/*
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 $empresaBG = $('#empresa');
	var $catalogosBG = $('#catalogos');
	var $comunicacaoBG = $('#comunicacao');
	var $makingBG = $('#making');
	var $videoBG = $('#video');
	var $clientesBG = $('#clientes');
	
	var $empresaBTN = $('#nav li.btn-empresa a');
	var $catalogosBTN = $('#nav li.btn-catalogos a');
	var $comunicacaoBTN = $('#nav li.btn-comunicacao a');
	var $makingBTN = $('#nav li.btn-making a');
	var $videoBTN = $('#nav li.btn-video a');
	var $clientesBTN = $('#nav li.btn-clientes a');
	
	var windowHeight = $window.height(); //get the height of the window



		
	
	//apply the class "inview" to a section that is in the viewport
	$('#empresa, #catalogos, #comunicacao, #making, #video, #clientes').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($empresaBG.hasClass("inview")){
			$empresaBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 900, 0.3)});
			$('#nav li a').parent("li").siblings().find("a").removeClass("focus");
			$empresaBTN.addClass("focus"); 
		}
		
		//if the second section is in view...
		if($catalogosBG.hasClass("inview")){
			$catalogosBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 2271, 0.3)});
			$('#nav li a').parent("li").siblings().find("a").removeClass("focus");
			$catalogosBTN.addClass("focus");
		}
		
		//if the third section is in view...
		if($comunicacaoBG.hasClass("inview")){
			$comunicacaoBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 2850, 0.3)});
			$('#nav li a').parent("li").siblings().find("a").removeClass("focus");
			$comunicacaoBTN.addClass("focus");
		}
		
		//if the making section is in view...
		if($makingBG.hasClass("inview")){
			$makingBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 4500, 0.3)});
			$('#nav li a').parent("li").siblings().find("a").removeClass("focus");
			$makingBTN.addClass("focus");
			
		}
		
		//if the fourth section is in view...
		if($videoBG.hasClass("inview")){
			$videoBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 5000, 0.3)});
			$('#nav li a').parent("li").siblings().find("a").removeClass("focus");
			$videoBTN.addClass("focus");
		}
		
		//if the fifth section is in view...
		if($clientesBG.hasClass("inview")){
			$clientesBG.css({'backgroundPosition': newPos(50, windowHeight, pos, 6500, 0.3)});
			$('#nav li a').parent("li").siblings().find("a").removeClass("focus");
			$clientesBTN.addClass("focus");
		}
		
		$('#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
	});
	
});