all: make callbacks initialize impls

Make addCallback calls (or similar) initalize the caller by calling the
specific callback methods.

This is primarily intended as a fix to an issue where the music library
would actually reload during a warm start. This is extremely bad, but I
hope it doesn't make the app too unusable until the next version.

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

@@ -54,6 +54,7 @@ class MusicStore private constructor() {
     private val callbacks = mutableListOf<Callback>()
 
     fun addCallback(callback: Callback) {
+        response?.let(callback::onMusicUpdate)
         callbacks.add(callback)
     }
 

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

@@ -43,7 +43,7 @@ class MusicViewModel : ViewModel(), MusicStore.Callback {
      * navigated to and because SnackBars will have the best UX here.
      */
     fun loadMusic(context: Context) {
-        if (musicStore.library != null || isBusy) {
+        if (_loaderResponse.value != null || isBusy) {
             logD("Loader is busy/already completed, not reloading")
             return
         }

app/src/main/java/org/oxycblt/auxio/playback/PlaybackViewModel.kt

@@ -83,18 +83,6 @@ class PlaybackViewModel : ViewModel(), PlaybackStateManager.Callback, MusicStore
     init {
         musicStore.addCallback(this)
         playbackManager.addCallback(this)
-
-        // If the PlaybackViewModel was cleared [Signified by PlaybackStateManager still being
-        // around & the fact that we are in the init function], then attempt to restore the
-        // ViewModel state. If it isn't, then wait for MainFragment to give the command to restore
-        // PlaybackStateManager.
-        if (playbackManager.isInitialized) {
-            onNewPlayback(playbackManager.index, playbackManager.queue, playbackManager.parent)
-            onPositionChanged(playbackManager.positionMs)
-            onPlayingChanged(playbackManager.isPlaying)
-            onShuffledChanged(playbackManager.isShuffled)
-            onRepeatChanged(playbackManager.repeatMode)
-        }
     }
 
     // --- PLAYING FUNCTIONS ---

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

@@ -96,6 +96,15 @@ class PlaybackStateManager private constructor() {
      * [removeCallback] when done.
      */
     fun addCallback(callback: Callback) {
+        if (isInitialized) {
+            callback.onNewPlayback(index, queue, parent)
+            callback.onSeek(positionMs)
+            callback.onPositionChanged(positionMs)
+            callback.onRepeatChanged(repeatMode)
+            callback.onShuffledChanged(isShuffled)
+            callback.onPlayingChanged(isPlaying)
+        }
+
         callbacks.add(callback)
     }
 

app/src/main/java/org/oxycblt/auxio/playback/system/MediaSessionComponent.kt

@@ -55,13 +55,6 @@ class MediaSessionComponent(private val context: Context, private val player: Pl
         playbackManager.addCallback(this)
         settingsManager.addCallback(this)
         mediaSession.setCallback(this)
-
-        if (playbackManager.isInitialized) {
-            updateMediaMetadata(playbackManager.song)
-            invalidateSessionState()
-            onRepeatChanged(playbackManager.repeatMode)
-            onShuffledChanged(playbackManager.isShuffled)
-        }
     }
 
     fun release() {

app/src/main/java/org/oxycblt/auxio/playback/system/PlaybackService.kt

@@ -139,13 +139,6 @@ class PlaybackService :
         // --- PLAYBACKSTATEMANAGER SETUP ---
 
         playbackManager.addCallback(this)
-        if (playbackManager.isInitialized) {
-            loadSong(playbackManager.song)
-            onSeek(playbackManager.positionMs)
-            onPlayingChanged(playbackManager.isPlaying)
-            onShuffledChanged(playbackManager.isShuffled)
-            onRepeatChanged(playbackManager.repeatMode)
-        }
 
         // --- SETTINGSMANAGER SETUP ---