webrtc-adapter/src/js/firefox/firefox_shim.js

A shim to insulate apps from WebRTC spec changes and browser prefix differences

/*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
 /* eslint-env node */
'use strict';

var utils = require('../utils');

var firefoxShim = {
  shimOnTrack: function(window) {
    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
        window.RTCPeerConnection.prototype)) {
      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
        get: function() {
          return this._ontrack;
        },
        set: function(f) {
          if (this._ontrack) {
            this.removeEventListener('track', this._ontrack);
            this.removeEventListener('addstream', this._ontrackpoly);
          }
          this.addEventListener('track', this._ontrack = f);
          this.addEventListener('addstream', this._ontrackpoly = function(e) {
            e.stream.getTracks().forEach(function(track) {
              var event = new Event('track');
              event.track = track;
              event.receiver = {track: track};
              event.streams = [e.stream];
              this.dispatchEvent(event);
            }.bind(this));
          }.bind(this));
        }
      });
    }
  },

  shimSourceObject: function(window) {
    // Firefox has supported mozSrcObject since FF22, unprefixed in 42.
    if (typeof window === 'object') {
      if (window.HTMLMediaElement &&
        !('srcObject' in window.HTMLMediaElement.prototype)) {
        // Shim the srcObject property, once, when HTMLMediaElement is found.
        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
          get: function() {
            return this.mozSrcObject;
          },
          set: function(stream) {
            this.mozSrcObject = stream;
          }
        });
      }
    }
  },

  shimPeerConnection: function(window) {
    var browserDetails = utils.detectBrowser(window);

    if (typeof window !== 'object' || !(window.RTCPeerConnection ||
        window.mozRTCPeerConnection)) {
      return; // probably media.peerconnection.enabled=false in about:config
    }
    // The RTCPeerConnection object.
    if (!window.RTCPeerConnection) {
      window.RTCPeerConnection = function(pcConfig, pcConstraints) {
        if (browserDetails.version < 38) {
          // .urls is not supported in FF < 38.
          // create RTCIceServers with a single url.
          if (pcConfig && pcConfig.iceServers) {
            var newIceServers = [];
            for (var i = 0; i < pcConfig.iceServers.length; i++) {
              var server = pcConfig.iceServers[i];
              if (server.hasOwnProperty('urls')) {
                for (var j = 0; j < server.urls.length; j++) {
                  var newServer = {
                    url: server.urls[j]
                  };
                  if (server.urls[j].indexOf('turn') === 0) {
                    newServer.username = server.username;
                    newServer.credential = server.credential;
                  }
                  newIceServers.push(newServer);
                }
              } else {
                newIceServers.push(pcConfig.iceServers[i]);
              }
            }
            pcConfig.iceServers = newIceServers;
          }
        }
        return new window.mozRTCPeerConnection(pcConfig, pcConstraints);
      };
      window.RTCPeerConnection.prototype =
          window.mozRTCPeerConnection.prototype;

      // wrap static methods. Currently just generateCertificate.
      if (window.mozRTCPeerConnection.generateCertificate) {
        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
          get: function() {
            return window.mozRTCPeerConnection.generateCertificate;
          }
        });
      }

      window.RTCSessionDescription = window.mozRTCSessionDescription;
      window.RTCIceCandidate = window.mozRTCIceCandidate;
    }

    // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
        .forEach(function(method) {
          var nativeMethod = window.RTCPeerConnection.prototype[method];
          window.RTCPeerConnection.prototype[method] = function() {
            arguments[0] = new ((method === 'addIceCandidate') ?
                window.RTCIceCandidate :
                window.RTCSessionDescription)(arguments[0]);
            return nativeMethod.apply(this, arguments);
          };
        });

    // support for addIceCandidate(null or undefined)
    var nativeAddIceCandidate =
        window.RTCPeerConnection.prototype.addIceCandidate;
    window.RTCPeerConnection.prototype.addIceCandidate = function() {
      if (!arguments[0]) {
        if (arguments[1]) {
          arguments[1].apply(null);
        }
        return Promise.resolve();
      }
      return nativeAddIceCandidate.apply(this, arguments);
    };

    // shim getStats with maplike support
    var makeMapStats = function(stats) {
      var map = new Map();
      Object.keys(stats).forEach(function(key) {
        map.set(key, stats[key]);
        map[key] = stats[key];
      });
      return map;
    };

    var modernStatsTypes = {
      inboundrtp: 'inbound-rtp',
      outboundrtp: 'outbound-rtp',
      candidatepair: 'candidate-pair',
      localcandidate: 'local-candidate',
      remotecandidate: 'remote-candidate'
    };

    var nativeGetStats = window.RTCPeerConnection.prototype.getStats;
    window.RTCPeerConnection.prototype.getStats = function(
      selector,
      onSucc,
      onErr
    ) {
      return nativeGetStats.apply(this, [selector || null])
        .then(function(stats) {
          if (browserDetails.version < 48) {
            stats = makeMapStats(stats);
          }
          if (browserDetails.version < 53 && !onSucc) {
            // Shim only promise getStats with spec-hyphens in type names
            // Leave callback version alone; misc old uses of forEach before Map
            try {
              stats.forEach(function(stat) {
                stat.type = modernStatsTypes[stat.type] || stat.type;
              });
            } catch (e) {
              if (e.name !== 'TypeError') {
                throw e;
              }
              // Avoid TypeError: "type" is read-only, in old versions. 34-43ish
              stats.forEach(function(stat, i) {
                stats.set(i, Object.assign({}, stat, {
                  type: modernStatsTypes[stat.type] || stat.type
                }));
              });
            }
          }
          return stats;
        })
        .then(onSucc, onErr);
    };
  }
};

// Expose public methods.
module.exports = {
  shimOnTrack: firefoxShim.shimOnTrack,
  shimSourceObject: firefoxShim.shimSourceObject,
  shimPeerConnection: firefoxShim.shimPeerConnection,
  shimGetUserMedia: require('./getusermedia')
};