> {
+    private fun buildArtists(
+        songs: List<SongImpl>,
+        albums: List<AlbumImpl>,
+        settings: MusicSettings
+    ): List<ArtistImpl> {
         // Add every raw artist credited to each Song/Album to the grouping. This way,
         // different multi-artist combinations are not treated as different artists.
-        val musicByArtist = mutableMapOf<Artist.Raw, MutableList<Music>>()
+        val musicByArtist = mutableMapOf<RawArtist, MutableList<Music>>()
 
         for (song in songs) {
-            for (rawArtist in song._rawArtists) {
+            for (rawArtist in song.rawArtists) {
                 musicByArtist.getOrPut(rawArtist) { mutableListOf() }.add(song)
             }
         }
 
         for (album in albums) {
-            for (rawArtist in album._rawArtists) {
+            for (rawArtist in album.rawArtists) {
                 musicByArtist.getOrPut(rawArtist) { mutableListOf() }.add(album)
             }
         }
 
         // Convert the combined mapping into artist instances.
-        val artists = musicByArtist.map { Artist(it.key, it.value) }
+        val artists = musicByArtist.map { ArtistImpl(it.key, settings, it.value) }
         logD("Successfully built ${artists.size} artists")
         return artists
     }
@@ -163,20 +213,21 @@ class Library(rawSongs: List<Song.Raw>, settings: MusicSettings) {
      * @param [songs] The [Song]s to build [Genre]s from. One [Song] can result in the creation of
      * one or more [Genre] instances. These will be linked with their respective [Genre]s when
      * created.
+     * @param settings [MusicSettings] to obtain user parsing configuration.
      * @return A non-empty list of [Genre]s.
      */
-    private fun buildGenres(songs: List<Song>): List<Genre> {
+    private fun buildGenres(songs: List<SongImpl>, settings: MusicSettings): List<GenreImpl> {
         // Add every raw genre credited to each Song to the grouping. This way,
         // different multi-genre combinations are not treated as different genres.
-        val songsByGenre = mutableMapOf<Genre.Raw, MutableList<Song>>()
+        val songsByGenre = mutableMapOf<RawGenre, MutableList<SongImpl>>()
         for (song in songs) {
-            for (rawGenre in song._rawGenres) {
+            for (rawGenre in song.rawGenres) {
                 songsByGenre.getOrPut(rawGenre) { mutableListOf() }.add(song)
             }
         }
 
         // Convert the mapping into genre instances.
-        val genres = songsByGenre.map { Genre(it.key, it.value) }
+        val genres = songsByGenre.map { GenreImpl(it.key, settings, it.value) }
         logD("Successfully built ${genres.size} genres")
         return genres
     }

app/src/main/java/org/oxycblt/auxio/music/model/MusicImpl.kt

@@ -0,0 +1,542 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.model
+
+import android.content.Context
+import androidx.annotation.VisibleForTesting
+import java.security.MessageDigest
+import java.text.CollationKey
+import java.text.Collator
+import org.oxycblt.auxio.R
+import org.oxycblt.auxio.list.Sort
+import org.oxycblt.auxio.music.Album
+import org.oxycblt.auxio.music.Artist
+import org.oxycblt.auxio.music.Genre
+import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.music.MusicMode
+import org.oxycblt.auxio.music.MusicSettings
+import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.metadata.Date
+import org.oxycblt.auxio.music.metadata.Disc
+import org.oxycblt.auxio.music.metadata.ReleaseType
+import org.oxycblt.auxio.music.metadata.parseId3GenreNames
+import org.oxycblt.auxio.music.metadata.parseMultiValue
+import org.oxycblt.auxio.music.storage.MimeType
+import org.oxycblt.auxio.music.storage.Path
+import org.oxycblt.auxio.music.storage.toAudioUri
+import org.oxycblt.auxio.music.storage.toCoverUri
+import org.oxycblt.auxio.util.nonZeroOrNull
+import org.oxycblt.auxio.util.toUuidOrNull
+import org.oxycblt.auxio.util.unlikelyToBeNull
+
+/**
+ * Library-backed implementation of [Song].
+ * @param rawSong The [RawSong] to derive the member data from.
+ * @param musicSettings [MusicSettings] to for user parsing configuration.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class SongImpl(rawSong: RawSong, musicSettings: MusicSettings) : Song {
+    override val uid =
+    // Attempt to use a MusicBrainz ID first before falling back to a hashed UID.
+    rawSong.musicBrainzId?.toUuidOrNull()?.let { Music.UID.musicBrainz(MusicMode.SONGS, it) }
+            ?: Music.UID.auxio(MusicMode.SONGS) {
+                // Song UIDs are based on the raw data without parsing so that they remain
+                // consistent across music setting changes. Parents are not held up to the
+                // same standard since grouping is already inherently linked to settings.
+                update(rawSong.name)
+                update(rawSong.albumName)
+                update(rawSong.date)
+
+                update(rawSong.track)
+                update(rawSong.disc)
+
+                update(rawSong.artistNames)
+                update(rawSong.albumArtistNames)
+            }
+    override val rawName = requireNotNull(rawSong.name) { "Invalid raw: No title" }
+    override val rawSortName = rawSong.sortName
+    override val collationKey = makeCollationKey(musicSettings)
+    override fun resolveName(context: Context) = rawName
+
+    override val track = rawSong.track
+    override val disc = rawSong.disc?.let { Disc(it, rawSong.subtitle) }
+    override val date = rawSong.date
+    override val uri = requireNotNull(rawSong.mediaStoreId) { "Invalid raw: No id" }.toAudioUri()
+    override val path =
+        Path(
+            name = requireNotNull(rawSong.fileName) { "Invalid raw: No display name" },
+            parent = requireNotNull(rawSong.directory) { "Invalid raw: No parent directory" })
+    override val mimeType =
+        MimeType(
+            fromExtension =
+                requireNotNull(rawSong.extensionMimeType) { "Invalid raw: No mime type" },
+            fromFormat = null)
+    override val size = requireNotNull(rawSong.size) { "Invalid raw: No size" }
+    override val durationMs = requireNotNull(rawSong.durationMs) { "Invalid raw: No duration" }
+    override val dateAdded = requireNotNull(rawSong.dateAdded) { "Invalid raw: No date added" }
+    private var _album: AlbumImpl? = null
+    override val album: Album
+        get() = unlikelyToBeNull(_album)
+
+    // Note: Only compare by UID so songs that differ only in MBID are treated differently.
+    override fun hashCode() = uid.hashCode()
+    override fun equals(other: Any?) = other is Song && uid == other.uid
+
+    private val artistMusicBrainzIds = rawSong.artistMusicBrainzIds.parseMultiValue(musicSettings)
+    private val artistNames = rawSong.artistNames.parseMultiValue(musicSettings)
+    private val artistSortNames = rawSong.artistSortNames.parseMultiValue(musicSettings)
+    private val rawIndividualArtists =
+        artistNames.mapIndexed { i, name ->
+            RawArtist(
+                artistMusicBrainzIds.getOrNull(i)?.toUuidOrNull(),
+                name,
+                artistSortNames.getOrNull(i))
+        }
+
+    private val albumArtistMusicBrainzIds =
+        rawSong.albumArtistMusicBrainzIds.parseMultiValue(musicSettings)
+    private val albumArtistNames = rawSong.albumArtistNames.parseMultiValue(musicSettings)
+    private val albumArtistSortNames = rawSong.albumArtistSortNames.parseMultiValue(musicSettings)
+    private val rawAlbumArtists =
+        albumArtistNames.mapIndexed { i, name ->
+            RawArtist(
+                albumArtistMusicBrainzIds.getOrNull(i)?.toUuidOrNull(),
+                name,
+                albumArtistSortNames.getOrNull(i))
+        }
+
+    private val _artists = mutableListOf<ArtistImpl>()
+    override val artists: List<Artist>
+        get() = _artists
+
+    private val _genres = mutableListOf<GenreImpl>()
+    override val genres: List<Genre>
+        get() = _genres
+
+    /**
+     * The [RawAlbum] instances collated by the [Song]. This can be used to group [Song]s into an
+     * [Album].
+     */
+    val rawAlbum =
+        RawAlbum(
+            mediaStoreId = requireNotNull(rawSong.albumMediaStoreId) { "Invalid raw: No album id" },
+            musicBrainzId = rawSong.albumMusicBrainzId?.toUuidOrNull(),
+            name = requireNotNull(rawSong.albumName) { "Invalid raw: No album name" },
+            sortName = rawSong.albumSortName,
+            releaseType = ReleaseType.parse(rawSong.releaseTypes.parseMultiValue(musicSettings)),
+            rawArtists =
+                rawAlbumArtists
+                    .ifEmpty { rawIndividualArtists }
+                    .ifEmpty { listOf(RawArtist(null, null)) })
+
+    /**
+     * The [RawArtist] instances collated by the [Song]. The artists of the song take priority,
+     * followed by the album artists. If there are no artists, this field will be a single "unknown"
+     * [RawArtist]. This can be used to group up [Song]s into an [Artist].
+     */
+    val rawArtists =
+        rawIndividualArtists.ifEmpty { rawAlbumArtists }.ifEmpty { listOf(RawArtist()) }
+
+    /**
+     * The [RawGenre] instances collated by the [Song]. This can be used to group up [Song]s into a
+     * [Genre]. ID3v2 Genre names are automatically converted to their resolved names.
+     */
+    val rawGenres =
+        rawSong.genreNames
+            .parseId3GenreNames(musicSettings)
+            .map { RawGenre(it) }
+            .ifEmpty { listOf(RawGenre()) }
+
+    /**
+     * Links this [Song] with a parent [Album].
+     * @param album The parent [Album] to link to.
+     */
+    fun link(album: AlbumImpl) {
+        _album = album
+    }
+
+    /**
+     * Links this [Song] with a parent [Artist].
+     * @param artist The parent [Artist] to link to.
+     */
+    fun link(artist: ArtistImpl) {
+        _artists.add(artist)
+    }
+
+    /**
+     * Links this [Song] with a parent [Genre].
+     * @param genre The parent [Genre] to link to.
+     */
+    fun link(genre: GenreImpl) {
+        _genres.add(genre)
+    }
+
+    /**
+     * Perform final validation and organization on this instance.
+     * @return This instance upcasted to [Song].
+     */
+    fun finalize(): Song {
+        checkNotNull(_album) { "Malformed song: No album" }
+
+        check(_artists.isNotEmpty()) { "Malformed song: No artists" }
+        for (i in _artists.indices) {
+            // Non-destructively reorder the linked artists so that they align with
+            // the artist ordering within the song metadata.
+            val newIdx = _artists[i].getOriginalPositionIn(rawArtists)
+            val other = _artists[newIdx]
+            _artists[newIdx] = _artists[i]
+            _artists[i] = other
+        }
+
+        check(_genres.isNotEmpty()) { "Malformed song: No genres" }
+        for (i in _genres.indices) {
+            // Non-destructively reorder the linked genres so that they align with
+            // the genre ordering within the song metadata.
+            val newIdx = _genres[i].getOriginalPositionIn(rawGenres)
+            val other = _genres[newIdx]
+            _genres[newIdx] = _genres[i]
+            _genres[i] = other
+        }
+        return this
+    }
+}
+
+/**
+ * Library-backed implementation of [Album].
+ * @param rawAlbum The [RawAlbum] to derive the member data from.
+ * @param musicSettings [MusicSettings] to for user parsing configuration.
+ * @param songs The [Song]s that are a part of this [Album]. These items will be linked to this
+ * [Album].
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class AlbumImpl(
+    private val rawAlbum: RawAlbum,
+    musicSettings: MusicSettings,
+    override val songs: List<SongImpl>
+) : Album {
+    override val uid =
+    // Attempt to use a MusicBrainz ID first before falling back to a hashed UID.
+    rawAlbum.musicBrainzId?.let { Music.UID.musicBrainz(MusicMode.ALBUMS, it) }
+            ?: Music.UID.auxio(MusicMode.ALBUMS) {
+                // Hash based on only names despite the presence of a date to increase stability.
+                // I don't know if there is any situation where an artist will have two albums with
+                // the exact same name, but if there is, I would love to know.
+                update(rawAlbum.name)
+                update(rawAlbum.rawArtists.map { it.name })
+            }
+    override val rawName = rawAlbum.name
+    override val rawSortName = rawAlbum.sortName
+    override val collationKey = makeCollationKey(musicSettings)
+    override fun resolveName(context: Context) = rawName
+
+    override val dates = Date.Range.from(songs.mapNotNull { it.date })
+    override val releaseType = rawAlbum.releaseType ?: ReleaseType.Album(null)
+    override val coverUri = rawAlbum.mediaStoreId.toCoverUri()
+    override val durationMs: Long
+    override val dateAdded: Long
+
+    // Note: Append song contents to MusicParent equality so that Groups with
+    // the same UID but different contents are not equal.
+    override fun hashCode() = 31 * uid.hashCode() + songs.hashCode()
+    override fun equals(other: Any?) =
+        other is AlbumImpl && uid == other.uid && songs == other.songs
+
+    private val _artists = mutableListOf<ArtistImpl>()
+    override val artists: List<Artist>
+        get() = _artists
+
+    init {
+        var totalDuration: Long = 0
+        var earliestDateAdded: Long = Long.MAX_VALUE
+
+        // Do linking and value generation in the same loop for efficiency.
+        for (song in songs) {
+            song.link(this)
+            if (song.dateAdded < earliestDateAdded) {
+                earliestDateAdded = song.dateAdded
+            }
+            totalDuration += song.durationMs
+        }
+
+        durationMs = totalDuration
+        dateAdded = earliestDateAdded
+    }
+
+    /**
+     * The [RawArtist] instances collated by the [Album]. The album artists of the song take
+     * priority, followed by the artists. If there are no artists, this field will be a single
+     * "unknown" [RawArtist]. This can be used to group up [Album]s into an [Artist].
+     */
+    val rawArtists = rawAlbum.rawArtists
+
+    /**
+     * Links this [Album] with a parent [Artist].
+     * @param artist The parent [Artist] to link to.
+     */
+    fun link(artist: ArtistImpl) {
+        _artists.add(artist)
+    }
+
+    /**
+     * Perform final validation and organization on this instance.
+     * @return This instance upcasted to [Album].
+     */
+    fun finalize(): Album {
+        check(songs.isNotEmpty()) { "Malformed album: Empty" }
+        check(_artists.isNotEmpty()) { "Malformed album: No artists" }
+        for (i in _artists.indices) {
+            // Non-destructively reorder the linked artists so that they align with
+            // the artist ordering within the song metadata.
+            val newIdx = _artists[i].getOriginalPositionIn(rawArtists)
+            val other = _artists[newIdx]
+            _artists[newIdx] = _artists[i]
+            _artists[i] = other
+        }
+        return this
+    }
+}
+
+/**
+ * Library-backed implementation of [Artist].
+ * @param rawArtist The [RawArtist] to derive the member data from.
+ * @param musicSettings [MusicSettings] to for user parsing configuration.
+ * @param songAlbums A list of the [Song]s and [Album]s that are a part of this [Artist] , either
+ * through artist or album artist tags. Providing [Song]s to the artist is optional. These instances
+ * will be linked to this [Artist].
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class ArtistImpl(
+    private val rawArtist: RawArtist,
+    musicSettings: MusicSettings,
+    songAlbums: List<Music>
+) : Artist {
+    override val uid =
+    // Attempt to use a MusicBrainz ID first before falling back to a hashed UID.
+    rawArtist.musicBrainzId?.let { Music.UID.musicBrainz(MusicMode.ARTISTS, it) }
+            ?: Music.UID.auxio(MusicMode.ARTISTS) { update(rawArtist.name) }
+    override val rawName = rawArtist.name
+    override val rawSortName = rawArtist.sortName
+    override val collationKey = makeCollationKey(musicSettings)
+    override fun resolveName(context: Context) = rawName ?: context.getString(R.string.def_artist)
+    override val songs: List<Song>
+
+    override val albums: List<Album>
+    override val durationMs: Long?
+    override val isCollaborator: Boolean
+
+    // Note: Append song contents to MusicParent equality so that Groups with
+    // the same UID but different contents are not equal.
+    override fun hashCode() = 31 * uid.hashCode() + songs.hashCode()
+    override fun equals(other: Any?) =
+        other is ArtistImpl && uid == other.uid && songs == other.songs
+
+    override lateinit var genres: List<Genre>
+
+    init {
+        val distinctSongs = mutableSetOf<Song>()
+        val distinctAlbums = mutableSetOf<Album>()
+
+        var noAlbums = true
+
+        for (music in songAlbums) {
+            when (music) {
+                is SongImpl -> {
+                    music.link(this)
+                    distinctSongs.add(music)
+                    distinctAlbums.add(music.album)
+                }
+                is AlbumImpl -> {
+                    music.link(this)
+                    distinctAlbums.add(music)
+                    noAlbums = false
+                }
+                else -> error("Unexpected input music ${music::class.simpleName}")
+            }
+        }
+
+        songs = distinctSongs.toList()
+        albums = distinctAlbums.toList()
+        durationMs = songs.sumOf { it.durationMs }.nonZeroOrNull()
+        isCollaborator = noAlbums
+    }
+
+    /**
+     * Returns the original position of this [Artist]'s [RawArtist] within the given [RawArtist]
+     * list. This can be used to create a consistent ordering within child [Artist] lists based on
+     * the original tag order.
+     * @param rawArtists The [RawArtist] instances to check. It is assumed that this [Artist]'s
+     * [RawArtist] will be within the list.
+     * @return The index of the [Artist]'s [RawArtist] within the list.
+     */
+    fun getOriginalPositionIn(rawArtists: List<RawArtist>) = rawArtists.indexOf(rawArtist)
+
+    /**
+     * Perform final validation and organization on this instance.
+     * @return This instance upcasted to [Artist].
+     */
+    fun finalize(): Artist {
+        check(songs.isNotEmpty() || albums.isNotEmpty()) { "Malformed artist: Empty" }
+        genres =
+            Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+                .genres(songs.flatMapTo(mutableSetOf()) { it.genres })
+                .sortedByDescending { genre -> songs.count { it.genres.contains(genre) } }
+        return this
+    }
+}
+/**
+ * Library-backed implementation of [Genre].
+ * @param rawGenre [RawGenre] to derive the member data from.
+ * @param musicSettings [MusicSettings] to for user parsing configuration.
+ * @param songs Child [SongImpl]s of this instance.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class GenreImpl(
+    private val rawGenre: RawGenre,
+    musicSettings: MusicSettings,
+    override val songs: List<SongImpl>
+) : Genre {
+    override val uid = Music.UID.auxio(MusicMode.GENRES) { update(rawGenre.name) }
+    override val rawName = rawGenre.name
+    override val rawSortName = rawName
+    override val collationKey = makeCollationKey(musicSettings)
+    override fun resolveName(context: Context) = rawName ?: context.getString(R.string.def_genre)
+
+    override val albums: List<Album>
+    override val artists: List<Artist>
+    override val durationMs: Long
+
+    // Note: Append song contents to MusicParent equality so that Groups with
+    // the same UID but different contents are not equal.
+    override fun hashCode() = 31 * uid.hashCode() + songs.hashCode()
+    override fun equals(other: Any?) =
+        other is GenreImpl && uid == other.uid && songs == other.songs
+
+    init {
+        val distinctAlbums = mutableSetOf<Album>()
+        val distinctArtists = mutableSetOf<Artist>()
+        var totalDuration = 0L
+
+        for (song in songs) {
+            song.link(this)
+            distinctAlbums.add(song.album)
+            distinctArtists.addAll(song.artists)
+            totalDuration += song.durationMs
+        }
+
+        albums =
+            Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+                .albums(distinctAlbums)
+                .sortedByDescending { album -> album.songs.count { it.genres.contains(this) } }
+        artists = Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING).artists(distinctArtists)
+        durationMs = totalDuration
+    }
+
+    /**
+     * Returns the original position of this [Genre]'s [RawGenre] within the given [RawGenre] list.
+     * This can be used to create a consistent ordering within child [Genre] lists based on the
+     * original tag order.
+     * @param rawGenres The [RawGenre] instances to check. It is assumed that this [Genre] 's
+     * [RawGenre] will be within the list.
+     * @return The index of the [Genre]'s [RawGenre] within the list.
+     */
+    fun getOriginalPositionIn(rawGenres: List<RawGenre>) = rawGenres.indexOf(rawGenre)
+
+    /**
+     * Perform final validation and organization on this instance.
+     * @return This instance upcasted to [Genre].
+     */
+    fun finalize(): Music {
+        check(songs.isNotEmpty()) { "Malformed genre: Empty" }
+        return this
+    }
+}
+
+/**
+ * Update a [MessageDigest] with a lowercase [String].
+ * @param string The [String] to hash. If null, it will not be hashed.
+ */
+@VisibleForTesting
+fun MessageDigest.update(string: String?) {
+    if (string != null) {
+        update(string.lowercase().toByteArray())
+    } else {
+        update(0)
+    }
+}
+
+/**
+ * Update a [MessageDigest] with the string representation of a [Date].
+ * @param date The [Date] to hash. If null, nothing will be done.
+ */
+@VisibleForTesting
+fun MessageDigest.update(date: Date?) {
+    if (date != null) {
+        update(date.toString().toByteArray())
+    } else {
+        update(0)
+    }
+}
+
+/**
+ * Update a [MessageDigest] with the lowercase versions of all of the input [String]s.
+ * @param strings The [String]s to hash. If a [String] is null, it will not be hashed.
+ */
+@VisibleForTesting
+fun MessageDigest.update(strings: List<String?>) {
+    strings.forEach(::update)
+}
+
+/**
+ * Update a [MessageDigest] with the little-endian bytes of a [Int].
+ * @param n The [Int] to write. If null, nothing will be done.
+ */
+@VisibleForTesting
+fun MessageDigest.update(n: Int?) {
+    if (n != null) {
+        update(byteArrayOf(n.toByte(), n.shr(8).toByte(), n.shr(16).toByte(), n.shr(24).toByte()))
+    } else {
+        update(0)
+    }
+}
+
+/** Cached collator instance re-used with [makeCollationKey]. */
+private val COLLATOR: Collator = Collator.getInstance().apply { strength = Collator.PRIMARY }
+
+/**
+ * Provided implementation to create a [CollationKey] in the way described by [Music.collationKey].
+ * This should be used in all overrides of all [CollationKey].
+ * @param musicSettings [MusicSettings] required for user parsing configuration.
+ * @return A [CollationKey] that follows the specification described by [Music.collationKey].
+ */
+private fun Music.makeCollationKey(musicSettings: MusicSettings): CollationKey? {
+    var sortName = (rawSortName ?: rawName) ?: return null
+
+    if (musicSettings.automaticSortNames) {
+        sortName =
+            sortName.run {
+                when {
+                    length > 5 && startsWith("the ", ignoreCase = true) -> substring(4)
+                    length > 4 && startsWith("an ", ignoreCase = true) -> substring(3)
+                    length > 3 && startsWith("a ", ignoreCase = true) -> substring(2)
+                    else -> this
+                }
+            }
+    }
+
+    return COLLATOR.getCollationKey(sortName)
+}

app/src/main/java/org/oxycblt/auxio/music/model/RawMusic.kt

@@ -0,0 +1,200 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.model
+
+import java.util.UUID
+import org.oxycblt.auxio.music.*
+import org.oxycblt.auxio.music.metadata.*
+import org.oxycblt.auxio.music.storage.Directory
+
+/**
+ * Raw information about a [SongImpl] obtained from the filesystem/Extractor instances.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class RawSong(
+    /**
+     * The ID of the [SongImpl]'s audio file, obtained from MediaStore. Note that this ID is highly
+     * unstable and should only be used for accessing the audio file.
+     */
+    var mediaStoreId: Long? = null,
+    /** @see Song.dateAdded */
+    var dateAdded: Long? = null,
+    /** The latest date the [SongImpl]'s audio file was modified, as a unix epoch timestamp. */
+    var dateModified: Long? = null,
+    /** @see Song.path */
+    var fileName: String? = null,
+    /** @see Song.path */
+    var directory: Directory? = null,
+    /** @see Song.size */
+    var size: Long? = null,
+    /** @see Song.durationMs */
+    var durationMs: Long? = null,
+    /** @see Song.mimeType */
+    var extensionMimeType: String? = null,
+    /** @see Music.UID */
+    var musicBrainzId: String? = null,
+    /** @see Music.rawName */
+    var name: String? = null,
+    /** @see Music.rawSortName */
+    var sortName: String? = null,
+    /** @see Song.track */
+    var track: Int? = null,
+    /** @see Disc.number */
+    var disc: Int? = null,
+    /** @See Disc.name */
+    var subtitle: String? = null,
+    /** @see Song.date */
+    var date: Date? = null,
+    /** @see RawAlbum.mediaStoreId */
+    var albumMediaStoreId: Long? = null,
+    /** @see RawAlbum.musicBrainzId */
+    var albumMusicBrainzId: String? = null,
+    /** @see RawAlbum.name */
+    var albumName: String? = null,
+    /** @see RawAlbum.sortName */
+    var albumSortName: String? = null,
+    /** @see RawAlbum.releaseType */
+    var releaseTypes: List<String> = listOf(),
+    /** @see RawArtist.musicBrainzId */
+    var artistMusicBrainzIds: List<String> = listOf(),
+    /** @see RawArtist.name */
+    var artistNames: List<String> = listOf(),
+    /** @see RawArtist.sortName */
+    var artistSortNames: List<String> = listOf(),
+    /** @see RawArtist.musicBrainzId */
+    var albumArtistMusicBrainzIds: List<String> = listOf(),
+    /** @see RawArtist.name */
+    var albumArtistNames: List<String> = listOf(),
+    /** @see RawArtist.sortName */
+    var albumArtistSortNames: List<String> = listOf(),
+    /** @see RawGenre.name */
+    var genreNames: List<String> = listOf()
+)
+
+/**
+ * Raw information about an [AlbumImpl] obtained from the component [SongImpl] instances.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class RawAlbum(
+    /**
+     * The ID of the [AlbumImpl]'s grouping, obtained from MediaStore. Note that this ID is highly
+     * unstable and should only be used for accessing the system-provided cover art.
+     */
+    val mediaStoreId: Long,
+    /** @see Music.uid */
+    val musicBrainzId: UUID?,
+    /** @see Music.rawName */
+    val name: String,
+    /** @see Music.rawSortName */
+    val sortName: String?,
+    /** @see Album.releaseType */
+    val releaseType: ReleaseType?,
+    /** @see RawArtist.name */
+    val rawArtists: List<RawArtist>
+) {
+    // Albums are grouped as follows:
+    // - If we have a MusicBrainz ID, only group by it. This allows different Albums with the
+    // same name to be differentiated, which is common in large libraries.
+    // - If we do not have a MusicBrainz ID, compare by the lowercase album name and lowercase
+    // artist name. This allows for case-insensitive artist/album grouping, which can be common
+    // for albums/artists that have different naming (ex. "RAMMSTEIN" vs. "Rammstein").
+
+    // Cache the hash-code for HashMap efficiency.
+    private val hashCode =
+        musicBrainzId?.hashCode() ?: (31 * name.lowercase().hashCode() + rawArtists.hashCode())
+
+    override fun hashCode() = hashCode
+
+    override fun equals(other: Any?) =
+        other is RawAlbum &&
+            when {
+                musicBrainzId != null && other.musicBrainzId != null ->
+                    musicBrainzId == other.musicBrainzId
+                musicBrainzId == null && other.musicBrainzId == null ->
+                    name.equals(other.name, true) && rawArtists == other.rawArtists
+                else -> false
+            }
+}
+
+/**
+ * Raw information about an [ArtistImpl] obtained from the component [SongImpl] and [AlbumImpl]
+ * instances.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class RawArtist(
+    /** @see Music.UID */
+    val musicBrainzId: UUID? = null,
+    /** @see Music.rawName */
+    val name: String? = null,
+    /** @see Music.rawSortName */
+    val sortName: String? = null
+) {
+    // Artists are grouped as follows:
+    // - If we have a MusicBrainz ID, only group by it. This allows different Artists with the
+    // same name to be differentiated, which is common in large libraries.
+    // - If we do not have a MusicBrainz ID, compare by the lowercase name. This allows artist
+    // grouping to be case-insensitive.
+
+    // Cache the hashCode for HashMap efficiency.
+    private val hashCode = musicBrainzId?.hashCode() ?: name?.lowercase().hashCode()
+
+    // Compare names and MusicBrainz IDs in order to differentiate artists with the
+    // same name in large libraries.
+
+    override fun hashCode() = hashCode
+
+    override fun equals(other: Any?) =
+        other is RawArtist &&
+            when {
+                musicBrainzId != null && other.musicBrainzId != null ->
+                    musicBrainzId == other.musicBrainzId
+                musicBrainzId == null && other.musicBrainzId == null ->
+                    when {
+                        name != null && other.name != null -> name.equals(other.name, true)
+                        name == null && other.name == null -> true
+                        else -> false
+                    }
+                else -> false
+            }
+}
+
+/**
+ * Raw information about a [GenreImpl] obtained from the component [SongImpl] instances.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+class RawGenre(
+    /** @see Music.rawName */
+    val name: String? = null
+) {
+    // Only group by the lowercase genre name. This allows Genre grouping to be
+    // case-insensitive, which may be helpful in some libraries with different ways of
+    // formatting genres.
+
+    // Cache the hashCode for HashMap efficiency.
+    private val hashCode = name?.lowercase().hashCode()
+
+    override fun hashCode() = hashCode
+
+    override fun equals(other: Any?) =
+        other is RawGenre &&
+            when {
+                name != null && other.name != null -> name.equals(other.name, true)
+                name == null && other.name == null -> true
+                else -> false
+            }
+}

app/src/main/java/org/oxycblt/auxio/music/storage/Filesystem.kt

@@ -53,7 +53,7 @@ class Directory private constructor(val volume: StorageVolume, val relativePath:
     /**
      * Converts this [Directory] instance into an opaque document tree path. This is a huge
      * violation of the document tree URI contract, but it's also the only one can sensibly work
-     * with these uris in the UI, and it doesn't exactly matter since we never write or read
+     * with these uris in the UI, and it doesn't exactly matter since we never write or read to
      * directory.
      * @return A URI [String] abiding by the document tree specification, or null if the [Directory]
      * is not valid.
@@ -142,10 +142,9 @@ data class MimeType(val fromExtension: String, val fromFormat: String?) {
      * Resolve the mime type into a human-readable format name, such as "Ogg Vorbis".
      * @param context [Context] required to obtain human-readable strings.
      * @return A human-readable name for this mime type. Will first try [fromFormat], then falling
-     * back to [fromExtension], then falling back to the extension name, and then finally a
+     * back to [fromExtension], and then null if that fails.
-     * placeholder "No Format" string.
      */
-    fun resolveName(context: Context): String {
+    fun resolveName(context: Context): String? {
         // We try our best to produce a more readable name for the common audio formats.
         val formatName =
             when (fromFormat) {
@@ -157,6 +156,8 @@ data class MimeType(val fromExtension: String, val fromFormat: String?) {
                 MediaFormat.MIMETYPE_AUDIO_VORBIS -> R.string.cdc_vorbis
                 MediaFormat.MIMETYPE_AUDIO_OPUS -> R.string.cdc_opus
                 MediaFormat.MIMETYPE_AUDIO_FLAC -> R.string.cdc_flac
+                // TODO: Add ALAC to this as soon as I can stop using MediaFormat for
+                //  extracting metadata and just use ExoPlayer.
                 // We don't give a name to more unpopular formats.
                 else -> -1
             }
@@ -199,8 +200,6 @@ data class MimeType(val fromExtension: String, val fromFormat: String?) {
         } else {
             // Fall back to the extension if we can't find a special name for this format.
             MimeTypeMap.getSingleton().getExtensionFromMimeType(fromExtension)?.uppercase()
-            // Fall back to a placeholder if even that fails.
-            ?: context.getString(R.string.def_codec)
         }
     }
 }

app/src/main/java/org/oxycblt/auxio/music/storage/MediaStoreExtractor.kt

@@ -0,0 +1,598 @@
+/*
+ * Copyright (c) 2022 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.storage
+
+import android.content.Context
+import android.database.Cursor
+import android.os.Build
+import android.os.storage.StorageManager
+import android.provider.MediaStore
+import androidx.annotation.RequiresApi
+import androidx.core.database.getIntOrNull
+import androidx.core.database.getStringOrNull
+import java.io.File
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.yield
+import org.oxycblt.auxio.music.MusicSettings
+import org.oxycblt.auxio.music.cache.Cache
+import org.oxycblt.auxio.music.metadata.Date
+import org.oxycblt.auxio.music.metadata.parseId3v2PositionField
+import org.oxycblt.auxio.music.metadata.transformPositionField
+import org.oxycblt.auxio.music.model.RawSong
+import org.oxycblt.auxio.util.getSystemServiceCompat
+import org.oxycblt.auxio.util.logD
+
+/**
+ * The layer that loads music from the [MediaStore] database. This is an intermediate step in the
+ * music extraction process and primarily intended for redundancy for files not natively supported
+ * by other extractors. Solely relying on this is not recommended, as it often produces bad
+ * metadata.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+interface MediaStoreExtractor {
+    /**
+     * Query the media database.
+     * @return A new [Query] returned from the media database.
+     */
+    suspend fun query(): Query
+
+    /**
+     * Consume the [Cursor] loaded after [query].
+     * @param query The [Query] to consume.
+     * @param cache A [Cache] used to avoid extracting metadata for cached songs, or null if no
+     * [Cache] was available.
+     * @param incompleteSongs A channel where songs that could not be retrieved from the [Cache]
+     * should be sent to.
+     * @param completeSongs A channel where completed songs should be sent to.
+     */
+    suspend fun consume(
+        query: Query,
+        cache: Cache?,
+        incompleteSongs: Channel<RawSong>,
+        completeSongs: Channel<RawSong>
+    )
+
+    /** A black-box interface representing a query from the media database. */
+    interface Query {
+        val projectedTotal: Int
+        fun moveToNext(): Boolean
+        fun close()
+        fun populateFileInfo(rawSong: RawSong)
+        fun populateTags(rawSong: RawSong)
+    }
+
+    companion object {
+        /**
+         * Create a framework-backed instance.
+         * @param context [Context] required.
+         * @param musicSettings [MusicSettings] required.
+         * @return A new [MediaStoreExtractor] that will work best on the device's API level.
+         */
+        fun from(context: Context, musicSettings: MusicSettings): MediaStoreExtractor =
+            when {
+                Build.VERSION.SDK_INT >= Build.VERSION_CODES.R ->
+                    Api30MediaStoreExtractor(context, musicSettings)
+                Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q ->
+                    Api29MediaStoreExtractor(context, musicSettings)
+                else -> Api21MediaStoreExtractor(context, musicSettings)
+            }
+    }
+}
+
+private abstract class BaseMediaStoreExtractor(
+    protected val context: Context,
+    private val musicSettings: MusicSettings
+) : MediaStoreExtractor {
+    final override suspend fun query(): MediaStoreExtractor.Query {
+        val start = System.currentTimeMillis()
+
+        val args = mutableListOf<String>()
+        var selector = BASE_SELECTOR
+
+        // Filter out audio that is not music, if enabled.
+        if (musicSettings.excludeNonMusic) {
+            logD("Excluding non-music")
+            selector += " AND ${MediaStore.Audio.AudioColumns.IS_MUSIC}=1"
+        }
+
+        // Set up the projection to follow the music directory configuration.
+        val dirs = musicSettings.musicDirs
+        if (dirs.dirs.isNotEmpty()) {
+            selector += " AND "
+            if (!dirs.shouldInclude) {
+                // Without a NOT, the query will be restricted to the specified paths, resulting
+                // in the "Include" mode. With a NOT, the specified paths will not be included,
+                // resulting in the "Exclude" mode.
+                selector += "NOT "
+            }
+            selector += " ("
+
+            // Specifying the paths to filter is version-specific, delegate to the concrete
+            // implementations.
+            for (i in dirs.dirs.indices) {
+                if (addDirToSelector(dirs.dirs[i], args)) {
+                    selector +=
+                        if (i < dirs.dirs.lastIndex) {
+                            "$dirSelectorTemplate OR "
+                        } else {
+                            dirSelectorTemplate
+                        }
+                }
+            }
+
+            selector += ')'
+        }
+
+        // Now we can actually query MediaStore.
+        logD("Starting song query [proj: ${projection.toList()}, selector: $selector, args: $args]")
+        val cursor =
+            context.contentResolverSafe.safeQuery(
+                MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
+                projection,
+                selector,
+                args.toTypedArray())
+        logD("Song query succeeded [Projected total: ${cursor.count}]")
+
+        val genreNamesMap = mutableMapOf<Long, String>()
+
+        // Since we can't obtain the genre tag from a song query, we must construct our own
+        // equivalent from genre database queries. Theoretically, this isn't needed since
+        // MetadataLayer will fill this in for us, but I'd imagine there are some obscure
+        // formats where genre support is only really covered by this, so we are forced to
+        // bite the O(n^2) complexity here.
+        context.contentResolverSafe.useQuery(
+            MediaStore.Audio.Genres.EXTERNAL_CONTENT_URI,
+            arrayOf(MediaStore.Audio.Genres._ID, MediaStore.Audio.Genres.NAME)) { genreCursor ->
+            val idIndex = genreCursor.getColumnIndexOrThrow(MediaStore.Audio.Genres._ID)
+            val nameIndex = genreCursor.getColumnIndexOrThrow(MediaStore.Audio.Genres.NAME)
+
+            while (genreCursor.moveToNext()) {
+                val id = genreCursor.getLong(idIndex)
+                val name = genreCursor.getStringOrNull(nameIndex) ?: continue
+
+                context.contentResolverSafe.useQuery(
+                    MediaStore.Audio.Genres.Members.getContentUri(VOLUME_EXTERNAL, id),
+                    arrayOf(MediaStore.Audio.Genres.Members._ID)) { cursor ->
+                    val songIdIndex =
+                        cursor.getColumnIndexOrThrow(MediaStore.Audio.Genres.Members._ID)
+
+                    while (cursor.moveToNext()) {
+                        // Assume that a song can't inhabit multiple genre entries, as I doubt
+                        // MediaStore is actually aware that songs can have multiple genres.
+                        genreNamesMap[cursor.getLong(songIdIndex)] = name
+                    }
+                }
+            }
+        }
+
+        logD("Finished initialization in ${System.currentTimeMillis() - start}ms")
+        return wrapQuery(cursor, genreNamesMap)
+    }
+
+    final override suspend fun consume(
+        query: MediaStoreExtractor.Query,
+        cache: Cache?,
+        incompleteSongs: Channel<RawSong>,
+        completeSongs: Channel<RawSong>
+    ) {
+        while (query.moveToNext()) {
+            val rawSong = RawSong()
+            query.populateFileInfo(rawSong)
+            if (cache?.populate(rawSong) == true) {
+                completeSongs.send(rawSong)
+            } else {
+                query.populateTags(rawSong)
+                incompleteSongs.send(rawSong)
+            }
+            yield()
+        }
+        // Free the cursor and signal that no more incomplete songs will be produced by
+        // this extractor.
+        query.close()
+        incompleteSongs.close()
+    }
+
+    /**
+     * The database columns available to all android versions supported by Auxio. Concrete
+     * implementations can extend this projection to add version-specific columns.
+     */
+    protected open val projection: Array<String>
+        get() =
+            arrayOf(
+                // These columns are guaranteed to work on all versions of android
+                MediaStore.Audio.AudioColumns._ID,
+                MediaStore.Audio.AudioColumns.DATE_ADDED,
+                MediaStore.Audio.AudioColumns.DATE_MODIFIED,
+                MediaStore.Audio.AudioColumns.DISPLAY_NAME,
+                MediaStore.Audio.AudioColumns.SIZE,
+                MediaStore.Audio.AudioColumns.DURATION,
+                MediaStore.Audio.AudioColumns.MIME_TYPE,
+                MediaStore.Audio.AudioColumns.TITLE,
+                MediaStore.Audio.AudioColumns.YEAR,
+                MediaStore.Audio.AudioColumns.ALBUM,
+                MediaStore.Audio.AudioColumns.ALBUM_ID,
+                MediaStore.Audio.AudioColumns.ARTIST,
+                AUDIO_COLUMN_ALBUM_ARTIST)
+
+    /**
+     * The companion template to add to the projection's selector whenever arguments are added by
+     * [addDirToSelector].
+     * @see addDirToSelector
+     */
+    protected abstract val dirSelectorTemplate: String
+
+    /**
+     * Add a [Directory] to the given list of projection selector arguments.
+     * @param dir The [Directory] to add.
+     * @param args The destination list to append selector arguments to that are analogous to the
+     * given [Directory].
+     * @return true if the [Directory] was added, false otherwise.
+     * @see dirSelectorTemplate
+     */
+    protected abstract fun addDirToSelector(dir: Directory, args: MutableList<String>): Boolean
+
+    protected abstract fun wrapQuery(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>
+    ): MediaStoreExtractor.Query
+
+    abstract class Query(
+        protected val cursor: Cursor,
+        private val genreNamesMap: Map<Long, String>
+    ) : MediaStoreExtractor.Query {
+        private val idIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns._ID)
+        private val titleIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.TITLE)
+        private val displayNameIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DISPLAY_NAME)
+        private val mimeTypeIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.MIME_TYPE)
+        private val sizeIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.SIZE)
+        private val dateAddedIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DATE_ADDED)
+        private val dateModifiedIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DATE_MODIFIED)
+        private val durationIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DURATION)
+        private val yearIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.YEAR)
+        private val albumIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.ALBUM)
+        private val albumIdIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.ALBUM_ID)
+        private val artistIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.ARTIST)
+        private val albumArtistIndex = cursor.getColumnIndexOrThrow(AUDIO_COLUMN_ALBUM_ARTIST)
+
+        final override val projectedTotal = cursor.count
+        final override fun moveToNext() = cursor.moveToNext()
+        final override fun close() = cursor.close()
+
+        override fun populateFileInfo(rawSong: RawSong) {
+            rawSong.mediaStoreId = cursor.getLong(idIndex)
+            rawSong.dateAdded = cursor.getLong(dateAddedIndex)
+            rawSong.dateModified = cursor.getLong(dateModifiedIndex)
+            // Try to use the DISPLAY_NAME column to obtain a (probably sane) file name
+            // from the android system.
+            rawSong.fileName = cursor.getStringOrNull(displayNameIndex)
+            rawSong.extensionMimeType = cursor.getString(mimeTypeIndex)
+            rawSong.albumMediaStoreId = cursor.getLong(albumIdIndex)
+        }
+
+        override fun populateTags(rawSong: RawSong) {
+            // Song title
+            rawSong.name = cursor.getString(titleIndex)
+            // Size (in bytes)
+            rawSong.size = cursor.getLong(sizeIndex)
+            // Duration (in milliseconds)
+            rawSong.durationMs = cursor.getLong(durationIndex)
+            // MediaStore only exposes the year value of a file. This is actually worse than it
+            // seems, as it means that it will not read ID3v2 TDRC tags or Vorbis DATE comments.
+            // This is one of the major weaknesses of using MediaStore, hence the redundancy layers.
+            rawSong.date = cursor.getStringOrNull(yearIndex)?.let(Date::from)
+            // A non-existent album name should theoretically be the name of the folder it contained
+            // in, but in practice it is more often "0" (as in /storage/emulated/0), even when it
+            // the
+            // file is not actually in the root internal storage directory. We can't do anything to
+            // fix this, really.
+            rawSong.albumName = cursor.getString(albumIndex)
+            // Android does not make a non-existent artist tag null, it instead fills it in
+            // as <unknown>, which makes absolutely no sense given how other columns default
+            // to null if they are not present. If this column is such, null it so that
+            // it's easier to handle later.
+            val artist = cursor.getString(artistIndex)
+            if (artist != MediaStore.UNKNOWN_STRING) {
+                rawSong.artistNames = listOf(artist)
+            }
+            // The album artist column is nullable and never has placeholder values.
+            cursor.getStringOrNull(albumArtistIndex)?.let { rawSong.albumArtistNames = listOf(it) }
+            // Get the genre value we had to query for in initialization
+            genreNamesMap[rawSong.mediaStoreId]?.let { rawSong.genreNames = listOf(it) }
+        }
+    }
+
+    companion object {
+        /**
+         * The base selector that works across all versions of android. Does not exclude
+         * directories.
+         */
+        private const val BASE_SELECTOR = "NOT ${MediaStore.Audio.Media.SIZE}=0"
+
+        /**
+         * The album artist of a song. This column has existed since at least API 21, but until API
+         * 30 it was an undocumented extension for Google Play Music. This column will work on all
+         * versions that Auxio supports.
+         */
+        @Suppress("InlinedApi")
+        private const val AUDIO_COLUMN_ALBUM_ARTIST = MediaStore.Audio.AudioColumns.ALBUM_ARTIST
+
+        /**
+         * The external volume. This naming has existed since API 21, but no constant existed for it
+         * until API 29. This will work on all versions that Auxio supports.
+         */
+        @Suppress("InlinedApi") private const val VOLUME_EXTERNAL = MediaStore.VOLUME_EXTERNAL
+    }
+}
+
+// Note: The separation between version-specific backends may not be the cleanest. To preserve
+// speed, we only want to add redundancy on known issues, not with possible issues.
+
+// Note: The separation between version-specific backends may not be the cleanest. To preserve
+// speed, we only want to add redundancy on known issues, not with possible issues.
+
+private class Api21MediaStoreExtractor(context: Context, musicSettings: MusicSettings) :
+    BaseMediaStoreExtractor(context, musicSettings) {
+    override val projection: Array<String>
+        get() =
+            super.projection +
+                arrayOf(
+                    MediaStore.Audio.AudioColumns.TRACK,
+                    // Below API 29, we are restricted to the absolute path (Called DATA by
+                    // MedaStore) when working with audio files.
+                    MediaStore.Audio.AudioColumns.DATA)
+
+    // The selector should be configured to convert the given directories instances to their
+    // absolute paths and then compare them to DATA.
+
+    override val dirSelectorTemplate: String
+        get() = "${MediaStore.Audio.Media.DATA} LIKE ?"
+
+    override fun addDirToSelector(dir: Directory, args: MutableList<String>): Boolean {
+        // "%" signifies to accept any DATA value that begins with the Directory's path,
+        // thus recursively filtering all files in the directory.
+        args.add("${dir.volume.directoryCompat ?: return false}/${dir.relativePath}%")
+        return true
+    }
+
+    override fun wrapQuery(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>,
+    ): MediaStoreExtractor.Query =
+        Query(cursor, genreNamesMap, context.getSystemServiceCompat(StorageManager::class))
+
+    private class Query(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>,
+        storageManager: StorageManager
+    ) : BaseMediaStoreExtractor.Query(cursor, genreNamesMap) {
+        // Set up cursor indices for later use.
+        private val trackIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.TRACK)
+        private val dataIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DATA)
+        private val volumes = storageManager.storageVolumesCompat
+
+        override fun populateFileInfo(rawSong: RawSong) {
+            super.populateFileInfo(rawSong)
+
+            val data = cursor.getString(dataIndex)
+            // On some OEM devices below API 29, DISPLAY_NAME may not be present. I assume
+            // that this only applies to below API 29, as beyond API 29, this column not being
+            // present would completely break the scoped storage system. Fill it in with DATA
+            // if it's not available.
+            if (rawSong.fileName == null) {
+                rawSong.fileName = data.substringAfterLast(File.separatorChar, "").ifEmpty { null }
+            }
+
+            // Find the volume that transforms the DATA column into a relative path. This is
+            // the Directory we will use.
+            val rawPath = data.substringBeforeLast(File.separatorChar)
+            for (volume in volumes) {
+                val volumePath = volume.directoryCompat ?: continue
+                val strippedPath = rawPath.removePrefix(volumePath)
+                if (strippedPath != rawPath) {
+                    rawSong.directory = Directory.from(volume, strippedPath)
+                    break
+                }
+            }
+        }
+
+        override fun populateTags(rawSong: RawSong) {
+            super.populateTags(rawSong)
+            // See unpackTrackNo/unpackDiscNo for an explanation
+            // of how this column is set up.
+            val rawTrack = cursor.getIntOrNull(trackIndex)
+            if (rawTrack != null) {
+                rawTrack.unpackTrackNo()?.let { rawSong.track = it }
+                rawTrack.unpackDiscNo()?.let { rawSong.disc = it }
+            }
+        }
+    }
+}
+
+/**
+ * A [BaseMediaStoreExtractor] that implements common behavior supported from API 29 onwards.
+ * @param context [Context] required to query the media database.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+@RequiresApi(Build.VERSION_CODES.Q)
+private abstract class BaseApi29MediaStoreExtractor(
+    context: Context,
+    musicSettings: MusicSettings
+) : BaseMediaStoreExtractor(context, musicSettings) {
+    override val projection: Array<String>
+        get() =
+            super.projection +
+                arrayOf(
+                    // After API 29, we now have access to the volume name and relative
+                    // path, which simplifies working with Paths significantly.
+                    MediaStore.Audio.AudioColumns.VOLUME_NAME,
+                    MediaStore.Audio.AudioColumns.RELATIVE_PATH)
+
+    // The selector should be configured to compare both the volume name and relative path
+    // of the given directories, albeit with some conversion to the analogous MediaStore
+    // column values.
+
+    override val dirSelectorTemplate: String
+        get() =
+            "(${MediaStore.Audio.AudioColumns.VOLUME_NAME} LIKE ? " +
+                "AND ${MediaStore.Audio.AudioColumns.RELATIVE_PATH} LIKE ?)"
+
+    override fun addDirToSelector(dir: Directory, args: MutableList<String>): Boolean {
+        // MediaStore uses a different naming scheme for it's volume column convert this
+        // directory's volume to it.
+        args.add(dir.volume.mediaStoreVolumeNameCompat ?: return false)
+        // "%" signifies to accept any DATA value that begins with the Directory's path,
+        // thus recursively filtering all files in the directory.
+        args.add("${dir.relativePath}%")
+        return true
+    }
+
+    abstract class Query(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>,
+        storageManager: StorageManager
+    ) : BaseMediaStoreExtractor.Query(cursor, genreNamesMap) {
+        private val volumeIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.VOLUME_NAME)
+        private val relativePathIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.RELATIVE_PATH)
+        private val volumes = storageManager.storageVolumesCompat
+
+        final override fun populateFileInfo(rawSong: RawSong) {
+            super.populateFileInfo(rawSong)
+            // Find the StorageVolume whose MediaStore name corresponds to this song.
+            // This is combined with the plain relative path column to create the directory.
+            val volumeName = cursor.getString(volumeIndex)
+            val relativePath = cursor.getString(relativePathIndex)
+            val volume = volumes.find { it.mediaStoreVolumeNameCompat == volumeName }
+            if (volume != null) {
+                rawSong.directory = Directory.from(volume, relativePath)
+            }
+        }
+    }
+}
+
+/**
+ * A [BaseMediaStoreExtractor] that completes the music loading process in a way compatible with at
+ * API
+ * 29.
+ * @param context [Context] required to query the media database.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+@RequiresApi(Build.VERSION_CODES.Q)
+private class Api29MediaStoreExtractor(context: Context, musicSettings: MusicSettings) :
+    BaseApi29MediaStoreExtractor(context, musicSettings) {
+
+    override val projection: Array<String>
+        get() = super.projection + arrayOf(MediaStore.Audio.AudioColumns.TRACK)
+
+    override fun wrapQuery(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>
+    ): MediaStoreExtractor.Query =
+        Query(cursor, genreNamesMap, context.getSystemServiceCompat(StorageManager::class))
+
+    private class Query(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>,
+        storageManager: StorageManager
+    ) : BaseApi29MediaStoreExtractor.Query(cursor, genreNamesMap, storageManager) {
+        private val trackIndex = cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.TRACK)
+        override fun populateTags(rawSong: RawSong) {
+            super.populateTags(rawSong)
+            // This extractor is volume-aware, but does not support the modern track columns.
+            // Use the old column instead. See unpackTrackNo/unpackDiscNo for an explanation
+            // of how this column is set up.
+            val rawTrack = cursor.getIntOrNull(trackIndex)
+            if (rawTrack != null) {
+                rawTrack.unpackTrackNo()?.let { rawSong.track = it }
+                rawTrack.unpackDiscNo()?.let { rawSong.disc = it }
+            }
+        }
+    }
+}
+
+/**
+ * A [BaseMediaStoreExtractor] that completes the music loading process in a way compatible from API
+ * 30 onwards.
+ * @param context [Context] required to query the media database.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+@RequiresApi(Build.VERSION_CODES.R)
+private class Api30MediaStoreExtractor(context: Context, musicSettings: MusicSettings) :
+    BaseApi29MediaStoreExtractor(context, musicSettings) {
+    override val projection: Array<String>
+        get() =
+            super.projection +
+                arrayOf(
+                    // API 30 grant us access to the superior CD_TRACK_NUMBER and DISC_NUMBER
+                    // fields, which take the place of TRACK.
+                    MediaStore.Audio.AudioColumns.CD_TRACK_NUMBER,
+                    MediaStore.Audio.AudioColumns.DISC_NUMBER)
+
+    override fun wrapQuery(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>
+    ): MediaStoreExtractor.Query =
+        Query(cursor, genreNamesMap, context.getSystemServiceCompat(StorageManager::class))
+
+    private class Query(
+        cursor: Cursor,
+        genreNamesMap: Map<Long, String>,
+        storageManager: StorageManager
+    ) : BaseApi29MediaStoreExtractor.Query(cursor, genreNamesMap, storageManager) {
+        private val trackIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.CD_TRACK_NUMBER)
+        private val discIndex =
+            cursor.getColumnIndexOrThrow(MediaStore.Audio.AudioColumns.DISC_NUMBER)
+
+        override fun populateTags(rawSong: RawSong) {
+            super.populateTags(rawSong)
+            // Both CD_TRACK_NUMBER and DISC_NUMBER tend to be formatted as they are in
+            // the tag itself, which is to say that it is formatted as NN/TT tracks, where
+            // N is the number and T is the total. Parse the number while ignoring the
+            // total, as we have no use for it.
+            cursor.getStringOrNull(trackIndex)?.parseId3v2PositionField()?.let {
+                rawSong.track = it
+            }
+            cursor.getStringOrNull(discIndex)?.parseId3v2PositionField()?.let { rawSong.disc = it }
+        }
+    }
+}
+
+/**
+ * Unpack the track number from a combined track + disc [Int] field. These fields appear within
+ * MediaStore's TRACK column, and combine the track and disc value into a single field where the
+ * disc number is the 4th+ digit.
+ * @return The track number extracted from the combined integer value, or null if the value was
+ * zero.
+ */
+private fun Int.unpackTrackNo() = transformPositionField(mod(1000), null)
+
+/**
+ * Unpack the disc number from a combined track + disc [Int] field. These fields appear within
+ * MediaStore's TRACK column, and combine the track and disc value into a single field where the
+ * disc number is the 4th+ digit.
+ * @return The disc number extracted from the combined integer field, or null if the value was zero.
+ */
+private fun Int.unpackDiscNo() = transformPositionField(div(1000), null)

app/src/main/java/org/oxycblt/auxio/music/storage/MusicDirsDialog.kt

@@ -28,6 +28,8 @@ import androidx.activity.result.contract.ActivityResultContracts
 import androidx.appcompat.app.AlertDialog
 import androidx.core.view.ViewCompat
 import androidx.core.view.isVisible
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import org.oxycblt.auxio.BuildConfig
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogMusicDirsBinding
@@ -41,11 +43,13 @@ import org.oxycblt.auxio.util.showToast
  * Dialog that manages the music dirs setting.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class MusicDirsDialog :
     ViewBindingDialogFragment<DialogMusicDirsBinding>(), DirectoryAdapter.Listener {
     private val dirAdapter = DirectoryAdapter(this)
     private var openDocumentTreeLauncher: ActivityResultLauncher<Uri?>? = null
     private var storageManager: StorageManager? = null
+    @Inject lateinit var musicSettings: MusicSettings
 
     override fun onCreateBinding(inflater: LayoutInflater) =
         DialogMusicDirsBinding.inflate(inflater)
@@ -55,11 +59,10 @@ class MusicDirsDialog :
             .setTitle(R.string.set_dirs)
             .setNegativeButton(R.string.lbl_cancel, null)
             .setPositiveButton(R.string.lbl_save) { _, _ ->
-                val settings = MusicSettings.from(requireContext())
                 val newDirs = MusicDirectories(dirAdapter.dirs, isUiModeInclude(requireBinding()))
-                if (settings.musicDirs != newDirs) {
+                if (musicSettings.musicDirs != newDirs) {
                     logD("Committing changes")
-                    settings.musicDirs = newDirs
+                    musicSettings.musicDirs = newDirs
                 }
             }
     }
@@ -96,7 +99,7 @@ class MusicDirsDialog :
             itemAnimator = null
         }
 
-        var dirs = MusicSettings.from(context).musicDirs
+        var dirs = musicSettings.musicDirs
         if (savedInstanceState != null) {
             val pendingDirs = savedInstanceState.getStringArrayList(KEY_PENDING_DIRS)
             if (pendingDirs != null) {

app/src/main/java/org/oxycblt/auxio/music/storage/StorageModule.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.music.storage
+
+import android.content.Context
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import org.oxycblt.auxio.music.MusicSettings
+
+@Module
+@InstallIn(SingletonComponent::class)
+class StorageModule {
+    @Provides
+    fun mediaStoreExtractor(@ApplicationContext context: Context, musicSettings: MusicSettings) =
+        MediaStoreExtractor.from(context, musicSettings)
+}

app/src/main/java/org/oxycblt/auxio/music/system/Indexer.kt

@@ -22,14 +22,24 @@ import android.content.Context
 import android.content.pm.PackageManager
 import android.os.Build
 import androidx.core.content.ContextCompat
+import java.util.LinkedList
+import javax.inject.Inject
 import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.async
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import kotlinx.coroutines.yield
 import org.oxycblt.auxio.BuildConfig
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.extractor.*
+import org.oxycblt.auxio.music.cache.CacheRepository
-import org.oxycblt.auxio.music.library.Library
+import org.oxycblt.auxio.music.metadata.TagExtractor
+import org.oxycblt.auxio.music.model.Library
+import org.oxycblt.auxio.music.model.RawSong
+import org.oxycblt.auxio.music.storage.MediaStoreExtractor
 import org.oxycblt.auxio.util.logD
 import org.oxycblt.auxio.util.logE
 import org.oxycblt.auxio.util.logW
@@ -39,28 +49,20 @@ import org.oxycblt.auxio.util.logW
  *
  * This class provides low-level access into the exact state of the music loading process. **This
  * class should not be used in most cases.** It is highly volatile and provides far more information
- * than is usually needed. Use [MusicStore] instead if you do not need to work with the exact music
+ * than is usually needed. Use [MusicRepository] instead if you do not need to work with the exact
- * loading state.
+ * music loading state.
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
-class Indexer private constructor() {
+interface Indexer {
-    @Volatile private var lastResponse: Result<Library>? = null
-    @Volatile private var indexingState: Indexing? = null
-    @Volatile private var controller: Controller? = null
-    @Volatile private var listener: Listener? = null
-
     /** Whether music loading is occurring or not. */
     val isIndexing: Boolean
-        get() = indexingState != null
-
     /**
      * Whether this instance has not completed a loading process and is not currently loading music.
      * This often occurs early in an app's lifecycle, and consumers should try to avoid showing any
      * state when this flag is true.
      */
     val isIndeterminate: Boolean
-        get() = lastResponse == null && indexingState == null
 
     /**
      * Register a [Controller] for this instance. This instance will handle any commands to start
@@ -68,19 +70,7 @@ class Indexer private constructor() {
      * [Listener] methods to initialize the instance with the current state.
      * @param controller The [Controller] to register. Will do nothing if already registered.
      */
-    @Synchronized
+    fun registerController(controller: Controller)
-    fun registerController(controller: Controller) {
-        if (BuildConfig.DEBUG && this.controller != null) {
-            logW("Controller is already registered")
-            return
-        }
-
-        // Initialize the controller with the current state.
-        val currentState =
-            indexingState?.let { State.Indexing(it) } ?: lastResponse?.let { State.Complete(it) }
-        controller.onIndexerStateChanged(currentState)
-        this.controller = controller
-    }
 
     /**
      * Unregister the [Controller] from this instance, prevent it from recieving any further
@@ -88,15 +78,7 @@ class Indexer private constructor() {
      * @param controller The [Controller] to unregister. Must be the current [Controller]. Does
      * nothing if invoked by another [Controller] implementation.
      */
-    @Synchronized
+    fun unregisterController(controller: Controller)
-    fun unregisterController(controller: Controller) {
-        if (BuildConfig.DEBUG && this.controller !== controller) {
-            logW("Given controller did not match current controller")
-            return
-        }
-
-        this.controller = null
-    }
 
     /**
      * Register the [Listener] for this instance. This can be used to receive rapid-fire updates to
@@ -104,19 +86,7 @@ class Indexer private constructor() {
      * [Listener] methods to initialize the instance with the current state.
      * @param listener The [Listener] to add.
      */
-    @Synchronized
+    fun registerListener(listener: Listener)
-    fun registerListener(listener: Listener) {
-        if (BuildConfig.DEBUG && this.listener != null) {
-            logW("Listener is already registered")
-            return
-        }
-
-        // Initialize the listener with the current state.
-        val currentState =
-            indexingState?.let { State.Indexing(it) } ?: lastResponse?.let { State.Complete(it) }
-        listener.onIndexerStateChanged(currentState)
-        this.listener = listener
-    }
 
     /**
      * Unregister a [Listener] from this instance, preventing it from recieving any further updates.
@@ -124,15 +94,7 @@ class Indexer private constructor() {
      * invoked by another [Listener] implementation.
      * @see Listener
      */
-    @Synchronized
+    fun unregisterListener(listener: Listener)
-    fun unregisterListener(listener: Listener) {
-        if (BuildConfig.DEBUG && this.listener !== listener) {
-            logW("Given controller did not match current controller")
-            return
-        }
-
-        this.listener = null
-    }
 
     /**
      * Start the indexing process. This should be done from in the background from [Controller]'s
@@ -140,172 +102,25 @@ class Indexer private constructor() {
      * @param context [Context] required to load music.
      * @param withCache Whether to use the cache or not when loading. If false, the cache will still
      * be written, but no cache entries will be loaded into the new library.
+     * @param scope The [CoroutineScope] to run the indexing job in.
+     * @return The [Job] stacking the indexing status.
      */
-    suspend fun index(context: Context, withCache: Boolean) {
+    fun index(context: Context, withCache: Boolean, scope: CoroutineScope): Job
-        val result =
-            try {
-                val start = System.currentTimeMillis()
-                val library = indexImpl(context, withCache)
-                logD(
-                    "Music indexing completed successfully in " +
-                        "${System.currentTimeMillis() - start}ms")
-                Result.success(library)
-            } catch (e: CancellationException) {
-                // Got cancelled, propagate upwards to top-level co-routine.
-                logD("Loading routine was cancelled")
-                throw e
-            } catch (e: Exception) {
-                // Music loading process failed due to something we have not handled.
-                logE("Music indexing failed")
-                logE(e.stackTraceToString())
-                Result.failure(e)
-            }
-        emitCompletion(result)
-    }
 
     /**
      * Request that the music library should be reloaded. This should be used by components that do
-     * not manage the indexing process in order to signal that the [Controller] should call [index]
+     * not manage the indexing process in order to signal that the [Indexer.Controller] should call
-     * eventually.
+     * [index] eventually.
      * @param withCache Whether to use the cache when loading music. Does nothing if there is no
-     * [Controller].
+     * [Indexer.Controller].
      */
-    @Synchronized
+    fun requestReindex(withCache: Boolean)
-    fun requestReindex(withCache: Boolean) {
-        logD("Requesting reindex")
-        controller?.onStartIndexing(withCache)
-    }
 
     /**
      * Reset the current loading state to signal that the instance is not loading. This should be
      * called by [Controller] after it's indexing co-routine was cancelled.
      */
-    @Synchronized
+    fun reset()
-    fun reset() {
-        logD("Cancelling last job")
-        emitIndexing(null)
-    }
-
-    /**
-     * Internal implementation of the music loading process.
-     * @param context [Context] required to load music.
-     * @param withCache Whether to use the cache or not when loading. If false, the cache will still
-     * be written, but no cache entries will be loaded into the new library.
-     * @return A newly-loaded [Library].
-     * @throws NoPermissionException If [PERMISSION_READ_AUDIO] was not granted.
-     * @throws NoMusicException If no music was found on the device.
-     */
-    private suspend fun indexImpl(context: Context, withCache: Boolean): Library {
-        if (ContextCompat.checkSelfPermission(context, PERMISSION_READ_AUDIO) ==
-            PackageManager.PERMISSION_DENIED) {
-            // No permissions, signal that we can't do anything.
-            throw NoPermissionException()
-        }
-
-        // Create the chain of extractors. Each extractor builds on the previous and
-        // enables version-specific features in order to create the best possible music
-        // experience.
-        val cacheDatabase =
-            if (withCache) {
-                ReadWriteCacheExtractor(context)
-            } else {
-                WriteOnlyCacheExtractor(context)
-            }
-        val mediaStoreExtractor =
-            when {
-                Build.VERSION.SDK_INT >= Build.VERSION_CODES.R ->
-                    Api30MediaStoreExtractor(context, cacheDatabase)
-                Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q ->
-                    Api29MediaStoreExtractor(context, cacheDatabase)
-                else -> Api21MediaStoreExtractor(context, cacheDatabase)
-            }
-        val metadataExtractor = MetadataExtractor(context, mediaStoreExtractor)
-        val rawSongs = loadRawSongs(metadataExtractor).ifEmpty { throw NoMusicException() }
-        // Build the rest of the music library from the song list. This is much more powerful
-        // and reliable compared to using MediaStore to obtain grouping information.
-        val buildStart = System.currentTimeMillis()
-        val library = Library(rawSongs, MusicSettings.from(context))
-        logD("Successfully built library in ${System.currentTimeMillis() - buildStart}ms")
-        return library
-    }
-
-    /**
-     * Load a list of [Song]s from the device.
-     * @param metadataExtractor The completed [MetadataExtractor] instance to use to load [Song.Raw]
-     * instances.
-     * @return A possibly empty list of [Song]s. These [Song]s will be incomplete and must be linked
-     * with parent [Album], [Artist], and [Genre] items in order to be usable.
-     */
-    private suspend fun loadRawSongs(metadataExtractor: MetadataExtractor): List<Song.Raw> {
-        logD("Starting indexing process")
-        val start = System.currentTimeMillis()
-        // Start initializing the extractors. Use an indeterminate state, as there is no ETA on
-        // how long a media database query will take.
-        emitIndexing(Indexing.Indeterminate)
-        val total = metadataExtractor.init()
-        yield()
-
-        // Note: We use a set here so we can eliminate song duplicates.
-        val rawSongs = mutableListOf<Song.Raw>()
-        metadataExtractor.extract().collect { rawSong ->
-            rawSongs.add(rawSong)
-            // Now we can signal a defined progress by showing how many songs we have
-            // loaded, and the projected amount of songs we found in the library
-            // (obtained by the extractors)
-            yield()
-            emitIndexing(Indexing.Songs(rawSongs.size, total))
-        }
-
-        // Finalize the extractors with the songs we have now loaded. There is no ETA
-        // on this process, so go back to an indeterminate state.
-        emitIndexing(Indexing.Indeterminate)
-        metadataExtractor.finalize(rawSongs)
-        logD(
-            "Successfully loaded ${rawSongs.size} raw songs in ${System.currentTimeMillis() - start}ms")
-        return rawSongs
-    }
-
-    /**
-     * Emit a new [State.Indexing] state. This can be used to signal the current state of the music
-     * loading process to external code. Assumes that the callee has already checked if they have
-     * not been canceled and thus have the ability to emit a new state.
-     * @param indexing The new [Indexing] state to emit, or null if no loading process is occurring.
-     */
-    @Synchronized
-    private fun emitIndexing(indexing: Indexing?) {
-        indexingState = indexing
-        // If we have canceled the loading process, we want to revert to a previous completion
-        // whenever possible to prevent state inconsistency.
-        val state =
-            indexingState?.let { State.Indexing(it) } ?: lastResponse?.let { State.Complete(it) }
-        controller?.onIndexerStateChanged(state)
-        listener?.onIndexerStateChanged(state)
-    }
-
-    /**
-     * Emit a new [State.Complete] state. This can be used to signal the completion of the music
-     * loading process to external code. Will check if the callee has not been canceled and thus has
-     * the ability to emit a new state
-     * @param result The new [Result] to emit, representing the outcome of the music loading
-     * process.
-     */
-    private suspend fun emitCompletion(result: Result<Library>) {
-        yield()
-        // Swap to the Main thread so that downstream callbacks don't crash from being on
-        // a background thread. Does not occur in emitIndexing due to efficiency reasons.
-        withContext(Dispatchers.Main) {
-            synchronized(this) {
-                // Do not check for redundancy here, as we actually need to notify a switch
-                // from Indexing -> Complete and not Indexing -> Indexing or Complete -> Complete.
-                lastResponse = result
-                indexingState = null
-                // Signal that the music loading process has been completed.
-                val state = State.Complete(result)
-                controller?.onIndexerStateChanged(state)
-                listener?.onIndexerStateChanged(state)
-            }
-        }
-    }
 
     /** Represents the current state of [Indexer]. */
     sealed class State {
@@ -357,8 +172,8 @@ class Indexer private constructor() {
      * A listener for rapid-fire changes in the music loading state.
      *
      * This is only useful for code that absolutely must show the current loading process.
-     * Otherwise, [MusicStore.Listener] is highly recommended due to it's updates only consisting of
+     * Otherwise, [MusicRepository.Listener] is highly recommended due to it's updates only
-     * the [Library].
+     * consisting of the [Library].
      */
     interface Listener {
         /**
@@ -388,8 +203,6 @@ class Indexer private constructor() {
     }
 
     companion object {
-        @Volatile private var INSTANCE: Indexer? = null
-
         /**
          * A version-compatible identifier for the read external storage permission required by the
          * system to load audio.
@@ -401,21 +214,218 @@ class Indexer private constructor() {
             } else {
                 Manifest.permission.READ_EXTERNAL_STORAGE
             }
+    }
+}
 
-        /**
+class IndexerImpl
-         * Get a singleton instance.
+@Inject
-         * @return The (possibly newly-created) singleton instance.
+constructor(
-         */
+    private val musicSettings: MusicSettings,
-        fun getInstance(): Indexer {
+    private val cacheRepository: CacheRepository,
-            val currentInstance = INSTANCE
+    private val mediaStoreExtractor: MediaStoreExtractor,
-            if (currentInstance != null) {
+    private val tagExtractor: TagExtractor
-                return currentInstance
+) : Indexer {
+    @Volatile private var lastResponse: Result<Library>? = null
+    @Volatile private var indexingState: Indexer.Indexing? = null
+    @Volatile private var controller: Indexer.Controller? = null
+    @Volatile private var listener: Indexer.Listener? = null
+
+    override val isIndexing: Boolean
+        get() = indexingState != null
+
+    override val isIndeterminate: Boolean
+        get() = lastResponse == null && indexingState == null
+
+    @Synchronized
+    override fun registerController(controller: Indexer.Controller) {
+        if (BuildConfig.DEBUG && this.controller != null) {
+            logW("Controller is already registered")
+            return
+        }
+
+        // Initialize the controller with the current state.
+        val currentState =
+            indexingState?.let { Indexer.State.Indexing(it) }
+                ?: lastResponse?.let { Indexer.State.Complete(it) }
+        controller.onIndexerStateChanged(currentState)
+        this.controller = controller
+    }
+
+    @Synchronized
+    override fun unregisterController(controller: Indexer.Controller) {
+        if (BuildConfig.DEBUG && this.controller !== controller) {
+            logW("Given controller did not match current controller")
+            return
+        }
+
+        this.controller = null
+    }
+
+    @Synchronized
+    override fun registerListener(listener: Indexer.Listener) {
+        if (BuildConfig.DEBUG && this.listener != null) {
+            logW("Listener is already registered")
+            return
+        }
+
+        // Initialize the listener with the current state.
+        val currentState =
+            indexingState?.let { Indexer.State.Indexing(it) }
+                ?: lastResponse?.let { Indexer.State.Complete(it) }
+        listener.onIndexerStateChanged(currentState)
+        this.listener = listener
+    }
+
+    @Synchronized
+    override fun unregisterListener(listener: Indexer.Listener) {
+        if (BuildConfig.DEBUG && this.listener !== listener) {
+            logW("Given controller did not match current controller")
+            return
+        }
+
+        this.listener = null
+    }
+
+    override fun index(context: Context, withCache: Boolean, scope: CoroutineScope) =
+        scope.launch {
+            val result =
+                try {
+                    val start = System.currentTimeMillis()
+                    val library = indexImpl(context, withCache, this)
+                    logD(
+                        "Music indexing completed successfully in " +
+                            "${System.currentTimeMillis() - start}ms")
+                    Result.success(library)
+                } catch (e: CancellationException) {
+                    // Got cancelled, propagate upwards to top-level co-routine.
+                    logD("Loading routine was cancelled")
+                    throw e
+                } catch (e: Exception) {
+                    // Music loading process failed due to something we have not handled.
+                    logE("Music indexing failed")
+                    logE(e.stackTraceToString())
+                    Result.failure(e)
+                }
+            emitCompletion(result)
+        }
+
+    @Synchronized
+    override fun requestReindex(withCache: Boolean) {
+        logD("Requesting reindex")
+        controller?.onStartIndexing(withCache)
+    }
+
+    @Synchronized
+    override fun reset() {
+        logD("Cancelling last job")
+        emitIndexing(null)
+    }
+
+    private suspend fun indexImpl(
+        context: Context,
+        withCache: Boolean,
+        scope: CoroutineScope
+    ): Library {
+        if (ContextCompat.checkSelfPermission(context, Indexer.PERMISSION_READ_AUDIO) ==
+            PackageManager.PERMISSION_DENIED) {
+            logE("Permission check failed")
+            // No permissions, signal that we can't do anything.
+            throw Indexer.NoPermissionException()
+        }
+
+        // Start initializing the extractors. Use an indeterminate state, as there is no ETA on
+        // how long a media database query will take.
+        emitIndexing(Indexer.Indexing.Indeterminate)
+
+        // Do the initial query of the cache and media databases in parallel.
+        logD("Starting queries")
+        val mediaStoreQueryJob = scope.async { mediaStoreExtractor.query() }
+        val cache =
+            if (withCache) {
+                cacheRepository.readCache()
+            } else {
+                null
             }
+        val query = mediaStoreQueryJob.await()
 
+        // Now start processing the queried song information in parallel. Songs that can't be
+        // received from the cache are consisted incomplete and pushed to a separate channel
+        // that will eventually be processed into completed raw songs.
+        logD("Starting song discovery")
+        val completeSongs = Channel<RawSong>(Channel.UNLIMITED)
+        val incompleteSongs = Channel<RawSong>(Channel.UNLIMITED)
+        val mediaStoreJob =
+            scope.async {
+                mediaStoreExtractor.consume(query, cache, incompleteSongs, completeSongs)
+            }
+        val metadataJob = scope.async { tagExtractor.consume(incompleteSongs, completeSongs) }
+
+        // Await completed raw songs as they are processed.
+        val rawSongs = LinkedList<RawSong>()
+        for (rawSong in completeSongs) {
+            rawSongs.add(rawSong)
+            emitIndexing(Indexer.Indexing.Songs(rawSongs.size, query.projectedTotal))
+        }
+        // These should be no-ops
+        mediaStoreJob.await()
+        metadataJob.await()
+
+        if (rawSongs.isEmpty()) {
+            logE("Music library was empty")
+            throw Indexer.NoMusicException()
+        }
+
+        // Successfully loaded the library, now save the cache and create the library in
+        // parallel.
+        logD("Discovered ${rawSongs.size} songs, starting finalization")
+        emitIndexing(Indexer.Indexing.Indeterminate)
+        val libraryJob = scope.async(Dispatchers.Main) { Library.from(rawSongs, musicSettings) }
+        if (cache == null || cache.invalidated) {
+            cacheRepository.writeCache(rawSongs)
+        }
+        return libraryJob.await()
+    }
+
+    /**
+     * Emit a new [Indexer.State.Indexing] state. This can be used to signal the current state of
+     * the music loading process to external code. Assumes that the callee has already checked if
+     * they have not been canceled and thus have the ability to emit a new state.
+     * @param indexing The new [Indexer.Indexing] state to emit, or null if no loading process is
+     * occurring.
+     */
+    @Synchronized
+    private fun emitIndexing(indexing: Indexer.Indexing?) {
+        indexingState = indexing
+        // If we have canceled the loading process, we want to revert to a previous completion
+        // whenever possible to prevent state inconsistency.
+        val state =
+            indexingState?.let { Indexer.State.Indexing(it) }
+                ?: lastResponse?.let { Indexer.State.Complete(it) }
+        controller?.onIndexerStateChanged(state)
+        listener?.onIndexerStateChanged(state)
+    }
+
+    /**
+     * Emit a new [Indexer.State.Complete] state. This can be used to signal the completion of the
+     * music loading process to external code. Will check if the callee has not been canceled and
+     * thus has the ability to emit a new state
+     * @param result The new [Result] to emit, representing the outcome of the music loading
+     * process.
+     */
+    private suspend fun emitCompletion(result: Result<Library>) {
+        yield()
+        // Swap to the Main thread so that downstream callbacks don't crash from being on
+        // a background thread. Does not occur in emitIndexing due to efficiency reasons.
+        withContext(Dispatchers.Main) {
             synchronized(this) {
-                val newInstance = Indexer()
+                // Do not check for redundancy here, as we actually need to notify a switch
-                INSTANCE = newInstance
+                // from Indexing -> Complete and not Indexing -> Indexing or Complete -> Complete.
-                return newInstance
+                lastResponse = result
+                indexingState = null
+                // Signal that the music loading process has been completed.
+                val state = Indexer.State.Complete(result)
+                controller?.onIndexerStateChanged(state)
+                listener?.onIndexerStateChanged(state)
             }
         }
     }

app/src/main/java/org/oxycblt/auxio/music/system/IndexerService.kt

@@ -25,14 +25,15 @@ import android.os.IBinder
 import android.os.Looper
 import android.os.PowerManager
 import android.provider.MediaStore
-import coil.imageLoader
+import coil.ImageLoader
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.launch
 import org.oxycblt.auxio.BuildConfig
+import org.oxycblt.auxio.music.MusicRepository
 import org.oxycblt.auxio.music.MusicSettings
-import org.oxycblt.auxio.music.MusicStore
 import org.oxycblt.auxio.music.storage.contentResolverSafe
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
 import org.oxycblt.auxio.service.ForegroundManager
@@ -53,10 +54,13 @@ import org.oxycblt.auxio.util.logD
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
-    private val indexer = Indexer.getInstance()
+    @Inject lateinit var imageLoader: ImageLoader
-    private val musicStore = MusicStore.getInstance()
+    @Inject lateinit var musicRepository: MusicRepository
-    private val playbackManager = PlaybackStateManager.getInstance()
+    @Inject lateinit var indexer: Indexer
+    @Inject lateinit var musicSettings: MusicSettings
+    @Inject lateinit var playbackManager: PlaybackStateManager
     private val serviceJob = Job()
     private val indexScope = CoroutineScope(serviceJob + Dispatchers.IO)
     private var currentIndexJob: Job? = null
@@ -65,7 +69,6 @@ class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
     private lateinit var observingNotification: ObservingNotification
     private lateinit var wakeLock: PowerManager.WakeLock
     private lateinit var indexerContentObserver: SystemContentObserver
-    private lateinit var settings: MusicSettings
 
     override fun onCreate() {
         super.onCreate()
@@ -80,12 +83,11 @@ class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
         // Initialize any listener-dependent components last as we wouldn't want a listener race
         // condition to cause us to load music before we were fully initialize.
         indexerContentObserver = SystemContentObserver()
-        settings = MusicSettings.from(this)
+        musicSettings.registerListener(this)
-        settings.registerListener(this)
         indexer.registerController(this)
         // An indeterminate indexer and a missing library implies we are extremely early
         // in app initialization so start loading music.
-        if (musicStore.library == null && indexer.isIndeterminate) {
+        if (musicRepository.library == null && indexer.isIndeterminate) {
             logD("No library present and no previous response, indexing music now")
             onStartIndexing(true)
         }
@@ -105,7 +107,7 @@ class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
         // Then cancel the listener-dependent components to ensure that stray reloading
         // events will not occur.
         indexerContentObserver.release()
-        settings.unregisterListener(this)
+        musicSettings.unregisterListener(this)
         indexer.unregisterController(this)
         // Then cancel any remaining music loading jobs.
         serviceJob.cancel()
@@ -121,7 +123,7 @@ class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
             indexer.reset()
         }
         // Start a new music loading job on a co-routine.
-        currentIndexJob = indexScope.launch { indexer.index(this@IndexerService, withCache) }
+        currentIndexJob = indexer.index(this@IndexerService, withCache, indexScope)
     }
 
     override fun onIndexerStateChanged(state: Indexer.State?) {
@@ -129,20 +131,31 @@ class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
             is Indexer.State.Indexing -> updateActiveSession(state.indexing)
             is Indexer.State.Complete -> {
                 val newLibrary = state.result.getOrNull()
-                if (newLibrary != null && newLibrary != musicStore.library) {
+                if (newLibrary != null && newLibrary != musicRepository.library) {
                     logD("Applying new library")
                     // We only care if the newly-loaded library is going to replace a previously
                     // loaded library.
-                    if (musicStore.library != null) {
+                    if (musicRepository.library != null) {
                         // Wipe possibly-invalidated outdated covers
                         imageLoader.memoryCache?.clear()
                         // Clear invalid models from PlaybackStateManager. This is not connected
                         // to a listener as it is bad practice for a shared object to attach to
                         // the listener system of another.
-                        playbackManager.sanitize(newLibrary)
+                        playbackManager.toSavedState()?.let { savedState ->
+                            playbackManager.applySavedState(
+                                PlaybackStateManager.SavedState(
+                                    parent = savedState.parent?.let(newLibrary::sanitize),
+                                    queueState =
+                                        savedState.queueState.remap { song ->
+                                            newLibrary.sanitize(requireNotNull(song))
+                                        },
+                                    positionMs = savedState.positionMs,
+                                    repeatMode = savedState.repeatMode),
+                                true)
+                        }
                     }
                     // Forward the new library to MusicStore to continue the update process.
-                    musicStore.library = newLibrary
+                    musicRepository.library = newLibrary
                 }
                 // On errors, while we would want to show a notification that displays the
                 // error, that requires the Android 13 notification permission, which is not
@@ -184,7 +197,7 @@ class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
      * currently monitoring the music library for changes.
      */
     private fun updateIdleSession() {
-        if (settings.shouldBeObserving) {
+        if (musicSettings.shouldBeObserving) {
             // There are a few reasons why we stay in the foreground with automatic rescanning:
             // 1. Newer versions of Android have become more and more restrictive regarding
             // how a foreground service starts. Thus, it's best to go foreground now so that
@@ -274,7 +287,7 @@ class IndexerService : Service(), Indexer.Controller, MusicSettings.Listener {
         override fun run() {
             // Check here if we should even start a reindex. This is much less bug-prone than
             // registering and de-registering this component as this setting changes.
-            if (settings.shouldBeObserving) {
+            if (musicSettings.shouldBeObserving) {
                 onStartIndexing(true)
             }
         }

app/src/main/java/org/oxycblt/auxio/picker/ArtistChoiceAdapter.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.picker
+package org.oxycblt.auxio.picker
 
 import android.view.View
 import android.view.ViewGroup

app/src/main/java/org/oxycblt/auxio/picker/ArtistNavigationPickerDialog.kt

@@ -15,12 +15,13 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.picker
+package org.oxycblt.auxio.picker
 
 import android.os.Bundle
 import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.RecyclerView
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.databinding.DialogMusicPickerBinding
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.ui.NavigationViewModel
@@ -29,6 +30,7 @@ import org.oxycblt.auxio.ui.NavigationViewModel
  * An [ArtistPickerDialog] intended for when [Artist] navigation is ambiguous.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class ArtistNavigationPickerDialog : ArtistPickerDialog() {
     private val navModel: NavigationViewModel by activityViewModels()
     // Information about what Song to show choices for is initially within the navigation arguments

app/src/main/java/org/oxycblt/auxio/picker/ArtistPickerDialog.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.picker
+package org.oxycblt.auxio.picker
 
 import android.os.Bundle
 import android.view.LayoutInflater
@@ -23,6 +23,7 @@ import androidx.appcompat.app.AlertDialog
 import androidx.fragment.app.viewModels
 import androidx.navigation.fragment.findNavController
 import androidx.recyclerview.widget.RecyclerView
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogMusicPickerBinding
 import org.oxycblt.auxio.list.ClickableListListener
@@ -36,6 +37,7 @@ import org.oxycblt.auxio.util.collectImmediately
  * to choose from.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 abstract class ArtistPickerDialog :
     ViewBindingDialogFragment<DialogMusicPickerBinding>(), ClickableListListener<Artist> {
     protected val pickerModel: PickerViewModel by viewModels()

app/src/main/java/org/oxycblt/auxio/picker/ArtistPlaybackPickerDialog.kt

@@ -15,16 +15,17 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.picker
+package org.oxycblt.auxio.picker
 
 import android.os.Bundle
+import androidx.fragment.app.activityViewModels
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.RecyclerView
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.databinding.DialogMusicPickerBinding
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.playback.PlaybackViewModel
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.requireIs
 import org.oxycblt.auxio.util.unlikelyToBeNull
 
@@ -32,8 +33,9 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * An [ArtistPickerDialog] intended for when [Artist] playback is ambiguous.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class ArtistPlaybackPickerDialog : ArtistPickerDialog() {
-    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val playbackModel: PlaybackViewModel by activityViewModels()
     // Information about what Song to show choices for is initially within the navigation arguments
     // as UIDs, as that is the only safe way to parcel a Song.
     private val args: ArtistPlaybackPickerDialogArgs by navArgs()

app/src/main/java/org/oxycblt/auxio/picker/GenreChoiceAdapter.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.picker
+package org.oxycblt.auxio.picker
 
 import android.view.View
 import android.view.ViewGroup

app/src/main/java/org/oxycblt/auxio/picker/GenrePlaybackPickerDialog.kt

@@ -15,15 +15,17 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.picker
+package org.oxycblt.auxio.picker
 
 import android.os.Bundle
 import android.view.LayoutInflater
 import androidx.appcompat.app.AlertDialog
+import androidx.fragment.app.activityViewModels
 import androidx.fragment.app.viewModels
 import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.RecyclerView
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogMusicPickerBinding
 import org.oxycblt.auxio.list.ClickableListListener
@@ -31,7 +33,6 @@ import org.oxycblt.auxio.music.Genre
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.ui.ViewBindingDialogFragment
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.collectImmediately
 import org.oxycblt.auxio.util.requireIs
 import org.oxycblt.auxio.util.unlikelyToBeNull
@@ -40,10 +41,11 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * A picker [ViewBindingDialogFragment] intended for when [Genre] playback is ambiguous.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class GenrePlaybackPickerDialog :
     ViewBindingDialogFragment<DialogMusicPickerBinding>(), ClickableListListener<Genre> {
     private val pickerModel: PickerViewModel by viewModels()
-    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val playbackModel: PlaybackViewModel by activityViewModels()
     // Information about what Song to show choices for is initially within the navigation arguments
     // as UIDs, as that is the only safe way to parcel a Song.
     private val args: GenrePlaybackPickerDialogArgs by navArgs()

app/src/main/java/org/oxycblt/auxio/picker/PickerViewModel.kt

@@ -15,14 +15,15 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.music.picker
+package org.oxycblt.auxio.picker
 
 import androidx.lifecycle.ViewModel
+import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.MusicStore
+import org.oxycblt.auxio.music.model.Library
-import org.oxycblt.auxio.music.library.Library
 import org.oxycblt.auxio.util.unlikelyToBeNull
 
 /**
@@ -30,8 +31,9 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * contain the music themselves and then exit if the library changes.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class PickerViewModel : ViewModel(), MusicStore.Listener {
+@HiltViewModel
-    private val musicStore = MusicStore.getInstance()
+class PickerViewModel @Inject constructor(private val musicRepository: MusicRepository) :
+    ViewModel(), MusicRepository.Listener {
 
     private val _currentItem = MutableStateFlow<Music?>(null)
     /** The current item whose artists should be shown in the picker. Null if there is no item. */
@@ -49,7 +51,7 @@ class PickerViewModel : ViewModel(), MusicStore.Listener {
         get() = _genreChoices
 
     override fun onCleared() {
-        musicStore.removeListener(this)
+        musicRepository.removeListener(this)
     }
 
     override fun onLibraryChanged(library: Library?) {
@@ -63,7 +65,7 @@ class PickerViewModel : ViewModel(), MusicStore.Listener {
      * @param uid The [Music.UID] of the [Song] to update to.
      */
     fun setItemUid(uid: Music.UID) {
-        val library = unlikelyToBeNull(musicStore.library)
+        val library = unlikelyToBeNull(musicRepository.library)
         _currentItem.value = library.find(uid)
         refreshChoices()
     }

app/src/main/java/org/oxycblt/auxio/playback/PlaybackBarFragment.kt

@@ -20,14 +20,15 @@ package org.oxycblt.auxio.playback
 import android.os.Bundle
 import android.view.LayoutInflater
 import androidx.fragment.app.activityViewModels
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentPlaybackBarBinding
 import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.resolveNames
 import org.oxycblt.auxio.playback.state.RepeatMode
 import org.oxycblt.auxio.ui.MainNavigationAction
 import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.ui.ViewBindingFragment
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.collectImmediately
 import org.oxycblt.auxio.util.getAttrColorCompat
 import org.oxycblt.auxio.util.getColorCompat
@@ -36,8 +37,9 @@ import org.oxycblt.auxio.util.getColorCompat
  * A [ViewBindingFragment] that shows the current playback state in a compact manner.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class PlaybackBarFragment : ViewBindingFragment<FragmentPlaybackBarBinding>() {
-    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val playbackModel: PlaybackViewModel by activityViewModels()
     private val navModel: NavigationViewModel by activityViewModels()
 
     override fun onCreateBinding(inflater: LayoutInflater) =
@@ -121,7 +123,7 @@ class PlaybackBarFragment : ViewBindingFragment<FragmentPlaybackBarBinding>() {
             val binding = requireBinding()
             binding.playbackCover.bind(song)
             binding.playbackSong.text = song.resolveName(context)
-            binding.playbackInfo.text = song.resolveArtistContents(context)
+            binding.playbackInfo.text = song.artists.resolveNames(context)
             binding.playbackProgressBar.max = song.durationMs.msToDs().toInt()
         }
     }

app/src/main/java/org/oxycblt/auxio/playback/PlaybackModule.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.playback
+
+import dagger.Binds
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+import org.oxycblt.auxio.playback.state.PlaybackStateManager
+import org.oxycblt.auxio.playback.state.PlaybackStateManagerImpl
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface PlaybackModule {
+    @Singleton
+    @Binds
+    fun stateManager(playbackManager: PlaybackStateManagerImpl): PlaybackStateManager
+    @Binds fun settings(playbackSettings: PlaybackSettingsImpl): PlaybackSettings
+}

app/src/main/java/org/oxycblt/auxio/playback/PlaybackPanelFragment.kt

@@ -28,17 +28,18 @@ import androidx.activity.result.contract.ActivityResultContracts
 import androidx.appcompat.widget.Toolbar
 import androidx.core.view.updatePadding
 import androidx.fragment.app.activityViewModels
+import dagger.hilt.android.AndroidEntryPoint
 import org.oxycblt.auxio.MainFragmentDirections
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.FragmentPlaybackPanelBinding
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.resolveNames
 import org.oxycblt.auxio.playback.state.RepeatMode
 import org.oxycblt.auxio.playback.ui.StyledSeekBar
 import org.oxycblt.auxio.ui.MainNavigationAction
 import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.ui.ViewBindingFragment
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.collectImmediately
 import org.oxycblt.auxio.util.showToast
 import org.oxycblt.auxio.util.systemBarInsetsCompat
@@ -48,11 +49,12 @@ import org.oxycblt.auxio.util.systemBarInsetsCompat
  * available controls.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class PlaybackPanelFragment :
     ViewBindingFragment<FragmentPlaybackPanelBinding>(),
     Toolbar.OnMenuItemClickListener,
     StyledSeekBar.Listener {
-    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val playbackModel: PlaybackViewModel by activityViewModels()
     private val navModel: NavigationViewModel by activityViewModels()
     private var equalizerLauncher: ActivityResultLauncher<Intent>? = null
 
@@ -183,7 +185,7 @@ class PlaybackPanelFragment :
         val context = requireContext()
         binding.playbackCover.bind(song)
         binding.playbackSong.text = song.resolveName(context)
-        binding.playbackArtist.text = song.resolveArtistContents(context)
+        binding.playbackArtist.text = song.artists.resolveNames(context)
         binding.playbackAlbum.text = song.album.resolveName(context)
         binding.playbackSeekBar.durationDs = song.durationMs.msToDs()
     }

app/src/main/java/org/oxycblt/auxio/playback/PlaybackSettings.kt

@@ -19,6 +19,8 @@ package org.oxycblt.auxio.playback
 
 import android.content.Context
 import androidx.core.content.edit
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
 import org.oxycblt.auxio.IntegerTable
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.music.MusicMode
@@ -65,154 +67,143 @@ interface PlaybackSettings : Settings<PlaybackSettings.Listener> {
         /** Called when [notificationAction] has changed. */
         fun onNotificationActionChanged() {}
     }
+}
 
-    private class Real(context: Context) : Settings.Real<Listener>(context), PlaybackSettings {
+class PlaybackSettingsImpl @Inject constructor(@ApplicationContext context: Context) :
-        override val inListPlaybackMode: MusicMode
+    Settings.Impl<PlaybackSettings.Listener>(context), PlaybackSettings {
-            get() =
+    override val inListPlaybackMode: MusicMode
-                MusicMode.fromIntCode(
+        get() =
-                    sharedPreferences.getInt(
+            MusicMode.fromIntCode(
-                        getString(R.string.set_key_in_list_playback_mode), Int.MIN_VALUE))
+                sharedPreferences.getInt(
+                    getString(R.string.set_key_in_list_playback_mode), Int.MIN_VALUE))
+                ?: MusicMode.SONGS
+
+    override val inParentPlaybackMode: MusicMode?
+        get() =
+            MusicMode.fromIntCode(
+                sharedPreferences.getInt(
+                    getString(R.string.set_key_in_parent_playback_mode), Int.MIN_VALUE))
+
+    override val barAction: ActionMode
+        get() =
+            ActionMode.fromIntCode(
+                sharedPreferences.getInt(getString(R.string.set_key_bar_action), Int.MIN_VALUE))
+                ?: ActionMode.NEXT
+
+    override val notificationAction: ActionMode
+        get() =
+            ActionMode.fromIntCode(
+                sharedPreferences.getInt(getString(R.string.set_key_notif_action), Int.MIN_VALUE))
+                ?: ActionMode.REPEAT
+
+    override val headsetAutoplay: Boolean
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_headset_autoplay), false)
+
+    override val replayGainMode: ReplayGainMode
+        get() =
+            ReplayGainMode.fromIntCode(
+                sharedPreferences.getInt(getString(R.string.set_key_replay_gain), Int.MIN_VALUE))
+                ?: ReplayGainMode.DYNAMIC
+
+    override var replayGainPreAmp: ReplayGainPreAmp
+        get() =
+            ReplayGainPreAmp(
+                sharedPreferences.getFloat(getString(R.string.set_key_pre_amp_with), 0f),
+                sharedPreferences.getFloat(getString(R.string.set_key_pre_amp_without), 0f))
+        set(value) {
+            sharedPreferences.edit {
+                putFloat(getString(R.string.set_key_pre_amp_with), value.with)
+                putFloat(getString(R.string.set_key_pre_amp_without), value.without)
+                apply()
+            }
+        }
+
+    override val keepShuffle: Boolean
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_keep_shuffle), true)
+
+    override val rewindWithPrev: Boolean
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_rewind_prev), true)
+
+    override val pauseOnRepeat: Boolean
+        get() = sharedPreferences.getBoolean(getString(R.string.set_key_repeat_pause), false)
+
+    override fun migrate() {
+        // "Use alternate notification action" was converted to an ActionMode setting in 3.0.0.
+        if (sharedPreferences.contains(OLD_KEY_ALT_NOTIF_ACTION)) {
+            logD("Migrating $OLD_KEY_ALT_NOTIF_ACTION")
+
+            val mode =
+                if (sharedPreferences.getBoolean(OLD_KEY_ALT_NOTIF_ACTION, false)) {
+                    ActionMode.SHUFFLE
+                } else {
+                    ActionMode.REPEAT
+                }
+
+            sharedPreferences.edit {
+                putInt(getString(R.string.set_key_notif_action), mode.intCode)
+                remove(OLD_KEY_ALT_NOTIF_ACTION)
+                apply()
+            }
+        }
+
+        // PlaybackMode was converted to MusicMode in 3.0.0
+
+        fun Int.migratePlaybackMode() =
+            when (this) {
+                // Convert PlaybackMode into MusicMode
+                IntegerTable.PLAYBACK_MODE_ALL_SONGS -> MusicMode.SONGS
+                IntegerTable.PLAYBACK_MODE_IN_ARTIST -> MusicMode.ARTISTS
+                IntegerTable.PLAYBACK_MODE_IN_ALBUM -> MusicMode.ALBUMS
+                IntegerTable.PLAYBACK_MODE_IN_GENRE -> MusicMode.GENRES
+                else -> null
+            }
+
+        if (sharedPreferences.contains(OLD_KEY_LIB_PLAYBACK_MODE)) {
+            logD("Migrating $OLD_KEY_LIB_PLAYBACK_MODE")
+
+            val mode =
+                sharedPreferences
+                    .getInt(OLD_KEY_LIB_PLAYBACK_MODE, IntegerTable.PLAYBACK_MODE_ALL_SONGS)
+                    .migratePlaybackMode()
                     ?: MusicMode.SONGS
 
-        override val inParentPlaybackMode: MusicMode?
+            sharedPreferences.edit {
-            get() =
+                putInt(getString(R.string.set_key_in_list_playback_mode), mode.intCode)
-                MusicMode.fromIntCode(
+                remove(OLD_KEY_LIB_PLAYBACK_MODE)
-                    sharedPreferences.getInt(
+                apply()
-                        getString(R.string.set_key_in_parent_playback_mode), Int.MIN_VALUE))
-
-        override val barAction: ActionMode
-            get() =
-                ActionMode.fromIntCode(
-                    sharedPreferences.getInt(getString(R.string.set_key_bar_action), Int.MIN_VALUE))
-                    ?: ActionMode.NEXT
-
-        override val notificationAction: ActionMode
-            get() =
-                ActionMode.fromIntCode(
-                    sharedPreferences.getInt(
-                        getString(R.string.set_key_notif_action), Int.MIN_VALUE))
-                    ?: ActionMode.REPEAT
-
-        override val headsetAutoplay: Boolean
-            get() =
-                sharedPreferences.getBoolean(getString(R.string.set_key_headset_autoplay), false)
-
-        override val replayGainMode: ReplayGainMode
-            get() =
-                ReplayGainMode.fromIntCode(
-                    sharedPreferences.getInt(
-                        getString(R.string.set_key_replay_gain), Int.MIN_VALUE))
-                    ?: ReplayGainMode.DYNAMIC
-
-        override var replayGainPreAmp: ReplayGainPreAmp
-            get() =
-                ReplayGainPreAmp(
-                    sharedPreferences.getFloat(getString(R.string.set_key_pre_amp_with), 0f),
-                    sharedPreferences.getFloat(getString(R.string.set_key_pre_amp_without), 0f))
-            set(value) {
-                sharedPreferences.edit {
-                    putFloat(getString(R.string.set_key_pre_amp_with), value.with)
-                    putFloat(getString(R.string.set_key_pre_amp_without), value.without)
-                    apply()
-                }
-            }
-
-        override val keepShuffle: Boolean
-            get() = sharedPreferences.getBoolean(getString(R.string.set_key_keep_shuffle), true)
-
-        override val rewindWithPrev: Boolean
-            get() = sharedPreferences.getBoolean(getString(R.string.set_key_rewind_prev), true)
-
-        override val pauseOnRepeat: Boolean
-            get() = sharedPreferences.getBoolean(getString(R.string.set_key_repeat_pause), false)
-
-        override fun migrate() {
-            // "Use alternate notification action" was converted to an ActionMode setting in 3.0.0.
-            if (sharedPreferences.contains(OLD_KEY_ALT_NOTIF_ACTION)) {
-                logD("Migrating $OLD_KEY_ALT_NOTIF_ACTION")
-
-                val mode =
-                    if (sharedPreferences.getBoolean(OLD_KEY_ALT_NOTIF_ACTION, false)) {
-                        ActionMode.SHUFFLE
-                    } else {
-                        ActionMode.REPEAT
-                    }
-
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_notif_action), mode.intCode)
-                    remove(OLD_KEY_ALT_NOTIF_ACTION)
-                    apply()
-                }
-            }
-
-            // PlaybackMode was converted to MusicMode in 3.0.0
-
-            fun Int.migratePlaybackMode() =
-                when (this) {
-                    // Convert PlaybackMode into MusicMode
-                    IntegerTable.PLAYBACK_MODE_ALL_SONGS -> MusicMode.SONGS
-                    IntegerTable.PLAYBACK_MODE_IN_ARTIST -> MusicMode.ARTISTS
-                    IntegerTable.PLAYBACK_MODE_IN_ALBUM -> MusicMode.ALBUMS
-                    IntegerTable.PLAYBACK_MODE_IN_GENRE -> MusicMode.GENRES
-                    else -> null
-                }
-
-            if (sharedPreferences.contains(OLD_KEY_LIB_PLAYBACK_MODE)) {
-                logD("Migrating $OLD_KEY_LIB_PLAYBACK_MODE")
-
-                val mode =
-                    sharedPreferences
-                        .getInt(OLD_KEY_LIB_PLAYBACK_MODE, IntegerTable.PLAYBACK_MODE_ALL_SONGS)
-                        .migratePlaybackMode()
-                        ?: MusicMode.SONGS
-
-                sharedPreferences.edit {
-                    putInt(getString(R.string.set_key_in_list_playback_mode), mode.intCode)
-                    remove(OLD_KEY_LIB_PLAYBACK_MODE)
-                    apply()
-                }
-            }
-
-            if (sharedPreferences.contains(OLD_KEY_DETAIL_PLAYBACK_MODE)) {
-                logD("Migrating $OLD_KEY_DETAIL_PLAYBACK_MODE")
-
-                val mode =
-                    sharedPreferences
-                        .getInt(OLD_KEY_DETAIL_PLAYBACK_MODE, Int.MIN_VALUE)
-                        .migratePlaybackMode()
-
-                sharedPreferences.edit {
-                    putInt(
-                        getString(R.string.set_key_in_parent_playback_mode),
-                        mode?.intCode ?: Int.MIN_VALUE)
-                    remove(OLD_KEY_DETAIL_PLAYBACK_MODE)
-                    apply()
-                }
             }
         }
 
-        override fun onSettingChanged(key: String, listener: Listener) {
+        if (sharedPreferences.contains(OLD_KEY_DETAIL_PLAYBACK_MODE)) {
-            when (key) {
+            logD("Migrating $OLD_KEY_DETAIL_PLAYBACK_MODE")
-                getString(R.string.set_key_replay_gain),
-                getString(R.string.set_key_pre_amp_with),
-                getString(R.string.set_key_pre_amp_without) ->
-                    listener.onReplayGainSettingsChanged()
-                getString(R.string.set_key_notif_action) -> listener.onNotificationActionChanged()
-            }
-        }
 
-        private companion object {
+            val mode =
-            const val OLD_KEY_ALT_NOTIF_ACTION = "KEY_ALT_NOTIF_ACTION"
+                sharedPreferences
-            const val OLD_KEY_LIB_PLAYBACK_MODE = "KEY_SONG_PLAY_MODE2"
+                    .getInt(OLD_KEY_DETAIL_PLAYBACK_MODE, Int.MIN_VALUE)
-            const val OLD_KEY_DETAIL_PLAYBACK_MODE = "auxio_detail_song_play_mode"
+                    .migratePlaybackMode()
+
+            sharedPreferences.edit {
+                putInt(
+                    getString(R.string.set_key_in_parent_playback_mode),
+                    mode?.intCode ?: Int.MIN_VALUE)
+                remove(OLD_KEY_DETAIL_PLAYBACK_MODE)
+                apply()
+            }
         }
     }
 
-    companion object {
+    override fun onSettingChanged(key: String, listener: PlaybackSettings.Listener) {
-        /**
+        when (key) {
-         * Get a framework-backed implementation.
+            getString(R.string.set_key_replay_gain),
-         * @param context [Context] required.
+            getString(R.string.set_key_pre_amp_with),
-         */
+            getString(R.string.set_key_pre_amp_without) -> listener.onReplayGainSettingsChanged()
-        fun from(context: Context): PlaybackSettings = Real(context)
+            getString(R.string.set_key_notif_action) -> listener.onNotificationActionChanged()
+        }
+    }
+
+    private companion object {
+        const val OLD_KEY_ALT_NOTIF_ACTION = "KEY_ALT_NOTIF_ACTION"
+        const val OLD_KEY_LIB_PLAYBACK_MODE = "KEY_SONG_PLAY_MODE2"
+        const val OLD_KEY_DETAIL_PLAYBACK_MODE = "auxio_detail_song_play_mode"
     }
 }

app/src/main/java/org/oxycblt/auxio/playback/PlaybackViewModel.kt

@@ -17,28 +17,34 @@
  
 package org.oxycblt.auxio.playback
 
-import android.app.Application
+import androidx.lifecycle.ViewModel
-import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.viewModelScope
+import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.launch
 import org.oxycblt.auxio.music.*
+import org.oxycblt.auxio.playback.persist.PersistenceRepository
+import org.oxycblt.auxio.playback.queue.Queue
 import org.oxycblt.auxio.playback.state.*
-import org.oxycblt.auxio.util.context
 
 /**
- * An [AndroidViewModel] that provides a safe UI frontend for the current playback state.
+ * An [ViewModel] that provides a safe UI frontend for the current playback state.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class PlaybackViewModel(application: Application) :
+@HiltViewModel
-    AndroidViewModel(application), PlaybackStateManager.Listener {
+class PlaybackViewModel
-    private val musicSettings = MusicSettings.from(application)
+@Inject
-    private val playbackSettings = PlaybackSettings.from(application)
+constructor(
-    private val playbackManager = PlaybackStateManager.getInstance()
+    private val playbackManager: PlaybackStateManager,
-    private val musicStore = MusicStore.getInstance()
+    private val playbackSettings: PlaybackSettings,
+    private val persistenceRepository: PersistenceRepository,
+    private val musicRepository: MusicRepository,
+    private val musicSettings: MusicSettings
+) : ViewModel(), PlaybackStateManager.Listener {
     private var lastPositionJob: Job? = null
 
     private val _song = MutableStateFlow<Song?>(null)
@@ -277,7 +283,7 @@ class PlaybackViewModel(application: Application) :
         check(song == null || parent == null || parent.songs.contains(song)) {
             "Song to play not in parent"
         }
-        val library = musicStore.library ?: return
+        val library = musicRepository.library ?: return
         val sort =
             when (parent) {
                 is Genre -> musicSettings.genreSongSort
@@ -428,8 +434,7 @@ class PlaybackViewModel(application: Application) :
      */
     fun savePlaybackState(onDone: (Boolean) -> Unit) {
         viewModelScope.launch {
-            val saved = playbackManager.saveState(PlaybackStateDatabase.getInstance(context))
+            onDone(persistenceRepository.saveState(playbackManager.toSavedState()))
-            onDone(saved)
         }
     }
 
@@ -438,10 +443,7 @@ class PlaybackViewModel(application: Application) :
      * @param onDone Called when the wipe is completed with true if successful, and false otherwise.
      */
     fun wipePlaybackState(onDone: (Boolean) -> Unit) {
-        viewModelScope.launch {
+        viewModelScope.launch { onDone(persistenceRepository.saveState(null)) }
-            val wiped = playbackManager.wipeState(PlaybackStateDatabase.getInstance(context))
-            onDone(wiped)
-        }
     }
 
     /**
@@ -451,9 +453,16 @@ class PlaybackViewModel(application: Application) :
      */
     fun tryRestorePlaybackState(onDone: (Boolean) -> Unit) {
         viewModelScope.launch {
-            val restored =
+            val library = musicRepository.library
-                playbackManager.restoreState(PlaybackStateDatabase.getInstance(context), true)
+            if (library != null) {
-            onDone(restored)
+                val savedState = persistenceRepository.readState(library)
+                if (savedState != null) {
+                    playbackManager.applySavedState(savedState, true)
+                    onDone(true)
+                    return@launch
+                }
+            }
+            onDone(false)
         }
     }
 

app/src/main/java/org/oxycblt/auxio/playback/persist/PersistenceDatabase.kt

@@ -0,0 +1,156 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.playback.persist
+
+import androidx.room.Dao
+import androidx.room.Database
+import androidx.room.Entity
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.PrimaryKey
+import androidx.room.Query
+import androidx.room.RoomDatabase
+import androidx.room.TypeConverter
+import androidx.room.TypeConverters
+import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.playback.state.RepeatMode
+
+/**
+ * Provides raw access to the database storing the persisted playback state.
+ * @author Alexander Capehart
+ */
+@Database(
+    entities = [PlaybackState::class, QueueHeapItem::class, QueueMappingItem::class],
+    version = 27,
+    exportSchema = false)
+@TypeConverters(PersistenceDatabase.Converters::class)
+abstract class PersistenceDatabase : RoomDatabase() {
+    /**
+     * Get the current [PlaybackStateDao].
+     * @return A [PlaybackStateDao] providing control of the database's playback state tables.
+     */
+    abstract fun playbackStateDao(): PlaybackStateDao
+
+    /**
+     * Get the current [QueueDao].
+     * @return A [QueueDao] providing control of the database's queue tables.
+     */
+    abstract fun queueDao(): QueueDao
+
+    object Converters {
+        /** @see [Music.UID.toString] */
+        @TypeConverter fun fromMusicUID(uid: Music.UID?) = uid?.toString()
+
+        /** @see [Music.UID.fromString] */
+        @TypeConverter fun toMusicUid(string: String?) = string?.let(Music.UID::fromString)
+    }
+}
+
+/**
+ * Provides control of the persisted playback state table.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+@Dao
+interface PlaybackStateDao {
+    /**
+     * Get the previously persisted [PlaybackState].
+     * @return The previously persisted [PlaybackState], or null if one was not present.
+     */
+    @Query("SELECT * FROM ${PlaybackState.TABLE_NAME} WHERE id = 0")
+    suspend fun getState(): PlaybackState?
+
+    /** Delete any previously persisted [PlaybackState]s. */
+    @Query("DELETE FROM ${PlaybackState.TABLE_NAME}") suspend fun nukeState()
+
+    /**
+     * Insert a new [PlaybackState] into the database.
+     * @param state The [PlaybackState] to insert.
+     */
+    @Insert(onConflict = OnConflictStrategy.ABORT) suspend fun insertState(state: PlaybackState)
+}
+
+/**
+ * Provides control of the persisted queue state tables.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+@Dao
+interface QueueDao {
+    /**
+     * Get the previously persisted queue heap.
+     * @return A list of persisted [QueueHeapItem]s wrapping each heap item.
+     */
+    @Query("SELECT * FROM ${QueueHeapItem.TABLE_NAME}") suspend fun getHeap(): List<QueueHeapItem>
+
+    /**
+     * Get the previously persisted queue mapping.
+     * @return A list of persisted [QueueMappingItem]s wrapping each heap item.
+     */
+    @Query("SELECT * FROM ${QueueMappingItem.TABLE_NAME}")
+    suspend fun getMapping(): List<QueueMappingItem>
+
+    /** Delete any previously persisted queue heap entries. */
+    @Query("DELETE FROM ${QueueHeapItem.TABLE_NAME}") suspend fun nukeHeap()
+
+    /** Delete any previously persisted queue mapping entries. */
+    @Query("DELETE FROM ${QueueMappingItem.TABLE_NAME}") suspend fun nukeMapping()
+
+    /**
+     * Insert new heap entries into the database.
+     * @param heap The list of wrapped [QueueHeapItem]s to insert.
+     */
+    @Insert(onConflict = OnConflictStrategy.ABORT) suspend fun insertHeap(heap: List<QueueHeapItem>)
+
+    /**
+     * Insert new mapping entries into the database.
+     * @param mapping The list of wrapped [QueueMappingItem] to insert.
+     */
+    @Insert(onConflict = OnConflictStrategy.ABORT)
+    suspend fun insertMapping(mapping: List<QueueMappingItem>)
+}
+
+@Entity(tableName = PlaybackState.TABLE_NAME)
+data class PlaybackState(
+    @PrimaryKey val id: Int,
+    val index: Int,
+    val positionMs: Long,
+    val repeatMode: RepeatMode,
+    val songUid: Music.UID,
+    val parentUid: Music.UID?
+) {
+    companion object {
+        const val TABLE_NAME = "playback_state"
+    }
+}
+
+@Entity(tableName = QueueHeapItem.TABLE_NAME)
+data class QueueHeapItem(@PrimaryKey val id: Int, val uid: Music.UID) {
+    companion object {
+        const val TABLE_NAME = "queue_heap"
+    }
+}
+
+@Entity(tableName = QueueMappingItem.TABLE_NAME)
+data class QueueMappingItem(
+    @PrimaryKey val id: Int,
+    val orderedIndex: Int,
+    val shuffledIndex: Int
+) {
+    companion object {
+        const val TABLE_NAME = "queue_mapping"
+    }
+}

app/src/main/java/org/oxycblt/auxio/playback/persist/PersistenceModule.kt

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.playback.persist
+
+import android.content.Context
+import androidx.room.Room
+import dagger.Binds
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface PersistenceModule {
+    @Binds fun repository(persistenceRepository: PersistenceRepositoryImpl): PersistenceRepository
+}
+
+@Module
+@InstallIn(SingletonComponent::class)
+class PersistenceRoomModule {
+    @Singleton
+    @Provides
+    fun database(@ApplicationContext context: Context) =
+        Room.databaseBuilder(
+                context.applicationContext,
+                PersistenceDatabase::class.java,
+                "playback_persistence.db")
+            .fallbackToDestructiveMigration()
+            .fallbackToDestructiveMigrationFrom(1)
+            .fallbackToDestructiveMigrationOnDowngrade()
+            .build()
+
+    @Provides fun playbackStateDao(database: PersistenceDatabase) = database.playbackStateDao()
+
+    @Provides fun queueDao(database: PersistenceDatabase) = database.queueDao()
+}

app/src/main/java/org/oxycblt/auxio/playback/persist/PersistenceRepository.kt

@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2023 Auxio Project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+ 
+package org.oxycblt.auxio.playback.persist
+
+import javax.inject.Inject
+import org.oxycblt.auxio.music.MusicParent
+import org.oxycblt.auxio.music.model.Library
+import org.oxycblt.auxio.playback.queue.Queue
+import org.oxycblt.auxio.playback.state.PlaybackStateManager
+import org.oxycblt.auxio.util.logD
+import org.oxycblt.auxio.util.logE
+
+/**
+ * Manages the persisted playback state in a structured manner.
+ * @author Alexander Capehart (OxygenCobalt)
+ */
+interface PersistenceRepository {
+    /**
+     * Read the previously persisted [PlaybackStateManager.SavedState].
+     * @param library The [Library] required to de-serialize the [PlaybackStateManager.SavedState].
+     */
+    suspend fun readState(library: Library): PlaybackStateManager.SavedState?
+
+    /**
+     * Persist a new [PlaybackStateManager.SavedState].
+     * @param state The [PlaybackStateManager.SavedState] to persist.
+     */
+    suspend fun saveState(state: PlaybackStateManager.SavedState?): Boolean
+}
+
+class PersistenceRepositoryImpl
+@Inject
+constructor(private val playbackStateDao: PlaybackStateDao, private val queueDao: QueueDao) :
+    PersistenceRepository {
+
+    override suspend fun readState(library: Library): PlaybackStateManager.SavedState? {
+        val playbackState: PlaybackState
+        val heap: List<QueueHeapItem>
+        val mapping: List<QueueMappingItem>
+        try {
+            playbackState = playbackStateDao.getState() ?: return null
+            heap = queueDao.getHeap()
+            mapping = queueDao.getMapping()
+        } catch (e: Exception) {
+            logE("Unable to load playback state data")
+            logE(e.stackTraceToString())
+            return null
+        }
+
+        val orderedMapping = mutableListOf<Int>()
+        val shuffledMapping = mutableListOf<Int>()
+        for (entry in mapping) {
+            orderedMapping.add(entry.orderedIndex)
+            shuffledMapping.add(entry.shuffledIndex)
+        }
+
+        val parent = playbackState.parentUid?.let { library.find<MusicParent>(it) }
+        logD("Read playback state")
+
+        return PlaybackStateManager.SavedState(
+            parent = parent,
+            queueState =
+                Queue.SavedState(
+                    heap.map { library.find(it.uid) },
+                    orderedMapping,
+                    shuffledMapping,
+                    playbackState.index,
+                    playbackState.songUid),
+            positionMs = playbackState.positionMs,
+            repeatMode = playbackState.repeatMode)
+    }
+
+    override suspend fun saveState(state: PlaybackStateManager.SavedState?): Boolean {
+        // Only bother saving a state if a song is actively playing from one.
+        // This is not the case with a null state.
+        try {
+            playbackStateDao.nukeState()
+            queueDao.nukeHeap()
+            queueDao.nukeMapping()
+        } catch (e: Exception) {
+            logE("Unable to clear previous state")
+            logE(e.stackTraceToString())
+            return false
+        }
+        logD("Cleared state")
+        if (state != null) {
+            // Transform saved state into raw state, which can then be written to the database.
+            val playbackState =
+                PlaybackState(
+                    id = 0,
+                    index = state.queueState.index,
+                    positionMs = state.positionMs,
+                    repeatMode = state.repeatMode,
+                    songUid = state.queueState.songUid,
+                    parentUid = state.parent?.uid)
+
+            // Convert the remaining queue information do their database-specific counterparts.
+            val heap =
+                state.queueState.heap.mapIndexed { i, song ->
+                    QueueHeapItem(i, requireNotNull(song).uid)
+                }
+            val mapping =
+                state.queueState.orderedMapping.zip(state.queueState.shuffledMapping).mapIndexed {
+                    i,
+                    pair ->
+                    QueueMappingItem(i, pair.first, pair.second)
+                }
+            try {
+                playbackStateDao.insertState(playbackState)
+                queueDao.insertHeap(heap)
+                queueDao.insertMapping(mapping)
+            } catch (e: Exception) {
+                logE("Unable to write new state")
+                logE(e.stackTraceToString())
+                return false
+            }
+            logD("Wrote state")
+        }
+        return true
+    }
+}

app/src/main/java/org/oxycblt/auxio/playback/queue/Queue.kt

@@ -15,7 +15,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
  
-package org.oxycblt.auxio.playback.state
+package org.oxycblt.auxio.playback.queue
 
 import kotlin.random.Random
 import kotlin.random.nextInt
@@ -36,30 +36,82 @@ import org.oxycblt.auxio.music.Song
  *
  * @author OxygenCobalt
  */
-class Queue {
+interface Queue {
+    /** The index of the currently playing [Song] in the current mapping. */
+    val index: Int
+    /** The currently playing [Song]. */
+    val currentSong: Song?
+    /** Whether this queue is shuffled. */
+    val isShuffled: Boolean
+    /**
+     * Resolve this queue into a more conventional list of [Song]s.
+     * @return A list of [Song] corresponding to the current queue mapping.
+     */
+    fun resolve(): List<Song>
+
+    /**
+     * Represents the possible changes that can occur during certain queue mutation events. The
+     * precise meanings of these differ somewhat depending on the type of mutation done.
+     */
+    enum class ChangeResult {
+        /** Only the mapping has changed. */
+        MAPPING,
+        /** The mapping has changed, and the index also changed to align with it. */
+        INDEX,
+        /**
+         * The current song has changed, possibly alongside the mapping and index depending on the
+         * context.
+         */
+        SONG
+    }
+
+    /**
+     * An immutable representation of the queue state.
+     * @param heap The heap of [Song]s that are/were used in the queue. This can be modified with
+     * null values to represent [Song]s that were "lost" from the heap without having to change
+     * other values.
+     * @param orderedMapping The mapping of the [heap] to an ordered queue.
+     * @param shuffledMapping The mapping of the [heap] to a shuffled queue.
+     * @param index The index of the currently playing [Song] at the time of serialization.
+     * @param songUid The [Music.UID] of the [Song] that was originally at [index].
+     */
+    class SavedState(
+        val heap: List<Song?>,
+        val orderedMapping: List<Int>,
+        val shuffledMapping: List<Int>,
+        val index: Int,
+        val songUid: Music.UID,
+    ) {
+        /**
+         * Remaps the [heap] of this instance based on the given mapping function and copies it into
+         * a new [SavedState].
+         * @param transform Code to remap the existing [Song] heap into a new [Song] heap. This
+         * **MUST** be the same size as the original heap. [Song] instances that could not be
+         * converted should be replaced with null in the new heap.
+         * @throws IllegalStateException If the invariant specified by [transform] is violated.
+         */
+        inline fun remap(transform: (Song?) -> Song?) =
+            SavedState(heap.map(transform), orderedMapping, shuffledMapping, index, songUid)
+    }
+}
+
+class EditableQueue : Queue {
     @Volatile private var heap = mutableListOf<Song>()
     @Volatile private var orderedMapping = mutableListOf<Int>()
     @Volatile private var shuffledMapping = mutableListOf<Int>()
-    /** The index of the currently playing [Song] in the current mapping. */
     @Volatile
-    var index = -1
+    override var index = -1
         private set
-    /** The currently playing [Song]. */
+    override val currentSong: Song?
-    val currentSong: Song?
         get() =
             shuffledMapping
                 .ifEmpty { orderedMapping.ifEmpty { null } }
                 ?.getOrNull(index)
                 ?.let(heap::get)
-    /** Whether this queue is shuffled. */
+    override val isShuffled: Boolean
-    val isShuffled: Boolean
         get() = shuffledMapping.isNotEmpty()
 
-    /**
+    override fun resolve() =
-     * Resolve this queue into a more conventional list of [Song]s.
-     * @return A list of [Song] corresponding to the current queue mapping.
-     */
-    fun resolve() =
         if (currentSong != null) {
             shuffledMapping.map { heap[it] }.ifEmpty { orderedMapping.map { heap[it] } }
         } else {
@@ -134,14 +186,15 @@ class Queue {
     /**
      * Add [Song]s to the top of the queue. Will start playback if nothing is playing.
      * @param songs The [Song]s to add.
-     * @return [ChangeResult.MAPPING] if added to an existing queue, or [ChangeResult.SONG] if there
+     * @return [Queue.ChangeResult.MAPPING] if added to an existing queue, or
-     * was no prior playback and these enqueued [Song]s start new playback.
+     * [Queue.ChangeResult.SONG] if there was no prior playback and these enqueued [Song]s start new
+     * playback.
      */
-    fun playNext(songs: List<Song>): ChangeResult {
+    fun playNext(songs: List<Song>): Queue.ChangeResult {
         if (orderedMapping.isEmpty()) {
             // No playback, start playing these songs.
             start(songs[0], songs, false)
-            return ChangeResult.SONG
+            return Queue.ChangeResult.SONG
         }
 
         val heapIndices = songs.map(::addSongToHeap)
@@ -156,20 +209,21 @@ class Queue {
             orderedMapping.addAll(index + 1, heapIndices)
         }
         check()
-        return ChangeResult.MAPPING
+        return Queue.ChangeResult.MAPPING
     }
 
     /**
      * Add [Song]s to the end of the queue. Will start playback if nothing is playing.
      * @param songs The [Song]s to add.
-     * @return [ChangeResult.MAPPING] if added to an existing queue, or [ChangeResult.SONG] if there
+     * @return [Queue.ChangeResult.MAPPING] if added to an existing queue, or
-     * was no prior playback and these enqueued [Song]s start new playback.
+     * [Queue.ChangeResult.SONG] if there was no prior playback and these enqueued [Song]s start new
+     * playback.
      */
-    fun addToQueue(songs: List<Song>): ChangeResult {
+    fun addToQueue(songs: List<Song>): Queue.ChangeResult {
         if (orderedMapping.isEmpty()) {
             // No playback, start playing these songs.
             start(songs[0], songs, false)
-            return ChangeResult.SONG
+            return Queue.ChangeResult.SONG
         }
 
         val heapIndices = songs.map(::addSongToHeap)
@@ -179,18 +233,18 @@ class Queue {
             shuffledMapping.addAll(heapIndices)
         }
         check()
-        return ChangeResult.MAPPING
+        return Queue.ChangeResult.MAPPING
     }
 
     /**
      * Move a [Song] at the given position to a new position.
      * @param src The position of the [Song] to move.
      * @param dst The destination position of the [Song].
-     * @return [ChangeResult.MAPPING] if the move occurred after the current index,
+     * @return [Queue.ChangeResult.MAPPING] if the move occurred after the current index,
-     * [ChangeResult.INDEX] if the move occurred before or at the current index, requiring it to be
+     * [Queue.ChangeResult.INDEX] if the move occurred before or at the current index, requiring it
-     * mutated.
+     * to be mutated.
      */
-    fun move(src: Int, dst: Int): ChangeResult {
+    fun move(src: Int, dst: Int): Queue.ChangeResult {
         if (shuffledMapping.isNotEmpty()) {
             // Move songs only in the shuffled mapping. There is no sane analogous form of
             // this for the ordered mapping.
@@ -210,21 +264,21 @@ class Queue {
             else -> {
                 // Nothing to do.
                 check()
-                return ChangeResult.MAPPING
+                return Queue.ChangeResult.MAPPING
             }
         }
         check()
-        return ChangeResult.INDEX
+        return Queue.ChangeResult.INDEX
     }
 
     /**
      * Remove a [Song] at the given position.
      * @param at The position of the [Song] to remove.
-     * @return [ChangeResult.MAPPING] if the removed [Song] was after the current index,
+     * @return [Queue.ChangeResult.MAPPING] if the removed [Song] was after the current index,
-     * [ChangeResult.INDEX] if the removed [Song] was before the current index, and
+     * [Queue.ChangeResult.INDEX] if the removed [Song] was before the current index, and
-     * [ChangeResult.SONG] if the currently playing [Song] was removed.
+     * [Queue.ChangeResult.SONG] if the currently playing [Song] was removed.
      */
-    fun remove(at: Int): ChangeResult {
+    fun remove(at: Int): Queue.ChangeResult {
         if (shuffledMapping.isNotEmpty()) {
             // Remove the specified index in the shuffled mapping and the analogous song in the
             // ordered mapping.
@@ -242,34 +296,34 @@ class Queue {
         val result =
             when {
                 // We just removed the currently playing song.
-                index == at -> ChangeResult.SONG
+                index == at -> Queue.ChangeResult.SONG
                 // Index was ahead of removed song, shift back to preserve consistency.
                 index > at -> {
                     index -= 1
-                    ChangeResult.INDEX
+                    Queue.ChangeResult.INDEX
                 }
                 // Nothing to do
-                else -> ChangeResult.MAPPING
+                else -> Queue.ChangeResult.MAPPING
             }
         check()
         return result
     }
 
     /**
-     * Convert the current state of this instance into a [SavedState].
+     * Convert the current state of this instance into a [Queue.SavedState].
-     * @return A new [SavedState] reflecting the exact state of the queue when called.
+     * @return A new [Queue.SavedState] reflecting the exact state of the queue when called.
      */
     fun toSavedState() =
         currentSong?.let { song ->
-            SavedState(
+            Queue.SavedState(
                 heap.toList(), orderedMapping.toList(), shuffledMapping.toList(), index, song.uid)
         }
 
     /**
-     * Update this instance from the given [SavedState].
+     * Update this instance from the given [Queue.SavedState].
-     * @param savedState A [SavedState] with a valid queue representation.
+     * @param savedState A [Queue.SavedState] with a valid queue representation.
      */
-    fun applySavedState(savedState: SavedState) {
+    fun applySavedState(savedState: Queue.SavedState) {
         val adjustments = mutableListOf<Int?>()
         var currentShift = 0
         for (song in savedState.heap) {
@@ -345,49 +399,4 @@ class Queue {
             "Queue inconsistency detected: Shuffled mapping indices out of heap bounds"
         }
     }
-
-    /**
-     * An immutable representation of the queue state.
-     * @param heap The heap of [Song]s that are/were used in the queue. This can be modified with
-     * null values to represent [Song]s that were "lost" from the heap without having to change
-     * other values.
-     * @param orderedMapping The mapping of the [heap] to an ordered queue.
-     * @param shuffledMapping The mapping of the [heap] to a shuffled queue.
-     * @param index The index of the currently playing [Song] at the time of serialization.
-     * @param songUid The [Music.UID] of the [Song] that was originally at [index].
-     */
-    class SavedState(
-        val heap: List<Song?>,
-        val orderedMapping: List<Int>,
-        val shuffledMapping: List<Int>,
-        val index: Int,
-        val songUid: Music.UID,
-    ) {
-        /**
-         * Remaps the [heap] of this instance based on the given mapping function and copies it into
-         * a new [SavedState].
-         * @param transform Code to remap the existing [Song] heap into a new [Song] heap. This
-         * **MUST** be the same size as the original heap. [Song] instances that could not be
-         * converted should be replaced with null in the new heap.
-         * @throws IllegalStateException If the invariant specified by [transform] is violated.
-         */
-        inline fun remap(transform: (Song?) -> Song?) =
-            SavedState(heap.map(transform), orderedMapping, shuffledMapping, index, songUid)
-    }
-
-    /**
-     * Represents the possible changes that can occur during certain queue mutation events. The
-     * precise meanings of these differ somewhat depending on the type of mutation done.
-     */
-    enum class ChangeResult {
-        /** Only the mapping has changed. */
-        MAPPING,
-        /** The mapping has changed, and the index also changed to align with it. */
-        INDEX,
-        /**
-         * The current song has changed, possibly alongside the mapping and index depending on the
-         * context.
-         */
-        SONG
-    }
 }

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueAdapter.kt

@@ -33,6 +33,7 @@ import org.oxycblt.auxio.list.adapter.ListDiffer
 import org.oxycblt.auxio.list.adapter.PlayingIndicatorAdapter
 import org.oxycblt.auxio.list.recycler.SongViewHolder
 import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.resolveNames
 import org.oxycblt.auxio.util.*
 
 /**
@@ -149,7 +150,7 @@ class QueueSongViewHolder private constructor(private val binding: ItemQueueSong
         listener.bind(song, this, bodyView, binding.songDragHandle)
         binding.songAlbumCover.bind(song)
         binding.songName.text = song.resolveName(binding.context)
-        binding.songInfo.text = song.resolveArtistContents(binding.context)
+        binding.songInfo.text = song.artists.resolveNames(binding.context)
         // Not swiping this ViewHolder if it's being re-bound, ensure that the background is
         // not visible. See QueueDragCallback for why this is done.
         binding.background.isInvisible = true

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueFragment.kt

@@ -24,6 +24,7 @@ import androidx.fragment.app.activityViewModels
 import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import dagger.hilt.android.AndroidEntryPoint
 import kotlin.math.min
 import org.oxycblt.auxio.databinding.FragmentQueueBinding
 import org.oxycblt.auxio.list.EditableListListener
@@ -31,16 +32,16 @@ import org.oxycblt.auxio.list.adapter.BasicListInstructions
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.ui.ViewBindingFragment
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.collectImmediately
 
 /**
  * A [ViewBindingFragment] that displays an editable queue.
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class QueueFragment : ViewBindingFragment<FragmentQueueBinding>(), EditableListListener<Song> {
     private val queueModel: QueueViewModel by activityViewModels()
-    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val playbackModel: PlaybackViewModel by activityViewModels()
     private val queueAdapter = QueueAdapter(this)
     private var touchHelper: ItemTouchHelper? = null
 

app/src/main/java/org/oxycblt/auxio/playback/queue/QueueViewModel.kt

@@ -18,21 +18,23 @@
 package org.oxycblt.auxio.playback.queue
 
 import androidx.lifecycle.ViewModel
+import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import org.oxycblt.auxio.list.adapter.BasicListInstructions
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
-import org.oxycblt.auxio.playback.state.Queue
 
 /**
  * A [ViewModel] that manages the current queue state and allows navigation through the queue.
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
-class QueueViewModel : ViewModel(), PlaybackStateManager.Listener {
+@HiltViewModel
-    private val playbackManager = PlaybackStateManager.getInstance()
+class QueueViewModel @Inject constructor(private val playbackManager: PlaybackStateManager) :
+    ViewModel(), PlaybackStateManager.Listener {
 
     private val _queue = MutableStateFlow(listOf<Song>())
     /** The current queue. */

app/src/main/java/org/oxycblt/auxio/playback/replaygain/PreAmpCustomizeDialog.kt

@@ -21,6 +21,8 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import android.widget.TextView
 import androidx.appcompat.app.AlertDialog
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import kotlin.math.abs
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogPreAmpBinding
@@ -31,7 +33,10 @@ import org.oxycblt.auxio.ui.ViewBindingDialogFragment
  * aa [ViewBindingDialogFragment] that allows user configuration of the current [ReplayGainPreAmp].
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class PreAmpCustomizeDialog : ViewBindingDialogFragment<DialogPreAmpBinding>() {
+    @Inject lateinit var playbackSettings: PlaybackSettings
+
     override fun onCreateBinding(inflater: LayoutInflater) = DialogPreAmpBinding.inflate(inflater)
 
     override fun onConfigDialog(builder: AlertDialog.Builder) {
@@ -39,11 +44,11 @@ class PreAmpCustomizeDialog : ViewBindingDialogFragment<DialogPreAmpBinding>() {
             .setTitle(R.string.set_pre_amp)
             .setPositiveButton(R.string.lbl_ok) { _, _ ->
                 val binding = requireBinding()
-                PlaybackSettings.from(requireContext()).replayGainPreAmp =
+                playbackSettings.replayGainPreAmp =
                     ReplayGainPreAmp(binding.withTagsSlider.value, binding.withoutTagsSlider.value)
             }
             .setNeutralButton(R.string.lbl_reset) { _, _ ->
-                PlaybackSettings.from(requireContext()).replayGainPreAmp = ReplayGainPreAmp(0f, 0f)
+                playbackSettings.replayGainPreAmp = ReplayGainPreAmp(0f, 0f)
             }
             .setNegativeButton(R.string.lbl_cancel, null)
     }
@@ -53,7 +58,7 @@ class PreAmpCustomizeDialog : ViewBindingDialogFragment<DialogPreAmpBinding>() {
             // First initialization, we need to supply the sliders with the values from
             // settings. After this, the sliders save their own state, so we do not need to
             // do any restore behavior.
-            val preAmp = PlaybackSettings.from(requireContext()).replayGainPreAmp
+            val preAmp = playbackSettings.replayGainPreAmp
             binding.withTagsSlider.value = preAmp.with
             binding.withoutTagsSlider.value = preAmp.without
         }

app/src/main/java/org/oxycblt/auxio/playback/replaygain/ReplayGainAudioProcessor.kt

@@ -17,7 +17,6 @@
  
 package org.oxycblt.auxio.playback.replaygain
 
-import android.content.Context
 import com.google.android.exoplayer2.C
 import com.google.android.exoplayer2.Format
 import com.google.android.exoplayer2.Player
@@ -26,9 +25,10 @@ import com.google.android.exoplayer2.audio.AudioProcessor
 import com.google.android.exoplayer2.audio.BaseAudioProcessor
 import com.google.android.exoplayer2.util.MimeTypes
 import java.nio.ByteBuffer
+import javax.inject.Inject
 import kotlin.math.pow
 import org.oxycblt.auxio.music.Album
-import org.oxycblt.auxio.music.extractor.TextTags
+import org.oxycblt.auxio.music.metadata.TextTags
 import org.oxycblt.auxio.playback.PlaybackSettings
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
 import org.oxycblt.auxio.util.logD
@@ -43,10 +43,12 @@ import org.oxycblt.auxio.util.logD
  *
  * @author Alexander Capehart (OxygenCobalt)
  */
-class ReplayGainAudioProcessor(context: Context) :
+class ReplayGainAudioProcessor
-    BaseAudioProcessor(), Player.Listener, PlaybackSettings.Listener {
+@Inject
-    private val playbackManager = PlaybackStateManager.getInstance()
+constructor(
-    private val playbackSettings = PlaybackSettings.from(context)
+    private val playbackManager: PlaybackStateManager,
+    private val playbackSettings: PlaybackSettings
+) : BaseAudioProcessor(), Player.Listener, PlaybackSettings.Listener {
     private var lastFormat: Format? = null
 
     private var volume = 1f

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateDatabase.kt

@@ -1,335 +0,0 @@
-/*
- * Copyright (c) 2021 Auxio Project
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
- 
-package org.oxycblt.auxio.playback.state
-
-import android.content.ContentValues
-import android.content.Context
-import android.database.sqlite.SQLiteDatabase
-import android.database.sqlite.SQLiteOpenHelper
-import android.provider.BaseColumns
-import androidx.core.database.getIntOrNull
-import androidx.core.database.sqlite.transaction
-import org.oxycblt.auxio.music.*
-import org.oxycblt.auxio.music.library.Library
-import org.oxycblt.auxio.util.*
-
-/**
- * A [SQLiteDatabase] that persists the current playback state for future app lifecycles.
- * @author Alexander Capehart (OxygenCobalt)
- */
-class PlaybackStateDatabase private constructor(context: Context) :
-    SQLiteOpenHelper(context, DB_NAME, null, DB_VERSION) {
-
-    override fun onCreate(db: SQLiteDatabase) {
-        // Here, we have to split the database into two tables. One contains the queue with
-        // an indefinite amount of items, and the other contains only one entry consisting
-        // of the non-queue parts of the state, such as the playback position.
-        db.createTable(TABLE_STATE) {
-            append("${BaseColumns._ID} INTEGER PRIMARY KEY,")
-            append("${PlaybackStateColumns.INDEX} INTEGER NOT NULL,")
-            append("${PlaybackStateColumns.POSITION} LONG NOT NULL,")
-            append("${PlaybackStateColumns.REPEAT_MODE} INTEGER NOT NULL,")
-            append("${PlaybackStateColumns.SONG_UID} STRING,")
-            append("${PlaybackStateColumns.PARENT_UID} STRING")
-        }
-
-        db.createTable(TABLE_QUEUE_HEAP) {
-            append("${BaseColumns._ID} INTEGER PRIMARY KEY,")
-            append("${QueueHeapColumns.SONG_UID} STRING NOT NULL")
-        }
-
-        db.createTable(TABLE_QUEUE_MAPPINGS) {
-            append("${BaseColumns._ID} INTEGER PRIMARY KEY,")
-            append("${QueueMappingColumns.ORDERED_INDEX} INT NOT NULL,")
-            append("${QueueMappingColumns.SHUFFLED_INDEX} INT")
-        }
-    }
-
-    override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) = nuke(db)
-    override fun onDowngrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) = nuke(db)
-
-    private fun nuke(db: SQLiteDatabase) {
-        logD("Nuking database")
-        db.apply {
-            execSQL("DROP TABLE IF EXISTS $TABLE_STATE")
-            execSQL("DROP TABLE IF EXISTS $TABLE_QUEUE_HEAP")
-            execSQL("DROP TABLE IF EXISTS $TABLE_QUEUE_MAPPINGS")
-            onCreate(this)
-        }
-    }
-
-    // --- INTERFACE FUNCTIONS ---
-
-    /**
-     * Read a persisted [SavedState] from the database.
-     * @param library [Library] required to restore [SavedState].
-     * @return A persisted [SavedState], or null if one could not be found.
-     */
-    fun read(library: Library): SavedState? {
-        requireBackgroundThread()
-        // Read the saved state and queue. If the state is non-null, that must imply an
-        // existent, albeit possibly empty, queue.
-        val rawState = readRawPlaybackState() ?: return null
-        val rawQueueState = readRawQueueState(library)
-        // Restore parent item from the music library. If this fails, then the playback mode
-        // reverts to "All Songs", which is considered okay.
-        val parent = rawState.parentUid?.let { library.find<MusicParent>(it) }
-        return SavedState(
-            parent = parent,
-            queueState =
-                Queue.SavedState(
-                    heap = rawQueueState.heap,
-                    orderedMapping = rawQueueState.orderedMapping,
-                    shuffledMapping = rawQueueState.shuffledMapping,
-                    index = rawState.index,
-                    songUid = rawState.songUid),
-            positionMs = rawState.positionMs,
-            repeatMode = rawState.repeatMode)
-    }
-
-    private fun readRawPlaybackState() =
-        readableDatabase.queryAll(TABLE_STATE) { cursor ->
-            if (!cursor.moveToFirst()) {
-                // Empty, nothing to do.
-                return@queryAll null
-            }
-
-            val indexIndex = cursor.getColumnIndexOrThrow(PlaybackStateColumns.INDEX)
-            val posIndex = cursor.getColumnIndexOrThrow(PlaybackStateColumns.POSITION)
-            val repeatModeIndex = cursor.getColumnIndexOrThrow(PlaybackStateColumns.REPEAT_MODE)
-            val songUidIndex = cursor.getColumnIndexOrThrow(PlaybackStateColumns.SONG_UID)
-            val parentUidIndex = cursor.getColumnIndexOrThrow(PlaybackStateColumns.PARENT_UID)
-            RawPlaybackState(
-                index = cursor.getInt(indexIndex),
-                positionMs = cursor.getLong(posIndex),
-                repeatMode = RepeatMode.fromIntCode(cursor.getInt(repeatModeIndex))
-                        ?: RepeatMode.NONE,
-                songUid = Music.UID.fromString(cursor.getString(songUidIndex))
-                        ?: return@queryAll null,
-                parentUid = cursor.getString(parentUidIndex)?.let(Music.UID::fromString))
-        }
-
-    private fun readRawQueueState(library: Library): RawQueueState {
-        val heap = mutableListOf<Song?>()
-        readableDatabase.queryAll(TABLE_QUEUE_HEAP) { cursor ->
-            if (cursor.count == 0) {
-                // Empty, nothing to do.
-                return@queryAll
-            }
-
-            val songIndex = cursor.getColumnIndexOrThrow(QueueHeapColumns.SONG_UID)
-            while (cursor.moveToNext()) {
-                heap.add(Music.UID.fromString(cursor.getString(songIndex))?.let(library::find))
-            }
-        }
-        logD("Successfully read queue of ${heap.size} songs")
-
-        val orderedMapping = mutableListOf<Int?>()
-        val shuffledMapping = mutableListOf<Int?>()
-        readableDatabase.queryAll(TABLE_QUEUE_MAPPINGS) { cursor ->
-            if (cursor.count == 0) {
-                // Empty, nothing to do.
-                return@queryAll
-            }
-
-            val orderedIndex = cursor.getColumnIndexOrThrow(QueueMappingColumns.ORDERED_INDEX)
-            val shuffledIndex = cursor.getColumnIndexOrThrow(QueueMappingColumns.SHUFFLED_INDEX)
-            while (cursor.moveToNext()) {
-                orderedMapping.add(cursor.getInt(orderedIndex))
-                cursor.getIntOrNull(shuffledIndex)?.let(shuffledMapping::add)
-            }
-        }
-
-        return RawQueueState(heap, orderedMapping.filterNotNull(), shuffledMapping.filterNotNull())
-    }
-
-    /**
-     * Clear the previous [SavedState] and write a new one.
-     * @param state The new [SavedState] to write, or null to clear the database entirely.
-     */
-    fun write(state: SavedState?) {
-        requireBackgroundThread()
-        // Only bother saving a state if a song is actively playing from one.
-        // This is not the case with a null state.
-        if (state != null) {
-            // Transform saved state into raw state, which can then be written to the database.
-            val rawPlaybackState =
-                RawPlaybackState(
-                    index = state.queueState.index,
-                    positionMs = state.positionMs,
-                    repeatMode = state.repeatMode,
-                    songUid = state.queueState.songUid,
-                    parentUid = state.parent?.uid)
-            writeRawPlaybackState(rawPlaybackState)
-            val rawQueueState =
-                RawQueueState(
-                    heap = state.queueState.heap,
-                    orderedMapping = state.queueState.orderedMapping,
-                    shuffledMapping = state.queueState.shuffledMapping)
-            writeRawQueueState(rawQueueState)
-            logD("Wrote state")
-        } else {
-            writeRawPlaybackState(null)
-            writeRawQueueState(null)
-            logD("Cleared state")
-        }
-    }
-
-    private fun writeRawPlaybackState(rawPlaybackState: RawPlaybackState?) {
-        writableDatabase.transaction {
-            delete(TABLE_STATE, null, null)
-
-            if (rawPlaybackState != null) {
-                val stateData =
-                    ContentValues(7).apply {
-                        put(BaseColumns._ID, 0)
-                        put(PlaybackStateColumns.SONG_UID, rawPlaybackState.songUid.toString())
-                        put(PlaybackStateColumns.POSITION, rawPlaybackState.positionMs)
-                        put(PlaybackStateColumns.PARENT_UID, rawPlaybackState.parentUid?.toString())
-                        put(PlaybackStateColumns.INDEX, rawPlaybackState.index)
-                        put(PlaybackStateColumns.REPEAT_MODE, rawPlaybackState.repeatMode.intCode)
-                    }
-
-                insert(TABLE_STATE, null, stateData)
-            }
-        }
-    }
-
-    private fun writeRawQueueState(rawQueueState: RawQueueState?) {
-        writableDatabase.writeList(rawQueueState?.heap ?: listOf(), TABLE_QUEUE_HEAP) { i, song ->
-            ContentValues(2).apply {
-                put(BaseColumns._ID, i)
-                put(QueueHeapColumns.SONG_UID, unlikelyToBeNull(song).uid.toString())
-            }
-        }
-
-        val combinedMapping =
-            rawQueueState?.run {
-                if (shuffledMapping.isNotEmpty()) {
-                    orderedMapping.zip(shuffledMapping)
-                } else {
-                    orderedMapping.map { Pair(it, null) }
-                }
-            }
-
-        writableDatabase.writeList(combinedMapping ?: listOf(), TABLE_QUEUE_MAPPINGS) { i, pair ->
-            ContentValues(3).apply {
-                put(BaseColumns._ID, i)
-                put(QueueMappingColumns.ORDERED_INDEX, pair.first)
-                put(QueueMappingColumns.SHUFFLED_INDEX, pair.second)
-            }
-        }
-    }
-
-    /**
-     * A condensed representation of the playback state that can be persisted.
-     * @param parent The [MusicParent] item currently being played from.
-     * @param queueState The [Queue.SavedState]
-     * @param positionMs The current position in the currently played song, in ms
-     * @param repeatMode The current [RepeatMode].
-     */
-    data class SavedState(
-        val parent: MusicParent?,
-        val queueState: Queue.SavedState,
-        val positionMs: Long,
-        val repeatMode: RepeatMode,
-    )
-
-    /** A lower-level form of [SavedState] that contains individual field-based information. */
-    private data class RawPlaybackState(
-        /** @see Queue.SavedState.index */
-        val index: Int,
-        /** @see SavedState.positionMs */
-        val positionMs: Long,
-        /** @see SavedState.repeatMode */
-        val repeatMode: RepeatMode,
-        /**
-         * The [Music.UID] of the [Song] that was originally in the queue at [index]. This can be
-         * used to restore the currently playing item in the queue if the index mapping changed.
-         */
-        val songUid: Music.UID,
-        /** @see SavedState.parent */
-        val parentUid: Music.UID?
-    )
-
-    /** A lower-level form of [Queue.SavedState] that contains heap and mapping information. */
-    private data class RawQueueState(
-        /** @see Queue.SavedState.heap */
-        val heap: List<Song?>,
-        /** @see Queue.SavedState.orderedMapping */
-        val orderedMapping: List<Int>,
-        /** @see Queue.SavedState.shuffledMapping */
-        val shuffledMapping: List<Int>
-    )
-
-    /** Defines the columns used in the playback state table. */
-    private object PlaybackStateColumns {
-        /** @see RawPlaybackState.index */
-        const val INDEX = "queue_index"
-        /** @see RawPlaybackState.positionMs */
-        const val POSITION = "position"
-        /** @see RawPlaybackState.repeatMode */
-        const val REPEAT_MODE = "repeat_mode"
-        /** @see RawPlaybackState.songUid */
-        const val SONG_UID = "song_uid"
-        /** @see RawPlaybackState.parentUid */
-        const val PARENT_UID = "parent"
-    }
-
-    /** Defines the columns used in the queue heap table. */
-    private object QueueHeapColumns {
-        /** @see Music.UID */
-        const val SONG_UID = "song_uid"
-    }
-
-    /** Defines the columns used in the queue mapping table. */
-    private object QueueMappingColumns {
-        /** @see Queue.SavedState.orderedMapping */
-        const val ORDERED_INDEX = "ordered_index"
-        /** @see Queue.SavedState.shuffledMapping */
-        const val SHUFFLED_INDEX = "shuffled_index"
-    }
-
-    companion object {
-        private const val DB_NAME = "auxio_playback_state.db"
-        private const val DB_VERSION = 9
-        private const val TABLE_STATE = "playback_state"
-        private const val TABLE_QUEUE_HEAP = "queue_heap"
-        private const val TABLE_QUEUE_MAPPINGS = "queue_mapping"
-
-        @Volatile private var INSTANCE: PlaybackStateDatabase? = null
-
-        /**
-         * Get a singleton instance.
-         * @return The (possibly newly-created) singleton instance.
-         */
-        fun getInstance(context: Context): PlaybackStateDatabase {
-            val currentInstance = INSTANCE
-
-            if (currentInstance != null) {
-                return currentInstance
-            }
-
-            synchronized(this) {
-                val newInstance = PlaybackStateDatabase(context.applicationContext)
-                INSTANCE = newInstance
-                return newInstance
-            }
-        }
-    }
-}

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateManager.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021 Auxio Project
+ * Copyright (c) 2023 Auxio Project
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,17 +17,14 @@
  
 package org.oxycblt.auxio.playback.state
 
-import kotlinx.coroutines.Dispatchers
+import javax.inject.Inject
-import kotlinx.coroutines.withContext
 import org.oxycblt.auxio.BuildConfig
-import org.oxycblt.auxio.music.*
+import org.oxycblt.auxio.music.MusicParent
-import org.oxycblt.auxio.music.MusicStore
+import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.library.Library
+import org.oxycblt.auxio.playback.queue.EditableQueue
-import org.oxycblt.auxio.playback.state.PlaybackStateManager.Listener
+import org.oxycblt.auxio.playback.queue.Queue
 import org.oxycblt.auxio.util.logD
-import org.oxycblt.auxio.util.logE
 import org.oxycblt.auxio.util.logW
-import org.oxycblt.auxio.util.unlikelyToBeNull
 
 /**
  * Core playback state controller class.
@@ -36,48 +33,27 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * MediaSession is poorly designed. This class instead ful-fills this role.
  *
  * This should ***NOT*** be used outside of the playback module.
- * - If you want to use the playback state in the UI, use
+ * - If you want to use the playback state in the UI, use PlaybackViewModel as it can withstand
- * [org.oxycblt.auxio.playback.PlaybackViewModel] as it can withstand volatile UIs.
+ * volatile UIs.
  * - If you want to use the playback state with the ExoPlayer instance or system-side things, use
- * [org.oxycblt.auxio.playback.system.PlaybackService].
+ * PlaybackService.
  *
  * Internal consumers should usually use [Listener], however the component that manages the player
  * itself should instead use [InternalPlayer].
  *
- * All access should be done with [PlaybackStateManager.getInstance].
- *
  * @author Alexander Capehart (OxygenCobalt)
  */
-class PlaybackStateManager private constructor() {
+interface PlaybackStateManager {
-    private val musicStore = MusicStore.getInstance()
-    private val listeners = mutableListOf<Listener>()
-    @Volatile private var internalPlayer: InternalPlayer? = null
-    @Volatile private var pendingAction: InternalPlayer.Action? = null
-    @Volatile private var isInitialized = false
-
     /** The current [Queue]. */
-    val queue = Queue()
+    val queue: Queue
     /** The [MusicParent] currently being played. Null if playback is occurring from all songs. */
-    @Volatile
+    val parent: MusicParent?
-    var parent: MusicParent? = null // FIXME: Parent is interpreted wrong when nothing is playing.
-        private set
-
     /** The current [InternalPlayer] state. */
-    @Volatile
+    val playerState: InternalPlayer.State
-    var playerState = InternalPlayer.State.from(isPlaying = false, isAdvancing = false, 0)
-        private set
     /** The current [RepeatMode] */
-    @Volatile
+    var repeatMode: RepeatMode
-    var repeatMode = RepeatMode.NONE
+    /** The audio session ID of the internal player. Null if no internal player exists. */
-        set(value) {
-            field = value
-            notifyRepeatModeChanged()
-        }
-    /**
-     * The current audio session ID of the internal player. Null if [InternalPlayer] is unavailable.
-     */
     val currentAudioSessionId: Int?
-        get() = internalPlayer?.audioSessionId
 
     /**
      * Add a [Listener] to this instance. This can be used to receive changes in the playback state.
@@ -85,16 +61,7 @@ class PlaybackStateManager private constructor() {
      * @param listener The [Listener] to add.
      * @see Listener
      */
-    @Synchronized
+    fun addListener(listener: Listener)
-    fun addListener(listener: Listener) {
-        if (isInitialized) {
-            listener.onNewPlayback(queue, parent)
-            listener.onRepeatChanged(repeatMode)
-            listener.onStateChanged(playerState)
-        }
-
-        listeners.add(listener)
-    }
 
     /**
      * Remove a [Listener] from this instance, preventing it from receiving any further updates.
@@ -102,10 +69,7 @@ class PlaybackStateManager private constructor() {
      * the first place.
      * @see Listener
      */
-    @Synchronized
+    fun removeListener(listener: Listener)
-    fun removeListener(listener: Listener) {
-        listeners.remove(listener)
-    }
 
     /**
      * Register an [InternalPlayer] for this instance. This instance will handle translating the
@@ -114,42 +78,15 @@ class PlaybackStateManager private constructor() {
      * @param internalPlayer The [InternalPlayer] to register. Will do nothing if already
      * registered.
      */
-    @Synchronized
+    fun registerInternalPlayer(internalPlayer: InternalPlayer)
-    fun registerInternalPlayer(internalPlayer: InternalPlayer) {
-        if (this.internalPlayer != null) {
-            logW("Internal player is already registered")
-            return
-        }
-
-        if (isInitialized) {
-            internalPlayer.loadSong(queue.currentSong, playerState.isPlaying)
-            internalPlayer.seekTo(playerState.calculateElapsedPositionMs())
-            // See if there's any action that has been queued.
-            requestAction(internalPlayer)
-            // Once initialized, try to synchronize with the player state it has created.
-            synchronizeState(internalPlayer)
-        }
-
-        this.internalPlayer = internalPlayer
-    }
 
     /**
-     * Unregister the [InternalPlayer] from this instance, prevent it from recieving any further
+     * Unregister the [InternalPlayer] from this instance, prevent it from receiving any further
      * commands.
      * @param internalPlayer The [InternalPlayer] to unregister. Must be the current
      * [InternalPlayer]. Does nothing if invoked by another [InternalPlayer] implementation.
      */
-    @Synchronized
+    fun unregisterInternalPlayer(internalPlayer: InternalPlayer)
-    fun unregisterInternalPlayer(internalPlayer: InternalPlayer) {
-        if (this.internalPlayer !== internalPlayer) {
-            logW("Given internal player did not match current internal player")
-            return
-        }
-
-        this.internalPlayer = null
-    }
-
-    // --- PLAYING FUNCTIONS ---
 
     /**
      * Start new playback.
@@ -159,190 +96,81 @@ class PlaybackStateManager private constructor() {
      * collection of "All [Song]s".
      * @param shuffled Whether to shuffle or not.
      */
-    @Synchronized
+    fun play(song: Song?, parent: MusicParent?, queue: List<Song>, shuffled: Boolean)
-    fun play(song: Song?, parent: MusicParent?, queue: List<Song>, shuffled: Boolean) {
-        val internalPlayer = internalPlayer ?: return
-        // Set up parent and queue
-        this.parent = parent
-        this.queue.start(song, queue, shuffled)
-        // Notify components of changes
-        notifyNewPlayback()
-        internalPlayer.loadSong(this.queue.currentSong, true)
-        // Played something, so we are initialized now
-        isInitialized = true
-    }
-
-    // --- QUEUE FUNCTIONS ---
 
     /**
      * Go to the next [Song] in the queue. Will go to the first [Song] in the queue if there is no
      * [Song] ahead to skip to.
      */
-    @Synchronized
+    fun next()
-    fun next() {
-        val internalPlayer = internalPlayer ?: return
-        var play = true
-        if (!queue.goto(queue.index + 1)) {
-            queue.goto(0)
-            play = false
-        }
-        notifyIndexMoved()
-        internalPlayer.loadSong(queue.currentSong, play)
-    }
 
     /**
      * Go to the previous [Song] in the queue. Will rewind if there are no previous [Song]s to skip
      * to, or if configured to do so.
      */
-    @Synchronized
+    fun prev()
-    fun prev() {
-        val internalPlayer = internalPlayer ?: return
-
-        // If enabled, rewind before skipping back if the position is past 3 seconds [3000ms]
-        if (internalPlayer.shouldRewindWithPrev) {
-            rewind()
-            setPlaying(true)
-        } else {
-            if (!queue.goto(queue.index - 1)) {
-                queue.goto(0)
-            }
-            notifyIndexMoved()
-            internalPlayer.loadSong(queue.currentSong, true)
-        }
-    }
 
     /**
      * Play a [Song] at the given position in the queue.
      * @param index The position of the [Song] in the queue to start playing.
      */
-    @Synchronized
+    fun goto(index: Int)
-    fun goto(index: Int) {
-        val internalPlayer = internalPlayer ?: return
-        if (queue.goto(index)) {
-            notifyIndexMoved()
-            internalPlayer.loadSong(queue.currentSong, true)
-        }
-    }
-
-    /**
-     * Add a [Song] to the top of the queue.
-     * @param song The [Song] to add.
-     */
-    @Synchronized fun playNext(song: Song) = playNext(listOf(song))
 
     /**
      * Add [Song]s to the top of the queue.
      * @param songs The [Song]s to add.
      */
-    @Synchronized
+    fun playNext(songs: List<Song>)
-    fun playNext(songs: List<Song>) {
-        val internalPlayer = internalPlayer ?: return
-        when (queue.playNext(songs)) {
-            Queue.ChangeResult.MAPPING -> notifyQueueChanged(Queue.ChangeResult.MAPPING)
-            Queue.ChangeResult.SONG -> {
-                // Enqueueing actually started a new playback session from all songs.
-                parent = null
-                internalPlayer.loadSong(queue.currentSong, true)
-                notifyNewPlayback()
-            }
-            Queue.ChangeResult.INDEX -> error("Unreachable")
-        }
-    }
 
     /**
-     * Add a [Song] to the end of the queue.
+     * Add a [Song] to the top of the queue.
      * @param song The [Song] to add.
      */
-    @Synchronized fun addToQueue(song: Song) = addToQueue(listOf(song))
+    fun playNext(song: Song) = playNext(listOf(song))
 
     /**
      * Add [Song]s to the end of the queue.
      * @param songs The [Song]s to add.
      */
-    @Synchronized
+    fun addToQueue(songs: List<Song>)
-    fun addToQueue(songs: List<Song>) {
+
-        val internalPlayer = internalPlayer ?: return
+    /**
-        when (queue.addToQueue(songs)) {
+     * Add a [Song] to the end of the queue.
-            Queue.ChangeResult.MAPPING -> notifyQueueChanged(Queue.ChangeResult.MAPPING)
+     * @param song The [Song] to add.
-            Queue.ChangeResult.SONG -> {
+     */
-                // Enqueueing actually started a new playback session from all songs.
+    fun addToQueue(song: Song) = addToQueue(listOf(song))
-                parent = null
-                internalPlayer.loadSong(queue.currentSong, true)
-                notifyNewPlayback()
-            }
-            Queue.ChangeResult.INDEX -> error("Unreachable")
-        }
-    }
 
     /**
      * Move a [Song] in the queue.
      * @param src The position of the [Song] to move in the queue.
      * @param dst The destination position in the queue.
      */
-    @Synchronized
+    fun moveQueueItem(src: Int, dst: Int)
-    fun moveQueueItem(src: Int, dst: Int) {
-        logD("Moving item $src to position $dst")
-        notifyQueueChanged(queue.move(src, dst))
-    }
 
     /**
      * Remove a [Song] from the queue.
      * @param at The position of the [Song] to remove in the queue.
      */
-    @Synchronized
+    fun removeQueueItem(at: Int)
-    fun removeQueueItem(at: Int) {
-        val internalPlayer = internalPlayer ?: return
-        logD("Removing item at $at")
-        val change = queue.remove(at)
-        if (change == Queue.ChangeResult.SONG) {
-            internalPlayer.loadSong(queue.currentSong, playerState.isPlaying)
-        }
-        notifyQueueChanged(change)
-    }
 
     /**
      * (Re)shuffle or (Re)order this instance.
      * @param shuffled Whether to shuffle the queue or not.
      */
-    @Synchronized
+    fun reorder(shuffled: Boolean)
-    fun reorder(shuffled: Boolean) {
-        queue.reorder(shuffled)
-        notifyQueueReordered()
-    }
-
-    // --- INTERNAL PLAYER FUNCTIONS ---
 
     /**
      * Synchronize the state of this instance with the current [InternalPlayer].
      * @param internalPlayer The [InternalPlayer] to synchronize with. Must be the current
      * [InternalPlayer]. Does nothing if invoked by another [InternalPlayer] implementation.
      */
-    @Synchronized
+    fun synchronizeState(internalPlayer: InternalPlayer)
-    fun synchronizeState(internalPlayer: InternalPlayer) {
-        if (BuildConfig.DEBUG && this.internalPlayer !== internalPlayer) {
-            logW("Given internal player did not match current internal player")
-            return
-        }
-
-        val newState = internalPlayer.getState(queue.currentSong?.durationMs ?: 0)
-        if (newState != playerState) {
-            playerState = newState
-            notifyStateChanged()
-        }
-    }
 
     /**
      * Start a [InternalPlayer.Action] for the current [InternalPlayer] to handle eventually.
      * @param action The [InternalPlayer.Action] to perform.
      */
-    @Synchronized
+    fun startAction(action: InternalPlayer.Action)
-    fun startAction(action: InternalPlayer.Action) {
-        val internalPlayer = internalPlayer
-        if (internalPlayer == null || !internalPlayer.performAction(action)) {
-            logD("Internal player not present or did not consume action, waiting")
-            pendingAction = action
-        }
-    }
 
     /**
      * Request that the pending [InternalPlayer.Action] (if any) be passed to the given
@@ -350,213 +178,37 @@ class PlaybackStateManager private constructor() {
      * @param internalPlayer The [InternalPlayer] to synchronize with. Must be the current
      * [InternalPlayer]. Does nothing if invoked by another [InternalPlayer] implementation.
      */
-    @Synchronized
+    fun requestAction(internalPlayer: InternalPlayer)
-    fun requestAction(internalPlayer: InternalPlayer) {
-        if (BuildConfig.DEBUG && this.internalPlayer !== internalPlayer) {
-            logW("Given internal player did not match current internal player")
-            return
-        }
-
-        if (pendingAction?.let(internalPlayer::performAction) == true) {
-            logD("Pending action consumed")
-            pendingAction = null
-        }
-    }
 
     /**
      * Update whether playback is ongoing or not.
      * @param isPlaying Whether playback is ongoing or not.
      */
-    fun setPlaying(isPlaying: Boolean) {
+    fun setPlaying(isPlaying: Boolean)
-        internalPlayer?.setPlaying(isPlaying)
-    }
 
     /**
      * Seek to the given position in the currently playing [Song].
      * @param positionMs The position to seek to, in milliseconds.
      */
-    @Synchronized
+    fun seekTo(positionMs: Long)
-    fun seekTo(positionMs: Long) {
-        internalPlayer?.seekTo(positionMs)
-    }
 
     /** Rewind to the beginning of the currently playing [Song]. */
     fun rewind() = seekTo(0)
 
-    // --- PERSISTENCE FUNCTIONS ---
+    /**
+     * Converts the current state of this instance into a [SavedState].
+     * @return An immutable [SavedState] that is analogous to the current state, or null if nothing
+     * is currently playing.
+     */
+    fun toSavedState(): SavedState?
 
     /**
-     * Restore the previously saved state (if any) and apply it to the playback state.
+     * Restores this instance from the given [SavedState].
-     * @param database The [PlaybackStateDatabase] to load from.
+     * @param savedState The [SavedState] to restore from.
-     * @param force Whether to do a restore regardless of any prior playback state.
+     * @param destructive Whether to disregard the prior playback state and overwrite it with this
-     * @return If the state was restored, false otherwise.
+     * [SavedState].
      */
-    suspend fun restoreState(database: PlaybackStateDatabase, force: Boolean): Boolean {
+    fun applySavedState(savedState: SavedState, destructive: Boolean)
-        if (isInitialized && !force) {
-            // Already initialized and not forcing a restore, nothing to do.
-            return false
-        }
-
-        val library = musicStore.library ?: return false
-        val internalPlayer = internalPlayer ?: return false
-        val state =
-            try {
-                withContext(Dispatchers.IO) { database.read(library) }
-            } catch (e: Exception) {
-                logE("Unable to restore playback state.")
-                logE(e.stackTraceToString())
-                return false
-            }
-
-        // Translate the state we have just read into a usable playback state for this
-        // instance.
-        return synchronized(this) {
-            // State could have changed while we were loading, so check if we were initialized
-            // now before applying the state.
-            if (state != null && (!isInitialized || force)) {
-                parent = state.parent
-                queue.applySavedState(state.queueState)
-                repeatMode = state.repeatMode
-                notifyNewPlayback()
-                notifyRepeatModeChanged()
-                // Continuing playback after drastic state updates is a bad idea, so pause.
-                internalPlayer.loadSong(queue.currentSong, false)
-                internalPlayer.seekTo(state.positionMs)
-                isInitialized = true
-                true
-            } else {
-                false
-            }
-        }
-    }
-
-    /**
-     * Save the current state.
-     * @param database The [PlaybackStateDatabase] to save the state to.
-     * @return If state was saved, false otherwise.
-     */
-    suspend fun saveState(database: PlaybackStateDatabase): Boolean {
-        logD("Saving state to DB")
-        // Create the saved state from the current playback state.
-        val state =
-            synchronized(this) {
-                queue.toSavedState()?.let {
-                    PlaybackStateDatabase.SavedState(
-                        parent = parent,
-                        queueState = it,
-                        positionMs = playerState.calculateElapsedPositionMs(),
-                        repeatMode = repeatMode)
-                }
-            }
-        return try {
-            withContext(Dispatchers.IO) { database.write(state) }
-            true
-        } catch (e: Exception) {
-            logE("Unable to save playback state.")
-            logE(e.stackTraceToString())
-            false
-        }
-    }
-
-    /**
-     * Clear the current state.
-     * @param database The [PlaybackStateDatabase] to clear te state from
-     * @return If the state was cleared, false otherwise.
-     */
-    suspend fun wipeState(database: PlaybackStateDatabase) =
-        try {
-            logD("Wiping state")
-            withContext(Dispatchers.IO) { database.write(null) }
-            true
-        } catch (e: Exception) {
-            logE("Unable to wipe playback state.")
-            logE(e.stackTraceToString())
-            false
-        }
-
-    /**
-     * Update the playback state to align with a new [Library].
-     * @param newLibrary The new [Library] that was recently loaded.
-     */
-    @Synchronized
-    fun sanitize(newLibrary: Library) {
-        if (!isInitialized) {
-            // Nothing playing, nothing to do.
-            logD("Not initialized, no need to sanitize")
-            return
-        }
-
-        val internalPlayer = internalPlayer ?: return
-
-        logD("Sanitizing state")
-
-        // While we could just save and reload the state, we instead sanitize the state
-        // at runtime for better performance (and to sidestep a co-routine on behalf of the caller).
-
-        // Sanitize parent
-        parent =
-            parent?.let {
-                when (it) {
-                    is Album -> newLibrary.sanitize(it)
-                    is Artist -> newLibrary.sanitize(it)
-                    is Genre -> newLibrary.sanitize(it)
-                }
-            }
-
-        // Sanitize the queue.
-        queue.toSavedState()?.let { state ->
-            queue.applySavedState(state.remap { newLibrary.sanitize(unlikelyToBeNull(it)) })
-        }
-
-        notifyNewPlayback()
-
-        val oldPosition = playerState.calculateElapsedPositionMs()
-        // Continuing playback while also possibly doing drastic state updates is
-        // a bad idea, so pause.
-        internalPlayer.loadSong(queue.currentSong, false)
-        if (queue.currentSong != null) {
-            // Internal player may have reloaded the media item, re-seek to the previous position
-            seekTo(oldPosition)
-        }
-    }
-
-    // --- CALLBACKS ---
-
-    private fun notifyIndexMoved() {
-        for (callback in listeners) {
-            callback.onIndexMoved(queue)
-        }
-    }
-
-    private fun notifyQueueChanged(change: Queue.ChangeResult) {
-        for (callback in listeners) {
-            callback.onQueueChanged(queue, change)
-        }
-    }
-
-    private fun notifyQueueReordered() {
-        for (callback in listeners) {
-            callback.onQueueReordered(queue)
-        }
-    }
-
-    private fun notifyNewPlayback() {
-        for (callback in listeners) {
-            callback.onNewPlayback(queue, parent)
-        }
-    }
-
-    private fun notifyStateChanged() {
-        for (callback in listeners) {
-            callback.onStateChanged(playerState)
-        }
-    }
-
-    private fun notifyRepeatModeChanged() {
-        for (callback in listeners) {
-            callback.onRepeatChanged(repeatMode)
-        }
-    }
 
     /**
      * The interface for receiving updates from [PlaybackStateManager]. Add the listener to
@@ -604,25 +256,318 @@ class PlaybackStateManager private constructor() {
         fun onRepeatChanged(repeatMode: RepeatMode) {}
     }
 
-    companion object {
+    /**
-        @Volatile private var INSTANCE: PlaybackStateManager? = null
+     * A condensed representation of the playback state that can be persisted.
+     * @param parent The [MusicParent] item currently being played from.
+     * @param queueState The [Queue.SavedState]
+     * @param positionMs The current position in the currently played song, in ms
+     * @param repeatMode The current [RepeatMode].
+     */
+    data class SavedState(
+        val parent: MusicParent?,
+        val queueState: Queue.SavedState,
+        val positionMs: Long,
+        val repeatMode: RepeatMode,
+    )
+}
 
-        /**
+class PlaybackStateManagerImpl @Inject constructor() : PlaybackStateManager {
-         * Get a singleton instance.
+    private val listeners = mutableListOf<PlaybackStateManager.Listener>()
-         * @return The (possibly newly-created) singleton instance.
+    @Volatile private var internalPlayer: InternalPlayer? = null
-         */
+    @Volatile private var pendingAction: InternalPlayer.Action? = null
-        fun getInstance(): PlaybackStateManager {
+    @Volatile private var isInitialized = false
-            val currentInstance = INSTANCE
 
-            if (currentInstance != null) {
+    override val queue = EditableQueue()
-                return currentInstance
+    @Volatile
+    override var parent: MusicParent? =
+        null // FIXME: Parent is interpreted wrong when nothing is playing.
+        private set
+    @Volatile
+    override var playerState = InternalPlayer.State.from(isPlaying = false, isAdvancing = false, 0)
+        private set
+    @Volatile
+    override var repeatMode = RepeatMode.NONE
+        set(value) {
+            field = value
+            notifyRepeatModeChanged()
+        }
+    override val currentAudioSessionId: Int?
+        get() = internalPlayer?.audioSessionId
+
+    @Synchronized
+    override fun addListener(listener: PlaybackStateManager.Listener) {
+        if (isInitialized) {
+            listener.onNewPlayback(queue, parent)
+            listener.onRepeatChanged(repeatMode)
+            listener.onStateChanged(playerState)
+        }
+
+        listeners.add(listener)
+    }
+
+    @Synchronized
+    override fun removeListener(listener: PlaybackStateManager.Listener) {
+        listeners.remove(listener)
+    }
+
+    @Synchronized
+    override fun registerInternalPlayer(internalPlayer: InternalPlayer) {
+        if (this.internalPlayer != null) {
+            logW("Internal player is already registered")
+            return
+        }
+
+        if (isInitialized) {
+            internalPlayer.loadSong(queue.currentSong, playerState.isPlaying)
+            internalPlayer.seekTo(playerState.calculateElapsedPositionMs())
+            // See if there's any action that has been queued.
+            requestAction(internalPlayer)
+            // Once initialized, try to synchronize with the player state it has created.
+            synchronizeState(internalPlayer)
+        }
+
+        this.internalPlayer = internalPlayer
+    }
+
+    @Synchronized
+    override fun unregisterInternalPlayer(internalPlayer: InternalPlayer) {
+        if (this.internalPlayer !== internalPlayer) {
+            logW("Given internal player did not match current internal player")
+            return
+        }
+
+        this.internalPlayer = null
+    }
+
+    // --- PLAYING FUNCTIONS ---
+
+    @Synchronized
+    override fun play(song: Song?, parent: MusicParent?, queue: List<Song>, shuffled: Boolean) {
+        val internalPlayer = internalPlayer ?: return
+        // Set up parent and queue
+        this.parent = parent
+        this.queue.start(song, queue, shuffled)
+        // Notify components of changes
+        notifyNewPlayback()
+        internalPlayer.loadSong(this.queue.currentSong, true)
+        // Played something, so we are initialized now
+        isInitialized = true
+    }
+
+    // --- QUEUE FUNCTIONS ---
+
+    @Synchronized
+    override fun next() {
+        val internalPlayer = internalPlayer ?: return
+        var play = true
+        if (!queue.goto(queue.index + 1)) {
+            queue.goto(0)
+            play = repeatMode == RepeatMode.ALL
+        }
+        notifyIndexMoved()
+        internalPlayer.loadSong(queue.currentSong, play)
+    }
+
+    @Synchronized
+    override fun prev() {
+        val internalPlayer = internalPlayer ?: return
+
+        // If enabled, rewind before skipping back if the position is past 3 seconds [3000ms]
+        if (internalPlayer.shouldRewindWithPrev) {
+            rewind()
+            setPlaying(true)
+        } else {
+            if (!queue.goto(queue.index - 1)) {
+                queue.goto(0)
             }
+            notifyIndexMoved()
+            internalPlayer.loadSong(queue.currentSong, true)
+        }
+    }
 
-            synchronized(this) {
+    @Synchronized
-                val newInstance = PlaybackStateManager()
+    override fun goto(index: Int) {
-                INSTANCE = newInstance
+        val internalPlayer = internalPlayer ?: return
-                return newInstance
+        if (queue.goto(index)) {
+            notifyIndexMoved()
+            internalPlayer.loadSong(queue.currentSong, true)
+        }
+    }
+
+    @Synchronized
+    override fun playNext(songs: List<Song>) {
+        val internalPlayer = internalPlayer ?: return
+        when (queue.playNext(songs)) {
+            Queue.ChangeResult.MAPPING -> notifyQueueChanged(Queue.ChangeResult.MAPPING)
+            Queue.ChangeResult.SONG -> {
+                // Enqueueing actually started a new playback session from all songs.
+                parent = null
+                internalPlayer.loadSong(queue.currentSong, true)
+                notifyNewPlayback()
             }
+            Queue.ChangeResult.INDEX -> error("Unreachable")
+        }
+    }
+
+    @Synchronized
+    override fun addToQueue(songs: List<Song>) {
+        val internalPlayer = internalPlayer ?: return
+        when (queue.addToQueue(songs)) {
+            Queue.ChangeResult.MAPPING -> notifyQueueChanged(Queue.ChangeResult.MAPPING)
+            Queue.ChangeResult.SONG -> {
+                // Enqueueing actually started a new playback session from all songs.
+                parent = null
+                internalPlayer.loadSong(queue.currentSong, true)
+                notifyNewPlayback()
+            }
+            Queue.ChangeResult.INDEX -> error("Unreachable")
+        }
+    }
+
+    @Synchronized
+    override fun moveQueueItem(src: Int, dst: Int) {
+        logD("Moving item $src to position $dst")
+        notifyQueueChanged(queue.move(src, dst))
+    }
+
+    @Synchronized
+    override fun removeQueueItem(at: Int) {
+        val internalPlayer = internalPlayer ?: return
+        logD("Removing item at $at")
+        val change = queue.remove(at)
+        if (change == Queue.ChangeResult.SONG) {
+            internalPlayer.loadSong(queue.currentSong, playerState.isPlaying)
+        }
+        notifyQueueChanged(change)
+    }
+
+    @Synchronized
+    override fun reorder(shuffled: Boolean) {
+        queue.reorder(shuffled)
+        notifyQueueReordered()
+    }
+
+    // --- INTERNAL PLAYER FUNCTIONS ---
+
+    @Synchronized
+    override fun synchronizeState(internalPlayer: InternalPlayer) {
+        if (BuildConfig.DEBUG && this.internalPlayer !== internalPlayer) {
+            logW("Given internal player did not match current internal player")
+            return
+        }
+
+        val newState = internalPlayer.getState(queue.currentSong?.durationMs ?: 0)
+        if (newState != playerState) {
+            playerState = newState
+            notifyStateChanged()
+        }
+    }
+
+    @Synchronized
+    override fun startAction(action: InternalPlayer.Action) {
+        val internalPlayer = internalPlayer
+        if (internalPlayer == null || !internalPlayer.performAction(action)) {
+            logD("Internal player not present or did not consume action, waiting")
+            pendingAction = action
+        }
+    }
+
+    @Synchronized
+    override fun requestAction(internalPlayer: InternalPlayer) {
+        if (BuildConfig.DEBUG && this.internalPlayer !== internalPlayer) {
+            logW("Given internal player did not match current internal player")
+            return
+        }
+
+        if (pendingAction?.let(internalPlayer::performAction) == true) {
+            logD("Pending action consumed")
+            pendingAction = null
+        }
+    }
+
+    @Synchronized
+    override fun setPlaying(isPlaying: Boolean) {
+        internalPlayer?.setPlaying(isPlaying)
+    }
+
+    @Synchronized
+    override fun seekTo(positionMs: Long) {
+        internalPlayer?.seekTo(positionMs)
+    }
+
+    // --- PERSISTENCE FUNCTIONS ---
+
+    @Synchronized
+    override fun toSavedState() =
+        queue.toSavedState()?.let {
+            PlaybackStateManager.SavedState(
+                parent = parent,
+                queueState = it,
+                positionMs = playerState.calculateElapsedPositionMs(),
+                repeatMode = repeatMode)
+        }
+
+    @Synchronized
+    override fun applySavedState(
+        savedState: PlaybackStateManager.SavedState,
+        destructive: Boolean
+    ) {
+        if (isInitialized && !destructive) {
+            return
+        }
+        val internalPlayer = internalPlayer ?: return
+        logD("Restoring state $savedState")
+
+        parent = savedState.parent
+        queue.applySavedState(savedState.queueState)
+        repeatMode = savedState.repeatMode
+        notifyNewPlayback()
+
+        // Continuing playback while also possibly doing drastic state updates is
+        // a bad idea, so pause.
+        internalPlayer.loadSong(queue.currentSong, false)
+        if (queue.currentSong != null) {
+            // Internal player may have reloaded the media item, re-seek to the previous position
+            seekTo(savedState.positionMs)
+        }
+        isInitialized = true
+    }
+
+    // --- CALLBACKS ---
+
+    private fun notifyIndexMoved() {
+        for (callback in listeners) {
+            callback.onIndexMoved(queue)
+        }
+    }
+
+    private fun notifyQueueChanged(change: Queue.ChangeResult) {
+        for (callback in listeners) {
+            callback.onQueueChanged(queue, change)
+        }
+    }
+
+    private fun notifyQueueReordered() {
+        for (callback in listeners) {
+            callback.onQueueReordered(queue)
+        }
+    }
+
+    private fun notifyNewPlayback() {
+        for (callback in listeners) {
+            callback.onNewPlayback(queue, parent)
+        }
+    }
+
+    private fun notifyStateChanged() {
+        for (callback in listeners) {
+            callback.onStateChanged(playerState)
+        }
+    }
+
+    private fun notifyRepeatModeChanged() {
+        for (callback in listeners) {
+            callback.onRepeatChanged(repeatMode)
         }
     }
 }

app/src/main/java/org/oxycblt/auxio/playback/system/MediaButtonReceiver.kt

@@ -22,15 +22,19 @@ import android.content.ComponentName
 import android.content.Context
 import android.content.Intent
 import androidx.core.content.ContextCompat
+import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
 
 /**
  * A [BroadcastReceiver] that forwards [Intent.ACTION_MEDIA_BUTTON] [Intent]s to [PlaybackService].
  * @author Alexander Capehart (OxygenCobalt)
  */
+@AndroidEntryPoint
 class MediaButtonReceiver : BroadcastReceiver() {
+    @Inject lateinit var playbackManager: PlaybackStateManager
+
     override fun onReceive(context: Context, intent: Intent) {
-        val playbackManager = PlaybackStateManager.getInstance()
         if (playbackManager.queue.currentSong != null) {
             // We have a song, so we can assume that the service will start a foreground state.
             // At least, I hope. Again, *this is why we don't do this*. I cannot describe how

app/src/main/java/org/oxycblt/auxio/playback/system/MediaSessionComponent.kt

@@ -27,28 +27,36 @@ import android.support.v4.media.MediaMetadataCompat
 import android.support.v4.media.session.MediaSessionCompat
 import android.support.v4.media.session.PlaybackStateCompat
 import androidx.media.session.MediaButtonReceiver
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
 import org.oxycblt.auxio.BuildConfig
 import org.oxycblt.auxio.R
 import org.oxycblt.auxio.image.BitmapProvider
 import org.oxycblt.auxio.image.ImageSettings
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.resolveNames
 import org.oxycblt.auxio.playback.ActionMode
 import org.oxycblt.auxio.playback.PlaybackSettings
+import org.oxycblt.auxio.playback.queue.Queue
 import org.oxycblt.auxio.playback.state.InternalPlayer
 import org.oxycblt.auxio.playback.state.PlaybackStateManager
-import org.oxycblt.auxio.playback.state.Queue
 import org.oxycblt.auxio.playback.state.RepeatMode
 import org.oxycblt.auxio.util.logD
 
 /**
  * A component that mirrors the current playback state into the [MediaSessionCompat] and
  * [NotificationComponent].
- * @param context [Context] required to initialize components.
- * @param listener [Listener] to forward notification updates to.
  * @author Alexander Capehart (OxygenCobalt)
  */
-class MediaSessionComponent(private val context: Context, private val listener: Listener) :
+class MediaSessionComponent
+@Inject
+constructor(
+    @ApplicationContext private val context: Context,
+    private val bitmapProvider: BitmapProvider,
+    private val playbackManager: PlaybackStateManager,
+    private val playbackSettings: PlaybackSettings,
+) :
     MediaSessionCompat.Callback(),
     PlaybackStateManager.Listener,
     ImageSettings.Listener,
@@ -59,11 +67,9 @@ class MediaSessionComponent(private val context: Context, private val listener:
             setQueueTitle(context.getString(R.string.lbl_queue))
         }
 
-    private val playbackManager = PlaybackStateManager.getInstance()
-    private val playbackSettings = PlaybackSettings.from(context)
-
     private val notification = NotificationComponent(context, mediaSession.sessionToken)
-    private val provider = BitmapProvider(context)
+
+    private var listener: Listener? = null
 
     init {
         playbackManager.addListener(this)
@@ -79,12 +85,21 @@ class MediaSessionComponent(private val context: Context, private val listener:
         MediaButtonReceiver.handleIntent(mediaSession, intent)
     }
 
+    /**
+     * Register a [Listener] for notification updates to this service.
+     * @param listener The [Listener] to register.
+     */
+    fun registerListener(listener: Listener) {
+        this.listener = listener
+    }
+
     /**
      * Release this instance, closing the [MediaSessionCompat] and preventing any further updates to
      * the [NotificationComponent].
      */
     fun release() {
-        provider.release()
+        listener = null
+        bitmapProvider.release()
         playbackSettings.unregisterListener(this)
         playbackManager.removeListener(this)
         mediaSession.apply {
@@ -134,8 +149,8 @@ class MediaSessionComponent(private val context: Context, private val listener:
     override fun onStateChanged(state: InternalPlayer.State) {
         invalidateSessionState()
         notification.updatePlaying(playbackManager.playerState.isPlaying)
-        if (!provider.isBusy) {
+        if (!bitmapProvider.isBusy) {
-            listener.onPostNotification(notification)
+            listener?.onPostNotification(notification)
         }
     }
 
@@ -271,7 +286,7 @@ class MediaSessionComponent(private val context: Context, private val listener:
         // Populate MediaMetadataCompat. For efficiency, cache some fields that are re-used
         // several times.
         val title = song.resolveName(context)
-        val artist = song.resolveArtistContents(context)
+        val artist = song.artists.resolveNames(context)
         val builder =
             MediaMetadataCompat.Builder()
                 .putText(MediaMetadataCompat.METADATA_KEY_TITLE, title)
@@ -281,14 +296,14 @@ class MediaSessionComponent(private val context: Context, private val listener:
                 .putText(MediaMetadataCompat.METADATA_KEY_ARTIST, artist)
                 .putText(
                     MediaMetadataCompat.METADATA_KEY_ALBUM_ARTIST,
-                    song.album.resolveArtistContents(context))
+                    song.album.artists.resolveNames(context))
                 .putText(MediaMetadataCompat.METADATA_KEY_AUTHOR, artist)
                 .putText(MediaMetadataCompat.METADATA_KEY_COMPOSER, artist)
                 .putText(MediaMetadataCompat.METADATA_KEY_WRITER, artist)
                 .putText(
                     METADATA_KEY_PARENT,
                     parent?.resolveName(context) ?: context.getString(R.string.lbl_all_songs))
-                .putText(MediaMetadataCompat.METADATA_KEY_GENRE, song.resolveGenreContents(context))
+                .putText(MediaMetadataCompat.METADATA_KEY_GENRE, song.genres.resolveNames(context))
                 .putText(MediaMetadataCompat.METADATA_KEY_DISPLAY_TITLE, title)
                 .putText(MediaMetadataCompat.METADATA_KEY_DISPLAY_SUBTITLE, artist)
                 .putText(
@@ -300,14 +315,14 @@ class MediaSessionComponent(private val context: Context, private val listener:
             builder.putLong(MediaMetadataCompat.METADATA_KEY_TRACK_NUMBER, it.toLong())
         }
         song.disc?.let {
-            builder.putLong(MediaMetadataCompat.METADATA_KEY_DISC_NUMBER, it.toLong())
+            builder.putLong(MediaMetadataCompat.METADATA_KEY_DISC_NUMBER, it.number.toLong())
         }
         song.date?.let { builder.putString(MediaMetadataCompat.METADATA_KEY_DATE, it.toString()) }
 
         // We are normally supposed to use URIs for album art, but that removes some of the
         // nice things we can do like square cropping or high quality covers. Instead,
         // we load a full-size bitmap into the media session and take the performance hit.
-        provider.load(
+        bitmapProvider.load(
             song,
             object : BitmapProvider.Target {
                 override fun onCompleted(bitmap: Bitmap?) {
@@ -316,7 +331,7 @@ class MediaSessionComponent(private val context: Context, private val listener:
                     val metadata = builder.build()
                     mediaSession.setMetadata(metadata)
                     notification.updateMetadata(metadata)
-                    listener.onPostNotification(notification)
+                    listener?.onPostNotification(notification)
                 }
             })
     }
@@ -334,7 +349,7 @@ class MediaSessionComponent(private val context: Context, private val listener:
                         // as it's used to request a song to be played from the queue.
                         .setMediaId(song.uid.toString())
                         .setTitle(song.resolveName(context))
-                        .setSubtitle(song.resolveArtistContents(context))
+                        .setSubtitle(song.artists.resolveNames(context))
                         // Since we usually have to load many songs into the queue, use the
                         // MediaStore URI instead of loading a bitmap.
                         .setIconUri(song.album.coverUri)
@@ -402,8 +417,8 @@ class MediaSessionComponent(private val context: Context, private val listener:
             else -> notification.updateRepeatMode(playbackManager.repeatMode)
         }
 
-        if (!provider.isBusy) {
+        if (!bitmapProvider.isBusy) {
-            listener.onPostNotification(notification)
+            listener?.onPostNotification(notification)
         }
     }