package node

import (
	"fmt"
	"log"
	"net/netip"
	"sync/atomic"
	"time"
	"vppn/m"
)

type remotePeers [256]*remotePeer

type peerData struct {
	controlCipher *controlCipher
	dataCipher    *dataCipher
	remoteAddr    netip.AddrPort
	relayIP       byte // Non-zero if we should relay.
}

type remotePeer struct {
	// Immutable data.
	localIP     byte
	remoteIP    byte
	privKey     []byte
	localPublic bool // True if local node is public.
	iface       *ifWriter
	conn        *connWriter

	// Shared state.
	shared *atomic.Pointer[peerData]

	// Only used in HandlePeerUpdate.
	peerVersion int64

	// Only used in HandlePacket / Not synchronized.
	dupCheck   *dupCheck
	decryptBuf []byte

	// Only used in SendData / Not synchronized.
	encryptBuf []byte

	// Used for sending control and data packets. Atomic access only.
	counter uint64

	// For communicating with the supervisor thread.
	peerUpdates    chan *m.Peer
	controlPackets chan controlPacket
}

func newRemotePeer(conf m.PeerConfig, remoteIP byte, iface *ifWriter, conn *connWriter) *remotePeer {
	rp := &remotePeer{
		localIP:        conf.PeerIP,
		remoteIP:       remoteIP,
		privKey:        conf.EncPrivKey,
		localPublic:    addrIsValid(conf.PublicIP),
		iface:          iface,
		conn:           conn,
		shared:         &atomic.Pointer[peerData]{},
		dupCheck:       newDupCheck(0),
		decryptBuf:     make([]byte, bufferSize),
		encryptBuf:     make([]byte, bufferSize),
		counter:        uint64(time.Now().Unix()) << 30,
		peerUpdates:    make(chan *m.Peer),
		controlPackets: make(chan controlPacket, 512),
	}

	pd := peerData{}
	rp.shared.Store(&pd)

	go newPeerSuper(rp).Run()

	return rp
}

func (rp *remotePeer) logf(msg string, args ...any) {
	log.Printf(fmt.Sprintf("[%03d] ", rp.remoteIP)+msg, args...)
}

func (rp *remotePeer) HandlePeerUpdate(peer *m.Peer) {
	if peer != nil && peer.Version != rp.peerVersion {
		rp.peerUpdates <- peer
		rp.peerVersion = peer.Version
	}
}

// ----------------------------------------------------------------------------

// HandlePacket accepts a raw data packet coming in from the network.
//
// This function is called by a single thread.
func (rp *remotePeer) HandlePacket(addr netip.AddrPort, h header, data []byte) {
	switch h.StreamID {
	case controlStreamID:
		rp.handleControlPacket(addr, h, data)

	case dataStreamID:
		rp.handleDataPacket(data)

	case forwardStreamID:
		fallthrough
		// TODO
		//rp.handleForwardPacket(h, data)
	default:
		rp.logf("Unknown stream ID: %d", h.StreamID)
	}
}

// ----------------------------------------------------------------------------

func (rp *remotePeer) handleControlPacket(addr netip.AddrPort, h header, data []byte) {
	shared := rp.shared.Load()
	if shared.controlCipher == nil {
		rp.logf("Not connected (control).")
		return
	}

	out, ok := shared.controlCipher.Decrypt(data, rp.decryptBuf)
	if !ok {
		rp.logf("Failed to decrypt control packet.")
		return
	}

	if len(out) == 0 {
		rp.logf("Empty control packet from: %d", h.SourceIP)
		return
	}

	if rp.dupCheck.IsDup(h.Counter) {
		rp.logf("Duplicate control packet: %d", h.Counter)
		return
	}

	if h.DestIP != rp.localIP {
		// TODO: Forward control packet.
		// TODO: Probably this should be dropped.
		// Control packets should be forwarded as data for efficiency.
		return
	}

	pkt := controlPacket{
		SrcIP:      h.SourceIP,
		RemoteAddr: addr,
	}

	var err error

	switch out[0] {
	case packetTypePing:
		pkt.Payload, err = parsePingPacket(out)
	case packetTypePong:
		pkt.Payload, err = parsePongPacket(out)
	default:
		rp.logf("Unknown control packet type: %d", out[0])
		return
	}

	if err != nil {
		rp.logf("Failed to parse control packet: %v", err)
		return
	}

	select {
	case rp.controlPackets <- pkt:
	default:
		rp.logf("Dropping control packet.")
	}
}

func (rp *remotePeer) handleDataPacket(data []byte) {
	shared := rp.shared.Load()
	if shared.dataCipher == nil {
		rp.logf("Not connected (recv).")
		return
	}

	dec, ok := shared.dataCipher.Decrypt(data, rp.decryptBuf)
	if !ok {
		rp.logf("Failed to decrypt data packet.")
		return
	}

	rp.iface.Write(dec)
}

// ----------------------------------------------------------------------------

// SendData sends data coming from the interface going to the network.
//
// This function is called by a single thread.
func (rp *remotePeer) SendData(data []byte) {
	shared := rp.shared.Load()
	if shared.dataCipher == nil || shared.remoteAddr == zeroAddrPort {
		rp.logf("Not connected (send).")
		return
	}

	h := header{
		StreamID: dataStreamID,
		Counter:  atomic.AddUint64(&rp.counter, 1),
		SourceIP: rp.localIP,
		DestIP:   rp.remoteIP,
	}

	enc := shared.dataCipher.Encrypt(h, data, rp.encryptBuf)
	rp.conn.WriteTo(enc, shared.remoteAddr)
}