music: improve field management

Cache some music fields and make other fields more coherent given
recent changes.

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

@@ -241,10 +241,6 @@ class DetailViewModel(application: Application) :
 
         val byReleaseGroup =
             albums.groupBy {
-                if (it.releaseType == null) {
-                    return@groupBy R.string.lbl_albums
-                }
-
                 when (it.releaseType.refinement) {
                     ReleaseType.Refinement.LIVE -> R.string.lbl_live_group
                     ReleaseType.Refinement.REMIX -> R.string.lbl_remix_group

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

@@ -115,8 +115,7 @@ private class AlbumDetailViewHolder private constructor(private val binding: Ite
 
     override fun bind(item: Album, listener: AlbumDetailAdapter.Listener) {
         binding.detailCover.bind(item)
-        binding.detailType.text =
-            binding.context.getString(item.releaseType?.stringRes ?: R.string.lbl_album)
+        binding.detailType.text = binding.context.getString(item.releaseType.stringRes)
 
         binding.detailName.text = item.resolveName(binding.context)
 

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

@@ -123,8 +123,7 @@ data class Song(
     override fun resolveName(context: Context) = rawName
 
     /** The duration of this song, in seconds (rounded down) */
-    val durationSecs: Long
-        get() = durationMs / 1000
+    val durationSecs = durationMs / 1000
 
     private var _album: Album? = null
     /** The album of this song. */
@@ -202,11 +201,8 @@ data class Album(
     override val rawSortName: String?,
     /** The date this album was released. */
     val date: Date?,
-    /**
-     * The type of release this album represents. Null if release types were not applicable to this
-     * library.
-     */
-    val releaseType: ReleaseType?,
+    /** The type of release this album has. */
+    val releaseType: ReleaseType,
     /** The URI for the cover image corresponding to this album. */
     val coverUri: Uri,
     /** The songs of this album. */
@@ -237,6 +233,9 @@ data class Album(
     val artist: Artist
         get() = unlikelyToBeNull(_artist)
 
+    /** The earliest date a song in this album was added. */
+    val dateAdded = songs.minOf { it.dateAdded }
+
     /** Internal field. Do not use. */
     val _artistGroupingId: Long
         get() = _artistGroupingName.toMusicId()
@@ -437,6 +436,15 @@ class Date private constructor(private val tokens: List<Int>) : Comparable<Date>
     }
 }
 
+/**
+ * Represents the type of release a particular album is.
+ *
+ * This can be used to differentiate between album sub-types like Singles, EPs, Compilations, and
+ * others. Internally, it operates on a reduced version of the MusicBrainz release type
+ * specification. It can be extended if there is demand.
+ *
+ * @author OxygenCobalt
+ */
 sealed class ReleaseType {
     abstract val refinement: Refinement?
     abstract val stringRes: Int
@@ -495,6 +503,11 @@ sealed class ReleaseType {
             get() = R.string.lbl_mixtape
     }
 
+    /**
+     * Roughly analogous to the MusicBrainz "live" and "remix" secondary types. Unlike the main
+     * types, these only modify an existing, primary type. They are not implemented for secondary
+     * types, however they may be expanded to compilations in the future.
+     */
     enum class Refinement {
         LIVE,
         REMIX

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

@@ -296,13 +296,6 @@ class Indexer {
         val albums = mutableListOf<Album>()
         val songsByAlbum = songs.groupBy { it._albumGroupingId }
 
-        // If album types aren't used by the music library (Represented by all songs having
-        // no album type), there is no point in displaying them.
-        val enableAlbumTypes = songs.any { it._albumReleaseType != null }
-        if (!enableAlbumTypes) {
-            logD("No distinct album types detected, ignoring them")
-        }
-
         for (entry in songsByAlbum) {
             val albumSongs = entry.value
 
@@ -317,10 +310,7 @@ class Indexer {
                     rawName = templateSong._albumName,
                     rawSortName = templateSong._albumSortName,
                     date = templateSong._date,
-                    releaseType =
-                        if (enableAlbumTypes)
-                            (templateSong._albumReleaseType ?: ReleaseType.Album(null))
-                        else null,
+                    releaseType = templateSong._albumReleaseType ?: ReleaseType.Album(null),
                     coverUri = templateSong._albumCoverUri,
                     songs = entry.value,
                     _artistGroupingName = templateSong._artistGroupingName,

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

@@ -350,7 +350,7 @@ data class Sort(val mode: Mode, val isAscending: Boolean) {
         }
 
         private class BasicComparator<T : Music> private constructor() : Comparator<T> {
-            // TODO: Use Collator for sorting?
+            // TODO: Perhaps I should leverage collator?
 
             override fun compare(a: T, b: T): Int {
                 val aSortName = a.sortName