package node

import (
	"errors"
	"net/netip"
)

var (
	errMalformedPacket   = errors.New("malformed packet")
	errUnknownPacketType = errors.New("unknown packet type")
)

const (
	packetTypeSyn = iota + 1
	packetTypeSynAck
	packetTypeAck
	packetTypePing
	packetTypePong
	packetTypeRelayed
)

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

type controlPacket struct {
	SrcIP      byte
	RemoteAddr netip.AddrPort
	Payload    any
}

func (p *controlPacket) ParsePayload(buf []byte) (err error) {
	switch buf[0] {
	case packetTypeSyn:
		p.Payload, err = parseSynPacket(buf)
	case packetTypeSynAck:
		p.Payload, err = parseSynAckPacket(buf)
	case packetTypeAck:
		p.Payload, err = parseAckPacket(buf)
	default:
		return errUnknownPacketType
	}
	return err
}

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

type synPacket struct {
	TraceID   uint64   // TraceID to match response w/ request.
	SharedKey [32]byte // Our shared key.
	RelayIP   byte
}

func (p synPacket) Marshal(buf []byte) []byte {
	return newBinWriter(buf).
		Byte(packetTypeSyn).
		Uint64(p.TraceID).
		SharedKey(p.SharedKey).
		Byte(p.RelayIP).
		Build()
}

func parseSynPacket(buf []byte) (p synPacket, err error) {
	err = newBinReader(buf[1:]).
		Uint64(&p.TraceID).
		SharedKey(&p.SharedKey).
		Byte(&p.RelayIP).
		Error()
	return
}

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

type synAckPacket struct {
	TraceID uint64
}

func newSynAckPacket(traceID uint64) synAckPacket {
	return synAckPacket{traceID}
}

func (p synAckPacket) Marshal(buf []byte) []byte {
	return newBinWriter(buf).
		Byte(packetTypeSynAck).
		Uint64(p.TraceID).
		Build()
}

func parseSynAckPacket(buf []byte) (p synAckPacket, err error) {
	err = newBinReader(buf[1:]).
		Uint64(&p.TraceID).
		Error()
	return
}

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

type ackPacket struct {
	TraceID uint64
}

func (p ackPacket) Marshal(buf []byte) []byte {
	return newBinWriter(buf).
		Byte(packetTypeAck).
		Uint64(p.TraceID).
		Build()
}

func parseAckPacket(buf []byte) (p ackPacket, err error) {
	err = newBinReader(buf[1:]).
		Uint64(&p.TraceID).
		Error()
	return
}