package main

import (
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
	"sync"

	"database/sql"

	"github.com/joho/godotenv"
	"github.com/pion/interceptor"
	"github.com/pion/webrtc/v3"

	_ "github.com/mattn/go-sqlite3"
)

type WebRTCStream struct {
	audioTrack, videoTrack *webrtc.TrackLocalStaticRTP
}

var (
	runningStreams     map[string]WebRTCStream
	runningStreamsLock sync.Mutex
	api                *webrtc.API
	db                 *sql.DB
)

func main() {
	if err := godotenv.Load(".env"); err != nil {
		log.Fatal(err)
	}

	db = setupDatabase()
	defer db.Close()

	api = setupWebRTC()
	runningStreams = map[string]WebRTCStream{}

	mux := http.NewServeMux()
	mux.HandleFunc("/api/wish-server/whip", withCors(HandleWHIP))
	mux.HandleFunc("/api/wish-server/whep", withCors(HandleWHEP))

	log.Fatal((&http.Server{
		Handler: mux,
		Addr:    os.Getenv("HTTP_ADDRESS"),
	}).ListenAndServe())
}

func setupDatabase() *sql.DB {
	db, err := sql.Open("sqlite3", os.Getenv("DATABASE_URL"))
	if err != nil {
		log.Fatal(err)
	}

	return db
}

func setupWebRTC() *webrtc.API {
	mediaEngine := &webrtc.MediaEngine{}
	if err := mediaEngine.RegisterDefaultCodecs(); err != nil {
		log.Fatal(err)
	}

	interceptorRegistry := &interceptor.Registry{}
	if err := webrtc.RegisterDefaultInterceptors(mediaEngine, interceptorRegistry); err != nil {
		log.Fatal(err)
	}

	settingEngine := webrtc.SettingEngine{}

	return webrtc.NewAPI(
		webrtc.WithMediaEngine(mediaEngine),
		webrtc.WithInterceptorRegistry(interceptorRegistry),
		webrtc.WithSettingEngine(settingEngine),
	)
}

func withCors(next func(w http.ResponseWriter, r *http.Request)) http.HandlerFunc {
	return func(res http.ResponseWriter, req *http.Request) {
		res.Header().Set("Access-Control-Allow-Origin", "*")
		res.Header().Set("Access-Control-Allow-Methods", "*")
		res.Header().Set("Access-Control-Allow-Headers", "*")

		if req.Method != http.MethodOptions {
			next(res, req)
		}
	}
}

func logHTTPError(w http.ResponseWriter, err string, code int) {
	log.Println(err)
	http.Error(w, err, code)
}

func getTracksForStream(streamName string) (
	*webrtc.TrackLocalStaticRTP,
	*webrtc.TrackLocalStaticRTP,
	error,
) {
	runningStreamsLock.Lock()
	defer runningStreamsLock.Unlock()

	foundStream, ok := runningStreams[streamName]
	if !ok {
		videoTrack, err := webrtc.NewTrackLocalStaticRTP(webrtc.RTPCodecCapability{MimeType: webrtc.MimeTypeH264}, "video", "pion")
		if err != nil {
			return nil, nil, err
		}

		audioTrack, err := webrtc.NewTrackLocalStaticRTP(webrtc.RTPCodecCapability{MimeType: webrtc.MimeTypeOpus}, "audio", "pion")
		if err != nil {
			return nil, nil, err
		}

		foundStream = WebRTCStream{
			audioTrack: audioTrack,
			videoTrack: videoTrack,
		}
		runningStreams[streamName] = foundStream
	}

	return foundStream.audioTrack, foundStream.videoTrack, nil
}

func HandleWHIP(res http.ResponseWriter, req *http.Request) {
	authorization := req.Header.Get("Authorization")
	if authorization == "" {
		logHTTPError(res, "Authorization was not set", http.StatusBadRequest)
		return
	}

	streamName, streamPassword, _ := strings.Cut(authorization, ":")
	if err := db.QueryRow("SELECT * FROM streams WHERE stream = ? AND password = ?", streamName, streamPassword).Scan(); err != nil {
		logHTTPError(res, "Invalid stream authorization", http.StatusUnauthorized)
		return
	}

	offer, err := io.ReadAll(req.Body)
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	peerConnection, err := api.NewPeerConnection(webrtc.Configuration{})
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	audioTrack, videoTrack, err := getTracksForStream(streamName)
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	peerConnection.OnTrack(func(track *webrtc.TrackRemote, _recv *webrtc.RTPReceiver) {
		var localTrack *webrtc.TrackLocalStaticRTP
		if strings.HasPrefix(track.Codec().RTPCodecCapability.MimeType, "audio/") {
			localTrack = audioTrack
		} else {
			localTrack = videoTrack
		}

		rtpBuf := make([]byte, 1500)
		for {
			rtpRead, _, readErr := track.Read(rtpBuf)
			switch {
			case errors.Is(readErr, io.EOF):
				return
			case readErr != nil:
				log.Println(readErr)
				return
			}

			if _, writeErr := localTrack.Write(rtpBuf[:rtpRead]); writeErr != nil && !errors.Is(writeErr, io.ErrClosedPipe) {
				log.Println(writeErr)
				return
			}
		}
	})

	peerConnection.OnICEConnectionStateChange(func(state webrtc.ICEConnectionState) {
		if state == webrtc.ICEConnectionStateFailed {
			if err := peerConnection.Close(); err != nil {
				log.Println(err)
				return
			}
		}
	})

	if err := peerConnection.SetRemoteDescription(webrtc.SessionDescription{
		SDP:  string(offer),
		Type: webrtc.SDPTypeOffer,
	}); err != nil {
		logHTTPError(res, err.Error(), http.StatusBadRequest)
		return
	}

	gatheringComplete := webrtc.GatheringCompletePromise(peerConnection)

	answer, err := peerConnection.CreateAnswer(nil)
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	} else if err = peerConnection.SetLocalDescription(answer); err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	<-gatheringComplete

	fmt.Fprint(res, peerConnection.LocalDescription().SDP)
}

func HandleWHEP(res http.ResponseWriter, req *http.Request) {
	streamName := req.Header.Get("Authorization")
	if streamName == "" {
		logHTTPError(res, "Stream name was not set", http.StatusBadRequest)
		return
	}

	offer, err := io.ReadAll(req.Body)
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	peerConnection, err := api.NewPeerConnection(webrtc.Configuration{})
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	audioTrack, videoTrack, err := getTracksForStream(streamName)
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	if _, err = peerConnection.AddTrack(audioTrack); err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	if _, err = peerConnection.AddTrack(videoTrack); err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	if err := peerConnection.SetRemoteDescription(webrtc.SessionDescription{
		SDP:  string(offer),
		Type: webrtc.SDPTypeOffer,
	}); err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	gatheringComplete := webrtc.GatheringCompletePromise(peerConnection)

	answer, err := peerConnection.CreateAnswer(nil)
	if err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	} else if err = peerConnection.SetLocalDescription(answer); err != nil {
		logHTTPError(res, err.Error(), http.StatusInternalServerError)
		return
	}

	<-gatheringComplete

	fmt.Fprint(res, peerConnection.LocalDescription().SDP)
}