/* --------------------------------------------------------------
 pageup.js 2016-03-09
 Gambio GmbH
 http://www.gambio.de
 Copyright (c) 2015 Gambio GmbH
 Released under the GNU General Public License (Version 2)
 [http://www.gnu.org/licenses/gpl-2.0.html]
 --------------------------------------------------------------
 */

/**
 * Component that displays a "Page Up" button if the
 * page is not at top position. On click the page
 * scrolls up to top
 */
gambio.widgets.module(
    'pageup',

    [
        gambio.source + '/libs/events'
    ],

    function (data) {

        'use strict';

// ########## VARIABLE INITIALIZATION ##########

        var $this = $(this),
            $window = $(window),
            visible = false,
            transition = {},
            defaults = {
                top: 200,        // Pixel from top needs to be reached before the button gets displayed
                duration: 300,        // Animation time to scroll up
                showClass: 'visible'   // Class that gets added to show the pageup element (else it will be hidden)
            },
            options = $.extend(true, {}, defaults, data),
            module = {};


// ########## EVENT HANDLER ##########

        /**
         * Event handler for the scroll event.
         * If the current scroll position ist higher
         * than the position given by options.top
         * the button gets displayed.
         * @private
         */
        var _scrollHandler = function () {
            var show = $window.scrollTop() > options.top;

            if (show && !visible) {
                visible = true;
                transition.open = true;
                $this.trigger(jse.libs.theme.events.TRANSITION(), transition);
            } else if (!show && visible) {
                visible = false;
                transition.open = false;
                $this.trigger(jse.libs.theme.events.TRANSITION(), transition);
            }
        };


        /**
         * Event handler for clicking on the
         * page-up button. It scrolls up the
         * page.
         * @private
         */
        var _clickHandler = function (e) {
            e.preventDefault();
            $('html, body').animate({scrollTop: '0'}, options.duration);
        };

// ########## INITIALIZATION ##########


        /**
         * Init function of the widget
         * @constructor
         */
        module.init = function (done) {

            transition.classOpen = options.showClass;

            $window.on('scroll', _scrollHandler);
            $this.on('click', _clickHandler);

            _scrollHandler();

            done();
        };

        // Return data to widget engine
        return module;
    });