package gobridge

import (
	"encoding/binary"
	"encoding/json"
	"fmt"
	"io"
	"net"
)

// writeMsg 将消息以 [4字节长度][JSON载荷] 格式写入连接
func writeMsg(conn net.Conn, msg Message) error {
	data, err := json.Marshal(msg)
	if err != nil {
		return fmt.Errorf("marshal message: %w", err)
	}
	header := make([]byte, 4)
	binary.BigEndian.PutUint32(header, uint32(len(data)))
	_, err = conn.Write(append(header, data...))
	return err
}

// readMsg 从连接中读取一条消息
func readMsg(conn net.Conn) (Message, error) {
	header := make([]byte, 4)
	if _, err := io.ReadFull(conn, header); err != nil {
		return Message{}, fmt.Errorf("read header: %w", err)
	}
	length := binary.BigEndian.Uint32(header)
	body := make([]byte, length)
	if _, err := io.ReadFull(conn, body); err != nil {
		return Message{}, fmt.Errorf("read body: %w", err)
	}
	var msg Message
	if err := json.Unmarshal(body, &msg); err != nil {
		return Message{}, fmt.Errorf("unmarshal message: %w", err)
	}
	return msg, nil
}