import net from 'node:net';

export function probeTcp(monitor) {
  const started = Date.now();
  const timeoutMs = (monitor.timeout ?? 10) * 1000;
  return new Promise((resolve) => {
    const socket = net.createConnection({ host: monitor.host, port: monitor.port });
    const finish = (status, detail) => {
      socket.destroy();
      resolve({ status, latency: Date.now() - started, code: null, detail });
    };
    socket.setTimeout(timeoutMs, () => finish('down', 'TCP 连接超时'));
    socket.once('error', (err) =>
      finish('down', err.code === 'ECONNREFUSED' ? '连接被拒绝（端口关闭）' : (err.code || err.message))
    );
    socket.once('connect', () => finish('up', '端口可连接'));
  });
}