add scaffold for ConstraintStreamSelector

new-player/src/main/java/net/newpipe/newplayer/NewPlayerImpl.kt

@@ -207,6 +207,7 @@ class NewPlayerImpl(
             }
 
             override fun onMediaItemTransition(mediaItem: MediaItem?, reason: Int) {
+                currentStreamLanguageConstraint = null
                 super.onMediaItemTransition(mediaItem, reason)
                 mutableCurrentlyPlaying.update { mediaItem }
                 if (mediaItem != null) {
@@ -418,6 +419,7 @@ class NewPlayerImpl(
 
     @OptIn(UnstableApi::class)
     private fun internalPlayStream(mediaSource: MediaSource, playMode: PlayMode) {
+        currentStreamLanguageConstraint = null
         if (exoPlayer.value?.playbackState == Player.STATE_IDLE || exoPlayer.value == null) {
             prepare()
         }
@@ -469,11 +471,11 @@ class NewPlayerImpl(
     private suspend
     fun toMediaSource(item: String): MediaSource {
         val autoStreamSelector = AutoStreamSelector(
-            preferredLanguages = preferredStreamLanguages
+            preferredLanguages = preferredStreamLanguages,
+            streamLanguageConstraint = currentStreamLanguageConstraint
         )
 
         val selection = autoStreamSelector.selectStreamAutomatically(
-            item,
             availableStreams = repository.getStreams(item),
         )
         return toMediaSource(selection, item)

new-player/src/main/java/net/newpipe/newplayer/logic/AutoStreamSelector.kt

@@ -31,14 +31,25 @@ import net.newpipe.newplayer.logic.TrackUtils.tryAndGetMedianAudioOnlyTracks
 import net.newpipe.newplayer.logic.TrackUtils.tryAndGetMedianCombinedVideoAndAudioTracks
 import net.newpipe.newplayer.logic.TrackUtils.tryAndGetMedianVideoOnlyTracks
 
+/**
+ * TODO: This whole class is just a concept. this should really be finished at some point.
+ */
 internal class AutoStreamSelector(
     /**
      * Must be in IETF-BCP-47 format
+     * This is a soft constraint. If no language can be found in the available tracks
+     * that fits on of the preferred languages, a default language is picked.
      */
     val preferredLanguages: List<String>,
+
+    /**
+     * This is a hard constraint. If not null a stream with this language must be selected,
+     * otherwise the automatic stream selection fails.
+     * Setting this will override the [preferredLanguages].
+     */
+    val streamLanguageConstraint: String?
 ) {
     internal fun selectStreamAutomatically(
-        item: String,
         availableStreams: List<Stream>,
     ): StreamSelection {
 
@@ -47,7 +58,8 @@ internal class AutoStreamSelector(
 
         val bestFittingLanguage =
             TrackUtils.getBestLanguageFit(availableStreams, preferredLanguages)
-        val availablesInPreferredLanguage =
+
+        val availableInPreferredLanguage =
             if (bestFittingLanguage != null) TrackUtils.filtersByLanguage(
                 availableStreams, bestFittingLanguage
             )
@@ -60,7 +72,7 @@ internal class AutoStreamSelector(
         if (hasVideoTracks(availableStreams)) {
 
             // first: try and get a dynamic stream variant
-            val dynamicStreams = getDynamicStreams(availablesInPreferredLanguage)
+            val dynamicStreams = getDynamicStreams(availableInPreferredLanguage)
             if (dynamicStreams.isNotEmpty()) {
                 return SingleSelection(dynamicStreams[0])
             }

new-player/src/main/java/net/newpipe/newplayer/logic/ConstraintStreamSelector.kt

@@ -0,0 +1,16 @@
+package net.newpipe.newplayer.logic
+
+import net.newpipe.newplayer.data.Stream
+import net.newpipe.newplayer.data.StreamSelection
+import net.newpipe.newplayer.data.StreamTrack
+
+internal object ConstraintStreamSelector {
+    fun selectStream(
+        availableStreams: List<Stream>,
+        currentStreamSelection: StreamSelection,
+        currentlyPlayingTracks: List<StreamTrack>
+    ): StreamSelection {
+
+        return currentStreamSelection
+    }
+}