package lib

import (
	"net"
)

// Sends a magic packet
func SendPacket(from, to, macStr string) error {
	// Get a binary representation of that MAC Address
	mac, err := net.ParseMAC(macStr)
	if err != nil {
		return err
	}

	// Construct the Magic Packet
	packet := make([]byte, 102)
	index := 0
	for i := 0; i < 6; i++ {
		packet[index] = 0xFF
		index++
	}
	for i := 0; i < 16; i++ {
		for j := 0; j < 6; j++ {
			packet[index] = mac[j]
			index++
		}
	}

	// Resolve addresses
	localAddr, err := net.ResolveUDPAddr("udp4", from)
	if err != nil {
		return err
	}

	broadcastAddr, err := net.ResolveUDPAddr("udp4", to)
	if err != nil {
		return err
	}

	// Send packet
	conn, err := net.DialUDP("udp4", localAddr, broadcastAddr)
	if err != nil {
		return err
	}
	defer conn.Close()

	conn.Write(packet)

	return nil
}