package main

import (
	"fmt"
	"time"

	"github.com/pions/rtcp"
	"github.com/pions/webrtc"

	"github.com/pions/webrtc/examples/internal/signal"
)

var peerConnectionConfig = webrtc.Configuration{
	ICEServers: []webrtc.ICEServer{
		{
			URLs: []string{"stun:stun.l.google.com:19302"},
		},
	},
}

const (
	rtcpPLIInterval = time.Second * 3
)

func main() {
	sdpChan := signal.HTTPSDPServer()

	// Everything below is the pion-WebRTC API, thanks for using it ❤️.
	// Create a MediaEngine object to configure the supported codec
	m := webrtc.MediaEngine{}

	// Setup the codecs you want to use.
	// Only support VP8, this makes our proxying code simpler
	m.RegisterCodec(webrtc.NewRTPVP8Codec(webrtc.DefaultPayloadTypeVP8, 90000))

	// Create the API object with the MediaEngine
	api := webrtc.NewAPI(webrtc.WithMediaEngine(m))

	offer := webrtc.SessionDescription{}
	signal.Decode(<-sdpChan, &offer)
	fmt.Println("")

	// Create a new RTCPeerConnection
	peerConnection, err := api.NewPeerConnection(peerConnectionConfig)
	if err != nil {
		panic(err)
	}

	localTrackChan := make(chan *webrtc.Track)
	// Set a handler for when a new remote track starts, this just distributes all our packets
	// to connected peers
	peerConnection.OnTrack(func(remoteTrack *webrtc.Track, receiver *webrtc.RTPReceiver) {
		// Send a PLI on an interval so that the publisher is pushing a keyframe every rtcpPLIInterval
		// This can be less wasteful by processing incoming RTCP events, then we would emit a NACK/PLI when a viewer requests it
		go func() {
			ticker := time.NewTicker(rtcpPLIInterval)
			for range ticker.C {
				if err := peerConnection.SendRTCP(&rtcp.PictureLossIndication{MediaSSRC: remoteTrack.SSRC()}); err != nil {
					fmt.Println(err)
				}
			}
		}()

		// Create a local track, all our SFU clients will be fed via this track
		localTrack, err := peerConnection.NewTrack(remoteTrack.PayloadType(), remoteTrack.SSRC(), "video", "pion")
		if err != nil {
			panic(err)
		}
		localTrackChan <- localTrack

		rtpBuf := make([]byte, 1400)
		for {
			i, err := remoteTrack.Read(rtpBuf)
			if err != nil {
				panic(err)
			}

			if _, err = localTrack.Write(rtpBuf[:i]); err != nil {
				panic(err)
			}
		}
	})

	// Set the remote SessionDescription
	err = peerConnection.SetRemoteDescription(offer)
	if err != nil {
		panic(err)
	}

	// Create answer
	answer, err := peerConnection.CreateAnswer(nil)
	if err != nil {
		panic(err)
	}

	// Sets the LocalDescription, and starts our UDP listeners
	err = peerConnection.SetLocalDescription(answer)
	if err != nil {
		panic(err)
	}

	// Get the LocalDescription and take it to base64 so we can paste in browser
	fmt.Println(signal.Encode(answer))

	localTrack := <-localTrackChan
	for {
		fmt.Println("")
		fmt.Println("Curl an base64 SDP to start sendonly peer connection")

		recvOnlyOffer := webrtc.SessionDescription{}
		signal.Decode(<-sdpChan, &recvOnlyOffer)

		// Create a new PeerConnection
		peerConnection, err := api.NewPeerConnection(peerConnectionConfig)
		if err != nil {
			panic(err)
		}

		_, err = peerConnection.AddTrack(localTrack)
		if err != nil {
			panic(err)
		}

		// Set the remote SessionDescription
		err = peerConnection.SetRemoteDescription(recvOnlyOffer)
		if err != nil {
			panic(err)
		}

		// Create answer
		answer, err := peerConnection.CreateAnswer(nil)
		if err != nil {
			panic(err)
		}

		// Sets the LocalDescription, and starts our UDP listeners
		err = peerConnection.SetLocalDescription(answer)
		if err != nil {
			panic(err)
		}

		// Get the LocalDescription and take it to base64 so we can paste in browser
		fmt.Println(signal.Encode(answer))
	}
}