package apdu

import (
	"bytes"
	"encoding/binary"
)

type Command struct {
	Cla  uint8
	Ins  uint8
	P1   uint8
	P2   uint8
	Data []byte
	Le   uint8
}

func NewCommand(cla, ins, p1, p2 uint8, data []byte) *Command {
	return &Command{
		Cla:  cla,
		Ins:  ins,
		P1:   p1,
		P2:   p2,
		Data: data,
	}
}

func (c *Command) Serialize() ([]byte, error) {
	buf := new(bytes.Buffer)

	if err := binary.Write(buf, binary.BigEndian, c.Cla); err != nil {
		return nil, err
	}

	if err := binary.Write(buf, binary.BigEndian, c.Ins); err != nil {
		return nil, err
	}

	if err := binary.Write(buf, binary.BigEndian, c.P1); err != nil {
		return nil, err
	}

	if err := binary.Write(buf, binary.BigEndian, c.P2); err != nil {
		return nil, err
	}

	if len(c.Data) > 0 {
		if err := binary.Write(buf, binary.BigEndian, uint8(len(c.Data))); err != nil {
			return nil, err
		}
		if err := binary.Write(buf, binary.BigEndian, c.Data); err != nil {
			return nil, err
		}
	}

	if err := binary.Write(buf, binary.BigEndian, c.Le); err != nil {
		return nil, err
	}

	return buf.Bytes(), nil
}