const net = require('net');

function checkPortUsable(port) {
  return new Promise((resolve, reject) => {
    const server = net.createConnection({ port });
    server.on('connect', () => {
      server.end();
      reject(`Port ${port} is not available!`);
    });
    server.on('error', () => {
      resolve(port);
    });
  });
}

function randomNumByRange(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

function findUsablePort(port, minPort = 10000, maxPort = 65536) {
  const retry = () => {
    const port = randomNumByRange(minPort, maxPort);
    return findUsablePort(port, minPort, maxPort);
  };
  return checkPortUsable(port)
    .then(() => port)
    .catch(retry);
}

module.exports = {
  findUsablePort,
  checkPortUsable,
};