// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

import ChildProcess from 'child_process';

// Get an available port
// Works on Unix systems
export function getAvailablePort(defaultPort: number = 3000): Promise<number> {
  return new Promise((resolve) => {
    // Get a list of all ports in use
    ChildProcess.exec('lsof -i -P -n | grep LISTEN', (error, stdout) => {
      if (error) {
        // likely no permission, e.g. CI
        resolve(defaultPort);
        return;
      }

      const portsInUse: number[] = [];
      const regex = /:(\d+) \(LISTEN\)/;
      stdout.split('\n').forEach((line) => {
        const match = regex.exec(line);
        if (match) {
          portsInUse.push(Number(match[1]));
        }
      });
      let port = defaultPort;
      while (portsInUse.includes(port)) {
        port++;
      }
      resolve(port);
    });
  });
}