NchanSubscriber.js

/*
 * NchanSubscriber
 * usage: var sub = new NchanSubscriber(url, opt);
 * 
 * opt = {
 *   subscriber: 'longpoll', 'eventsource', or 'websocket',
 *     //or an array of the above indicating subscriber type preference
 *   reconnect: undefined or 'session' or 'persist'
 *     //if the HTML5 sessionStore or localStore should be used to resume
 *     //connections interrupted by a page load
 *   shared: true or undefined
 *     //share connection to same subscriber url between browser 
 *     //windows and tabs using localStorage. In shared mode, 
 *     //only 1 running subscriber is allowed per url per window/tab.
 * }
 * 
 * sub.on("message", function(message, message_metadata) {
 *   // message is a string
 *   // message_metadata may contain 'id' and 'content-type'
 * });
 * 
 * sub.on('connect', function(evt) {
 *   //fired when first connected. 
 * });
 * 
 * sub.on('disconnect', function(evt) {
 *   // when disconnected.
 * });
 * 
 * sub.on('error', function(code, message) {
 *   //error callback. not sure about the parameters yet
 * });
 * 
 * sub.reconnect; // should subscriber try to reconnect? true by default.
 * sub.reconnectTimeout; //how long to wait to reconnect? does not apply to EventSource, which reconnects on its own.
 * sub.lastMessageId; //last message id. useful for resuming a connection without loss or repetition.
 * 
 * sub.start(); // begin (or resume) subscribing
 * sub.stop(); // stop subscriber. do not reconnect.
 */

//Thanks Darren Whitlen ( @prawnsalad ) for your feedback


;(function (global, moduleName, factory) { // eslint-disable-line
  "use strict";
  /* eslint-disable no-undef */
  var newModule = factory(global);
  if (typeof module === "object" && module != null && module.exports) {
    module.exports = newModule;
  } else if (typeof define === "function" && define.amd) {
    define(function () { return newModule; });
  } else {
    global[moduleName] = newModule;
  }
  /* eslint-enable no-undef */
})(typeof window !== "undefined" ? window : this, "NchanSubscriber", function factory(global, undefined) { // eslint-disable-line

  // https://github.com/yanatan16/nanoajax
  var nanoajax={};
  (function(){var e=["responseType","withCredentials","timeout","onprogress"];nanoajax.ajax=function(r,o){var a=r.headers||{},u=r.body,s=r.method||(u?"POST":"GET"),i=false;var f=t(r.cors);function l(e,t){return function(){if(!i){o(f.status===undefined?e:f.status,f.status===0?"Error":f.response||f.responseText||t,f);i=true}}}f.open(s,r.url,true);var d=f.onload=l(200);f.onreadystatechange=function(){if(f.readyState===4)d()};f.onerror=l(null,"Error");f.ontimeout=l(null,"Timeout");f.onabort=l(null,"Abort");if(u){n(a,"X-Requested-With","XMLHttpRequest");if(!global.FormData||!(u instanceof global.FormData)){n(a,"Content-Type","application/x-www-form-urlencoded")}}for(var p=0,c=e.length,g;p<c;p++){g=e[p];if(r[g]!==undefined)f[g]=r[g]}for(var g in a)f.setRequestHeader(g,a[g]);f.send(u);return f};function t(e){if(e&&global.XDomainRequest&&!/MSIE 1/.test(navigator.userAgent))return new XDomainRequest;if(global.XMLHttpRequest)return new XMLHttpRequest}function n(e,t,n){e[t]=e[t]||n}})(); // eslint-disable-line


  // https://github.com/component/emitter
  function Emitter(t){return t?mixin(t):void 0}function mixin(t){for(var e in Emitter.prototype)t[e]=Emitter.prototype[e];return t}Emitter.prototype.on=Emitter.prototype.addEventListener=function(t,e){return this._callbacks=this._callbacks||{},(this._callbacks["$"+t]=this._callbacks["$"+t]||[]).push(e),this},Emitter.prototype.once=function(t,e){function i(){this.off(t,i),e.apply(this,arguments)}return i.fn=e,this.on(t,i),this},Emitter.prototype.off=Emitter.prototype.removeListener=Emitter.prototype.removeAllListeners=Emitter.prototype.removeEventListener=function(t,e){if(this._callbacks=this._callbacks||{},0==arguments.length)return this._callbacks={},this;var i=this._callbacks["$"+t];if(!i)return this;if(1==arguments.length)return delete this._callbacks["$"+t],this;for(var r,s=0;s<i.length;s++)if(r=i[s],r===e||r.fn===e){i.splice(s,1);break}return this},Emitter.prototype.emit=function(t){this._callbacks=this._callbacks||{};var e=[].slice.call(arguments,1),i=this._callbacks["$"+t];if(i){i=i.slice(0);for(var r=0,s=i.length;s>r;++r)i[r].apply(this,e)}return this},Emitter.prototype.listeners=function(t){return this._callbacks=this._callbacks||{},this._callbacks["$"+t]||[]},Emitter.prototype.hasListeners=function(t){return!!this.listeners(t).length};// eslint-disable-line

  var ughbind = (Function.prototype.bind
    ? function ughbind(fn, thisObj) {
      return fn.bind(thisObj);
    }
    : function ughbind(fn, thisObj) {
      return function() {
        fn.apply(thisObj, arguments);
      };
    }
  );

  var sharedSubscriberTable={};

  "use strict"; 
  function NchanSubscriber(url, opt) {
    if(typeof window !== "undefined" && this === window) {
      throw "use 'new NchanSubscriber(...)' to initialize";
    }
    
    this.url = url;
    opt = opt || {};
    
    //which transport should i use?
    if(typeof opt === "string") {
      opt = {subscriber: opt}; 
    }
    if(opt.transport && !opt.subscriber) {
      opt.subscriber = opt.transport;
    }
    if(typeof opt.subscriber === "string") {
      opt.subscriber = [ opt.subscriber ];
    }
    this.desiredTransport = opt.subscriber;
    
    if(opt.shared) {
      if (!("localStorage" in global)) {
        throw "localStorage unavailable for use in shared NchanSubscriber";
      }
      
      var pre = "NchanSubscriber:" + this.url + ":shared:";
      var sharedKey = function(key) { return pre + key; };
      var localStorage = global.localStorage;
      this.shared = {
        id: "" + Math.random() + Math.random(),
        key: sharedKey,
        get: function(key) {
          return localStorage.getItem(sharedKey(key));
        },
        set: function(key, val) {
          return localStorage.setItem(sharedKey(key), val);
        },
        setWithId: ughbind(function(key, val) {
          return this.shared.set(key, "##" + this.shared.id + ":" + val);
        }, this),
        getWithId: ughbind(function(key) {
          return this.shared.stripIdFromVal(this.shared.get(key));
        }, this),
        stripIdFromVal: function(val) {
          if(!val) {
            return val;
          }
          var sep = val.indexOf(":");
          if(val[0]!=val[1] || val[0]!="#" || !sep) {
            //throw "not an event value with id";
            return val; //for backwards-compatibility
          }
          return val.substring(sep+1, val.length);
        },
        remove: function(key) {
          return localStorage.removeItem(sharedKey(key));
        },
        matchEventKey: ughbind(function(ev, key) {
          if(ev.storageArea && ev.storageArea != localStorage){
            return false;
          }
          return ev.key == sharedKey(key);
        }, this),
        matchEventKeyWithId: ughbind(function(ev, key) {
          if(this.shared.matchEventKey(ev, key)) {
            var val = ev.newValue;
            var sep = val.indexOf(":");
            if(val[0]!=val[1] || val[0]!="#" || !sep) {
              //throw "not an event value with id";
              return true; //for backwards-compatibility
            }
            var id = val.substring(2, sep);
            return (id != this.shared.id); //ignore own events (accommodations for IE. Fuckin' IE, even after all these years...)
          }
          else {
            return false;
          }
        }, this),
        setRole: ughbind(function(role) {
          //console.log(this.url, "set shared role to ", role);
          if(role == "master" && this.shared.role != "master") {
            var now = new Date().getTime()/1000;
            this.shared.setWithId("master:created", now);
            this.shared.setWithId("master:lastSeen", now);
          }
          if(role == "slave" && !this.lastMessageId) {
            this.lastMessageId = this.shared.get("msg:id");
          }
          this.shared.role = role;
          return this;
        }, this),
        
        demoteToSlave: ughbind(function() {
          //console.log("demote to slave");
          if(this.shared.role != "master") {
            throw "can't demote non-master to slave";
          }
          if(this.running) {
            this.stop();
            this.shared.setRole("slave");
            this.initializeTransport();
            this.start();
          }
          else {
            this.initializeTransport();
          }
        }, this),
        
        maybePromoteToMaster: ughbind(function() {
          if(!(this.running || this.starting)) {
            //console.log(this.url, "stopped Subscriber won't be promoted to master");
            return this;
          }
          if(this.shared.maybePromotingToMaster) {
            //console.log(this.url, " already maybePromotingToMaster");
            return;
          }
          this.shared.maybePromotingToMaster = true;
          
          //console.log(this.url, "maybe promote to master");
          var processRoll;
          
          var lotteryRoundDuration = 2000;
          var currentContenders = 0;
          
          //roll the dice
          var roll = Math.random();
          var bestRoll = roll;
          
          var checkRollInterval;
          var checkRoll = ughbind(function(dontProcess) {
            var latestSharedRollTime = parseFloat(this.shared.getWithId("lotteryTime"));
            var latestSharedRoll = parseFloat(this.shared.getWithId("lottery"));
            var notStale = !latestSharedRollTime || (latestSharedRollTime > (new Date().getTime() - lotteryRoundDuration * 2));
            if(notStale && latestSharedRoll && (!bestRoll || latestSharedRoll > bestRoll)) {
              bestRoll = latestSharedRoll;
            }
            if(!dontProcess) {
              processRoll();
            }
          }, this);
          
          checkRoll(true);
          this.shared.setWithId("lottery", roll);
          this.shared.setWithId("lotteryTime", new Date().getTime() / 1000);
          
          var rollCallback = ughbind(function(ev) {
            if(this.shared.matchEventKeyWithId(ev, "lottery") && ev.newValue) {
              currentContenders += 1;
              var newVal = parseFloat(this.shared.stripIdFromVal(ev.newValue));
              var oldVal = parseFloat(this.shared.stripIdFromVal(ev.oldValue));
              if(oldVal > newVal) {
                this.shared.setWithId("lottery", oldVal);
              }
              
              if(!bestRoll || newVal >= bestRoll) {
                //console.log("new bestRoll", newVal);
                bestRoll = newVal;
              }
            }
          }, this);
          global.addEventListener("storage", rollCallback);
          
          var finish = ughbind(function() {
            //console.log("finish");
            this.shared.maybePromotingToMaster = false;
            //console.log(this.url, this.shared.role);
            global.removeEventListener("storage", rollCallback);
            if(checkRollInterval) {
              clearInterval(checkRollInterval);
            }
            if(this.shared && this.shared.role == "master") {
              this.shared.remove("lottery");
              this.shared.remove("lotteryTime");
            }
            if(this.running) {
              this.stop();
              this.initializeTransport();
              this.start();
            }
            else {
              this.initializeTransport();
              if(this.starting) {
                this.start();
              }
            }
          }, this);
          
          processRoll = ughbind(function() {
            //console.log("roll, bestroll", roll, bestRoll);
            if(roll < bestRoll) {
              //console.log(this.url, "loser");
              this.shared.setRole("slave");
              finish();
            }
            else if(roll >= bestRoll) {
              //var now = new Date().getTime() / 1000;
              //var lotteryTime = parseFloat(this.shared.getWithId("lotteryTime"));
              //console.log(lotteryTime, now - lotteryRoundDuration/1000);
              if(currentContenders == 0) {
                //console.log("winner, no more contenders!");
                this.shared.setRole("master");
                finish();
              }
              else {
                //console.log("winning, but have contenders", currentContenders);
                currentContenders = 0;
              }
            }
          }, this);
          
          checkRollInterval = global.setInterval(checkRoll, lotteryRoundDuration);
        }, this),
        masterCheckInterval: 10000
      };
    }
    
    this.lastMessageId = opt.id || opt.msgId;
    this.reconnect = typeof opt.reconnect == "undefined" ? true : opt.reconnect;
    this.reconnectTimeout = opt.reconnectTimeout || 1000;
    
    
    var saveConnectionState;
    if(!opt.reconnect) {
      saveConnectionState = function() {};
    }
    else {
      var index = "NchanSubscriber:" + url + ":lastMessageId";
      var storage;
      if(opt.reconnect == "persist") {
        storage = ("localStorage" in global) && global.localStorage;
        if(!storage)
          throw "can't use reconnect: 'persist' option: localStorage not available";
      }
      else if(opt.reconnect == "session") {
        storage = ("sessionStorage" in global) && global.sessionStorage;
        if(!storage)
          throw "can't use reconnect: 'session' option: sessionStorage not available";
      }
      else {
        throw "invalid 'reconnect' option value " + opt.reconnect;
      }
      saveConnectionState = ughbind(function(msgid) {
        if(this.shared && this.shared.role == "slave") return;
        storage.setItem(index, msgid);
      }, this);
      this.lastMessageId = storage.getItem(index);
    }
    
    var onUnloadEvent = ughbind(function() {
      if(this.running) {
        this.stop();
      }
      if(this.shared && this.shared.role == "master") {
        this.shared.setWithId("status", "disconnected");
      }
    }, this);
    global.addEventListener("beforeunload", onUnloadEvent, false);
    // swap `beforeunload` to `unload` after DOM is loaded
    global.addEventListener("DOMContentLoaded", function() {
      global.removeEventListener("beforeunload", onUnloadEvent, false);
      global.addEventListener("unload", onUnloadEvent, false);
    }, false);
    
    
    var notifySharedSubscribers;
    if(this.shared) {
      notifySharedSubscribers = ughbind(function(name, data) {
        if(this.shared.role != "master") {
          return;
        }
        
        if(name == "message") {
          this.shared.set("msg:id", data[1] && data[1].id || "");
          this.shared.set("msg:content-type", data[1] && data[1]["content-type"] || "");
          this.shared.set("msg", data[0]);
        }
        else if(name == "error") {
          //TODO 
        }
        else if(name == "connecting") {
          this.shared.setWithId("status", "connecting");
        }
        else if(name == "connect") {
          this.shared.setWithId("status", "connected");
        }
        else if(name == "reconnect") {
          this.shared.setWithId("status", "reconnecting");
        }
        else if(name == "disconnect") {
          this.shared.setWithId("status", "disconnected");
        }
      }, this);
    }
    else {
      notifySharedSubscribers = function(){};
    }
    
    var restartTimeoutIndex;
    var stopHandler = ughbind(function() {
      if(!restartTimeoutIndex && this.running && this.reconnect && !this.transport.reconnecting && !this.transport.doNotReconnect) {
        //console.log("stopHAndler reconnect plz", this.running, this.reconnect);
        notifySharedSubscribers("reconnect");
        restartTimeoutIndex = global.setTimeout(ughbind(function() {
          restartTimeoutIndex = null;
          this.stop();
          this.start();
        }, this), this.reconnectTimeout);
      }
      else {
        notifySharedSubscribers("disconnect");
      }
    }, this);
    
    this.on("message", function msg(msg, meta) {
      this.lastMessageId=meta.id;
      if(meta.id) {
        saveConnectionState(meta.id);
      }
      notifySharedSubscribers("message", [msg, meta]);
      //console.log(msg, meta);
    });
    this.on("error", function fail(code, text) {
      stopHandler(code, text);
      notifySharedSubscribers("error", [code, text]);
      //console.log("failure", code, text);
    });
    this.on("connect", function() {
      this.connected = true;
      notifySharedSubscribers("connect");
    });
    this.on("__disconnect", function fail(code, text) {
      this.connected = false;
      this.emit("disconnect", code, text);
      stopHandler(code, text);
      //console.log("__disconnect", code, text);
    });
  }

  Emitter(NchanSubscriber.prototype);

  NchanSubscriber.prototype.initializeTransport = function(possibleTransports) {
    if(possibleTransports) {
      this.desiredTransport = possibleTransports;
    }
    if(this.shared && this.shared.role == "slave") {
      this.transport = new this.SubscriberClass["__slave"](ughbind(this.emit, this)); //try it
    }
    else {
      var tryInitializeTransport = ughbind(function(name) {
        if(!this.SubscriberClass[name]) {
          throw "unknown subscriber type " + name;
        }
        try {
          this.transport = new this.SubscriberClass[name](ughbind(this.emit, this)); //try it
          return this.transport;
        } catch(err) { /*meh...*/ }
      }, this);
      
      var i;
      if(this.desiredTransport) {
        for(i=0; i<this.desiredTransport.length; i++) {
          if(tryInitializeTransport(this.desiredTransport[i])) {
            break;
          }
        }
      }
      else {
        for(i in this.SubscriberClass) {
          if (this.SubscriberClass.hasOwnProperty(i) && i[0] != "_" && tryInitializeTransport(i)) {
            break;
          }
        }
      }
    }
    if(! this.transport) {
      throw "can't use any transport type";
    }
  };

  var storageEventListener;

  NchanSubscriber.prototype.start = function() {
    if(this.running)
      throw "Can't start NchanSubscriber, it's already started.";
    
    this.starting = true;
    
    if(this.shared) {
      if(sharedSubscriberTable[this.url] && sharedSubscriberTable[this.url] != this) {
        throw "Only 1 shared subscriber allowed per url per window/tab.";
      }
      sharedSubscriberTable[this.url] = this;
      
      if(!this.shared.role) {
        var status = this.shared.getWithId("status");
        storageEventListener = ughbind(function(ev) {
          if(this.shared.matchEventKeyWithId(ev, "status")) {
            var newValue = this.shared.stripIdFromVal(ev.newValue);
            if(newValue == "disconnected") {
              if(this.shared.role == "slave") {
                //play the promotion lottery
                //console.log(this.url, "status changed to disconnected, maybepromotetomaster", ev.newValue, ev.oldValue);
                this.shared.maybePromoteToMaster();
              }
              else if(this.shared.role == "master") {
                //do nothing
                //console.log(this.url, "current role is master, do nothing?...");
              }
            }
          }
          else if(this.shared.role == "master" && this.shared.matchEventKeyWithId(ev, "master:created") && ev.newValue) {
            //a new master has arrived. demote to slave.
            this.shared.demoteToSlave();
          }
        }, this);
        global.addEventListener("storage", storageEventListener);
        if(status == "disconnected") {
          //console.log(this.url, "status == disconnected, maybepromotetomaster");
          this.shared.maybePromoteToMaster();
        }
        else {
          this.shared.setRole(status ? "slave" : "master");
          this.initializeTransport();
        }
      }
      
      if(this.shared.role == "master") {
        this.shared.setWithId("status", "connecting");
        this.transport.listen(this.url, this.lastMessageId);
        this.running = true;
        delete this.starting;
        
        //master checkin interval
        this.shared.masterIntervalCheckID = global.setInterval(ughbind(function() {
          this.shared.setWithId("master:lastSeen", new Date().getTime() / 1000);
        }, this), this.shared.masterCheckInterval * 0.8);
      }
      else if(this.shared.role == "slave") {
        this.transport.listen(this.url, this.shared);
        this.running = true;
        delete this.starting;
        
        //slave check if master is around
        this.shared.masterIntervalCheckID = global.setInterval(ughbind(function() {
          var lastCheckin = parseFloat(this.shared.getWithId("master:lastSeen"));
          if(!lastCheckin || lastCheckin < (new Date().getTime() / 1000) - this.shared.masterCheckInterval / 1000) {
            //master hasn't checked in for too long. assume it's gone.
            this.shared.maybePromoteToMaster();
          }
        }, this), this.shared.masterCheckInterval);
      }
    }
    else {
      if(!this.transport) {
        this.initializeTransport();
      }
      this.transport.listen(this.url, this.lastMessageId);
      this.running = true;
      delete this.starting;
    }
    return this;
  };

  NchanSubscriber.prototype.stop = function() {
    if(!this.running)
      throw "Can't stop NchanSubscriber, it's not running.";
    
    this.running = false;
    if(storageEventListener) {
      global.removeEventListener("storage", storageEventListener);
    }
    this.transport.cancel();
    if(this.shared) {
      delete sharedSubscriberTable[this.url];
      if(this.shared.masterIntervalCheckID) {
        clearInterval(this.shared.masterIntervalCheckID);
        delete this.shared.masterIntervalCheckID;
      }
    }
    return this;
  };

  function addLastMsgIdToQueryString(url, msgid) {
    if(msgid) {
      var m = url.match(/(\?.*)$/);
      url += (m ? "&" : "?") + "last_event_id=" + encodeURIComponent(msgid);
    }
    return url;
  }

  NchanSubscriber.prototype.SubscriberClass = {
    "websocket": (function() {
      function WSWrapper(emit) {
        WebSocket;
        this.emit = emit;
      }
      
      WSWrapper.prototype.websocketizeURL = function(url) {
        var m = url.match(/^((\w+:)?\/\/([^/]+))?(\/)?(.*)/);
        var protocol = m[2];
        var host = m[3];
        var absolute = m[4];
        var path = m[5];
        
        var loc;
        if(typeof window == "object") {
          loc = window.location;
        }
        else if(typeof document == "object") {
          loc = document.location;
        }
        
        if(!protocol && loc) {
          protocol = loc.protocol;
        }
        if(protocol == "https:") {
          protocol = "wss:";
        }
        else if(protocol == "http:") {
          protocol = "ws:";
        }
        else {
          protocol = "wss:"; //default setting: secure
        }
        
        if(!host && loc) {
          host = loc.host;
        }
        
        if(!absolute) {
          path = loc ? loc.pathname.match(/(.*\/)[^/]*/)[1] + path : "/" + path;
        }
        else {
          path = "/" + path;
        }
        
        return protocol + "//" + host + path;
      };
      
      WSWrapper.prototype.listen = function(url, msgid) {
        url = this.websocketizeURL(url);
        url = addLastMsgIdToQueryString(url, msgid);
        //console.log(url);
        if(this.listener) {
          throw "websocket already listening";
        }
        this.listener = new WebSocket(url, "ws+meta.nchan");
        var l = this.listener;
        l.onmessage = ughbind(function(evt) {
          var m = evt.data.match(/^id: (.*)\n(content-type: (.*)\n)?\n/m);
          this.emit("message", evt.data.substr(m[0].length), {"id": m[1], "content-type": m[3]});
        }, this);
        
        l.onopen = ughbind(function(evt) {
          this.emit("connect", evt);
          //console.log("connect", evt);
        }, this);
        
        l.onerror = ughbind(function(evt) {
          //console.log("error", evt);
          this.emit("error", evt, l);
          delete this.listener;
        }, this);
        
        l.onclose = ughbind(function(evt) {
          this.emit("__disconnect", evt);
          delete this.listener;
        }, this);
      };
      
      WSWrapper.prototype.cancel = function() {
        if(this.listener) {
          this.listener.close();
          delete this.listener;
        }
      };
      
      return WSWrapper;
    })(),
  
    "eventsource": (function() {
      function ESWrapper(emit) {
        EventSource;
        this.emit = emit;
      }
      
      ESWrapper.prototype.listen= function(url, msgid) {
        url = addLastMsgIdToQueryString(url, msgid);
        if(this.listener) {
          throw "there's a ES listener running already";
        }
        this.listener = new EventSource(url);
        var l = this.listener;
        l.onmessage = ughbind(function(evt){
          //console.log("message", evt);
          this.emit("message", evt.data, {id: evt.lastEventId});
        }, this);
        
        l.onopen = ughbind(function(evt) {
          this.reconnecting = false;
          //console.log("connect", evt);
          this.emit("connect", evt);
        }, this);
        
        l.onerror = ughbind(function(evt) {
          //EventSource will try to reconnect by itself
          //console.log("onerror", this.listener.readyState, evt);
          if(this.listener.readyState == EventSource.CONNECTING && !this.reconnecting) {
            if(!this.reconnecting) {
              this.reconnecting = true;
              this.emit("__disconnect", evt);
            }
          }
          else {
            this.emit("__disconnect", evt);
            //console.log('other __disconnect', evt);
          }
        }, this);
      };
      
      ESWrapper.prototype.cancel= function() {
        if(this.listener) {
          this.listener.close();
          delete this.listener;
        }
      };
      
      return ESWrapper;
    })(),
    
    "longpoll": (function () {
      function Longpoll(emit) {
        this.headers = {};
        this.longPollStartTime = null;
        this.maxLongPollTime = 5*60*1000; //5 minutes
        this.emit = emit;
      }
      
      Longpoll.prototype.listen = function(url, msgid) {
        if(this.req) {
          throw "already listening";
        }
        if(url) { this.url=url; }
        var setHeader = ughbind(function(incoming, name) {
          if(incoming) { this.headers[name]= incoming; }
        }, this);
        
        if(msgid) {
          this.headers = {"Etag": msgid};
        }
        
        this.reqStartTime = new Date().getTime();
        
        var  requestCallback;
        requestCallback = ughbind(function (code, response_text, req) {
          setHeader(req.getResponseHeader("Last-Modified"), "If-Modified-Since");
          setHeader(req.getResponseHeader("Etag"), "If-None-Match");
          
          if(code >= 200 && code <= 210) {
            //legit reply
            var content_type = req.getResponseHeader("Content-Type");
            if (!this.parseMultipartMixedMessage(content_type, response_text, req)) {
              this.emit("message", response_text || "", {"content-type": content_type, "id": this.msgIdFromResponseHeaders(req)});
            }
            
            this.reqStartTime = new Date().getTime();
            this.req = nanoajax.ajax({url: this.url, headers: this.headers}, requestCallback);
          }
          else if((code == 0 && response_text == "Error" && req.readyState == 4) || (code === null && response_text != "Abort")) {
            //console.log("abort!!!");
            this.emit("__disconnect", code || 0, response_text);
            delete this.req;
          }
          else if(code !== null) {
            //HTTP error
            this.emit("error", code, response_text);
            delete this.req;
          }
          else {
            //don't care about abortions 
            delete this.req;
            this.emit("__disconnect");
            //console.log("abort!");
          }
        }, this);
        
        this.reqStartTime = new Date().getTime();
        this.req = nanoajax.ajax({url: this.url, headers: this.headers}, requestCallback);
        this.emit("connect");
        
        return this;
      };
      
      Longpoll.prototype.parseMultipartMixedMessage = function(content_type, text, req) {
        var m = content_type && content_type.match(/^multipart\/mixed;\s+boundary=(.*)$/);
        if(!m) { 
          return false;
        }
        var boundary = m[1];
        
        var msgs = text.split("--" + boundary);
        if(msgs[0] != "" || !msgs[msgs.length-1].match(/--\r?\n/)) { throw "weird multipart/mixed split"; }
        
        msgs = msgs.slice(1, -1);
        for(var i in msgs) {
          m = msgs[i].match(/^(.*)\r?\n\r?\n([\s\S]*)\r?\n$/m);
          var hdrs = m[1].split("\n");
          
          var meta = {};
          for(var j in hdrs) {
            var hdr = hdrs[j].match(/^([^:]+):\s+(.*)/);
            if(hdr && hdr[1] == "Content-Type") {
              meta["content-type"] = hdr[2];
            }
          }
          
          if(i == msgs.length - 1) {
            meta["id"] = this.msgIdFromResponseHeaders(req);
          }
          this.emit("message", m[2], meta);
        }
        return true;
      };
      
      Longpoll.prototype.msgIdFromResponseHeaders = function(req) {
        var lastModified, etag;
        lastModified = req.getResponseHeader("Last-Modified");
        etag = req.getResponseHeader("Etag");
        if(lastModified) {
          return "" + Date.parse(lastModified)/1000 + ":" + (etag || "0");
        }
        else if(etag) {
          return etag;
        }
        else {
          return null;
        }
      };
      
      Longpoll.prototype.cancel = function() {
        if(this.req) {
          this.req.abort();
          delete this.req;
        }
        return this; 
      };
      
      return Longpoll;
    })(),
    
    "__slave": (function() {
      function LocalStoreSlaveTransport(emit) {
        this.emit = emit;
        this.doNotReconnect = true;
      }
      
      LocalStoreSlaveTransport.prototype.listen = function(url, shared) {
        this.shared = shared;
        this.statusChangeChecker = ughbind(function(ev) {
          if(this.shared.matchEventKey(ev, "msg")) {
            var msgId = this.shared.get("msg:id");
            var contentType = this.shared.get("msg:content-type");
            var msg = this.shared.get("msg");
            this.emit("message", msg, {"id": msgId == "" ? undefined : msgId, "content-type": contentType == "" ? undefined : contentType});
          }
        }, this);
        global.addEventListener("storage", this.statusChangeChecker);
      };
        
      LocalStoreSlaveTransport.prototype.cancel = function() {
        global.removeEventListener("storage", this.statusChangeChecker);
      };
      
      return LocalStoreSlaveTransport;
    })()

  };

  return NchanSubscriber;
});