From a526d3fafd1ec2456d3ed817c54589b528810787 Mon Sep 17 00:00:00 2001
From: tonihei <tonihei@google.com>
Date: Thu, 8 Mar 2018 09:02:11 -0800
Subject: [PATCH] Keep window sequence number of playing period if queue is
 cleared.

This allows to keep the same window sequence number if playback fails and
is then retried without resetting the position.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188339509
---
 .../exoplayer2/ExoPlayerImplInternal.java     |  4 +--
 .../android/exoplayer2/MediaPeriodQueue.java  | 28 +++++++++++++++++--
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
index 1305348b6f..9f3b0bed5b 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java
@@ -691,7 +691,7 @@ import java.util.Collections;
       resetRendererPosition(periodPositionUs);
       maybeContinueLoading();
     } else {
-      queue.clear();
+      queue.clear(/* keepFrontPeriodUid= */ true);
       resetRendererPosition(periodPositionUs);
     }
 
@@ -776,7 +776,7 @@ import java.util.Collections;
       }
     }
     enabledRenderers = new Renderer[0];
-    queue.clear();
+    queue.clear(/* keepFrontPeriodUid= */ !resetPosition);
     setIsLoading(false);
     if (resetPosition) {
       pendingInitialSeekPosition = null;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java b/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java
index 3efff58f5d..dde3e67635 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/MediaPeriodQueue.java
@@ -52,6 +52,8 @@ import com.google.android.exoplayer2.util.Assertions;
   private MediaPeriodHolder reading;
   private MediaPeriodHolder loading;
   private int length;
+  private Object oldFrontPeriodUid;
+  private long oldFrontPeriodWindowSequenceNumber;
 
   /** Creates a new media period queue. */
   public MediaPeriodQueue() {
@@ -162,6 +164,7 @@ import com.google.android.exoplayer2.util.Assertions;
       Assertions.checkState(hasPlayingPeriod());
       loading.next = newPeriodHolder;
     }
+    oldFrontPeriodUid = null;
     loading = newPeriodHolder;
     length++;
     return newPeriodHolder.mediaPeriod;
@@ -276,12 +279,21 @@ import com.google.android.exoplayer2.util.Assertions;
     return removedReading;
   }
 
-  /** Clears the queue. */
-  public void clear() {
+  /**
+   * Clears the queue.
+   *
+   * @param keepFrontPeriodUid Whether the queue should keep the id of the media period in the front
+   *     of queue (typically the playing one) for later reuse.
+   */
+  public void clear(boolean keepFrontPeriodUid) {
     MediaPeriodHolder front = getFrontPeriod();
     if (front != null) {
+      oldFrontPeriodUid = keepFrontPeriodUid ? front.uid : null;
+      oldFrontPeriodWindowSequenceNumber = front.info.id.windowSequenceNumber;
       front.release();
       removeAfter(front);
+    } else if (!keepFrontPeriodUid) {
+      oldFrontPeriodUid = null;
     }
     playing = null;
     loading = null;
@@ -408,6 +420,17 @@ import com.google.android.exoplayer2.util.Assertions;
    */
   private long resolvePeriodIndexToWindowSequenceNumber(int periodIndex) {
     Object periodUid = timeline.getPeriod(periodIndex, period, /* setIds= */ true).uid;
+    int windowIndex = period.windowIndex;
+    if (oldFrontPeriodUid != null) {
+      int oldFrontPeriodIndex = timeline.getIndexOfPeriod(oldFrontPeriodUid);
+      if (oldFrontPeriodIndex != C.INDEX_UNSET) {
+        int oldFrontWindowIndex = timeline.getPeriod(oldFrontPeriodIndex, period).windowIndex;
+        if (oldFrontWindowIndex == windowIndex) {
+          // Try to match old front uid after the queue has been cleared.
+          return oldFrontPeriodWindowSequenceNumber;
+        }
+      }
+    }
     MediaPeriodHolder mediaPeriodHolder = getFrontPeriod();
     while (mediaPeriodHolder != null) {
       if (mediaPeriodHolder.uid.equals(periodUid)) {
@@ -416,7 +439,6 @@ import com.google.android.exoplayer2.util.Assertions;
       }
       mediaPeriodHolder = mediaPeriodHolder.next;
     }
-    int windowIndex = period.windowIndex;
     mediaPeriodHolder = getFrontPeriod();
     while (mediaPeriodHolder != null) {
       int indexOfHolderInTimeline = timeline.getIndexOfPeriod(mediaPeriodHolder.uid);