From c49d142981ae1498840d6cd2b4f5be4461f037a3 Mon Sep 17 00:00:00 2001
From: aquilescanta <aquilescanta@google.com>
Date: Thu, 26 Jan 2017 08:55:42 -0800
Subject: [PATCH] Prevent old playlist snapshots from being used on live HLS
 streams

This aims to replace InvalidCodeResponse's with BLWE's caused by trying to
load chunks that have been removed from the server.

Issue:#2344

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=145679171
---
 .../exoplayer2/source/hls/HlsChunkSource.java | 22 +++++++------
 .../hls/playlist/HlsPlaylistTracker.java      | 33 +++++++++++++++++--
 2 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsChunkSource.java b/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsChunkSource.java
index c2a345ace6..c7c66fbd61 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsChunkSource.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/hls/HlsChunkSource.java
@@ -194,15 +194,16 @@ import java.util.Locale;
 
     // Select the variant.
     trackSelection.updateSelectedTrack(bufferedDurationUs);
-    int newVariantIndex = trackSelection.getSelectedIndexInTrackGroup();
+    int selectedVariantIndex = trackSelection.getSelectedIndexInTrackGroup();
 
-    boolean switchingVariant = oldVariantIndex != newVariantIndex;
-    HlsMediaPlaylist mediaPlaylist = playlistTracker.getPlaylistSnapshot(variants[newVariantIndex]);
-    if (mediaPlaylist == null) {
-      out.playlist = variants[newVariantIndex];
+    boolean switchingVariant = oldVariantIndex != selectedVariantIndex;
+    HlsUrl selectedUrl = variants[selectedVariantIndex];
+    if (!playlistTracker.isSnapshotValid(selectedUrl)) {
+      out.playlist = selectedUrl;
       // Retry when playlist is refreshed.
       return;
     }
+    HlsMediaPlaylist mediaPlaylist = playlistTracker.getPlaylistSnapshot(selectedUrl);
 
     // Select the chunk.
     int chunkMediaSequence;
@@ -218,8 +219,9 @@ import java.util.Locale;
         if (chunkMediaSequence < mediaPlaylist.mediaSequence && previous != null) {
           // We try getting the next chunk without adapting in case that's the reason for falling
           // behind the live window.
-          newVariantIndex = oldVariantIndex;
-          mediaPlaylist = playlistTracker.getPlaylistSnapshot(variants[newVariantIndex]);
+          selectedVariantIndex = oldVariantIndex;
+          selectedUrl = variants[selectedVariantIndex];
+          mediaPlaylist = playlistTracker.getPlaylistSnapshot(selectedUrl);
           chunkMediaSequence = previous.getNextChunkIndex();
         }
       }
@@ -236,7 +238,7 @@ import java.util.Locale;
       if (mediaPlaylist.hasEndTag) {
         out.endOfStream = true;
       } else /* Live */ {
-        out.playlist = variants[newVariantIndex];
+        out.playlist = selectedUrl;
       }
       return;
     }
@@ -249,7 +251,7 @@ import java.util.Locale;
       Uri keyUri = UriUtil.resolveToUri(mediaPlaylist.baseUri, segment.encryptionKeyUri);
       if (!keyUri.equals(encryptionKeyUri)) {
         // Encryption is specified and the key has changed.
-        out.chunk = newEncryptionKeyChunk(keyUri, segment.encryptionIV, newVariantIndex,
+        out.chunk = newEncryptionKeyChunk(keyUri, segment.encryptionIV, selectedVariantIndex,
             trackSelection.getSelectionReason(), trackSelection.getSelectionData());
         return;
       }
@@ -279,7 +281,7 @@ import java.util.Locale;
     Uri chunkUri = UriUtil.resolveToUri(mediaPlaylist.baseUri, segment.url);
     DataSpec dataSpec = new DataSpec(chunkUri, segment.byterangeOffset, segment.byterangeLength,
         null);
-    out.chunk = new HlsMediaChunk(dataSource, dataSpec, initDataSpec, variants[newVariantIndex],
+    out.chunk = new HlsMediaChunk(dataSource, dataSpec, initDataSpec, selectedUrl,
         trackSelection.getSelectionReason(), trackSelection.getSelectionData(),
         startTimeUs, startTimeUs + segment.durationUs, chunkMediaSequence, discontinuitySequence,
         isTimestampMaster, timestampAdjuster, previous, encryptionKey, encryptionIv);
diff --git a/library/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistTracker.java b/library/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistTracker.java
index 92e2480da7..95784092a9 100644
--- a/library/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistTracker.java
+++ b/library/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistTracker.java
@@ -166,8 +166,24 @@ public final class HlsPlaylistTracker implements Loader.Callback<ParsingLoadable
    *     be null if no snapshot has been loaded yet.
    */
   public HlsMediaPlaylist getPlaylistSnapshot(HlsUrl url) {
-    maybeSetPrimaryUrl(url);
-    return playlistBundles.get(url).getPlaylistSnapshot();
+    HlsMediaPlaylist snapshot = playlistBundles.get(url).getPlaylistSnapshot();
+    if (snapshot != null) {
+      maybeSetPrimaryUrl(url);
+    }
+    return snapshot;
+  }
+
+  /**
+   * Returns whether the snapshot of the playlist referenced by the provided {@link HlsUrl} is
+   * valid, meaning all the segments referenced by the playlist are expected to be available. If the
+   * playlist is not valid then some of the segments may no longer be available.
+
+   * @param url The {@link HlsUrl}.
+   * @return Whether the snapshot of the playlist referenced by the provided {@link HlsUrl} is
+   *     valid.
+   */
+  public boolean isSnapshotValid(HlsUrl url) {
+    return playlistBundles.get(url).isSnapshotValid();
   }
 
   /**
@@ -412,6 +428,7 @@ public final class HlsPlaylistTracker implements Loader.Callback<ParsingLoadable
     private final ParsingLoadable<HlsPlaylist> mediaPlaylistLoadable;
 
     private HlsMediaPlaylist playlistSnapshot;
+    private long lastSnapshotLoadMs;
     private long lastSnapshotAccessTimeMs;
     private long blacklistUntilMs;
 
@@ -429,6 +446,17 @@ public final class HlsPlaylistTracker implements Loader.Callback<ParsingLoadable
       return playlistSnapshot;
     }
 
+    public boolean isSnapshotValid() {
+      if (playlistSnapshot == null) {
+        return false;
+      }
+      // TODO: Return true for event playlists once playlist types are supported.
+      long currentTimeMs = SystemClock.elapsedRealtime();
+      long snapshotValidityDurationMs = Math.max(30000, C.usToMs(playlistSnapshot.durationUs));
+      return playlistSnapshot.hasEndTag
+          || lastSnapshotLoadMs + snapshotValidityDurationMs > currentTimeMs;
+    }
+
     public void release() {
       mediaPlaylistLoader.release();
     }
@@ -488,6 +516,7 @@ public final class HlsPlaylistTracker implements Loader.Callback<ParsingLoadable
 
     private void processLoadedPlaylist(HlsMediaPlaylist loadedPlaylist) {
       HlsMediaPlaylist oldPlaylist = playlistSnapshot;
+      lastSnapshotLoadMs = SystemClock.elapsedRealtime();
       playlistSnapshot = getLatestPlaylistSnapshot(oldPlaylist, loadedPlaylist);
       long refreshDelayUs = C.TIME_UNSET;
       if (playlistSnapshot != oldPlaylist) {