package tcp

import (
	"encoding/binary"
	"io"
	"net"

	"go.uber.org/zap"
)

const (
	LengthPrefixSize = 4
)

func readFrame(conn net.Conn) ([]byte, error) {
	lengthBytes := make([]byte, LengthPrefixSize)
	_, err := io.ReadFull(conn, lengthBytes)
	if err != nil {
		return []byte{}, err
	}

	messageLength := binary.BigEndian.Uint32(lengthBytes)

	if messageLength > 65536 {
		zap.L().Warn("message length exceed",
			zap.Uint32("length", messageLength))
	}

	payload := make([]byte, messageLength)
	_, err = io.ReadFull(conn, payload)
	if err != nil {
		return []byte{}, err
	}

	return payload, nil
}

func sendFrame(conn net.Conn, data []byte) error {
	messageLength := uint32(len(data))

	lengthBytes := make([]byte, LengthPrefixSize)
	binary.BigEndian.PutUint32(lengthBytes, messageLength)

	_, err := conn.Write(lengthBytes)
	if err != nil {
		return err
	}

	_, err = conn.Write(data)
	return err
}