/*

	DOMLoader : 0.2 : mudcu.be
	---------------------------
	DOMLoader.script.add({
		strictOrder: true,
		srcs: [
			{
				src: "../js/jszip/jszip.js",
				verify: "JSZip",
				callback: function() {
					console.log(1)
				}
			},
			{ 
				src: "../inc/downloadify/js/swfobject.js",
				verify: "swfobject",
				callback: function() {
					console.log(2)
				}
			}
		],
		callback: function() {
			console.log(3)
		}
	});
	
*/

if (typeof(DOMLoader) === "undefined") DOMLoader = {};

DOMLoader.script = function() {
	this.loaded = {};
	this.loading = {};
	return this;
};

DOMLoader.script.prototype.add = function(config) {
	var that = this;
	var srcs = config.srcs;
	if (typeof(srcs) === "undefined") {
		srcs = [{ 
			src: config.src, 
			verify: config.verify
		}];
	}
	/// adding the elements to the head
	var doc = document.getElementsByTagName("head")[0];
	/// 
	var testElement = function(element, test) {
		if (that.loaded[element.src]) return;
		if (test && !eval(test)) return;
		that.loaded[element.src] = true;
		//
		if (that.loading[element.src]) that.loading[element.src]();
		delete that.loading[element.src];
		//
		if (element.callback) element.callback();
		if (typeof(getNext) !== "undefined") getNext();
	};
	///
	var batchTest = [];
	var addElement = function(element) {
		if (/([\w\d.\[\]])$/.test(element.verify)) { // check whether its a variable reference
			element.test = "(typeof(" + element.verify + ") !== \"undefined\")";
			batchTest.push(element.test);
		}
		var script = document.createElement("script");
		script.onreadystatechange = function() {
			if (this.readyState !== "loaded" && this.readyState !== "complete") return;
			testElement(element);
		};
		script.onload = function() {
			testElement(element);
		};
		script.setAttribute("type", "text/javascript");
		script.setAttribute("src", element.src);
		doc.appendChild(script);
		that.loading[element.src] = function() {};
	};
	/// checking to see whether everything loaded properly
	var onLoad = function(element) {
		if (element) {
			testElement(element, element.test);
		} else {
			for (var n = 0; n < srcs.length; n ++) {
				testElement(srcs[n], srcs[n].test);
			}
		}
		if (!config.strictOrder && eval(batchTest.join(" && "))) { // finished loading all the requested scripts
			if (config.callback) config.callback();
		} else { // keep calling back the function
			setTimeout(function() { //- should get slower over time?
				onLoad(element);
			}, 10);
		}
	};
	/// loading methods;  strict ordering or loose ordering
	if (config.strictOrder) {
		var ID = -1;
		var getNext = function() {
			ID ++;
			if (!srcs[ID]) { // all elements are loaded
				if (config.callback) config.callback();
			} else { // loading new script
				var element = srcs[ID];
				var src = element.src;
				if (that.loading[src]) { // already loading from another call (attach to event)
					that.loading[src] = function() {
						if (element.callback) element.callback();
						getNext();
					}
				} else if (!that.loaded[src]) { // create script element
					addElement(element);
					onLoad(element);
				} else { // it's already been successfully loaded
					getNext();
				}
			}
		};
		getNext();
	} else { // loose ordering
		for (var ID = 0; ID < srcs.length; ID ++) {
			if (that.loaded[srcs[ID].src]) return;
			addElement(srcs[ID]);
		}
		onLoad();
	}
};

DOMLoader.script = (new DOMLoader.script());