const net = require('net');

const PORT = 1080;
const HOST = '0.0.0.0';

const server = net.createServer((client) => {
  client.once('data', (data) => {
    // SOCKS5 handshake
    if (data[0] !== 0x05) {
      client.end();
      return;
    }

    // No auth required
    client.write(Buffer.from([0x05, 0x00]));

    client.once('data', (data) => {
      if (data[0] !== 0x05 || data[1] !== 0x01) {
        client.write(Buffer.from([0x05, 0x07, 0x00, 0x01, 0, 0, 0, 0, 0, 0]));
        client.end();
        return;
      }

      let host, port;
      const atyp = data[3];

      if (atyp === 0x01) {
        // IPv4
        host = `${data[4]}.${data[5]}.${data[6]}.${data[7]}`;
        port = data.readUInt16BE(8);
      } else if (atyp === 0x03) {
        // Domain
        const len = data[4];
        host = data.slice(5, 5 + len).toString();
        port = data.readUInt16BE(5 + len);
      } else if (atyp === 0x04) {
        // IPv6
        host = '';
        for (let i = 0; i < 16; i += 2) {
          host += data.slice(4 + i, 6 + i).toString('hex');
          if (i < 14) host += ':';
        }
        port = data.readUInt16BE(20);
      } else {
        client.write(Buffer.from([0x05, 0x08, 0x00, 0x01, 0, 0, 0, 0, 0, 0]));
        client.end();
        return;
      }

      const remote = net.createConnection(port, host, () => {
        const response = Buffer.from([0x05, 0x00, 0x00, 0x01, 0, 0, 0, 0, 0, 0]);
        client.write(response);
        client.pipe(remote);
        remote.pipe(client);
      });

      remote.on('error', () => {
        client.write(Buffer.from([0x05, 0x05, 0x00, 0x01, 0, 0, 0, 0, 0, 0]));
        client.end();
      });
    });
  });

  client.on('error', () => {});
});

server.listen(PORT, HOST, () => {
  console.log(`SOCKS5 proxy running on ${HOST}:${PORT}`);
});