playback: revert the restored session prepare

Preparing the restored window on launch was meant to make the paused
session reachable from Bluetooth and Automate. The follow-up on the issue
shows the notification appears, but the car's play command still does not
reach the app until the phone is unlocked, and the speculative prepare
buffered up to 50 seconds of the restored track on every launch while
claiming the media controls whenever the app opened.

Removing the prepare also removes the error gate it needed, which could
hide genuine playback errors while paused.

Reverts #230.

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

@@ -214,14 +214,34 @@ interface QueueDao {
     ): List<String>
 
     @Query(
-        "SELECT songs.*, albums.coverArt AS coverArt FROM songs " +
-            "LEFT JOIN albums ON albums.sourceId = songs.sourceId AND albums.id = songs.albumId " +
-            "WHERE songs.sourceId = :sourceId AND songs.id IN (:ids)",
+        "SELECT CASE WHEN EXISTS (SELECT 1 FROM songs WHERE sourceId = :sourceId AND albumId = :albumId AND id = :songId) " +
+            "THEN (SELECT COUNT(*) FROM songs ranked CROSS JOIN songs target " +
+            "WHERE ranked.sourceId = :sourceId AND ranked.albumId = :albumId " +
+            "AND target.sourceId = :sourceId AND target.albumId = :albumId AND target.id = :songId " +
+            "AND ((ranked.disc IS NULL AND target.disc IS NOT NULL) OR ranked.disc < target.disc OR " +
+            "(ranked.disc IS target.disc AND ((ranked.track IS NULL AND target.track IS NOT NULL) OR ranked.track < target.track OR " +
+            "(ranked.track IS target.track AND ranked.id < target.id))))) END",
     )
-    suspend fun songsByIds(
+    suspend fun albumRank(
         sourceId: Long,
-        ids: List<String>,
-    ): List<AlbumSongItem>
+        albumId: String,
+        songId: String,
+    ): Long?
+
+    @Query(
+        "SELECT CASE WHEN firstPosition IS NULL THEN NULL ELSE " +
+            "(SELECT COUNT(*) - 1 FROM playlist_songs " +
+            "JOIN songs ON songs.sourceId = playlist_songs.sourceId AND songs.id = playlist_songs.songId " +
+            "WHERE playlist_songs.sourceId = :sourceId AND playlist_songs.playlistId = :playlistId AND position <= firstPosition) END " +
+            "FROM (SELECT MIN(position) AS firstPosition FROM playlist_songs " +
+            "JOIN songs ON songs.sourceId = playlist_songs.sourceId AND songs.id = playlist_songs.songId " +
+            "WHERE playlist_songs.sourceId = :sourceId AND playlist_songs.playlistId = :playlistId AND songId = :songId)",
+    )
+    suspend fun playlistRank(
+        sourceId: Long,
+        playlistId: String,
+        songId: String,
+    ): Long?
 
     @Query("SELECT COUNT(*) FROM song_genres WHERE sourceId = :sourceId AND genre = :genre")
     suspend fun genreLength(
@@ -243,17 +263,6 @@ interface QueueDao {
         limit: Int,
     ): List<AlbumSongItem>
 
-    @Query(
-        "SELECT songs.id FROM song_genres " +
-            "JOIN songs ON songs.sourceId = song_genres.sourceId AND songs.id = song_genres.songId " +
-            "WHERE song_genres.sourceId = :sourceId AND song_genres.genre = :genre " +
-            "ORDER BY songs.sortName COLLATE NOCASE, songs.id",
-    )
-    suspend fun genreSongIds(
-        sourceId: Long,
-        genre: String,
-    ): List<String>
-
     @Query("SELECT COUNT(*) FROM song_downloads WHERE sourceId = :sourceId AND status = 'Completed'")
     suspend fun downloadedLength(sourceId: Long): Long
 
@@ -272,12 +281,6 @@ interface QueueDao {
         limit: Int,
     ): List<AlbumSongItem>
 
-    @Query(
-        "SELECT songs.id FROM songs WHERE sourceId = :sourceId AND starred IS NOT NULL " +
-            "ORDER BY starred DESC, sortName COLLATE NOCASE, id",
-    )
-    suspend fun starredSongIds(sourceId: Long): List<String>
-
     @Query(
         "SELECT songs.*, albums.coverArt AS coverArt FROM song_downloads d " +
             "JOIN songs ON songs.sourceId = d.sourceId AND songs.id = d.songId " +
@@ -290,12 +293,4 @@ interface QueueDao {
         offset: Long,
         limit: Int,
     ): List<AlbumSongItem>
-
-    @Query(
-        "SELECT songs.id FROM song_downloads d " +
-            "JOIN songs ON songs.sourceId = d.sourceId AND songs.id = d.songId " +
-            "WHERE d.sourceId = :sourceId AND d.status = 'Completed' " +
-            "ORDER BY d.downloadedAt DESC, songs.sortName COLLATE NOCASE, songs.id",
-    )
-    suspend fun downloadedSongIds(sourceId: Long): List<String>
 }

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

@@ -360,10 +360,7 @@ class LibraryRepository(
         sourceId: Long,
         albumId: String,
         songId: String,
-    ): Long {
-        val index = db.queueDao().albumSongIds(sourceId, albumId).indexOf(songId)
-        return if (index < 0) 0L else index.toLong()
-    }
+    ): Long = db.queueDao().albumRank(sourceId, albumId, songId) ?: 0L
 
     fun playlist(
         sourceId: Long,

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

@@ -209,6 +209,202 @@ data class Reanchored(
     val changed: Boolean,
 )
 
+private interface QueueKindResolver {
+    fun supportsKeyset(key: OrderKey): Boolean = false
+
+    suspend fun length(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+    ): Long
+
+    suspend fun rows(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        offset: Long,
+        limit: Int,
+    ): List<SongItem>
+
+    suspend fun rowsFrom(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        key: OrderKey,
+        skip: Long,
+        limit: Int,
+    ): List<SongItem>? = null
+
+    suspend fun rowsBefore(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        key: OrderKey,
+        skip: Long,
+        limit: Int,
+    ): List<SongItem>? = null
+
+    suspend fun rank(
+        dao: com.subtracks.data.db.QueueDao,
+        entry: QueueEntry,
+        songId: String,
+    ): Long? = null
+}
+
+private val queueKindResolvers =
+    mapOf<QueueKind, QueueKindResolver>(
+        QueueKind.Song to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.songLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.song(entry.sourceId, entry.refId, offset, limit)
+
+                override suspend fun rank(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    songId: String,
+                ) = if (entry.refId == songId && length(dao, entry) > 0) 0L else null
+            },
+        QueueKind.Playlist to
+            object : QueueKindResolver {
+                override fun supportsKeyset(key: OrderKey) = key.position != null
+
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.playlistLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.playlistSongs(entry.sourceId, entry.refId, offset, limit)
+
+                override suspend fun rowsFrom(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.playlistSongsFrom(entry.sourceId, entry.refId, key.position!!, skip, limit)
+
+                override suspend fun rowsBefore(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.playlistSongsBefore(entry.sourceId, entry.refId, key.position!!, skip, limit)
+
+                override suspend fun rank(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    songId: String,
+                ) = dao.playlistRank(entry.sourceId, entry.refId, songId)
+            },
+        QueueKind.Album to
+            object : QueueKindResolver {
+                override fun supportsKeyset(key: OrderKey) = key.disc != null && key.track != null
+
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.albumLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.albumSongs(entry.sourceId, entry.refId, offset, limit)
+
+                override suspend fun rowsFrom(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.albumSongsFrom(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
+
+                override suspend fun rowsBefore(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    key: OrderKey,
+                    skip: Long,
+                    limit: Int,
+                ) = dao.albumSongsBefore(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
+
+                override suspend fun rank(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    songId: String,
+                ) = dao.albumRank(entry.sourceId, entry.refId, songId)
+            },
+        QueueKind.Artist to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.artistLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.artistSongs(entry.sourceId, entry.refId, offset, limit)
+            },
+        QueueKind.Genre to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.genreLength(entry.sourceId, entry.refId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.genreSongs(entry.sourceId, entry.refId, offset, limit)
+            },
+        QueueKind.Downloaded to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.downloadedLength(entry.sourceId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.downloadedSongs(entry.sourceId, offset, limit)
+            },
+        QueueKind.Starred to
+            object : QueueKindResolver {
+                override suspend fun length(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                ) = dao.starredLength(entry.sourceId)
+
+                override suspend fun rows(
+                    dao: com.subtracks.data.db.QueueDao,
+                    entry: QueueEntry,
+                    offset: Long,
+                    limit: Int,
+                ) = dao.starredSongs(entry.sourceId, offset, limit)
+            },
+    )
+
+private fun resolverFor(kind: QueueKind): QueueKindResolver = queueKindResolvers.getValue(kind)
+
 class QueueRepository(
     private val db: SubtracksDatabase,
 ) {
@@ -216,12 +412,6 @@ class QueueRepository(
 
     private val queueVersion = AtomicLong()
 
-    @Volatile
-    private var cachedFlatIds: List<String>? = null
-
-    @Volatile
-    private var cachedFlatVersion = -1L
-
     @Volatile
     private var shuffleRemoved: ShuffleState? = null
 
@@ -235,6 +425,9 @@ class QueueRepository(
     internal var offsetSeeks = 0L
         private set
 
+    internal var resolvedRowCount = 0L
+        private set
+
     private val cursorMutex = Mutex()
 
     fun playlistEntry(
@@ -388,7 +581,6 @@ class QueueRepository(
     }
 
     fun invalidateLibraryCache() {
-        cachedFlatIds = null
         lengthCache.clear()
         keyCache.clear()
         shuffleRemoved = null
@@ -409,8 +601,8 @@ class QueueRepository(
         snapshot: QueueSnapshot,
         songId: String,
     ): Long? {
-        val upIndex = idsFor(snapshot.upNext).indexOf(songId)
-        if (upIndex >= 0) return snapshot.anchorPlay + 1 + upIndex
+        val upIndex = flatIndexOf(snapshot.upNext, songId)
+        if (upIndex != null) return snapshot.anchorPlay + 1 + upIndex
         return combinedContextIndexOf(snapshot, songId)
     }
 
@@ -418,9 +610,8 @@ class QueueRepository(
         snapshot: QueueSnapshot,
         songId: String,
     ): Long? {
-        val flat = flatIds(snapshot).indexOf(songId)
-        if (flat < 0) return null
-        return snapshot.playContext(flat.toLong())?.let { snapshot.combined(it) }
+        val flat = flatIndexOf(snapshot.entries, songId) ?: return null
+        return snapshot.playContext(flat)?.let { snapshot.combined(it) }
     }
 
     suspend fun range(
@@ -633,7 +824,6 @@ class QueueRepository(
             }
         }
         queueVersion.incrementAndGet()
-        cachedFlatIds = null
     }
 
     private suspend fun writeUpNext(entries: List<QueueEntry>) {
@@ -650,34 +840,40 @@ class QueueRepository(
         queueVersion.incrementAndGet()
     }
 
-    private suspend fun flatIds(snapshot: QueueSnapshot): List<String> {
-        val cached = cachedFlatIds
-        if (cached != null && cachedFlatVersion == snapshot.version && cached.size.toLong() == snapshot.contextSize) return cached
-        val ids = idsFor(snapshot.entries)
-        cachedFlatIds = ids
-        cachedFlatVersion = snapshot.version
-        return ids
+    private suspend fun flatIndexOf(
+        entries: List<ResolvedQueueEntry>,
+        songId: String,
+    ): Long? {
+        var start = 0L
+        for (resolved in entries) {
+            val entry = resolved.entry
+            val rank = resolverFor(entry.kind).rank(dao, entry, songId)
+            if (rank != null && rank >= entry.offset && rank < entry.offset + resolved.length) {
+                return start + rank - entry.offset
+            }
+            val fallback = fallbackRank(entry, resolved.length, songId)
+            if (fallback != null) return start + fallback - entry.offset
+            start += resolved.length
+        }
+        return null
     }
 
-    private suspend fun idsFor(resolved: List<ResolvedQueueEntry>): List<String> {
-        val ids = ArrayList<String>()
-        for (entry in resolved) {
-            val ref = entry.entry
-            val entryIds =
-                when (ref.kind) {
-                    QueueKind.Song -> listOf(ref.refId)
-                    QueueKind.Album -> dao.albumSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Playlist -> dao.playlistSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Artist -> dao.artistSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Genre -> dao.genreSongIds(ref.sourceId, ref.refId)
-                    QueueKind.Downloaded -> dao.downloadedSongIds(ref.sourceId)
-                    QueueKind.Starred -> dao.starredSongIds(ref.sourceId)
-                }
-            val from = ref.offset.toInt().coerceIn(0, entryIds.size)
-            val to = (ref.offset + entry.length).toInt().coerceIn(from, entryIds.size)
-            ids.addAll(entryIds.subList(from, to))
+    private suspend fun fallbackRank(
+        entry: QueueEntry,
+        length: Long,
+        songId: String,
+    ): Long? {
+        var offset = entry.offset
+        val end = entry.offset + length
+        while (offset < end) {
+            val limit = minOf(QUEUE_CHUNK.toLong(), end - offset).toInt()
+            val batch = rows(entry, offset, limit)
+            val index = batch.indexOfFirst { it.song.id == songId }
+            if (index >= 0) return offset + index
+            if (batch.size < limit) return null
+            offset += batch.size
         }
-        return ids
+        return null
     }
 
     private suspend fun contextPlayRange(
@@ -688,21 +884,11 @@ class QueueRepository(
         if (first > last) return emptyList()
         val items = mutableListOf<QueueWindowItem>()
         if (snapshot.shuffled) {
-            val sourceId =
-                snapshot.entries
-                    .firstOrNull()
-                    ?.entry
-                    ?.sourceId ?: return emptyList()
-            val ids = flatIds(snapshot)
-            val requested = mutableListOf<Pair<Long, String>>()
             for (play in first..last) {
-                val flat = snapshot.flatContext(play) ?: continue
-                val id = ids.getOrNull(flat.toInt()) ?: continue
-                requested += play to id
+                val located = snapshot.locateContext(play) ?: continue
+                val item = rows(located.first, located.first.offset + located.second, 1).firstOrNull() ?: continue
+                items += QueueWindowItem(snapshot.combined(play), item, playlistPosition = item.playlistPosition)
             }
-            if (requested.isEmpty()) return emptyList()
-            val byId = dao.songsByIds(sourceId, requested.map { it.second }.distinct()).associateBy { it.song.id }
-            requested.forEach { (play, id) -> byId[id]?.let { items += QueueWindowItem(snapshot.combined(play), it) } }
             return items
         }
         var start = 0L
@@ -757,27 +943,20 @@ class QueueRepository(
     ): List<SongItem> {
         if (entry.kind == QueueKind.Song) {
             offsetSeeks++
-            return dao.song(entry.sourceId, entry.refId, offset, limit)
+            return resolverFor(entry.kind).rows(dao, entry, offset, limit).also { resolvedRowCount += it.size }
         }
         val ref = QueueRef(entry.kind, entry.sourceId, entry.refId)
         val anchored = keyCache[ref]?.let { keyedRows(entry, offset, limit, it) }
         if (anchored != null) {
             keysetSeeks++
             if (anchored.isNotEmpty()) remember(ref, offset, anchored)
+            resolvedRowCount += anchored.size
             return anchored
         }
         offsetSeeks++
-        val fresh =
-            when (entry.kind) {
-                QueueKind.Playlist -> dao.playlistSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Album -> dao.albumSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Artist -> dao.artistSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Genre -> dao.genreSongs(entry.sourceId, entry.refId, offset, limit)
-                QueueKind.Downloaded -> dao.downloadedSongs(entry.sourceId, offset, limit)
-                QueueKind.Starred -> dao.starredSongs(entry.sourceId, offset, limit)
-                QueueKind.Song -> emptyList()
-            }
+        val fresh = resolverFor(entry.kind).rows(dao, entry, offset, limit)
         if (fresh.isNotEmpty()) remember(ref, offset, fresh)
+        resolvedRowCount += fresh.size
         return fresh
     }
 
@@ -810,7 +989,7 @@ class QueueRepository(
         limit: Int,
         cursor: KeyCursor,
     ): List<SongItem>? {
-        if (!cursor.key.seekable(entry.kind)) return null
+        if (!resolverFor(entry.kind).supportsKeyset(cursor.key)) return null
         val from = cursor.ordinal
         // A backward seek from a far cursor is not cheaper than the offset query: the album
         // predicate is not sargable (it has to include NULL disc/track), so it scans the partition
@@ -836,43 +1015,14 @@ class QueueRepository(
         key: OrderKey,
         skip: Long,
         limit: Int,
-    ): List<SongItem> =
-        when (entry.kind) {
-            QueueKind.Playlist -> dao.playlistSongsFrom(entry.sourceId, entry.refId, key.position!!, skip, limit)
-            QueueKind.Album -> dao.albumSongsFrom(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
-            QueueKind.Artist -> emptyList()
-            QueueKind.Genre -> emptyList()
-            QueueKind.Downloaded -> emptyList()
-            QueueKind.Starred -> emptyList()
-            QueueKind.Song -> emptyList()
-        }
+    ): List<SongItem> = resolverFor(entry.kind).rowsFrom(dao, entry, key, skip, limit) ?: emptyList()
 
     private suspend fun rowsBefore(
         entry: QueueEntry,
         key: OrderKey,
         skip: Long,
         limit: Int,
-    ): List<SongItem> =
-        when (entry.kind) {
-            QueueKind.Playlist -> dao.playlistSongsBefore(entry.sourceId, entry.refId, key.position!!, skip, limit)
-            QueueKind.Album -> dao.albumSongsBefore(entry.sourceId, entry.refId, key.disc!!, key.track!!, key.id, skip, limit)
-            QueueKind.Artist -> emptyList()
-            QueueKind.Genre -> emptyList()
-            QueueKind.Downloaded -> emptyList()
-            QueueKind.Starred -> emptyList()
-            QueueKind.Song -> emptyList()
-        }
-
-    private fun OrderKey.seekable(kind: QueueKind): Boolean =
-        when (kind) {
-            QueueKind.Playlist -> position != null
-            QueueKind.Album -> disc != null && track != null
-            QueueKind.Artist -> false
-            QueueKind.Genre -> false
-            QueueKind.Downloaded -> false
-            QueueKind.Starred -> false
-            QueueKind.Song -> false
-        }
+    ): List<SongItem> = resolverFor(entry.kind).rowsBefore(dao, entry, key, skip, limit) ?: emptyList()
 
     private suspend fun lengthOf(
         entry: QueueEntry,
@@ -897,36 +1047,7 @@ class QueueRepository(
         )
 
     private suspend fun QueueEntry.resolvedLength(): Long {
-        val total =
-            when (kind) {
-                QueueKind.Song -> {
-                    dao.songLength(sourceId, refId)
-                }
-
-                QueueKind.Playlist -> {
-                    dao.playlistLength(sourceId, refId)
-                }
-
-                QueueKind.Album -> {
-                    dao.albumLength(sourceId, refId)
-                }
-
-                QueueKind.Artist -> {
-                    dao.artistLength(sourceId, refId)
-                }
-
-                QueueKind.Genre -> {
-                    dao.genreLength(sourceId, refId)
-                }
-
-                QueueKind.Downloaded -> {
-                    dao.downloadedLength(sourceId)
-                }
-
-                QueueKind.Starred -> {
-                    dao.starredLength(sourceId)
-                }
-            }
+        val total = resolverFor(kind).length(dao, this)
         val available = (total - offset).coerceAtLeast(0)
         return count?.coerceAtMost(available) ?: available
     }

app/src/main/kotlin/com/subtracks/playback/PlaybackController.kt

@@ -1070,7 +1070,6 @@ class PlaybackController(
             }
             lastSavedPositionMs = savedPositionMs
             loadWindow(anchor.position, autoplay = false, startPositionMs = savedPositionMs)
-            player?.takeIf { it.itemCount > 0 }?.ensurePrepared()
         }
 
     private suspend fun stop() = startLock.withLock { stopLocked() }
@@ -1452,7 +1451,7 @@ class PlaybackController(
             }
 
             override fun onError(message: UiMessage) {
-                if (player?.playWhenReady == true) showMessage(message)
+                showMessage(message)
                 refresh()
             }
         }

app/src/test/kotlin/com/subtracks/data/repo/QueueKeysetTest.kt

@@ -150,6 +150,18 @@ class QueueKeysetTest {
             assertTrue("backward keyset seeks", repository.keysetSeeks > beforeBackward)
         }
 
+    @Test
+    fun scanningAnAlbumWithNullDiscAndTrackForwardFallsBackToOffsetRows() =
+        runTest {
+            seedLibrary()
+            repository.replace(listOf(repository.albumEntry(1, "mixed")))
+            val snapshot = repository.snapshot()
+
+            val resolved = (0 until snapshot.size).map { repository.itemAt(snapshot, it)?.song?.id }
+
+            assertEquals(listOf("n1", "n2", "s1", "s2"), resolved)
+        }
+
     @Test
     fun scanningAnAlbumWithNullDiscAndTrackBackwardsResolvesEveryRow() =
         runTest {
@@ -260,6 +272,22 @@ class QueueKeysetTest {
             assertTrue(ids.all { it in expected })
         }
 
+    @Test
+    fun thePlaylistWindowQuerySeeksThePositionIndex() =
+        runTest {
+            seedLibrary()
+            val plan =
+                queryPlan(
+                    "SELECT songs.*, playlist_songs.position AS playlistPosition, albums.coverArt AS coverArt " +
+                        "FROM playlist_songs JOIN songs ON songs.sourceId = playlist_songs.sourceId " +
+                        "AND songs.id = playlist_songs.songId LEFT JOIN albums ON albums.sourceId = songs.sourceId " +
+                        "AND albums.id = songs.albumId WHERE playlist_songs.sourceId = 1 " +
+                        "AND playlist_songs.playlistId = 'pl1' ORDER BY playlist_songs.position LIMIT 51 OFFSET 100000",
+                )
+
+            assertTrue(plan.joinToString("\n"), plan.any { it.contains("sqlite_autoindex_playlist_songs_1") })
+        }
+
     @Test
     fun theAlbumKeysetQuerySeeksTheOrderIndex() =
         runTest {

app/src/test/kotlin/com/subtracks/data/repo/QueueRepositoryTest.kt

@@ -727,6 +727,32 @@ class QueueRepositoryTest {
             assertEquals(listOf("s1", "s2", "s3"), resolveAll(restored))
         }
 
+    @Test
+    fun shuffledLargeContextWindowOnlyResolvesRequestedRows() =
+        runTest {
+            seedLibrary()
+            db.libraryDao().upsertPlaylists(listOf(playlist("huge", "Huge")))
+            db.useWriterConnection { transactor ->
+                transactor.usePrepared(
+                    "WITH RECURSIVE n(x) AS (VALUES(0) UNION ALL SELECT x + 1 FROM n WHERE x < 199999) " +
+                        "INSERT INTO playlist_songs SELECT 1, 'huge', 's1', x FROM n",
+                ) { statement ->
+                    statement.step()
+                }
+            }
+            repository.snapshotAfter(listOf(repository.playlistEntry(1, "huge")))
+            repository.setShuffle(42L)
+            val snapshot = repository.snapshot()
+
+            val window = repository.window(snapshot, center = 100_000, radius = 25)
+
+            assertEquals(200_000L, snapshot.contextSize)
+            assertEquals(51, window.size)
+            assertEquals(51L, repository.resolvedRowCount)
+            assertEquals((99_975L..100_025L).toList(), window.map { it.position })
+            assertTrue(window.all { it.item.song.id == "s1" })
+        }
+
     @Test
     fun shuffledRangeResolvesEntriesInPositionOrder() =
         runTest {
@@ -851,6 +877,55 @@ class QueueRepositoryTest {
             }
         }
 
+    @Test
+    fun contextIndexUsesTheFirstDuplicateOrdinalAcrossSparsePositions() =
+        runTest {
+            seedLibrary()
+            db.libraryDao().upsertPlaylists(listOf(playlist("duplicates", "Duplicates")))
+            db.libraryDao().upsertPlaylistSongs(
+                listOf(
+                    PlaylistSong(1, "duplicates", "s2", 10),
+                    PlaylistSong(1, "duplicates", "s1", 20),
+                    PlaylistSong(1, "duplicates", "s2", 30),
+                ),
+            )
+            val snapshot = repository.snapshotAfter(listOf(repository.playlistEntry(1, "duplicates")))
+
+            assertEquals(0L, repository.combinedContextIndexOf(snapshot, "s2"))
+            assertEquals(1L, repository.combinedContextIndexOf(snapshot, "s1"))
+        }
+
+    @Test
+    fun contextIndexFindsADuplicateInsideTheEntryRange() =
+        runTest {
+            seedLibrary()
+            db.libraryDao().upsertPlaylists(listOf(playlist("duplicates", "Duplicates")))
+            db.libraryDao().upsertPlaylistSongs(
+                listOf(
+                    PlaylistSong(1, "duplicates", "s2", 10),
+                    PlaylistSong(1, "duplicates", "s1", 20),
+                    PlaylistSong(1, "duplicates", "s2", 30),
+                ),
+            )
+            val entry = repository.playlistEntry(1, "duplicates").copy(rangeStart = 1, rangeEnd = 2)
+            val snapshot = repository.snapshotAfter(listOf(entry))
+
+            assertEquals(1L, repository.combinedContextIndexOf(snapshot, "s2"))
+        }
+
+    @Test
+    fun contextIndexFallsBackToBoundedRowsForGenre() =
+        runTest {
+            seedLibrary()
+            insertGenre("s1", "Rock")
+            insertGenre("s3", "Rock")
+            insertGenre("s4", "Rock")
+            val snapshot = repository.snapshotAfter(listOf(repository.genreEntry(1, "Rock")))
+
+            assertEquals(2L, repository.combinedContextIndexOf(snapshot, "s4"))
+            assertTrue(repository.resolvedRowCount <= QUEUE_CHUNK)
+        }
+
     @Test
     fun upNextCombinedIndexOfCountsFromTheAnchorIntoTheBlock() =
         runTest {

app/src/test/kotlin/com/subtracks/playback/PlaybackControllerTest.kt

@@ -343,75 +343,18 @@ class PlaybackControllerTest {
     }
 
     @Test
-    fun restoringAPreviousQueuePreparesTheSessionWithoutPlaying() {
-        seedAlbum(3, sourceId = 1)
-        runBlocking { queues.replace(listOf(queues.albumEntry(1, "al1"))) }
-
-        controller.connect()
-        await { handle.operations.contains("prepare") }
-
-        assertFalse(handle.operations.contains("play"))
-        assertFalse(handle.isIdle)
-        assertFalse(handle.playWhenReady)
-        assertFalse(controller.state.value.isPlaying)
-    }
-
-    @Test
-    fun aPrepareFailureBeforePlaybackIsNotReported() {
-        seedAlbum(3, sourceId = 1)
-        runBlocking { queues.replace(listOf(queues.albumEntry(1, "al1"))) }
-
-        controller.connect()
-        await { handle.operations.contains("prepare") }
-
-        handle.fail(UiMessage(R.string.playback_error_network))
-        assertTrue(messages.isEmpty())
-
-        controller.togglePlayPause()
-        await { handle.operations.contains("play") }
-        handle.fail(UiMessage(R.string.playback_error_network))
-        await { messages.isNotEmpty() }
-
-        assertEquals(1, messages.size)
-    }
-
-    @Test
-    fun restoringAnEmptyQueueDoesNotPrepare() {
-        seedAlbum(3, sourceId = 1)
-
-        controller.connect()
-        await { controller.ready.value }
-
-        assertTrue(handle.items.isEmpty())
-        assertFalse(handle.operations.contains("prepare"))
-    }
-
-    @Test
-    fun restoringAnOfflineQueueWithoutDownloadsDoesNotPrepare() {
-        seedAlbum(3, sourceId = 1)
-        runBlocking { queues.replace(listOf(queues.albumEntry(1, "al1"))) }
-        setOffline()
-
-        controller.connect()
-        await { controller.ready.value }
-
-        assertTrue(handle.items.isEmpty())
-        assertFalse(handle.operations.contains("prepare"))
-    }
-
-    @Test
-    fun togglingPlayOnARestoredQueuePlaysThePreparedWindow() {
+    fun togglingPlayOnARestoredQueuePreparesBeforePlaying() {
         seedAlbum(5, sourceId = 1)
         runBlocking { queues.replace(listOf(queues.albumEntry(1, "al1"))) }
 
         controller.connect()
-        await { handle.operations.contains("prepare") }
+        await { handle.items.isNotEmpty() }
         handle.operations.clear()
 
         controller.togglePlayPause()
         await { handle.operations.contains("play") }
 
-        assertEquals(listOf("play"), handle.operations)
+        assertEquals(listOf("prepare", "play"), handle.operations)
     }
 
     @Test