広告ネットワークを翻訳関連の Google 検索機能と連携させる

function decodeHostname(proxyUrl) {
  const parsedProxyUrl = new URL(proxyUrl);
  const fullHost = parsedProxyUrl.hostname;
  // 1. Extract the domain prefix from the hostname, by removing the
        ".translate.goog" suffix
  let domainPrefix = fullHost.substring(0, fullHost.indexOf('.'));

  // 2. Split _x_tr_enc parameter by "," (comma), save as encodingList
  const encodingList = parsedProxyUrl.searchParams.has('_x_tr_enc') ?
      parsedProxyUrl.searchParams.get('_x_tr_enc').split(',') :
      [];

  // 3. Prepend value of _x_tr_hp parameter to the domain prefix, if it exists
  if (parsedProxyUrl.searchParams.has('_x_tr_hp')) {
    domainPrefix = parsedProxyUrl.searchParams.get('_x_tr_hp') + domainPrefix;
  }

  // 4. Remove '1-' prefix from the output of step 2 if encodingList contains
  //    '1' and the output begins with '1-'.
  if (encodingList.includes('1') && domainPrefix.startsWith('1-')) {
    domainPrefix = domainPrefix.substring(2);
  }

  // 5. Remove '0-' prefix from the output of step 3 if encodingList contains
  //    '0' and the output begins with '0-'.
  //    Set isIdn to true if removed, false otherwise.
  let isIdn = false;
  if (encodingList.includes('0') && domainPrefix.startsWith('0-')) {
    isIdn = true;
    domainPrefix = domainPrefix.substring(2);
  }

  // 6. Replace /\b-\b/ (regex) with '.' (dot) character.
  // 7. Replace '--' (double hyphen) with '-' (hyphen).
  let decodedSegment =
      domainPrefix.replaceAll(/\b-\b/g, '.').replaceAll('--', '-');

  // 8. If isIdn equals true, add the punycode prefix 'xn--'.
  if (isIdn) {
    decodedSegment = 'xn--' + decodedSegment;
  }
  return decodedSegment;
}