var xparser = {};

xparser.feedType = {
	rss : 1,
	atom : 2
};

xparser.FeezdNode = function (oNode) {
	this.value = (oNode && (oNode.text || oNode.getText())) || null;
};

xparser.BaseFeed = function (iFeedType, fpCallBack, oCallBackScope ) {
	this.type = iFeedType || null;
	this.title = null;
	this.link = null;
	this.description = null;
	this.copyright = null;
	this.generator = null;
	this.modified = null;
	this.author = null;
	this.items = [];
	this.callBack = (typeof fpCallBack == "function") ? fpCallBack : function () {};
	this.callBackScope = (typeof oCallBackScope == "object") ? oCallBackScope : this;
};

xparser.BaseFeed.prototype = {
	parse : function (oContextNode, oElements, oNamespaces) {
		//Loop through the keys
		for (var sProperty in oElements) {
			if (oElement.hasOwnProperty(sProperty)) {
				//Create FeedNode objects with the node
				//returned from the XPath evaluation
				this[sProperty] = new xparser.FeedNode( zXPath.selectSingleNode(
												oContextNode,
												oElements[sProperty],
												oNamespaces )
				);
			}
		}
	}
};

xparser.BaseItem = function () {
	this.title = null;
	this.author = null;
	this.link = null;
	this.description = null;
	this.date = null;
};

xparser.BaseItem.prototype = {
	parse : function (oContextNode, oElements, oNamespaces ) {
		//Loop through the keys
		for (var sProperty in oElements) {
			if (oElements.hasOwnProperty(sProperty)) {
				//Create FeedNode objects with the node
				//returned from the XPath evaluation
				this[sProperty] = new xparser.FeedNode(
									zXPath.selectSingleNode(
										oContextNode,
										oElements[sProperty],
										oNamespaces )
				);
			}
		}
	}
};

xparser.RssFeed = function (oRootNode, fpCallBack, oCallBackScope) {
	xparser.BaseFeed.apply(this, [xparser.feedType.rss, fpCallBack, oCallBackScope]);
	
	var oChannelNode = zXPath.selectSingleNode(oRootNode, "channel");
	var oElements = {
		title : "title",
		link : "link",
		description : "description",
		copyright : "copyright",
		generator : "generator",
		modified : "lastbuilddate",
		author : "managingeditor"
	};
	this.parse(oChannelNode, oElements, []);
	
	var cItems = zXPath.selectNodes(oChannelNode, "item");
	for (var i = 0, oItem; oItem = cItems[i]; i++) {
		this.items.push(new xparser.RssItem(oItem));
	}
	this.callBack.call(this.callBackScope, this);
};

xparser.RssFeed.prototype = new xparser.BaseFeed();

xparser.RssItem = function (oItemNode) {
	xparser.BaseItem.apply(this);
	var oElements = {
		title : "title",
		link : "link",
		description : "description",
		date : "pubdate",
		author : "author"
	};
	this.parse(oItemNode, oElements, {});
};

xparser.RssItem.prototype = new xparser.BaseItem();

xparser.AtomFeed = function (oRootNode, fpCallBack, oCallBackScope) {
	xparser.BaseFeed.apply(this, [xparser.feedType.atom, fpCallBack, oCallBackScope] );
	var oNamespaces = {
		atom : oRootNode.namespaceURI
	};
	
	var oElements = {
		title : "atom:title",
		link : "atom:link/@href",
		description : "atom:tagline",
		copyright : "atom:copyright",
		generator : "atom:generator",
		modified : "atom:modified",
		author : "atom:author"
	};
	this.parse(oRootNode, oElements, oNamespaces);
	
	var cEntries = zXPath.selectNodes(oRootNode, "atom:entry", oNamespaces);
	for (var i = 0, oEntry; oEntry = cEntries[i]; i++) {
		this.items.push(new xparser.AtomItem(oEntry, oNamespaces));
	}
	this.callBack.apply(this.callBackScope, [this]);
};

xparser.AtomFeed.prototype = new xparser.BaseFeed();

xparser.AtomItem = function (oEntryNode, oNamespaces) {
	xparser.BaseItem.apply(this, []);
	var oElements = {
		title : "atom:title",
		link : "atom:link/@href",
		description : "atom:content",
		date : "atom:issued",
		author : "atom:author"
	};
	this.parse(oEntryNode, oElements, oNamespaces);
};

xparser.AtomItem.prototype = new xparser.BaseItem();

xparser.getFeed = function (sUrl, fpCallBack, oCallBackScope) {
	var oReq = zXmlHttp.createRequest();
	//alert(" create the XMLHttpRequest object.");
	oReq.onreadystatechange = function () {
		if (oReq.readyState == 4) {
			if (oReq.status == 200 || oReq.status == 304) {
			//more code here
				var oFeed = null;
				var oXmlDom = zXmlDom.createDocument();
				oXmlDom.loadXML(oReq.responseText);
				if (oXmlDom.parseError.errorCode != 0) {
					throw new Error("XParser Error: The requested feed is not " +
								"valid XML and could not be parsed.");
				} else {
					var oRootNode = oXmlDom.documentElement;
					//Get the name of the document element.
					var sRootName;
					if (oRootNode.nodeName.indexOf(":") > -1) //a prefix exists
						sRootName = oRootNode.nodeName.split(":")[1];
					else
						sRootName = oRootNode.nodeName;
						switch (sRootName.toLowerCase()) {
							case "feed": //It’s Atom.
								oFeed = new xparser.AtomFeed( oRootNode, fpCallBack, oCallBackScope);
								break;
							case "rss": //It’s RSS
								//Check the version.
								if (parseInt(oRootNode.getAttribute("version")) < 2)
									throw new Error("XParser Error! RSS feed " + "version is not supported" );
								oFeed = new xparser.RssFeed( oRootNode, fpCallBack, oCallBackScope );
								break;
							default: //The feed isn’t supported.
								throw new Error("XParser Error: The supplied feed " + "is currently not supported." );
								break;
						}
					}
				} 
			} else { //The HTTP Status code isn’t what we wanted; throw an error.
					throw new Error("XParser Error: XHR failed. " + "HTTP Status: " + oReq.status );
			}
		}
	oReq.open("GET", sUrl, true);
	oReq.send(null);
};