(function() {
	'use strict';

	if ('querySelector' in document && 'addEventListener' in window && Array.prototype.forEach) {
		var smoothscroll = function(anchor, duration) {
			var startLocation = window.pageYOffset;
			var endLocation = anchor.offsetTop;
			var distance = endLocation - startLocation;
			var increments = distance / (duration / 16);
			var stopAnimation;

			var animateScroll = function() {
				window.scrollBy(0, increments);
				stopAnimation();
			}

			if (increments >= 0) {
				stopAnimation = function() {
					var traveled = window.pageYOffset;

					if ((traveled >= (endLocation - increments)) || ((window.innerHeight + traveled) >= document.body.offsetHeight)) {
						clearInterval(runAnimation);
					}
				};
			} else {
				stopAnimation = function() {
					var traveled = window.pageYOffset;

					if (traveled <= (endLocation || 0)) {
						clearInterval(runAnimation);
					}
				};
			}

			var runAnimation = setInterval(animateScroll, 16);
		};

		var scrollToggle = document.querySelectorAll('.scroll');

		[].forEach.call(scrollToggle, function(toggle) {
			toggle.addEventListener('click', function(e) {
				e.preventDefault();

				var dataID = toggle.getAttribute('href');
				var dataTarget = document.querySelector(dataID);
				var dataSpeed = toggle.getAttribute('data-speed');

				if (dataTarget) {
					smoothscroll(dataTarget, dataSpeed || 500);
				}
			}, false);
		});
	}
})();