home: play the whole genre list from a genre song row

app/src/main/kotlin/com/subtracks/data/db/LibraryDao.kt

@@ -726,6 +726,21 @@ interface LibraryDao {
         genre: String,
     ): PagingSource<Int, AlbumSongItem>
 
+    @Query(
+        "SELECT songs.id FROM songs " +
+            "WHERE songs.sourceId = :sourceId AND (" +
+            "EXISTS (SELECT 1 FROM song_genres " +
+            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id " +
+            "AND song_genres.genre = :genre) " +
+            "OR (songs.genre = :genre AND NOT EXISTS (SELECT 1 FROM song_genres " +
+            "WHERE song_genres.sourceId = songs.sourceId AND song_genres.songId = songs.id))) " +
+            "ORDER BY songs.title COLLATE NOCASE, songs.id",
+    )
+    suspend fun songsByGenreIds(
+        sourceId: Long,
+        genre: String,
+    ): List<String>
+
     @Query(
         "SELECT * FROM albums WHERE sourceId = :sourceId AND year >= :start AND year < :end " +
             "ORDER BY year DESC, name COLLATE NOCASE, id",

app/src/main/kotlin/com/subtracks/data/repo/LibraryRepository.kt

@@ -95,6 +95,11 @@ class LibraryRepository(
         genre: String,
     ): Flow<PagingData<AlbumSongItem>> = pager(60) { db.libraryDao().songsByGenre(sourceId, genre) }
 
+    suspend fun genreSongIds(
+        sourceId: Long,
+        genre: String,
+    ): List<String> = db.libraryDao().songsByGenreIds(sourceId, genre)
+
     fun albumsByDecade(
         sourceId: Long,
         decade: Long,

app/src/main/kotlin/com/subtracks/ui/home/HomeListViewModel.kt

@@ -111,10 +111,23 @@ class HomeListViewModel(
     ): CoverArtRef? = sourceRepository.coverArt(coverArt, thumbnail)
 
     fun play(song: Song) {
-        if (request.section == HomeSection.RecentlyStarredSongs) {
-            viewModelScope.playStarredList(libraryRepository, playbackController, song)
-        } else {
-            viewModelScope.playSongInContext(libraryRepository, playbackController, song)
+        val genre = request.genre
+        when {
+            genre != null -> {
+                viewModelScope.playGenreList(libraryRepository, playbackController, genre, song)
+            }
+
+            request.section == HomeSection.RecentlyStarredSongs -> {
+                viewModelScope.playStarredList(
+                    libraryRepository,
+                    playbackController,
+                    song,
+                )
+            }
+
+            else -> {
+                viewModelScope.playSongInContext(libraryRepository, playbackController, song)
+            }
         }
     }
 }

app/src/main/kotlin/com/subtracks/ui/home/HomeViewModel.kt

@@ -173,3 +173,15 @@ internal fun CoroutineScope.playStarredList(
         playbackController.playSongs(song.sourceId, ids, ids.indexOf(song.id).coerceAtLeast(0))
     }
 }
+
+internal fun CoroutineScope.playGenreList(
+    libraryRepository: LibraryRepository,
+    playbackController: PlaybackController,
+    genre: String,
+    song: Song,
+) {
+    launch {
+        val ids = libraryRepository.genreSongIds(song.sourceId, genre)
+        playbackController.playSongs(song.sourceId, ids, ids.indexOf(song.id).coerceAtLeast(0))
+    }
+}

app/src/test/kotlin/com/subtracks/data/db/LibraryHomeDaoTest.kt

@@ -182,6 +182,7 @@ class LibraryHomeDaoTest {
             val page = dao.songsByGenre(sourceId, "Rock").page()
             assertEquals(listOf("s1", "s2"), page.map { it.song.id })
             assertEquals("cover-1", page.first().coverArt)
+            assertEquals(page.map { it.song.id }, dao.songsByGenreIds(sourceId, "Rock"))
         }
 
     private suspend fun insertGenre(