// xmpp side of signaling.Bridge; one Adapter per session,
// sharing a *jingle.Manager for stanza dispatch
package xmppsig

import (
	"fmt"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"

	"dev.narayana.im/narayana/telegabber/calls/signaling"
	"dev.narayana.im/narayana/telegabber/xmpp/jingle"

	"github.com/pion/webrtc/v4"
	log "github.com/sirupsen/logrus"
)

type AdapterConfig struct {
	Sender   jingle.Sender // *xmpp.Component satisfies this
	LocalJID string        // gateway's bare JID
	Manager  *jingle.Manager
	// fresh PC per call, with the transceivers/tracks SDP negotiation needs
	PCFactory func() (*webrtc.PeerConnection, error)
}

type Adapter struct {
	cfg AdapterConfig
}

func NewAdapter(cfg AdapterConfig) *Adapter { return &Adapter{cfg: cfg} }
func (a *Adapter) Manager() *jingle.Manager { return a.cfg.Manager }
func (a *Adapter) LocalJID() string         { return a.cfg.LocalJID }

// xmpp side for a TG-originated call; PC and session built upfront so a
// failure unwinds both. Bind must run before bridge.Start.
func (a *Adapter) NewCaller(remoteJID string, callerUserID int64) (*Caller, error) {
	pc, err := a.cfg.PCFactory()
	if err != nil {
		return nil, fmt.Errorf("PCFactory: %w", err)
	}
	// XEP-0353 requires a full JID; /telegabber matches the gateway's other
	// per-contact outbound stanzas
	localJID := fmt.Sprintf("%d@%s/telegabber", callerUserID, a.cfg.LocalJID)
	c := &Caller{xmppBase: xmppBase{
		a: a, remote: remoteJID, pc: pc, localJID: localJID,
		side: signaling.CallerSide,
	}}
	// must install OnTrack forwarder before SetRemoteDescription, otherwise
	// pion fires OnTrack during SDP processing and a late handler misses it
	c.hookTrack(pc)

	sid := newSID()
	sess, err := jingle.New(jingle.SessionOpts{
		PC: pc, Sender: a.cfg.Sender,
		LocalJID: localJID, RemoteJID: remoteJID,
		SID: sid, Role: jingle.RoleInitiator, Media: []string{"audio"},
		Observer: c,
	})
	if err != nil {
		_ = pc.Close()
		return nil, fmt.Errorf("jingle.New: %w", err)
	}
	c.set(sid, sess)
	return c, nil
}

// xmpp side for an XMPP-originated call; Bind must run before bridge.Start
func (a *Adapter) NewCallee(p jingle.IncomingProposal) (*Callee, *jingle.Session, error) {
	pc, err := a.cfg.PCFactory()
	if err != nil {
		return nil, nil, fmt.Errorf("PCFactory: %w", err)
	}

	c := &Callee{xmppBase: xmppBase{a: a, remote: p.From, pc: pc, side: signaling.CalleeSide}}
	c.hookTrack(pc)
	// LocalJID is the propose's `to`, not the bare component domain;
	// anotherim's libdino filters proceed with from.equals_bare(peer_state.jid)
	// so a proceed from the bare component domain silently fails to match
	// and anotherim never sends session-initiate
	localJID := p.To
	if localJID == "" {
		localJID = a.cfg.LocalJID
	}
	// Conversations' RtpSessionActivity crashes on bare-JID `with` once ICE
	// completes (IllegalStateException "No RTP connection found"); real
	// callees always send <proceed> from a full JID. Stick the SID on as
	// resource so concurrent calls don't collide.
	if !strings.ContainsRune(localJID, '/') && p.SID != "" {
		localJID = localJID + "/" + p.SID
	}
	sess, err := jingle.New(jingle.SessionOpts{
		PC: pc, Sender: a.cfg.Sender,
		LocalJID: localJID, RemoteJID: p.From,
		SID: p.SID, Role: jingle.RoleResponder, Media: p.Media,
		Observer: c,
	})
	if err != nil {
		_ = pc.Close()
		return nil, nil, err
	}
	c.set(p.SID, sess)
	return c, sess, nil
}

// wires pion's connection-state callback to bridge media transitions.
// Disconnected can be transient (ICE restart) so only Failed reacts.
// side dedups MediaConnected per source. Called from xmppBase.Bind.
func hookPCState(pc *webrtc.PeerConnection, br *signaling.Bridge, side signaling.Side) {
	if pc == nil || br == nil {
		return
	}
	// DTLS logger lazily on first state change - the transceiver's
	// DTLSTransport doesn't exist until SetLocalDescription runs
	var dtlsHookOnce sync.Once
	pc.OnConnectionStateChange(func(s webrtc.PeerConnectionState) {
		dtlsHookOnce.Do(func() { hookDTLSState(pc) })
		entry := log.WithField("state", s.String())
		// log the selected ICE pair on Connected - flaky calls have happened
		// when pion picked a docker-bridge or Tailscale pair whose STUN pings
		// succeed but real RTP doesn't transit. SCTP isn't negotiated for
		// audio-only, so reach the ICE transport via any RTP sender's
		// DTLSTransport (BUNDLE means they all share one).
		if s == webrtc.PeerConnectionStateConnected {
			var dtls *webrtc.DTLSTransport
			for _, snd := range pc.GetSenders() {
				if snd != nil && snd.Transport() != nil {
					dtls = snd.Transport()
					break
				}
			}
			if dtls == nil {
				for _, r := range pc.GetReceivers() {
					if r != nil && r.Transport() != nil {
						dtls = r.Transport()
						break
					}
				}
			}
			switch {
			case dtls == nil:
				entry = entry.WithField("ice_pair", "no-dtls-transport")
			case dtls.ICETransport() == nil:
				entry = entry.WithField("ice_pair", "no-ice-transport")
			default:
				pair, err := dtls.ICETransport().GetSelectedCandidatePair()
				switch {
				case err != nil:
					entry = entry.WithError(err).WithField("ice_pair", "get-selected-failed")
				case pair == nil || pair.Local == nil || pair.Remote == nil:
					entry = entry.WithField("ice_pair", "nil")
				default:
					entry = entry.WithFields(log.Fields{
						"local":         fmt.Sprintf("%s:%d (%s)", pair.Local.Address, pair.Local.Port, pair.Local.Typ.String()),
						"remote":        fmt.Sprintf("%s:%d (%s)", pair.Remote.Address, pair.Remote.Port, pair.Remote.Typ.String()),
						"local_related": pair.Local.RelatedAddress,
					})
				}
			}
		}
		entry.Debug("pion: PC connection state")
		switch s {
		case webrtc.PeerConnectionStateConnected:
			br.MediaConnected(side)
		case webrtc.PeerConnectionStateFailed:
			br.MediaFailed(signaling.ReasonMediaFailed)
		}
	})
	pc.OnICEConnectionStateChange(func(s webrtc.ICEConnectionState) {
		log.WithField("state", s.String()).Debug("pion: ICE connection state")
	})
	pc.OnICEGatheringStateChange(func(s webrtc.ICEGatheringState) {
		log.WithField("state", s.String()).Debug("pion: ICE gathering state")
	})
	// do NOT register pc.OnICECandidate here - jingle.New attaches the
	// session's trickle handler there, pion's API is replace-only, and
	// overwriting it strands srflx/relay candidates -> breaks TURN-only paths
}

// logs DTLS state - separates "handshake never completed" from "completed
// but no audio" (SRTP/SSRC/codec). Called from the first state change so
// the transport actually exists.
func hookDTLSState(pc *webrtc.PeerConnection) {
	var dtls *webrtc.DTLSTransport
	for _, s := range pc.GetSenders() {
		if s != nil && s.Transport() != nil {
			dtls = s.Transport()
			break
		}
	}
	if dtls == nil {
		for _, r := range pc.GetReceivers() {
			if r != nil && r.Transport() != nil {
				dtls = r.Transport()
				break
			}
		}
	}
	if dtls == nil {
		log.Debug("pion: no DTLSTransport available at hook time; DTLS state changes will go unlogged")
		return
	}
	dtls.OnStateChange(func(s webrtc.DTLSTransportState) {
		log.WithField("state", s.String()).Info("pion: DTLS transport state")
	})
}

func mapReason(r signaling.TerminationReason) string {
	switch r {
	case signaling.ReasonHangup:
		return jingle.ReasonSuccess
	case signaling.ReasonDecline:
		return jingle.ReasonDecline
	case signaling.ReasonBusy:
		return jingle.ReasonBusy
	case signaling.ReasonRingTimeout:
		return jingle.ReasonTimeout
	case signaling.ReasonExchangeTimeout, signaling.ReasonConnectTimeout:
		return jingle.ReasonConnectivityError
	case signaling.ReasonMediaFailed:
		return jingle.ReasonFailedTransport
	case signaling.ReasonPeerGone:
		return jingle.ReasonGone
	default:
		return jingle.ReasonGeneralError
	}
}

func reasonFromCondition(cond string) signaling.TerminationReason {
	switch cond {
	case "rejected", jingle.ReasonDecline:
		return signaling.ReasonDecline
	case "retracted", jingle.ReasonGone, jingle.ReasonCancel:
		return signaling.ReasonPeerGone
	case jingle.ReasonBusy:
		return signaling.ReasonBusy
	case jingle.ReasonTimeout:
		return signaling.ReasonRingTimeout
	case jingle.ReasonConnectivityError:
		return signaling.ReasonConnectTimeout
	case jingle.ReasonFailedTransport, jingle.ReasonFailedApplication:
		return signaling.ReasonMediaFailed
	default:
		return signaling.ReasonHangup
	}
}

var sidCounter atomic.Uint64

func newSID() string {
	return fmt.Sprintf("tg-call-%d", sidCounter.Add(1))
}

// telegram user-id from a JID localpart: "12345@gw.example" -> (12345, true)
func ParseTargetJID(jid string) (int64, bool) {
	parts := strings.SplitN(jid, "@", 2)
	if len(parts) == 0 || parts[0] == "" {
		return 0, false
	}
	id, err := strconv.ParseInt(parts[0], 10, 64)
	if err != nil {
		return 0, false
	}
	return id, true
}

// PC with no ICE servers - for tests; production uses MakePCFactory
func DefaultPCFactory() (*webrtc.PeerConnection, error) {
	return buildPC(nil)
}

// PCFactory pulling ICE servers from provider per call, so short-lived TURN
// creds refresh without restarting the component
func MakePCFactory(provider func() []webrtc.ICEServer) func() (*webrtc.PeerConnection, error) {
	return func() (*webrtc.PeerConnection, error) {
		var servers []webrtc.ICEServer
		if provider != nil {
			servers = provider()
		}
		return buildPC(servers)
	}
}

func buildPC(iceServers []webrtc.ICEServer) (*webrtc.PeerConnection, error) {
	// SetHandleUndeclaredSSRCWithoutAnswer: anotherim's libnice starts
	// sending RTP the moment ICE is selected, which often beats the local
	// SetRemoteDescription(answer) - so pion drops the inbound track with
	// "Incoming unhandled RTP ssrc(N), OnTrack will not be fired" and the
	// peer's audio never reaches TG. With this flag pion buffers early RTP.
	s := webrtc.SettingEngine{}
	s.SetHandleUndeclaredSSRCWithoutAnswer(true)
	m := &webrtc.MediaEngine{}
	if err := m.RegisterDefaultCodecs(); err != nil {
		return nil, fmt.Errorf("RegisterDefaultCodecs: %w", err)
	}
	api := webrtc.NewAPI(webrtc.WithSettingEngine(s), webrtc.WithMediaEngine(m))
	pc, err := api.NewPeerConnection(webrtc.Configuration{ICEServers: iceServers})
	if err != nil {
		return nil, err
	}
	// placeholder opus track BEFORE the transceiver (not just a kind).
	// Otherwise pion's RTPSender.Send leaves hasSent=false, the later
	// ReplaceTrack short-circuits without Bind, the real track has no
	// packetizer, and WriteSample silently drops every sample. Caller
	// path always hit this because setupAudio attaches the real track
	// after SetLocalDescription.
	placeholder, err := webrtc.NewTrackLocalStaticSample(
		webrtc.RTPCodecCapability{
			MimeType:    webrtc.MimeTypeOpus,
			ClockRate:   48000,
			Channels:    2,
			SDPFmtpLine: "minptime=10;useinbandfec=1",
		},
		"audio-placeholder",
		"telegabber-placeholder",
	)
	if err != nil {
		_ = pc.Close()
		return nil, fmt.Errorf("placeholder track: %w", err)
	}
	tr, err := pc.AddTransceiverFromTrack(placeholder, webrtc.RTPTransceiverInit{
		Direction: webrtc.RTPTransceiverDirectionSendrecv,
	})
	if err != nil {
		_ = pc.Close()
		return nil, err
	}
	// drain RTCP off the outgoing sender, otherwise its queue can stall
	// under load. exits when pc.Close makes Read error out.
	go drainSenderRTCP(tr.Sender())
	return pc, nil
}

func drainSenderRTCP(sender *webrtc.RTPSender) {
	if sender == nil {
		return
	}
	buf := make([]byte, 1500)
	for {
		if _, _, err := sender.Read(buf); err != nil {
			return
		}
	}
}