import * as childProcess from 'child_process';

/**
 * Downloads a file using a curl child process, to allow for speed-limiting and timeout if download is too slow.
 * Takes as input the host domain name, the path and the file size
 */
export default function downloadWithCurl({ host, path, tempFileName }: {host: string, path: string, tempFileName: string}): Promise<string> {
  return new Promise(function(resolve, reject) {
    const url = `http://${host}${(path.substr(0, 1) === '/' ? '' : '/')}${path}`;

    const parameters: string[] = [
      //...
      '--silent',
      '--limit-rate', '20m', //maximum speed of 20 MB/s = 160 MBit/s
      '--speed-limit', String(Math.round(100 * 1024 * 1024 / 15)), //abort if less than 100 MB in 15 seconds
      '--speed-time', '15',
      '--output', tempFileName,
      url,
    ];

    const spawnedProcess = childProcess.spawn('curl', parameters);

    spawnedProcess.stderr.setEncoding('utf8');
    spawnedProcess.stderr.on('data', function(error) {
      reject(`Error in process:\n> curl ${parameters.join(' ')}\n${error}`);
    });

    spawnedProcess.on('exit', function(code) {
      if (code === 0) {
        resolve(tempFileName);
      } else {
        reject(`Error in process:\n> curl ${parameters.join(' ')}\nNon-zero exit code ${code}.`);
      }
    });
  });
}