playback: fix broken state restore

That didn't properly handle when the index was invalid and kept stale
song entries.

Resolves #723.

app/src/main/java/org/oxycblt/auxio/playback/service/PlaybackServiceFragment.kt

@@ -470,6 +470,10 @@ constructor(
         ack?.let { playbackManager.ack(this, it) }
     }
 
+    override fun reset() {
+        player.setMediaItems(emptyList())
+    }
+
     // --- PLAYER OVERRIDES ---
 
     override fun onPlayWhenReadyChanged(playWhenReady: Boolean, reason: Int) {

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateHolder.kt

@@ -153,6 +153,9 @@ interface PlaybackStateHolder {
      *   ack.
      */
     fun applySavedState(parent: MusicParent?, rawQueue: RawQueue, ack: StateAck.NewPlayback?)
+
+    /** Reset this instance to an empty state. */
+    fun reset()
 }
 
 /**

app/src/main/java/org/oxycblt/auxio/playback/state/PlaybackStateManager.kt

@@ -717,6 +717,8 @@ class PlaybackStateManagerImpl @Inject constructor() : PlaybackStateManager {
             return
         }
 
+        val stateHolder = stateHolder ?: return
+
         // The heap may not be the same if the song composition changed between state saves/reloads.
         // This also means that we must modify the shuffled mapping as well, in what it points to
         // and it's general composition.
@@ -763,27 +765,30 @@ class PlaybackStateManagerImpl @Inject constructor() : PlaybackStateManager {
             "Queue inconsistency detected: Shuffled mapping indices out of heap bounds"
         }
 
+        if (index < 0) {
+            stateHolder.reset()
+            return
+        }
+
         val rawQueue =
             RawQueue(
                 heap = heap,
                 shuffledMapping = shuffledMapping,
                 heapIndex =
                     if (shuffledMapping.isNotEmpty()) {
-                        shuffledMapping[savedState.index]
+                        shuffledMapping[index]
                     } else {
                         index
                     })
 
-        if (index > -1) {
-            // Valid state where something needs to be played, direct the stateholder to apply
-            // this new state.
-            val oldStateMirror = stateMirror
-            if (oldStateMirror.rawQueue != rawQueue) {
-                logD("Queue changed, must reload player")
-                stateHolder?.playing(false)
-                stateHolder?.applySavedState(parent, rawQueue, StateAck.NewPlayback)
-                stateHolder?.seekTo(savedState.positionMs)
-            }
+        // Valid state where something needs to be played, direct the stateholder to apply
+        // this new state.
+        val oldStateMirror = stateMirror
+        if (oldStateMirror.rawQueue != rawQueue) {
+            logD("Queue changed, must reload player")
+            stateHolder.playing(false)
+            stateHolder.applySavedState(parent, rawQueue, StateAck.NewPlayback)
+            stateHolder.seekTo(savedState.positionMs)
         }
 
         isInitialized = true