var GUI = new function() {

	var _this = this;
	
	var controllers = [];

	this.add = function() {
	
		// We need to call GUI.start() before .add()
		if (!started) {
			error("Make sure to call GUI.start() in the window.onload function");
			return;
		}
	
		var object = arguments[0];
		var propertyName = arguments[1];
	
		// Have we already added this?
		if (alreadyControlled(object, propertyName)) {
			error("Controller for \"" + propertyName+"\" already added.");
			return;
		}
	
		var value = object[propertyName];
		
		// Does this value exist? Is it accessible?
		if (value == undefined) {
			error(object + " either has no property \""+propertyName+"\", or the property is inaccessible.");
			return;
		}
		
		var type = typeof value;
		var handler = addHandlers[type];
		
		// Do we know how to deal with this data type?
		if (handler == undefined) {
			error("Cannot create controller for data type \""+type+"\"");
			return;
		}
	
		var controllerObject = handler.apply(this, arguments);
		
		// Were we able to make the controller?
		if (!controllerObject) {		
			error("Error creating controller for \""+propertyName+"\".");	
			return;
		}
		
		// Success.
		controllerContainer.appendChild(controllerObject.domElement);
		controllers.push(controllerObject);
		
		return controllerObject;
		
	}
	
	var addHandlers = {
		
		"number": function() {
            return construct(NumberController, arguments);
		},
		
		"string": function() {
            return construct(StringController, arguments);
		},
		
		"boolean": function() {
			return construct(BooleanController, arguments);
		},
		
		"function": function() {
			return construct(FunctionController, arguments);
		},
		
	};
	
	var alreadyControlled = function(object, propertyName) {
		for (var i in controllers) {
			if (controllers[i].object == object &&
				controllers[i].propertyName == propertyName) {
				return true;
			}
		}
		return false;
	};
	
	var error = function(str) {
		if (typeof console.log == 'function') {
			console.error("[GUI ERROR] " + str);
		}
	};
	
	var construct = function(constructor, args) {
        function F() {
            return constructor.apply(this, args);
        }
        F.prototype = constructor.prototype;
        return new F();
    };



	// GUI ... GUI
	
	var domElement;
	var controllerContainer;
	var started = false;
	var open = false;
	
	// TODO: obtain this dynamically?
	var domElementMarginTop = 300;
	
	this.start = function() {
		
		domElement = document.createElement('div');
		domElement.setAttribute('id', 'guidat');
		
		controllerContainer = document.createElement('div');
		controllerContainer.setAttribute('id', 'guidat-controllers');
		
		toggleButton = document.createElement('a');
		toggleButton.setAttribute('id', 'guidat-toggle');
		toggleButton.setAttribute('href', '#');
		toggleButton.innerHTML = "Show Controls";
		toggleButton.addEventListener('click', function(e) {
			_this.toggle();
			e.preventDefault();
		}, false);
		
		domElement.appendChild(controllerContainer);
		domElement.appendChild(toggleButton);
		
		domElement.style.marginTop = -domElementMarginTop+"px";
		
		document.body.appendChild(domElement);
		
		started = true;
		
	};
	
	this.toggle = function() {
		
		if (open) {
			this.hide();
		} else { 
			this.show();
		}
		
	};
	
	this.show = function() {
		domElement.style.marginTop = 0+"px";
		toggleButton.innerHTML = "Hide Controls";
		open = true;
	}
	
	this.hide = function() {
		domElement.style.marginTop = -domElementMarginTop+"px";
		toggleButton.innerHTML = "Show Controls";
		open = false;
	}
	
};