package main

import (
	"fmt"

	"github.com/pion/mediadevices"
	"github.com/pion/mediadevices/examples/internal/signal"
	"github.com/pion/mediadevices/pkg/frame"
	"github.com/pion/mediadevices/pkg/prop"
	"github.com/pion/webrtc/v4"

	// If you don't like x264, you can also use vpx by importing as below
	// "github.com/pion/mediadevices/pkg/codec/vpx" // This is required to use VP8/VP9 video encoder
	// or you can also use openh264 for alternative h264 implementation
	// "github.com/pion/mediadevices/pkg/codec/openh264"
	// or if you use a raspberry pi like, you can use mmal for using its hardware encoder
	// "github.com/pion/mediadevices/pkg/codec/mmal"
	"github.com/pion/mediadevices/pkg/codec/opus" // This is required to use opus audio encoder
	"github.com/pion/mediadevices/pkg/codec/x264" // This is required to use h264 video encoder

	// Note: If you don't have a camera or microphone or your adapters are not supported,
	//       you can always swap your adapters with our dummy adapters below.
	// _ "github.com/pion/mediadevices/pkg/driver/videotest"
	// _ "github.com/pion/mediadevices/pkg/driver/audiotest"
	_ "github.com/pion/mediadevices/pkg/driver/camera"     // This is required to register camera adapter
	_ "github.com/pion/mediadevices/pkg/driver/microphone" // This is required to register microphone adapter
)

func main() {
	config := webrtc.Configuration{
		ICEServers: []webrtc.ICEServer{
			{
				URLs: []string{"stun:stun.l.google.com:19302"},
			},
		},
	}

	// Wait for the offer to be pasted
	offer := webrtc.SessionDescription{}
	signal.Decode(signal.MustReadStdin(), &offer)

	// Create a new RTCPeerConnection
	x264Params, err := x264.NewParams()
	if err != nil {
		panic(err)
	}
	x264Params.BitRate = 500_000 // 500kbps

	opusParams, err := opus.NewParams()
	if err != nil {
		panic(err)
	}
	codecSelector := mediadevices.NewCodecSelector(
		mediadevices.WithVideoEncoders(&x264Params),
		mediadevices.WithAudioEncoders(&opusParams),
	)

	mediaEngine := webrtc.MediaEngine{}
	codecSelector.Populate(&mediaEngine)
	api := webrtc.NewAPI(webrtc.WithMediaEngine(&mediaEngine))
	peerConnection, err := api.NewPeerConnection(config)
	if err != nil {
		panic(err)
	}

	// Set the handler for ICE connection state
	// This will notify you when the peer has connected/disconnected
	peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
		fmt.Printf("Connection State has changed %s \n", connectionState.String())
	})

	s, err := mediadevices.GetUserMedia(mediadevices.MediaStreamConstraints{
		Video: func(c *mediadevices.MediaTrackConstraints) {
			c.FrameFormat = prop.FrameFormat(frame.FormatI420)
			c.Width = prop.Int(640)
			c.Height = prop.Int(480)
		},
		Audio: func(c *mediadevices.MediaTrackConstraints) {
		},
		Codec: codecSelector,
	})
	if err != nil {
		panic(err)
	}

	for _, track := range s.GetTracks() {
		track.OnEnded(func(err error) {
			fmt.Printf("Track (ID: %s) ended with error: %v\n",
				track.ID(), err)
		})

		_, err = peerConnection.AddTransceiverFromTrack(track,
			webrtc.RTPTransceiverInit{
				Direction: webrtc.RTPTransceiverDirectionSendonly,
			},
		)
		if err != nil {
			panic(err)
		}
	}

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

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

	// Create channel that is blocked until ICE Gathering is complete
	gatherComplete := webrtc.GatheringCompletePromise(peerConnection)

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

	// Block until ICE Gathering is complete, disabling trickle ICE
	// we do this because we only can exchange one signaling message
	// in a production application you should exchange ICE Candidates via OnICECandidate
	<-gatherComplete

	// Output the answer in base64 so we can paste it in browser
	fmt.Println(signal.Encode(*peerConnection.LocalDescription()))

	// Block forever
	select {}
}