// JavaScript Document

/**
 * This script adds background-position-x and background-position-y Css properties to jQuery.
 * Because FireFox fails to support these natively.
 * 
 * Usage:
 * 
 * this.$element.css
 *	({
 *		"background_position_x": 'left',
 *		"background_position_y": 'top'
 *	})
 * 
 * Copyright (c) 2011 Nikolay Kuchumov
 * Licensed under MIT (http://en.wikipedia.org/wiki/MIT_License)
 * 
 * @author Kuchumov Nikolay
 * @email kuchumovn@gmail.com
 * @github kuchumovn
 */

(function($)
{
	function get_background_position($element)
	{
		var position = $element.css('background-position')
			
		if (!position)
			position = 'auto'
			
		return position
	}
	
	function get_coordinates(position)
	{
		var coordinates = position.split(' ')
		
		if (coordinates.length != 2)
			return
				
		return coordinates	
	}
	
	function get_position(coordinates)
	{
		return coordinates.join(' ')
	}
	
	function get_coordinate(index, $element)
	{
		var position = get_background_position($element)
			
		if (position === 'auto')
		{
			return 'auto'
		}
			
		var coordinates = get_coordinates(position)
		
		if (!coordinates)
			return

		return coordinates[index - 1]
	}
	
	$.cssHooks['background_position_x'] = 
	{
		get: function(element, computed, extra) 
		{
			var x = get_coordinate(1, $element)
			
			if (!x)
				return
				
			return x
		},
		
		set: function(element, x) 
		{
			var $element = $(element)
			
			var y = get_coordinate(2, $element)
			
			if (!y)
				return
				
			$element.css('background-position', get_position([x, y]))
		}
	}
		
	$.cssHooks['background_position_y'] = 
	{
		get: function(element, computed, extra) 
		{
			var y = get_coordinate(2, $element)
			
			if (!y)
				return
		},
		
		set: function(element, y) 
		{
			var $element = $(element)
			
			var x = get_coordinate(1, $element)
			
			if (!x)
				return
				
			$element.css('background-position', get_position([x, y]))
		}
	}
	
	$.fx.step['background_position_x']  = function(fx) 
	{
		$.cssHooks['background_position_x'].set(fx.elem, fx.now + fx.unit);
	}

	$.fx.step['background_position_y']  = function(fx) 
	{
		$.cssHooks['background_position_y'].set(fx.elem, fx.now + fx.unit);
	}
})
(jQuery)