Fix masking step 1

1. Move Timeline/Manifest into PlaybackInfo
2. Don't update externally visible Timeline/Manifest during preparation
3. Ignore MSG_POSITION_DISCONTINUITY during preparation
4. Correctly set masking variables at start of preparation, and use them

Once this change goes in, PlaybackInfo will contain timeline, manifest
and position, which should always be self-consistent with one another.
The next step would then be to move a bunch of logic in ExoPlayerImpl
that derives state from timeline and position into PlaybackInfo, and
split that into its own top level class that can be easily tested to make
sure it never IndexOutOfBounds.

I think we could also replace the masking variables and instead just assign
a new PlaybackInfo to the playbackInfo variable whenever we're doing
something that requires masking. This should be possible because we no
longer update playbackInfo whenever we have pending acks. It would
require allowing PlaybackInfo to mask the window position internally when
the timeline is empty, but I think this is ok, and again is something we
could test pretty easily.

Issue: #3362

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=173909791

library/core/src/androidTest/java/com/google/android/exoplayer2/ExoPlayerTest.java

@@ -56,7 +56,7 @@ public final class ExoPlayerTest extends TestCase {
         .setTimeline(timeline).setRenderers(renderer)
         .build().start().blockUntilEnded(TIMEOUT_MS);
     testRunner.assertPositionDiscontinuityCount(0);
-    testRunner.assertTimelinesEqual(timeline);
+    testRunner.assertTimelinesEqual();
     assertEquals(0, renderer.formatReadCount);
     assertEquals(0, renderer.bufferReadCount);
     assertFalse(renderer.isEnded);

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java

@@ -22,7 +22,6 @@ import android.os.Message;
 import android.support.annotation.Nullable;
 import android.util.Log;
 import com.google.android.exoplayer2.ExoPlayerImplInternal.PlaybackInfo;
-import com.google.android.exoplayer2.ExoPlayerImplInternal.SourceInfo;
 import com.google.android.exoplayer2.source.MediaSource;
 import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
 import com.google.android.exoplayer2.source.TrackGroupArray;
@@ -105,9 +104,9 @@ import java.util.concurrent.CopyOnWriteArraySet;
         ExoPlayerImpl.this.handleEvent(msg);
       }
     };
-    playbackInfo = new ExoPlayerImplInternal.PlaybackInfo(0, 0);
+    playbackInfo = new ExoPlayerImplInternal.PlaybackInfo(timeline, manifest, 0, 0);
     internalPlayer = new ExoPlayerImplInternal(renderers, trackSelector, loadControl, playWhenReady,
-        repeatMode, shuffleModeEnabled, eventHandler, playbackInfo, this);
+        repeatMode, shuffleModeEnabled, eventHandler, this);
   }
 
   @Override
@@ -137,6 +136,15 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public void prepare(MediaSource mediaSource, boolean resetPosition, boolean resetState) {
+    if (!resetPosition) {
+      maskingWindowIndex = getCurrentWindowIndex();
+      maskingPeriodIndex = getCurrentPeriodIndex();
+      maskingWindowPositionMs = getCurrentPosition();
+    } else {
+      maskingWindowIndex = 0;
+      maskingPeriodIndex = 0;
+      maskingWindowPositionMs = 0;
+    }
     if (resetState) {
       if (!timeline.isEmpty() || manifest != null) {
         timeline = Timeline.EMPTY;
@@ -263,6 +271,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
       maskingPeriodIndex = periodIndex;
     }
     if (positionMs == C.TIME_UNSET) {
+      // TODO: Work out when to call onPositionDiscontinuity on listeners for this case.
       maskingWindowPositionMs = 0;
       internalPlayer.seekTo(timeline, windowIndex, C.TIME_UNSET);
     } else {
@@ -313,7 +322,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public int getCurrentPeriodIndex() {
-    if (timeline.isEmpty() || pendingSeekAcks > 0) {
+    if (shouldMaskPosition()) {
       return maskingPeriodIndex;
     } else {
       return playbackInfo.periodId.periodIndex;
@@ -322,7 +331,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public int getCurrentWindowIndex() {
-    if (timeline.isEmpty() || pendingSeekAcks > 0) {
+    if (shouldMaskPosition()) {
       return maskingWindowIndex;
     } else {
       return timeline.getPeriod(playbackInfo.periodId.periodIndex, period).windowIndex;
@@ -358,7 +367,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public long getCurrentPosition() {
-    if (timeline.isEmpty() || pendingSeekAcks > 0) {
+    if (shouldMaskPosition()) {
       return maskingWindowPositionMs;
     } else {
       return playbackInfoPositionUsToWindowPositionMs(playbackInfo.positionUs);
@@ -368,7 +377,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
   @Override
   public long getBufferedPosition() {
     // TODO - Implement this properly.
-    if (timeline.isEmpty() || pendingSeekAcks > 0) {
+    if (shouldMaskPosition()) {
       return maskingWindowPositionMs;
     } else {
       return playbackInfoPositionUsToWindowPositionMs(playbackInfo.bufferedPositionUs);
@@ -398,7 +407,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 
   @Override
   public boolean isPlayingAd() {
-    return !timeline.isEmpty() && pendingSeekAcks == 0 && playbackInfo.periodId.isAd();
+    return !shouldMaskPosition() && playbackInfo.periodId.isAd();
   }
 
   @Override
@@ -469,28 +478,9 @@ import java.util.concurrent.CopyOnWriteArraySet;
         break;
       }
       case ExoPlayerImplInternal.MSG_SOURCE_INFO_REFRESHED: {
-        SourceInfo sourceInfo = (SourceInfo) msg.obj;
-        pendingPrepareAcks -= sourceInfo.prepareAcks;
-        pendingSeekAcks -= sourceInfo.seekAcks;
-        if (pendingPrepareAcks == 0) {
-          timeline = sourceInfo.timeline;
-          manifest = sourceInfo.manifest;
-          playbackInfo = sourceInfo.playbackInfo;
-          if (pendingSeekAcks == 0 && timeline.isEmpty()) {
-            // Update the masking variables, which are used when the timeline is empty.
-            maskingPeriodIndex = 0;
-            maskingWindowIndex = 0;
-            maskingWindowPositionMs = 0;
-          }
-          for (Player.EventListener listener : listeners) {
-            listener.onTimelineChanged(timeline, manifest);
-          }
-        }
-        if (pendingSeekAcks == 0 && sourceInfo.seekAcks > 0) {
-          for (Player.EventListener listener : listeners) {
-            listener.onSeekProcessed();
-          }
-        }
+        int prepareAcks = msg.arg1;
+        int seekAcks = msg.arg2;
+        handlePlaybackInfo((PlaybackInfo) msg.obj, prepareAcks, seekAcks, false);
         break;
       }
       case ExoPlayerImplInternal.MSG_TRACKS_CHANGED: {
@@ -507,30 +497,12 @@ import java.util.concurrent.CopyOnWriteArraySet;
         break;
       }
       case ExoPlayerImplInternal.MSG_SEEK_ACK: {
-        if (--pendingSeekAcks == 0) {
-          playbackInfo = (ExoPlayerImplInternal.PlaybackInfo) msg.obj;
-          if (timeline.isEmpty()) {
-            // Update the masking variables, which are used when the timeline is empty.
-            maskingPeriodIndex = 0;
-            maskingWindowIndex = 0;
-            maskingWindowPositionMs = 0;
-          }
-          for (Player.EventListener listener : listeners) {
-            if (msg.arg1 != 0) {
-              listener.onPositionDiscontinuity(DISCONTINUITY_REASON_INTERNAL);
-            }
-            listener.onSeekProcessed();
-          }
-        }
+        boolean seekPositionAdjusted = msg.arg1 != 0;
+        handlePlaybackInfo((PlaybackInfo) msg.obj, 0, 1, seekPositionAdjusted);
         break;
       }
       case ExoPlayerImplInternal.MSG_POSITION_DISCONTINUITY: {
-        if (pendingSeekAcks == 0) {
-          playbackInfo = (ExoPlayerImplInternal.PlaybackInfo) msg.obj;
-          for (Player.EventListener listener : listeners) {
-            listener.onPositionDiscontinuity(DISCONTINUITY_REASON_PERIOD_TRANSITION);
-          }
-        }
+        handlePlaybackInfo((PlaybackInfo) msg.obj, 0, 0, true);
         break;
       }
       case ExoPlayerImplInternal.MSG_PLAYBACK_PARAMETERS_CHANGED: {
@@ -555,6 +527,43 @@ import java.util.concurrent.CopyOnWriteArraySet;
     }
   }
 
+  private void handlePlaybackInfo(PlaybackInfo playbackInfo, int prepareAcks, int seekAcks,
+      boolean positionDiscontinuity) {
+    Assertions.checkNotNull(playbackInfo.timeline);
+    pendingPrepareAcks -= prepareAcks;
+    pendingSeekAcks -= seekAcks;
+    if (pendingPrepareAcks == 0 && pendingSeekAcks == 0) {
+      this.playbackInfo = playbackInfo;
+      boolean timelineOrManifestChanged = timeline != playbackInfo.timeline
+          || manifest != playbackInfo.manifest;
+      timeline = playbackInfo.timeline;
+      manifest = playbackInfo.manifest;
+      if (timeline.isEmpty()) {
+        // Update the masking variables, which are used when the timeline is empty.
+        maskingPeriodIndex = 0;
+        maskingWindowIndex = 0;
+        maskingWindowPositionMs = 0;
+      }
+      if (timelineOrManifestChanged) {
+        for (Player.EventListener listener : listeners) {
+          listener.onTimelineChanged(timeline, manifest);
+        }
+      }
+      if (positionDiscontinuity) {
+        for (Player.EventListener listener : listeners) {
+          listener.onPositionDiscontinuity(
+              seekAcks > 0 ? DISCONTINUITY_REASON_INTERNAL : DISCONTINUITY_REASON_PERIOD_TRANSITION
+          );
+        }
+      }
+    }
+    if (pendingSeekAcks == 0 && seekAcks > 0) {
+      for (Player.EventListener listener : listeners) {
+        listener.onSeekProcessed();
+      }
+    }
+  }
+
   private long playbackInfoPositionUsToWindowPositionMs(long positionUs) {
     long positionMs = C.usToMs(positionUs);
     if (!playbackInfo.periodId.isAd()) {
@@ -564,4 +573,8 @@ import java.util.concurrent.CopyOnWriteArraySet;
     return positionMs;
   }
 
+  private boolean shouldMaskPosition() {
+    return timeline.isEmpty() || pendingSeekAcks > 0 || pendingPrepareAcks > 0;
+  }
+
 }