RTCPeerConnection.prototype.setLocalDescription = function()

in release/connect-rtc.js [3642:3734]
75 lines of code
16 McCabe index (conditional complexity)

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

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

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

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

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

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

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

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

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

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

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

    return Promise.resolve();
  };