livecodingspace-app/public/vwf/view/webrtc/adapter-latest.js

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/*
 *  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 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) {
    // 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;
}

// 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;
}


// 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);
  var e = new Event('addtrack'); // TODO: MediaStreamTrackEvent
  e.track = track;
  stream.dispatchEvent(e);
}

function removeTrackFromStreamAndFireEvent(track, stream) {
  stream.removeTrack(track);
  var e = new Event('removetrack'); // TODO: MediaStreamTrackEvent
  e.track = track;
  stream.dispatchEvent(e);
}

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);
  });
}

function makeError(name, description) {
  var e = new Error(description);
  e.name = name;
  return e;
}

module.exports = function(window, edgeVersion) {
  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.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 = 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;
  };

  // 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.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.
  // (whih is not yet the same as the WebRTC 1.0 transceiver)
  RTCPeerConnection.prototype._createTransceiver = function(kind) {
    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;
    }
    this.transceivers.push(transceiver);
    return transceiver;
  };

  RTCPeerConnection.prototype.addTrack = function(track, stream) {
    var alreadyExists = this.transceivers.find(function(s) {
      return s.track === track;
    });

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

    if (this.signalingState === 'closed') {
      throw makeError('InvalidStateError',
          'Attempted to call addTrack on a closed peerconnection.');
    }

    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 (!(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].candidates = [];
    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].candidates !== null) {
        pc.transceivers[sdpMLineIndex].candidates.push(event.candidate);
      }
    };
    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 candidates = this.transceivers[sdpMLineIndex].candidates;
    this.transceivers[sdpMLineIndex].candidates = 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;
        event.candidate.candidate = SDPUtils.writeCandidate(cand);
      }

      // update local description.
      var sections = SDPUtils.splitSections(pc.localDescription.sdp);
      if (!end) {
        sections[event.candidate.sdpMLineIndex + 1] +=
            'a=' + event.candidate.candidate + '\r\n';
      } else {
        sections[event.candidate.sdpMLineIndex + 1] +=
            'a=end-of-candidates\r\n';
      }
      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() {
      candidates.forEach(function(candidate) {
        var e = new Event('RTCIceGatherEvent');
        e.candidate = candidate;
        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._updateConnectionState();
    };

    var dtlsTransport = new window.RTCDtlsTransport(iceTransport);
    dtlsTransport.ondtlsstatechange = function() {
      pc._updateConnectionState();
    };
    dtlsTransport.onerror = function() {
      // onerror does not set state to failed by itpc.
      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;
      }
      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;

    if (!isActionAllowedInSignalingState('setLocalDescription',
        description.type, this.signalingState) || this._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;
      });

      this.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.isDatachannel) {
          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);
        }
      });
    }

    this.localDescription = {
      type: description.type,
      sdp: description.sdp
    };
    switch (description.type) {
      case 'offer':
        this._updateSignalingState('have-local-offer');
        break;
      case 'answer':
        this._updateSignalingState('stable');
        break;
      default:
        throw new TypeError('unsupported type "' + description.type +
            '"');
    }

    return Promise.resolve();
  };

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

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

    var streams = {};
    this.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;
    this.usingBundle = usingBundle;
    var iceOptions = SDPUtils.matchPrefix(sessionpart,
        'a=ice-options:')[0];
    if (iceOptions) {
      this.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
          .indexOf('trickle') >= 0;
    } else {
      this.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 (kind === 'application' && protocol === 'DTLS/SCTP') {
        pc.transceivers[sdpMLineIndex] = {
          mid: mid,
          isDatachannel: true
        };
        return;
      }

      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);
          }
        }

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

    this.remoteDescription = {
      type: description.type,
      sdp: description.sdp
    };
    switch (description.type) {
      case 'offer':
        this._updateSignalingState('have-remote-offer');
        break;
      case 'answer':
        this._updateSignalingState('stable');
        break;
      default:
        throw new TypeError('unsupported type "' + description.type +
            '"');
    }
    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 === false) {
        return;
      }
      pc.needNegotiation = false;
      var event = new Event('negotiationneeded');
      pc._dispatchEvent('negotiationneeded', event);
    }, 0);
  };

  // Update the connection state.
  RTCPeerConnection.prototype._updateConnectionState = function() {
    var newState;
    var states = {
      'new': 0,
      closed: 0,
      connecting: 0,
      checking: 0,
      connected: 0,
      completed: 0,
      disconnected: 0,
      failed: 0
    };
    this.transceivers.forEach(function(transceiver) {
      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 || states.checking > 0) {
      newState = 'connecting';
    } else if (states.disconnected > 0) {
      newState = 'disconnected';
    } else if (states.new > 0) {
      newState = 'new';
    } else if (states.connected > 0 || states.completed > 0) {
      newState = 'connected';
    }

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

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

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

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

    this.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) {
        this._createTransceiver('audio');
        numAudioTracks--;
      }
      if (numVideoTracks > 0) {
        this._createTransceiver('video');
        numVideoTracks--;
      }
    }

    var sdp = SDPUtils.writeSessionBoilerplate(this._sdpSessionId,
        this._sdpSessionVersion++);
    this.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 = 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';
        }
      });

      // 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 (this._config.bundlePolicy !== 'max-compat') {
      sdp += 'a=group:BUNDLE ' + this.transceivers.map(function(t) {
        return t.mid;
      }).join(' ') + '\r\n';
    }
    sdp += 'a=ice-options:trickle\r\n';

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

    var sdp = SDPUtils.writeSessionBoilerplate(this._sdpSessionId,
        this._sdpSessionVersion++);
    if (this.usingBundle) {
      sdp += 'a=group:BUNDLE ' + this.transceivers.map(function(t) {
        return t.mid;
      }).join(' ') + '\r\n';
    }
    var mediaSectionsInOffer = SDPUtils.splitSections(
        this.remoteDescription.sdp).length - 1;
    this.transceivers.forEach(function(transceiver, sdpMLineIndex) {
      if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
        return;
      }
      if (transceiver.isDatachannel) {
        sdp += 'm=application 0 DTLS/SCTP 5000\r\n' +
            'c=IN IP4 0.0.0.0\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 sections;
    if (!candidate || candidate.candidate === '') {
      for (var j = 0; j < this.transceivers.length; j++) {
        if (this.transceivers[j].isDatachannel) {
          continue;
        }
        this.transceivers[j].iceTransport.addRemoteCandidate({});
        sections = SDPUtils.splitSections(this.remoteDescription.sdp);
        sections[j + 1] += 'a=end-of-candidates\r\n';
        this.remoteDescription.sdp = sections.join('');
        if (this.usingBundle) {
          break;
        }
      }
    } else if (!(candidate.sdpMLineIndex !== undefined || candidate.sdpMid)) {
      throw new TypeError('sdpMLineIndex or sdpMid required');
    } else if (!this.remoteDescription) {
      return Promise.reject(makeError('InvalidStateError',
          'Can not add ICE candidate without a remote description'));
    } else {
      var sdpMLineIndex = candidate.sdpMLineIndex;
      if (candidate.sdpMid) {
        for (var i = 0; i < this.transceivers.length; i++) {
          if (this.transceivers[i].mid === candidate.sdpMid) {
            sdpMLineIndex = i;
            break;
          }
        }
      }
      var transceiver = this.transceivers[sdpMLineIndex];
      if (transceiver) {
        if (transceiver.isDatachannel) {
          return Promise.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 Promise.resolve();
        }
        // Ignore RTCP candidates, we assume RTCP-MUX.
        if (cand.component && cand.component !== 1) {
          return Promise.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 !== this.transceivers[0].iceTransport)) {
          if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
            return Promise.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.splitSections(this.remoteDescription.sdp);
        sections[sdpMLineIndex + 1] += 'a=' +
            (cand.type ? candidateString : 'end-of-candidates')
            + '\r\n';
        this.remoteDescription.sdp = sections.join('');
      } else {
        return Promise.reject(makeError('OperationError',
            'Can not add ICE candidate'));
      }
    }
    return Promise.resolve();
  };

  RTCPeerConnection.prototype.getStats = function() {
    var promises = [];
    this.transceivers.forEach(function(transceiver) {
      ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
          'dtlsTransport'].forEach(function(method) {
            if (transceiver[method]) {
              promises.push(transceiver[method].getStats());
            }
          });
    });
    var fixStatsType = function(stat) {
      return {
        inboundrtp: 'inbound-rtp',
        outboundrtp: 'outbound-rtp',
        candidatepair: 'candidate-pair',
        localcandidate: 'local-candidate',
        remotecandidate: 'remote-candidate'
      }[stat.type] || stat.type;
    };
    return new Promise(function(resolve) {
      // shim getStats with maplike support
      var results = new Map();
      Promise.all(promises).then(function(res) {
        res.forEach(function(result) {
          Object.keys(result).forEach(function(id) {
            result[id].type = fixStatsType(result[id]);
            results.set(id, result[id]);
          });
        });
        resolve(results);
      });
    });
  };

  // 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":2}],2:[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 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],
    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.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); // was: relAddr
    sdp.push('rport');
    sdp.push(candidate.relatedPort); // was: relPort
  }
  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
    sdp.push('tcptype');
    sdp.push(candidate.tcpType);
  }
  if (candidate.ufrag) {
    sdp.push('ufrag');
    sdp.push(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
  // was: channels
  parsed.numChannels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
  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;
  }
  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
      (codec.numChannels !== 1 ? '/' + codec.numChannels : '') + '\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) {
      params.push(param + '=' + codec.parameters[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;
};

// 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';

  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.split(' ');
    parts.shift();
    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),
        rtx: {
          ssrc: secondarySsrc
        }
      };
      encodingParameters.push(encParam);
      if (hasRed) {
        encParam = JSON.parse(JSON.stringify(encParam));
        encParam.fec = {
          ssrc: secondarySsrc,
          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 = {};

  var cname;
  // Gets the first SSRC. Note that 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(parts) {
    return parts.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
SDPUtils.writeSessionBoilerplate = function(sessId, sessVer) {
  var sessionId;
  var version = sessVer !== undefined ? sessVer : 2;
  if (sessId) {
    sessionId = sessId;
  } else {
    sessionId = SDPUtils.generateSessionId();
  }
  // FIXME: sess-id should be an NTP timestamp.
  return 'v=0\r\n' +
      'o=thisisadapterortc ' + 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 mline = lines[0].split(' ');
  return {
    kind: mline[0].substr(2),
    port: parseInt(mline[1], 10),
    protocol: mline[2],
    fmt: mline.slice(3).join(' ')
  };
};

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

},{}],3:[function(require,module,exports){
(function (global){
/*
 *  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 adapterFactory = require('./adapter_factory.js');
module.exports = adapterFactory({window: global.window});

}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{"./adapter_factory.js":4}],4:[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 utils = require('./utils');
// Shimming starts here.
module.exports = function(dependencies, opts) {
  var window = dependencies && dependencies.window;

  var options = {
    shimChrome: true,
    shimFirefox: true,
    shimEdge: true,
    shimSafari: true,
  };

  for (var key in opts) {
    if (hasOwnProperty.call(opts, key)) {
      options[key] = opts[key];
    }
  }

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

  // Uncomment the line below if you want logging to occur, including logging
  // for the switch statement below. Can also be turned on in the browser via
  // adapter.disableLog(false), but then logging from the switch statement below
  // will not appear.
  // require('./utils').disableLog(false);

  // Browser shims.
  var chromeShim = require('./chrome/chrome_shim') || null;
  var edgeShim = require('./edge/edge_shim') || null;
  var firefoxShim = require('./firefox/firefox_shim') || null;
  var safariShim = require('./safari/safari_shim') || null;
  var commonShim = require('./common_shim') || null;

  // Export to the adapter global object visible in the browser.
  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;
      commonShim.shimCreateObjectURL(window);

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

      commonShim.shimRTCIceCandidate(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;
      commonShim.shimCreateObjectURL(window);

      firefoxShim.shimGetUserMedia(window);
      firefoxShim.shimSourceObject(window);
      firefoxShim.shimPeerConnection(window);
      firefoxShim.shimOnTrack(window);
      firefoxShim.shimRemoveStream(window);

      commonShim.shimRTCIceCandidate(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;
      commonShim.shimCreateObjectURL(window);

      edgeShim.shimGetUserMedia(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;
      commonShim.shimCreateObjectURL(window);

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

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

  return adapter;
};

},{"./chrome/chrome_shim":5,"./common_shim":7,"./edge/edge_shim":8,"./firefox/firefox_shim":10,"./safari/safari_shim":12,"./utils":13}],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';
var utils = require('../utils.js');
var logging = utils.log;

module.exports = {
  shimGetUserMedia: require('./getusermedia'),
  shimMediaStream: function(window) {
    window.MediaStream = window.MediaStream || window.webkitMediaStream;
  },

  shimOnTrack: function(window) {
    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
        window.RTCPeerConnection.prototype)) {
      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
        get: function() {
          return this._ontrack;
        },
        set: function(f) {
          if (this._ontrack) {
            this.removeEventListener('track', this._ontrack);
          }
          this.addEventListener('track', this._ontrack = f);
        }
      });
      var origSetRemoteDescription =
          window.RTCPeerConnection.prototype.setRemoteDescription;
      window.RTCPeerConnection.prototype.setRemoteDescription = function() {
        var pc = this;
        if (!pc._ontrackpoly) {
          pc._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;
              if (window.RTCPeerConnection.prototype.getReceivers) {
                receiver = pc.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];
              pc.dispatchEvent(event);
            });
            e.stream.getTracks().forEach(function(track) {
              var receiver;
              if (window.RTCPeerConnection.prototype.getReceivers) {
                receiver = pc.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];
              pc.dispatchEvent(event);
            });
          };
          pc.addEventListener('addstream', pc._ontrackpoly);
        }
        return origSetRemoteDescription.apply(pc, arguments);
      };
    } else if (!('RTCRtpTransceiver' in window)) {
      utils.wrapPeerConnectionEvent(window, 'track', function(e) {
        if (!e.transceiver) {
          e.transceiver = {receiver: e.receiver};
        }
        return e;
      });
    }
  },

  shimGetSendersWithDtmf: function(window) {
    // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
    if (typeof window === 'object' && window.RTCPeerConnection &&
        !('getSenders' in window.RTCPeerConnection.prototype) &&
        'createDTMFSender' in window.RTCPeerConnection.prototype) {
      var shimSenderWithDtmf = function(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 pc = this;
          var sender = origAddTrack.apply(pc, arguments);
          if (!sender) {
            sender = shimSenderWithDtmf(pc, track);
            pc._senders.push(sender);
          }
          return sender;
        };

        var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
        window.RTCPeerConnection.prototype.removeTrack = function(sender) {
          var pc = this;
          origRemoveTrack.apply(pc, arguments);
          var idx = pc._senders.indexOf(sender);
          if (idx !== -1) {
            pc._senders.splice(idx, 1);
          }
        };
      }
      var origAddStream = window.RTCPeerConnection.prototype.addStream;
      window.RTCPeerConnection.prototype.addStream = function(stream) {
        var pc = this;
        pc._senders = pc._senders || [];
        origAddStream.apply(pc, [stream]);
        stream.getTracks().forEach(function(track) {
          pc._senders.push(shimSenderWithDtmf(pc, track));
        });
      };

      var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
      window.RTCPeerConnection.prototype.removeStream = function(stream) {
        var pc = this;
        pc._senders = pc._senders || [];
        origRemoveStream.apply(pc, [stream]);

        stream.getTracks().forEach(function(track) {
          var sender = pc._senders.find(function(s) {
            return s.track === track;
          });
          if (sender) {
            pc._senders.splice(pc._senders.indexOf(sender), 1); // remove sender
          }
        });
      };
    } else if (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 pc = this;
        var senders = origGetSenders.apply(pc, []);
        senders.forEach(function(sender) {
          sender._pc = pc;
        });
        return senders;
      };

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

  shimSourceObject: function(window) {
    var URL = window && window.URL;

    if (typeof window === 'object') {
      if (window.HTMLMediaElement &&
        !('srcObject' in window.HTMLMediaElement.prototype)) {
        // Shim the srcObject property, once, when HTMLMediaElement is found.
        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
          get: function() {
            return this._srcObject;
          },
          set: function(stream) {
            var self = this;
            // Use _srcObject as a private property for this shim
            this._srcObject = stream;
            if (this.src) {
              URL.revokeObjectURL(this.src);
            }

            if (!stream) {
              this.src = '';
              return undefined;
            }
            this.src = URL.createObjectURL(stream);
            // We need to recreate the blob url when a track is added or
            // removed. Doing it manually since we want to avoid a recursion.
            stream.addEventListener('addtrack', function() {
              if (self.src) {
                URL.revokeObjectURL(self.src);
              }
              self.src = URL.createObjectURL(stream);
            });
            stream.addEventListener('removetrack', function() {
              if (self.src) {
                URL.revokeObjectURL(self.src);
              }
              self.src = URL.createObjectURL(stream);
            });
          }
        });
      }
    }
  },

  shimAddTrackRemoveTrackWithNative: function(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 pc = this;
      this._shimmedLocalStreams = this._shimmedLocalStreams || {};
      return Object.keys(this._shimmedLocalStreams).map(function(streamId) {
        return pc._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 pc = this;
      this._shimmedLocalStreams = this._shimmedLocalStreams || {};

      stream.getTracks().forEach(function(track) {
        var alreadyExists = pc.getSenders().find(function(s) {
          return s.track === track;
        });
        if (alreadyExists) {
          throw new DOMException('Track already exists.',
              'InvalidAccessError');
        }
      });
      var existingSenders = pc.getSenders();
      origAddStream.apply(this, arguments);
      var newSenders = pc.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 pc = this;
      this._shimmedLocalStreams = this._shimmedLocalStreams || {};
      if (sender) {
        Object.keys(this._shimmedLocalStreams).forEach(function(streamId) {
          var idx = pc._shimmedLocalStreams[streamId].indexOf(sender);
          if (idx !== -1) {
            pc._shimmedLocalStreams[streamId].splice(idx, 1);
          }
          if (pc._shimmedLocalStreams[streamId].length === 1) {
            delete pc._shimmedLocalStreams[streamId];
          }
        });
      }
      return origRemoveTrack.apply(this, arguments);
    };
  },

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

    var origAddStream = window.RTCPeerConnection.prototype.addStream;
    window.RTCPeerConnection.prototype.addStream = function(stream) {
      var pc = this;
      pc._streams = pc._streams || {};
      pc._reverseStreams = pc._reverseStreams || {};

      stream.getTracks().forEach(function(track) {
        var alreadyExists = pc.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 (!pc._reverseStreams[stream.id]) {
        var newStream = new window.MediaStream(stream.getTracks());
        pc._streams[stream.id] = newStream;
        pc._reverseStreams[newStream.id] = stream;
        stream = newStream;
      }
      origAddStream.apply(pc, [stream]);
    };

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

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

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

      pc._streams = pc._streams || {};
      pc._reverseStreams = pc._reverseStreams || {};
      var oldStream = pc._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() {
          pc.dispatchEvent(new Event('negotiationneeded'));
        });
      } else {
        var newStream = new window.MediaStream([track]);
        pc._streams[stream.id] = newStream;
        pc._reverseStreams[newStream.id] = stream;
        pc.addStream(newStream);
      }
      return pc.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 pc = this;
        var args = arguments;
        var isLegacyCall = arguments.length &&
            typeof arguments[0] === 'function';
        if (isLegacyCall) {
          return nativeMethod.apply(pc, [
            function(description) {
              var desc = replaceInternalStreamId(pc, description);
              args[0].apply(null, [desc]);
            },
            function(err) {
              if (args[1]) {
                args[1].apply(null, err);
              }
            }, arguments[2]
          ]);
        }
        return nativeMethod.apply(pc, arguments)
        .then(function(description) {
          return replaceInternalStreamId(pc, description);
        });
      };
    });

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

    window.RTCPeerConnection.prototype.removeTrack = function(sender) {
      var pc = this;
      if (pc.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 === pc;
      if (!isLocal) {
        throw new DOMException('Sender was not created by this connection.',
            'InvalidAccessError');
      }

      // Search for the native stream the senders track belongs to.
      pc._streams = pc._streams || {};
      var stream;
      Object.keys(pc._streams).forEach(function(streamid) {
        var hasTrack = pc._streams[streamid].getTracks().find(function(track) {
          return sender.track === track;
        });
        if (hasTrack) {
          stream = pc._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.
          pc.removeStream(pc._reverseStreams[stream.id]);
        } else {
          // relying on the same odd chrome behaviour as above.
          stream.removeTrack(sender.track);
        }
        pc.dispatchEvent(new Event('negotiationneeded'));
      }
    };
  },

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

    // The RTCPeerConnection object.
    if (!window.RTCPeerConnection) {
      window.RTCPeerConnection = function(pcConfig, pcConstraints) {
        // Translate iceTransportPolicy to iceTransports,
        // see https://code.google.com/p/webrtc/issues/detail?id=4869
        // this was fixed in M56 along with unprefixing RTCPeerConnection.
        logging('PeerConnection');
        if (pcConfig && pcConfig.iceTransportPolicy) {
          pcConfig.iceTransports = pcConfig.iceTransportPolicy;
        }

        return new window.webkitRTCPeerConnection(pcConfig, pcConstraints);
      };
      window.RTCPeerConnection.prototype =
          window.webkitRTCPeerConnection.prototype;
      // wrap static methods. Currently just generateCertificate.
      if (window.webkitRTCPeerConnection.generateCertificate) {
        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
          get: function() {
            return window.webkitRTCPeerConnection.generateCertificate;
          }
        });
      }
    } else {
      // 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;
              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.
      Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
        get: function() {
          return OrigPeerConnection.generateCertificate;
        }
      });
    }

    var origGetStats = window.RTCPeerConnection.prototype.getStats;
    window.RTCPeerConnection.prototype.getStats = function(selector,
        successCallback, errorCallback) {
      var pc = 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(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(stats) {
        return new Map(Object.keys(stats).map(function(key) {
          return [key, stats[key]];
        }));
      };

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

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

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

    // add promise support -- natively available in Chrome 51
    if (browserDetails.version < 51) {
      ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
          .forEach(function(method) {
            var nativeMethod = window.RTCPeerConnection.prototype[method];
            window.RTCPeerConnection.prototype[method] = function() {
              var args = arguments;
              var pc = this;
              var promise = new Promise(function(resolve, reject) {
                nativeMethod.apply(pc, [args[0], resolve, reject]);
              });
              if (args.length < 2) {
                return promise;
              }
              return promise.then(function() {
                args[1].apply(null, []);
              },
              function(err) {
                if (args.length >= 3) {
                  args[2].apply(null, [err]);
                }
              });
            };
          });
    }

    // promise support for createOffer and createAnswer. Available (without
    // bugs) since M52: crbug/619289
    if (browserDetails.version < 52) {
      ['createOffer', 'createAnswer'].forEach(function(method) {
        var nativeMethod = window.RTCPeerConnection.prototype[method];
        window.RTCPeerConnection.prototype[method] = function() {
          var pc = this;
          if (arguments.length < 1 || (arguments.length === 1 &&
              typeof arguments[0] === 'object')) {
            var opts = arguments.length === 1 ? arguments[0] : undefined;
            return new Promise(function(resolve, reject) {
              nativeMethod.apply(pc, [resolve, reject, opts]);
            });
          }
          return nativeMethod.apply(this, arguments);
        };
      });
    }

    // 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);
    };
  }
};

},{"../utils.js":13,"./getusermedia":6}],6:[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 utils = require('../utils.js');
var logging = utils.log;

// Expose public methods.
module.exports = function(window) {
  var browserDetails = utils.detectBrowser(window);
  var navigator = window && window.navigator;

  var constraintsToChrome_ = function(c) {
    if (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(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(constraints, func) {
    if (browserDetails.version >= 61) {
      return func(constraints);
    }
    constraints = JSON.parse(JSON.stringify(constraints));
    if (constraints && typeof constraints.audio === 'object') {
      var remap = function(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 === '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;
        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().indexOf(match) !== -1;
              });
            });
            if (!dev && devices.length && matches.indexOf('back') !== -1) {
              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(e) {
    return {
      name: {
        PermissionDeniedError: 'NotAllowedError',
        InvalidStateError: 'NotReadableError',
        DevicesNotFoundError: 'NotFoundError',
        ConstraintNotSatisfiedError: 'OverconstrainedError',
        TrackStartError: 'NotReadableError',
        MediaDeviceFailedDueToShutdown: 'NotReadableError',
        MediaDeviceKillSwitchOn: 'NotReadableError'
      }[e.name] || e.name,
      message: e.message,
      constraint: e.constraintName,
      toString: function() {
        return this.name + (this.message && ': ') + this.message;
      }
    };
  };

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

  navigator.getUserMedia = getUserMedia_;

  // Returns the result of getUserMedia as a Promise.
  var getUserMediaPromise_ = function(constraints) {
    return new Promise(function(resolve, reject) {
      navigator.getUserMedia(constraints, resolve, reject);
    });
  };

  if (!navigator.mediaDevices) {
    navigator.mediaDevices = {
      getUserMedia: getUserMediaPromise_,
      enumerateDevices: function() {
        return new Promise(function(resolve) {
          var kinds = {audio: 'audioinput', video: 'videoinput'};
          return window.MediaStreamTrack.getSources(function(devices) {
            resolve(devices.map(function(device) {
              return {label: device.label,
                kind: kinds[device.kind],
                deviceId: device.id,
                groupId: ''};
            }));
          });
        });
      },
      getSupportedConstraints: function() {
        return {
          deviceId: true, echoCancellation: true, facingMode: true,
          frameRate: true, height: true, width: true
        };
      }
    };
  }

  // A shim for getUserMedia method on the mediaDevices object.
  // TODO(KaptenJansson) remove once implemented in Chrome stable.
  if (!navigator.mediaDevices.getUserMedia) {
    navigator.mediaDevices.getUserMedia = function(constraints) {
      return getUserMediaPromise_(constraints);
    };
  } else {
    // 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));
        });
      });
    };
  }

  // Dummy devicechange event methods.
  // TODO(KaptenJansson) remove once implemented in Chrome stable.
  if (typeof navigator.mediaDevices.addEventListener === 'undefined') {
    navigator.mediaDevices.addEventListener = function() {
      logging('Dummy mediaDevices.addEventListener called.');
    };
  }
  if (typeof navigator.mediaDevices.removeEventListener === 'undefined') {
    navigator.mediaDevices.removeEventListener = function() {
      logging('Dummy mediaDevices.removeEventListener called.');
    };
  }
};

},{"../utils.js":13}],7:[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');
var utils = require('./utils');

module.exports = {
  shimRTCIceCandidate: function(window) {
    // foundation is arbitrarily chosen as an indicator for full support for
    // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
    if (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 === 'object' && args.candidate &&
          args.candidate.indexOf('a=') === 0) {
        args = JSON.parse(JSON.stringify(args));
        args.candidate = args.candidate.substr(2);
      }

      // Augment the native candidate with the parsed fields.
      var nativeCandidate = new NativeRTCIceCandidate(args);
      var parsedCandidate = SDPUtils.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;
    };

    // 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;
    });
  },

  // shimCreateObjectURL must be called before shimSourceObject to avoid loop.

  shimCreateObjectURL: function(window) {
    var URL = window && window.URL;

    if (!(typeof window === 'object' && window.HTMLMediaElement &&
          'srcObject' in window.HTMLMediaElement.prototype &&
        URL.createObjectURL && URL.revokeObjectURL)) {
      // Only shim CreateObjectURL using srcObject if srcObject exists.
      return undefined;
    }

    var nativeCreateObjectURL = URL.createObjectURL.bind(URL);
    var nativeRevokeObjectURL = URL.revokeObjectURL.bind(URL);
    var streams = new Map(), newId = 0;

    URL.createObjectURL = function(stream) {
      if ('getTracks' in stream) {
        var url = 'polyblob:' + (++newId);
        streams.set(url, stream);
        utils.deprecated('URL.createObjectURL(stream)',
            'elem.srcObject = stream');
        return url;
      }
      return nativeCreateObjectURL(stream);
    };
    URL.revokeObjectURL = function(url) {
      nativeRevokeObjectURL(url);
      streams.delete(url);
    };

    var dsc = Object.getOwnPropertyDescriptor(window.HTMLMediaElement.prototype,
                                              'src');
    Object.defineProperty(window.HTMLMediaElement.prototype, 'src', {
      get: function() {
        return dsc.get.apply(this);
      },
      set: function(url) {
        this.srcObject = streams.get(url) || null;
        return dsc.set.apply(this, [url]);
      }
    });

    var nativeSetAttribute = window.HTMLMediaElement.prototype.setAttribute;
    window.HTMLMediaElement.prototype.setAttribute = function() {
      if (arguments.length === 2 &&
          ('' + arguments[0]).toLowerCase() === 'src') {
        this.srcObject = streams.get(arguments[1]) || null;
      }
      return nativeSetAttribute.apply(this, arguments);
    };
  },

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

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

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

    var getRemoteFirefoxVersion = function(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(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 {
          // 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;
        }
      }
      return canSendMaxMessageSize;
    };

    var getMaxMessageSize = function(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 = SDPUtils.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() {
      var pc = this;
      pc._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;
        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() {
            return maxMessageSize;
          }
        });
        pc._sctp = sctp;
      }

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

  shimSendThrowTypeError: function(window) {
    // 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

    var origCreateDataChannel =
      window.RTCPeerConnection.prototype.createDataChannel;
    window.RTCPeerConnection.prototype.createDataChannel = function() {
      var pc = this;
      var dataChannel = origCreateDataChannel.apply(pc, arguments);
      var origDataChannelSend = dataChannel.send;

      // Patch 'send' method
      dataChannel.send = function() {
        var dc = this;
        var data = arguments[0];
        var length = data.length || data.size || data.byteLength;
        if (length > pc.sctp.maxMessageSize) {
          throw new DOMException('Message too large (can send a maximum of ' +
            pc.sctp.maxMessageSize + ' bytes)', 'TypeError');
        }
        return origDataChannelSend.apply(dc, arguments);
      };

      return dataChannel;
    };
  }
};

},{"./utils":13,"sdp":2}],8:[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 utils = require('../utils');
var shimRTCPeerConnection = require('rtcpeerconnection-shim');

module.exports = {
  shimGetUserMedia: require('./getusermedia'),
  shimPeerConnection: function(window) {
    var browserDetails = utils.detectBrowser(window);

    if (window.RTCIceGatherer) {
      // ORTC defines an RTCIceCandidate object but no constructor.
      // Not implemented in Edge.
      if (!window.RTCIceCandidate) {
        window.RTCIceCandidate = function(args) {
          return args;
        };
      }
      // ORTC does not have a session description object but
      // other browsers (i.e. Chrome) that will support both PC and ORTC
      // in the future might have this defined already.
      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(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() {
          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;
        }
      });
    }

    window.RTCPeerConnection =
        shimRTCPeerConnection(window, browserDetails.version);
  },
  shimReplaceTrack: function(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":13,"./getusermedia":9,"rtcpeerconnection-shim":1}],9:[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';

// Expose public methods.
module.exports = function(window) {
  var navigator = window && window.navigator;

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

},{}],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';

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

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

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

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

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

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

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

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

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

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

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

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

  shimRemoveStream: function(window) {
    if (!window.RTCPeerConnection ||
        'removeStream' in window.RTCPeerConnection.prototype) {
      return;
    }
    window.RTCPeerConnection.prototype.removeStream = function(stream) {
      var pc = this;
      utils.deprecated('removeStream', 'removeTrack');
      this.getSenders().forEach(function(sender) {
        if (sender.track && stream.getTracks().indexOf(sender.track) !== -1) {
          pc.removeTrack(sender);
        }
      });
    };
  }
};

},{"../utils":13,"./getusermedia":11}],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';

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

// Expose public methods.
module.exports = function(window) {
  var browserDetails = utils.detectBrowser(window);
  var navigator = window && window.navigator;
  var MediaStreamTrack = window && window.MediaStreamTrack;

  var shimError_ = function(e) {
    return {
      name: {
        InternalError: 'NotReadableError',
        NotSupportedError: 'TypeError',
        PermissionDeniedError: 'NotAllowedError',
        SecurityError: 'NotAllowedError'
      }[e.name] || e.name,
      message: {
        'The operation is insecure.': 'The request is not allowed by the ' +
        'user agent or the platform in the current context.'
      }[e.message] || e.message,
      constraint: e.constraint,
      toString: function() {
        return this.name + (this.message && ': ') + this.message;
      }
    };
  };

  // getUserMedia constraints shim.
  var getUserMedia_ = function(constraints, onSuccess, onError) {
    var constraintsToFF37_ = function(c) {
      if (typeof c !== 'object' || c.require) {
        return c;
      }
      var require = [];
      Object.keys(c).forEach(function(key) {
        if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
          return;
        }
        var r = c[key] = (typeof c[key] === 'object') ?
            c[key] : {ideal: c[key]};
        if (r.min !== undefined ||
            r.max !== undefined || r.exact !== undefined) {
          require.push(key);
        }
        if (r.exact !== undefined) {
          if (typeof r.exact === 'number') {
            r. min = r.max = r.exact;
          } else {
            c[key] = r.exact;
          }
          delete r.exact;
        }
        if (r.ideal !== undefined) {
          c.advanced = c.advanced || [];
          var oc = {};
          if (typeof r.ideal === 'number') {
            oc[key] = {min: r.ideal, max: r.ideal};
          } else {
            oc[key] = r.ideal;
          }
          c.advanced.push(oc);
          delete r.ideal;
          if (!Object.keys(r).length) {
            delete c[key];
          }
        }
      });
      if (require.length) {
        c.require = require;
      }
      return c;
    };
    constraints = JSON.parse(JSON.stringify(constraints));
    if (browserDetails.version < 38) {
      logging('spec: ' + JSON.stringify(constraints));
      if (constraints.audio) {
        constraints.audio = constraintsToFF37_(constraints.audio);
      }
      if (constraints.video) {
        constraints.video = constraintsToFF37_(constraints.video);
      }
      logging('ff37: ' + JSON.stringify(constraints));
    }
    return navigator.mozGetUserMedia(constraints, onSuccess, function(e) {
      onError(shimError_(e));
    });
  };

  // Returns the result of getUserMedia as a Promise.
  var getUserMediaPromise_ = function(constraints) {
    return new Promise(function(resolve, reject) {
      getUserMedia_(constraints, resolve, reject);
    });
  };

  // Shim for mediaDevices on older versions.
  if (!navigator.mediaDevices) {
    navigator.mediaDevices = {getUserMedia: getUserMediaPromise_,
      addEventListener: function() { },
      removeEventListener: function() { }
    };
  }
  navigator.mediaDevices.enumerateDevices =
      navigator.mediaDevices.enumerateDevices || function() {
        return new Promise(function(resolve) {
          var infos = [
            {kind: 'audioinput', deviceId: 'default', label: '', groupId: ''},
            {kind: 'videoinput', deviceId: 'default', label: '', groupId: ''}
          ];
          resolve(infos);
        });
      };

  if (browserDetails.version < 41) {
    // Work around http://bugzil.la/1169665
    var orgEnumerateDevices =
        navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices);
    navigator.mediaDevices.enumerateDevices = function() {
      return orgEnumerateDevices().then(undefined, function(e) {
        if (e.name === 'NotFoundError') {
          return [];
        }
        throw e;
      });
    };
  }
  if (browserDetails.version < 49) {
    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
        bind(navigator.mediaDevices);
    navigator.mediaDevices.getUserMedia = function(c) {
      return origGetUserMedia(c).then(function(stream) {
        // Work around https://bugzil.la/802326
        if (c.audio && !stream.getAudioTracks().length ||
            c.video && !stream.getVideoTracks().length) {
          stream.getTracks().forEach(function(track) {
            track.stop();
          });
          throw new DOMException('The object can not be found here.',
                                 'NotFoundError');
        }
        return stream;
      }, function(e) {
        return Promise.reject(shimError_(e));
      });
    };
  }
  if (!(browserDetails.version > 55 &&
      'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
    var remap = function(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 === '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 === 'object') {
          c = JSON.parse(JSON.stringify(c));
          remap(c, 'autoGainControl', 'mozAutoGainControl');
          remap(c, 'noiseSuppression', 'mozNoiseSuppression');
        }
        return nativeApplyConstraints.apply(this, [c]);
      };
    }
  }
  navigator.getUserMedia = function(constraints, onSuccess, onError) {
    if (browserDetails.version < 44) {
      return getUserMedia_(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);
  };
};

},{"../utils":13}],12:[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';
var utils = require('../utils');

module.exports = {
  shimLocalStreamsAPI: function(window) {
    if (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 (!('getStreamById' in window.RTCPeerConnection.prototype)) {
      window.RTCPeerConnection.prototype.getStreamById = function(id) {
        var result = null;
        if (this._localStreams) {
          this._localStreams.forEach(function(stream) {
            if (stream.id === id) {
              result = stream;
            }
          });
        }
        if (this._remoteStreams) {
          this._remoteStreams.forEach(function(stream) {
            if (stream.id === id) {
              result = stream;
            }
          });
        }
        return result;
      };
    }
    if (!('addStream' in window.RTCPeerConnection.prototype)) {
      var _addTrack = window.RTCPeerConnection.prototype.addTrack;
      window.RTCPeerConnection.prototype.addStream = function(stream) {
        if (!this._localStreams) {
          this._localStreams = [];
        }
        if (this._localStreams.indexOf(stream) === -1) {
          this._localStreams.push(stream);
        }
        var pc = this;
        stream.getTracks().forEach(function(track) {
          _addTrack.call(pc, track, stream);
        });
      };

      window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
        if (stream) {
          if (!this._localStreams) {
            this._localStreams = [stream];
          } else if (this._localStreams.indexOf(stream) === -1) {
            this._localStreams.push(stream);
          }
        }
        return _addTrack.call(this, track, stream);
      };
    }
    if (!('removeStream' in window.RTCPeerConnection.prototype)) {
      window.RTCPeerConnection.prototype.removeStream = function(stream) {
        if (!this._localStreams) {
          this._localStreams = [];
        }
        var index = this._localStreams.indexOf(stream);
        if (index === -1) {
          return;
        }
        this._localStreams.splice(index, 1);
        var pc = this;
        var tracks = stream.getTracks();
        this.getSenders().forEach(function(sender) {
          if (tracks.indexOf(sender.track) !== -1) {
            pc.removeTrack(sender);
          }
        });
      };
    }
  },
  shimRemoteStreamsAPI: function(window) {
    if (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() {
          return this._onaddstream;
        },
        set: function(f) {
          var pc = 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 (!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);
            });
          });
        }
      });
    }
  },
  shimCallbacksAPI: function(window) {
    if (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(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(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(candidate, successCallback, failureCallback) {
      var promise = addIceCandidate.apply(this, [candidate]);
      if (!failureCallback) {
        return promise;
      }
      promise.then(successCallback, failureCallback);
      return Promise.resolve();
    };
    prototype.addIceCandidate = withCallback;
  },
  shimGetUserMedia: function(window) {
    var navigator = window && window.navigator;

    if (!navigator.getUserMedia) {
      if (navigator.webkitGetUserMedia) {
        navigator.getUserMedia = navigator.webkitGetUserMedia.bind(navigator);
      } else if (navigator.mediaDevices &&
          navigator.mediaDevices.getUserMedia) {
        navigator.getUserMedia = function(constraints, cb, errcb) {
          navigator.mediaDevices.getUserMedia(constraints)
          .then(cb, errcb);
        }.bind(navigator);
      }
    }
  },
  shimRTCIceServerUrls: function(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() {
          return OrigPeerConnection.generateCertificate;
        }
      });
    }
  },
  shimTrackEventTransceiver: function(window) {
    // Add event.transceiver member over deprecated event.receiver
    if (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() {
          return {receiver: this.receiver};
        }
      });
    }
  },

  shimCreateOfferLegacy: function(window) {
    var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
    window.RTCPeerConnection.prototype.createOffer = function(offerOptions) {
      var pc = this;
      if (offerOptions) {
        var audioTransceiver = pc.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) {
          pc.addTransceiver('audio');
        }

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

},{"../utils":13}],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';

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.
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(e) {
      cb(wrapper(e));
    };
    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() {
      return this['_on' + eventNameToWrap];
    },
    set: function(cb) {
      if (this['_on' + eventNameToWrap]) {
        this.removeEventListener(eventNameToWrap,
            this['_on' + eventNameToWrap]);
        delete this['_on' + eventNameToWrap];
      }
      if (cb) {
        this.addEventListener(eventNameToWrap,
            this['_on' + eventNameToWrap] = cb);
      }
    }
  });
}

// Utility methods.
module.exports = {
  extractVersion: extractVersion,
  wrapPeerConnectionEvent: wrapPeerConnectionEvent,
  disableLog: function(bool) {
    if (typeof bool !== 'boolean') {
      return new Error('Argument type: ' + 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.
   */
  disableWarnings: function(bool) {
    if (typeof bool !== 'boolean') {
      return new Error('Argument type: ' + typeof bool +
          '. Please use a boolean.');
    }
    deprecationWarnings_ = !bool;
    return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled');
  },

  log: function() {
    if (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.
   */
  deprecated: function(oldMethod, newMethod) {
    if (!deprecationWarnings_) {
      return;
    }
    console.warn(oldMethod + ' is deprecated, please use ' + newMethod +
        ' instead.');
  },

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

    // Returned result object.
    var result = {};
    result.browser = null;
    result.version = null;

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

    // Firefox.
    if (navigator.mozGetUserMedia) {
      result.browser = 'firefox';
      result.version = extractVersion(navigator.userAgent,
          /Firefox\/(\d+)\./, 1);
    } else if (navigator.webkitGetUserMedia) {
      // Chrome, Chromium, Webview, Opera, all use the chrome shim for now
      if (window.webkitRTCPeerConnection) {
        result.browser = 'chrome';
        result.version = extractVersion(navigator.userAgent,
          /Chrom(e|ium)\/(\d+)\./, 2);
      } else { // Safari (in an unpublished version) or unknown webkit-based.
        if (navigator.userAgent.match(/Version\/(\d+).(\d+)/)) {
          result.browser = 'safari';
          result.version = extractVersion(navigator.userAgent,
            /AppleWebKit\/(\d+)\./, 1);
        } else { // unknown webkit-based browser.
          result.browser = 'Unsupported webkit-based browser ' +
              'with GUM support but no WebRTC support.';
          return result;
        }
      }
    } 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 (navigator.mediaDevices &&
        navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) {
        // Safari, with webkitGetUserMedia removed.
      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;
  }
};

},{}]},{},[3])(3)
});