package node

import (
	"errors"
	"net/netip"
)

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

const (
	packetTypeSyn = iota + 1
	packetTypeSynAck
	packetTypeAck
	packetTypeProbe
	packetTypeAddrDiscovery
)

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

type synPacket struct {
	TraceID uint64 // TraceID to match response w/ request.
	// TODO: SentAt int64 // Unixmilli.
	SharedKey     [32]byte // Our shared key.
	Direct        bool
	PossibleAddrs [8]netip.AddrPort // Possible public addresses of the sender.
}

func (p synPacket) Marshal(buf []byte) []byte {
	return newBinWriter(buf).
		Byte(packetTypeSyn).
		Uint64(p.TraceID).
		SharedKey(p.SharedKey).
		Bool(p.Direct).
		AddrPort(p.PossibleAddrs[0]).
		AddrPort(p.PossibleAddrs[1]).
		AddrPort(p.PossibleAddrs[2]).
		AddrPort(p.PossibleAddrs[3]).
		AddrPort(p.PossibleAddrs[4]).
		AddrPort(p.PossibleAddrs[5]).
		AddrPort(p.PossibleAddrs[6]).
		AddrPort(p.PossibleAddrs[7]).
		Build()
}

func parseSynPacket(buf []byte) (p synPacket, err error) {
	err = newBinReader(buf[1:]).
		Uint64(&p.TraceID).
		SharedKey(&p.SharedKey).
		Bool(&p.Direct).
		AddrPort(&p.PossibleAddrs[0]).
		AddrPort(&p.PossibleAddrs[1]).
		AddrPort(&p.PossibleAddrs[2]).
		AddrPort(&p.PossibleAddrs[3]).
		AddrPort(&p.PossibleAddrs[4]).
		AddrPort(&p.PossibleAddrs[5]).
		AddrPort(&p.PossibleAddrs[6]).
		AddrPort(&p.PossibleAddrs[7]).
		Error()
	return
}

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

type ackPacket struct {
	TraceID       uint64
	ToAddr        netip.AddrPort
	PossibleAddrs [8]netip.AddrPort // Possible public addresses of the sender.
}

func (p ackPacket) Marshal(buf []byte) []byte {
	return newBinWriter(buf).
		Byte(packetTypeAck).
		Uint64(p.TraceID).
		AddrPort(p.ToAddr).
		AddrPort(p.PossibleAddrs[0]).
		AddrPort(p.PossibleAddrs[1]).
		AddrPort(p.PossibleAddrs[2]).
		AddrPort(p.PossibleAddrs[3]).
		AddrPort(p.PossibleAddrs[4]).
		AddrPort(p.PossibleAddrs[5]).
		AddrPort(p.PossibleAddrs[6]).
		AddrPort(p.PossibleAddrs[7]).
		Build()

}

func parseAckPacket(buf []byte) (p ackPacket, err error) {
	err = newBinReader(buf[1:]).
		Uint64(&p.TraceID).
		AddrPort(&p.ToAddr).
		AddrPort(&p.PossibleAddrs[0]).
		AddrPort(&p.PossibleAddrs[1]).
		AddrPort(&p.PossibleAddrs[2]).
		AddrPort(&p.PossibleAddrs[3]).
		AddrPort(&p.PossibleAddrs[4]).
		AddrPort(&p.PossibleAddrs[5]).
		AddrPort(&p.PossibleAddrs[6]).
		AddrPort(&p.PossibleAddrs[7]).
		Error()
	return
}

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

// A probeReqPacket is sent from a client to a server to determine if direct
// UDP communication can be used.
type probePacket struct {
	TraceID uint64
}

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

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

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

type localDiscoveryPacket struct{}