/*
JavaScript for the demo: Recreating the Nikebetterworld.com Parallax Demo
Demo: Recreating the Nikebetterworld.com Parallax Demo
Author: Ian Lunn
Author URL: http://www.ianlunn.co.uk/
Demo URL: http://www.ianlunn.co.uk/demos/recreate-nikebetterworld-parallax/
Tutorial URL: http://www.ianlunn.co.uk/blog/code-tutorials/recreate-nikebetterworld-parallax/

License: http://creativecommons.org/licenses/by-sa/3.0/ (Attribution Share Alike). Please attribute work to Ian Lunn simply by leaving these comments in the source code or if you'd prefer, place a link on your website to http://www.ianlunn.co.uk/.

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

$(document).ready(function() { //when the document is ready...


	//save selectors as variables to increase performance
	var $window = $(window);
	var $firstBG = $('#intro');
	var $secondBG = $('#second');
	var $thirdBG = $('#third');
	var $fourthBG = $('#fourth');
	var $fifthBG = $('#fifth');
	var $sixthBG = $('#sixth');
	var $seventhBG = $('#seventh');
	var $eightBG = $('#eight');
	var $ninthBG = $('#ninth');
	var $tenthBG = $('#tenth');
	var trainers = $("#seventh .bg");
	var web = $("#sixth .bg");
	var home = $("#intro .bg");
	var map = $("#tenth .bg");
	
	var windowHeight = $window.height(); //get the height of the window
	
	
	//apply the class "inview" to a section that is in the viewport
	$('#intro, #second, #third, #fourth, #fifth, #sixth, #seventh, #eight, #ninth, #tenth').bind('inview', function (event, visible) {
			if (visible == true) {
			$(this).addClass("inview");
			} else {
			$(this).removeClass("inview");
			}
		});
	
			
	//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 that is called for every pixel the user scrolls. Determines the position of the background
	/*arguments: 
		x = horizontal position of background
		windowHeight = height of the viewport
		pos = position of the scrollbar
		adjuster = adjust the position of the background
		inertia = how fast the background moves in relation to scrolling
	*/
	function newPos(x, windowHeight, pos, adjuster, inertia){
		return x + "% " + (-((windowHeight + pos) - adjuster) * inertia)  + "px";
	}
	
	//function to be called whenever the window is scrolled or resized
	function Move(){ 
		var pos = $window.scrollTop(); //position of the scrollbar

		//if the first section is in view...
		if($firstBG.hasClass("inview")){
			//call the newPos function and change the background position
			$firstBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 860, 0.3)}); 
			home.css({'backgroundPosition': newPos(50, windowHeight, pos, 2150, 0.5)});
		}
		
		//if the second section is in view...
		if($secondBG.hasClass("inview")){
			//call the newPos function and change the background position
			$secondBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 2310, 0.3)});
			//call the newPos function and change the second background position
		}
		
		//if the third section is in view...
		if($thirdBG.hasClass("inview")){
			//call the newPos function and change the background position
			$thirdBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 3590, 0.3)});
		}
		
		//if the fourth section is in view...
		if($fourthBG.hasClass("inview")){
			//call the newPos function and change the background position for CSS3 multiple backgrounds
			$fourthBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 4900, 0.3)});
		}
		
		
			//if the fifth section is in view...
			if($fifthBG.hasClass("inview")){
				//call the newPos function and change the background position for CSS3 multiple backgrounds
				$fifthBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 6090, 0.3)});
			}
			
			//if the fifth section is in view...
			if($sixthBG.hasClass("inview")){
				//call the newPos function and change the background position for CSS3 multiple backgrounds
				$sixthBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 7600, 0.3)});
				web.css({'backgroundPosition': newPos(50, windowHeight, pos, 8050, 0.9)});
				
			}
		
			//if the fifth section is in view...
			if($seventhBG.hasClass("inview")){
				//call the newPos function and change the background position for CSS3 multiple backgrounds
				$seventhBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 8850, 0.3)});
				trainers.css({'backgroundPosition': newPos(50, windowHeight, pos, 9300, 0.9)});
			}
		
			//if the fifth section is in view...
			if($eightBG.hasClass("inview")){
				//call the newPos function and change the background position for CSS3 multiple backgrounds
				$eightBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 10070, 0.3)});
			}
				//if the fifth section is in view...
				if($ninthBG.hasClass("inview")){
					//call the newPos function and change the background position for CSS3 multiple backgrounds
					$ninthBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 11350, 0.3)});
				}
			
		
					//if the fifth section is in view...
					if($tenthBG.hasClass("inview")){
						//call the newPos function and change the background position for CSS3 multiple backgrounds
						$tenthBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 10050, 0.3)});
						map.css({'backgroundPosition': newPos(50, windowHeight, pos, 10400, 0.4)});
					}
			
			
		
		$('#pixels').html(pos); //display the number of pixels scrolled at the bottom of the page
	}
		
	RepositionNav(); //Reposition the Navigation to center it in the window when the script loads
	
	$window.resize(function(){ //if the user resizes the window...
		Move(); //move the background images in relation to the movement of the scrollbar
		RepositionNav(); //reposition the navigation list so it remains vertically central
	});		
	
	$window.bind('scroll', function(){ //when the user is scrolling...
		Move(); //move the background images in relation to the movement of the scrollbar
	});
	
});