// http://www.dustindiaz.com/rock-solid-addevent/
function addEvent( obj, type, fn ) {
  if (obj.addEventListener) {
  obj.addEventListener( type, fn, false );
  EventCache.add(obj, type, fn);
  }
  else if (obj.attachEvent) {
  obj["e"+type+fn] = fn;
  obj[type+fn] = function() { obj["e"+type+fn]( window.event ); }
  obj.attachEvent( "on"+type, obj[type+fn] );
  EventCache.add(obj, type, fn);
  }
  else {
  obj["on"+type] = obj["e"+type+fn];
  }
}

var EventCache = function(){
  var listEvents = [];
  return {
  listEvents : listEvents,
  add : function(node, sEventName, fHandler){
    listEvents.push(arguments);
  },
  flush : function(){
    var i, item;
    for(i = listEvents.length - 1; i >= 0; i = i - 1){
    item = listEvents[i];
    if(item[0].removeEventListener){
      item[0].removeEventListener(item[1], item[2], item[3]);
    };
    if(item[1].substring(0, 2) != "on"){
      item[1] = "on" + item[1];
    };
    if(item[0].detachEvent){
      item[0].detachEvent(item[1], item[2]);
    };
    item[0][item[1]] = null;
    };
  }
  };
}();
addEvent(window,'unload',EventCache.flush);

function RemoveElements( el ) {
  for (var i=el.childNodes.length-1; i>=0; i=i-1) {
// can cause stack overflow error or take forever to remove elements on large select / option objects
//  if (!el.childNodes[i].leaf) this.RemoveElements( el.childNodes[i] )
  el.removeChild( el.childNodes[i] );
  }
}

// url-loading object and a request queue built on top of it
// namespacing object
var net = new Object();

net.READY_STATE_UNINITIALIZED = 0;
net.READY_STATE_LOADING = 1;
net.READY_STATE_LOADED = 2;
net.READY_STATE_INTERACTIVE = 3;
net.READY_STATE_COMPLETE = 4;

/*--- content loader object for cross-browser requests ---*/
net.ContentLoader = function(url, onload, onerror, method, params, contentType) {
  this.req = null;
  net.currentLoader = this;
  this.onload = onload;
  this.onerror = (onerror) ? onerror : this.defaultError;
  this.loadXMLDoc(url, method, params, contentType);
}

net.ContentLoader.prototype.loadXMLDoc = function(url, method, params, contentType) {
//  if (window.netscape && window.netscape.security.PrivilegeManager.enablePrivilege) netscape.security.PrivilegeManager.enablePrivilege('UniversalBrowserRead');
  if (!method) method = 'GET';
  if (!contentType && method == 'POST') contentType = 'application/x-www-form-urlencoded';
//  if (window.XMLHttpRequest) this.req = new XMLHttpRequest();
//  else if (window.ActiveXObject) this.req = new ActiveXObject('Microsoft.XMLHTTP');
// Allen code to determine which browser and make the AJAX request
	try { this.req = new ActiveXObject( 'Msxml2.XMLHTTP' ); }
	catch( e ) {
	  try { this.req = new ActiveXObject( 'Microsoft.XMLHTTP' ); }
	  catch( e ) { this.req = false; }
	}
	if( !this.req && typeof XMLHttpRequest != 'undefined' ) {
		try { this.req = new XMLHttpRequest(); }
		catch( e ) { this.req = false; }
	}
	if( !this.req && window.createRequest ) {
		try { this.req = window.createRequest(); }
		catch( e ) { this.req = false; }
	}

  if( this.req ) {
    try {
      var loader = this;
      this.req.onreadystatechange = function() { net.ContentLoader.onReadyState.call(loader); }
      this.req.open(method, url, true);
      if (contentType) this.req.setRequestHeader('Content-Type', contentType);
//	  	this.req.setRequestHeader('Content-Type','text/html');
      this.req.send(params);
    } catch (err) { this.onerror.call(this); }
  }
}

net.ContentLoader.onReadyState = function() {
//  if (window.netscape && window.netscape.security.PrivilegeManager.enablePrivilege) netscape.security.PrivilegeManager.enablePrivilege('UniversalBrowserRead');
  var req = this.req;
  var ready = req.readyState;
  if (ready == net.READY_STATE_COMPLETE) {
    var httpStatus = req.status;
    //if (status==200 || httpStatus==0){
    if (httpStatus == 200 || httpStatus == 0) this.onload.call(this);
    else this.onerror.call(this);
  }
}

net.ContentLoader.prototype.defaultError = function() {
  alert("error fetching data!"
    + "\n\nreadyState:" + this.req.readyState
    + "\nstatus: " + this.req.status
    + "\nheaders: " + this.req.getAllResponseHeaders());
}

/*--- queue system for efficient transfer of many small commands in a single request ---*/
net.cmdQueues = new Array();

net.CommandQueue = function(id, url, onUpdate, freq) {
  this.id = id;
  net.cmdQueues[id] = this;
  this.url = url;
  this.queued = new Array();
  this.sent = new Array();
  this.onUpdate = onUpdate;
  if (freq) this.repeat(freq);
  this.lastUpdateTime = 0;
}

net.CommandQueue.STATUS_QUEUED = -1;
net.CommandQueue.STATE_UNINITIALIZED = net.READY_STATE_UNINITIALIZED;
net.CommandQueue.STATE_LOADING = net.READY_STATE_LOADING;
net.CommandQueue.STATE_LOADED = net.READY_STATE_LOADED;
net.CommandQueue.STATE_INTERACTIVE = net.READY_STATE_INTERACTIVE;
net.CommandQueue.STATE_COMPLETE = net.READY_STATE_COMPLETE;
net.CommandQueue.STATE_PROCESSED = 5;
net.CommandQueue.PRIORITY_NORMAL = 0;
net.CommandQueue.PRIORITY_IMMEDIATE = 1;

net.CommandQueue.prototype.addCommand = function(command) {
  if (this.isCommand(command)) {
    this.queue.append(command, true);
    if (command.priority == net.CommandQueue.PRIORITY_IMMEDIATE) this.fireRequest();
  }
}

net.CommandQueue.prototype.fireRequest = function() {
  if (!this.onUpdate && this.queued.length == 0) return;
  var data = "lastUpdate=" + this.lastUpdateTime + "&data=";
  for (var i = 0; i < this.queued.length; i++) {
    var cmd = this.queued[i];
    if (this.isCommand(cmd)) {
      data += cmd.toRequestString();
      this.sent[cmd.id] = cmd;
    }
  }
  this.queued = new Array();
  this.loader = new net.ContentLoader(
    this.url,
    net.CommandQueue.onload,
    net.CommandQueue.onerror,
    "POST", data
    );
}

net.CommandQueue.prototype.isCommand = function(obj) {
  return (
    obj.implementsProp("id")
      && obj.implementsProp("priority")
      && obj.implementsFunc("toRequestString")
      && obj.implementsFunc("parseResponse")
    );
}

net.CommandQueue.onload = function() {
  var xmlDoc = this.req.responseXML;
  var elDocRoot = xmlDoc.getElementsByTagName("responses")[0];
  var lastUpdate = elDocRoot.attributes.getNamedItem("updateTime");
  if (parseInt(lastUpdate) > this.lastUpdateTime) this.lastUpdateTime = lastUpdate;
  if (elDocRoot) {
    for (i = 0; i < elDocRoot.childNodes.length; i++) {
      elChild = elDocRoot.childNodes[i];
      if (elChild.nodeType == 1) {
        if (elChild.tagName == "command") {
          var attrs = elChild.attributes;
          var id = attrs.getNamedItem("id").value;
          var command = net.commandQueue.sent[id];
          if (command) command.parseResponse(elChild);
        } else if (elChild.tagName == "update") {
          if (this.implementsFunc("onUpdate")) this.onUpdate.call(this, elChild);
        }
      }
    }
  }
}

net.CommandQueue.onerror = function() {
  alert("problem sending the data to the server");
}

net.CommandQueue.prototype.repeat = function(freq) {
  this.unrepeat();
  if (freq > 0) {
    this.freq = freq;
    var cmd = "net.cmdQueues[" + this.id + "].fireRequest()";
    this.repeater = setInterval(cmd, freq * 1000);
  }
}
net.CommandQueue.prototype.unrepeat = function() {
  if (this.repeater) clearInterval(this.repeater);
  this.repeater = null;
}