package fcast

import (
	"encoding/binary"
	"errors"
)

type OpCode uint8

type MessageHeader struct {
	Size   uint32 // little endian (4) 0-3
	OpCode OpCode // (1) 4-4
}

type RawMessage struct {
	Header MessageHeader // 0-4
	Body   []byte        // 5-
}

func NewMessage(op OpCode, body []byte) *RawMessage {
	return &RawMessage{
		Header: MessageHeader{
			Size:   uint32(len(body) + 1),
			OpCode: op,
		},
		Body: body,
	}
}

func SerializeRaw(message *RawMessage) []byte {
	buf := make([]byte, 4+message.Header.Size)
	binary.LittleEndian.PutUint32(buf[0:4], message.Header.Size)
	buf[4] = byte(message.Header.OpCode)
	copy(buf[5:], message.Body)

	return buf
}

var (
	ErrHeaderTooShort = errors.New("header is too short")
	ErrBodyTooShort   = errors.New("body is too short")
)

func DeserializeRaw(bodyLen, opCode, body []byte) (*RawMessage, error) {

	var msg RawMessage

	msg.Header.Size = binary.LittleEndian.Uint32(bodyLen)
	msg.Header.OpCode = OpCode(uint8(opCode[0]))
	msg.Body = body

	return &msg, nil

}