/*
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,notify)
{
  this.req=null;
  this.onload=onload;
  this.url = url;
  this.notify = notify;
  this.onerror=(onerror) ? onerror : this.defaultError;
  this.loadXMLDoc(url,method,params,contentType);
}

net.ContentLoader.prototype={
  loadXMLDoc:function(url,method,params,contentType)
  {
    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");
    }
    else
    {
      this.req=new ActiveXObject("Microsoft.XMLHTTP");
    }
    if (this.req){
      try{
        var loader=this;
        this.req.onreadystatechange=function(){
          loader.onReadyState.call(loader);
        }
        this.req.open(method,url,true);
        if (contentType){
          this.req.setRequestHeader('Content-Type', contentType);
        }
        this.req.send(params);
      }catch (err){
        this.onerror.call(this);
      }
    }
  },

  onReadyState:function(){
    var req=this.req;
    var ready=req.readyState;
    if (ready==net.READY_STATE_COMPLETE)
    {
      var httpStatus=req.status;
      if (httpStatus==200 || httpStatus==0)
      {
        this.onload.call(this);
       // alert(this.notify);
        if (this.notify != null)
        {
         // alert("notify called");
          this.notify.call(this);
        }
      }
      else
      {
        this.onerror.call(this);
      }
    }
  },

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



/*--- 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();
      }
    }
  },

  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
      );
  },

  isCommand:function(obj){
    return (
      obj.implementsProp("id")
      && obj.implementsProp("priority")
      && obj.implementsFunc("toRequestString")
      && obj.implementsFunc("parseResponse")
      );
  },

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

  unrepeat:function(){
    if (this.repeater){
      clearInterval(this.repeater);
    }
    this.repeater=null;
  }
}

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.nodeName=="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.nodeName=="update"){
        if (this.implementsFunc("onUpdate")){
          this.onUpdate.call(this,elChild);
        }
      }
    }
  }
}

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