package gateway

import (
	"encoding/binary"
	"errors"
)

var ErrInputMalformed = errors.New("input event malformed")

func EncodeInputEvent(event InputEvent) ([]byte, error) {
	if len(event.Device) == 0 || len(event.Device) > 64 || len(event.Payload) > 1024 {
		return nil, ErrInputMalformed
	}
	encoded := make([]byte, 16+len(event.Device)+len(event.Payload))
	copy(encoded[:4], "INP1")
	binary.BigEndian.PutUint32(encoded[4:8], event.Sequence)
	binary.BigEndian.PutUint32(encoded[8:12], uint32(event.Code))
	if event.Pressed {
		encoded[12] = 1
	}
	encoded[13] = byte(len(event.Device))
	binary.BigEndian.PutUint16(encoded[14:16], uint16(len(event.Payload)))
	copy(encoded[16:16+len(event.Device)], event.Device)
	copy(encoded[16+len(event.Device):], event.Payload)
	return encoded, nil
}

func DecodeInputEvent(data []byte) (InputEvent, error) {
	if len(data) < 16 || len(data) > 1179 || string(data[:4]) != "INP1" || (data[12] != 0 && data[12] != 1) {
		return InputEvent{}, ErrInputMalformed
	}
	deviceLength := int(data[13])
	payloadLength := int(binary.BigEndian.Uint16(data[14:16]))
	if deviceLength == 0 || deviceLength > 64 || payloadLength > 1024 || len(data) != 16+deviceLength+payloadLength {
		return InputEvent{}, ErrInputMalformed
	}
	return InputEvent{Sequence: binary.BigEndian.Uint32(data[4:8]), Code: int32(binary.BigEndian.Uint32(data[8:12])), Pressed: data[12] == 1, Device: string(data[16 : 16+deviceLength]), Payload: append([]byte(nil), data[16+deviceLength:]...)}, nil
}