(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.adapter = f()}})(function(){var define,module,exports;return (function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){
/*
 *  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 _adapter_factory = require('./adapter_factory.js');

var adapter = (0, _adapter_factory.adapterFactory)({ window: window });
module.exports = adapter; // this is the difference from adapter_core.

},{"./adapter_factory.js":2}],2:[function(require,module,exports){
'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.adapterFactory = adapterFactory;

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

var utils = _interopRequireWildcard(_utils);

var _chrome_shim = require('./chrome/chrome_shim');

var chromeShim = _interopRequireWildcard(_chrome_shim);

var _edge_shim = require('./edge/edge_shim');

var edgeShim = _interopRequireWildcard(_edge_shim);

var _firefox_shim = require('./firefox/firefox_shim');

var firefoxShim = _interopRequireWildcard(_firefox_shim);

var _safari_shim = require('./safari/safari_shim');

var safariShim = _interopRequireWildcard(_safari_shim);

var _common_shim = require('./common_shim');

var commonShim = _interopRequireWildcard(_common_shim);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

// Shimming starts here.
/*
 *  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.
 */
function adapterFactory() {
  var _ref = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
      window = _ref.window;

  var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {
    shimChrome: true,
    shimFirefox: true,
    shimEdge: true,
    shimSafari: true
  };

  // Utils.
  var logging = utils.log;
  var browserDetails = utils.detectBrowser(window);

  var adapter = {
    browserDetails: browserDetails,
    commonShim: commonShim,
    extractVersion: utils.extractVersion,
    disableLog: utils.disableLog,
    disableWarnings: utils.disableWarnings
  };

  // Shim browser if found.
  switch (browserDetails.browser) {
    case 'chrome':
      if (!chromeShim || !chromeShim.shimPeerConnection || !options.shimChrome) {
        logging('Chrome shim is not included in this adapter release.');
        return adapter;
      }
      logging('adapter.js shimming chrome.');
      // Export to the adapter global object visible in the browser.
      adapter.browserShim = chromeShim;

      chromeShim.shimGetUserMedia(window);
      chromeShim.shimMediaStream(window);
      chromeShim.shimPeerConnection(window);
      chromeShim.shimOnTrack(window);
      chromeShim.shimAddTrackRemoveTrack(window);
      chromeShim.shimGetSendersWithDtmf(window);
      chromeShim.shimSenderReceiverGetStats(window);
      chromeShim.fixNegotiationNeeded(window);

      commonShim.shimRTCIceCandidate(window);
      commonShim.shimConnectionState(window);
      commonShim.shimMaxMessageSize(window);
      commonShim.shimSendThrowTypeError(window);
      break;
    case 'firefox':
      if (!firefoxShim || !firefoxShim.shimPeerConnection || !options.shimFirefox) {
        logging('Firefox shim is not included in this adapter release.');
        return adapter;
      }
      logging('adapter.js shimming firefox.');
      // Export to the adapter global object visible in the browser.
      adapter.browserShim = firefoxShim;

      firefoxShim.shimGetUserMedia(window);
      firefoxShim.shimPeerConnection(window);
      firefoxShim.shimOnTrack(window);
      firefoxShim.shimRemoveStream(window);
      firefoxShim.shimSenderGetStats(window);
      firefoxShim.shimReceiverGetStats(window);
      firefoxShim.shimRTCDataChannel(window);

      commonShim.shimRTCIceCandidate(window);
      commonShim.shimConnectionState(window);
      commonShim.shimMaxMessageSize(window);
      commonShim.shimSendThrowTypeError(window);
      break;
    case 'edge':
      if (!edgeShim || !edgeShim.shimPeerConnection || !options.shimEdge) {
        logging('MS edge shim is not included in this adapter release.');
        return adapter;
      }
      logging('adapter.js shimming edge.');
      // Export to the adapter global object visible in the browser.
      adapter.browserShim = edgeShim;

      edgeShim.shimGetUserMedia(window);
      edgeShim.shimGetDisplayMedia(window);
      edgeShim.shimPeerConnection(window);
      edgeShim.shimReplaceTrack(window);

      // the edge shim implements the full RTCIceCandidate object.

      commonShim.shimMaxMessageSize(window);
      commonShim.shimSendThrowTypeError(window);
      break;
    case 'safari':
      if (!safariShim || !options.shimSafari) {
        logging('Safari shim is not included in this adapter release.');
        return adapter;
      }
      logging('adapter.js shimming safari.');
      // Export to the adapter global object visible in the browser.
      adapter.browserShim = safariShim;

      safariShim.shimRTCIceServerUrls(window);
      safariShim.shimCreateOfferLegacy(window);
      safariShim.shimCallbacksAPI(window);
      safariShim.shimLocalStreamsAPI(window);
      safariShim.shimRemoteStreamsAPI(window);
      safariShim.shimTrackEventTransceiver(window);
      safariShim.shimGetUserMedia(window);

      commonShim.shimRTCIceCandidate(window);
      commonShim.shimMaxMessageSize(window);
      commonShim.shimSendThrowTypeError(window);
      break;
    default:
      logging('Unsupported browser!');
      break;
  }

  return adapter;
}

// Browser shims.

},{"./chrome/chrome_shim":3,"./common_shim":6,"./edge/edge_shim":7,"./firefox/firefox_shim":11,"./safari/safari_shim":14,"./utils":15}],3:[function(require,module,exports){

/*
 *  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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

var _getusermedia = require('./getusermedia');

Object.defineProperty(exports, 'shimGetUserMedia', {
  enumerable: true,
  get: function get() {
    return _getusermedia.shimGetUserMedia;
  }
});

var _getdisplaymedia = require('./getdisplaymedia');

Object.defineProperty(exports, 'shimGetDisplayMedia', {
  enumerable: true,
  get: function get() {
    return _getdisplaymedia.shimGetDisplayMedia;
  }
});
exports.shimMediaStream = shimMediaStream;
exports.shimOnTrack = shimOnTrack;
exports.shimGetSendersWithDtmf = shimGetSendersWithDtmf;
exports.shimSenderReceiverGetStats = shimSenderReceiverGetStats;
exports.shimAddTrackRemoveTrackWithNative = shimAddTrackRemoveTrackWithNative;
exports.shimAddTrackRemoveTrack = shimAddTrackRemoveTrack;
exports.shimPeerConnection = shimPeerConnection;
exports.fixNegotiationNeeded = fixNegotiationNeeded;

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

var utils = _interopRequireWildcard(_utils);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

/* iterates the stats graph recursively. */
function walkStats(stats, base, resultSet) {
  if (!base || resultSet.has(base.id)) {
    return;
  }
  resultSet.set(base.id, base);
  Object.keys(base).forEach(function (name) {
    if (name.endsWith('Id')) {
      walkStats(stats, stats.get(base[name]), resultSet);
    } else if (name.endsWith('Ids')) {
      base[name].forEach(function (id) {
        walkStats(stats, stats.get(id), resultSet);
      });
    }
  });
}

/* filter getStats for a sender/receiver track. */
function filterStats(result, track, outbound) {
  var streamStatsType = outbound ? 'outbound-rtp' : 'inbound-rtp';
  var filteredResult = new Map();
  if (track === null) {
    return filteredResult;
  }
  var trackStats = [];
  result.forEach(function (value) {
    if (value.type === 'track' && value.trackIdentifier === track.id) {
      trackStats.push(value);
    }
  });
  trackStats.forEach(function (trackStat) {
    result.forEach(function (stats) {
      if (stats.type === streamStatsType && stats.trackId === trackStat.id) {
        walkStats(result, stats, filteredResult);
      }
    });
  });
  return filteredResult;
}

function shimMediaStream(window) {
  window.MediaStream = window.MediaStream || window.webkitMediaStream;
}

function shimOnTrack(window) {
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('ontrack' in window.RTCPeerConnection.prototype)) {
    Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
      get: function get() {
        return this._ontrack;
      },
      set: function set(f) {
        if (this._ontrack) {
          this.removeEventListener('track', this._ontrack);
        }
        this.addEventListener('track', this._ontrack = f);
      },

      enumerable: true,
      configurable: true
    });
    var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
    window.RTCPeerConnection.prototype.setRemoteDescription = function () {
      var _this = this;

      if (!this._ontrackpoly) {
        this._ontrackpoly = function (e) {
          // onaddstream does not fire when a track is added to an existing
          // stream. But stream.onaddtrack is implemented so we use that.
          e.stream.addEventListener('addtrack', function (te) {
            var receiver = void 0;
            if (window.RTCPeerConnection.prototype.getReceivers) {
              receiver = _this.getReceivers().find(function (r) {
                return r.track && r.track.id === te.track.id;
              });
            } else {
              receiver = { track: te.track };
            }

            var event = new Event('track');
            event.track = te.track;
            event.receiver = receiver;
            event.transceiver = { receiver: receiver };
            event.streams = [e.stream];
            _this.dispatchEvent(event);
          });
          e.stream.getTracks().forEach(function (track) {
            var receiver = void 0;
            if (window.RTCPeerConnection.prototype.getReceivers) {
              receiver = _this.getReceivers().find(function (r) {
                return r.track && r.track.id === track.id;
              });
            } else {
              receiver = { track: track };
            }
            var event = new Event('track');
            event.track = track;
            event.receiver = receiver;
            event.transceiver = { receiver: receiver };
            event.streams = [e.stream];
            _this.dispatchEvent(event);
          });
        };
        this.addEventListener('addstream', this._ontrackpoly);
      }
      return origSetRemoteDescription.apply(this, arguments);
    };
  } else {
    // even if RTCRtpTransceiver is in window, it is only used and
    // emitted in unified-plan. Unfortunately this means we need
    // to unconditionally wrap the event.
    utils.wrapPeerConnectionEvent(window, 'track', function (e) {
      if (!e.transceiver) {
        Object.defineProperty(e, 'transceiver', { value: { receiver: e.receiver } });
      }
      return e;
    });
  }
}

function shimGetSendersWithDtmf(window) {
  // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('getSenders' in window.RTCPeerConnection.prototype) && 'createDTMFSender' in window.RTCPeerConnection.prototype) {
    var shimSenderWithDtmf = function shimSenderWithDtmf(pc, track) {
      return {
        track: track,
        get dtmf() {
          if (this._dtmf === undefined) {
            if (track.kind === 'audio') {
              this._dtmf = pc.createDTMFSender(track);
            } else {
              this._dtmf = null;
            }
          }
          return this._dtmf;
        },
        _pc: pc
      };
    };

    // augment addTrack when getSenders is not available.
    if (!window.RTCPeerConnection.prototype.getSenders) {
      window.RTCPeerConnection.prototype.getSenders = function () {
        this._senders = this._senders || [];
        return this._senders.slice(); // return a copy of the internal state.
      };
      var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
      window.RTCPeerConnection.prototype.addTrack = function (track, stream) {
        var sender = origAddTrack.apply(this, arguments);
        if (!sender) {
          sender = shimSenderWithDtmf(this, track);
          this._senders.push(sender);
        }
        return sender;
      };

      var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
      window.RTCPeerConnection.prototype.removeTrack = function (sender) {
        origRemoveTrack.apply(this, arguments);
        var idx = this._senders.indexOf(sender);
        if (idx !== -1) {
          this._senders.splice(idx, 1);
        }
      };
    }
    var origAddStream = window.RTCPeerConnection.prototype.addStream;
    window.RTCPeerConnection.prototype.addStream = function (stream) {
      var _this2 = this;

      this._senders = this._senders || [];
      origAddStream.apply(this, [stream]);
      stream.getTracks().forEach(function (track) {
        _this2._senders.push(shimSenderWithDtmf(_this2, track));
      });
    };

    var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
    window.RTCPeerConnection.prototype.removeStream = function (stream) {
      var _this3 = this;

      this._senders = this._senders || [];
      origRemoveStream.apply(this, [stream]);

      stream.getTracks().forEach(function (track) {
        var sender = _this3._senders.find(function (s) {
          return s.track === track;
        });
        if (sender) {
          // remove sender
          _this3._senders.splice(_this3._senders.indexOf(sender), 1);
        }
      });
    };
  } else if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && 'getSenders' in window.RTCPeerConnection.prototype && 'createDTMFSender' in window.RTCPeerConnection.prototype && window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
    var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
    window.RTCPeerConnection.prototype.getSenders = function () {
      var _this4 = this;

      var senders = origGetSenders.apply(this, []);
      senders.forEach(function (sender) {
        return sender._pc = _this4;
      });
      return senders;
    };

    Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
      get: function get() {
        if (this._dtmf === undefined) {
          if (this.track.kind === 'audio') {
            this._dtmf = this._pc.createDTMFSender(this.track);
          } else {
            this._dtmf = null;
          }
        }
        return this._dtmf;
      }
    });
  }
}

function shimSenderReceiverGetStats(window) {
  if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender && window.RTCRtpReceiver)) {
    return;
  }

  // shim sender stats.
  if (!('getStats' in window.RTCRtpSender.prototype)) {
    var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
    if (origGetSenders) {
      window.RTCPeerConnection.prototype.getSenders = function () {
        var _this5 = this;

        var senders = origGetSenders.apply(this, []);
        senders.forEach(function (sender) {
          return sender._pc = _this5;
        });
        return senders;
      };
    }

    var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
    if (origAddTrack) {
      window.RTCPeerConnection.prototype.addTrack = function () {
        var sender = origAddTrack.apply(this, arguments);
        sender._pc = this;
        return sender;
      };
    }
    window.RTCRtpSender.prototype.getStats = function () {
      var sender = this;
      return this._pc.getStats().then(function (result) {
        return (
          /* Note: this will include stats of all senders that
           *   send a track with the same id as sender.track as
           *   it is not possible to identify the RTCRtpSender.
           */
          filterStats(result, sender.track, true)
        );
      });
    };
  }

  // shim receiver stats.
  if (!('getStats' in window.RTCRtpReceiver.prototype)) {
    var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
    if (origGetReceivers) {
      window.RTCPeerConnection.prototype.getReceivers = function () {
        var _this6 = this;

        var receivers = origGetReceivers.apply(this, []);
        receivers.forEach(function (receiver) {
          return receiver._pc = _this6;
        });
        return receivers;
      };
    }
    utils.wrapPeerConnectionEvent(window, 'track', function (e) {
      e.receiver._pc = e.srcElement;
      return e;
    });
    window.RTCRtpReceiver.prototype.getStats = function () {
      var receiver = this;
      return this._pc.getStats().then(function (result) {
        return filterStats(result, receiver.track, false);
      });
    };
  }

  if (!('getStats' in window.RTCRtpSender.prototype && 'getStats' in window.RTCRtpReceiver.prototype)) {
    return;
  }

  // shim RTCPeerConnection.getStats(track).
  var origGetStats = window.RTCPeerConnection.prototype.getStats;
  window.RTCPeerConnection.prototype.getStats = function () {
    if (arguments.length > 0 && arguments[0] instanceof window.MediaStreamTrack) {
      var track = arguments[0];
      var sender = void 0;
      var receiver = void 0;
      var err = void 0;
      this.getSenders().forEach(function (s) {
        if (s.track === track) {
          if (sender) {
            err = true;
          } else {
            sender = s;
          }
        }
      });
      this.getReceivers().forEach(function (r) {
        if (r.track === track) {
          if (receiver) {
            err = true;
          } else {
            receiver = r;
          }
        }
        return r.track === track;
      });
      if (err || sender && receiver) {
        return Promise.reject(new DOMException('There are more than one sender or receiver for the track.', 'InvalidAccessError'));
      } else if (sender) {
        return sender.getStats();
      } else if (receiver) {
        return receiver.getStats();
      }
      return Promise.reject(new DOMException('There is no sender or receiver for the track.', 'InvalidAccessError'));
    }
    return origGetStats.apply(this, arguments);
  };
}

function shimAddTrackRemoveTrackWithNative(window) {
  // shim addTrack/removeTrack with native variants in order to make
  // the interactions with legacy getLocalStreams behave as in other browsers.
  // Keeps a mapping stream.id => [stream, rtpsenders...]
  window.RTCPeerConnection.prototype.getLocalStreams = function () {
    var _this7 = this;

    this._shimmedLocalStreams = this._shimmedLocalStreams || {};
    return Object.keys(this._shimmedLocalStreams).map(function (streamId) {
      return _this7._shimmedLocalStreams[streamId][0];
    });
  };

  var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
  window.RTCPeerConnection.prototype.addTrack = function (track, stream) {
    if (!stream) {
      return origAddTrack.apply(this, arguments);
    }
    this._shimmedLocalStreams = this._shimmedLocalStreams || {};

    var sender = origAddTrack.apply(this, arguments);
    if (!this._shimmedLocalStreams[stream.id]) {
      this._shimmedLocalStreams[stream.id] = [stream, sender];
    } else if (this._shimmedLocalStreams[stream.id].indexOf(sender) === -1) {
      this._shimmedLocalStreams[stream.id].push(sender);
    }
    return sender;
  };

  var origAddStream = window.RTCPeerConnection.prototype.addStream;
  window.RTCPeerConnection.prototype.addStream = function (stream) {
    var _this8 = this;

    this._shimmedLocalStreams = this._shimmedLocalStreams || {};

    stream.getTracks().forEach(function (track) {
      var alreadyExists = _this8.getSenders().find(function (s) {
        return s.track === track;
      });
      if (alreadyExists) {
        throw new DOMException('Track already exists.', 'InvalidAccessError');
      }
    });
    var existingSenders = this.getSenders();
    origAddStream.apply(this, arguments);
    var newSenders = this.getSenders().filter(function (newSender) {
      return existingSenders.indexOf(newSender) === -1;
    });
    this._shimmedLocalStreams[stream.id] = [stream].concat(newSenders);
  };

  var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
  window.RTCPeerConnection.prototype.removeStream = function (stream) {
    this._shimmedLocalStreams = this._shimmedLocalStreams || {};
    delete this._shimmedLocalStreams[stream.id];
    return origRemoveStream.apply(this, arguments);
  };

  var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
  window.RTCPeerConnection.prototype.removeTrack = function (sender) {
    var _this9 = this;

    this._shimmedLocalStreams = this._shimmedLocalStreams || {};
    if (sender) {
      Object.keys(this._shimmedLocalStreams).forEach(function (streamId) {
        var idx = _this9._shimmedLocalStreams[streamId].indexOf(sender);
        if (idx !== -1) {
          _this9._shimmedLocalStreams[streamId].splice(idx, 1);
        }
        if (_this9._shimmedLocalStreams[streamId].length === 1) {
          delete _this9._shimmedLocalStreams[streamId];
        }
      });
    }
    return origRemoveTrack.apply(this, arguments);
  };
}

function shimAddTrackRemoveTrack(window) {
  if (!window.RTCPeerConnection) {
    return;
  }
  var browserDetails = utils.detectBrowser(window);
  // shim addTrack and removeTrack.
  if (window.RTCPeerConnection.prototype.addTrack && browserDetails.version >= 65) {
    return this.shimAddTrackRemoveTrackWithNative(window);
  }

  // also shim pc.getLocalStreams when addTrack is shimmed
  // to return the original streams.
  var origGetLocalStreams = window.RTCPeerConnection.prototype.getLocalStreams;
  window.RTCPeerConnection.prototype.getLocalStreams = function () {
    var _this10 = this;

    var nativeStreams = origGetLocalStreams.apply(this);
    this._reverseStreams = this._reverseStreams || {};
    return nativeStreams.map(function (stream) {
      return _this10._reverseStreams[stream.id];
    });
  };

  var origAddStream = window.RTCPeerConnection.prototype.addStream;
  window.RTCPeerConnection.prototype.addStream = function (stream) {
    var _this11 = this;

    this._streams = this._streams || {};
    this._reverseStreams = this._reverseStreams || {};

    stream.getTracks().forEach(function (track) {
      var alreadyExists = _this11.getSenders().find(function (s) {
        return s.track === track;
      });
      if (alreadyExists) {
        throw new DOMException('Track already exists.', 'InvalidAccessError');
      }
    });
    // Add identity mapping for consistency with addTrack.
    // Unless this is being used with a stream from addTrack.
    if (!this._reverseStreams[stream.id]) {
      var newStream = new window.MediaStream(stream.getTracks());
      this._streams[stream.id] = newStream;
      this._reverseStreams[newStream.id] = stream;
      stream = newStream;
    }
    origAddStream.apply(this, [stream]);
  };

  var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
  window.RTCPeerConnection.prototype.removeStream = function (stream) {
    this._streams = this._streams || {};
    this._reverseStreams = this._reverseStreams || {};

    origRemoveStream.apply(this, [this._streams[stream.id] || stream]);
    delete this._reverseStreams[this._streams[stream.id] ? this._streams[stream.id].id : stream.id];
    delete this._streams[stream.id];
  };

  window.RTCPeerConnection.prototype.addTrack = function (track, stream) {
    var _this12 = this;

    if (this.signalingState === 'closed') {
      throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError');
    }
    var streams = [].slice.call(arguments, 1);
    if (streams.length !== 1 || !streams[0].getTracks().find(function (t) {
      return t === track;
    })) {
      // this is not fully correct but all we can manage without
      // [[associated MediaStreams]] internal slot.
      throw new DOMException('The adapter.js addTrack polyfill only supports a single ' + ' stream which is associated with the specified track.', 'NotSupportedError');
    }

    var alreadyExists = this.getSenders().find(function (s) {
      return s.track === track;
    });
    if (alreadyExists) {
      throw new DOMException('Track already exists.', 'InvalidAccessError');
    }

    this._streams = this._streams || {};
    this._reverseStreams = this._reverseStreams || {};
    var oldStream = this._streams[stream.id];
    if (oldStream) {
      // this is using odd Chrome behaviour, use with caution:
      // https://bugs.chromium.org/p/webrtc/issues/detail?id=7815
      // Note: we rely on the high-level addTrack/dtmf shim to
      // create the sender with a dtmf sender.
      oldStream.addTrack(track);

      // Trigger ONN async.
      Promise.resolve().then(function () {
        _this12.dispatchEvent(new Event('negotiationneeded'));
      });
    } else {
      var newStream = new window.MediaStream([track]);
      this._streams[stream.id] = newStream;
      this._reverseStreams[newStream.id] = stream;
      this.addStream(newStream);
    }
    return this.getSenders().find(function (s) {
      return s.track === track;
    });
  };

  // replace the internal stream id with the external one and
  // vice versa.
  function replaceInternalStreamId(pc, description) {
    var sdp = description.sdp;
    Object.keys(pc._reverseStreams || []).forEach(function (internalId) {
      var externalStream = pc._reverseStreams[internalId];
      var internalStream = pc._streams[externalStream.id];
      sdp = sdp.replace(new RegExp(internalStream.id, 'g'), externalStream.id);
    });
    return new RTCSessionDescription({
      type: description.type,
      sdp: sdp
    });
  }
  function replaceExternalStreamId(pc, description) {
    var sdp = description.sdp;
    Object.keys(pc._reverseStreams || []).forEach(function (internalId) {
      var externalStream = pc._reverseStreams[internalId];
      var internalStream = pc._streams[externalStream.id];
      sdp = sdp.replace(new RegExp(externalStream.id, 'g'), internalStream.id);
    });
    return new RTCSessionDescription({
      type: description.type,
      sdp: sdp
    });
  }
  ['createOffer', 'createAnswer'].forEach(function (method) {
    var nativeMethod = window.RTCPeerConnection.prototype[method];
    window.RTCPeerConnection.prototype[method] = function () {
      var _this13 = this;

      var args = arguments;
      var isLegacyCall = arguments.length && typeof arguments[0] === 'function';
      if (isLegacyCall) {
        return nativeMethod.apply(this, [function (description) {
          var desc = replaceInternalStreamId(_this13, description);
          args[0].apply(null, [desc]);
        }, function (err) {
          if (args[1]) {
            args[1].apply(null, err);
          }
        }, arguments[2]]);
      }
      return nativeMethod.apply(this, arguments).then(function (description) {
        return replaceInternalStreamId(_this13, description);
      });
    };
  });

  var origSetLocalDescription = window.RTCPeerConnection.prototype.setLocalDescription;
  window.RTCPeerConnection.prototype.setLocalDescription = function () {
    if (!arguments.length || !arguments[0].type) {
      return origSetLocalDescription.apply(this, arguments);
    }
    arguments[0] = replaceExternalStreamId(this, arguments[0]);
    return origSetLocalDescription.apply(this, arguments);
  };

  // TODO: mangle getStats: https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamstats-streamidentifier

  var origLocalDescription = Object.getOwnPropertyDescriptor(window.RTCPeerConnection.prototype, 'localDescription');
  Object.defineProperty(window.RTCPeerConnection.prototype, 'localDescription', {
    get: function get() {
      var description = origLocalDescription.get.apply(this);
      if (description.type === '') {
        return description;
      }
      return replaceInternalStreamId(this, description);
    }
  });

  window.RTCPeerConnection.prototype.removeTrack = function (sender) {
    var _this14 = this;

    if (this.signalingState === 'closed') {
      throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError');
    }
    // We can not yet check for sender instanceof RTCRtpSender
    // since we shim RTPSender. So we check if sender._pc is set.
    if (!sender._pc) {
      throw new DOMException('Argument 1 of RTCPeerConnection.removeTrack ' + 'does not implement interface RTCRtpSender.', 'TypeError');
    }
    var isLocal = sender._pc === this;
    if (!isLocal) {
      throw new DOMException('Sender was not created by this connection.', 'InvalidAccessError');
    }

    // Search for the native stream the senders track belongs to.
    this._streams = this._streams || {};
    var stream = void 0;
    Object.keys(this._streams).forEach(function (streamid) {
      var hasTrack = _this14._streams[streamid].getTracks().find(function (track) {
        return sender.track === track;
      });
      if (hasTrack) {
        stream = _this14._streams[streamid];
      }
    });

    if (stream) {
      if (stream.getTracks().length === 1) {
        // if this is the last track of the stream, remove the stream. This
        // takes care of any shimmed _senders.
        this.removeStream(this._reverseStreams[stream.id]);
      } else {
        // relying on the same odd chrome behaviour as above.
        stream.removeTrack(sender.track);
      }
      this.dispatchEvent(new Event('negotiationneeded'));
    }
  };
}

function shimPeerConnection(window) {
  if (!window.RTCPeerConnection && window.webkitRTCPeerConnection) {
    // very basic support for old versions.
    window.RTCPeerConnection = window.webkitRTCPeerConnection;
  }
  if (!window.RTCPeerConnection) {
    return;
  }

  var origGetStats = window.RTCPeerConnection.prototype.getStats;
  window.RTCPeerConnection.prototype.getStats = function (selector, successCallback, errorCallback) {
    var _this15 = this;

    var args = arguments;

    // If selector is a function then we are in the old style stats so just
    // pass back the original getStats format to avoid breaking old users.
    if (arguments.length > 0 && typeof selector === 'function') {
      return origGetStats.apply(this, arguments);
    }

    // When spec-style getStats is supported, return those when called with
    // either no arguments or the selector argument is null.
    if (origGetStats.length === 0 && (arguments.length === 0 || typeof arguments[0] !== 'function')) {
      return origGetStats.apply(this, []);
    }

    var fixChromeStats_ = function fixChromeStats_(response) {
      var standardReport = {};
      var reports = response.result();
      reports.forEach(function (report) {
        var standardStats = {
          id: report.id,
          timestamp: report.timestamp,
          type: {
            localcandidate: 'local-candidate',
            remotecandidate: 'remote-candidate'
          }[report.type] || report.type
        };
        report.names().forEach(function (name) {
          standardStats[name] = report.stat(name);
        });
        standardReport[standardStats.id] = standardStats;
      });

      return standardReport;
    };

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

    if (arguments.length >= 2) {
      var successCallbackWrapper_ = function successCallbackWrapper_(response) {
        args[1](makeMapStats(fixChromeStats_(response)));
      };

      return origGetStats.apply(this, [successCallbackWrapper_, arguments[0]]);
    }

    // promise-support
    return new Promise(function (resolve, reject) {
      origGetStats.apply(_this15, [function (response) {
        resolve(makeMapStats(fixChromeStats_(response)));
      }, reject]);
    }).then(successCallback, errorCallback);
  };

  // shim implicit creation of RTCSessionDescription/RTCIceCandidate
  ['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);
  };
}

function fixNegotiationNeeded(window) {
  utils.wrapPeerConnectionEvent(window, 'negotiationneeded', function (e) {
    var pc = e.target;
    if (pc.signalingState !== 'stable') {
      return;
    }
    return e;
  });
}

},{"../utils.js":15,"./getdisplaymedia":4,"./getusermedia":5}],4:[function(require,module,exports){
/*
 *  Copyright (c) 2018 The adapter.js 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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.shimGetDisplayMedia = shimGetDisplayMedia;
function shimGetDisplayMedia(window, getSourceId) {
  if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
    return;
  }
  if (!window.navigator.mediaDevices) {
    return;
  }
  // getSourceId is a function that returns a promise resolving with
  // the sourceId of the screen/window/tab to be shared.
  if (typeof getSourceId !== 'function') {
    console.error('shimGetDisplayMedia: getSourceId argument is not ' + 'a function');
    return;
  }
  window.navigator.mediaDevices.getDisplayMedia = function (constraints) {
    return getSourceId(constraints).then(function (sourceId) {
      var widthSpecified = constraints.video && constraints.video.width;
      var heightSpecified = constraints.video && constraints.video.height;
      var frameRateSpecified = constraints.video && constraints.video.frameRate;
      constraints.video = {
        mandatory: {
          chromeMediaSource: 'desktop',
          chromeMediaSourceId: sourceId,
          maxFrameRate: frameRateSpecified || 3
        }
      };
      if (widthSpecified) {
        constraints.video.mandatory.maxWidth = widthSpecified;
      }
      if (heightSpecified) {
        constraints.video.mandatory.maxHeight = heightSpecified;
      }
      return window.navigator.mediaDevices.getUserMedia(constraints);
    });
  };
}

},{}],5:[function(require,module,exports){
/*
 *  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';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

exports.shimGetUserMedia = shimGetUserMedia;

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

var utils = _interopRequireWildcard(_utils);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

var logging = utils.log;

function shimGetUserMedia(window) {
  var navigator = window && window.navigator;

  if (!navigator.mediaDevices) {
    return;
  }

  var browserDetails = utils.detectBrowser(window);

  var constraintsToChrome_ = function constraintsToChrome_(c) {
    if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) !== 'object' || c.mandatory || c.optional) {
      return c;
    }
    var cc = {};
    Object.keys(c).forEach(function (key) {
      if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
        return;
      }
      var r = _typeof(c[key]) === 'object' ? c[key] : { ideal: c[key] };
      if (r.exact !== undefined && typeof r.exact === 'number') {
        r.min = r.max = r.exact;
      }
      var oldname_ = function oldname_(prefix, name) {
        if (prefix) {
          return prefix + name.charAt(0).toUpperCase() + name.slice(1);
        }
        return name === 'deviceId' ? 'sourceId' : name;
      };
      if (r.ideal !== undefined) {
        cc.optional = cc.optional || [];
        var oc = {};
        if (typeof r.ideal === 'number') {
          oc[oldname_('min', key)] = r.ideal;
          cc.optional.push(oc);
          oc = {};
          oc[oldname_('max', key)] = r.ideal;
          cc.optional.push(oc);
        } else {
          oc[oldname_('', key)] = r.ideal;
          cc.optional.push(oc);
        }
      }
      if (r.exact !== undefined && typeof r.exact !== 'number') {
        cc.mandatory = cc.mandatory || {};
        cc.mandatory[oldname_('', key)] = r.exact;
      } else {
        ['min', 'max'].forEach(function (mix) {
          if (r[mix] !== undefined) {
            cc.mandatory = cc.mandatory || {};
            cc.mandatory[oldname_(mix, key)] = r[mix];
          }
        });
      }
    });
    if (c.advanced) {
      cc.optional = (cc.optional || []).concat(c.advanced);
    }
    return cc;
  };

  var shimConstraints_ = function shimConstraints_(constraints, func) {
    if (browserDetails.version >= 61) {
      return func(constraints);
    }
    constraints = JSON.parse(JSON.stringify(constraints));
    if (constraints && _typeof(constraints.audio) === 'object') {
      var remap = function remap(obj, a, b) {
        if (a in obj && !(b in obj)) {
          obj[b] = obj[a];
          delete obj[a];
        }
      };
      constraints = JSON.parse(JSON.stringify(constraints));
      remap(constraints.audio, 'autoGainControl', 'googAutoGainControl');
      remap(constraints.audio, 'noiseSuppression', 'googNoiseSuppression');
      constraints.audio = constraintsToChrome_(constraints.audio);
    }
    if (constraints && _typeof(constraints.video) === 'object') {
      // Shim facingMode for mobile & surface pro.
      var face = constraints.video.facingMode;
      face = face && ((typeof face === 'undefined' ? 'undefined' : _typeof(face)) === 'object' ? face : { ideal: face });
      var getSupportedFacingModeLies = browserDetails.version < 66;

      if (face && (face.exact === 'user' || face.exact === 'environment' || face.ideal === 'user' || face.ideal === 'environment') && !(navigator.mediaDevices.getSupportedConstraints && navigator.mediaDevices.getSupportedConstraints().facingMode && !getSupportedFacingModeLies)) {
        delete constraints.video.facingMode;
        var matches = void 0;
        if (face.exact === 'environment' || face.ideal === 'environment') {
          matches = ['back', 'rear'];
        } else if (face.exact === 'user' || face.ideal === 'user') {
          matches = ['front'];
        }
        if (matches) {
          // Look for matches in label, or use last cam for back (typical).
          return navigator.mediaDevices.enumerateDevices().then(function (devices) {
            devices = devices.filter(function (d) {
              return d.kind === 'videoinput';
            });
            var dev = devices.find(function (d) {
              return matches.some(function (match) {
                return d.label.toLowerCase().includes(match);
              });
            });
            if (!dev && devices.length && matches.includes('back')) {
              dev = devices[devices.length - 1]; // more likely the back cam
            }
            if (dev) {
              constraints.video.deviceId = face.exact ? { exact: dev.deviceId } : { ideal: dev.deviceId };
            }
            constraints.video = constraintsToChrome_(constraints.video);
            logging('chrome: ' + JSON.stringify(constraints));
            return func(constraints);
          });
        }
      }
      constraints.video = constraintsToChrome_(constraints.video);
    }
    logging('chrome: ' + JSON.stringify(constraints));
    return func(constraints);
  };

  var shimError_ = function shimError_(e) {
    if (browserDetails.version >= 64) {
      return e;
    }
    return {
      name: {
        PermissionDeniedError: 'NotAllowedError',
        PermissionDismissedError: 'NotAllowedError',
        InvalidStateError: 'NotAllowedError',
        DevicesNotFoundError: 'NotFoundError',
        ConstraintNotSatisfiedError: 'OverconstrainedError',
        TrackStartError: 'NotReadableError',
        MediaDeviceFailedDueToShutdown: 'NotAllowedError',
        MediaDeviceKillSwitchOn: 'NotAllowedError',
        TabCaptureError: 'AbortError',
        ScreenCaptureError: 'AbortError',
        DeviceCaptureError: 'AbortError'
      }[e.name] || e.name,
      message: e.message,
      constraint: e.constraint || e.constraintName,
      toString: function toString() {
        return this.name + (this.message && ': ') + this.message;
      }
    };
  };

  var getUserMedia_ = function getUserMedia_(constraints, onSuccess, onError) {
    shimConstraints_(constraints, function (c) {
      navigator.webkitGetUserMedia(c, onSuccess, function (e) {
        if (onError) {
          onError(shimError_(e));
        }
      });
    });
  };
  navigator.getUserMedia = getUserMedia_.bind(navigator);

  // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
  // function which returns a Promise, it does not accept spec-style
  // constraints.
  var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
  navigator.mediaDevices.getUserMedia = function (cs) {
    return shimConstraints_(cs, function (c) {
      return origGetUserMedia(c).then(function (stream) {
        if (c.audio && !stream.getAudioTracks().length || c.video && !stream.getVideoTracks().length) {
          stream.getTracks().forEach(function (track) {
            track.stop();
          });
          throw new DOMException('', 'NotFoundError');
        }
        return stream;
      }, function (e) {
        return Promise.reject(shimError_(e));
      });
    });
  };
}

},{"../utils.js":15}],6:[function(require,module,exports){
/*
 *  Copyright (c) 2017 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';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

exports.shimRTCIceCandidate = shimRTCIceCandidate;
exports.shimMaxMessageSize = shimMaxMessageSize;
exports.shimSendThrowTypeError = shimSendThrowTypeError;
exports.shimConnectionState = shimConnectionState;

var _sdp = require('sdp');

var _sdp2 = _interopRequireDefault(_sdp);

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

var utils = _interopRequireWildcard(_utils);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function shimRTCIceCandidate(window) {
  // foundation is arbitrarily chosen as an indicator for full support for
  // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
  if (!window.RTCIceCandidate || window.RTCIceCandidate && 'foundation' in window.RTCIceCandidate.prototype) {
    return;
  }

  var NativeRTCIceCandidate = window.RTCIceCandidate;
  window.RTCIceCandidate = function (args) {
    // Remove the a= which shouldn't be part of the candidate string.
    if ((typeof args === 'undefined' ? 'undefined' : _typeof(args)) === 'object' && args.candidate && args.candidate.indexOf('a=') === 0) {
      args = JSON.parse(JSON.stringify(args));
      args.candidate = args.candidate.substr(2);
    }

    if (args.candidate && args.candidate.length) {
      // Augment the native candidate with the parsed fields.
      var nativeCandidate = new NativeRTCIceCandidate(args);
      var parsedCandidate = _sdp2.default.parseCandidate(args.candidate);
      var augmentedCandidate = Object.assign(nativeCandidate, parsedCandidate);

      // Add a serializer that does not serialize the extra attributes.
      augmentedCandidate.toJSON = function () {
        return {
          candidate: augmentedCandidate.candidate,
          sdpMid: augmentedCandidate.sdpMid,
          sdpMLineIndex: augmentedCandidate.sdpMLineIndex,
          usernameFragment: augmentedCandidate.usernameFragment
        };
      };
      return augmentedCandidate;
    }
    return new NativeRTCIceCandidate(args);
  };
  window.RTCIceCandidate.prototype = NativeRTCIceCandidate.prototype;

  // Hook up the augmented candidate in onicecandidate and
  // addEventListener('icecandidate', ...)
  utils.wrapPeerConnectionEvent(window, 'icecandidate', function (e) {
    if (e.candidate) {
      Object.defineProperty(e, 'candidate', {
        value: new window.RTCIceCandidate(e.candidate),
        writable: 'false'
      });
    }
    return e;
  });
}

function shimMaxMessageSize(window) {
  if (window.RTCSctpTransport || !window.RTCPeerConnection) {
    return;
  }
  var browserDetails = utils.detectBrowser(window);

  if (!('sctp' in window.RTCPeerConnection.prototype)) {
    Object.defineProperty(window.RTCPeerConnection.prototype, 'sctp', {
      get: function get() {
        return typeof this._sctp === 'undefined' ? null : this._sctp;
      }
    });
  }

  var sctpInDescription = function sctpInDescription(description) {
    var sections = _sdp2.default.splitSections(description.sdp);
    sections.shift();
    return sections.some(function (mediaSection) {
      var mLine = _sdp2.default.parseMLine(mediaSection);
      return mLine && mLine.kind === 'application' && mLine.protocol.indexOf('SCTP') !== -1;
    });
  };

  var getRemoteFirefoxVersion = function getRemoteFirefoxVersion(description) {
    // TODO: Is there a better solution for detecting Firefox?
    var match = description.sdp.match(/mozilla...THIS_IS_SDPARTA-(\d+)/);
    if (match === null || match.length < 2) {
      return -1;
    }
    var version = parseInt(match[1], 10);
    // Test for NaN (yes, this is ugly)
    return version !== version ? -1 : version;
  };

  var getCanSendMaxMessageSize = function getCanSendMaxMessageSize(remoteIsFirefox) {
    // Every implementation we know can send at least 64 KiB.
    // Note: Although Chrome is technically able to send up to 256 KiB, the
    //       data does not reach the other peer reliably.
    //       See: https://bugs.chromium.org/p/webrtc/issues/detail?id=8419
    var canSendMaxMessageSize = 65536;
    if (browserDetails.browser === 'firefox') {
      if (browserDetails.version < 57) {
        if (remoteIsFirefox === -1) {
          // FF < 57 will send in 16 KiB chunks using the deprecated PPID
          // fragmentation.
          canSendMaxMessageSize = 16384;
        } else {
          // However, other FF (and RAWRTC) can reassemble PPID-fragmented
          // messages. Thus, supporting ~2 GiB when sending.
          canSendMaxMessageSize = 2147483637;
        }
      } else if (browserDetails.version < 60) {
        // Currently, all FF >= 57 will reset the remote maximum message size
        // to the default value when a data channel is created at a later
        // stage. :(
        // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831
        canSendMaxMessageSize = browserDetails.version === 57 ? 65535 : 65536;
      } else {
        // FF >= 60 supports sending ~2 GiB
        canSendMaxMessageSize = 2147483637;
      }
    }
    return canSendMaxMessageSize;
  };

  var getMaxMessageSize = function getMaxMessageSize(description, remoteIsFirefox) {
    // Note: 65536 bytes is the default value from the SDP spec. Also,
    //       every implementation we know supports receiving 65536 bytes.
    var maxMessageSize = 65536;

    // FF 57 has a slightly incorrect default remote max message size, so
    // we need to adjust it here to avoid a failure when sending.
    // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1425697
    if (browserDetails.browser === 'firefox' && browserDetails.version === 57) {
      maxMessageSize = 65535;
    }

    var match = _sdp2.default.matchPrefix(description.sdp, 'a=max-message-size:');
    if (match.length > 0) {
      maxMessageSize = parseInt(match[0].substr(19), 10);
    } else if (browserDetails.browser === 'firefox' && remoteIsFirefox !== -1) {
      // If the maximum message size is not present in the remote SDP and
      // both local and remote are Firefox, the remote peer can receive
      // ~2 GiB.
      maxMessageSize = 2147483637;
    }
    return maxMessageSize;
  };

  var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
  window.RTCPeerConnection.prototype.setRemoteDescription = function () {
    this._sctp = null;

    if (sctpInDescription(arguments[0])) {
      // Check if the remote is FF.
      var isFirefox = getRemoteFirefoxVersion(arguments[0]);

      // Get the maximum message size the local peer is capable of sending
      var canSendMMS = getCanSendMaxMessageSize(isFirefox);

      // Get the maximum message size of the remote peer.
      var remoteMMS = getMaxMessageSize(arguments[0], isFirefox);

      // Determine final maximum message size
      var maxMessageSize = void 0;
      if (canSendMMS === 0 && remoteMMS === 0) {
        maxMessageSize = Number.POSITIVE_INFINITY;
      } else if (canSendMMS === 0 || remoteMMS === 0) {
        maxMessageSize = Math.max(canSendMMS, remoteMMS);
      } else {
        maxMessageSize = Math.min(canSendMMS, remoteMMS);
      }

      // Create a dummy RTCSctpTransport object and the 'maxMessageSize'
      // attribute.
      var sctp = {};
      Object.defineProperty(sctp, 'maxMessageSize', {
        get: function get() {
          return maxMessageSize;
        }
      });
      this._sctp = sctp;
    }

    return origSetRemoteDescription.apply(this, arguments);
  };
}

function shimSendThrowTypeError(window) {
  if (!(window.RTCPeerConnection && 'createDataChannel' in window.RTCPeerConnection.prototype)) {
    return;
  }

  // Note: Although Firefox >= 57 has a native implementation, the maximum
  //       message size can be reset for all data channels at a later stage.
  //       See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831

  function wrapDcSend(dc, pc) {
    var origDataChannelSend = dc.send;
    dc.send = function () {
      var data = arguments[0];
      var length = data.length || data.size || data.byteLength;
      if (dc.readyState === 'open' && pc.sctp && length > pc.sctp.maxMessageSize) {
        throw new TypeError('Message too large (can send a maximum of ' + pc.sctp.maxMessageSize + ' bytes)');
      }
      return origDataChannelSend.apply(dc, arguments);
    };
  }
  var origCreateDataChannel = window.RTCPeerConnection.prototype.createDataChannel;
  window.RTCPeerConnection.prototype.createDataChannel = function () {
    var dataChannel = origCreateDataChannel.apply(this, arguments);
    wrapDcSend(dataChannel, this);
    return dataChannel;
  };
  utils.wrapPeerConnectionEvent(window, 'datachannel', function (e) {
    wrapDcSend(e.channel, e.target);
    return e;
  });
}

/* shims RTCConnectionState by pretending it is the same as iceConnectionState.
 * See https://bugs.chromium.org/p/webrtc/issues/detail?id=6145#c12
 * for why this is a valid hack in Chrome. In Firefox it is slightly incorrect
 * since DTLS failures would be hidden. See
 * https://bugzilla.mozilla.org/show_bug.cgi?id=1265827
 * for the Firefox tracking bug.
 */
function shimConnectionState(window) {
  if (!window.RTCPeerConnection || 'connectionState' in window.RTCPeerConnection.prototype) {
    return;
  }
  var proto = window.RTCPeerConnection.prototype;
  Object.defineProperty(proto, 'connectionState', {
    get: function get() {
      return {
        completed: 'connected',
        checking: 'connecting'
      }[this.iceConnectionState] || this.iceConnectionState;
    },

    enumerable: true,
    configurable: true
  });
  Object.defineProperty(proto, 'onconnectionstatechange', {
    get: function get() {
      return this._onconnectionstatechange || null;
    },
    set: function set(cb) {
      if (this._onconnectionstatechange) {
        this.removeEventListener('connectionstatechange', this._onconnectionstatechange);
        delete this._onconnectionstatechange;
      }
      if (cb) {
        this.addEventListener('connectionstatechange', this._onconnectionstatechange = cb);
      }
    },

    enumerable: true,
    configurable: true
  });

  ['setLocalDescription', 'setRemoteDescription'].forEach(function (method) {
    var origMethod = proto[method];
    proto[method] = function () {
      if (!this._connectionstatechangepoly) {
        this._connectionstatechangepoly = function (e) {
          var pc = e.target;
          if (pc._lastConnectionState !== pc.connectionState) {
            pc._lastConnectionState = pc.connectionState;
            var newEvent = new Event('connectionstatechange', e);
            pc.dispatchEvent(newEvent);
          }
          return e;
        };
        this.addEventListener('iceconnectionstatechange', this._connectionstatechangepoly);
      }
      return origMethod.apply(this, arguments);
    };
  });
}

},{"./utils":15,"sdp":17}],7:[function(require,module,exports){
/*
 *  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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;

var _getusermedia = require('./getusermedia');

Object.defineProperty(exports, 'shimGetUserMedia', {
  enumerable: true,
  get: function get() {
    return _getusermedia.shimGetUserMedia;
  }
});

var _getdisplaymedia = require('./getdisplaymedia');

Object.defineProperty(exports, 'shimGetDisplayMedia', {
  enumerable: true,
  get: function get() {
    return _getdisplaymedia.shimGetDisplayMedia;
  }
});
exports.shimPeerConnection = shimPeerConnection;
exports.shimReplaceTrack = shimReplaceTrack;

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

var utils = _interopRequireWildcard(_utils);

var _filtericeservers = require('./filtericeservers');

var _rtcpeerconnectionShim = require('rtcpeerconnection-shim');

var _rtcpeerconnectionShim2 = _interopRequireDefault(_rtcpeerconnectionShim);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

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

  if (window.RTCIceGatherer) {
    if (!window.RTCIceCandidate) {
      window.RTCIceCandidate = function (args) {
        return args;
      };
    }
    if (!window.RTCSessionDescription) {
      window.RTCSessionDescription = function (args) {
        return args;
      };
    }
    // this adds an additional event listener to MediaStrackTrack that signals
    // when a tracks enabled property was changed. Workaround for a bug in
    // addStream, see below. No longer required in 15025+
    if (browserDetails.version < 15025) {
      var origMSTEnabled = Object.getOwnPropertyDescriptor(window.MediaStreamTrack.prototype, 'enabled');
      Object.defineProperty(window.MediaStreamTrack.prototype, 'enabled', {
        set: function set(value) {
          origMSTEnabled.set.call(this, value);
          var ev = new Event('enabled');
          ev.enabled = value;
          this.dispatchEvent(ev);
        }
      });
    }
  }

  // ORTC defines the DTMF sender a bit different.
  // https://github.com/w3c/ortc/issues/714
  if (window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
    Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
      get: function get() {
        if (this._dtmf === undefined) {
          if (this.track.kind === 'audio') {
            this._dtmf = new window.RTCDtmfSender(this);
          } else if (this.track.kind === 'video') {
            this._dtmf = null;
          }
        }
        return this._dtmf;
      }
    });
  }
  // Edge currently only implements the RTCDtmfSender, not the
  // RTCDTMFSender alias. See http://draft.ortc.org/#rtcdtmfsender2*
  if (window.RTCDtmfSender && !window.RTCDTMFSender) {
    window.RTCDTMFSender = window.RTCDtmfSender;
  }

  var RTCPeerConnectionShim = (0, _rtcpeerconnectionShim2.default)(window, browserDetails.version);
  window.RTCPeerConnection = function (config) {
    if (config && config.iceServers) {
      config.iceServers = (0, _filtericeservers.filterIceServers)(config.iceServers, browserDetails.version);
      utils.log('ICE servers after filtering:', config.iceServers);
    }
    return new RTCPeerConnectionShim(config);
  };
  window.RTCPeerConnection.prototype = RTCPeerConnectionShim.prototype;
}

function shimReplaceTrack(window) {
  // ORTC has replaceTrack -- https://github.com/w3c/ortc/issues/614
  if (window.RTCRtpSender && !('replaceTrack' in window.RTCRtpSender.prototype)) {
    window.RTCRtpSender.prototype.replaceTrack = window.RTCRtpSender.prototype.setTrack;
  }
}

},{"../utils":15,"./filtericeservers":8,"./getdisplaymedia":9,"./getusermedia":10,"rtcpeerconnection-shim":16}],8:[function(require,module,exports){
/*
 *  Copyright (c) 2018 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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.filterIceServers = filterIceServers;

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

var utils = _interopRequireWildcard(_utils);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

// Edge does not like
// 1) stun: filtered after 14393 unless ?transport=udp is present
// 2) turn: that does not have all of turn:host:port?transport=udp
// 3) turn: with ipv6 addresses
// 4) turn: occurring muliple times
function filterIceServers(iceServers, edgeVersion) {
  var hasTurn = false;
  iceServers = JSON.parse(JSON.stringify(iceServers));
  return iceServers.filter(function (server) {
    if (server && (server.urls || server.url)) {
      var urls = server.urls || server.url;
      if (server.url && !server.urls) {
        utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
      }
      var isString = typeof urls === 'string';
      if (isString) {
        urls = [urls];
      }
      urls = urls.filter(function (url) {
        // filter STUN unconditionally.
        if (url.indexOf('stun:') === 0) {
          return false;
        }

        var validTurn = url.startsWith('turn') && !url.startsWith('turn:[') && url.includes('transport=udp');
        if (validTurn && !hasTurn) {
          hasTurn = true;
          return true;
        }
        return validTurn && !hasTurn;
      });

      delete server.url;
      server.urls = isString ? urls[0] : urls;
      return !!urls.length;
    }
  });
}

},{"../utils":15}],9:[function(require,module,exports){
/*
 *  Copyright (c) 2018 The adapter.js 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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.shimGetDisplayMedia = shimGetDisplayMedia;
function shimGetDisplayMedia(window) {
  if (!('getDisplayMedia' in window.navigator)) {
    return;
  }
  if (!window.navigator.mediaDevices) {
    return;
  }
  if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
    return;
  }
  window.navigator.mediaDevices.getDisplayMedia = window.navigator.getDisplayMedia.bind(window.navigator.mediaDevices);
}

},{}],10:[function(require,module,exports){
/*
 *  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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.shimGetUserMedia = shimGetUserMedia;
function shimGetUserMedia(window) {
  var navigator = window && window.navigator;

  var shimError_ = function shimError_(e) {
    return {
      name: { PermissionDeniedError: 'NotAllowedError' }[e.name] || e.name,
      message: e.message,
      constraint: e.constraint,
      toString: function toString() {
        return this.name;
      }
    };
  };

  // getUserMedia error shim.
  var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
  navigator.mediaDevices.getUserMedia = function (c) {
    return origGetUserMedia(c).catch(function (e) {
      return Promise.reject(shimError_(e));
    });
  };
}

},{}],11:[function(require,module,exports){
/*
 *  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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

var _getusermedia = require('./getusermedia');

Object.defineProperty(exports, 'shimGetUserMedia', {
  enumerable: true,
  get: function get() {
    return _getusermedia.shimGetUserMedia;
  }
});

var _getdisplaymedia = require('./getdisplaymedia');

Object.defineProperty(exports, 'shimGetDisplayMedia', {
  enumerable: true,
  get: function get() {
    return _getdisplaymedia.shimGetDisplayMedia;
  }
});
exports.shimOnTrack = shimOnTrack;
exports.shimPeerConnection = shimPeerConnection;
exports.shimSenderGetStats = shimSenderGetStats;
exports.shimReceiverGetStats = shimReceiverGetStats;
exports.shimRemoveStream = shimRemoveStream;
exports.shimRTCDataChannel = shimRTCDataChannel;

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

var utils = _interopRequireWildcard(_utils);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

function shimOnTrack(window) {
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCTrackEvent && 'receiver' in window.RTCTrackEvent.prototype && !('transceiver' in window.RTCTrackEvent.prototype)) {
    Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
      get: function get() {
        return { receiver: this.receiver };
      }
    });
  }
}

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

  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !(window.RTCPeerConnection || window.mozRTCPeerConnection)) {
    return; // probably media.peerconnection.enabled=false in about:config
  }
  if (!window.RTCPeerConnection && window.mozRTCPeerConnection) {
    // very basic support for old versions.
    window.RTCPeerConnection = window.mozRTCPeerConnection;
  }

  // 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);
  };

  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 < 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);
  };
}

function shimSenderGetStats(window) {
  if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
    return;
  }
  if (window.RTCRtpSender && 'getStats' in window.RTCRtpSender.prototype) {
    return;
  }
  var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
  if (origGetSenders) {
    window.RTCPeerConnection.prototype.getSenders = function () {
      var _this = this;

      var senders = origGetSenders.apply(this, []);
      senders.forEach(function (sender) {
        return sender._pc = _this;
      });
      return senders;
    };
  }

  var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
  if (origAddTrack) {
    window.RTCPeerConnection.prototype.addTrack = function () {
      var sender = origAddTrack.apply(this, arguments);
      sender._pc = this;
      return sender;
    };
  }
  window.RTCRtpSender.prototype.getStats = function () {
    return this.track ? this._pc.getStats(this.track) : Promise.resolve(new Map());
  };
}

function shimReceiverGetStats(window) {
  if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
    return;
  }
  if (window.RTCRtpSender && 'getStats' in window.RTCRtpReceiver.prototype) {
    return;
  }
  var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
  if (origGetReceivers) {
    window.RTCPeerConnection.prototype.getReceivers = function () {
      var _this2 = this;

      var receivers = origGetReceivers.apply(this, []);
      receivers.forEach(function (receiver) {
        return receiver._pc = _this2;
      });
      return receivers;
    };
  }
  utils.wrapPeerConnectionEvent(window, 'track', function (e) {
    e.receiver._pc = e.srcElement;
    return e;
  });
  window.RTCRtpReceiver.prototype.getStats = function () {
    return this._pc.getStats(this.track);
  };
}

function shimRemoveStream(window) {
  if (!window.RTCPeerConnection || 'removeStream' in window.RTCPeerConnection.prototype) {
    return;
  }
  window.RTCPeerConnection.prototype.removeStream = function (stream) {
    var _this3 = this;

    utils.deprecated('removeStream', 'removeTrack');
    this.getSenders().forEach(function (sender) {
      if (sender.track && stream.getTracks().includes(sender.track)) {
        _this3.removeTrack(sender);
      }
    });
  };
}

function shimRTCDataChannel(window) {
  // rename DataChannel to RTCDataChannel (native fix in FF60):
  // https://bugzilla.mozilla.org/show_bug.cgi?id=1173851
  if (window.DataChannel && !window.RTCDataChannel) {
    window.RTCDataChannel = window.DataChannel;
  }
}

},{"../utils":15,"./getdisplaymedia":12,"./getusermedia":13}],12:[function(require,module,exports){
/*
 *  Copyright (c) 2018 The adapter.js 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';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.shimGetDisplayMedia = shimGetDisplayMedia;
function shimGetDisplayMedia(window, preferredMediaSource) {
  if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
    return;
  }
  if (!window.navigator.mediaDevices) {
    return;
  }
  window.navigator.mediaDevices.getDisplayMedia = function (constraints) {
    if (!(constraints && constraints.video)) {
      var err = new DOMException('getDisplayMedia without video ' + 'constraints is undefined');
      err.name = 'NotFoundError';
      // from https://heycam.github.io/webidl/#idl-DOMException-error-names
      err.code = 8;
      return Promise.reject(err);
    }
    if (constraints.video === true) {
      constraints.video = { mediaSource: preferredMediaSource };
    } else {
      constraints.video.mediaSource = preferredMediaSource;
    }
    return window.navigator.mediaDevices.getUserMedia(constraints);
  };
}

},{}],13:[function(require,module,exports){
/*
 *  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';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

exports.shimGetUserMedia = shimGetUserMedia;

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

var utils = _interopRequireWildcard(_utils);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

function shimGetUserMedia(window) {
  var browserDetails = utils.detectBrowser(window);
  var navigator = window && window.navigator;
  var MediaStreamTrack = window && window.MediaStreamTrack;

  navigator.getUserMedia = function (constraints, onSuccess, onError) {
    // Replace Firefox 44+'s deprecation warning with unprefixed version.
    utils.deprecated('navigator.getUserMedia', 'navigator.mediaDevices.getUserMedia');
    navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
  };

  if (!(browserDetails.version > 55 && 'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
    var remap = function remap(obj, a, b) {
      if (a in obj && !(b in obj)) {
        obj[b] = obj[a];
        delete obj[a];
      }
    };

    var nativeGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
    navigator.mediaDevices.getUserMedia = function (c) {
      if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object' && _typeof(c.audio) === 'object') {
        c = JSON.parse(JSON.stringify(c));
        remap(c.audio, 'autoGainControl', 'mozAutoGainControl');
        remap(c.audio, 'noiseSuppression', 'mozNoiseSuppression');
      }
      return nativeGetUserMedia(c);
    };

    if (MediaStreamTrack && MediaStreamTrack.prototype.getSettings) {
      var nativeGetSettings = MediaStreamTrack.prototype.getSettings;
      MediaStreamTrack.prototype.getSettings = function () {
        var obj = nativeGetSettings.apply(this, arguments);
        remap(obj, 'mozAutoGainControl', 'autoGainControl');
        remap(obj, 'mozNoiseSuppression', 'noiseSuppression');
        return obj;
      };
    }

    if (MediaStreamTrack && MediaStreamTrack.prototype.applyConstraints) {
      var nativeApplyConstraints = MediaStreamTrack.prototype.applyConstraints;
      MediaStreamTrack.prototype.applyConstraints = function (c) {
        if (this.kind === 'audio' && (typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object') {
          c = JSON.parse(JSON.stringify(c));
          remap(c, 'autoGainControl', 'mozAutoGainControl');
          remap(c, 'noiseSuppression', 'mozNoiseSuppression');
        }
        return nativeApplyConstraints.apply(this, [c]);
      };
    }
  }
}

},{"../utils":15}],14:[function(require,module,exports){
/*
 *  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.
 */
'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

exports.shimLocalStreamsAPI = shimLocalStreamsAPI;
exports.shimRemoteStreamsAPI = shimRemoteStreamsAPI;
exports.shimCallbacksAPI = shimCallbacksAPI;
exports.shimGetUserMedia = shimGetUserMedia;
exports.shimRTCIceServerUrls = shimRTCIceServerUrls;
exports.shimTrackEventTransceiver = shimTrackEventTransceiver;
exports.shimCreateOfferLegacy = shimCreateOfferLegacy;

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

var utils = _interopRequireWildcard(_utils);

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

function shimLocalStreamsAPI(window) {
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
    return;
  }
  if (!('getLocalStreams' in window.RTCPeerConnection.prototype)) {
    window.RTCPeerConnection.prototype.getLocalStreams = function () {
      if (!this._localStreams) {
        this._localStreams = [];
      }
      return this._localStreams;
    };
  }
  if (!('addStream' in window.RTCPeerConnection.prototype)) {
    var _addTrack = window.RTCPeerConnection.prototype.addTrack;
    window.RTCPeerConnection.prototype.addStream = function (stream) {
      var _this = this;

      if (!this._localStreams) {
        this._localStreams = [];
      }
      if (!this._localStreams.includes(stream)) {
        this._localStreams.push(stream);
      }
      stream.getTracks().forEach(function (track) {
        return _addTrack.call(_this, track, stream);
      });
    };

    window.RTCPeerConnection.prototype.addTrack = function (track, stream) {
      if (stream) {
        if (!this._localStreams) {
          this._localStreams = [stream];
        } else if (!this._localStreams.includes(stream)) {
          this._localStreams.push(stream);
        }
      }
      return _addTrack.call(this, track, stream);
    };
  }
  if (!('removeStream' in window.RTCPeerConnection.prototype)) {
    window.RTCPeerConnection.prototype.removeStream = function (stream) {
      var _this2 = this;

      if (!this._localStreams) {
        this._localStreams = [];
      }
      var index = this._localStreams.indexOf(stream);
      if (index === -1) {
        return;
      }
      this._localStreams.splice(index, 1);
      var tracks = stream.getTracks();
      this.getSenders().forEach(function (sender) {
        if (tracks.includes(sender.track)) {
          _this2.removeTrack(sender);
        }
      });
    };
  }
}

function shimRemoteStreamsAPI(window) {
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
    return;
  }
  if (!('getRemoteStreams' in window.RTCPeerConnection.prototype)) {
    window.RTCPeerConnection.prototype.getRemoteStreams = function () {
      return this._remoteStreams ? this._remoteStreams : [];
    };
  }
  if (!('onaddstream' in window.RTCPeerConnection.prototype)) {
    Object.defineProperty(window.RTCPeerConnection.prototype, 'onaddstream', {
      get: function get() {
        return this._onaddstream;
      },
      set: function set(f) {
        var _this3 = this;

        if (this._onaddstream) {
          this.removeEventListener('addstream', this._onaddstream);
          this.removeEventListener('track', this._onaddstreampoly);
        }
        this.addEventListener('addstream', this._onaddstream = f);
        this.addEventListener('track', this._onaddstreampoly = function (e) {
          e.streams.forEach(function (stream) {
            if (!_this3._remoteStreams) {
              _this3._remoteStreams = [];
            }
            if (_this3._remoteStreams.includes(stream)) {
              return;
            }
            _this3._remoteStreams.push(stream);
            var event = new Event('addstream');
            event.stream = stream;
            _this3.dispatchEvent(event);
          });
        });
      }
    });
    var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
    window.RTCPeerConnection.prototype.setRemoteDescription = function () {
      var pc = this;
      if (!this._onaddstreampoly) {
        this.addEventListener('track', this._onaddstreampoly = function (e) {
          e.streams.forEach(function (stream) {
            if (!pc._remoteStreams) {
              pc._remoteStreams = [];
            }
            if (pc._remoteStreams.indexOf(stream) >= 0) {
              return;
            }
            pc._remoteStreams.push(stream);
            var event = new Event('addstream');
            event.stream = stream;
            pc.dispatchEvent(event);
          });
        });
      }
      return origSetRemoteDescription.apply(pc, arguments);
    };
  }
}

function shimCallbacksAPI(window) {
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
    return;
  }
  var prototype = window.RTCPeerConnection.prototype;
  var createOffer = prototype.createOffer;
  var createAnswer = prototype.createAnswer;
  var setLocalDescription = prototype.setLocalDescription;
  var setRemoteDescription = prototype.setRemoteDescription;
  var addIceCandidate = prototype.addIceCandidate;

  prototype.createOffer = function (successCallback, failureCallback) {
    var options = arguments.length >= 2 ? arguments[2] : arguments[0];
    var promise = createOffer.apply(this, [options]);
    if (!failureCallback) {
      return promise;
    }
    promise.then(successCallback, failureCallback);
    return Promise.resolve();
  };

  prototype.createAnswer = function (successCallback, failureCallback) {
    var options = arguments.length >= 2 ? arguments[2] : arguments[0];
    var promise = createAnswer.apply(this, [options]);
    if (!failureCallback) {
      return promise;
    }
    promise.then(successCallback, failureCallback);
    return Promise.resolve();
  };

  var withCallback = function withCallback(description, successCallback, failureCallback) {
    var promise = setLocalDescription.apply(this, [description]);
    if (!failureCallback) {
      return promise;
    }
    promise.then(successCallback, failureCallback);
    return Promise.resolve();
  };
  prototype.setLocalDescription = withCallback;

  withCallback = function withCallback(description, successCallback, failureCallback) {
    var promise = setRemoteDescription.apply(this, [description]);
    if (!failureCallback) {
      return promise;
    }
    promise.then(successCallback, failureCallback);
    return Promise.resolve();
  };
  prototype.setRemoteDescription = withCallback;

  withCallback = function withCallback(candidate, successCallback, failureCallback) {
    var promise = addIceCandidate.apply(this, [candidate]);
    if (!failureCallback) {
      return promise;
    }
    promise.then(successCallback, failureCallback);
    return Promise.resolve();
  };
  prototype.addIceCandidate = withCallback;
}

function shimGetUserMedia(window) {
  var navigator = window && window.navigator;

  if (!navigator.getUserMedia && navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
    navigator.getUserMedia = function (constraints, cb, errcb) {
      navigator.mediaDevices.getUserMedia(constraints).then(cb, errcb);
    }.bind(navigator);
  }
}

function shimRTCIceServerUrls(window) {
  // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
  var OrigPeerConnection = window.RTCPeerConnection;
  window.RTCPeerConnection = function (pcConfig, pcConstraints) {
    if (pcConfig && pcConfig.iceServers) {
      var newIceServers = [];
      for (var i = 0; i < pcConfig.iceServers.length; i++) {
        var server = pcConfig.iceServers[i];
        if (!server.hasOwnProperty('urls') && server.hasOwnProperty('url')) {
          utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
          server = JSON.parse(JSON.stringify(server));
          server.urls = server.url;
          delete server.url;
          newIceServers.push(server);
        } else {
          newIceServers.push(pcConfig.iceServers[i]);
        }
      }
      pcConfig.iceServers = newIceServers;
    }
    return new OrigPeerConnection(pcConfig, pcConstraints);
  };
  window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
  // wrap static methods. Currently just generateCertificate.
  if ('generateCertificate' in window.RTCPeerConnection) {
    Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
      get: function get() {
        return OrigPeerConnection.generateCertificate;
      }
    });
  }
}

function shimTrackEventTransceiver(window) {
  // Add event.transceiver member over deprecated event.receiver
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && 'receiver' in window.RTCTrackEvent.prototype &&
  // can't check 'transceiver' in window.RTCTrackEvent.prototype, as it is
  // defined for some reason even when window.RTCTransceiver is not.
  !window.RTCTransceiver) {
    Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
      get: function get() {
        return { receiver: this.receiver };
      }
    });
  }
}

function shimCreateOfferLegacy(window) {
  var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
  window.RTCPeerConnection.prototype.createOffer = function (offerOptions) {
    if (offerOptions) {
      if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
        // support bit values
        offerOptions.offerToReceiveAudio = !!offerOptions.offerToReceiveAudio;
      }
      var audioTransceiver = this.getTransceivers().find(function (transceiver) {
        return transceiver.sender.track && transceiver.sender.track.kind === 'audio';
      });
      if (offerOptions.offerToReceiveAudio === false && audioTransceiver) {
        if (audioTransceiver.direction === 'sendrecv') {
          if (audioTransceiver.setDirection) {
            audioTransceiver.setDirection('sendonly');
          } else {
            audioTransceiver.direction = 'sendonly';
          }
        } else if (audioTransceiver.direction === 'recvonly') {
          if (audioTransceiver.setDirection) {
            audioTransceiver.setDirection('inactive');
          } else {
            audioTransceiver.direction = 'inactive';
          }
        }
      } else if (offerOptions.offerToReceiveAudio === true && !audioTransceiver) {
        this.addTransceiver('audio');
      }

      if (typeof offerOptions.offerToReceiveVideo !== 'undefined') {
        // support bit values
        offerOptions.offerToReceiveVideo = !!offerOptions.offerToReceiveVideo;
      }
      var videoTransceiver = this.getTransceivers().find(function (transceiver) {
        return transceiver.sender.track && transceiver.sender.track.kind === 'video';
      });
      if (offerOptions.offerToReceiveVideo === false && videoTransceiver) {
        if (videoTransceiver.direction === 'sendrecv') {
          if (videoTransceiver.setDirection) {
            videoTransceiver.setDirection('sendonly');
          } else {
            videoTransceiver.direction = 'sendonly';
          }
        } else if (videoTransceiver.direction === 'recvonly') {
          if (videoTransceiver.setDirection) {
            videoTransceiver.setDirection('inactive');
          } else {
            videoTransceiver.direction = 'inactive';
          }
        }
      } else if (offerOptions.offerToReceiveVideo === true && !videoTransceiver) {
        this.addTransceiver('video');
      }
    }
    return origCreateOffer.apply(this, arguments);
  };
}

},{"../utils":15}],15:[function(require,module,exports){
/*
 *  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';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

exports.extractVersion = extractVersion;
exports.wrapPeerConnectionEvent = wrapPeerConnectionEvent;
exports.disableLog = disableLog;
exports.disableWarnings = disableWarnings;
exports.log = log;
exports.deprecated = deprecated;
exports.detectBrowser = detectBrowser;
var logDisabled_ = true;
var deprecationWarnings_ = true;

/**
 * Extract browser version out of the provided user agent string.
 *
 * @param {!string} uastring userAgent string.
 * @param {!string} expr Regular expression used as match criteria.
 * @param {!number} pos position in the version string to be returned.
 * @return {!number} browser version.
 */
function extractVersion(uastring, expr, pos) {
  var match = uastring.match(expr);
  return match && match.length >= pos && parseInt(match[pos], 10);
}

// Wraps the peerconnection event eventNameToWrap in a function
// which returns the modified event object (or false to prevent
// the event).
function wrapPeerConnectionEvent(window, eventNameToWrap, wrapper) {
  if (!window.RTCPeerConnection) {
    return;
  }
  var proto = window.RTCPeerConnection.prototype;
  var nativeAddEventListener = proto.addEventListener;
  proto.addEventListener = function (nativeEventName, cb) {
    if (nativeEventName !== eventNameToWrap) {
      return nativeAddEventListener.apply(this, arguments);
    }
    var wrappedCallback = function wrappedCallback(e) {
      var modifiedEvent = wrapper(e);
      if (modifiedEvent) {
        cb(modifiedEvent);
      }
    };
    this._eventMap = this._eventMap || {};
    this._eventMap[cb] = wrappedCallback;
    return nativeAddEventListener.apply(this, [nativeEventName, wrappedCallback]);
  };

  var nativeRemoveEventListener = proto.removeEventListener;
  proto.removeEventListener = function (nativeEventName, cb) {
    if (nativeEventName !== eventNameToWrap || !this._eventMap || !this._eventMap[cb]) {
      return nativeRemoveEventListener.apply(this, arguments);
    }
    var unwrappedCb = this._eventMap[cb];
    delete this._eventMap[cb];
    return nativeRemoveEventListener.apply(this, [nativeEventName, unwrappedCb]);
  };

  Object.defineProperty(proto, 'on' + eventNameToWrap, {
    get: function get() {
      return this['_on' + eventNameToWrap];
    },
    set: function set(cb) {
      if (this['_on' + eventNameToWrap]) {
        this.removeEventListener(eventNameToWrap, this['_on' + eventNameToWrap]);
        delete this['_on' + eventNameToWrap];
      }
      if (cb) {
        this.addEventListener(eventNameToWrap, this['_on' + eventNameToWrap] = cb);
      }
    },

    enumerable: true,
    configurable: true
  });
}

function disableLog(bool) {
  if (typeof bool !== 'boolean') {
    return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.');
  }
  logDisabled_ = bool;
  return bool ? 'adapter.js logging disabled' : 'adapter.js logging enabled';
}

/**
 * Disable or enable deprecation warnings
 * @param {!boolean} bool set to true to disable warnings.
 */
function disableWarnings(bool) {
  if (typeof bool !== 'boolean') {
    return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.');
  }
  deprecationWarnings_ = !bool;
  return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled');
}

function log() {
  if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object') {
    if (logDisabled_) {
      return;
    }
    if (typeof console !== 'undefined' && typeof console.log === 'function') {
      console.log.apply(console, arguments);
    }
  }
}

/**
 * Shows a deprecation warning suggesting the modern and spec-compatible API.
 */
function deprecated(oldMethod, newMethod) {
  if (!deprecationWarnings_) {
    return;
  }
  console.warn(oldMethod + ' is deprecated, please use ' + newMethod + ' instead.');
}

/**
 * Browser detector.
 *
 * @return {object} result containing browser and version
 *     properties.
 */
function detectBrowser(window) {
  var navigator = window.navigator;

  // Returned result object.

  var result = { browser: null, version: null };

  // Fail early if it's not a browser
  if (typeof window === 'undefined' || !window.navigator) {
    result.browser = 'Not a browser.';
    return result;
  }

  if (navigator.mozGetUserMedia) {
    // Firefox.
    result.browser = 'firefox';
    result.version = extractVersion(navigator.userAgent, /Firefox\/(\d+)\./, 1);
  } else if (navigator.webkitGetUserMedia) {
    // Chrome, Chromium, Webview, Opera.
    // Version matches Chrome/WebRTC version.
    result.browser = 'chrome';
    result.version = extractVersion(navigator.userAgent, /Chrom(e|ium)\/(\d+)\./, 2);
  } else if (navigator.mediaDevices && navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) {
    // Edge.
    result.browser = 'edge';
    result.version = extractVersion(navigator.userAgent, /Edge\/(\d+).(\d+)$/, 2);
  } else if (window.RTCPeerConnection && navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) {
    // Safari.
    result.browser = 'safari';
    result.version = extractVersion(navigator.userAgent, /AppleWebKit\/(\d+)\./, 1);
  } else {
    // Default fallthrough: not supported.
    result.browser = 'Not a supported browser.';
    return result;
  }

  return result;
}

},{}],16:[function(require,module,exports){
/*
 *  Copyright (c) 2017 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 SDPUtils = require('sdp');

function fixStatsType(stat) {
  return {
    inboundrtp: 'inbound-rtp',
    outboundrtp: 'outbound-rtp',
    candidatepair: 'candidate-pair',
    localcandidate: 'local-candidate',
    remotecandidate: 'remote-candidate'
  }[stat.type] || stat.type;
}

function writeMediaSection(transceiver, caps, type, stream, dtlsRole) {
  var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

  // Map ICE parameters (ufrag, pwd) to SDP.
  sdp += SDPUtils.writeIceParameters(
      transceiver.iceGatherer.getLocalParameters());

  // Map DTLS parameters to SDP.
  sdp += SDPUtils.writeDtlsParameters(
      transceiver.dtlsTransport.getLocalParameters(),
      type === 'offer' ? 'actpass' : dtlsRole || 'active');

  sdp += 'a=mid:' + transceiver.mid + '\r\n';

  if (transceiver.rtpSender && transceiver.rtpReceiver) {
    sdp += 'a=sendrecv\r\n';
  } else if (transceiver.rtpSender) {
    sdp += 'a=sendonly\r\n';
  } else if (transceiver.rtpReceiver) {
    sdp += 'a=recvonly\r\n';
  } else {
    sdp += 'a=inactive\r\n';
  }

  if (transceiver.rtpSender) {
    var trackId = transceiver.rtpSender._initialTrackId ||
        transceiver.rtpSender.track.id;
    transceiver.rtpSender._initialTrackId = trackId;
    // spec.
    var msid = 'msid:' + (stream ? stream.id : '-') + ' ' +
        trackId + '\r\n';
    sdp += 'a=' + msid;
    // for Chrome. Legacy should no longer be required.
    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
        ' ' + msid;

    // RTX
    if (transceiver.sendEncodingParameters[0].rtx) {
      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
          ' ' + msid;
      sdp += 'a=ssrc-group:FID ' +
          transceiver.sendEncodingParameters[0].ssrc + ' ' +
          transceiver.sendEncodingParameters[0].rtx.ssrc +
          '\r\n';
    }
  }
  // FIXME: this should be written by writeRtpDescription.
  sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
      ' cname:' + SDPUtils.localCName + '\r\n';
  if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
        ' cname:' + SDPUtils.localCName + '\r\n';
  }
  return sdp;
}

// Edge does not like
// 1) stun: filtered after 14393 unless ?transport=udp is present
// 2) turn: that does not have all of turn:host:port?transport=udp
// 3) turn: with ipv6 addresses
// 4) turn: occurring muliple times
function filterIceServers(iceServers, edgeVersion) {
  var hasTurn = false;
  iceServers = JSON.parse(JSON.stringify(iceServers));
  return iceServers.filter(function(server) {
    if (server && (server.urls || server.url)) {
      var urls = server.urls || server.url;
      if (server.url && !server.urls) {
        console.warn('RTCIceServer.url is deprecated! Use urls instead.');
      }
      var isString = typeof urls === 'string';
      if (isString) {
        urls = [urls];
      }
      urls = urls.filter(function(url) {
        var validTurn = url.indexOf('turn:') === 0 &&
            url.indexOf('transport=udp') !== -1 &&
            url.indexOf('turn:[') === -1 &&
            !hasTurn;

        if (validTurn) {
          hasTurn = true;
          return true;
        }
        return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
            url.indexOf('?transport=udp') === -1;
      });

      delete server.url;
      server.urls = isString ? urls[0] : urls;
      return !!urls.length;
    }
  });
}

// Determines the intersection of local and remote capabilities.
function getCommonCapabilities(localCapabilities, remoteCapabilities) {
  var commonCapabilities = {
    codecs: [],
    headerExtensions: [],
    fecMechanisms: []
  };

  var findCodecByPayloadType = function(pt, codecs) {
    pt = parseInt(pt, 10);
    for (var i = 0; i < codecs.length; i++) {
      if (codecs[i].payloadType === pt ||
          codecs[i].preferredPayloadType === pt) {
        return codecs[i];
      }
    }
  };

  var rtxCapabilityMatches = function(lRtx, rRtx, lCodecs, rCodecs) {
    var lCodec = findCodecByPayloadType(lRtx.parameters.apt, lCodecs);
    var rCodec = findCodecByPayloadType(rRtx.parameters.apt, rCodecs);
    return lCodec && rCodec &&
        lCodec.name.toLowerCase() === rCodec.name.toLowerCase();
  };

  localCapabilities.codecs.forEach(function(lCodec) {
    for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
      var rCodec = remoteCapabilities.codecs[i];
      if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
          lCodec.clockRate === rCodec.clockRate) {
        if (lCodec.name.toLowerCase() === 'rtx' &&
            lCodec.parameters && rCodec.parameters.apt) {
          // for RTX we need to find the local rtx that has a apt
          // which points to the same local codec as the remote one.
          if (!rtxCapabilityMatches(lCodec, rCodec,
              localCapabilities.codecs, remoteCapabilities.codecs)) {
            continue;
          }
        }
        rCodec = JSON.parse(JSON.stringify(rCodec)); // deepcopy
        // number of channels is the highest common number of channels
        rCodec.numChannels = Math.min(lCodec.numChannels,
            rCodec.numChannels);
        // push rCodec so we reply with offerer payload type
        commonCapabilities.codecs.push(rCodec);

        // determine common feedback mechanisms
        rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
          for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
            if (lCodec.rtcpFeedback[j].type === fb.type &&
                lCodec.rtcpFeedback[j].parameter === fb.parameter) {
              return true;
            }
          }
          return false;
        });
        // FIXME: also need to determine .parameters
        //  see https://github.com/openpeer/ortc/issues/569
        break;
      }
    }
  });

  localCapabilities.headerExtensions.forEach(function(lHeaderExtension) {
    for (var i = 0; i < remoteCapabilities.headerExtensions.length;
         i++) {
      var rHeaderExtension = remoteCapabilities.headerExtensions[i];
      if (lHeaderExtension.uri === rHeaderExtension.uri) {
        commonCapabilities.headerExtensions.push(rHeaderExtension);
        break;
      }
    }
  });

  // FIXME: fecMechanisms
  return commonCapabilities;
}

// is action=setLocalDescription with type allowed in signalingState
function isActionAllowedInSignalingState(action, type, signalingState) {
  return {
    offer: {
      setLocalDescription: ['stable', 'have-local-offer'],
      setRemoteDescription: ['stable', 'have-remote-offer']
    },
    answer: {
      setLocalDescription: ['have-remote-offer', 'have-local-pranswer'],
      setRemoteDescription: ['have-local-offer', 'have-remote-pranswer']
    }
  }[type][action].indexOf(signalingState) !== -1;
}

function maybeAddCandidate(iceTransport, candidate) {
  // Edge's internal representation adds some fields therefore
  // not all fieldѕ are taken into account.
  var alreadyAdded = iceTransport.getRemoteCandidates()
      .find(function(remoteCandidate) {
        return candidate.foundation === remoteCandidate.foundation &&
            candidate.ip === remoteCandidate.ip &&
            candidate.port === remoteCandidate.port &&
            candidate.priority === remoteCandidate.priority &&
            candidate.protocol === remoteCandidate.protocol &&
            candidate.type === remoteCandidate.type;
      });
  if (!alreadyAdded) {
    iceTransport.addRemoteCandidate(candidate);
  }
  return !alreadyAdded;
}


function makeError(name, description) {
  var e = new Error(description);
  e.name = name;
  // legacy error codes from https://heycam.github.io/webidl/#idl-DOMException-error-names
  e.code = {
    NotSupportedError: 9,
    InvalidStateError: 11,
    InvalidAccessError: 15,
    TypeError: undefined,
    OperationError: undefined
  }[name];
  return e;
}

module.exports = function(window, edgeVersion) {
  // https://w3c.github.io/mediacapture-main/#mediastream
  // Helper function to add the track to the stream and
  // dispatch the event ourselves.
  function addTrackToStreamAndFireEvent(track, stream) {
    stream.addTrack(track);
    stream.dispatchEvent(new window.MediaStreamTrackEvent('addtrack',
        {track: track}));
  }

  function removeTrackFromStreamAndFireEvent(track, stream) {
    stream.removeTrack(track);
    stream.dispatchEvent(new window.MediaStreamTrackEvent('removetrack',
        {track: track}));
  }

  function fireAddTrack(pc, track, receiver, streams) {
    var trackEvent = new Event('track');
    trackEvent.track = track;
    trackEvent.receiver = receiver;
    trackEvent.transceiver = {receiver: receiver};
    trackEvent.streams = streams;
    window.setTimeout(function() {
      pc._dispatchEvent('track', trackEvent);
    });
  }

  var RTCPeerConnection = function(config) {
    var pc = this;

    var _eventTarget = document.createDocumentFragment();
    ['addEventListener', 'removeEventListener', 'dispatchEvent']
        .forEach(function(method) {
          pc[method] = _eventTarget[method].bind(_eventTarget);
        });

    this.canTrickleIceCandidates = null;

    this.needNegotiation = false;

    this.localStreams = [];
    this.remoteStreams = [];

    this._localDescription = null;
    this._remoteDescription = null;

    this.signalingState = 'stable';
    this.iceConnectionState = 'new';
    this.connectionState = 'new';
    this.iceGatheringState = 'new';

    config = JSON.parse(JSON.stringify(config || {}));

    this.usingBundle = config.bundlePolicy === 'max-bundle';
    if (config.rtcpMuxPolicy === 'negotiate') {
      throw(makeError('NotSupportedError',
          'rtcpMuxPolicy \'negotiate\' is not supported'));
    } else if (!config.rtcpMuxPolicy) {
      config.rtcpMuxPolicy = 'require';
    }

    switch (config.iceTransportPolicy) {
      case 'all':
      case 'relay':
        break;
      default:
        config.iceTransportPolicy = 'all';
        break;
    }

    switch (config.bundlePolicy) {
      case 'balanced':
      case 'max-compat':
      case 'max-bundle':
        break;
      default:
        config.bundlePolicy = 'balanced';
        break;
    }

    config.iceServers = filterIceServers(config.iceServers || [], edgeVersion);

    this._iceGatherers = [];
    if (config.iceCandidatePoolSize) {
      for (var i = config.iceCandidatePoolSize; i > 0; i--) {
        this._iceGatherers.push(new window.RTCIceGatherer({
          iceServers: config.iceServers,
          gatherPolicy: config.iceTransportPolicy
        }));
      }
    } else {
      config.iceCandidatePoolSize = 0;
    }

    this._config = config;

    // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
    // everything that is needed to describe a SDP m-line.
    this.transceivers = [];

    this._sdpSessionId = SDPUtils.generateSessionId();
    this._sdpSessionVersion = 0;

    this._dtlsRole = undefined; // role for a=setup to use in answers.

    this._isClosed = false;
  };

  Object.defineProperty(RTCPeerConnection.prototype, 'localDescription', {
    configurable: true,
    get: function() {
      return this._localDescription;
    }
  });
  Object.defineProperty(RTCPeerConnection.prototype, 'remoteDescription', {
    configurable: true,
    get: function() {
      return this._remoteDescription;
    }
  });

  // set up event handlers on prototype
  RTCPeerConnection.prototype.onicecandidate = null;
  RTCPeerConnection.prototype.onaddstream = null;
  RTCPeerConnection.prototype.ontrack = null;
  RTCPeerConnection.prototype.onremovestream = null;
  RTCPeerConnection.prototype.onsignalingstatechange = null;
  RTCPeerConnection.prototype.oniceconnectionstatechange = null;
  RTCPeerConnection.prototype.onconnectionstatechange = null;
  RTCPeerConnection.prototype.onicegatheringstatechange = null;
  RTCPeerConnection.prototype.onnegotiationneeded = null;
  RTCPeerConnection.prototype.ondatachannel = null;

  RTCPeerConnection.prototype._dispatchEvent = function(name, event) {
    if (this._isClosed) {
      return;
    }
    this.dispatchEvent(event);
    if (typeof this['on' + name] === 'function') {
      this['on' + name](event);
    }
  };

  RTCPeerConnection.prototype._emitGatheringStateChange = function() {
    var event = new Event('icegatheringstatechange');
    this._dispatchEvent('icegatheringstatechange', event);
  };

  RTCPeerConnection.prototype.getConfiguration = function() {
    return this._config;
  };

  RTCPeerConnection.prototype.getLocalStreams = function() {
    return this.localStreams;
  };

  RTCPeerConnection.prototype.getRemoteStreams = function() {
    return this.remoteStreams;
  };

  // internal helper to create a transceiver object.
  // (which is not yet the same as the WebRTC 1.0 transceiver)
  RTCPeerConnection.prototype._createTransceiver = function(kind, doNotAdd) {
    var hasBundleTransport = this.transceivers.length > 0;
    var transceiver = {
      track: null,
      iceGatherer: null,
      iceTransport: null,
      dtlsTransport: null,
      localCapabilities: null,
      remoteCapabilities: null,
      rtpSender: null,
      rtpReceiver: null,
      kind: kind,
      mid: null,
      sendEncodingParameters: null,
      recvEncodingParameters: null,
      stream: null,
      associatedRemoteMediaStreams: [],
      wantReceive: true
    };
    if (this.usingBundle && hasBundleTransport) {
      transceiver.iceTransport = this.transceivers[0].iceTransport;
      transceiver.dtlsTransport = this.transceivers[0].dtlsTransport;
    } else {
      var transports = this._createIceAndDtlsTransports();
      transceiver.iceTransport = transports.iceTransport;
      transceiver.dtlsTransport = transports.dtlsTransport;
    }
    if (!doNotAdd) {
      this.transceivers.push(transceiver);
    }
    return transceiver;
  };

  RTCPeerConnection.prototype.addTrack = function(track, stream) {
    if (this._isClosed) {
      throw makeError('InvalidStateError',
          'Attempted to call addTrack on a closed peerconnection.');
    }

    var alreadyExists = this.transceivers.find(function(s) {
      return s.track === track;
    });

    if (alreadyExists) {
      throw makeError('InvalidAccessError', 'Track already exists.');
    }

    var transceiver;
    for (var i = 0; i < this.transceivers.length; i++) {
      if (!this.transceivers[i].track &&
          this.transceivers[i].kind === track.kind) {
        transceiver = this.transceivers[i];
      }
    }
    if (!transceiver) {
      transceiver = this._createTransceiver(track.kind);
    }

    this._maybeFireNegotiationNeeded();

    if (this.localStreams.indexOf(stream) === -1) {
      this.localStreams.push(stream);
    }

    transceiver.track = track;
    transceiver.stream = stream;
    transceiver.rtpSender = new window.RTCRtpSender(track,
        transceiver.dtlsTransport);
    return transceiver.rtpSender;
  };

  RTCPeerConnection.prototype.addStream = function(stream) {
    var pc = this;
    if (edgeVersion >= 15025) {
      stream.getTracks().forEach(function(track) {
        pc.addTrack(track, stream);
      });
    } else {
      // Clone is necessary for local demos mostly, attaching directly
      // to two different senders does not work (build 10547).
      // Fixed in 15025 (or earlier)
      var clonedStream = stream.clone();
      stream.getTracks().forEach(function(track, idx) {
        var clonedTrack = clonedStream.getTracks()[idx];
        track.addEventListener('enabled', function(event) {
          clonedTrack.enabled = event.enabled;
        });
      });
      clonedStream.getTracks().forEach(function(track) {
        pc.addTrack(track, clonedStream);
      });
    }
  };

  RTCPeerConnection.prototype.removeTrack = function(sender) {
    if (this._isClosed) {
      throw makeError('InvalidStateError',
          'Attempted to call removeTrack on a closed peerconnection.');
    }

    if (!(sender instanceof window.RTCRtpSender)) {
      throw new TypeError('Argument 1 of RTCPeerConnection.removeTrack ' +
          'does not implement interface RTCRtpSender.');
    }

    var transceiver = this.transceivers.find(function(t) {
      return t.rtpSender === sender;
    });

    if (!transceiver) {
      throw makeError('InvalidAccessError',
          'Sender was not created by this connection.');
    }
    var stream = transceiver.stream;

    transceiver.rtpSender.stop();
    transceiver.rtpSender = null;
    transceiver.track = null;
    transceiver.stream = null;

    // remove the stream from the set of local streams
    var localStreams = this.transceivers.map(function(t) {
      return t.stream;
    });
    if (localStreams.indexOf(stream) === -1 &&
        this.localStreams.indexOf(stream) > -1) {
      this.localStreams.splice(this.localStreams.indexOf(stream), 1);
    }

    this._maybeFireNegotiationNeeded();
  };

  RTCPeerConnection.prototype.removeStream = function(stream) {
    var pc = this;
    stream.getTracks().forEach(function(track) {
      var sender = pc.getSenders().find(function(s) {
        return s.track === track;
      });
      if (sender) {
        pc.removeTrack(sender);
      }
    });
  };

  RTCPeerConnection.prototype.getSenders = function() {
    return this.transceivers.filter(function(transceiver) {
      return !!transceiver.rtpSender;
    })
    .map(function(transceiver) {
      return transceiver.rtpSender;
    });
  };

  RTCPeerConnection.prototype.getReceivers = function() {
    return this.transceivers.filter(function(transceiver) {
      return !!transceiver.rtpReceiver;
    })
    .map(function(transceiver) {
      return transceiver.rtpReceiver;
    });
  };


  RTCPeerConnection.prototype._createIceGatherer = function(sdpMLineIndex,
      usingBundle) {
    var pc = this;
    if (usingBundle && sdpMLineIndex > 0) {
      return this.transceivers[0].iceGatherer;
    } else if (this._iceGatherers.length) {
      return this._iceGatherers.shift();
    }
    var iceGatherer = new window.RTCIceGatherer({
      iceServers: this._config.iceServers,
      gatherPolicy: this._config.iceTransportPolicy
    });
    Object.defineProperty(iceGatherer, 'state',
        {value: 'new', writable: true}
    );

    this.transceivers[sdpMLineIndex].bufferedCandidateEvents = [];
    this.transceivers[sdpMLineIndex].bufferCandidates = function(event) {
      var end = !event.candidate || Object.keys(event.candidate).length === 0;
      // polyfill since RTCIceGatherer.state is not implemented in
      // Edge 10547 yet.
      iceGatherer.state = end ? 'completed' : 'gathering';
      if (pc.transceivers[sdpMLineIndex].bufferedCandidateEvents !== null) {
        pc.transceivers[sdpMLineIndex].bufferedCandidateEvents.push(event);
      }
    };
    iceGatherer.addEventListener('localcandidate',
      this.transceivers[sdpMLineIndex].bufferCandidates);
    return iceGatherer;
  };

  // start gathering from an RTCIceGatherer.
  RTCPeerConnection.prototype._gather = function(mid, sdpMLineIndex) {
    var pc = this;
    var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
    if (iceGatherer.onlocalcandidate) {
      return;
    }
    var bufferedCandidateEvents =
      this.transceivers[sdpMLineIndex].bufferedCandidateEvents;
    this.transceivers[sdpMLineIndex].bufferedCandidateEvents = null;
    iceGatherer.removeEventListener('localcandidate',
      this.transceivers[sdpMLineIndex].bufferCandidates);
    iceGatherer.onlocalcandidate = function(evt) {
      if (pc.usingBundle && sdpMLineIndex > 0) {
        // if we know that we use bundle we can drop candidates with
        // ѕdpMLineIndex > 0. If we don't do this then our state gets
        // confused since we dispose the extra ice gatherer.
        return;
      }
      var event = new Event('icecandidate');
      event.candidate = {sdpMid: mid, sdpMLineIndex: sdpMLineIndex};

      var cand = evt.candidate;
      // Edge emits an empty object for RTCIceCandidateComplete‥
      var end = !cand || Object.keys(cand).length === 0;
      if (end) {
        // polyfill since RTCIceGatherer.state is not implemented in
        // Edge 10547 yet.
        if (iceGatherer.state === 'new' || iceGatherer.state === 'gathering') {
          iceGatherer.state = 'completed';
        }
      } else {
        if (iceGatherer.state === 'new') {
          iceGatherer.state = 'gathering';
        }
        // RTCIceCandidate doesn't have a component, needs to be added
        cand.component = 1;
        // also the usernameFragment. TODO: update SDP to take both variants.
        cand.ufrag = iceGatherer.getLocalParameters().usernameFragment;

        var serializedCandidate = SDPUtils.writeCandidate(cand);
        event.candidate = Object.assign(event.candidate,
            SDPUtils.parseCandidate(serializedCandidate));

        event.candidate.candidate = serializedCandidate;
        event.candidate.toJSON = function() {
          return {
            candidate: event.candidate.candidate,
            sdpMid: event.candidate.sdpMid,
            sdpMLineIndex: event.candidate.sdpMLineIndex,
            usernameFragment: event.candidate.usernameFragment
          };
        };
      }

      // update local description.
      var sections = SDPUtils.getMediaSections(pc._localDescription.sdp);
      if (!end) {
        sections[event.candidate.sdpMLineIndex] +=
            'a=' + event.candidate.candidate + '\r\n';
      } else {
        sections[event.candidate.sdpMLineIndex] +=
            'a=end-of-candidates\r\n';
      }
      pc._localDescription.sdp =
          SDPUtils.getDescription(pc._localDescription.sdp) +
          sections.join('');
      var complete = pc.transceivers.every(function(transceiver) {
        return transceiver.iceGatherer &&
            transceiver.iceGatherer.state === 'completed';
      });

      if (pc.iceGatheringState !== 'gathering') {
        pc.iceGatheringState = 'gathering';
        pc._emitGatheringStateChange();
      }

      // Emit candidate. Also emit null candidate when all gatherers are
      // complete.
      if (!end) {
        pc._dispatchEvent('icecandidate', event);
      }
      if (complete) {
        pc._dispatchEvent('icecandidate', new Event('icecandidate'));
        pc.iceGatheringState = 'complete';
        pc._emitGatheringStateChange();
      }
    };

    // emit already gathered candidates.
    window.setTimeout(function() {
      bufferedCandidateEvents.forEach(function(e) {
        iceGatherer.onlocalcandidate(e);
      });
    }, 0);
  };

  // Create ICE transport and DTLS transport.
  RTCPeerConnection.prototype._createIceAndDtlsTransports = function() {
    var pc = this;
    var iceTransport = new window.RTCIceTransport(null);
    iceTransport.onicestatechange = function() {
      pc._updateIceConnectionState();
      pc._updateConnectionState();
    };

    var dtlsTransport = new window.RTCDtlsTransport(iceTransport);
    dtlsTransport.ondtlsstatechange = function() {
      pc._updateConnectionState();
    };
    dtlsTransport.onerror = function() {
      // onerror does not set state to failed by itself.
      Object.defineProperty(dtlsTransport, 'state',
          {value: 'failed', writable: true});
      pc._updateConnectionState();
    };

    return {
      iceTransport: iceTransport,
      dtlsTransport: dtlsTransport
    };
  };

  // Destroy ICE gatherer, ICE transport and DTLS transport.
  // Without triggering the callbacks.
  RTCPeerConnection.prototype._disposeIceAndDtlsTransports = function(
      sdpMLineIndex) {
    var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
    if (iceGatherer) {
      delete iceGatherer.onlocalcandidate;
      delete this.transceivers[sdpMLineIndex].iceGatherer;
    }
    var iceTransport = this.transceivers[sdpMLineIndex].iceTransport;
    if (iceTransport) {
      delete iceTransport.onicestatechange;
      delete this.transceivers[sdpMLineIndex].iceTransport;
    }
    var dtlsTransport = this.transceivers[sdpMLineIndex].dtlsTransport;
    if (dtlsTransport) {
      delete dtlsTransport.ondtlsstatechange;
      delete dtlsTransport.onerror;
      delete this.transceivers[sdpMLineIndex].dtlsTransport;
    }
  };

  // Start the RTP Sender and Receiver for a transceiver.
  RTCPeerConnection.prototype._transceive = function(transceiver,
      send, recv) {
    var params = getCommonCapabilities(transceiver.localCapabilities,
        transceiver.remoteCapabilities);
    if (send && transceiver.rtpSender) {
      params.encodings = transceiver.sendEncodingParameters;
      params.rtcp = {
        cname: SDPUtils.localCName,
        compound: transceiver.rtcpParameters.compound
      };
      if (transceiver.recvEncodingParameters.length) {
        params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
      }
      transceiver.rtpSender.send(params);
    }
    if (recv && transceiver.rtpReceiver && params.codecs.length > 0) {
      // remove RTX field in Edge 14942
      if (transceiver.kind === 'video'
          && transceiver.recvEncodingParameters
          && edgeVersion < 15019) {
        transceiver.recvEncodingParameters.forEach(function(p) {
          delete p.rtx;
        });
      }
      if (transceiver.recvEncodingParameters.length) {
        params.encodings = transceiver.recvEncodingParameters;
      } else {
        params.encodings = [{}];
      }
      params.rtcp = {
        compound: transceiver.rtcpParameters.compound
      };
      if (transceiver.rtcpParameters.cname) {
        params.rtcp.cname = transceiver.rtcpParameters.cname;
      }
      if (transceiver.sendEncodingParameters.length) {
        params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
      }
      transceiver.rtpReceiver.receive(params);
    }
  };

  RTCPeerConnection.prototype.setLocalDescription = function(description) {
    var pc = this;

    // Note: pranswer is not supported.
    if (['offer', 'answer'].indexOf(description.type) === -1) {
      return Promise.reject(makeError('TypeError',
          'Unsupported type "' + description.type + '"'));
    }

    if (!isActionAllowedInSignalingState('setLocalDescription',
        description.type, pc.signalingState) || pc._isClosed) {
      return Promise.reject(makeError('InvalidStateError',
          'Can not set local ' + description.type +
          ' in state ' + pc.signalingState));
    }

    var sections;
    var sessionpart;
    if (description.type === 'offer') {
      // VERY limited support for SDP munging. Limited to:
      // * changing the order of codecs
      sections = SDPUtils.splitSections(description.sdp);
      sessionpart = sections.shift();
      sections.forEach(function(mediaSection, sdpMLineIndex) {
        var caps = SDPUtils.parseRtpParameters(mediaSection);
        pc.transceivers[sdpMLineIndex].localCapabilities = caps;
      });

      pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
        pc._gather(transceiver.mid, sdpMLineIndex);
      });
    } else if (description.type === 'answer') {
      sections = SDPUtils.splitSections(pc._remoteDescription.sdp);
      sessionpart = sections.shift();
      var isIceLite = SDPUtils.matchPrefix(sessionpart,
          'a=ice-lite').length > 0;
      sections.forEach(function(mediaSection, sdpMLineIndex) {
        var transceiver = pc.transceivers[sdpMLineIndex];
        var iceGatherer = transceiver.iceGatherer;
        var iceTransport = transceiver.iceTransport;
        var dtlsTransport = transceiver.dtlsTransport;
        var localCapabilities = transceiver.localCapabilities;
        var remoteCapabilities = transceiver.remoteCapabilities;

        // treat bundle-only as not-rejected.
        var rejected = SDPUtils.isRejected(mediaSection) &&
            SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;

        if (!rejected && !transceiver.rejected) {
          var remoteIceParameters = SDPUtils.getIceParameters(
              mediaSection, sessionpart);
          var remoteDtlsParameters = SDPUtils.getDtlsParameters(
              mediaSection, sessionpart);
          if (isIceLite) {
            remoteDtlsParameters.role = 'server';
          }

          if (!pc.usingBundle || sdpMLineIndex === 0) {
            pc._gather(transceiver.mid, sdpMLineIndex);
            if (iceTransport.state === 'new') {
              iceTransport.start(iceGatherer, remoteIceParameters,
                  isIceLite ? 'controlling' : 'controlled');
            }
            if (dtlsTransport.state === 'new') {
              dtlsTransport.start(remoteDtlsParameters);
            }
          }

          // Calculate intersection of capabilities.
          var params = getCommonCapabilities(localCapabilities,
              remoteCapabilities);

          // Start the RTCRtpSender. The RTCRtpReceiver for this
          // transceiver has already been started in setRemoteDescription.
          pc._transceive(transceiver,
              params.codecs.length > 0,
              false);
        }
      });
    }

    pc._localDescription = {
      type: description.type,
      sdp: description.sdp
    };
    if (description.type === 'offer') {
      pc._updateSignalingState('have-local-offer');
    } else {
      pc._updateSignalingState('stable');
    }

    return Promise.resolve();
  };

  RTCPeerConnection.prototype.setRemoteDescription = function(description) {
    var pc = this;

    // Note: pranswer is not supported.
    if (['offer', 'answer'].indexOf(description.type) === -1) {
      return Promise.reject(makeError('TypeError',
          'Unsupported type "' + description.type + '"'));
    }

    if (!isActionAllowedInSignalingState('setRemoteDescription',
        description.type, pc.signalingState) || pc._isClosed) {
      return Promise.reject(makeError('InvalidStateError',
          'Can not set remote ' + description.type +
          ' in state ' + pc.signalingState));
    }

    var streams = {};
    pc.remoteStreams.forEach(function(stream) {
      streams[stream.id] = stream;
    });
    var receiverList = [];
    var sections = SDPUtils.splitSections(description.sdp);
    var sessionpart = sections.shift();
    var isIceLite = SDPUtils.matchPrefix(sessionpart,
        'a=ice-lite').length > 0;
    var usingBundle = SDPUtils.matchPrefix(sessionpart,
        'a=group:BUNDLE ').length > 0;
    pc.usingBundle = usingBundle;
    var iceOptions = SDPUtils.matchPrefix(sessionpart,
        'a=ice-options:')[0];
    if (iceOptions) {
      pc.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
          .indexOf('trickle') >= 0;
    } else {
      pc.canTrickleIceCandidates = false;
    }

    sections.forEach(function(mediaSection, sdpMLineIndex) {
      var lines = SDPUtils.splitLines(mediaSection);
      var kind = SDPUtils.getKind(mediaSection);
      // treat bundle-only as not-rejected.
      var rejected = SDPUtils.isRejected(mediaSection) &&
          SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;
      var protocol = lines[0].substr(2).split(' ')[2];

      var direction = SDPUtils.getDirection(mediaSection, sessionpart);
      var remoteMsid = SDPUtils.parseMsid(mediaSection);

      var mid = SDPUtils.getMid(mediaSection) || SDPUtils.generateIdentifier();

      // Reject datachannels which are not implemented yet.
      if (rejected || (kind === 'application' && (protocol === 'DTLS/SCTP' ||
          protocol === 'UDP/DTLS/SCTP'))) {
        // TODO: this is dangerous in the case where a non-rejected m-line
        //     becomes rejected.
        pc.transceivers[sdpMLineIndex] = {
          mid: mid,
          kind: kind,
          protocol: protocol,
          rejected: true
        };
        return;
      }

      if (!rejected && pc.transceivers[sdpMLineIndex] &&
          pc.transceivers[sdpMLineIndex].rejected) {
        // recycle a rejected transceiver.
        pc.transceivers[sdpMLineIndex] = pc._createTransceiver(kind, true);
      }

      var transceiver;
      var iceGatherer;
      var iceTransport;
      var dtlsTransport;
      var rtpReceiver;
      var sendEncodingParameters;
      var recvEncodingParameters;
      var localCapabilities;

      var track;
      // FIXME: ensure the mediaSection has rtcp-mux set.
      var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
      var remoteIceParameters;
      var remoteDtlsParameters;
      if (!rejected) {
        remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
            sessionpart);
        remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
            sessionpart);
        remoteDtlsParameters.role = 'client';
      }
      recvEncodingParameters =
          SDPUtils.parseRtpEncodingParameters(mediaSection);

      var rtcpParameters = SDPUtils.parseRtcpParameters(mediaSection);

      var isComplete = SDPUtils.matchPrefix(mediaSection,
          'a=end-of-candidates', sessionpart).length > 0;
      var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
          .map(function(cand) {
            return SDPUtils.parseCandidate(cand);
          })
          .filter(function(cand) {
            return cand.component === 1;
          });

      // Check if we can use BUNDLE and dispose transports.
      if ((description.type === 'offer' || description.type === 'answer') &&
          !rejected && usingBundle && sdpMLineIndex > 0 &&
          pc.transceivers[sdpMLineIndex]) {
        pc._disposeIceAndDtlsTransports(sdpMLineIndex);
        pc.transceivers[sdpMLineIndex].iceGatherer =
            pc.transceivers[0].iceGatherer;
        pc.transceivers[sdpMLineIndex].iceTransport =
            pc.transceivers[0].iceTransport;
        pc.transceivers[sdpMLineIndex].dtlsTransport =
            pc.transceivers[0].dtlsTransport;
        if (pc.transceivers[sdpMLineIndex].rtpSender) {
          pc.transceivers[sdpMLineIndex].rtpSender.setTransport(
              pc.transceivers[0].dtlsTransport);
        }
        if (pc.transceivers[sdpMLineIndex].rtpReceiver) {
          pc.transceivers[sdpMLineIndex].rtpReceiver.setTransport(
              pc.transceivers[0].dtlsTransport);
        }
      }
      if (description.type === 'offer' && !rejected) {
        transceiver = pc.transceivers[sdpMLineIndex] ||
            pc._createTransceiver(kind);
        transceiver.mid = mid;

        if (!transceiver.iceGatherer) {
          transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
              usingBundle);
        }

        if (cands.length && transceiver.iceTransport.state === 'new') {
          if (isComplete && (!usingBundle || sdpMLineIndex === 0)) {
            transceiver.iceTransport.setRemoteCandidates(cands);
          } else {
            cands.forEach(function(candidate) {
              maybeAddCandidate(transceiver.iceTransport, candidate);
            });
          }
        }

        localCapabilities = window.RTCRtpReceiver.getCapabilities(kind);

        // filter RTX until additional stuff needed for RTX is implemented
        // in adapter.js
        if (edgeVersion < 15019) {
          localCapabilities.codecs = localCapabilities.codecs.filter(
              function(codec) {
                return codec.name !== 'rtx';
              });
        }

        sendEncodingParameters = transceiver.sendEncodingParameters || [{
          ssrc: (2 * sdpMLineIndex + 2) * 1001
        }];

        // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
        var isNewTrack = false;
        if (direction === 'sendrecv' || direction === 'sendonly') {
          isNewTrack = !transceiver.rtpReceiver;
          rtpReceiver = transceiver.rtpReceiver ||
              new window.RTCRtpReceiver(transceiver.dtlsTransport, kind);

          if (isNewTrack) {
            var stream;
            track = rtpReceiver.track;
            // FIXME: does not work with Plan B.
            if (remoteMsid && remoteMsid.stream === '-') {
              // no-op. a stream id of '-' means: no associated stream.
            } else if (remoteMsid) {
              if (!streams[remoteMsid.stream]) {
                streams[remoteMsid.stream] = new window.MediaStream();
                Object.defineProperty(streams[remoteMsid.stream], 'id', {
                  get: function() {
                    return remoteMsid.stream;
                  }
                });
              }
              Object.defineProperty(track, 'id', {
                get: function() {
                  return remoteMsid.track;
                }
              });
              stream = streams[remoteMsid.stream];
            } else {
              if (!streams.default) {
                streams.default = new window.MediaStream();
              }
              stream = streams.default;
            }
            if (stream) {
              addTrackToStreamAndFireEvent(track, stream);
              transceiver.associatedRemoteMediaStreams.push(stream);
            }
            receiverList.push([track, rtpReceiver, stream]);
          }
        } else if (transceiver.rtpReceiver && transceiver.rtpReceiver.track) {
          transceiver.associatedRemoteMediaStreams.forEach(function(s) {
            var nativeTrack = s.getTracks().find(function(t) {
              return t.id === transceiver.rtpReceiver.track.id;
            });
            if (nativeTrack) {
              removeTrackFromStreamAndFireEvent(nativeTrack, s);
            }
          });
          transceiver.associatedRemoteMediaStreams = [];
        }

        transceiver.localCapabilities = localCapabilities;
        transceiver.remoteCapabilities = remoteCapabilities;
        transceiver.rtpReceiver = rtpReceiver;
        transceiver.rtcpParameters = rtcpParameters;
        transceiver.sendEncodingParameters = sendEncodingParameters;
        transceiver.recvEncodingParameters = recvEncodingParameters;

        // Start the RTCRtpReceiver now. The RTPSender is started in
        // setLocalDescription.
        pc._transceive(pc.transceivers[sdpMLineIndex],
            false,
            isNewTrack);
      } else if (description.type === 'answer' && !rejected) {
        transceiver = pc.transceivers[sdpMLineIndex];
        iceGatherer = transceiver.iceGatherer;
        iceTransport = transceiver.iceTransport;
        dtlsTransport = transceiver.dtlsTransport;
        rtpReceiver = transceiver.rtpReceiver;
        sendEncodingParameters = transceiver.sendEncodingParameters;
        localCapabilities = transceiver.localCapabilities;

        pc.transceivers[sdpMLineIndex].recvEncodingParameters =
            recvEncodingParameters;
        pc.transceivers[sdpMLineIndex].remoteCapabilities =
            remoteCapabilities;
        pc.transceivers[sdpMLineIndex].rtcpParameters = rtcpParameters;

        if (cands.length && iceTransport.state === 'new') {
          if ((isIceLite || isComplete) &&
              (!usingBundle || sdpMLineIndex === 0)) {
            iceTransport.setRemoteCandidates(cands);
          } else {
            cands.forEach(function(candidate) {
              maybeAddCandidate(transceiver.iceTransport, candidate);
            });
          }
        }

        if (!usingBundle || sdpMLineIndex === 0) {
          if (iceTransport.state === 'new') {
            iceTransport.start(iceGatherer, remoteIceParameters,
                'controlling');
          }
          if (dtlsTransport.state === 'new') {
            dtlsTransport.start(remoteDtlsParameters);
          }
        }

        // If the offer contained RTX but the answer did not,
        // remove RTX from sendEncodingParameters.
        var commonCapabilities = getCommonCapabilities(
          transceiver.localCapabilities,
          transceiver.remoteCapabilities);

        var hasRtx = commonCapabilities.codecs.filter(function(c) {
          return c.name.toLowerCase() === 'rtx';
        }).length;
        if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
          delete transceiver.sendEncodingParameters[0].rtx;
        }

        pc._transceive(transceiver,
            direction === 'sendrecv' || direction === 'recvonly',
            direction === 'sendrecv' || direction === 'sendonly');

        // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
        if (rtpReceiver &&
            (direction === 'sendrecv' || direction === 'sendonly')) {
          track = rtpReceiver.track;
          if (remoteMsid) {
            if (!streams[remoteMsid.stream]) {
              streams[remoteMsid.stream] = new window.MediaStream();
            }
            addTrackToStreamAndFireEvent(track, streams[remoteMsid.stream]);
            receiverList.push([track, rtpReceiver, streams[remoteMsid.stream]]);
          } else {
            if (!streams.default) {
              streams.default = new window.MediaStream();
            }
            addTrackToStreamAndFireEvent(track, streams.default);
            receiverList.push([track, rtpReceiver, streams.default]);
          }
        } else {
          // FIXME: actually the receiver should be created later.
          delete transceiver.rtpReceiver;
        }
      }
    });

    if (pc._dtlsRole === undefined) {
      pc._dtlsRole = description.type === 'offer' ? 'active' : 'passive';
    }

    pc._remoteDescription = {
      type: description.type,
      sdp: description.sdp
    };
    if (description.type === 'offer') {
      pc._updateSignalingState('have-remote-offer');
    } else {
      pc._updateSignalingState('stable');
    }
    Object.keys(streams).forEach(function(sid) {
      var stream = streams[sid];
      if (stream.getTracks().length) {
        if (pc.remoteStreams.indexOf(stream) === -1) {
          pc.remoteStreams.push(stream);
          var event = new Event('addstream');
          event.stream = stream;
          window.setTimeout(function() {
            pc._dispatchEvent('addstream', event);
          });
        }

        receiverList.forEach(function(item) {
          var track = item[0];
          var receiver = item[1];
          if (stream.id !== item[2].id) {
            return;
          }
          fireAddTrack(pc, track, receiver, [stream]);
        });
      }
    });
    receiverList.forEach(function(item) {
      if (item[2]) {
        return;
      }
      fireAddTrack(pc, item[0], item[1], []);
    });

    // check whether addIceCandidate({}) was called within four seconds after
    // setRemoteDescription.
    window.setTimeout(function() {
      if (!(pc && pc.transceivers)) {
        return;
      }
      pc.transceivers.forEach(function(transceiver) {
        if (transceiver.iceTransport &&
            transceiver.iceTransport.state === 'new' &&
            transceiver.iceTransport.getRemoteCandidates().length > 0) {
          console.warn('Timeout for addRemoteCandidate. Consider sending ' +
              'an end-of-candidates notification');
          transceiver.iceTransport.addRemoteCandidate({});
        }
      });
    }, 4000);

    return Promise.resolve();
  };

  RTCPeerConnection.prototype.close = function() {
    this.transceivers.forEach(function(transceiver) {
      /* not yet
      if (transceiver.iceGatherer) {
        transceiver.iceGatherer.close();
      }
      */
      if (transceiver.iceTransport) {
        transceiver.iceTransport.stop();
      }
      if (transceiver.dtlsTransport) {
        transceiver.dtlsTransport.stop();
      }
      if (transceiver.rtpSender) {
        transceiver.rtpSender.stop();
      }
      if (transceiver.rtpReceiver) {
        transceiver.rtpReceiver.stop();
      }
    });
    // FIXME: clean up tracks, local streams, remote streams, etc
    this._isClosed = true;
    this._updateSignalingState('closed');
  };

  // Update the signaling state.
  RTCPeerConnection.prototype._updateSignalingState = function(newState) {
    this.signalingState = newState;
    var event = new Event('signalingstatechange');
    this._dispatchEvent('signalingstatechange', event);
  };

  // Determine whether to fire the negotiationneeded event.
  RTCPeerConnection.prototype._maybeFireNegotiationNeeded = function() {
    var pc = this;
    if (this.signalingState !== 'stable' || this.needNegotiation === true) {
      return;
    }
    this.needNegotiation = true;
    window.setTimeout(function() {
      if (pc.needNegotiation) {
        pc.needNegotiation = false;
        var event = new Event('negotiationneeded');
        pc._dispatchEvent('negotiationneeded', event);
      }
    }, 0);
  };

  // Update the ice connection state.
  RTCPeerConnection.prototype._updateIceConnectionState = function() {
    var newState;
    var states = {
      'new': 0,
      closed: 0,
      checking: 0,
      connected: 0,
      completed: 0,
      disconnected: 0,
      failed: 0
    };
    this.transceivers.forEach(function(transceiver) {
      if (transceiver.iceTransport && !transceiver.rejected) {
        states[transceiver.iceTransport.state]++;
      }
    });

    newState = 'new';
    if (states.failed > 0) {
      newState = 'failed';
    } else if (states.checking > 0) {
      newState = 'checking';
    } else if (states.disconnected > 0) {
      newState = 'disconnected';
    } else if (states.new > 0) {
      newState = 'new';
    } else if (states.connected > 0) {
      newState = 'connected';
    } else if (states.completed > 0) {
      newState = 'completed';
    }

    if (newState !== this.iceConnectionState) {
      this.iceConnectionState = newState;
      var event = new Event('iceconnectionstatechange');
      this._dispatchEvent('iceconnectionstatechange', event);
    }
  };

  // Update the connection state.
  RTCPeerConnection.prototype._updateConnectionState = function() {
    var newState;
    var states = {
      'new': 0,
      closed: 0,
      connecting: 0,
      connected: 0,
      completed: 0,
      disconnected: 0,
      failed: 0
    };
    this.transceivers.forEach(function(transceiver) {
      if (transceiver.iceTransport && transceiver.dtlsTransport &&
          !transceiver.rejected) {
        states[transceiver.iceTransport.state]++;
        states[transceiver.dtlsTransport.state]++;
      }
    });
    // ICETransport.completed and connected are the same for this purpose.
    states.connected += states.completed;

    newState = 'new';
    if (states.failed > 0) {
      newState = 'failed';
    } else if (states.connecting > 0) {
      newState = 'connecting';
    } else if (states.disconnected > 0) {
      newState = 'disconnected';
    } else if (states.new > 0) {
      newState = 'new';
    } else if (states.connected > 0) {
      newState = 'connected';
    }

    if (newState !== this.connectionState) {
      this.connectionState = newState;
      var event = new Event('connectionstatechange');
      this._dispatchEvent('connectionstatechange', event);
    }
  };

  RTCPeerConnection.prototype.createOffer = function() {
    var pc = this;

    if (pc._isClosed) {
      return Promise.reject(makeError('InvalidStateError',
          'Can not call createOffer after close'));
    }

    var numAudioTracks = pc.transceivers.filter(function(t) {
      return t.kind === 'audio';
    }).length;
    var numVideoTracks = pc.transceivers.filter(function(t) {
      return t.kind === 'video';
    }).length;

    // Determine number of audio and video tracks we need to send/recv.
    var offerOptions = arguments[0];
    if (offerOptions) {
      // Reject Chrome legacy constraints.
      if (offerOptions.mandatory || offerOptions.optional) {
        throw new TypeError(
            'Legacy mandatory/optional constraints not supported.');
      }
      if (offerOptions.offerToReceiveAudio !== undefined) {
        if (offerOptions.offerToReceiveAudio === true) {
          numAudioTracks = 1;
        } else if (offerOptions.offerToReceiveAudio === false) {
          numAudioTracks = 0;
        } else {
          numAudioTracks = offerOptions.offerToReceiveAudio;
        }
      }
      if (offerOptions.offerToReceiveVideo !== undefined) {
        if (offerOptions.offerToReceiveVideo === true) {
          numVideoTracks = 1;
        } else if (offerOptions.offerToReceiveVideo === false) {
          numVideoTracks = 0;
        } else {
          numVideoTracks = offerOptions.offerToReceiveVideo;
        }
      }
    }

    pc.transceivers.forEach(function(transceiver) {
      if (transceiver.kind === 'audio') {
        numAudioTracks--;
        if (numAudioTracks < 0) {
          transceiver.wantReceive = false;
        }
      } else if (transceiver.kind === 'video') {
        numVideoTracks--;
        if (numVideoTracks < 0) {
          transceiver.wantReceive = false;
        }
      }
    });

    // Create M-lines for recvonly streams.
    while (numAudioTracks > 0 || numVideoTracks > 0) {
      if (numAudioTracks > 0) {
        pc._createTransceiver('audio');
        numAudioTracks--;
      }
      if (numVideoTracks > 0) {
        pc._createTransceiver('video');
        numVideoTracks--;
      }
    }

    var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
        pc._sdpSessionVersion++);
    pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
      // For each track, create an ice gatherer, ice transport,
      // dtls transport, potentially rtpsender and rtpreceiver.
      var track = transceiver.track;
      var kind = transceiver.kind;
      var mid = transceiver.mid || SDPUtils.generateIdentifier();
      transceiver.mid = mid;

      if (!transceiver.iceGatherer) {
        transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
            pc.usingBundle);
      }

      var localCapabilities = window.RTCRtpSender.getCapabilities(kind);
      // filter RTX until additional stuff needed for RTX is implemented
      // in adapter.js
      if (edgeVersion < 15019) {
        localCapabilities.codecs = localCapabilities.codecs.filter(
            function(codec) {
              return codec.name !== 'rtx';
            });
      }
      localCapabilities.codecs.forEach(function(codec) {
        // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
        // by adding level-asymmetry-allowed=1
        if (codec.name === 'H264' &&
            codec.parameters['level-asymmetry-allowed'] === undefined) {
          codec.parameters['level-asymmetry-allowed'] = '1';
        }

        // for subsequent offers, we might have to re-use the payload
        // type of the last offer.
        if (transceiver.remoteCapabilities &&
            transceiver.remoteCapabilities.codecs) {
          transceiver.remoteCapabilities.codecs.forEach(function(remoteCodec) {
            if (codec.name.toLowerCase() === remoteCodec.name.toLowerCase() &&
                codec.clockRate === remoteCodec.clockRate) {
              codec.preferredPayloadType = remoteCodec.payloadType;
            }
          });
        }
      });
      localCapabilities.headerExtensions.forEach(function(hdrExt) {
        var remoteExtensions = transceiver.remoteCapabilities &&
            transceiver.remoteCapabilities.headerExtensions || [];
        remoteExtensions.forEach(function(rHdrExt) {
          if (hdrExt.uri === rHdrExt.uri) {
            hdrExt.id = rHdrExt.id;
          }
        });
      });

      // generate an ssrc now, to be used later in rtpSender.send
      var sendEncodingParameters = transceiver.sendEncodingParameters || [{
        ssrc: (2 * sdpMLineIndex + 1) * 1001
      }];
      if (track) {
        // add RTX
        if (edgeVersion >= 15019 && kind === 'video' &&
            !sendEncodingParameters[0].rtx) {
          sendEncodingParameters[0].rtx = {
            ssrc: sendEncodingParameters[0].ssrc + 1
          };
        }
      }

      if (transceiver.wantReceive) {
        transceiver.rtpReceiver = new window.RTCRtpReceiver(
            transceiver.dtlsTransport, kind);
      }

      transceiver.localCapabilities = localCapabilities;
      transceiver.sendEncodingParameters = sendEncodingParameters;
    });

    // always offer BUNDLE and dispose on return if not supported.
    if (pc._config.bundlePolicy !== 'max-compat') {
      sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
        return t.mid;
      }).join(' ') + '\r\n';
    }
    sdp += 'a=ice-options:trickle\r\n';

    pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
      sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
          'offer', transceiver.stream, pc._dtlsRole);
      sdp += 'a=rtcp-rsize\r\n';

      if (transceiver.iceGatherer && pc.iceGatheringState !== 'new' &&
          (sdpMLineIndex === 0 || !pc.usingBundle)) {
        transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
          cand.component = 1;
          sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n';
        });

        if (transceiver.iceGatherer.state === 'completed') {
          sdp += 'a=end-of-candidates\r\n';
        }
      }
    });

    var desc = new window.RTCSessionDescription({
      type: 'offer',
      sdp: sdp
    });
    return Promise.resolve(desc);
  };

  RTCPeerConnection.prototype.createAnswer = function() {
    var pc = this;

    if (pc._isClosed) {
      return Promise.reject(makeError('InvalidStateError',
          'Can not call createAnswer after close'));
    }

    if (!(pc.signalingState === 'have-remote-offer' ||
        pc.signalingState === 'have-local-pranswer')) {
      return Promise.reject(makeError('InvalidStateError',
          'Can not call createAnswer in signalingState ' + pc.signalingState));
    }

    var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
        pc._sdpSessionVersion++);
    if (pc.usingBundle) {
      sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
        return t.mid;
      }).join(' ') + '\r\n';
    }
    sdp += 'a=ice-options:trickle\r\n';

    var mediaSectionsInOffer = SDPUtils.getMediaSections(
        pc._remoteDescription.sdp).length;
    pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
      if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
        return;
      }
      if (transceiver.rejected) {
        if (transceiver.kind === 'application') {
          if (transceiver.protocol === 'DTLS/SCTP') { // legacy fmt
            sdp += 'm=application 0 DTLS/SCTP 5000\r\n';
          } else {
            sdp += 'm=application 0 ' + transceiver.protocol +
                ' webrtc-datachannel\r\n';
          }
        } else if (transceiver.kind === 'audio') {
          sdp += 'm=audio 0 UDP/TLS/RTP/SAVPF 0\r\n' +
              'a=rtpmap:0 PCMU/8000\r\n';
        } else if (transceiver.kind === 'video') {
          sdp += 'm=video 0 UDP/TLS/RTP/SAVPF 120\r\n' +
              'a=rtpmap:120 VP8/90000\r\n';
        }
        sdp += 'c=IN IP4 0.0.0.0\r\n' +
            'a=inactive\r\n' +
            'a=mid:' + transceiver.mid + '\r\n';
        return;
      }

      // FIXME: look at direction.
      if (transceiver.stream) {
        var localTrack;
        if (transceiver.kind === 'audio') {
          localTrack = transceiver.stream.getAudioTracks()[0];
        } else if (transceiver.kind === 'video') {
          localTrack = transceiver.stream.getVideoTracks()[0];
        }
        if (localTrack) {
          // add RTX
          if (edgeVersion >= 15019 && transceiver.kind === 'video' &&
              !transceiver.sendEncodingParameters[0].rtx) {
            transceiver.sendEncodingParameters[0].rtx = {
              ssrc: transceiver.sendEncodingParameters[0].ssrc + 1
            };
          }
        }
      }

      // Calculate intersection of capabilities.
      var commonCapabilities = getCommonCapabilities(
          transceiver.localCapabilities,
          transceiver.remoteCapabilities);

      var hasRtx = commonCapabilities.codecs.filter(function(c) {
        return c.name.toLowerCase() === 'rtx';
      }).length;
      if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
        delete transceiver.sendEncodingParameters[0].rtx;
      }

      sdp += writeMediaSection(transceiver, commonCapabilities,
          'answer', transceiver.stream, pc._dtlsRole);
      if (transceiver.rtcpParameters &&
          transceiver.rtcpParameters.reducedSize) {
        sdp += 'a=rtcp-rsize\r\n';
      }
    });

    var desc = new window.RTCSessionDescription({
      type: 'answer',
      sdp: sdp
    });
    return Promise.resolve(desc);
  };

  RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
    var pc = this;
    var sections;
    if (candidate && !(candidate.sdpMLineIndex !== undefined ||
        candidate.sdpMid)) {
      return Promise.reject(new TypeError('sdpMLineIndex or sdpMid required'));
    }

    // TODO: needs to go into ops queue.
    return new Promise(function(resolve, reject) {
      if (!pc._remoteDescription) {
        return reject(makeError('InvalidStateError',
            'Can not add ICE candidate without a remote description'));
      } else if (!candidate || candidate.candidate === '') {
        for (var j = 0; j < pc.transceivers.length; j++) {
          if (pc.transceivers[j].rejected) {
            continue;
          }
          pc.transceivers[j].iceTransport.addRemoteCandidate({});
          sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp);
          sections[j] += 'a=end-of-candidates\r\n';
          pc._remoteDescription.sdp =
              SDPUtils.getDescription(pc._remoteDescription.sdp) +
              sections.join('');
          if (pc.usingBundle) {
            break;
          }
        }
      } else {
        var sdpMLineIndex = candidate.sdpMLineIndex;
        if (candidate.sdpMid) {
          for (var i = 0; i < pc.transceivers.length; i++) {
            if (pc.transceivers[i].mid === candidate.sdpMid) {
              sdpMLineIndex = i;
              break;
            }
          }
        }
        var transceiver = pc.transceivers[sdpMLineIndex];
        if (transceiver) {
          if (transceiver.rejected) {
            return resolve();
          }
          var cand = Object.keys(candidate.candidate).length > 0 ?
              SDPUtils.parseCandidate(candidate.candidate) : {};
          // Ignore Chrome's invalid candidates since Edge does not like them.
          if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
            return resolve();
          }
          // Ignore RTCP candidates, we assume RTCP-MUX.
          if (cand.component && cand.component !== 1) {
            return resolve();
          }
          // when using bundle, avoid adding candidates to the wrong
          // ice transport. And avoid adding candidates added in the SDP.
          if (sdpMLineIndex === 0 || (sdpMLineIndex > 0 &&
              transceiver.iceTransport !== pc.transceivers[0].iceTransport)) {
            if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
              return reject(makeError('OperationError',
                  'Can not add ICE candidate'));
            }
          }

          // update the remoteDescription.
          var candidateString = candidate.candidate.trim();
          if (candidateString.indexOf('a=') === 0) {
            candidateString = candidateString.substr(2);
          }
          sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp);
          sections[sdpMLineIndex] += 'a=' +
              (cand.type ? candidateString : 'end-of-candidates')
              + '\r\n';
          pc._remoteDescription.sdp =
              SDPUtils.getDescription(pc._remoteDescription.sdp) +
              sections.join('');
        } else {
          return reject(makeError('OperationError',
              'Can not add ICE candidate'));
        }
      }
      resolve();
    });
  };

  RTCPeerConnection.prototype.getStats = function(selector) {
    if (selector && selector instanceof window.MediaStreamTrack) {
      var senderOrReceiver = null;
      this.transceivers.forEach(function(transceiver) {
        if (transceiver.rtpSender &&
            transceiver.rtpSender.track === selector) {
          senderOrReceiver = transceiver.rtpSender;
        } else if (transceiver.rtpReceiver &&
            transceiver.rtpReceiver.track === selector) {
          senderOrReceiver = transceiver.rtpReceiver;
        }
      });
      if (!senderOrReceiver) {
        throw makeError('InvalidAccessError', 'Invalid selector.');
      }
      return senderOrReceiver.getStats();
    }

    var promises = [];
    this.transceivers.forEach(function(transceiver) {
      ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
          'dtlsTransport'].forEach(function(method) {
            if (transceiver[method]) {
              promises.push(transceiver[method].getStats());
            }
          });
    });
    return Promise.all(promises).then(function(allStats) {
      var results = new Map();
      allStats.forEach(function(stats) {
        stats.forEach(function(stat) {
          results.set(stat.id, stat);
        });
      });
      return results;
    });
  };

  // fix low-level stat names and return Map instead of object.
  var ortcObjects = ['RTCRtpSender', 'RTCRtpReceiver', 'RTCIceGatherer',
    'RTCIceTransport', 'RTCDtlsTransport'];
  ortcObjects.forEach(function(ortcObjectName) {
    var obj = window[ortcObjectName];
    if (obj && obj.prototype && obj.prototype.getStats) {
      var nativeGetstats = obj.prototype.getStats;
      obj.prototype.getStats = function() {
        return nativeGetstats.apply(this)
        .then(function(nativeStats) {
          var mapStats = new Map();
          Object.keys(nativeStats).forEach(function(id) {
            nativeStats[id].type = fixStatsType(nativeStats[id]);
            mapStats.set(id, nativeStats[id]);
          });
          return mapStats;
        });
      };
    }
  });

  // legacy callback shims. Should be moved to adapter.js some days.
  var methods = ['createOffer', 'createAnswer'];
  methods.forEach(function(method) {
    var nativeMethod = RTCPeerConnection.prototype[method];
    RTCPeerConnection.prototype[method] = function() {
      var args = arguments;
      if (typeof args[0] === 'function' ||
          typeof args[1] === 'function') { // legacy
        return nativeMethod.apply(this, [arguments[2]])
        .then(function(description) {
          if (typeof args[0] === 'function') {
            args[0].apply(null, [description]);
          }
        }, function(error) {
          if (typeof args[1] === 'function') {
            args[1].apply(null, [error]);
          }
        });
      }
      return nativeMethod.apply(this, arguments);
    };
  });

  methods = ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'];
  methods.forEach(function(method) {
    var nativeMethod = RTCPeerConnection.prototype[method];
    RTCPeerConnection.prototype[method] = function() {
      var args = arguments;
      if (typeof args[1] === 'function' ||
          typeof args[2] === 'function') { // legacy
        return nativeMethod.apply(this, arguments)
        .then(function() {
          if (typeof args[1] === 'function') {
            args[1].apply(null);
          }
        }, function(error) {
          if (typeof args[2] === 'function') {
            args[2].apply(null, [error]);
          }
        });
      }
      return nativeMethod.apply(this, arguments);
    };
  });

  // getStats is special. It doesn't have a spec legacy method yet we support
  // getStats(something, cb) without error callbacks.
  ['getStats'].forEach(function(method) {
    var nativeMethod = RTCPeerConnection.prototype[method];
    RTCPeerConnection.prototype[method] = function() {
      var args = arguments;
      if (typeof args[1] === 'function') {
        return nativeMethod.apply(this, arguments)
        .then(function() {
          if (typeof args[1] === 'function') {
            args[1].apply(null);
          }
        });
      }
      return nativeMethod.apply(this, arguments);
    };
  });

  return RTCPeerConnection;
};

},{"sdp":17}],17:[function(require,module,exports){
 /* eslint-env node */
'use strict';

// SDP helpers.
var SDPUtils = {};

// Generate an alphanumeric identifier for cname or mids.
// TODO: use UUIDs instead? https://gist.github.com/jed/982883
SDPUtils.generateIdentifier = function() {
  return Math.random().toString(36).substr(2, 10);
};

// The RTCP CNAME used by all peerconnections from the same JS.
SDPUtils.localCName = SDPUtils.generateIdentifier();

// Splits SDP into lines, dealing with both CRLF and LF.
SDPUtils.splitLines = function(blob) {
  return blob.trim().split('\n').map(function(line) {
    return line.trim();
  });
};
// Splits SDP into sessionpart and mediasections. Ensures CRLF.
SDPUtils.splitSections = function(blob) {
  var parts = blob.split('\nm=');
  return parts.map(function(part, index) {
    return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
  });
};

// returns the session description.
SDPUtils.getDescription = function(blob) {
  var sections = SDPUtils.splitSections(blob);
  return sections && sections[0];
};

// returns the individual media sections.
SDPUtils.getMediaSections = function(blob) {
  var sections = SDPUtils.splitSections(blob);
  sections.shift();
  return sections;
};

// Returns lines that start with a certain prefix.
SDPUtils.matchPrefix = function(blob, prefix) {
  return SDPUtils.splitLines(blob).filter(function(line) {
    return line.indexOf(prefix) === 0;
  });
};

// Parses an ICE candidate line. Sample input:
// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
// rport 55996"
SDPUtils.parseCandidate = function(line) {
  var parts;
  // Parse both variants.
  if (line.indexOf('a=candidate:') === 0) {
    parts = line.substring(12).split(' ');
  } else {
    parts = line.substring(10).split(' ');
  }

  var candidate = {
    foundation: parts[0],
    component: parseInt(parts[1], 10),
    protocol: parts[2].toLowerCase(),
    priority: parseInt(parts[3], 10),
    ip: parts[4],
    address: parts[4], // address is an alias for ip.
    port: parseInt(parts[5], 10),
    // skip parts[6] == 'typ'
    type: parts[7]
  };

  for (var i = 8; i < parts.length; i += 2) {
    switch (parts[i]) {
      case 'raddr':
        candidate.relatedAddress = parts[i + 1];
        break;
      case 'rport':
        candidate.relatedPort = parseInt(parts[i + 1], 10);
        break;
      case 'tcptype':
        candidate.tcpType = parts[i + 1];
        break;
      case 'ufrag':
        candidate.ufrag = parts[i + 1]; // for backward compability.
        candidate.usernameFragment = parts[i + 1];
        break;
      default: // extension handling, in particular ufrag
        candidate[parts[i]] = parts[i + 1];
        break;
    }
  }
  return candidate;
};

// Translates a candidate object into SDP candidate attribute.
SDPUtils.writeCandidate = function(candidate) {
  var sdp = [];
  sdp.push(candidate.foundation);
  sdp.push(candidate.component);
  sdp.push(candidate.protocol.toUpperCase());
  sdp.push(candidate.priority);
  sdp.push(candidate.address || candidate.ip);
  sdp.push(candidate.port);

  var type = candidate.type;
  sdp.push('typ');
  sdp.push(type);
  if (type !== 'host' && candidate.relatedAddress &&
      candidate.relatedPort) {
    sdp.push('raddr');
    sdp.push(candidate.relatedAddress);
    sdp.push('rport');
    sdp.push(candidate.relatedPort);
  }
  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
    sdp.push('tcptype');
    sdp.push(candidate.tcpType);
  }
  if (candidate.usernameFragment || candidate.ufrag) {
    sdp.push('ufrag');
    sdp.push(candidate.usernameFragment || candidate.ufrag);
  }
  return 'candidate:' + sdp.join(' ');
};

// Parses an ice-options line, returns an array of option tags.
// a=ice-options:foo bar
SDPUtils.parseIceOptions = function(line) {
  return line.substr(14).split(' ');
};

// Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
// a=rtpmap:111 opus/48000/2
SDPUtils.parseRtpMap = function(line) {
  var parts = line.substr(9).split(' ');
  var parsed = {
    payloadType: parseInt(parts.shift(), 10) // was: id
  };

  parts = parts[0].split('/');

  parsed.name = parts[0];
  parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
  parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
  // legacy alias, got renamed back to channels in ORTC.
  parsed.numChannels = parsed.channels;
  return parsed;
};

// Generate an a=rtpmap line from RTCRtpCodecCapability or
// RTCRtpCodecParameters.
SDPUtils.writeRtpMap = function(codec) {
  var pt = codec.payloadType;
  if (codec.preferredPayloadType !== undefined) {
    pt = codec.preferredPayloadType;
  }
  var channels = codec.channels || codec.numChannels || 1;
  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
      (channels !== 1 ? '/' + channels : '') + '\r\n';
};

// Parses an a=extmap line (headerextension from RFC 5285). Sample input:
// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
SDPUtils.parseExtmap = function(line) {
  var parts = line.substr(9).split(' ');
  return {
    id: parseInt(parts[0], 10),
    direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
    uri: parts[1]
  };
};

// Generates a=extmap line from RTCRtpHeaderExtensionParameters or
// RTCRtpHeaderExtension.
SDPUtils.writeExtmap = function(headerExtension) {
  return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
      (headerExtension.direction && headerExtension.direction !== 'sendrecv'
          ? '/' + headerExtension.direction
          : '') +
      ' ' + headerExtension.uri + '\r\n';
};

// Parses an ftmp line, returns dictionary. Sample input:
// a=fmtp:96 vbr=on;cng=on
// Also deals with vbr=on; cng=on
SDPUtils.parseFmtp = function(line) {
  var parsed = {};
  var kv;
  var parts = line.substr(line.indexOf(' ') + 1).split(';');
  for (var j = 0; j < parts.length; j++) {
    kv = parts[j].trim().split('=');
    parsed[kv[0].trim()] = kv[1];
  }
  return parsed;
};

// Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
SDPUtils.writeFmtp = function(codec) {
  var line = '';
  var pt = codec.payloadType;
  if (codec.preferredPayloadType !== undefined) {
    pt = codec.preferredPayloadType;
  }
  if (codec.parameters && Object.keys(codec.parameters).length) {
    var params = [];
    Object.keys(codec.parameters).forEach(function(param) {
      if (codec.parameters[param]) {
        params.push(param + '=' + codec.parameters[param]);
      } else {
        params.push(param);
      }
    });
    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
  }
  return line;
};

// Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
// a=rtcp-fb:98 nack rpsi
SDPUtils.parseRtcpFb = function(line) {
  var parts = line.substr(line.indexOf(' ') + 1).split(' ');
  return {
    type: parts.shift(),
    parameter: parts.join(' ')
  };
};
// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
SDPUtils.writeRtcpFb = function(codec) {
  var lines = '';
  var pt = codec.payloadType;
  if (codec.preferredPayloadType !== undefined) {
    pt = codec.preferredPayloadType;
  }
  if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
    // FIXME: special handling for trr-int?
    codec.rtcpFeedback.forEach(function(fb) {
      lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
      (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
          '\r\n';
    });
  }
  return lines;
};

// Parses an RFC 5576 ssrc media attribute. Sample input:
// a=ssrc:3735928559 cname:something
SDPUtils.parseSsrcMedia = function(line) {
  var sp = line.indexOf(' ');
  var parts = {
    ssrc: parseInt(line.substr(7, sp - 7), 10)
  };
  var colon = line.indexOf(':', sp);
  if (colon > -1) {
    parts.attribute = line.substr(sp + 1, colon - sp - 1);
    parts.value = line.substr(colon + 1);
  } else {
    parts.attribute = line.substr(sp + 1);
  }
  return parts;
};

SDPUtils.parseSsrcGroup = function(line) {
  var parts = line.substr(13).split(' ');
  return {
    semantics: parts.shift(),
    ssrcs: parts.map(function(ssrc) {
      return parseInt(ssrc, 10);
    })
  };
};

// Extracts the MID (RFC 5888) from a media section.
// returns the MID or undefined if no mid line was found.
SDPUtils.getMid = function(mediaSection) {
  var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
  if (mid) {
    return mid.substr(6);
  }
};

SDPUtils.parseFingerprint = function(line) {
  var parts = line.substr(14).split(' ');
  return {
    algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
    value: parts[1]
  };
};

// Extracts DTLS parameters from SDP media section or sessionpart.
// FIXME: for consistency with other functions this should only
//   get the fingerprint line as input. See also getIceParameters.
SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
  var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
      'a=fingerprint:');
  // Note: a=setup line is ignored since we use the 'auto' role.
  // Note2: 'algorithm' is not case sensitive except in Edge.
  return {
    role: 'auto',
    fingerprints: lines.map(SDPUtils.parseFingerprint)
  };
};

// Serializes DTLS parameters to SDP.
SDPUtils.writeDtlsParameters = function(params, setupType) {
  var sdp = 'a=setup:' + setupType + '\r\n';
  params.fingerprints.forEach(function(fp) {
    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
  });
  return sdp;
};
// Parses ICE information from SDP media section or sessionpart.
// FIXME: for consistency with other functions this should only
//   get the ice-ufrag and ice-pwd lines as input.
SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
  var lines = SDPUtils.splitLines(mediaSection);
  // Search in session part, too.
  lines = lines.concat(SDPUtils.splitLines(sessionpart));
  var iceParameters = {
    usernameFragment: lines.filter(function(line) {
      return line.indexOf('a=ice-ufrag:') === 0;
    })[0].substr(12),
    password: lines.filter(function(line) {
      return line.indexOf('a=ice-pwd:') === 0;
    })[0].substr(10)
  };
  return iceParameters;
};

// Serializes ICE parameters to SDP.
SDPUtils.writeIceParameters = function(params) {
  return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
      'a=ice-pwd:' + params.password + '\r\n';
};

// Parses the SDP media section and returns RTCRtpParameters.
SDPUtils.parseRtpParameters = function(mediaSection) {
  var description = {
    codecs: [],
    headerExtensions: [],
    fecMechanisms: [],
    rtcp: []
  };
  var lines = SDPUtils.splitLines(mediaSection);
  var mline = lines[0].split(' ');
  for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
    var pt = mline[i];
    var rtpmapline = SDPUtils.matchPrefix(
        mediaSection, 'a=rtpmap:' + pt + ' ')[0];
    if (rtpmapline) {
      var codec = SDPUtils.parseRtpMap(rtpmapline);
      var fmtps = SDPUtils.matchPrefix(
          mediaSection, 'a=fmtp:' + pt + ' ');
      // Only the first a=fmtp:<pt> is considered.
      codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
      codec.rtcpFeedback = SDPUtils.matchPrefix(
          mediaSection, 'a=rtcp-fb:' + pt + ' ')
        .map(SDPUtils.parseRtcpFb);
      description.codecs.push(codec);
      // parse FEC mechanisms from rtpmap lines.
      switch (codec.name.toUpperCase()) {
        case 'RED':
        case 'ULPFEC':
          description.fecMechanisms.push(codec.name.toUpperCase());
          break;
        default: // only RED and ULPFEC are recognized as FEC mechanisms.
          break;
      }
    }
  }
  SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
    description.headerExtensions.push(SDPUtils.parseExtmap(line));
  });
  // FIXME: parse rtcp.
  return description;
};

// Generates parts of the SDP media section describing the capabilities /
// parameters.
SDPUtils.writeRtpDescription = function(kind, caps) {
  var sdp = '';

  // Build the mline.
  sdp += 'm=' + kind + ' ';
  sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
  sdp += ' UDP/TLS/RTP/SAVPF ';
  sdp += caps.codecs.map(function(codec) {
    if (codec.preferredPayloadType !== undefined) {
      return codec.preferredPayloadType;
    }
    return codec.payloadType;
  }).join(' ') + '\r\n';

  sdp += 'c=IN IP4 0.0.0.0\r\n';
  sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';

  // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
  caps.codecs.forEach(function(codec) {
    sdp += SDPUtils.writeRtpMap(codec);
    sdp += SDPUtils.writeFmtp(codec);
    sdp += SDPUtils.writeRtcpFb(codec);
  });
  var maxptime = 0;
  caps.codecs.forEach(function(codec) {
    if (codec.maxptime > maxptime) {
      maxptime = codec.maxptime;
    }
  });
  if (maxptime > 0) {
    sdp += 'a=maxptime:' + maxptime + '\r\n';
  }
  sdp += 'a=rtcp-mux\r\n';

  if (caps.headerExtensions) {
    caps.headerExtensions.forEach(function(extension) {
      sdp += SDPUtils.writeExtmap(extension);
    });
  }
  // FIXME: write fecMechanisms.
  return sdp;
};

// Parses the SDP media section and returns an array of
// RTCRtpEncodingParameters.
SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
  var encodingParameters = [];
  var description = SDPUtils.parseRtpParameters(mediaSection);
  var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
  var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;

  // filter a=ssrc:... cname:, ignore PlanB-msid
  var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
  .map(function(line) {
    return SDPUtils.parseSsrcMedia(line);
  })
  .filter(function(parts) {
    return parts.attribute === 'cname';
  });
  var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
  var secondarySsrc;

  var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
  .map(function(line) {
    var parts = line.substr(17).split(' ');
    return parts.map(function(part) {
      return parseInt(part, 10);
    });
  });
  if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
    secondarySsrc = flows[0][1];
  }

  description.codecs.forEach(function(codec) {
    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
      var encParam = {
        ssrc: primarySsrc,
        codecPayloadType: parseInt(codec.parameters.apt, 10)
      };
      if (primarySsrc && secondarySsrc) {
        encParam.rtx = {ssrc: secondarySsrc};
      }
      encodingParameters.push(encParam);
      if (hasRed) {
        encParam = JSON.parse(JSON.stringify(encParam));
        encParam.fec = {
          ssrc: primarySsrc,
          mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
        };
        encodingParameters.push(encParam);
      }
    }
  });
  if (encodingParameters.length === 0 && primarySsrc) {
    encodingParameters.push({
      ssrc: primarySsrc
    });
  }

  // we support both b=AS and b=TIAS but interpret AS as TIAS.
  var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
  if (bandwidth.length) {
    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
      bandwidth = parseInt(bandwidth[0].substr(7), 10);
    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
      // use formula from JSEP to convert b=AS to TIAS value.
      bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95
          - (50 * 40 * 8);
    } else {
      bandwidth = undefined;
    }
    encodingParameters.forEach(function(params) {
      params.maxBitrate = bandwidth;
    });
  }
  return encodingParameters;
};

// parses http://draft.ortc.org/#rtcrtcpparameters*
SDPUtils.parseRtcpParameters = function(mediaSection) {
  var rtcpParameters = {};

  // Gets the first SSRC. Note tha with RTX there might be multiple
  // SSRCs.
  var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
      .map(function(line) {
        return SDPUtils.parseSsrcMedia(line);
      })
      .filter(function(obj) {
        return obj.attribute === 'cname';
      })[0];
  if (remoteSsrc) {
    rtcpParameters.cname = remoteSsrc.value;
    rtcpParameters.ssrc = remoteSsrc.ssrc;
  }

  // Edge uses the compound attribute instead of reducedSize
  // compound is !reducedSize
  var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
  rtcpParameters.reducedSize = rsize.length > 0;
  rtcpParameters.compound = rsize.length === 0;

  // parses the rtcp-mux attrіbute.
  // Note that Edge does not support unmuxed RTCP.
  var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
  rtcpParameters.mux = mux.length > 0;

  return rtcpParameters;
};

// parses either a=msid: or a=ssrc:... msid lines and returns
// the id of the MediaStream and MediaStreamTrack.
SDPUtils.parseMsid = function(mediaSection) {
  var parts;
  var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
  if (spec.length === 1) {
    parts = spec[0].substr(7).split(' ');
    return {stream: parts[0], track: parts[1]};
  }
  var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
  .map(function(line) {
    return SDPUtils.parseSsrcMedia(line);
  })
  .filter(function(msidParts) {
    return msidParts.attribute === 'msid';
  });
  if (planB.length > 0) {
    parts = planB[0].value.split(' ');
    return {stream: parts[0], track: parts[1]};
  }
};

// Generate a session ID for SDP.
// https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
// recommends using a cryptographically random +ve 64-bit value
// but right now this should be acceptable and within the right range
SDPUtils.generateSessionId = function() {
  return Math.random().toString().substr(2, 21);
};

// Write boilder plate for start of SDP
// sessId argument is optional - if not supplied it will
// be generated randomly
// sessVersion is optional and defaults to 2
// sessUser is optional and defaults to 'thisisadapterortc'
SDPUtils.writeSessionBoilerplate = function(sessId, sessVer, sessUser) {
  var sessionId;
  var version = sessVer !== undefined ? sessVer : 2;
  if (sessId) {
    sessionId = sessId;
  } else {
    sessionId = SDPUtils.generateSessionId();
  }
  var user = sessUser || 'thisisadapterortc';
  // FIXME: sess-id should be an NTP timestamp.
  return 'v=0\r\n' +
      'o=' + user + ' ' + sessionId + ' ' + version +
        ' IN IP4 127.0.0.1\r\n' +
      's=-\r\n' +
      't=0 0\r\n';
};

SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
  var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

  // Map ICE parameters (ufrag, pwd) to SDP.
  sdp += SDPUtils.writeIceParameters(
      transceiver.iceGatherer.getLocalParameters());

  // Map DTLS parameters to SDP.
  sdp += SDPUtils.writeDtlsParameters(
      transceiver.dtlsTransport.getLocalParameters(),
      type === 'offer' ? 'actpass' : 'active');

  sdp += 'a=mid:' + transceiver.mid + '\r\n';

  if (transceiver.direction) {
    sdp += 'a=' + transceiver.direction + '\r\n';
  } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
    sdp += 'a=sendrecv\r\n';
  } else if (transceiver.rtpSender) {
    sdp += 'a=sendonly\r\n';
  } else if (transceiver.rtpReceiver) {
    sdp += 'a=recvonly\r\n';
  } else {
    sdp += 'a=inactive\r\n';
  }

  if (transceiver.rtpSender) {
    // spec.
    var msid = 'msid:' + stream.id + ' ' +
        transceiver.rtpSender.track.id + '\r\n';
    sdp += 'a=' + msid;

    // for Chrome.
    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
        ' ' + msid;
    if (transceiver.sendEncodingParameters[0].rtx) {
      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
          ' ' + msid;
      sdp += 'a=ssrc-group:FID ' +
          transceiver.sendEncodingParameters[0].ssrc + ' ' +
          transceiver.sendEncodingParameters[0].rtx.ssrc +
          '\r\n';
    }
  }
  // FIXME: this should be written by writeRtpDescription.
  sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
      ' cname:' + SDPUtils.localCName + '\r\n';
  if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
        ' cname:' + SDPUtils.localCName + '\r\n';
  }
  return sdp;
};

// Gets the direction from the mediaSection or the sessionpart.
SDPUtils.getDirection = function(mediaSection, sessionpart) {
  // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
  var lines = SDPUtils.splitLines(mediaSection);
  for (var i = 0; i < lines.length; i++) {
    switch (lines[i]) {
      case 'a=sendrecv':
      case 'a=sendonly':
      case 'a=recvonly':
      case 'a=inactive':
        return lines[i].substr(2);
      default:
        // FIXME: What should happen here?
    }
  }
  if (sessionpart) {
    return SDPUtils.getDirection(sessionpart);
  }
  return 'sendrecv';
};

SDPUtils.getKind = function(mediaSection) {
  var lines = SDPUtils.splitLines(mediaSection);
  var mline = lines[0].split(' ');
  return mline[0].substr(2);
};

SDPUtils.isRejected = function(mediaSection) {
  return mediaSection.split(' ', 2)[1] === '0';
};

SDPUtils.parseMLine = function(mediaSection) {
  var lines = SDPUtils.splitLines(mediaSection);
  var parts = lines[0].substr(2).split(' ');
  return {
    kind: parts[0],
    port: parseInt(parts[1], 10),
    protocol: parts[2],
    fmt: parts.slice(3).join(' ')
  };
};

SDPUtils.parseOLine = function(mediaSection) {
  var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
  var parts = line.substr(2).split(' ');
  return {
    username: parts[0],
    sessionId: parts[1],
    sessionVersion: parseInt(parts[2], 10),
    netType: parts[3],
    addressType: parts[4],
    address: parts[5]
  };
};

// a very naive interpretation of a valid SDP.
SDPUtils.isValidSDP = function(blob) {
  if (typeof blob !== 'string' || blob.length === 0) {
    return false;
  }
  var lines = SDPUtils.splitLines(blob);
  for (var i = 0; i < lines.length; i++) {
    if (lines[i].length < 2 || lines[i].charAt(1) !== '=') {
      return false;
    }
    // TODO: check the modifier a bit more.
  }
  return true;
};

// Expose public methods.
if (typeof module === 'object') {
  module.exports = SDPUtils;
}

},{}]},{},[1])(1)
});
