(function() {

  window.UoSLive = {};

  var busStopRequests = {};
  var busStopCache = {};

  UoSLive.getBusStopURL = function(busStop) {
    var base = "http://bus.southampton.ac.uk/bus-stop/";

    var url = base + busStop + ".json";

    return url;
  };

  UoSLive.subscribeToBusStop = function(busStop, callback) {

    if (busStop in busStopCache) {
      var result = busStopCache[busStop];
      if (result.timeFetched > (Date.now() - 60000)) {
        callback(result);
      }
    }

    var url = UoSLive.getBusStopURL(busStop);

    var req = new Pollymer.Request();

    busStopRequests[busStop] = req;

    req.recurring = true;

    req.on('finished', function(code, result, headers) {
      result.timeFetched = Date.now();
      busStopCache[busStop] = result;

      callback(result);
    });

    req.on('error', function(reason) {
    });

    req.maxTries = -1;
    req.maxDelay = 60000;
    req.minDelay = 60000;

    req.start('GET', url);
  };

  UoSLive.unsubscribeToBusStop = function(busStop) {

    var req = busStopRequests[busStop];

    req.abort();

  }

})();