/*
 Plugin: jQuery Parallax
 Version 1.1
 Author: Ian Lunn
 Author URL: http://www.ianlunn.co.uk/
 Plugin URL: http://www.ianlunn.co.uk/plugins/jquery-parallax/

 Dual licensed under the MIT and GPL licenses:
 http://www.opensource.org/licenses/mit-license.php
 http://www.gnu.org/licenses/gpl.html
 */

//function that places the navigation in the center of the window
function RepositionNav(){
	var windowHeight = $(window).height(); //get the height of the window
	var navHeight = $('#nav').height() / 2;
	var windowCenter = (windowHeight / 2);
	var newtop = windowCenter - navHeight;
	$('#nav').css({"top": newtop}); //set the new top position of the navigation list
}


(function( $ ){
	$.fn.parallax = function(xpos, adjuster, inertia, outerHeight) {

		function inView(pos, element){

			element.each(function(){ //for each selector, determine whether it's inview and run the move() function

				var element = $(this);
				var top = element.offset().top;

				if(outerHeight == true){
					var height = element.outerHeight(true);
				}else{
					var height = element.height();
				}

				//above & in view
				if(top + height >= pos && top + height - windowHeight < pos){
					move(pos, height);
				}

				//full view
				if(top <= pos && (top + height) >= pos && (top - windowHeight) < pos && top + height - windowHeight > pos){
					move(pos, height);
				}

				//below & in view
				if(top + height > pos && top - windowHeight < pos && top > pos){
					move(pos, height);
				}
			});
		}

		var $window = $(window);
		var windowHeight = $(window).height();
		var pos = $window.scrollTop(); //position of the scrollbar
		var $this = $(this);

		//setup defaults if arguments aren't specified
		if(xpos == null){xpos = "50%"}
		if(adjuster == null){adjuster = 0}
		if(inertia == null){inertia = 0.1}
		if(outerHeight == null){outerHeight = true}

		height = $this.height();
		$this.css({'backgroundPosition': newPos(xpos, outerHeight, adjuster, inertia)});

		function newPos(xpos, windowHeight, pos, adjuster, inertia){
			return xpos + " " + Math.round((-((windowHeight + pos) - adjuster) * inertia)) + "px";
		}

		//function to be called whenever the window is scrolled or resized
		function move(pos, height){
			$this.css({'backgroundPosition': newPos(xpos, height, pos, adjuster, inertia)});
		}

		$window.bind('scroll', function(){ //when the user is scrolling...
			var pos = $window.scrollTop(); //position of the scrollbar
			inView(pos, $this);

			$('#pixels').html(pos);
		})
	}
})( jQuery );