music: rework picker system

Rework the music picker system to be a reactive, viewmodel-based system
instead of a janky UI system.

This should make it much easier to maintain and extend in the future.

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

@@ -34,6 +34,7 @@ import com.google.android.material.transition.MaterialFadeThrough
 import kotlin.math.max
 import kotlin.math.min
 import org.oxycblt.auxio.databinding.FragmentMainBinding
+import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.playback.PlaybackSheetBehavior
@@ -124,7 +125,9 @@ class MainFragment :
 
         collect(navModel.mainNavigationAction, ::handleMainNavigation)
         collect(navModel.exploreNavigationItem, ::handleExploreNavigation)
+        collect(navModel.exploreNavigationArtists, ::handleExplorePicker)
         collectImmediately(playbackModel.song, ::updateSong)
+        collect(playbackModel.artistPlaybackPickerSong, ::handlePlaybackPicker)
     }
 
     override fun onStart() {
@@ -213,14 +216,6 @@ class MainFragment :
         return true
     }
 
-    private fun updateSong(song: Song?) {
-        if (song != null) {
-            tryUnhideAll()
-        } else {
-            tryHideAll()
-        }
-    }
-
     private fun handleMainNavigation(action: MainNavigationAction?) {
         if (action == null) return
 
@@ -239,6 +234,32 @@ class MainFragment :
         }
     }
 
+    private fun handleExplorePicker(items: List<Artist>?) {
+        if (items != null) {
+            navModel.mainNavigateTo(MainNavigationAction.Directions(
+                MainFragmentDirections.actionPickNavigationArtist(items.map { it.uid }.toTypedArray())
+            ))
+            navModel.finishExploreNavigation()
+        }
+    }
+
+    private fun updateSong(song: Song?) {
+        if (song != null) {
+            tryUnhideAll()
+        } else {
+            tryHideAll()
+        }
+    }
+
+    private fun handlePlaybackPicker(song: Song?) {
+        if (song != null) {
+            navModel.mainNavigateTo(MainNavigationAction.Directions(
+                MainFragmentDirections.actionPickPlaybackArtist(song.uid)
+            ))
+            playbackModel.finishPlaybackArtistPicker()
+        }
+    }
+
     private fun tryExpandAll() {
         val binding = requireBinding()
         val playbackSheetBehavior =

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

@@ -39,9 +39,8 @@ import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.music.Sort
-import org.oxycblt.auxio.music.picker.PickerMode
 import org.oxycblt.auxio.settings.Settings
-import org.oxycblt.auxio.ui.fragment.MusicFragment
+import org.oxycblt.auxio.ui.fragment.MenuFragment
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.util.canScroll
 import org.oxycblt.auxio.util.collect
@@ -56,7 +55,7 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * @author OxygenCobalt
  */
 class AlbumDetailFragment :
-    MusicFragment<FragmentDetailBinding>(),
+    MenuFragment<FragmentDetailBinding>(),
     Toolbar.OnMenuItemClickListener,
     AlbumDetailAdapter.Listener {
     private val detailModel: DetailViewModel by activityViewModels()
@@ -127,7 +126,7 @@ class AlbumDetailFragment :
             null,
             MusicMode.ALBUMS -> playbackModel.playFromAlbum(item)
             MusicMode.SONGS -> playbackModel.playFromAll(item)
-            MusicMode.ARTISTS -> doArtistDependentAction(item, PickerMode.PLAY)
+            MusicMode.ARTISTS -> playbackModel.playFromArtist(item)
             else -> error("Unexpected playback mode: ${settings.detailPlaybackMode}")
         }
     }
@@ -164,7 +163,7 @@ class AlbumDetailFragment :
     }
 
     override fun onNavigateToArtist() {
-        navigateToArtist(unlikelyToBeNull(detailModel.currentAlbum.value))
+        navModel.exploreNavigateTo(unlikelyToBeNull(detailModel.currentAlbum.value).artists)
     }
 
     private fun handleItemChange(album: Album?) {

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

@@ -37,9 +37,8 @@ import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.music.Sort
-import org.oxycblt.auxio.music.picker.PickerMode
 import org.oxycblt.auxio.settings.Settings
-import org.oxycblt.auxio.ui.fragment.MusicFragment
+import org.oxycblt.auxio.ui.fragment.MenuFragment
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.util.collect
 import org.oxycblt.auxio.util.collectImmediately
@@ -53,9 +52,7 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * @author OxygenCobalt
  */
 class ArtistDetailFragment :
-    MusicFragment<FragmentDetailBinding>(),
+    MenuFragment<FragmentDetailBinding>(), Toolbar.OnMenuItemClickListener, DetailAdapter.Listener {
-    Toolbar.OnMenuItemClickListener,
-    DetailAdapter.Listener {
     private val detailModel: DetailViewModel by activityViewModels()
 
     private val args: ArtistDetailFragmentArgs by navArgs()
@@ -123,7 +120,7 @@ class ArtistDetailFragment :
                             item, unlikelyToBeNull(detailModel.currentArtist.value))
                     MusicMode.SONGS -> playbackModel.playFromAll(item)
                     MusicMode.ALBUMS -> playbackModel.playFromAlbum(item)
-                    MusicMode.ARTISTS -> doArtistDependentAction(item, PickerMode.PLAY)
+                    MusicMode.ARTISTS -> playbackModel.playFromArtist(item)
                     else -> error("Unexpected playback mode: ${settings.detailPlaybackMode}")
                 }
             }

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

@@ -38,9 +38,8 @@ import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.music.Sort
-import org.oxycblt.auxio.music.picker.PickerMode
 import org.oxycblt.auxio.settings.Settings
-import org.oxycblt.auxio.ui.fragment.MusicFragment
+import org.oxycblt.auxio.ui.fragment.MenuFragment
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.util.collect
 import org.oxycblt.auxio.util.collectImmediately
@@ -54,9 +53,7 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * @author OxygenCobalt
  */
 class GenreDetailFragment :
-    MusicFragment<FragmentDetailBinding>(),
+    MenuFragment<FragmentDetailBinding>(), Toolbar.OnMenuItemClickListener, DetailAdapter.Listener {
-    Toolbar.OnMenuItemClickListener,
-    DetailAdapter.Listener {
     private val detailModel: DetailViewModel by activityViewModels()
 
     private val args: GenreDetailFragmentArgs by navArgs()
@@ -125,7 +122,7 @@ class GenreDetailFragment :
                             item, unlikelyToBeNull(detailModel.currentGenre.value))
                     MusicMode.SONGS -> playbackModel.playFromAll(item)
                     MusicMode.ALBUMS -> playbackModel.playFromAlbum(item)
-                    MusicMode.ARTISTS -> doArtistDependentAction(item, PickerMode.PLAY)
+                    MusicMode.ARTISTS -> playbackModel.playFromArtist(item)
                     else -> error("Unexpected playback mode: ${settings.detailPlaybackMode}")
                 }
             else -> error("Unexpected datatype: ${item::class.simpleName}")

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

@@ -23,7 +23,7 @@ import androidx.fragment.app.Fragment
 import org.oxycblt.auxio.databinding.FragmentHomeListBinding
 import org.oxycblt.auxio.home.HomeViewModel
 import org.oxycblt.auxio.ui.fastscroll.FastScrollRecyclerView
-import org.oxycblt.auxio.ui.fragment.MusicFragment
+import org.oxycblt.auxio.ui.fragment.MenuFragment
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.ui.recycler.MenuItemListener
 import org.oxycblt.auxio.util.androidActivityViewModels
@@ -33,7 +33,7 @@ import org.oxycblt.auxio.util.androidActivityViewModels
  * @author OxygenCobalt
  */
 abstract class HomeListFragment<T : Item> :
-    MusicFragment<FragmentHomeListBinding>(),
+    MenuFragment<FragmentHomeListBinding>(),
     MenuItemListener,
     FastScrollRecyclerView.PopupProvider,
     FastScrollRecyclerView.OnFastScrollListener {

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

@@ -28,7 +28,6 @@ import org.oxycblt.auxio.music.MusicMode
 import org.oxycblt.auxio.music.MusicParent
 import org.oxycblt.auxio.music.Song
 import org.oxycblt.auxio.music.Sort
-import org.oxycblt.auxio.music.picker.PickerMode
 import org.oxycblt.auxio.playback.formatDurationMs
 import org.oxycblt.auxio.playback.secsToMs
 import org.oxycblt.auxio.settings.Settings
@@ -110,7 +109,7 @@ class SongListFragment : HomeListFragment<Song>() {
         when (settings.libPlaybackMode) {
             MusicMode.SONGS -> playbackModel.playFromAll(item)
             MusicMode.ALBUMS -> playbackModel.playFromAlbum(item)
-            MusicMode.ARTISTS -> doArtistDependentAction(item, PickerMode.PLAY)
+            MusicMode.ARTISTS -> playbackModel.playFromArtist(item)
             else -> error("Unexpected playback mode: ${settings.libPlaybackMode}")
         }
     }

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

@@ -204,8 +204,8 @@ abstract class MediaStoreExtractor(
 
         // 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 there are some
+        // needed since MetadataLayer will fill this in for us, but I'd imagine there
-        // obscure formats where genre support is only really covered by this.
+        // are some obscure formats where genre support is only really covered by this.
         context.contentResolverSafe.useQuery(
             MediaStore.Audio.Genres.EXTERNAL_CONTENT_URI,
             arrayOf(MediaStore.Audio.Genres._ID, MediaStore.Audio.Genres.NAME)) { genreCursor ->

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

@@ -51,7 +51,7 @@ fun String.parseYear() = toIntOrNull()?.toDate()
 /** Parse an ISO-8601 time-stamp from this field into a [Date]. */
 fun String.parseTimestamp() = Date.from(this)
 
-/** Parse a string by [selector], also handling string escaping. */
+/** Split a string by [selector], also handling escaping. */
 inline fun String.splitEscaped(selector: (Char) -> Boolean): MutableList<String> {
     val split = mutableListOf<String>()
     var currentString = ""

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

@@ -0,0 +1,48 @@
+/*
+ * 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.picker
+
+import android.os.Bundle
+import androidx.fragment.app.activityViewModels
+import androidx.navigation.fragment.findNavController
+import androidx.navigation.fragment.navArgs
+import org.oxycblt.auxio.databinding.DialogMusicPickerBinding
+import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.ui.NavigationViewModel
+import org.oxycblt.auxio.ui.recycler.Item
+import org.oxycblt.auxio.util.collectImmediately
+
+/**
+ * The [ArtistPickerDialog] for ambiguous artist navigation operations.
+ * @author OxygenCobalt
+ */
+class ArtistNavigationPickerDialog : ArtistPickerDialog() {
+    private val navModel: NavigationViewModel by activityViewModels()
+    private val args: ArtistNavigationPickerDialogArgs by navArgs()
+
+    override fun onBindingCreated(binding: DialogMusicPickerBinding, savedInstanceState: Bundle?) {
+        pickerModel.setArtistUids(args.artistUids)
+        super.onBindingCreated(binding, savedInstanceState)
+    }
+
+    override fun onItemClick(item: Item) {
+        super.onItemClick(item)
+        check(item is Music) { "Unexpected datatype: ${item::class.simpleName}" }
+        navModel.exploreNavigateTo(item)
+    }
+}

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

@@ -20,38 +20,19 @@ package org.oxycblt.auxio.music.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 org.oxycblt.auxio.R
 import org.oxycblt.auxio.databinding.DialogMusicPickerBinding
-import org.oxycblt.auxio.music.Album
-import org.oxycblt.auxio.music.Artist
-import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.playback.PlaybackViewModel
-import org.oxycblt.auxio.ui.NavigationViewModel
 import org.oxycblt.auxio.ui.fragment.ViewBindingDialogFragment
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.ui.recycler.ItemClickListener
-import org.oxycblt.auxio.util.androidActivityViewModels
 import org.oxycblt.auxio.util.collectImmediately
 
-/**
+abstract class ArtistPickerDialog :
- * A dialog that shows several artist options if the result of an artist-reliant operation is
- * ambiguous.
- * @author OxygenCobalt
- *
- * TODO: Clean up the picker flow to reduce the amount of duplication I had to do.
- */
-class ArtistPickerDialog :
     ViewBindingDialogFragment<DialogMusicPickerBinding>(), ItemClickListener {
-    private val pickerModel: PickerViewModel by viewModels()
+    protected val pickerModel: MusicPickerViewModel by viewModels()
-    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val artistAdapter = ArtistChoiceAdapter(this)
-    private val navModel: NavigationViewModel by activityViewModels()
-
-    private val args: ArtistPickerDialogArgs by navArgs()
-    private val adapter = ArtistChoiceAdapter(this)
 
     override fun onCreateBinding(inflater: LayoutInflater) =
         DialogMusicPickerBinding.inflate(inflater)
@@ -61,16 +42,12 @@ class ArtistPickerDialog :
     }
 
     override fun onBindingCreated(binding: DialogMusicPickerBinding, savedInstanceState: Bundle?) {
-        pickerModel.setSongUid(args.uid)
+        binding.pickerRecycler.adapter = artistAdapter
-
+        collectImmediately(pickerModel.currentArtists) { artists ->
-        binding.pickerRecycler.adapter = adapter
+            if (artists != null) {
-
+                artistAdapter.submitList(artists)
-        collectImmediately(pickerModel.currentItem) { item ->
+            } else {
-            when (item) {
+                findNavController().navigateUp()
-                is Song -> adapter.submitList(item.artists)
-                is Album -> adapter.submitList(item.artists)
-                null -> findNavController().navigateUp()
-                else -> error("Invalid datatype: ${item::class.java}")
             }
         }
     }
@@ -80,15 +57,6 @@ class ArtistPickerDialog :
     }
 
     override fun onItemClick(item: Item) {
-        check(item is Artist) { "Unexpected datatype: ${item::class.simpleName}" }
         findNavController().navigateUp()
-        when (args.pickerMode) {
-            PickerMode.SHOW -> navModel.exploreNavigateTo(item)
-            PickerMode.PLAY -> {
-                val currentItem = pickerModel.currentItem.value
-                check(currentItem is Song) { "PickerMode.PLAY is only allowed with Songs" }
-                playbackModel.playFromArtist(currentItem, item)
-            }
-        }
     }
 }

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

@@ -0,0 +1,49 @@
+/*
+ * 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.picker
+
+import android.os.Bundle
+import androidx.navigation.fragment.navArgs
+import org.oxycblt.auxio.databinding.DialogMusicPickerBinding
+import org.oxycblt.auxio.music.Artist
+import org.oxycblt.auxio.playback.PlaybackViewModel
+import org.oxycblt.auxio.ui.recycler.Item
+import org.oxycblt.auxio.util.androidActivityViewModels
+import org.oxycblt.auxio.util.unlikelyToBeNull
+
+/**
+ * The [ArtistPickerDialog] for ambiguous artist playback operations.
+ * @author OxygenCobalt
+ */
+class ArtistPlaybackPickerDialog : ArtistPickerDialog() {
+    private val playbackModel: PlaybackViewModel by androidActivityViewModels()
+    private val args: ArtistPlaybackPickerDialogArgs by navArgs()
+
+    override fun onBindingCreated(binding: DialogMusicPickerBinding, savedInstanceState: Bundle?) {
+        pickerModel.setSongUid(args.songUid)
+        super.onBindingCreated(binding, savedInstanceState)
+    }
+
+    override fun onItemClick(item: Item) {
+        super.onItemClick(item)
+        check(item is Artist) { "Unexpected datatype: ${item::class.simpleName}" }
+        pickerModel.currentSong.value?.let { song ->
+            playbackModel.playFromArtist(song, item)
+        }
+    }
+}

app/src/main/java/org/oxycblt/auxio/music/picker/MusicPickerViewModel.kt

@@ -0,0 +1,31 @@
+package org.oxycblt.auxio.music.picker
+
+import androidx.lifecycle.ViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import org.oxycblt.auxio.music.Artist
+import org.oxycblt.auxio.music.Music
+import org.oxycblt.auxio.music.MusicStore
+import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.util.unlikelyToBeNull
+
+class MusicPickerViewModel : ViewModel() {
+    private val musicStore = MusicStore.getInstance()
+
+    private val _currentSong = MutableStateFlow<Song?>(null)
+    val currentSong: StateFlow<Song?> get() = _currentSong
+
+    private val _currentArtists = MutableStateFlow<List<Artist>?>(null)
+    val currentArtists: StateFlow<List<Artist>?> get() = _currentArtists
+
+    fun setSongUid(uid: Music.UID) {
+        val library = unlikelyToBeNull(musicStore.library)
+        _currentSong.value = library.find(uid)
+        _currentArtists.value =  _currentSong.value?.artists
+    }
+
+    fun setArtistUids(uids: Array<Music.UID>) {
+        val library = unlikelyToBeNull(musicStore.library)
+        _currentArtists.value = uids.mapNotNull { library.find<Artist>(it) }.ifEmpty { null }
+    }
+}

app/src/main/java/org/oxycblt/auxio/music/picker/PickerMode.kt

@@ -1,24 +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.picker
-
-/** Represents the actions available to the picker UI. */
-enum class PickerMode {
-    PLAY,
-    SHOW
-}

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

@@ -1,60 +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.picker
-
-import androidx.lifecycle.ViewModel
-import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.StateFlow
-import org.oxycblt.auxio.music.Album
-import org.oxycblt.auxio.music.Music
-import org.oxycblt.auxio.music.MusicStore
-import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.util.unlikelyToBeNull
-
-/**
- * A small ViewModel holding and updating the current song being shown in the picker UI.
- * @author OxygenCobalt
- */
-class PickerViewModel : ViewModel(), MusicStore.Callback {
-    private val musicStore = MusicStore.getInstance()
-
-    private var _currentItem = MutableStateFlow<Music?>(null)
-    val currentItem: StateFlow<Music?> = _currentItem
-
-    fun setSongUid(uid: Music.UID) {
-        if (_currentItem.value?.uid == uid) return
-        val library = unlikelyToBeNull(musicStore.library)
-        val item = requireNotNull(library.find(uid)) { "Invalid song id provided" }
-        _currentItem.value = item
-    }
-
-    override fun onLibraryChanged(library: MusicStore.Library?) {
-        if (library != null) {
-            when (val item = currentItem.value) {
-                is Song -> {
-                    _currentItem.value = library.sanitize(item)
-                }
-                is Album -> {
-                    _currentItem.value = library.sanitize(item)
-                }
-                null -> {}
-                else -> error("Invalid datatype: ${item::class.java}")
-            }
-        }
-    }
-}

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

@@ -32,11 +32,10 @@ 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.picker.PickerMode
 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.fragment.MusicFragment
+import org.oxycblt.auxio.ui.fragment.MenuFragment
 import org.oxycblt.auxio.util.collectImmediately
 import org.oxycblt.auxio.util.showToast
 import org.oxycblt.auxio.util.systemBarInsetsCompat
@@ -49,7 +48,7 @@ import org.oxycblt.auxio.util.systemBarInsetsCompat
  * TODO: Make seek thumb grow when selected
  */
 class PlaybackPanelFragment :
-    MusicFragment<FragmentPlaybackPanelBinding>(),
+    MenuFragment<FragmentPlaybackPanelBinding>(),
     StyledSeekBar.Callback,
     Toolbar.OnMenuItemClickListener {
     // AudioEffect expects you to use startActivityForResult with the panel intent. Use
@@ -207,7 +206,7 @@ class PlaybackPanelFragment :
 
     private fun showCurrentArtist() {
         val song = playbackModel.song.value ?: return
-        doArtistDependentAction(song, PickerMode.SHOW)
+        navModel.exploreNavigateTo(song.artists)
     }
     private fun showCurrentAlbum() {
         val song = playbackModel.song.value ?: return

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

@@ -77,11 +77,18 @@ class PlaybackViewModel(application: Application) :
     val isShuffled: StateFlow<Boolean>
         get() = _isShuffled
 
+    /** The current ID of the app's audio session. */
     val currentAudioSessionId: Int?
         get() = playbackManager.currentAudioSessionId
 
     private var lastPositionJob: Job? = null
 
+    private val _artistPlaybackPickerSong = MutableStateFlow<Song?>(null)
+
+    /** Flag for resolving an ambiguous artist choice when playing from a song's artists. */
+    val artistPlaybackPickerSong: StateFlow<Song?>
+        get() = _artistPlaybackPickerSong
+
     init {
         playbackManager.addCallback(this)
     }
@@ -104,9 +111,22 @@ class PlaybackViewModel(application: Application) :
     }
 
     /** Play a song from it's artist. */
-    fun playFromArtist(song: Song, artist: Artist) {
+    fun playFromArtist(song: Song, artist: Artist? = null) {
-        check(artist.songs.contains(song)) { "Invalid input: Artist is not linked to song" }
+        if (artist != null) {
+            check(artist in song.artists) { "Artist not in song artists" }
             playbackManager.play(song, artist, settings)
+        } else {
+            if (song.artists.size == 1) {
+                playbackManager.play(song, song.artists[0], settings)
+            } else {
+                _artistPlaybackPickerSong.value = song
+            }
+        }
+    }
+
+    /** Complete the picker opening process when playing from an artist.  */
+    fun finishPlaybackArtistPicker() {
+        _artistPlaybackPickerSong.value = null
     }
 
     /** Play a song from the specific genre that contains the song. */

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

@@ -71,6 +71,8 @@ import org.oxycblt.auxio.widgets.WidgetProvider
  * not the source of truth for the state, but rather the means to control system-side playback. Both
  * of those tasks are what [PlaybackStateManager] is for.
  *
+ * TODO: Refactor lifecycle to run completely headless (i.e no activity needed)
+ *
  * TODO: Android Auto
  *
  * @author OxygenCobalt

app/src/main/java/org/oxycblt/auxio/search/SearchFragment.kt

@@ -38,9 +38,8 @@ 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.picker.PickerMode
 import org.oxycblt.auxio.settings.Settings
-import org.oxycblt.auxio.ui.fragment.MusicFragment
+import org.oxycblt.auxio.ui.fragment.MenuFragment
 import org.oxycblt.auxio.ui.recycler.Item
 import org.oxycblt.auxio.ui.recycler.MenuItemListener
 import org.oxycblt.auxio.util.androidViewModels
@@ -55,7 +54,7 @@ import org.oxycblt.auxio.util.logW
  * @author OxygenCobalt
  */
 class SearchFragment :
-    MusicFragment<FragmentSearchBinding>(), MenuItemListener, Toolbar.OnMenuItemClickListener {
+    MenuFragment<FragmentSearchBinding>(), MenuItemListener, Toolbar.OnMenuItemClickListener {
 
     // SearchViewModel is only scoped to this Fragment
     private val searchModel: SearchViewModel by androidViewModels()
@@ -149,7 +148,7 @@ class SearchFragment :
                 when (settings.libPlaybackMode) {
                     MusicMode.SONGS -> playbackModel.playFromAll(item)
                     MusicMode.ALBUMS -> playbackModel.playFromAlbum(item)
-                    MusicMode.ARTISTS -> doArtistDependentAction(item, PickerMode.PLAY)
+                    MusicMode.ARTISTS -> playbackModel.playFromArtist(item)
                     else -> error("Unexpected playback mode: ${settings.libPlaybackMode}")
                 }
             is MusicParent -> navModel.exploreNavigateTo(item)

app/src/main/java/org/oxycblt/auxio/ui/NavigationViewModel.kt

@@ -21,6 +21,7 @@ import androidx.lifecycle.ViewModel
 import androidx.navigation.NavDirections
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
+import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Music
 import org.oxycblt.auxio.util.logD
 
@@ -44,6 +45,15 @@ class NavigationViewModel : ViewModel() {
     val exploreNavigationItem: StateFlow<Music?>
         get() = _exploreNavigationItem
 
+    private val _exploreNavigationArtists = MutableStateFlow<List<Artist>?>(null)
+
+    /**
+     * Flag for navigation within the explore fragments. In this case, it involves an ambiguous list
+     * of artist choices.
+     */
+    val exploreNavigationArtists: StateFlow<List<Artist>?>
+        get() = _exploreNavigationArtists
+
     /** Notify MainFragment to navigate to the location outlined in [MainNavigationAction]. */
     fun mainNavigateTo(action: MainNavigationAction) {
         if (_mainNavigationAction.value != null) {
@@ -72,10 +82,26 @@ class NavigationViewModel : ViewModel() {
         _exploreNavigationItem.value = item
     }
 
+    /** Navigate to one item out of a list of items. */
+    fun exploreNavigateTo(items: List<Artist>) {
+        if (_exploreNavigationArtists.value != null) {
+            logD("Already navigating, not doing explore action")
+            return
+        }
+
+        if (items.size == 1) {
+            exploreNavigateTo(items[0])
+        } else {
+            logD("Navigating to a choice of ${items.map { it.rawName }}")
+            _exploreNavigationArtists.value = items
+        }
+    }
+
     /** Mark that the item navigation process is done. */
     fun finishExploreNavigation() {
         logD("Finishing explore navigation process")
         _exploreNavigationItem.value = null
+        _exploreNavigationArtists.value = null
     }
 }
 
@@ -91,5 +117,6 @@ sealed class MainNavigationAction {
     /** Collapse the playback panel. */
     object Collapse : MainNavigationAction()
 
+    /** Provide raw navigation directions. */
     data class Directions(val directions: NavDirections) : MainNavigationAction()
 }

app/src/main/java/org/oxycblt/auxio/ui/fastscroll/FastScrollRecyclerView.kt

@@ -67,6 +67,8 @@ import org.oxycblt.auxio.util.systemBarInsetsCompat
  *
  * TODO: Add vibration when popup changes
  *
+ * TODO: Improve this for variably sized items
+ *
  * @author Hai Zhang, OxygenCobalt
  */
 class FastScrollRecyclerView

app/src/main/java/org/oxycblt/auxio/ui/fragment/MenuFragment.kt

@@ -29,7 +29,6 @@ import org.oxycblt.auxio.music.Album
 import org.oxycblt.auxio.music.Artist
 import org.oxycblt.auxio.music.Genre
 import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.picker.PickerMode
 import org.oxycblt.auxio.playback.PlaybackViewModel
 import org.oxycblt.auxio.ui.MainNavigationAction
 import org.oxycblt.auxio.ui.NavigationViewModel
@@ -42,40 +41,12 @@ import org.oxycblt.auxio.util.showToast
  * preventing UI issues and memory leaks.
  * @author OxygenCobalt
  */
-abstract class MusicFragment<T : ViewBinding> : ViewBindingFragment<T>() {
+abstract class MenuFragment<T : ViewBinding> : ViewBindingFragment<T>() {
     private var currentMenu: PopupMenu? = null
 
     protected val playbackModel: PlaybackViewModel by androidActivityViewModels()
     protected val navModel: NavigationViewModel by activityViewModels()
 
-    /**
-     * Run the UI flow to perform a specific [PickerMode] action with a particular artist from
-     * [song].
-     */
-    fun doArtistDependentAction(song: Song, mode: PickerMode) {
-        if (song.artists.size == 1) {
-            when (mode) {
-                PickerMode.PLAY -> playbackModel.playFromArtist(song, song.artists[0])
-                PickerMode.SHOW -> navModel.exploreNavigateTo(song.artists[0])
-            }
-        } else {
-            navModel.mainNavigateTo(
-                MainNavigationAction.Directions(
-                    MainFragmentDirections.actionPickArtist(song.uid, mode)))
-        }
-    }
-
-    /** Run the UI flow to navigate to a particular artist from [album]. */
-    fun navigateToArtist(album: Album) {
-        if (album.artists.size == 1) {
-            navModel.exploreNavigateTo(album.artists[0])
-        } else {
-            navModel.mainNavigateTo(
-                MainNavigationAction.Directions(
-                    MainFragmentDirections.actionPickArtist(album.uid, PickerMode.SHOW)))
-        }
-    }
-
     /**
      * Opens the given menu in context of [song]. Assumes that the menu is only composed of common
      * [Song] options.
@@ -94,7 +65,7 @@ abstract class MusicFragment<T : ViewBinding> : ViewBindingFragment<T>() {
                     requireContext().showToast(R.string.lng_queue_added)
                 }
                 R.id.action_go_artist -> {
-                    doArtistDependentAction(song, PickerMode.SHOW)
+                    navModel.exploreNavigateTo(song.artists)
                 }
                 R.id.action_go_album -> {
                     navModel.exploreNavigateTo(song.album)
@@ -137,7 +108,7 @@ abstract class MusicFragment<T : ViewBinding> : ViewBindingFragment<T>() {
                     requireContext().showToast(R.string.lng_queue_added)
                 }
                 R.id.action_go_artist -> {
-                    navigateToArtist(album)
+                    navModel.exploreNavigateTo(album.artists)
                 }
                 else -> {
                     error("Unexpected menu item selected")

app/src/main/java/org/oxycblt/auxio/widgets/WidgetComponent.kt

@@ -65,8 +65,6 @@ class WidgetComponent(private val context: Context) :
         // 1. We can't use the typical primitives like ViewModels
         // 2. The component range is far smaller, so we have to do some odd hacks to get
         // the same UX.
-        // 3. RemoteView memory is limited, so we want to batch updates as much as physically
-        // possible.
         val song = playbackManager.song
         if (song == null) {
             logD("No song, resetting widget")

app/src/main/res/navigation/nav_main.xml

@@ -18,22 +18,31 @@
             android:id="@+id/action_show_details"
             app:destination="@id/song_detail_dialog" />
         <action
-            android:id="@+id/action_pick_artist"
+            android:id="@+id/action_pick_playback_artist"
-            app:destination="@id/artist_picker_dialog" />
+            app:destination="@id/artist_playback_picker_dialog" />
+        <action
+            android:id="@+id/action_pick_navigation_artist"
+            app:destination="@id/artist_navigation_picker_dialog" />
     </fragment>
 
-
     <dialog
-        android:id="@+id/artist_picker_dialog"
+        android:id="@+id/artist_playback_picker_dialog"
-        android:name="org.oxycblt.auxio.music.picker.ArtistPickerDialog"
+        android:name="org.oxycblt.auxio.music.picker.ArtistPlaybackPickerDialog"
-        android:label="artist_picker_dialog"
+        android:label="artist_playback_picker_dialog"
         tools:layout="@layout/dialog_music_picker">
         <argument
-            android:name="uid"
+            android:name="songUid"
             app:argType="org.oxycblt.auxio.music.Music$UID" />
+    </dialog>
+
+    <dialog
+        android:id="@+id/artist_navigation_picker_dialog"
+        android:name="org.oxycblt.auxio.music.picker.ArtistNavigationPickerDialog"
+        android:label="artist_navigation_picker_dialog"
+        tools:layout="@layout/dialog_music_picker">
         <argument
-            android:name="pickerMode"
+            android:name="artistUids"
-            app:argType="org.oxycblt.auxio.music.picker.PickerMode" />
+            app:argType="org.oxycblt.auxio.music.Music$UID[]" />
     </dialog>
 
     <dialog

prebuild.py

@@ -29,6 +29,7 @@ OK="\033[1;92m"
 NC="\033[0m"
 
 # We do some shell scripting later on, so we can't support windows.
+# TODO: Support windows
 system = platform.system()
 if system not in ["Linux", "Darwin"]:
     print("fatal: unsupported platform " + system)