package telemost

import (
	"fmt"
	"sync"

	"github.com/pion/rtp"
	"github.com/pion/rtp/codecs"
	"github.com/pion/webrtc/v4"
	"github.com/sagernet/sing-box/transport/call/common"
	"github.com/sagernet/sing-box/transport/call/tunnel"
	"github.com/sagernet/sing/common/logger"
)

type SFURelay struct {
	pubPC        *webrtc.PeerConnection
	subPC        *webrtc.PeerConnection
	pubRemoteSet bool
	subRemoteSet bool
	pubPending   []webrtc.ICECandidateInit
	subPending   []webrtc.ICECandidateInit
	mu           sync.Mutex
	logger       logger.ContextLogger

	sampleTrack   *webrtc.TrackLocalStaticSample
	tun           *tunnel.VP8DataTunnel
	obf           *tunnel.TunnelObfuscator
	OnConnected   func(*tunnel.VP8DataTunnel)
	OnPubReady    func()
	OnPeerRestart func()
	OnPubICE      func(*webrtc.ICECandidate)
	OnSubICE      func(*webrtc.ICECandidate)

	readBufSize int
}

func (r *SFURelay) SetObfuscator(o *tunnel.TunnelObfuscator) { r.obf = o }

func NewSFURelay(logger logger.ContextLogger) *SFURelay {
	return &SFURelay{logger: logger}
}

func (r *SFURelay) Init(iceServers []webrtc.ICEServer) error {
	config := webrtc.Configuration{ICEServers: iceServers}
	pubPC, err := NewPeerConnection(config)
	if err != nil {
		return err
	}
	r.pubPC = pubPC
	sampleTrack, _ := webrtc.NewTrackLocalStaticSample(
		webrtc.RTPCodecCapability{MimeType: webrtc.MimeTypeVP8},
		"video", "tunnel-video",
	)
	r.sampleTrack = sampleTrack
	audioTrack, _ := webrtc.NewTrackLocalStaticRTP(
		webrtc.RTPCodecCapability{MimeType: webrtc.MimeTypeOpus},
		"audio", "tunnel-audio",
	)
	pubPC.AddTransceiverFromTrack(audioTrack, webrtc.RTPTransceiverInit{Direction: webrtc.RTPTransceiverDirectionSendonly})
	pubPC.AddTransceiverFromTrack(r.sampleTrack, webrtc.RTPTransceiverInit{Direction: webrtc.RTPTransceiverDirectionSendonly})
	pubPC.OnICECandidate(func(cand *webrtc.ICECandidate) {
		if cand == nil || r.OnPubICE == nil {
			return
		}
		r.OnPubICE(cand)
	})
	pubPC.OnConnectionStateChange(func(state webrtc.PeerConnectionState) {
		r.logger.Debug(fmt.Sprintf("[pub] connection state: %s", state.String()))
		if state == webrtc.PeerConnectionStateConnected {
			if r.tun == nil {
				r.logger.Debug("[relay] starting VP8 publish tunnel on pub PC connected")
				r.tun = tunnel.NewVP8DataTunnel(r.sampleTrack, r.obf, r.logger)
				r.tun.Start(0, 0)
				if r.OnConnected != nil {
					r.OnConnected(r.tun)
				}
			}
			if r.OnPubReady != nil {
				r.OnPubReady()
			}
		}
	})
	subPC, err := NewPeerConnection(config)
	if err != nil {
		pubPC.Close()
		return err
	}
	r.subPC = subPC
	subPC.OnICECandidate(func(cand *webrtc.ICECandidate) {
		if cand == nil || r.OnSubICE == nil {
			return
		}
		r.OnSubICE(cand)
	})
	subPC.OnConnectionStateChange(func(state webrtc.PeerConnectionState) {
		r.logger.Debug(fmt.Sprintf("[sub] connection state: %s", state.String()))
	})
	subPC.OnTrack(func(track *webrtc.TrackRemote, receiver *webrtc.RTPReceiver) {
		r.logger.Debug(fmt.Sprintf("[sub] remote track: %s", track.Codec().MimeType))
		go r.readTrack(track)
	})
	r.logger.Debug(fmt.Sprintf("[relay] pub+sub PCs created (%d ICE servers)", len(iceServers)))
	return nil
}

func (r *SFURelay) CreatePubOffer() (webrtc.SessionDescription, error) {
	offer, err := r.pubPC.CreateOffer(nil)
	if err != nil {
		return offer, err
	}
	if err := r.pubPC.SetLocalDescription(offer); err != nil {
		return offer, err
	}
	offer.SDP = MungeSDPAddVideoContent(offer.SDP)
	return offer, nil
}

func (r *SFURelay) SetPubAnswer(sdp string) error {
	r.mu.Lock()
	defer r.mu.Unlock()
	err := r.pubPC.SetRemoteDescription(webrtc.SessionDescription{
		Type: webrtc.SDPTypeAnswer, SDP: sdp,
	})
	if err != nil {
		return err
	}
	r.pubRemoteSet = true
	for _, cand := range r.pubPending {
		r.pubPC.AddICECandidate(cand)
	}
	r.pubPending = nil
	return nil
}

func (r *SFURelay) SetSubOffer(sdp string) (webrtc.SessionDescription, error) {
	r.mu.Lock()
	defer r.mu.Unlock()
	err := r.subPC.SetRemoteDescription(webrtc.SessionDescription{
		Type: webrtc.SDPTypeOffer, SDP: sdp,
	})
	if err != nil {
		return webrtc.SessionDescription{}, err
	}
	r.subRemoteSet = true
	for _, cand := range r.subPending {
		r.subPC.AddICECandidate(cand)
	}
	r.subPending = nil
	answer, err := r.subPC.CreateAnswer(nil)
	if err != nil {
		return answer, err
	}
	r.subPC.SetLocalDescription(answer)
	return answer, nil
}

func (r *SFURelay) AddPubICECandidate(cand webrtc.ICECandidateInit) {
	r.mu.Lock()
	defer r.mu.Unlock()
	if !r.pubRemoteSet {
		r.pubPending = append(r.pubPending, cand)
		return
	}
	r.pubPC.AddICECandidate(cand)
}

func (r *SFURelay) AddSubICECandidate(cand webrtc.ICECandidateInit) {
	r.mu.Lock()
	defer r.mu.Unlock()
	if !r.subRemoteSet {
		r.subPending = append(r.subPending, cand)
		return
	}
	r.subPC.AddICECandidate(cand)
}

func (r *SFURelay) Close() {
	if r.tun != nil {
		r.tun.Stop()
		r.tun = nil
	}
	if r.pubPC != nil {
		r.pubPC.Close()
		r.pubPC = nil
	}
	if r.subPC != nil {
		r.subPC.Close()
		r.subPC = nil
	}
}

func (r *SFURelay) readTrack(track *webrtc.TrackRemote) {
	if track.Codec().MimeType != webrtc.MimeTypeVP8 {
		buf := make([]byte, common.UDPBufSize)
		for {
			if _, _, err := track.Read(buf); err != nil {
				return
			}
		}
	}
	var vp8Pkt codecs.VP8Packet
	var pkt rtp.Packet
	var frameBuf []byte
	var lastSeq uint16
	var haveLastSeq bool
	frameValid := false
	var recvCount int
	bufSz := r.readBufSize
	if bufSz <= 0 {
		bufSz = common.RTPBufSize
	}
	buf := make([]byte, bufSz)
	for {
		n, _, err := track.Read(buf)
		if err != nil {
			return
		}
		if pkt.Unmarshal(buf[:n]) != nil {
			continue
		}
		if haveLastSeq && pkt.SequenceNumber != lastSeq+1 {
			frameValid = false
			frameBuf = frameBuf[:0]
		}
		lastSeq = pkt.SequenceNumber
		haveLastSeq = true
		vp8Payload, err := vp8Pkt.Unmarshal(pkt.Payload)
		if err != nil {
			frameValid = false
			frameBuf = frameBuf[:0]
			continue
		}
		if vp8Pkt.S == 1 {
			frameBuf = frameBuf[:0]
			frameValid = true
		}
		if !frameValid {
			continue
		}
		frameBuf = append(frameBuf, vp8Payload...)
		if !pkt.Marker {
			continue
		}
		recvCount++
		if recvCount <= 3 || recvCount%200 == 0 {
			r.logger.Debug(fmt.Sprintf("[video] recv vp8 frame #%d %d bytes", recvCount, len(frameBuf)))
		}
		res := r.obf.Decode(frameBuf)
		frameBuf = frameBuf[:0]
		frameValid = false
		if !res.HasFrame || res.SelfEcho {
			continue
		}
		if res.PeerRestart {
			r.logger.Info(fmt.Sprintf("[video] peer restart detected, new epoch=0x%08x", res.PeerEpoch))
			if r.OnPeerRestart != nil {
				r.OnPeerRestart()
			}
		}
		if res.Keepalive || len(res.Payload) == 0 {
			continue
		}
		if r.tun != nil && r.tun.OnData != nil {
			r.tun.OnData(res.Payload)
		}
	}
}