Javascript XPCOM Long-poll Singleton

longpoll.js

Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 
var gLongPollInstance = null;
 
function LongPoll() {
  if(gLongPollInstance)
    return gLongPollInstance;
 
  gLongPollInstance = this;
  this.wrappedJSObject = this;
 
  this.observerService =
    Components.classes["@mozilla.org/observer-service;1"]
     .getService(Components.interfaces.nsIObserverService);
 
  this.timer = null;
 
  this.endpoint = "http://notifications.example.com";
 
  this.currentRequest =
    Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"]
      .createInstance(Components.interfaces.nsIXMLHttpRequest);
  this.currentRequest.mozBackgroundRequest = true;
  this.currentRequest.onreadystatechange = function(evt) {
    if (gLongPollInstance.currentRequest.readyState == 4) {
      var status = gLongPollInstance.currentRequest.status;
      var timeout = 5000;
      if(status >= 200 && status < 300) {
        gLongPollInstance.observerService.notifyObservers(
          null,
          'longpoll',
          '{"topic":"notification", "data":' + gLongPollInstance.currentRequest.responseText +'}');
      } else {
        timeout = 60000;
      }
      gLongPollInstance.timer =
        Components.classes["@mozilla.org/timer;1"]
          .createInstance(Components.interfaces.nsITimer);
      gLongPollInstance.timer.init(
        gLongPollInstance,
        timeout,
        Components.interfaces.nsITimer.TYPE_ONE_SHOT);
    }
  };
}
 
LongPoll.prototype = {
  classDescription: "Long-Poll Component",
  classID: Components.ID("{1C0E8E86-A661-40D0-AE3D-ABCDEFABCDEF}"),
  contractID: "@example.com/longpoll;1",
  QueryInterface: XPCOMUtils.generateQI([Components.interfaces.nsISupports]),
  setEndpoint: function(nPoint) {
    this.endpoint = nDomain;
    this.currentRequest.abort();
  },
  poll: function() {
    this.currentRequest.open('GET', this.endpoint, true);
    this.currentRequest.send(null);
  },
  observe: function(subject, topic, data) {
    switch(topic) {
      case 'timer-callback':
        this.poll();
      break;
    }
  }
};
 
var components = [LongPoll];
function NSGetModule(compMgr, fileSpec) {
  return XPCOMUtils.generateModule(components);
}

classID: Components.ID("{e6b866e3-41b2-4f05-a4d2-3d4bde0f7ef8}