Clamp seeks to the seekable range. Closes #327

@@ -3,6 +3,7 @@ CHANGELOG
 
 ## HEAD (Unreleased)
 * @dmlap improved video duration calculation. ([view](https://github.com/videojs/videojs-contrib-hls/pull/321))
+* Clamp seeks to the seekable range ([view](https://github.com/videojs/videojs-contrib-hls/pull/327))
 
 --------------------
 

@@ -321,12 +321,21 @@ videojs.Hls.prototype.play = function() {
     this.mediaIndex = 0;
   }
 
-  // seek to the latest safe point in the media timeline when first
-  // playing live streams
-  if (this.duration() === Infinity &&
-      this.playlists.media() &&
-      !this.player().hasClass('vjs-has-started')) {
-    this.setCurrentTime(this.seekable().end(0));
+  // we may need to seek to begin playing safely for live playlists
+  if (this.duration() === Infinity) {
+
+    // if this is the first time we're playing the stream or we're
+    // ahead of the latest safe playback position, seek to the live
+    // point
+    if (!this.player().hasClass('vjs-has-started') ||
+        this.currentTime() > this.seekable().end(0)) {
+      this.setCurrentTime(this.seekable().end(0));
+
+    } else if (this.currentTime() < this.seekable().start(0)) {
+      // if the viewer has paused and we fell out of the live window,
+      // seek forward to the earliest available position
+      this.setCurrentTime(this.seekable().start(0));
+    }
   }
 
   // delegate back to the Flash implementation
@@ -356,6 +365,13 @@ videojs.Hls.prototype.setCurrentTime = function(currentTime) {
     return 0;
   }
 
+  // clamp seeks to the available seekable time range
+  if (currentTime < this.seekable().start(0)) {
+    currentTime = this.seekable().start(0);
+  } else if (currentTime > this.seekable().end(0)) {
+    currentTime = this.seekable().end(0);
+  }
+
   // save the seek target so currentTime can report it correctly
   // while the seek is pending
   this.lastSeekedTime_ = currentTime;

@@ -1686,6 +1686,87 @@ test('live playlist starts with correct currentTime value', function() {
               'currentTime is updated at playback');
 });
 
+test('resets the time to a seekable position when resuming a live stream ' +
+     'after a long break', function() {
+  var seekTarget;
+  player.src({
+    src: 'live0.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  openMediaSource(player);
+  requests.shift().respond(200, null,
+                           '#EXTM3U\n' +
+                           '#EXT-X-MEDIA-SEQUENCE:16\n' +
+                           '#EXTINF:10,\n' +
+                           '16.ts\n');
+  // mock out the player to simulate a live stream that has been
+  // playing for awhile
+  player.addClass('vjs-has-started');
+  player.hls.seekable = function() {
+    return {
+      start: function() {
+        return 160;
+      },
+      end: function() {
+        return 170;
+      }
+    };
+  };
+  player.hls.currentTime = function() {
+    return 0;
+  };
+  player.hls.setCurrentTime = function(time) {
+    if (time !== undefined) {
+      seekTarget = time;
+    }
+  };
+
+  player.play();
+  equal(seekTarget, player.seekable().start(0), 'seeked to the start of seekable');
+
+  player.hls.currentTime = function() {
+    return 180;
+  };
+  player.play();
+  equal(seekTarget, player.seekable().end(0), 'seeked to the end of seekable');
+});
+
+test('clamps seeks to the seekable window', function() {
+  var seekTarget;
+  player.src({
+    src: 'live0.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  openMediaSource(player);
+  requests.shift().respond(200, null,
+                           '#EXTM3U\n' +
+                           '#EXT-X-MEDIA-SEQUENCE:16\n' +
+                           '#EXTINF:10,\n' +
+                           '16.ts\n');
+  // mock out a seekable window
+  player.hls.seekable = function() {
+    return {
+      start: function() {
+        return 160;
+      },
+      end: function() {
+        return 170;
+      }
+    };
+  };
+  player.hls.fillBuffer = function(time) {
+    if (time !== undefined) {
+      seekTarget = time;
+    }
+  };
+
+  player.currentTime(180);
+  equal(seekTarget * 0.001, player.seekable().end(0), 'forward seeks are clamped');
+
+  player.currentTime(45);
+  equal(seekTarget * 0.001, player.seekable().start(0), 'backward seeks are clamped');
+});
+
 test('mediaIndex is zero before the first segment loads', function() {
   window.manifests['first-seg-load'] =
     '#EXTM3U\n' +