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

net.ContentLoader.prototype.loadXMLDoc=function(url,method,params,contentType,syn){
	if (!method){
		method="POST";
	}
	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");
	}
	if (this.req){
		try{
			var loader=this;
			this.req.onreadystatechange=function(){
				net.ContentLoader.onReadyState.call(loader);
			}
			this.req.open(method,url,false);	// syn:synchronous
			if (contentType){
				this.req.setRequestHeader('Content-Type', contentType);
			}
			this.req.send(params);
		}catch (err){
			this.onerror.call(this);
		}
	}
}


net.ContentLoader.onReadyState=function(){
	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;
}