package node

import (
	"errors"
	"unsafe"
)

var errMalformedPacket = errors.New("malformed packet")

const (
	packetTypeInvalid = iota

	// Used to maintain connection.
	packetTypePing
	packetTypePong
)

type routingPacket struct {
	Type    byte   // One of the packetType* constants.
	TraceID uint64 // For matching requests and responses.
}

func newRoutingPacket(reqType byte, traceID uint64) routingPacket {
	return routingPacket{
		Type:    reqType,
		TraceID: traceID,
	}
}

func (p routingPacket) Marshal(buf []byte) []byte {
	buf = buf[:32] // Reserve 32 bytes just in case we need to add anything.
	buf[0] = p.Type
	*(*uint64)(unsafe.Pointer(&buf[1])) = uint64(p.TraceID)
	return buf
}

func (p *routingPacket) Parse(buf []byte) error {
	if len(buf) != 32 {
		return errMalformedPacket
	}
	p.Type = buf[0]
	p.TraceID = *(*uint64)(unsafe.Pointer(&buf[1]))
	return nil
}