/**
 * ScrollUp button
 */
var ScrollUp = function ($scope) {

    var $target = $scope.find('.scroll-up'); // your button
    var VISIBLE_CLASS = 'visible'; // class to toggle
    var OFFSET_TOP = 100; // distance offset in 'px' from where the class is being toggled

    // prevent console errors
    if (!$target.length) {
        return;
    }

    changeButtonVisibility();

    /**
     * Visibility
     */
    function changeButtonVisibility() {

        /**
         * Handle Smooth Scroll Bar Plugin
         */
        if (typeof window.SB !== 'undefined') {

            window.SB.addListener(changeButtonClass); // add listener to Smooth Scrollbar plugin

            /**
             * Handle Normal Scroll using Scrollmagic plugin
             */
        } else {

            new $.ScrollMagic.Scene({
                    offset: OFFSET_TOP, // height offset from where it will be shown/hidden
                })
                .setClassToggle($target, VISIBLE_CLASS)
                .addTo(window.SMController); // global ScrollMagic controller

        }

    }

    /**
     * Change class depending on the distance
     * (only Smooth Scrollbar plugin)
     */
    function changeButtonClass() {

        if (window.SB.offset.y >= OFFSET_TOP) { // height offset from where it will be shown/hidden
            $target.addClass(VISIBLE_CLASS);
        } else {
            $target.removeClass(VISIBLE_CLASS);
        }

    }

    /**
     * Interaction
     */
    $target.on('click', function (e) {

        e.preventDefault();

        /**
         * Handle Normal Scroll with simple jQuery
         */
        $('html, body').animate({
            scrollTop: 0
        }, 600, 'swing');

        /**
         * Handle Smooth Scroll Bar Plugin
         */
        if (window.SB !== 'undefined') {

            // scroll to the target
            window.SB.scrollTo(0, 0, 600, { // x, y, speed
                easing: function (pos) { // easing function (if needed)
                    if (pos === 0) return 0;
                    if (pos === 1) return 1;
                    if ((pos /= 0.5) < 1) return 0.5 * Math.pow(2, 10 * (pos - 1));
                    return 0.5 * (-Math.pow(2, -10 * --pos) + 2);
                }
            });
        }

    });

}