detail: split off detail list into generator

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

@@ -0,0 +1,216 @@
+package org.oxycblt.auxio.detail
+
+import android.content.Context
+import androidx.annotation.StringRes
+import org.oxycblt.auxio.R
+import org.oxycblt.auxio.detail.list.DiscHeader
+import org.oxycblt.auxio.list.ListSettings
+import org.oxycblt.auxio.list.sort.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.MusicParent
+import org.oxycblt.auxio.music.MusicRepository
+import org.oxycblt.auxio.music.MusicType
+import org.oxycblt.auxio.music.Playlist
+import org.oxycblt.auxio.music.Song
+import org.oxycblt.auxio.music.info.Disc
+import org.oxycblt.auxio.music.info.ReleaseType
+import org.oxycblt.auxio.util.logD
+import java.util.SortedMap
+import javax.inject.Inject
+
+interface DetailGenerator {
+    fun any(uid: Music.UID): Detail<out MusicParent>?
+    fun album(uid: Music.UID): Detail<Album>?
+    fun artist(uid: Music.UID): Detail<Artist>?
+    fun genre(uid: Music.UID): Detail<Genre>?
+    fun playlist(uid: Music.UID): Detail<Playlist>?
+    fun release()
+
+    interface Factory {
+        fun create(invalidator: Invalidator): DetailGenerator
+    }
+
+    interface Invalidator {
+        fun invalidate(type: MusicType, replace: Int?)
+    }
+}
+
+class DetailGeneratorFactoryImpl @Inject constructor(
+    private val listSettings: ListSettings,
+    private val musicRepository: MusicRepository
+) : DetailGenerator.Factory {
+    override fun create(invalidator: DetailGenerator.Invalidator): DetailGenerator =
+        DetailGeneratorImpl(invalidator, listSettings, musicRepository)
+}
+
+private class DetailGeneratorImpl(
+    private val invalidator: DetailGenerator.Invalidator,
+    private val listSettings: ListSettings,
+    private val musicRepository: MusicRepository
+) : DetailGenerator, MusicRepository.UpdateListener, ListSettings.Listener {
+    init {
+        listSettings.registerListener(this)
+        musicRepository.addUpdateListener(this)
+    }
+
+    override fun onAlbumSongSortChanged() {
+        super.onAlbumSongSortChanged()
+        invalidator.invalidate(MusicType.ALBUMS, -1)
+    }
+
+    override fun onArtistSongSortChanged() {
+        super.onArtistSongSortChanged()
+        invalidator.invalidate(MusicType.ARTISTS, -1)
+    }
+
+    override fun onGenreSongSortChanged() {
+        super.onGenreSongSortChanged()
+        invalidator.invalidate(MusicType.GENRES, -1)
+    }
+
+    override fun onMusicChanges(changes: MusicRepository.Changes) {
+        if (changes.deviceLibrary) {
+            invalidator.invalidate(MusicType.ALBUMS, null)
+            invalidator.invalidate(MusicType.ARTISTS, null)
+            invalidator.invalidate(MusicType.GENRES, null)
+        }
+        if (changes.userLibrary) {
+            invalidator.invalidate(MusicType.PLAYLISTS, null)
+        }
+    }
+
+    override fun release() {
+        listSettings.unregisterListener(this)
+        musicRepository.removeUpdateListener(this)
+    }
+
+    override fun any(uid: Music.UID): Detail<out MusicParent>? {
+        val music = musicRepository.find(uid) ?: return null
+        return when (music) {
+            is Album -> album(uid)
+            is Artist -> artist(uid)
+            is Genre -> genre(uid)
+            is Playlist -> playlist(uid)
+            else -> null
+        }
+    }
+
+    override fun album(uid: Music.UID): Detail<Album>? {
+        val album = musicRepository.deviceLibrary?.findAlbum(uid) ?: return null
+        val songs = listSettings.albumSongSort.songs(album.songs)
+        val discs = songs.groupBy { it.disc }
+        val section = if (discs.size > 1 || discs.keys.first() != null) {
+             DetailSection.Discs(discs)
+        } else {
+            DetailSection.Songs(songs)
+        }
+        return Detail(album, listOf(section))
+    }
+
+    override fun artist(uid: Music.UID): Detail<Artist>? {
+        val artist = musicRepository.deviceLibrary?.findArtist(uid) ?: return null
+        val grouping =
+            artist.explicitAlbums.groupByTo(sortedMapOf()) {
+                // Remap the complicated ReleaseType data structure into detail sections
+                when (it.releaseType.refinement) {
+                    ReleaseType.Refinement.LIVE -> DetailSection.Albums.Category.LIVE
+                    ReleaseType.Refinement.REMIX -> DetailSection.Albums.Category.REMIXES
+                    null ->
+                        when (it.releaseType) {
+                            is ReleaseType.Album -> DetailSection.Albums.Category.ALBUMS
+                            is ReleaseType.EP -> DetailSection.Albums.Category.EPS
+                            is ReleaseType.Single -> DetailSection.Albums.Category.SINGLES
+                            is ReleaseType.Compilation -> DetailSection.Albums.Category.COMPILATIONS
+                            is ReleaseType.Soundtrack -> DetailSection.Albums.Category.SOUNDTRACKS
+                            is ReleaseType.Mix -> DetailSection.Albums.Category.DJ_MIXES
+                            is ReleaseType.Mixtape -> DetailSection.Albums.Category.MIXTAPES
+                            is ReleaseType.Demo -> DetailSection.Albums.Category.DEMOS
+                        }
+                }
+            }
+
+        if (artist.implicitAlbums.isNotEmpty()) {
+            // groupByTo normally returns a mapping to a MutableList mapping. Since MutableList
+            // inherits list, we can cast upwards and save a copy by directly inserting the
+            // implicit album list into the mapping.
+            logD("Implicit albums present, adding to list")
+            @Suppress("UNCHECKED_CAST")
+            (grouping as MutableMap<DetailSection.Albums.Category, Collection<Album>>)[DetailSection.Albums.Category.APPEARANCES] =
+                artist.implicitAlbums
+        }
+
+        val sections = grouping.mapTo(mutableListOf<DetailSection>()) { (category, albums) ->
+            DetailSection.Albums(category, ARTIST_ALBUM_SORT.albums(albums))
+        }
+        val songs = DetailSection.Songs(listSettings.artistSongSort.songs(artist.songs))
+        sections.add(songs)
+        return Detail(artist, sections)
+    }
+
+    override fun genre(uid: Music.UID): Detail<Genre>? {
+        val genre = musicRepository.deviceLibrary?.findGenre(uid) ?: return null
+        val artists = DetailSection.Artists(GENRE_ARTIST_SORT.artists(genre.artists))
+        val songs = DetailSection.Songs(listSettings.genreSongSort.songs(genre.songs))
+        return Detail(genre, listOf(artists, songs))
+    }
+
+    override fun playlist(uid: Music.UID): Detail<Playlist>? {
+        val playlist = musicRepository.userLibrary?.findPlaylist(uid) ?: return null
+        val songs = DetailSection.Songs(playlist.songs)
+        return Detail(playlist, listOf(songs))
+    }
+
+    private companion object {
+        val ARTIST_ALBUM_SORT = Sort(Sort.Mode.ByDate, Sort.Direction.DESCENDING)
+        val GENRE_ARTIST_SORT = Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+    }
+}
+
+data class Detail<P : MusicParent>(val parent: P, val sections: List<DetailSection>)
+
+sealed interface DetailSection {
+    val order: Int
+    val stringRes: Int
+
+    abstract class PlainSection<T : Music> : DetailSection {
+        abstract val items: List<T>
+    }
+
+    data class Artists(override val items: List<Artist>) : PlainSection<Artist>() {
+        override val order = 0
+        override val stringRes = R.string.lbl_songs
+    }
+
+    data class Albums(val category: Category, override val items: List<Album>) : PlainSection<Album>() {
+        override val order = 1 + category.ordinal
+        override val stringRes = category.stringRes
+
+        enum class Category(@StringRes val stringRes: Int) {
+            ALBUMS(R.string.lbl_albums),
+            EPS(R.string.lbl_eps),
+            SINGLES(R.string.lbl_singles),
+            COMPILATIONS(R.string.lbl_compilations),
+            SOUNDTRACKS(R.string.lbl_soundtracks),
+            DJ_MIXES(R.string.lbl_mixes),
+            MIXTAPES(R.string.lbl_mixtapes),
+            DEMOS(R.string.lbl_demos),
+            APPEARANCES(R.string.lbl_appears_on),
+            LIVE(R.string.lbl_live_group),
+            REMIXES(R.string.lbl_remix_group)
+        }
+    }
+
+
+    data class Songs(override val items: List<Song>) : PlainSection<Song>() {
+        override val order = 12
+        override val stringRes = R.string.lbl_songs
+    }
+
+    data class Discs(val discs: Map<Disc?, List<Song>>) : DetailSection {
+        override val order = 13
+        override val stringRes = R.string.lbl_songs
+    }
+}

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

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2024 Auxio Project
+ * HomeModule.kt is part of Auxio.
+ *
+ * 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 dagger.Binds
+import dagger.Module
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+
+@Module
+@InstallIn(SingletonComponent::class)
+interface DetailModule {
+    @Binds fun detailGeneratorFactory(factory: DetailGeneratorFactoryImpl): DetailGenerator.Factory
+}

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

@@ -18,7 +18,6 @@
  
 package org.oxycblt.auxio.detail
 
-import androidx.annotation.StringRes
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
@@ -43,10 +42,11 @@ 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.MusicRepository
+import org.oxycblt.auxio.music.MusicType
 import org.oxycblt.auxio.music.Playlist
 import org.oxycblt.auxio.music.Song
-import org.oxycblt.auxio.music.info.ReleaseType
 import org.oxycblt.auxio.music.metadata.AudioProperties
 import org.oxycblt.auxio.playback.PlaySong
 import org.oxycblt.auxio.playback.PlaybackSettings
@@ -69,8 +69,12 @@ constructor(
     private val listSettings: ListSettings,
     private val musicRepository: MusicRepository,
     private val audioPropertiesFactory: AudioProperties.Factory,
-    private val playbackSettings: PlaybackSettings
-) : ViewModel(), MusicRepository.UpdateListener {
+    private val playbackSettings: PlaybackSettings,
+    detailGeneratorFactory: DetailGenerator.Factory
+) : ViewModel(), DetailGenerator.Invalidator {
+    private val detailGenerator = detailGeneratorFactory.create(this)
+
+
     private val _toShow = MutableEvent<Show>()
     /**
      * A [Show] command that is awaiting a view capable of responding to it. Null if none currently.
@@ -133,13 +137,8 @@ constructor(
         get() = _artistSongInstructions
 
     /** The current [Sort] used for [Song]s in [artistSongList]. */
-    var artistSongSort: Sort
+    val artistSongSort: Sort
         get() = listSettings.artistSongSort
-        set(value) {
-            listSettings.artistSongSort = value
-            // Refresh the artist list to reflect the new sort.
-            currentArtist.value?.let { refreshArtistList(it, true) }
-        }
 
     /** The [PlaySong] instructions to use when playing a [Song] from [Artist] details. */
     val playInArtistWith
@@ -162,13 +161,8 @@ constructor(
         get() = _genreSongInstructions
 
     /** The current [Sort] used for [Song]s in [genreSongList]. */
-    var genreSongSort: Sort
+    val genreSongSort: Sort
         get() = listSettings.genreSongSort
-        set(value) {
-            listSettings.genreSongSort = value
-            // Refresh the genre list to reflect the new sort.
-            currentGenre.value?.let { refreshGenreList(it, true) }
-        }
 
     /** The [PlaySong] instructions to use when playing a [Song] from [Genre] details. */
     val playInGenreWith
@@ -204,54 +198,32 @@ constructor(
             playbackSettings.inParentPlaybackMode
                 ?: PlaySong.FromPlaylist(unlikelyToBeNull(currentPlaylist.value))
 
-    init {
-        musicRepository.addUpdateListener(this)
-    }
-
     override fun onCleared() {
-        musicRepository.removeUpdateListener(this)
+        detailGenerator.release()
     }
 
-    override fun onMusicChanges(changes: MusicRepository.Changes) {
-        // If we are showing any item right now, we will need to refresh it (and any information
-        // related to it) with the new library in order to prevent stale items from showing up
-        // in the UI.
-        val deviceLibrary = musicRepository.deviceLibrary
-        if (changes.deviceLibrary && deviceLibrary != null) {
-            val song = currentSong.value
-            if (song != null) {
-                _currentSong.value = deviceLibrary.findSong(song.uid)?.also(::refreshAudioInfo)
-                logD("Updated song to ${currentSong.value}")
+    override fun invalidate(type: MusicType, replace: Int?) {
+        when (type) {
+            MusicType.ALBUMS -> {
+                val album = detailGenerator.album(currentAlbum.value?.uid ?: return)
+                refreshDetail(album, _currentAlbum, _albumSongList, _albumSongInstructions, replace)
             }
 
-            val album = currentAlbum.value
-            if (album != null) {
-                _currentAlbum.value = deviceLibrary.findAlbum(album.uid)?.also(::refreshAlbumList)
-                logD("Updated album to ${currentAlbum.value}")
+            MusicType.ARTISTS -> {
+                val artist = detailGenerator.artist(currentArtist.value?.uid ?: return)
+                refreshDetail(artist, _currentArtist, _artistSongList, _artistSongInstructions, replace)
             }
 
-            val artist = currentArtist.value
-            if (artist != null) {
-                _currentArtist.value =
-                    deviceLibrary.findArtist(artist.uid)?.also(::refreshArtistList)
-                logD("Updated artist to ${currentArtist.value}")
+            MusicType.GENRES -> {
+                val genre = detailGenerator.genre(currentGenre.value?.uid ?: return)
+                refreshDetail(genre, _currentGenre, _genreSongList, _genreSongInstructions, replace)
             }
 
-            val genre = currentGenre.value
-            if (genre != null) {
-                _currentGenre.value = deviceLibrary.findGenre(genre.uid)?.also(::refreshGenreList)
-                logD("Updated genre to ${currentGenre.value}")
+            MusicType.PLAYLISTS -> {
+                refreshPlaylist(currentPlaylist.value?.uid ?: return)
             }
-        }
 
-        val userLibrary = musicRepository.userLibrary
-        if (changes.userLibrary && userLibrary != null) {
-            val playlist = currentPlaylist.value
-            if (playlist != null) {
-                _currentPlaylist.value =
-                    userLibrary.findPlaylist(playlist.uid)?.also(::refreshPlaylistList)
-                logD("Updated playlist to ${currentPlaylist.value}")
-            }
+            else -> error("Unexpected music type $type")
         }
     }
 
@@ -356,8 +328,11 @@ constructor(
      */
     fun setAlbum(uid: Music.UID) {
         logD("Opening album $uid")
-        _currentAlbum.value =
-            musicRepository.deviceLibrary?.findAlbum(uid)?.also(::refreshAlbumList)
+        if (uid === _currentAlbum.value?.uid) {
+            return
+        }
+        val album = detailGenerator.album(uid)
+        refreshDetail(album, _currentAlbum, _albumSongList, _albumSongInstructions, null)
         if (_currentAlbum.value == null) {
             logW("Given album UID was invalid")
         }
@@ -370,7 +345,6 @@ constructor(
      */
     fun applyAlbumSongSort(sort: Sort) {
         listSettings.albumSongSort = sort
-        _currentAlbum.value?.let { refreshAlbumList(it, true) }
     }
 
     /**
@@ -381,11 +355,11 @@ constructor(
      */
     fun setArtist(uid: Music.UID) {
         logD("Opening artist $uid")
-        _currentArtist.value =
-            musicRepository.deviceLibrary?.findArtist(uid)?.also(::refreshArtistList)
-        if (_currentArtist.value == null) {
-            logW("Given artist UID was invalid")
+        if (uid === _currentArtist.value?.uid) {
+            return
         }
+        val artist = detailGenerator.artist(uid)
+        refreshDetail(artist, _currentArtist, _artistSongList, _artistSongInstructions, null)
     }
 
     /**
@@ -395,7 +369,6 @@ constructor(
      */
     fun applyArtistSongSort(sort: Sort) {
         listSettings.artistSongSort = sort
-        _currentArtist.value?.let { refreshArtistList(it, true) }
     }
 
     /**
@@ -406,11 +379,11 @@ constructor(
      */
     fun setGenre(uid: Music.UID) {
         logD("Opening genre $uid")
-        _currentGenre.value =
-            musicRepository.deviceLibrary?.findGenre(uid)?.also(::refreshGenreList)
-        if (_currentGenre.value == null) {
-            logW("Given genre UID was invalid")
+        if (uid === _currentGenre.value?.uid) {
+            return
         }
+        val genre = detailGenerator.genre(uid)
+        refreshDetail(genre, _currentGenre, _genreSongList, _genreSongInstructions, null)
     }
 
     /**
@@ -420,7 +393,6 @@ constructor(
      */
     fun applyGenreSongSort(sort: Sort) {
         listSettings.genreSongSort = sort
-        _currentGenre.value?.let { refreshGenreList(it, true) }
     }
 
     /**
@@ -431,11 +403,10 @@ constructor(
      */
     fun setPlaylist(uid: Music.UID) {
         logD("Opening playlist $uid")
-        _currentPlaylist.value =
-            musicRepository.userLibrary?.findPlaylist(uid)?.also(::refreshPlaylistList)
-        if (_currentPlaylist.value == null) {
-            logW("Given playlist UID was invalid")
+        if (uid === _currentPlaylist.value?.uid) {
+            return
         }
+        refreshPlaylist(uid)
     }
 
     /** Start a playlist editing session. Does nothing if a playlist is not being shown. */
@@ -443,7 +414,7 @@ constructor(
         val playlist = _currentPlaylist.value ?: return
         logD("Starting playlist edit")
         _editedPlaylist.value = playlist.songs
-        refreshPlaylistList(playlist)
+        refreshPlaylist(playlist.uid)
     }
 
     /**
@@ -474,9 +445,8 @@ constructor(
             // Nothing to do.
             return false
         }
-        logD("Discarding playlist edits")
         _editedPlaylist.value = null
-        refreshPlaylistList(playlist)
+        refreshPlaylist(playlist.uid)
         return true
     }
 
@@ -488,7 +458,7 @@ constructor(
     fun applyPlaylistSongSort(sort: Sort) {
         val playlist = _currentPlaylist.value ?: return
         _editedPlaylist.value = sort.songs(_editedPlaylist.value ?: return)
-        refreshPlaylistList(playlist, UpdateInstructions.Replace(2))
+        refreshPlaylist(playlist.uid, UpdateInstructions.Replace(2))
     }
 
     /**
@@ -509,7 +479,7 @@ constructor(
         logD("Moving playlist song from $realFrom [$from] to $realTo [$to]")
         editedPlaylist.add(realFrom, editedPlaylist.removeAt(realTo))
         _editedPlaylist.value = editedPlaylist
-        refreshPlaylistList(playlist, UpdateInstructions.Move(from, to))
+        refreshPlaylist(playlist.uid, UpdateInstructions.Move(from, to))
         return true
     }
 
@@ -528,8 +498,8 @@ constructor(
         logD("Removing playlist song at $realAt [$at]")
         editedPlaylist.removeAt(realAt)
         _editedPlaylist.value = editedPlaylist
-        refreshPlaylistList(
-            playlist,
+        refreshPlaylist(
+            playlist.uid,
             if (editedPlaylist.isNotEmpty()) {
                 UpdateInstructions.Remove(at, 1)
             } else {
@@ -552,173 +522,69 @@ constructor(
             }
     }
 
-    private fun refreshAlbumList(album: Album, replace: Boolean = false) {
-        logD("Refreshing album list")
-        val list = mutableListOf<Item>()
-        val header = SortHeader(R.string.lbl_songs)
-        list.add(Divider(header))
-        list.add(header)
-        val instructions =
-            if (replace) {
-                // Intentional so that the header item isn't replaced with the songs
-                UpdateInstructions.Replace(list.size)
-            } else {
-                UpdateInstructions.Diff
-            }
 
-        // To create a good user experience regarding disc numbers, we group the album's
-        // songs up by disc and then delimit the groups by a disc header.
-        val songs = albumSongSort.songs(album.songs)
-        val byDisc = songs.groupBy { it.disc }
-        if (byDisc.size > 1) {
-            logD("Album has more than one disc, interspersing headers")
-            for (entry in byDisc.entries) {
-                list.add(DiscHeader(entry.key))
-                list.addAll(entry.value)
-            }
-        } else {
-            // Album only has one disc, don't add any redundant headers
-            list.addAll(songs)
+    private fun <T : MusicParent> refreshDetail(
+        detail: Detail<T>?,
+        parent: MutableStateFlow<T?>,
+        list: MutableStateFlow<List<Item>>,
+        instructions: MutableEvent<UpdateInstructions>,
+        replace: Int?
+    ) {
+        if (detail == null) {
+            parent.value = null
+            return
         }
+        val newList = mutableListOf<Item>()
+        var newInstructions: UpdateInstructions = UpdateInstructions.Diff
+        for ((i, section) in detail.sections.withIndex()) {
+            val items = when (section) {
+                is DetailSection.PlainSection<*> -> {
+                    val header = if (section is DetailSection.Songs)
+                        SortHeader(section.stringRes) else BasicHeader(section.stringRes)
+                    newList.add(Divider(header))
+                    newList.add(header)
+                    section.items
+                }
 
-        logD("Update album list to ${list.size} items with $instructions")
-        _albumSongInstructions.put(instructions)
-        _albumSongList.value = list
-    }
-
-    private fun refreshArtistList(artist: Artist, replace: Boolean = false) {
-        logD("Refreshing artist list")
-        val list = mutableListOf<Item>()
-
-        val grouping =
-            artist.explicitAlbums.groupByTo(sortedMapOf()) {
-                // Remap the complicated ReleaseType data structure into an easier
-                // "AlbumGrouping" enum that will automatically group and sort
-                // the artist's albums.
-                when (it.releaseType.refinement) {
-                    ReleaseType.Refinement.LIVE -> AlbumGrouping.LIVE
-                    ReleaseType.Refinement.REMIX -> AlbumGrouping.REMIXES
-                    null ->
-                        when (it.releaseType) {
-                            is ReleaseType.Album -> AlbumGrouping.ALBUMS
-                            is ReleaseType.EP -> AlbumGrouping.EPS
-                            is ReleaseType.Single -> AlbumGrouping.SINGLES
-                            is ReleaseType.Compilation -> AlbumGrouping.COMPILATIONS
-                            is ReleaseType.Soundtrack -> AlbumGrouping.SOUNDTRACKS
-                            is ReleaseType.Mix -> AlbumGrouping.DJMIXES
-                            is ReleaseType.Mixtape -> AlbumGrouping.MIXTAPES
-                            is ReleaseType.Demo -> AlbumGrouping.DEMOS
-                        }
+                is DetailSection.Discs -> {
+                    val header = BasicHeader(section.stringRes)
+                    newList.add(Divider(header))
+                    newList.add(header)
+                    section.discs.flatMap {
+                        listOf(DiscHeader(it.key)) + it.value
+                    }
                 }
             }
-
-        if (artist.implicitAlbums.isNotEmpty()) {
-            // groupByTo normally returns a mapping to a MutableList mapping. Since MutableList
-            // inherits list, we can cast upwards and save a copy by directly inserting the
-            // implicit album list into the mapping.
-            logD("Implicit albums present, adding to list")
-            @Suppress("UNCHECKED_CAST")
-            (grouping as MutableMap<AlbumGrouping, Collection<Album>>)[AlbumGrouping.APPEARANCES] =
-                artist.implicitAlbums
-        }
-
-        logD("Release groups for this artist: ${grouping.keys}")
-
-        for (entry in grouping.entries) {
-            val header = BasicHeader(entry.key.headerTitleRes)
-            list.add(Divider(header))
-            list.add(header)
-            list.addAll(ARTIST_ALBUM_SORT.albums(entry.value))
-        }
-
-        // Artists may not be linked to any songs, only include a header entry if we have any.
-        var instructions: UpdateInstructions = UpdateInstructions.Diff
-        if (artist.songs.isNotEmpty()) {
-            logD("Songs present in this artist, adding header")
-            val header = SortHeader(R.string.lbl_songs)
-            list.add(Divider(header))
-            list.add(header)
-            if (replace) {
+            // Currently only the final section (songs, which can be sorted) are invalidatable
+            // and thus need to be replaced.
+            if (replace == -1 && i == detail.sections.lastIndex) {
                 // Intentional so that the header item isn't replaced with the songs
-                instructions = UpdateInstructions.Replace(list.size)
+                newInstructions = UpdateInstructions.Replace(newList.size)
             }
-            list.addAll(artistSongSort.songs(artist.songs))
+            newList.addAll(items)
         }
-
-        logD("Updating artist list to ${list.size} items with $instructions")
-        _artistSongInstructions.put(instructions)
-        _artistSongList.value = list.toList()
+        parent.value = detail.parent
+        list.value = newList
+        instructions.put(newInstructions)
     }
 
-    private fun refreshGenreList(genre: Genre, replace: Boolean = false) {
-        logD("Refreshing genre list")
-        val list = mutableListOf<Item>()
-        // Genre is guaranteed to always have artists and songs.
-        val artistHeader = BasicHeader(R.string.lbl_artists)
-        list.add(Divider(artistHeader))
-        list.add(artistHeader)
-        list.addAll(GENRE_ARTIST_SORT.artists(genre.artists))
-
-        val songHeader = SortHeader(R.string.lbl_songs)
-        list.add(Divider(songHeader))
-        list.add(songHeader)
-        val instructions =
-            if (replace) {
-                // Intentional so that the header item isn't replaced alongside the songs
-                UpdateInstructions.Replace(list.size)
-            } else {
-                UpdateInstructions.Diff
-            }
-        list.addAll(genreSongSort.songs(genre.songs))
-
-        logD("Updating genre list to ${list.size} items with $instructions")
-        _genreSongInstructions.put(instructions)
-        _genreSongList.value = list
-    }
-
-    private fun refreshPlaylistList(
-        playlist: Playlist,
-        instructions: UpdateInstructions = UpdateInstructions.Diff
-    ) {
+    private fun refreshPlaylist(uid: Music.UID, instructions: UpdateInstructions = UpdateInstructions.Diff) {
         logD("Refreshing playlist list")
+        val edited = editedPlaylist.value
+        if (edited == null) {
+            val playlist = detailGenerator.playlist(uid)
+            refreshDetail(playlist, _currentPlaylist, _playlistSongList, _playlistSongInstructions, null)
+            return
+        }
         val list = mutableListOf<Item>()
-
-        val songs = editedPlaylist.value ?: playlist.songs
-        if (songs.isNotEmpty()) {
+        if (edited.isNotEmpty()) {
             val header = EditHeader(R.string.lbl_songs)
             list.add(Divider(header))
             list.add(header)
-            list.addAll(songs)
+            list.addAll(edited)
         }
-
-        logD("Updating playlist list to ${list.size} items with $instructions")
-        _playlistSongInstructions.put(instructions)
         _playlistSongList.value = list
-    }
-
-    /**
-     * A simpler mapping of [ReleaseType] used for grouping and sorting songs.
-     *
-     * @param headerTitleRes The title string resource to use for a header created out of an
-     *   instance of this enum.
-     */
-    private enum class AlbumGrouping(@StringRes val headerTitleRes: Int) {
-        ALBUMS(R.string.lbl_albums),
-        EPS(R.string.lbl_eps),
-        SINGLES(R.string.lbl_singles),
-        COMPILATIONS(R.string.lbl_compilations),
-        SOUNDTRACKS(R.string.lbl_soundtracks),
-        DJMIXES(R.string.lbl_mixes),
-        MIXTAPES(R.string.lbl_mixtapes),
-        DEMOS(R.string.lbl_demos),
-        APPEARANCES(R.string.lbl_appears_on),
-        LIVE(R.string.lbl_live_group),
-        REMIXES(R.string.lbl_remix_group),
-    }
-
-    private companion object {
-        val ARTIST_ALBUM_SORT = Sort(Sort.Mode.ByDate, Sort.Direction.DESCENDING)
-        val GENRE_ARTIST_SORT = Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
+        _playlistSongInstructions.put(instructions)
     }
 }
 

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

@@ -46,13 +46,12 @@ interface ListSettings : Settings<ListSettings.Listener> {
 
     interface Listener {
         fun onSongSortChanged() {}
-
         fun onAlbumSortChanged() {}
-
+        fun onAlbumSongSortChanged() {}
         fun onArtistSortChanged() {}
-
+        fun onArtistSongSortChanged() {}
         fun onGenreSortChanged() {}
-
+        fun onGenreSongSortChanged() {}
         fun onPlaylistSortChanged() {}
     }
 }
@@ -162,8 +161,11 @@ class ListSettingsImpl @Inject constructor(@ApplicationContext val context: Cont
         when (key) {
             getString(R.string.set_key_songs_sort) -> listener.onSongSortChanged()
             getString(R.string.set_key_albums_sort) -> listener.onAlbumSortChanged()
+            getString(R.string.set_key_album_songs_sort) -> listener.onAlbumSongSortChanged()
             getString(R.string.set_key_artists_sort) -> listener.onArtistSortChanged()
+            getString(R.string.set_key_artist_songs_sort) -> listener.onArtistSongSortChanged()
             getString(R.string.set_key_genres_sort) -> listener.onGenreSortChanged()
+            getString(R.string.set_key_genre_songs_sort) -> listener.onGenreSongSortChanged()
             getString(R.string.set_key_playlists_sort) -> listener.onPlaylistSortChanged()
         }
     }

app/src/main/java/org/oxycblt/auxio/music/service/MediaItemTranslation.kt

@@ -130,6 +130,10 @@ fun header(@StringRes nameRes: Int): Sugar = {
         MediaConstants.DESCRIPTION_EXTRAS_KEY_CONTENT_STYLE_GROUP_TITLE, it.getString(nameRes))
 }
 
+fun header(name: String): Sugar = {
+    putString(MediaConstants.DESCRIPTION_EXTRAS_KEY_CONTENT_STYLE_GROUP_TITLE, name)
+}
+
 private fun style(style: Int): Sugar = {
     putInt(MediaConstants.DESCRIPTION_EXTRAS_KEY_CONTENT_STYLE_SINGLE_ITEM, style)
 }

app/src/main/java/org/oxycblt/auxio/music/service/MusicBrowser.kt

@@ -22,7 +22,12 @@ import android.content.Context
 import android.support.v4.media.MediaBrowserCompat.MediaItem
 import javax.inject.Inject
 import org.oxycblt.auxio.R
+import org.oxycblt.auxio.detail.DetailGenerator
+import org.oxycblt.auxio.detail.DetailSection
+import org.oxycblt.auxio.detail.list.SortHeader
 import org.oxycblt.auxio.home.HomeGenerator
+import org.oxycblt.auxio.list.BasicHeader
+import org.oxycblt.auxio.list.Divider
 import org.oxycblt.auxio.list.ListSettings
 import org.oxycblt.auxio.list.adapter.UpdateInstructions
 import org.oxycblt.auxio.list.sort.Sort
@@ -42,17 +47,17 @@ private constructor(
     private val invalidator: Invalidator,
     private val musicRepository: MusicRepository,
     private val searchEngine: SearchEngine,
-    private val listSettings: ListSettings,
-    homeGeneratorFactory: HomeGenerator.Factory
-) : MusicRepository.UpdateListener, HomeGenerator.Invalidator {
+    homeGeneratorFactory: HomeGenerator.Factory,
+    detailGeneratorFactory: DetailGenerator.Factory
+) : HomeGenerator.Invalidator, DetailGenerator.Invalidator {
 
     class Factory
     @Inject
     constructor(
         private val musicRepository: MusicRepository,
         private val searchEngine: SearchEngine,
-        private val listSettings: ListSettings,
-        private val homeGeneratorFactory: HomeGenerator.Factory
+        private val homeGeneratorFactory: HomeGenerator.Factory,
+        private val detailGeneratorFactory: DetailGenerator.Factory
     ) {
         fun create(context: Context, invalidator: Invalidator): MusicBrowser =
             MusicBrowser(
@@ -60,8 +65,8 @@ private constructor(
                 invalidator,
                 musicRepository,
                 searchEngine,
-                listSettings,
-                homeGeneratorFactory)
+                homeGeneratorFactory,
+                detailGeneratorFactory)
     }
 
     interface Invalidator {
@@ -69,13 +74,11 @@ private constructor(
     }
 
     private val homeGenerator = homeGeneratorFactory.create(this)
-
-    init {
-        musicRepository.addUpdateListener(this)
-    }
+    private val detailGenerator = detailGeneratorFactory.create(this)
 
     fun release() {
-        musicRepository.removeUpdateListener(this)
+        homeGenerator.release()
+        detailGenerator.release()
     }
 
     override fun invalidateMusic(type: MusicType, instructions: UpdateInstructions) {
@@ -92,36 +95,21 @@ private constructor(
         }
     }
 
-    override fun onMusicChanges(changes: MusicRepository.Changes) {
-        val deviceLibrary = musicRepository.deviceLibrary
-        val invalidate = mutableSetOf<String>()
-        if (changes.deviceLibrary && deviceLibrary != null) {
-            deviceLibrary.albums.forEach {
-                val id = MediaSessionUID.SingleItem(it.uid).toString()
-                invalidate.add(id)
-            }
-
-            deviceLibrary.artists.forEach {
-                val id = MediaSessionUID.SingleItem(it.uid).toString()
-                invalidate.add(id)
-            }
-
-            deviceLibrary.genres.forEach {
-                val id = MediaSessionUID.SingleItem(it.uid).toString()
-                invalidate.add(id)
-            }
+    override fun invalidate(type: MusicType, replace: Int?) {
+        val deviceLibrary = musicRepository.deviceLibrary ?: return
+        val userLibrary = musicRepository.userLibrary ?: return
+        val music = when (type) {
+            MusicType.ALBUMS -> deviceLibrary.albums
+            MusicType.ARTISTS -> deviceLibrary.artists
+            MusicType.GENRES -> deviceLibrary.genres
+            MusicType.PLAYLISTS -> userLibrary.playlists
+            else -> return
         }
-        val userLibrary = musicRepository.userLibrary
-        if (changes.userLibrary && userLibrary != null) {
-            userLibrary.playlists.forEach {
-                val id = MediaSessionUID.SingleItem(it.uid).toString()
-                invalidate.add(id)
-            }
-        }
-
-        if (invalidate.isNotEmpty()) {
-            invalidator?.invalidateMusic(invalidate)
+        if (music.isEmpty()) {
+            return
         }
+        val ids = music.map { MediaSessionUID.SingleItem(it.uid).toString() }.toSet()
+        invalidator.invalidateMusic(ids)
     }
 
     fun getItem(mediaId: String): MediaItem? {
@@ -235,34 +223,25 @@ private constructor(
         }
 
     private fun getChildMediaItems(uid: Music.UID): List<MediaItem>? {
-        return when (val item = musicRepository.find(uid)) {
-            is Album -> {
-                val songs = listSettings.albumSongSort.songs(item.songs)
-                songs.map { it.toMediaItem(context, item, header(R.string.lbl_songs)) }
+        val detail = detailGenerator.any(uid) ?: return null
+        return detail.sections.flatMap { section ->
+            when (section) {
+                is DetailSection.Songs -> section.items.map { it.toMediaItem(context, null, header(section.stringRes)) }
+                is DetailSection.Albums -> section.items.map { it.toMediaItem(context, null, header(section.stringRes)) }
+                is DetailSection.Artists -> section.items.map { it.toMediaItem(context, header(section.stringRes)) }
+                is DetailSection.Discs -> section.discs.flatMap {
+                    section.discs.flatMap { entry ->
+                        val disc = entry.key
+                        val discString = if (disc != null) {
+                            context.getString(R.string.fmt_disc_no, disc.number)
+                        } else {
+                            context.getString(R.string.def_disc)
+                        }
+                        entry.value.map { it.toMediaItem(context, null, header(discString)) }
+                    }
+                }
+                else -> error("Unknown section type: $section")
             }
-            is Artist -> {
-                val albums = ARTIST_ALBUMS_SORT.albums(item.explicitAlbums + item.implicitAlbums)
-                val songs = listSettings.artistSongSort.songs(item.songs)
-                albums.map { it.toMediaItem(context, null, header(R.string.lbl_songs)) } +
-                    songs.map { it.toMediaItem(context, item, header(R.string.lbl_songs)) }
-            }
-            is Genre -> {
-                val artists = GENRE_ARTISTS_SORT.artists(item.artists)
-                val songs = listSettings.genreSongSort.songs(item.songs)
-                artists.map { it.toMediaItem(context, header(R.string.lbl_songs)) } +
-                    songs.map { it.toMediaItem(context, null, header(R.string.lbl_songs)) }
-            }
-            is Playlist -> {
-                item.songs.map { it.toMediaItem(context, null, header(R.string.lbl_songs)) }
-            }
-            is Song,
-            null -> return null
         }
     }
-
-    private companion object {
-        // TODO: Rely on detail item gen logic?
-        val ARTIST_ALBUMS_SORT = Sort(Sort.Mode.ByDate, Sort.Direction.DESCENDING)
-        val GENRE_ARTISTS_SORT = Sort(Sort.Mode.ByName, Sort.Direction.ASCENDING)
-    }
 }