// +build js,wasm

package webrtc

import (
	"fmt"
	"time"
)

func signalPair(pcOffer *PeerConnection, pcAnswer *PeerConnection) (err error) {
	offerChan := make(chan SessionDescription)
	pcOffer.OnICECandidate(func(candidate *string) {
		if candidate == nil {
			offerChan <- *pcOffer.PendingLocalDescription()
		}
	})

	// Note(albrow): We need to create a data channel in order to trigger ICE
	// candidate gathering in the background.
	if _, err := pcOffer.CreateDataChannel("initial_data_channel", nil); err != nil {
		return err
	}

	offer, err := pcOffer.CreateOffer(nil)
	if err != nil {
		return err
	}
	if err := pcOffer.SetLocalDescription(offer); err != nil {
		return err
	}

	timeout := time.After(3 * time.Second)
	select {
	case <-timeout:
		return fmt.Errorf("timed out waiting to receive offer")
	case offer := <-offerChan:
		if err := pcAnswer.SetRemoteDescription(offer); err != nil {
			return err
		}

		answer, err := pcAnswer.CreateAnswer(nil)
		if err != nil {
			return err
		}

		if err = pcAnswer.SetLocalDescription(answer); err != nil {
			return err
		}

		err = pcOffer.SetRemoteDescription(answer)
		if err != nil {
			return err
		}
		return nil
	}
	return nil
}