jquery(document).ready(function($){
	var	scrolling = false;
	var contentsections = $('.cd-section'),
		verticalnavigation = $('.cd-vertical-nav'),
		navigationitems = verticalnavigation.find('a'),
		navtrigger = $('.cd-nav-trigger'),
		scrollarrow = $('.cd-scroll-down');

	$(window).on('scroll', checkscroll);

	//smooth scroll to the selected section
	verticalnavigation.on('click', 'a', function(event){
        event.preventdefault();
        smoothscroll($(this.hash));
        verticalnavigation.removeclass('open');
    });

    //smooth scroll to the second section
    scrollarrow.on('click', function(event){
    	event.preventdefault();
        smoothscroll($(this.hash));
    });

	// open navigation if user clicks the .cd-nav-trigger - small devices only
    navtrigger.on('click', function(event){
    	event.preventdefault();
    	verticalnavigation.toggleclass('open');
    });

	function checkscroll() {
		if( !scrolling ) {
			scrolling = true;
			(!window.requestanimationframe) ? settimeout(updatesections, 500) : window.requestanimationframe(updatesections);
		}
	}

	function updatesections() {
		var halfwindowheight = $(window).height()/2,
			scrolltop = $(window).scrolltop();
		contentsections.each(function(){
			var section = $(this),
				sectionid = section.attr('id'),
				navigationitem = navigationitems.filter('[href^="#'+ sectionid +'"]');
			( (section.offset().top - halfwindowheight < scrolltop ) && ( section.offset().top + section.height() - halfwindowheight > scrolltop) )
				? navigationitem.addclass('active')
				: navigationitem.removeclass('active');
		});
		scrolling = false;
	}

	function smoothscroll(target) {
        $('body,html').animate(
        	{'scrolltop':target.offset().top},
        	500
        );
	}
});