var isIE6 = navigator.userAgent.indexOf('MSIE 6') != -1;

/**************************************************************************
 * Useful Array methods
 *
 **************************************************************************/

Array.prototype.indexOf = function(e) {
	for (var i = 0; i < this.length; i++)
		if (this[i] == e)
			return i;
	return -1;
}

Array.prototype.contains = function(e) {
	return this.indexOf(e) != -1;
}

Array.prototype.remove = function(e) {
	var p = this.indexOf(e);
	if (p != -1) {
		for (; p < this.length - 1; p++)
			this[p] = this[p+1];
		delete this[p];
		this.length = p;
	}
	return this;
}

Array.prototype.add = function(e) {
	this[this.length] = e;
}


/**************************************************************************
 * Widget content methods: addContent, clearContent, setContent
 *
 **************************************************************************/

function addContent(element, content) {
	if (!content)
		return;
	var type = typeof(content);
	if (type == 'function')
		return;
	else if (content instanceof Array)
		for (var i = 0; i < content.length; i++)
			addContent(element, content[i]);
	else if (type != 'object')
		element.appendChild(document.createTextNode(content));
	else if (content.nodeName)
		element.appendChild(content);
	else
		copyProperties(element, content);
}

function clearContent(element) {
	while (element.hasChildNodes())
		element.removeChild(element.lastChild);
}

function setContent(element, content) {
	clearContent(element);
	addContent(element, content);
}

/**************************************************************************
 * element(name, { attributes | children })
 * creates element with name, attributes and children specified
 *
 **************************************************************************/
function element(name) {
	var e = document.createElement(name);
	for (var i = 1; i < arguments.length; i++) {
		var arg = arguments[i];
		if (!arg)
			continue;
		addContent(e, arguments[i]);
	}
	addContent(e, elementMethods);
	return e;
}

function copyProperties(to, from) {
	for (var p in from) {
		if (!to[p] || typeof(to[p]) != 'object' || typeof(from[p]) != 'object') {
			to[p] = from[p];
		} else {
			copyProperties(to[p], from[p]);
		}
	}
}

/**************************************************************************
 * Element class methods: add and remove class names from element class attribute
 *
 **************************************************************************/
var elementMethods = {
	addClass :  function(style) {
					if (!this.className || this.className.length == 0)
						this.className == style;
					else if (!this.className.split(/\s+/).contains(style))
						this.className += ' ' + style;
				},

	removeClass : function(style) {
					if (this.className && this.className.length > 0)
						this.className = this.className.split(/\s+/).remove(style).join(' ');
				  },

	show : function() { this.removeClass('hidden'); },
	
	hide : function() { this.addClass('hidden'); },
	
	left : function() {
				var left = 0;
				var e = this;
				while (e) {
					left += e.offsetLeft;
					e = e.offsetParent;
				}
				return left;
			},
	
	top : function() {
				var top = 0;
				var e = this;
				while (e) {
					top += e.offsetTop;
					e = e.offsetParent;
				}
				return top;
			},
			
	right : function() { return this.left() + this.offsetWidth; },
			
	bottom : function() { return this.top() + this.offsetHeight; }
};


/**************************************************************************
 * positioned(x, y, z, widget)
 * absolutely positions widget at x, y, z
 *
 **************************************************************************/

function positioned(x, y, widget) {
	return element('div', 
					{ style : { position : 'absolute', 'left' : x + 'px', top : y + 'px' }},
					widget);
}


/**************************************************************************
 * multiStateImage({ srcPath })
 * 	an img tag which can change state using img.show(n) method
 *
 **************************************************************************/

function multiStateImage() {
	var attrs = { states : [],
				  setState : function(n) { this.src = this.states[n]; }
				};

	if (isIE6) {
		attrs.onreadystatechange = function() { fixPNG(this); };
		attrs.onload = attrs.onreadystatechange;
	}
	
	var img = element('img', attrs);
	
	for (var i = 0; i < arguments.length; i++)
		if (typeof(arguments[i]) == 'string')
			img.states[img.states.length] = arguments[i];
		else
			addContent(img, arguments[i]);
	img.setState(0);
	return img;
}

// Utility function which runs fn(item) on all items in list
function forAll(list, fn) {
	for (var i = 0; i < list.length; i++)
		fn(list[i]);
}

/**************************************************************************
 * singleActivated({ widget })
 * 
 *
 **************************************************************************/

function singleActivated() {
	var elements = [];
	for (var i = 0; i < arguments.length; i++) {
		elements[i] = arguments[i];
		elements[i].deactivateableSiblings = elements;
		elements[i]._originalActivate = elements[i].activate;
		elements[i].activate = function() {
						forAll(this.deactivateableSiblings, function(e) { e.deactivate(); });
						this._originalActivate(); 
					};
	}
	return elements;
}

function remainingArgs(a, n) {
	var result = new Array();
	var j = 0;
	for (var i = n; i < a.length; i++) {
		result[j++] = a[i];
	}
	return result;
}

function image(src) {
	var attrs = { src : src };
	if (isIE6 && src.indexOf('.png') != -1)
		attrs.onload = attrs.onreadystatechange = function() { fixPNG(this); };
	return element('img', attrs, remainingArgs(arguments, 1));
}

function link(href) {
	return element('a', href ? { href : href } : false, remainingArgs(arguments,1));
}