/*
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,oTarget,oElem){
  this.req=null;
  this.oTarget=oTarget;
  this.oElem=oElem;
  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 (!method){
    method="GET";
  }
  if (!contentType && method=="POST"){
    contentType='application/x-www-form-urlencoded';
  }
  if (window.XMLHttpRequest){
    this.req = new XMLHttpRequest();
  } else if(window.ActiveXObject){
	var MSXML = ['MSXML2.XMLHTTP.5.0', 'MSXML2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP', 'Microsoft.XMLHTTP'];
	for(var n = 0; n < MSXML.length; n ++)
	{
		try
		{
			this.req = new ActiveXObject(MSXML[n]);
			break;
		}
		catch(e)
		{
		}
	}
  }
  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.send(params);
    }catch (err){
      this.onerror.call(this);
    }
  }
}


net.ContentLoader.onReadyState=function(){
  var clb=this.oTarget;
  var req=this.req;
  var ready=req.readyState;
  if (ready==net.READY_STATE_COMPLETE){
    var httpStatus=req.status;
    if (httpStatus==200 || httpStatus==0){
	  if(clb) clb.style.color='';
      this.onload.call(this);
    }else{
      this.onerror.call(this);
    }
  }
  else
  {
	if(clb)
	{
	clb.options.length = 0;
	clb.style.color='#666666';
	var option = new Option('请稍候..','0');
	clb.options.add(option,clb.options.length);
	}
  }
}

net.ContentLoader.prototype.defaultError=function(){
	var clb=this.oTarget;
	if(clb)
	{
	clb.options.length = 0;
	this.oElem.value='0';
	clb.style.color='#666666';
	var option = new Option('链接超时请重试!','0');
	clb.options.add(option,clb.options.length);
	}
  	/*alert("网络链接超时,请重试!"
    +"\n\nreadyState:"+this.req.readyState
    +"\nstatus: "+this.req.status
    +"\nheaders: "+this.req.getAllResponseHeaders());*/
}