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gaia/apps/video/js/captions.js

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+(function(exports) {
+  'use strict';
+
+  function Captions(player) {
+    this.player = player;
+  }
+
+  //
+  // Remove all <track> elements from the <video> element
+  //
+  Captions.prototype.remove = function() {
+    for(var track of this.player.querySelectorAll('track')) {
+      if (track.src && track.src.startsWith('blob:')) {
+        URL.revokeObjectURL(track.src);
+      }
+      track.remove();
+    }
+  };
+
+  //
+  // Given the path of a video file, look in the same directory for a
+  // file of captions or subtitles for that video. If we find one, set
+  // it on the <track> element of the player to display the captions.
+  //
+  // This ought to be locale sensitive so that we pick the best captions
+  // for the current locale. But for now, if the video file is named foo.mp4
+  // then we'll just look for a file in the same directory with name foo.vtt.
+  //
+  Captions.prototype.findAndDisplay = function(filepath) {
+    if (!filepath) {  // If it is a blob with no name we can't look for captions
+      return;
+    }
+
+    // Look for a vtt file for this video
+    // XXX: ignoring locale for now
+    var basename = filepath.substring(0, filepath.lastIndexOf('.'));
+    var captionsFilename = basename + '.vtt';
+
+    var sdcard = navigator.getDeviceStorage('sdcard');
+    if (!sdcard) return; // Captions are optional on desktop.
+    var request = sdcard.get(captionsFilename);
+    request.onsuccess = function() {
+      var track = document.createElement('track');
+      track.src = URL.createObjectURL(request.result);
+      track.default = true;
+      this.player.appendChild(track);
+      track.track.mode = 'showing';
+    }.bind(this);
+  };
+
+  exports.Captions = Captions;
+}(window));