function JSONtoRSS(json, type, key) {
  oAuth();

  var options = {
    method: 'get',
    oAuthServiceName: 'twitter',
    oAuthUseToken: 'always',
  };

  try {
    var result = UrlFetchApp.fetch(json, options);

    if (result.getResponseCode() === 200) {
      var tweets = Utilities.jsonParse(result.getContentText());

      if (tweets) {
        var len = tweets.length;

        var rss = '';

        if (len) {
          rss = '<?xml version="1.0"?><rss version="2.0">';
          rss += ' <channel><title>Twitter ' + type + ': ' + key + '</title>';
          rss += ' <link>' + htmlentities(json) + '</link>';
          rss += ' <pubDate>' + new Date() + '</pubDate>';

          for (var i = 0; i < len; i++) {
            var sender = tweets[i].user.screen_name;
            var tweet = htmlentities(tweets[i].text);

            rss += '<item><title>' + sender + ': ' + tweet + '</title>';
            rss += ' <author>' + tweets[i].user.name + ' (@' + sender + ')</author>';
            rss += ' <pubDate>' + tweets[i].created_at + '</pubDate>';
            rss += " <guid isPermaLink='false'>" + tweets[i].id_str + '</guid>';
            rss += ' <link>https://twitter.com/' + sender + '/statuses/' + tweets[i].id_str + '</link>';
            rss += ' <description>' + tweet + '</description>';
            rss += '</item>';
          }

          rss += '</channel></rss>';

          return rss;
        }
      }
    }
  } catch (e) {
    Logger.log(e.toString());
  }
}

function doGet(e) {
  var a = e.parameter.action;
  var q = e.parameter.q;

  var feed = 'https://api.twitter.com/1.1/';

  switch (a) {
    case 'timeline':
      feed += 'statuses/user_timeline.json?screen_name=' + q;
      break;
    case 'search':
      feed += 'search/tweets.json?q=' + encodeURIComponent(q);
      break;
    case 'favorites':
      feed += 'favorites/list.json?screen_name=' + q;
      break;
    case 'list':
      var i = q.split('/');
      feed += 'lists/statuses.json?slug=' + i[1] + '&owner_screen_name=' + i[0];
      break;
    default:
      feed += 'statuses/user_timeline.json';
      break;
  }

  var id = Utilities.base64Encode(feed);

  var cache = CacheService.getPublicCache();
  var rss = cache.get(id);

  if (!rss) {
    rss = JSONtoRSS(feed, a, q);
    cache.put(id, rss, 3600);
  }

  return ContentService.createTextOutput(rss).setMimeType(ContentService.MimeType.RSS);
}