package hotline

import (
	"bytes"
	"encoding/binary"
	"errors"
)

type transfer struct {
	Protocol        [4]byte // "HTXF" 0x48545846
	ReferenceNumber [4]byte // Unique ID generated for the transfer
	DataSize        [4]byte // File size
	RSVD            [4]byte // Not implemented in Hotline Protocol
}

var HTXF = [4]byte{0x48, 0x54, 0x58, 0x46} // (HTXF) is the only supported transfer protocol

func (tf *transfer) Write(b []byte) (int, error) {
	if err := binary.Read(bytes.NewReader(b), binary.BigEndian, tf); err != nil {
		return 0, err
	}

	if tf.Protocol != HTXF {
		return 0, errors.New("invalid protocol")
	}

	return len(b), nil
}