// +build !js

package main

import (
	"context"
	"fmt"
	"io"
	"os"
	"time"

	"github.com/pion/webrtc/v3"
	"github.com/pion/webrtc/v3/examples/internal/signal"
	"github.com/pion/webrtc/v3/pkg/media"
	"github.com/pion/webrtc/v3/pkg/media/ivfreader"
)

const cipherKey = 0xAA

func main() {
	peerConnection, err := webrtc.NewPeerConnection(webrtc.Configuration{
		ICEServers: []webrtc.ICEServer{
			{
				URLs: []string{"stun:stun.l.google.com:19302"},
			},
		},
	})
	if err != nil {
		panic(err)
	}

	// Create a video track
	videoTrack, err := webrtc.NewTrackLocalStaticSample(webrtc.RTPCodecCapability{MimeType: "video/vp8"}, "video", "pion")
	if err != nil {
		panic(err)
	}
	if _, err = peerConnection.AddTrack(videoTrack); err != nil {
		panic(err)
	}

	iceConnectedCtx, iceConnectedCtxCancel := context.WithCancel(context.Background())
	go func() {
		// Open a IVF file and start reading using our IVFReader
		file, ivfErr := os.Open("output.ivf")
		if ivfErr != nil {
			panic(ivfErr)
		}

		ivf, header, ivfErr := ivfreader.NewWith(file)
		if ivfErr != nil {
			panic(ivfErr)
		}

		// Wait for connection established
		<-iceConnectedCtx.Done()

		// Send our video file frame at a time. Pace our sending so we send it at the same speed it should be played back as.
		// This isn't required since the video is timestamped, but we will such much higher loss if we send all at once.
		sleepTime := time.Millisecond * time.Duration((float32(header.TimebaseNumerator)/float32(header.TimebaseDenominator))*1000)
		for {
			frame, _, ivfErr := ivf.ParseNextFrame()
			if ivfErr == io.EOF {
				fmt.Printf("All frames parsed and sent")
				os.Exit(0)
			}

			if ivfErr != nil {
				panic(ivfErr)
			}

			// Encrypt video using XOR Cipher
			for i := range frame {
				frame[i] ^= cipherKey
			}

			time.Sleep(sleepTime)
			if ivfErr = videoTrack.WriteSample(media.Sample{Data: frame, Duration: time.Second}); ivfErr != nil {
				panic(ivfErr)
			}
		}
	}()

	// 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())
		if connectionState == webrtc.ICEConnectionStateConnected {
			iceConnectedCtxCancel()
		}
	})

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

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

	// Create 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
	if err = peerConnection.SetLocalDescription(answer); 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 {}
}