package udp

import (
	"encoding/binary"
	"errors"
)

type ProtocolPacket struct {
	Opcode uint8
	Data   []byte
}

type ApplicationPacket struct {
	Opcode uint16
	Data   []byte
}

func ParseProtocolPacket(data []byte) (*ProtocolPacket, error) {
	if len(data) < 2 {
		return nil, errors.New("packet too small")
	}

	return &ProtocolPacket{
		Opcode: data[1],
		Data:   data[2:],
	}, nil
}

func (p *ProtocolPacket) Serialize() []byte {
	data := make([]byte, 2+len(p.Data))
	data[0] = 0x00 // Reserved byte
	data[1] = p.Opcode
	copy(data[2:], p.Data)
	return data
}

func ParseApplicationPacket(data []byte) (*ApplicationPacket, error) {
	if len(data) < 2 {
		return nil, errors.New("application packet too small")
	}

	opcode := binary.LittleEndian.Uint16(data[0:2])
	return &ApplicationPacket{
		Opcode: opcode,
		Data:   data[2:],
	}, nil
}

func (p *ApplicationPacket) Serialize() []byte {
	data := make([]byte, 2+len(p.Data))
	binary.LittleEndian.PutUint16(data[0:2], p.Opcode)
	copy(data[2:], p.Data)
	return data
}