/*
---

script: Element.Pin.js

name: Element.Pin

description: Extends the Element native object to include the pin method useful for fixed positioning for elements.

license: MIT-style license

authors:
  - Aaron Newton

requires:
  - Core/Element.Event
  - Core/Element.Dimensions
  - Core/Element.Style
  - /MooTools.More

provides: [Element.Pin]

...
*/

(function(){
	var supportsPositionFixed = false,
		supportTested = false;

	var testPositionFixed = function(){
		var test = new Element('div').setStyles({
			position: 'fixed',
			top: 0,
			right: 0
		}).inject(document.body);
		supportsPositionFixed = (test.offsetTop === 0);
		test.dispose();
		supportTested = true;
	};

	Element.implement({

		pin: function(enable, forceScroll){
			if (!supportTested) testPositionFixed();
			if (this.getStyle('display') == 'none') return this;

			var pinnedPosition,
				scroll = window.getScroll(),
				parent,
				scrollFixer;

			if (enable !== false){
				pinnedPosition = this.getPosition(supportsPositionFixed ? document.body : this.getOffsetParent());
				if (!this.retrieve('pin:_pinned')){
					var currentPosition = {
						top: pinnedPosition.y - scroll.y,
						left: pinnedPosition.x - scroll.x
					};

					if (supportsPositionFixed && !forceScroll){
						this.setStyle('position', 'fixed').setStyles(currentPosition);
					} else {

						parent = this.getOffsetParent();
						var position = this.getPosition(parent),
							styles = this.getStyles('left', 'top');

						if (parent && styles.left == 'auto' || styles.top == 'auto') this.setPosition(position);
						if (this.getStyle('position') == 'static') this.setStyle('position', 'absolute');

						position = {
							x: styles.left.toInt() - scroll.x,
							y: styles.top.toInt() - scroll.y
						};

						scrollFixer = function(){
							if (!this.retrieve('pin:_pinned')) return;
							var scroll = window.getScroll();
							this.setStyles({
								left: position.x + scroll.x,
								top: position.y + scroll.y
							});
						}.bind(this);

						this.store('pin:_scrollFixer', scrollFixer);
						window.addEvent('scroll', scrollFixer);
					}
					this.store('pin:_pinned', true);
				}

			} else {
				if (!this.retrieve('pin:_pinned')) return this;

				parent = this.getParent();
				var offsetParent = (parent.getComputedStyle('position') != 'static' ? parent : parent.getOffsetParent());

				pinnedPosition = this.getPosition(offsetParent);

				this.store('pin:_pinned', false);
				scrollFixer = this.retrieve('pin:_scrollFixer');
				if (!scrollFixer){
					this.setStyles({
						position: 'absolute',
						top: pinnedPosition.y + scroll.y,
						left: pinnedPosition.x + scroll.x
					});
				} else {
					this.store('pin:_scrollFixer', null);
					window.removeEvent('scroll', scrollFixer);
				}
				this.removeClass('isPinned');
			}
			return this;
		},

		unpin: function(){
			return this.pin(false);
		},

		togglePin: function(){
			return this.pin(!this.retrieve('pin:_pinned'));
		}

	});

//<1.2compat>
Element.alias('togglepin', 'togglePin');
//</1.2compat>

})();