Method SetLocalDescription

peerconnection.go:1107–1163

SetLocalDescription sets the SessionDescription of the local peer nolint:cyclop

(desc SessionDescription)

//
//nolint:cyclop
func (pc *PeerConnection) SetLocalDescription(desc SessionDescription) error {
	if pc.isClosed.Load() {
		return &rtcerr.InvalidStateError{Err: ErrConnectionClosed}
	}

	haveLocalDescription := pc.currentLocalDescription != nil

	// JSEP 5.4
	if desc.SDP == "" {
		switch desc.Type {
		case SDPTypeAnswer, SDPTypePranswer:
			desc.SDP = pc.lastAnswer
		case SDPTypeOffer:
			desc.SDP = pc.lastOffer
		default:
			return &rtcerr.InvalidModificationError{
				Err: fmt.Errorf("%w: %s", errPeerConnSDPTypeInvalidValueSetLocalDescription, desc.Type),
			}
		}
	}

	desc.parsed = &sdp.SessionDescription{}
	if err := desc.parsed.UnmarshalString(desc.SDP); err != nil {
		return err
	}
	if err := pc.setDescription(&desc, stateChangeOpSetLocal); err != nil {
		return err
	}

	currentTransceivers := append([]*RTPTransceiver{}, pc.GetTransceivers()...)

	weAnswer := desc.Type == SDPTypeAnswer
	remoteDesc := pc.RemoteDescription()
	if weAnswer && remoteDesc != nil {
		_ = setRTPTransceiverCurrentDirection(&desc, currentTransceivers, false)
		if err := pc.startRTPSenders(currentTransceivers); err != nil {
			return err
		}
		pc.configureRTPReceivers(haveLocalDescription, remoteDesc, currentTransceivers)
		pc.ops.Enqueue(func() {
			pc.startRTP(haveLocalDescription, remoteDesc, currentTransceivers)
		})
	}

	mediaSection, ok := selectCandidateMediaSection(desc.parsed)
	if ok {
		pc.iceGatherer.setMediaStreamIdentification(mediaSection.SDPMid, mediaSection.SDPMLineIndex)
	}

	pc.iceGatherer.flushCandidates()

	if pc.iceGatherer.State() == ICEGathererStateNew {
		return pc.iceGatherer.Gather()
	}

	return nil
}