RTCPeerConnection.prototype.createOffer = function()

in monitoring-stack-cdk/resources/frontend/connect-rtc.js [4230:4407]
141 lines of code
43 McCabe index (conditional complexity)

      RTCPeerConnection.prototype.createOffer = function() {
        var pc = this;
    
        if (pc._isClosed) {
          return Promise.reject(makeError('InvalidStateError',
              'Can not call createOffer after close'));
        }
    
        var numAudioTracks = pc.transceivers.filter(function(t) {
          return t.kind === 'audio';
        }).length;
        var numVideoTracks = pc.transceivers.filter(function(t) {
          return t.kind === 'video';
        }).length;
    
        // Determine number of audio and video tracks we need to send/recv.
        var offerOptions = arguments[0];
        if (offerOptions) {
          // Reject Chrome legacy constraints.
          if (offerOptions.mandatory || offerOptions.optional) {
            throw new TypeError(
                'Legacy mandatory/optional constraints not supported.');
          }
          if (offerOptions.offerToReceiveAudio !== undefined) {
            if (offerOptions.offerToReceiveAudio === true) {
              numAudioTracks = 1;
            } else if (offerOptions.offerToReceiveAudio === false) {
              numAudioTracks = 0;
            } else {
              numAudioTracks = offerOptions.offerToReceiveAudio;
            }
          }
          if (offerOptions.offerToReceiveVideo !== undefined) {
            if (offerOptions.offerToReceiveVideo === true) {
              numVideoTracks = 1;
            } else if (offerOptions.offerToReceiveVideo === false) {
              numVideoTracks = 0;
            } else {
              numVideoTracks = offerOptions.offerToReceiveVideo;
            }
          }
        }
    
        pc.transceivers.forEach(function(transceiver) {
          if (transceiver.kind === 'audio') {
            numAudioTracks--;
            if (numAudioTracks < 0) {
              transceiver.wantReceive = false;
            }
          } else if (transceiver.kind === 'video') {
            numVideoTracks--;
            if (numVideoTracks < 0) {
              transceiver.wantReceive = false;
            }
          }
        });
    
        // Create M-lines for recvonly streams.
        while (numAudioTracks > 0 || numVideoTracks > 0) {
          if (numAudioTracks > 0) {
            pc._createTransceiver('audio');
            numAudioTracks--;
          }
          if (numVideoTracks > 0) {
            pc._createTransceiver('video');
            numVideoTracks--;
          }
        }
    
        var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
            pc._sdpSessionVersion++);
        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          // For each track, create an ice gatherer, ice transport,
          // dtls transport, potentially rtpsender and rtpreceiver.
          var track = transceiver.track;
          var kind = transceiver.kind;
          var mid = transceiver.mid || SDPUtils.generateIdentifier();
          transceiver.mid = mid;
    
          if (!transceiver.iceGatherer) {
            transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                pc.usingBundle);
          }
    
          var localCapabilities = window.RTCRtpSender.getCapabilities(kind);
          // filter RTX until additional stuff needed for RTX is implemented
          // in adapter.js
          if (edgeVersion < 15019) {
            localCapabilities.codecs = localCapabilities.codecs.filter(
                function(codec) {
                  return codec.name !== 'rtx';
                });
          }
          localCapabilities.codecs.forEach(function(codec) {
            // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
            // by adding level-asymmetry-allowed=1
            if (codec.name === 'H264' &&
                codec.parameters['level-asymmetry-allowed'] === undefined) {
              codec.parameters['level-asymmetry-allowed'] = '1';
            }
    
            // for subsequent offers, we might have to re-use the payload
            // type of the last offer.
            if (transceiver.remoteCapabilities &&
                transceiver.remoteCapabilities.codecs) {
              transceiver.remoteCapabilities.codecs.forEach(function(remoteCodec) {
                if (codec.name.toLowerCase() === remoteCodec.name.toLowerCase() &&
                    codec.clockRate === remoteCodec.clockRate) {
                  codec.preferredPayloadType = remoteCodec.payloadType;
                }
              });
            }
          });
          localCapabilities.headerExtensions.forEach(function(hdrExt) {
            var remoteExtensions = transceiver.remoteCapabilities &&
                transceiver.remoteCapabilities.headerExtensions || [];
            remoteExtensions.forEach(function(rHdrExt) {
              if (hdrExt.uri === rHdrExt.uri) {
                hdrExt.id = rHdrExt.id;
              }
            });
          });
    
          // generate an ssrc now, to be used later in rtpSender.send
          var sendEncodingParameters = transceiver.sendEncodingParameters || [{
            ssrc: (2 * sdpMLineIndex + 1) * 1001
          }];
          if (track) {
            // add RTX
            if (edgeVersion >= 15019 && kind === 'video' &&
                !sendEncodingParameters[0].rtx) {
              sendEncodingParameters[0].rtx = {
                ssrc: sendEncodingParameters[0].ssrc + 1
              };
            }
          }
    
          if (transceiver.wantReceive) {
            transceiver.rtpReceiver = new window.RTCRtpReceiver(
                transceiver.dtlsTransport, kind);
          }
    
          transceiver.localCapabilities = localCapabilities;
          transceiver.sendEncodingParameters = sendEncodingParameters;
        });
    
        // always offer BUNDLE and dispose on return if not supported.
        if (pc._config.bundlePolicy !== 'max-compat') {
          sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
            return t.mid;
          }).join(' ') + '\r\n';
        }
        sdp += 'a=ice-options:trickle\r\n';
    
        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
          sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
              'offer', transceiver.stream, pc._dtlsRole);
          sdp += 'a=rtcp-rsize\r\n';
    
          if (transceiver.iceGatherer && pc.iceGatheringState !== 'new' &&
              (sdpMLineIndex === 0 || !pc.usingBundle)) {
            transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
              cand.component = 1;
              sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n';
            });
    
            if (transceiver.iceGatherer.state === 'completed') {
              sdp += 'a=end-of-candidates\r\n';
            }
          }
        });
    
        var desc = new window.RTCSessionDescription({
          type: 'offer',
          sdp: sdp
        });
        return Promise.resolve(desc);
      };