Expose source indices via ExoPlayer (playlists #5).

ExoPlayer.EventListener.onPositionDiscontinuity is notified during seeking and
transitioning from one source to the next.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=125578976

demo/src/main/java/com/google/android/exoplayer/demo/EventLogger.java

@@ -72,6 +72,11 @@ public void onPlayerStateChanged(boolean playWhenReady, int state) {
         + getStateString(state) + "]");
   }
 
+  @Override
+  public void onPositionDiscontinuity(int sourceIndex, long positionMs) {
+    Log.d(TAG, "discontinuity [" + sourceIndex + ", " + positionMs + "]");
+  }
+
   @Override
   public void onPlayWhenReadyCommitted() {
     // Do nothing.

demo/src/main/java/com/google/android/exoplayer/demo/PlayerActivity.java

@@ -391,6 +391,14 @@ public void onPlayWhenReadyCommitted() {
     // Do nothing.
   }
 
+  @Override
+  public void onPositionDiscontinuity(int sourceIndex, long positionMs) {
+    if (mediaController.isShowing()) {
+      // The MediaController is visible, so force it to show the updated position immediately.
+      mediaController.show();
+    }
+  }
+
   @Override
   public void onPlayerError(ExoPlaybackException e) {
     String errorString = null;

extensions/flac/src/androidTest/java/com/google/android/exoplayer/ext/flac/FlacPlaybackTest.java

@@ -92,6 +92,11 @@ public void onPlayWhenReadyCommitted () {
       // Do nothing.
     }
 
+    @Override
+    public void onPositionDiscontinuity(int sourceIndex, long positionMs) {
+      // Do nothing.
+    }
+
     @Override
     public void onPlayerError(ExoPlaybackException error) {
       playbackException = error;

extensions/opus/src/androidTest/java/com/google/android/exoplayer/ext/opus/OpusPlaybackTest.java

@@ -92,6 +92,11 @@ public void onPlayWhenReadyCommitted () {
       // Do nothing.
     }
 
+    @Override
+    public void onPositionDiscontinuity(int sourceIndex, long positionMs) {
+      // Do nothing.
+    }
+
     @Override
     public void onPlayerError(ExoPlaybackException error) {
       playbackException = error;

extensions/vp9/src/androidTest/java/com/google/android/exoplayer/ext/vp9/VpxPlaybackTest.java

@@ -111,6 +111,11 @@ public void onPlayWhenReadyCommitted () {
       // Do nothing.
     }
 
+    @Override
+    public void onPositionDiscontinuity(int sourceIndex, long positionMs) {
+      // Do nothing.
+    }
+
     @Override
     public void onPlayerError(ExoPlaybackException error) {
       playbackException = error;

library/src/main/java/com/google/android/exoplayer/ExoPlayer.java

@@ -118,6 +118,16 @@ interface EventListener {
      */
     void onPlayWhenReadyCommitted();
 
+    // TODO[playlists]: Should source-initiated resets also cause this to be invoked?
+    /**
+     * Invoked when the player's position changes due to a discontinuity (seeking or playback
+     * transitioning to the next source).
+     *
+     * @param sourceIndex The index of the source being played.
+     * @param positionMs The playback position in that source, in milliseconds.
+     */
+    void onPositionDiscontinuity(int sourceIndex, long positionMs);
+
     /**
      * Invoked when an error occurs. The playback state will transition to
      * {@link ExoPlayer#STATE_IDLE} immediately after this method is invoked. The player instance
@@ -227,8 +237,9 @@ public ExoPlayerMessage(ExoPlayerComponent target, int messageType, Object messa
   void setSource(SampleSource sampleSource);
 
   /**
-   * Sets the player's source provider. The player will transition to {@link #STATE_BUFFERING} until
-   * it is ready to play the first source.
+   * Sets the player's source provider. The player's position will be reset to the start of the
+   * first source and the player will transition to {@link #STATE_BUFFERING} until it is ready to
+   * play it.
    *
    * @param sourceProvider The provider of {@link SampleSource}s to play.
    */
@@ -259,12 +270,20 @@ public ExoPlayerMessage(ExoPlayerComponent target, int messageType, Object messa
   boolean isPlayWhenReadyCommitted();
 
   /**
-   * Seeks to a position specified in milliseconds.
+   * Seeks to a position specified in milliseconds in the current source.
    *
    * @param positionMs The seek position.
    */
   void seekTo(long positionMs);
 
+  /**
+   * Seeks to a position specified in milliseconds in the specified source.
+   *
+   * @param sourceIndex The index of the source to seek to.
+   * @param positionMs The seek position relative to the start of the specified source.
+   */
+  void seekTo(int sourceIndex, long positionMs);
+
   /**
    * Stops playback. Use {@code setPlayWhenReady(false)} rather than this method if the intention
    * is to pause playback.
@@ -312,12 +331,19 @@ public ExoPlayerMessage(ExoPlayerComponent target, int messageType, Object messa
   long getDuration();
 
   /**
-   * Gets the current playback position in milliseconds.
+   * Gets the playback position in the current source, in milliseconds.
    *
-   * @return The current playback position in milliseconds.
+   * @return The playback position in the current source, in milliseconds.
    */
   long getCurrentPosition();
 
+  /**
+   * Gets the index of the current source.
+   *
+   * @return The index of the current source.
+   */
+  int getCurrentSourceIndex();
+
   /**
    * Gets an estimate of the absolute position in milliseconds up to which data is buffered.
    *

library/src/main/java/com/google/android/exoplayer/ExoPlayerImpl.java

@@ -39,6 +39,15 @@
   private boolean playWhenReady;
   private int playbackState;
   private int pendingPlayWhenReadyAcks;
+  private int pendingSetSourceProviderAndSeekAcks;
+
+  // Playback information when there is no pending seek/set source operation.
+  private ExoPlayerImplInternal.PlaybackInfo playbackInfo;
+
+  // Playback information when there is a pending seek/set source operation.
+  private int sourceIndex;
+  private long position;
+  private long duration;
 
   /**
    * Constructs an instance. Must be invoked from a thread that has an associated {@link Looper}.
@@ -68,6 +77,7 @@ public void handleMessage(Message msg) {
     };
     internalPlayer = new ExoPlayerImplInternal(renderers, trackSelector, minBufferMs, minRebufferMs,
         playWhenReady, eventHandler);
+    playbackInfo = new ExoPlayerImplInternal.PlaybackInfo(0);
   }
 
   @Override
@@ -87,12 +97,20 @@ public int getPlaybackState() {
 
   @Override
   public void setSource(final SampleSource sampleSource) {
-    internalPlayer.setSourceProvider(new SingleSampleSourceProvider(sampleSource));
+    setSourceProvider(new SingleSampleSourceProvider(sampleSource));
   }
 
   @Override
   public void setSourceProvider(SampleSourceProvider sourceProvider) {
+    duration = ExoPlayer.UNKNOWN_TIME;
+    position = 0;
+    sourceIndex = 0;
+
+    pendingSetSourceProviderAndSeekAcks++;
     internalPlayer.setSourceProvider(sourceProvider);
+    for (EventListener listener : listeners) {
+      listener.onPositionDiscontinuity(sourceIndex, position);
+    }
   }
 
   @Override
@@ -119,7 +137,20 @@ public boolean isPlayWhenReadyCommitted() {
 
   @Override
   public void seekTo(long positionMs) {
-    internalPlayer.seekTo(positionMs);
+    seekTo(getCurrentSourceIndex(), positionMs);
+  }
+
+  @Override
+  public void seekTo(int sourceIndex, long positionMs) {
+    duration = sourceIndex == getCurrentSourceIndex() ? getDuration() : ExoPlayer.UNKNOWN_TIME;
+    position = positionMs;
+    this.sourceIndex = sourceIndex;
+
+    pendingSetSourceProviderAndSeekAcks++;
+    internalPlayer.seekTo(sourceIndex, position);
+    for (EventListener listener : listeners) {
+      listener.onPositionDiscontinuity(sourceIndex, position);
+    }
   }
 
   @Override
@@ -145,17 +176,33 @@ public void blockingSendMessages(ExoPlayerMessage... messages) {
 
   @Override
   public long getDuration() {
-    return internalPlayer.getDuration();
+    if (pendingSetSourceProviderAndSeekAcks == 0) {
+      long durationUs = playbackInfo.durationUs;
+      return durationUs == C.UNSET_TIME_US ? ExoPlayer.UNKNOWN_TIME : durationUs / 1000;
+    } else {
+      return duration;
+    }
   }
 
   @Override
   public long getCurrentPosition() {
-    return internalPlayer.getCurrentPosition();
+    return pendingSetSourceProviderAndSeekAcks == 0 ? playbackInfo.positionUs / 1000 : position;
+  }
+
+  @Override
+  public int getCurrentSourceIndex() {
+    return pendingSetSourceProviderAndSeekAcks == 0 ? playbackInfo.sourceIndex : sourceIndex;
   }
 
   @Override
   public long getBufferedPosition() {
-    return internalPlayer.getBufferedPosition();
+    if (pendingSetSourceProviderAndSeekAcks == 0) {
+      long bufferedPositionUs = playbackInfo.bufferedPositionUs;
+      return bufferedPositionUs == C.UNSET_TIME_US || bufferedPositionUs == C.END_OF_SOURCE_US
+          ? ExoPlayer.UNKNOWN_TIME : bufferedPositionUs / 1000;
+    } else {
+      return position;
+    }
   }
 
   @Override
@@ -185,6 +232,20 @@ public int getBufferedPercentage() {
         }
         break;
       }
+      case ExoPlayerImplInternal.MSG_SET_SOURCE_PROVIDER_ACK: // Fall through.
+      case ExoPlayerImplInternal.MSG_SEEK_ACK: {
+        pendingSetSourceProviderAndSeekAcks--;
+        break;
+      }
+      case ExoPlayerImplInternal.MSG_SOURCE_CHANGED: {
+        playbackInfo = (ExoPlayerImplInternal.PlaybackInfo) msg.obj;
+        if (pendingSetSourceProviderAndSeekAcks == 0) {
+          for (EventListener listener : listeners) {
+            listener.onPositionDiscontinuity(playbackInfo.sourceIndex, 0);
+          }
+        }
+        break;
+      }
       case ExoPlayerImplInternal.MSG_ERROR: {
         ExoPlaybackException exception = (ExoPlaybackException) msg.obj;
         for (EventListener listener : listeners) {