package discovery

import (
	"bytes"
	"net"
)

var magicBytes = []byte{0x01, 0x02, 0x01}

func NewPacket() Packet {
	return make(Packet, 7) // 7 = 3 bytes of magic + 4 bytes for ipv4 address
}

func NewPacketWithIP(ip net.IP) Packet {
	return append(magicBytes, []byte(ip.To4())...)
}

type Packet []byte

func (p Packet) IP(n int) net.IP {
	return net.IP(p[3:n])
}

func (p Packet) MagicOk() bool {
	return bytes.Equal(p[:3], magicBytes)
}