const net = require('node:net');
const { Transform } = require('node:stream');

const LOCAL_PORT = 1935;
const REMOTE_PORT = 1936;
const REMOTE_ADDR = '127.0.0.1';

/**
 * 将十进制数字转换为4字节的 Buffer
 * @param {number} number 数字
 * @param {string} byteOrder 排序
 * @returns {Buffer}
 */
function toFixed4ByteBuffer(number, byteOrder = 'BE') {
  if (number < 0 || number > 0xFFFFFFFF) {
      throw new Error('Number must be between 0 and 4294967295');
  }

  const buffer = Buffer.alloc(4); // 创建一个4字节的 Buffer

  if (byteOrder === 'BE') {
      buffer.writeUInt32BE(number, 0); // 大端顺序
  } else if (byteOrder === 'LE') {
      buffer.writeUInt32LE(number, 0); // 小端顺序
  } else {
      throw new Error('Invalid byte order');
  }

  return buffer;
}

class CustomTransform extends Transform {
  _transform(chunk, encoding, callback) {
    const packet = Buffer.concat([toFixed4ByteBuffer(chunk.length), chunk]);
    this.push(packet, encoding);
    callback();
  }
}

const getIdentifier = () => {
  return Buffer.from([0x01, 0x02, 0x03, 0x04]);
};

function bootstrap() {
  const proxy = net.createServer();

  proxy.on('connection', (clientSocket) => {
    console.log('Client connected');

    // 创建一个新的连接到目标服务器
    const targetSocket = net.createConnection({
      host: REMOTE_ADDR, // 目标服务器的地址
      port: REMOTE_PORT // 目标服务器的端口
    }, () => {
      console.log('Proxy connected to target server');
    });

    // 将接收到的数据转发到目标服务器
    clientSocket.pipe(new CustomTransform()).pipe(targetSocket)

    // 将目标服务器的响应数据转发回客户端
    targetSocket.on('data', chunk => {
      clientSocket.write(chunk);
    });

    // 处理代理与目标服务器的关闭事件
    clientSocket.on('close', () => {
      targetSocket.end();
    });
    targetSocket.on('close', () => {
      clientSocket.end();
    });
  });

  // 监听本地端口
  proxy.listen(LOCAL_PORT, () => {
    console.log('Zone1 proxy server is listening on port ' + LOCAL_PORT);
  });
}
bootstrap();