Create MediaPeriods based on an identifier not an index

This will allow MediaSources to provide MediaPeriods that correspond to ad
breaks in a timeline period rather than content for a timeline period, in a
future change.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=160267841

extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsMediaSource.java

@@ -159,7 +159,8 @@ public final class ImaAdsMediaSource implements MediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+    int index = id.periodIndex;
     if (timeline.isPeriodAd(index)) {
       int adBreakIndex = timeline.getAdBreakIndex(index);
       int adIndexInAdBreak = timeline.getAdIndexInAdBreak(index);
@@ -174,13 +175,15 @@ public final class ImaAdsMediaSource implements MediaSource {
       }
 
       MediaSource adBreakMediaSource = adBreakMediaSources[adBreakIndex][adIndexInAdBreak];
-      MediaPeriod adBreakMediaPeriod = adBreakMediaSource.createPeriod(0, allocator);
+      MediaPeriod adBreakMediaPeriod =
+          adBreakMediaSource.createPeriod(new MediaPeriodId(0), allocator);
       mediaSourceByMediaPeriod.put(adBreakMediaPeriod, adBreakMediaSource);
       return adBreakMediaPeriod;
     } else {
       long startUs = timeline.getContentStartTimeUs(index);
       long endUs = timeline.getContentEndTimeUs(index);
-      MediaPeriod contentMediaPeriod = contentMediaSource.createPeriod(0, allocator);
+      MediaPeriod contentMediaPeriod =
+          contentMediaSource.createPeriod(new MediaPeriodId(0), allocator);
       ClippingMediaPeriod clippingPeriod = new ClippingMediaPeriod(contentMediaPeriod, true);
       clippingPeriod.setClipping(startUs, endUs == C.TIME_UNSET ? C.TIME_END_OF_SOURCE : endUs);
       mediaSourceByMediaPeriod.put(contentMediaPeriod, contentMediaSource);
@@ -445,7 +448,7 @@ public final class ImaAdsMediaSource implements MediaSource {
     }
 
     public void setMediaSource(MediaSource mediaSource) {
-      mediaPeriod = mediaSource.createPeriod(index, allocator);
+      mediaPeriod = mediaSource.createPeriod(new MediaPeriodId(index), allocator);
       if (callback != null) {
         mediaPeriod.prepare(this, positionUs);
       }

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

@@ -535,8 +535,8 @@ public final class ExoPlayerTest extends TestCase {
     }
 
     @Override
-    public MediaPeriod createPeriod(int index, Allocator allocator) {
-      Assertions.checkIndex(index, 0, timeline.getPeriodCount());
+    public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+      Assertions.checkIndex(id.periodIndex, 0, timeline.getPeriodCount());
       assertTrue(preparedSource);
       assertFalse(releasedSource);
       FakeMediaPeriod mediaPeriod = new FakeMediaPeriod(trackGroupArray);

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

@@ -98,7 +98,7 @@ public class TimelineTest extends TestCase {
     }
 
     @Override
-    public MediaPeriod createPeriod(int index, Allocator allocator) {
+    public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
       return null;
     }
 

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

@@ -26,6 +26,7 @@ import android.util.Pair;
 import com.google.android.exoplayer2.ExoPlayer.ExoPlayerMessage;
 import com.google.android.exoplayer2.source.MediaPeriod;
 import com.google.android.exoplayer2.source.MediaSource;
+import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
 import com.google.android.exoplayer2.source.SampleStream;
 import com.google.android.exoplayer2.trackselection.TrackSelection;
 import com.google.android.exoplayer2.trackselection.TrackSelectionArray;
@@ -1543,7 +1544,8 @@ import java.io.IOException;
       this.startPositionUs = startPositionUs;
       sampleStreams = new SampleStream[renderers.length];
       mayRetainStreamFlags = new boolean[renderers.length];
-      mediaPeriod = mediaSource.createPeriod(periodIndex, loadControl.getAllocator());
+      mediaPeriod = mediaSource.createPeriod(new MediaPeriodId(periodIndex),
+          loadControl.getAllocator());
     }
 
     public long toRendererTime(long periodTimeUs) {

library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java

@@ -91,9 +91,9 @@ public final class ClippingMediaSource implements MediaSource, MediaSource.Liste
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
     ClippingMediaPeriod mediaPeriod = new ClippingMediaPeriod(
-        mediaSource.createPeriod(index, allocator), enableInitialDiscontinuity);
+        mediaSource.createPeriod(id, allocator), enableInitialDiscontinuity);
     mediaPeriods.add(mediaPeriod);
     mediaPeriod.setClipping(clippingTimeline.startUs, clippingTimeline.endUs);
     return mediaPeriod;

library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java

@@ -91,11 +91,11 @@ public final class ConcatenatingMediaSource implements MediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
-    int sourceIndex = timeline.getChildIndexByPeriodIndex(index);
-    int periodIndexInSource = index - timeline.getFirstPeriodIndexInChild(sourceIndex);
-    MediaPeriod mediaPeriod =
-        mediaSources[sourceIndex].createPeriod(periodIndexInSource, allocator);
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+    int sourceIndex = timeline.getChildIndexByPeriodIndex(id.periodIndex);
+    MediaPeriodId periodIdInSource =
+        new MediaPeriodId(id.periodIndex - timeline.getFirstPeriodIndexInChild(sourceIndex));
+    MediaPeriod mediaPeriod = mediaSources[sourceIndex].createPeriod(periodIdInSource, allocator);
     sourceIndexByMediaPeriod.put(mediaPeriod, sourceIndex);
     return mediaPeriod;
   }

library/core/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java

@@ -165,8 +165,8 @@ public final class ExtractorMediaSource implements MediaSource, MediaSource.List
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
-    Assertions.checkArgument(index == 0);
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+    Assertions.checkArgument(id.periodIndex == 0);
     return new ExtractorMediaPeriod(uri, dataSourceFactory.createDataSource(),
         extractorsFactory.createExtractors(), minLoadableRetryCount, eventHandler, eventListener,
         this, allocator, customCacheKey, continueLoadingCheckIntervalBytes);

library/core/src/main/java/com/google/android/exoplayer2/source/LoopingMediaSource.java

@@ -76,10 +76,10 @@ public final class LoopingMediaSource implements MediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
     return loopCount != Integer.MAX_VALUE
-        ? childSource.createPeriod(index % childPeriodCount, allocator)
-        : childSource.createPeriod(index, allocator);
+        ? childSource.createPeriod(new MediaPeriodId(id.periodIndex % childPeriodCount), allocator)
+        : childSource.createPeriod(id, allocator);
   }
 
   @Override

library/core/src/main/java/com/google/android/exoplayer2/source/MediaSource.java

@@ -41,6 +41,27 @@ public interface MediaSource {
 
   }
 
+  /**
+   * Identifier for a {@link MediaPeriod}.
+   */
+  final class MediaPeriodId {
+
+    /**
+     * The timeline period index.
+     */
+    public final int periodIndex;
+
+    /**
+     * Creates a media period identifier for the specified period in the timeline.
+     *
+     * @param periodIndex The timeline period index.
+     */
+    public MediaPeriodId(int periodIndex) {
+      this.periodIndex = periodIndex;
+    }
+
+  }
+
   /**
    * Starts preparation of the source.
    *
@@ -59,15 +80,15 @@ public interface MediaSource {
   void maybeThrowSourceInfoRefreshError() throws IOException;
 
   /**
-   * Returns a new {@link MediaPeriod} corresponding to the period at the specified {@code index}.
-   * This method may be called multiple times with the same index without an intervening call to
+   * Returns a new {@link MediaPeriod} identified by {@code periodId}. This method may be called
+   * multiple times with the same period identifier without an intervening call to
    * {@link #releasePeriod(MediaPeriod)}.
    *
-   * @param index The index of the period.
+   * @param id The identifier of the period.
    * @param allocator An {@link Allocator} from which to obtain media buffer allocations.
    * @return A new {@link MediaPeriod}.
    */
-  MediaPeriod createPeriod(int index, Allocator allocator);
+  MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator);
 
   /**
    * Releases the period.

library/core/src/main/java/com/google/android/exoplayer2/source/MergingMediaSource.java

@@ -116,10 +116,10 @@ public final class MergingMediaSource implements MediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
     MediaPeriod[] periods = new MediaPeriod[mediaSources.length];
     for (int i = 0; i < periods.length; i++) {
-      periods[i] = mediaSources[i].createPeriod(index, allocator);
+      periods[i] = mediaSources[i].createPeriod(id, allocator);
     }
     return new MergingMediaPeriod(periods);
   }

library/core/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java

@@ -95,8 +95,8 @@ public final class SingleSampleMediaSource implements MediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
-    Assertions.checkArgument(index == 0);
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+    Assertions.checkArgument(id.periodIndex == 0);
     return new SingleSampleMediaPeriod(uri, dataSourceFactory, format, minLoadableRetryCount,
         eventHandler, eventListener, eventSourceId);
   }

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java

@@ -281,7 +281,8 @@ public final class DashMediaSource implements MediaSource {
   }
 
   @Override
-  public MediaPeriod createPeriod(int periodIndex, Allocator allocator) {
+  public MediaPeriod createPeriod(MediaPeriodId periodId, Allocator allocator) {
+    int periodIndex = periodId.periodIndex;
     EventDispatcher periodEventDispatcher = eventDispatcher.copyWithMediaTimeOffsetMs(
         manifest.getPeriod(periodIndex).startMs);
     DashMediaPeriod mediaPeriod = new DashMediaPeriod(firstPeriodId + periodIndex, manifest,

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java

@@ -88,8 +88,8 @@ public final class HlsMediaSource implements MediaSource,
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
-    Assertions.checkArgument(index == 0);
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+    Assertions.checkArgument(id.periodIndex == 0);
     return new HlsMediaPeriod(playlistTracker, dataSourceFactory, minLoadableRetryCount,
         eventDispatcher, allocator);
   }

library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java

@@ -222,8 +222,8 @@ public final class SsMediaSource implements MediaSource,
   }
 
   @Override
-  public MediaPeriod createPeriod(int index, Allocator allocator) {
-    Assertions.checkArgument(index == 0);
+  public MediaPeriod createPeriod(MediaPeriodId id, Allocator allocator) {
+    Assertions.checkArgument(id.periodIndex == 0);
     SsMediaPeriod period = new SsMediaPeriod(manifest, chunkSourceFactory, minLoadableRetryCount,
         eventDispatcher, manifestLoaderErrorThrower, allocator);
     mediaPeriods.add(period);