//go:build !js
// +build !js

package main

import (
	"context"
	_ "embed"
	"encoding/json"
	"flag"
	"io"
	"log"
	"net"
	"net/http"
	"time"

	"github.com/flavioribeiro/donut/eia608"

	astisrt "github.com/asticode/go-astisrt/pkg"
	"github.com/asticode/go-astits"
	"github.com/pion/webrtc/v3"
	"github.com/pion/webrtc/v3/pkg/media"
)

var (
	//go:embed index.html
	indexHTML string

	api *webrtc.API //nolint

	enableICEMux = false
)

func srtToWebRTC(srtConnection *astisrt.Connection, videoTrack *webrtc.TrackLocalStaticSample, metadataTrack *webrtc.DataChannel) {
	r, w := io.Pipe()
	defer r.Close()
	defer w.Close()
	defer srtConnection.Close()

	go func() {
		defer srtConnection.Close()
		inboundMpegTsPacket := make([]byte, 1316) // SRT Read Size

		for {
			n, err := srtConnection.Read(inboundMpegTsPacket)
			if err != nil {
				break
			}

			if _, err := w.Write(inboundMpegTsPacket[:n]); err != nil {
				break
			}
		}
	}()

	dmx := astits.NewDemuxer(context.Background(), r)
	eia608Reader := eia608.NewEIA608Reader()
	h264PID := uint16(0)
	for {
		d, err := dmx.NextData()
		if err != nil {
			break
		}

		if d.PMT != nil {
			for _, es := range d.PMT.ElementaryStreams {
				if es.StreamType == astits.StreamTypeH264Video {
					h264PID = es.ElementaryPID
				}
			}
		}

		if d.PID == h264PID && d.PES != nil {
			if err = videoTrack.WriteSample(media.Sample{Data: d.PES.Data, Duration: time.Second / 30}); err != nil {
				break
			}
			captions, err := eia608Reader.Parse(d.PES)
			if err != nil {
				break
			}
			if captions != "" {
				metadataTrack.SendText(captions)
			}
		}
	}

}

func doSignaling(w http.ResponseWriter, r *http.Request) {
	setCors(w, r)
	if r.Method != http.MethodPost {
		return
	}

	peerConnectionConfiguration := webrtc.Configuration{}
	if !enableICEMux {
		peerConnectionConfiguration.ICEServers = []webrtc.ICEServer{
			{
				URLs: []string{
					"stun:stun4.l.google.com:19302",
				},
			},
		}
	}

	peerConnection, err := api.NewPeerConnection(peerConnectionConfiguration)
	if err != nil {
		errorToHTTP(w, err)
		return
	}

	offer := struct {
		SRTHost     string
		SRTPort     string
		SRTStreamID string
		Offer       webrtc.SessionDescription
	}{"", "", "", webrtc.SessionDescription{}}

	if err = json.NewDecoder(r.Body).Decode(&offer); err != nil {
		errorToHTTP(w, err)
		return
	}

	// Create a video track
	videoTrack, err := webrtc.NewTrackLocalStaticSample(webrtc.RTPCodecCapability{MimeType: webrtc.MimeTypeH264}, "video", offer.SRTStreamID)
	if err != nil {
		errorToHTTP(w, err)
		return
	}
	if _, err := peerConnection.AddTrack(videoTrack); err != nil {
		errorToHTTP(w, err)
		return
	}

	// Create data channel for metadata transmission
	metadataSender, err := peerConnection.CreateDataChannel("metadata", nil)
	if err != nil {
		errorToHTTP(w, err)
	}

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

	srtPort, err := assertSignalingCorrect(offer.SRTHost, offer.SRTPort, offer.SRTStreamID)
	if err != nil {
		errorToHTTP(w, err)
		return
	}

	if err = peerConnection.SetRemoteDescription(offer.Offer); err != nil {
		errorToHTTP(w, err)
		return
	}

	log.Println("Gathering WebRTC Candidates")
	gatherComplete := webrtc.GatheringCompletePromise(peerConnection)
	answer, err := peerConnection.CreateAnswer(nil)
	if err != nil {
		errorToHTTP(w, err)
		return
	} else if err = peerConnection.SetLocalDescription(answer); err != nil {
		errorToHTTP(w, err)
		return
	}
	<-gatherComplete
	log.Println("Gathering WebRTC Candidates Complete")

	response, err := json.Marshal(*peerConnection.LocalDescription())
	if err != nil {
		return
	}

	log.Println("Connecting to SRT")
	srtConnection, err := astisrt.Dial(astisrt.DialOptions{
		ConnectionOptions: []astisrt.ConnectionOption{
			astisrt.WithLatency(300),
			astisrt.WithStreamid(offer.SRTStreamID),
		},

		// Callback when the connection is disconnected
		OnDisconnect: func(c *astisrt.Connection, err error) { log.Fatal("Disconnected from SRT") },

		Host: offer.SRTHost,
		Port: uint16(srtPort),
	})
	if err != nil {
		errorToHTTP(w, err)
		return
	}
	log.Println("Connected to SRT")

	go srtToWebRTC(srtConnection, videoTrack, metadataSender)

	w.Header().Set("Content-Type", "application/json")
	if _, err := w.Write(response); err != nil {
		errorToHTTP(w, err)
		return
	}
}

func main() {
	flag.BoolVar(&enableICEMux, "enable-ice-mux", false, "Enable ICE Mux on :8081")
	flag.Parse()

	mediaEngine := &webrtc.MediaEngine{}
	settingEngine := webrtc.SettingEngine{}
	if err := mediaEngine.RegisterDefaultCodecs(); err != nil {
		log.Fatal(err)
	}

	if enableICEMux {
		tcpListener, err := net.ListenTCP("tcp", &net.TCPAddr{
			IP:   net.IP{0, 0, 0, 0},
			Port: 8081,
		})
		if err != nil {
			log.Fatal(err)
		}

		udpListener, err := net.ListenUDP("udp", &net.UDPAddr{
			IP:   net.IP{0, 0, 0, 0},
			Port: 8081,
		})
		if err != nil {
			log.Fatal(err)
		}

		settingEngine.SetNAT1To1IPs([]string{"127.0.0.1"}, webrtc.ICECandidateTypeHost)
		settingEngine.SetICETCPMux(webrtc.NewICETCPMux(nil, tcpListener, 8))
		settingEngine.SetICEUDPMux(webrtc.NewICEUDPMux(nil, udpListener))
	}
	api = webrtc.NewAPI(webrtc.WithSettingEngine(settingEngine), webrtc.WithMediaEngine(mediaEngine))

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(200)
		w.Write([]byte(indexHTML))
	})
	http.HandleFunc("/doSignaling", doSignaling)

	log.Println("Open http://localhost:8080 to access this demo")
	log.Fatal(http.ListenAndServe(":8080", nil))
}