/*
---

script: Element.Position.js

description: Extends the Element native object to include methods useful positioning elements relative to others.

license: MIT-style license

authors:
- Aaron Newton

requires:
- core:1.2.4/Element.Dimensions
- /Element.Measure

provides: [Elements.Position]

...
*/

(function(){

var original = Element.prototype.position;

Element.implement({

	position: function(options){
		//call original position if the options are x/y values
		if (options && ($defined(options.x) || $defined(options.y))) return original ? original.apply(this, arguments) : this;
		$each(options||{}, function(v, k){ if (!$defined(v)) delete options[k]; });
		options = $merge({
			// minimum: { x: 0, y: 0 },
			// maximum: { x: 0, y: 0},
			relativeTo: document.body,
			position: {
				x: 'center', //left, center, right
				y: 'center' //top, center, bottom
			},
			edge: false,
			offset: {x: 0, y: 0},
			returnPos: false,
			relFixedPosition: false,
			ignoreMargins: false,
			ignoreScroll: false,
			allowNegative: false
		}, options);
		//compute the offset of the parent positioned element if this element is in one
		var parentOffset = {x: 0, y: 0}, 
				parentPositioned = false;
		/* dollar around getOffsetParent should not be necessary, but as it does not return
		 * a mootools extended element in IE, an error occurs on the call to expose. See:
		 * http://mootools.lighthouseapp.com/projects/2706/tickets/333-element-getoffsetparent-inconsistency-between-ie-and-other-browsers */
		var offsetParent = this.measure(function(){
			return document.id(this.getOffsetParent());
		});
		if (offsetParent && offsetParent != this.getDocument().body){
			parentOffset = offsetParent.measure(function(){
				return this.getPosition();
			});
			parentPositioned = offsetParent != document.id(options.relativeTo);
			options.offset.x = options.offset.x - parentOffset.x;
			options.offset.y = options.offset.y - parentOffset.y;
		}
		//upperRight, bottomRight, centerRight, upperLeft, bottomLeft, centerLeft
		//topRight, topLeft, centerTop, centerBottom, center
		var fixValue = function(option){
			if ($type(option) != 'string') return option;
			option = option.toLowerCase();
			var val = {};
			if (option.test('left')) val.x = 'left';
			else if (option.test('right')) val.x = 'right';
			else val.x = 'center';
			if (option.test('upper') || option.test('top')) val.y = 'top';
			else if (option.test('bottom')) val.y = 'bottom';
			else val.y = 'center';
			return val;
		};
		options.edge = fixValue(options.edge);
		options.position = fixValue(options.position);
		if (!options.edge){
			if (options.position.x == 'center' && options.position.y == 'center') options.edge = {x:'center', y:'center'};
			else options.edge = {x:'left', y:'top'};
		}

		this.setStyle('position', 'absolute');
		var rel = document.id(options.relativeTo) || document.body,
				calc = rel == document.body ? window.getScroll() : rel.getPosition(),
				top = calc.y, left = calc.x;

		var dim = this.getDimensions({computeSize: true, styles:['padding', 'border','margin']});
		var pos = {},
				prefY = options.offset.y,
				prefX = options.offset.x,
				winSize = window.getSize();
		switch(options.position.x){
			case 'left':
				pos.x = left + prefX;
				break;
			case 'right':
				pos.x = left + prefX + rel.offsetWidth;
				break;
			default: //center
				pos.x = left + ((rel == document.body ? winSize.x : rel.offsetWidth)/2) + prefX;
				break;
		}
		switch(options.position.y){
			case 'top':
				pos.y = top + prefY;
				break;
			case 'bottom':
				pos.y = top + prefY + rel.offsetHeight;
				break;
			default: //center
				pos.y = top + ((rel == document.body ? winSize.y : rel.offsetHeight)/2) + prefY;
				break;
		}
		if (options.edge){
			var edgeOffset = {};

			switch(options.edge.x){
				case 'left':
					edgeOffset.x = 0;
					break;
				case 'right':
					edgeOffset.x = -dim.x-dim.computedRight-dim.computedLeft;
					break;
				default: //center
					edgeOffset.x = -(dim.totalWidth/2);
					break;
			}
			switch(options.edge.y){
				case 'top':
					edgeOffset.y = 0;
					break;
				case 'bottom':
					edgeOffset.y = -dim.y-dim.computedTop-dim.computedBottom;
					break;
				default: //center
					edgeOffset.y = -(dim.totalHeight/2);
					break;
			}
			pos.x += edgeOffset.x;
			pos.y += edgeOffset.y;
		}
		pos = {
			left: ((pos.x >= 0 || parentPositioned || options.allowNegative) ? pos.x : 0).toInt(),
			top: ((pos.y >= 0 || parentPositioned || options.allowNegative) ? pos.y : 0).toInt()
		};
		var xy = {left: 'x', top: 'y'};
		['minimum', 'maximum'].each(function(minmax) {
			['left', 'top'].each(function(lr) {
				var val = options[minmax] ? options[minmax][xy[lr]] : null;
				if (val != null && pos[lr] < val) pos[lr] = val;
			});
		});
		if (rel.getStyle('position') == 'fixed' || options.relFixedPosition){
			var winScroll = window.getScroll();
			pos.top+= winScroll.y;
			pos.left+= winScroll.x;
		}
		if (options.ignoreScroll) {
			var relScroll = rel.getScroll();
			pos.top-= relScroll.y;
			pos.left-= relScroll.x;
		}
		if (options.ignoreMargins) {
			pos.left += (
				options.edge.x == 'right' ? dim['margin-right'] : 
				options.edge.x == 'center' ? -dim['margin-left'] + ((dim['margin-right'] + dim['margin-left'])/2) : 
					- dim['margin-left']
			);
			pos.top += (
				options.edge.y == 'bottom' ? dim['margin-bottom'] : 
				options.edge.y == 'center' ? -dim['margin-top'] + ((dim['margin-bottom'] + dim['margin-top'])/2) : 
					- dim['margin-top']
			);
		}
		pos.left = Math.ceil(pos.left);
		pos.top = Math.ceil(pos.top);
		if (options.returnPos) return pos;
		else this.setStyles(pos);
		return this;
	}

});

})();