WebTools = {};

/**
* @param String method
* @param String URL
* @param String postData
* @param Function(responseData) onSuccess
* @param Function(Integer HTTPStatusCode, String responseData) onSuccess
* @return void
*/
WebTools.requestURL = function(method, URL, postData, onSuccess, onFail)
{
	var XHR = new XMLHttpRequest();
	XHR.open(method, URL, true);
	XHR.setRequestHeader("Content-type", "application/x-www-form-urlencoded; charset=UTF-8");
	XHR.setRequestHeader("Pragma", "no-cache");
	XHR.setRequestHeader("Cache-Control", "no-cache");
	XHR.onreadystatechange = function(){
		if(XHR.status == 0)
			return onFail(XHR.status);
		if(XHR.readyState == 4)
			if(XHR.status == 200)
				onSuccess(XHR.responseText);
			else
				onFail(XHR.status, XHR.responseText);
	};
	XHR.send(postData);
};

WebTools.parseDocument = function(HTMLString)
{
	return new DOMParser().parseFromString(HTMLString, "text/html");
};



var ZachSite = function(elementContent){
	var THIS = this;
	THIS.elementContent = elementContent;
	window.addEventListener("popstate", function(ev){
		THIS.loadSitePage(location.href);
	});
};

ZachSite.prototype.registerLink = function(elmAnchor){
	var THIS = this;

	if(!elmAnchor instanceof HTMLAnchorElement)
		throw new TypeError("Only HTMLAnchorElements");

	elmAnchor.addEventListener("click", function(ev){
		ev.preventDefault();
		history.pushState({zachSiteURLRequest: true}, this.textContent, this.href);
		THIS.loadSitePage(this.href);
	});
};

ZachSite.prototype.loadSitePage = function(URL)
{
	var THIS = this;
	var onSuccess = function(responseData)
	{
		var newDocument = WebTools.parseDocument(responseData);
		var newContent = newDocument.getElementById("content");
		// removes old #content contents
		while(THIS.elementContent.firstChild)
			THIS.elementContent.removeChild(THIS.elementContent.firstChild);
		// appends new #content contents
		while(newContent.firstChild)
			THIS.elementContent.appendChild(newContent.firstChild);
		// updates the title
		document.title = newDocument.title;
	};

	var onFail = function(httpstatus, data){
		alert("Page request returned an error: " + httpstatus + "\n " + data);
	};

	WebTools.requestURL("GET", URL, null, onSuccess, onFail);
		document.title = "@@@@@ LOADING!!! @@@@@"; // you can show a loading gif here (and hide it inside onSuccess|onFail())
	};


var site = new ZachSite(document.getElementById("content"));
var siteLinks = document.getElementsByTagName("a");
for(var x=0; x<siteLinks.length; x++)
	site.registerLink(siteLinks[x]);