detail: respond to automatic rescanning

Make the detail UIs respond to automatic rescanning events.

This currently has no effect, but is instead a preparation step for the
seamless addition of automatic rescanning.

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

@@ -69,6 +69,7 @@ class AlbumDetailFragment : DetailFragment(), AlbumDetailAdapter.Listener {
 
         // -- VIEWMODEL SETUP ---
 
+        launch { detailModel.currentAlbum.collect(::handleItemChange) }
         launch { detailModel.albumData.collect(detailAdapter.data::submitList) }
         launch { navModel.exploreNavigationItem.collect(::handleNavigation) }
         launch { playbackModel.song.collectWith(playbackModel.parent, ::updatePlayback) }
@@ -127,6 +128,12 @@ class AlbumDetailFragment : DetailFragment(), AlbumDetailAdapter.Listener {
                     unlikelyToBeNull(detailModel.currentAlbum.value).artist.id))
     }
 
+    private fun handleItemChange(album: Album?) {
+        if (album == null) {
+            findNavController().navigateUp()
+        }
+    }
+
     private fun handleNavigation(item: Music?) {
         val binding = requireBinding()
         when (item) {

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

@@ -66,6 +66,7 @@ class ArtistDetailFragment : DetailFragment(), DetailAdapter.Listener {
 
         // --- VIEWMODEL SETUP ---
 
+        launch { detailModel.currentArtist.collect(::handleItemChange) }
         launch { detailModel.artistData.collect(detailAdapter.data::submitList) }
         launch { navModel.exploreNavigationItem.collect(::handleNavigation) }
         launch { playbackModel.song.collectWith(playbackModel.parent, ::updatePlayback) }
@@ -104,6 +105,12 @@ class ArtistDetailFragment : DetailFragment(), DetailAdapter.Listener {
             })
     }
 
+    private fun handleItemChange(artist: Artist?) {
+        if (artist == null) {
+            findNavController().navigateUp()
+        }
+    }
+
     private fun handleNavigation(item: Music?) {
         val binding = requireBinding()
 

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

@@ -41,7 +41,7 @@ import org.oxycblt.auxio.util.unlikelyToBeNull
  * - Menu triggers for each fragment
  * @author OxygenCobalt
  */
-class DetailViewModel : ViewModel() {
+class DetailViewModel : ViewModel(), MusicStore.Callback {
     private val musicStore = MusicStore.getInstance()
     private val settingsManager = SettingsManager.getInstance()
 
@@ -116,6 +116,10 @@ class DetailViewModel : ViewModel() {
         refreshGenreData(genre)
     }
 
+    init {
+        musicStore.addCallback(this)
+    }
+
     private fun refreshAlbumData(album: Album) {
         logD("Refreshing album data")
         val data = mutableListOf<Item>(album)
@@ -157,4 +161,38 @@ class DetailViewModel : ViewModel() {
         data.addAll(genreSort.songs(genre.songs))
         _genreData.value = data
     }
+
+    // --- CALLBACKS ---
+
+    override fun onLibraryChanged(library: MusicStore.Library?) {
+        if (library != null) {
+            val album = currentAlbum.value
+            if (album != null) {
+                val newAlbum = library.sanitize(album).also { _currentAlbum.value = it }
+                if (newAlbum != null) {
+                    refreshAlbumData(newAlbum)
+                }
+            }
+
+            val artist = currentArtist.value
+            if (artist != null) {
+                val newArtist = library.sanitize(artist).also { _currentArtist.value = it }
+                if (newArtist != null) {
+                    refreshArtistData(newArtist)
+                }
+            }
+
+            val genre = currentGenre.value
+            if (genre != null) {
+                val newGenre = library.sanitize(genre).also { _currentGenre.value = it }
+                if (newGenre != null) {
+                    refreshGenreData(newGenre)
+                }
+            }
+        }
+    }
+
+    override fun onCleared() {
+        musicStore.removeCallback(this)
+    }
 }

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

@@ -65,6 +65,7 @@ class GenreDetailFragment : DetailFragment(), DetailAdapter.Listener {
 
         // --- VIEWMODEL SETUP ---
 
+        launch { detailModel.currentGenre.collect(::handleItemChange) }
         launch { detailModel.genreData.collect(detailAdapter.data::submitList) }
         launch { navModel.exploreNavigationItem.collect(::handleNavigation) }
         launch { playbackModel.song.collectWith(playbackModel.parent, ::updatePlayback) }
@@ -101,6 +102,12 @@ class GenreDetailFragment : DetailFragment(), DetailAdapter.Listener {
             showItem = { it != R.id.option_sort_disc && it != R.id.option_sort_track })
     }
 
+    private fun handleItemChange(genre: Genre?) {
+        if (genre == null) {
+            findNavController().navigateUp()
+        }
+    }
+
     private fun handleNavigation(item: Music?) {
         when (item) {
             is Song -> {

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

@@ -148,7 +148,8 @@ class Indexer {
             // 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) }
+                indexingState?.let { State.Indexing(it) }
+                    ?: lastResponse?.let { State.Complete(it) }
 
             for (callback in callbacks) {
                 callback.onIndexerStateChanged(state)
@@ -180,7 +181,8 @@ class Indexer {
         emitIndexing(Indexing.Indeterminate, generation)
 
         // Establish the backend to use when initially loading songs.
-        val mediaStoreBackend = when {
+        val mediaStoreBackend =
+            when {
                 Build.VERSION.SDK_INT >= Build.VERSION_CODES.R -> Api30MediaStoreBackend()
                 Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q -> Api29MediaStoreBackend()
                 else -> Api21MediaStoreBackend()
@@ -229,7 +231,9 @@ class Indexer {
                     "Successfully queried media database " +
                         "in ${System.currentTimeMillis() - start}ms")
 
-                backend.buildSongs(context, cursor) { indexing -> emitIndexing(indexing, generation) }
+                backend.buildSongs(context, cursor) { indexing ->
+                    emitIndexing(indexing, generation)
+                }
             }
 
         // Deduplicate songs to prevent (most) deformed music clones

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

@@ -77,6 +77,12 @@ class MusicStore private constructor() {
 
                 songs.find { it.fileName == displayName }
             }
+
+        /** "Sanitize" a music object from a previous library iteration. */
+        fun sanitize(song: Song) = songs.find { it.id == song.id }
+        fun sanitize(album: Album) = albums.find { it.id == album.id }
+        fun sanitize(artist: Artist) = artists.find { it.id == artist.id }
+        fun sanitize(genre: Genre) = genres.find { it.id == genre.id }
     }
 
     /** A callback for awaiting the loading of music. */

app/src/main/java/org/oxycblt/auxio/music/excluded/ExcludedDirectory.kt

@@ -21,6 +21,13 @@ import android.os.Build
 import java.io.File
 import org.oxycblt.auxio.util.logW
 
+/**
+ * Represents a directory excluded from the music loading process. This is a in-code
+ * representation of a typical document tree URI scheme, designed to not only provide
+ * support for external volumes, but also provide it in a way compatible with older
+ * android versions.
+ * @author OxygenCobalt
+ */
 data class ExcludedDirectory(val volume: Volume, val relativePath: String) {
     override fun toString(): String = "${volume}:$relativePath"
 
@@ -50,6 +57,9 @@ data class ExcludedDirectory(val volume: Volume, val relativePath: String) {
 
             val volume = Volume.fromString(split.getOrNull(0) ?: return null)
             if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q && volume is Volume.Secondary) {
+                // While Android Q provides a stable way of accessing volumes, we can't trust
+                // that DATA provides a stable volume scheme on older versions, so external
+                // volumes are not supported.
                 logW("Cannot use secondary volumes below API 29")
                 return null
             }

app/src/main/java/org/oxycblt/auxio/settings/AboutFragment.kt

@@ -81,8 +81,7 @@ class AboutFragment : ViewBindingFragment<FragmentAboutBinding>() {
     }
 
     private fun updateAlbumCount(albums: List<Album>) {
-        requireBinding().aboutAlbumCount.textSafe =
-            getString(R.string.fmt_album_count, albums.size)
+        requireBinding().aboutAlbumCount.textSafe = getString(R.string.fmt_album_count, albums.size)
     }
 
     private fun updateArtistCount(artists: List<Artist>) {
@@ -91,8 +90,7 @@ class AboutFragment : ViewBindingFragment<FragmentAboutBinding>() {
     }
 
     private fun updateGenreCount(genres: List<Genre>) {
-        requireBinding().aboutGenreCount.textSafe =
-            getString(R.string.fmt_genre_count, genres.size)
+        requireBinding().aboutGenreCount.textSafe = getString(R.string.fmt_genre_count, genres.size)
     }
 
     /** Go through the process of opening a [link] in a browser. */