Team:NCTU Formosa/source/scrollit

/**

* ScrollIt
* ScrollIt.js(scroll•it•dot•js) makes it easy to make long, vertically scrolling pages.
*
* Latest version: https://github.com/cmpolis/scrollIt.js
*
* License <https://github.com/cmpolis/scrollIt.js/blob/master/LICENSE.txt>
*/

(function($) {

   'use strict';

   var pluginName = 'ScrollIt',
       pluginVersion = '1.0.3';

   /*
    * OPTIONS
    */
   var defaults = {
       upKey: 38,
       downKey: 40,
       easing: 'linear',
       scrollTime: 600,
       activeClass: 'active',
       onPageChange: null,
       topOffset : 0
   };

   $.scrollIt = function(options) {

       /*
        * DECLARATIONS
        */
       var settings = $.extend(defaults, options),
           active = 0,
           lastIndex = $('[data-scroll-index]:last').attr('data-scroll-index');

       /*
        * METHODS
        */

       /**
        * navigate
        *
        * sets up navigation animation
        */
       var navigate = function(ndx) {
           if(ndx < 0 || ndx > lastIndex) return;

           var targetTop = $('[data-scroll-index=' + ndx + ']').offset().top + settings.topOffset + 1;
           $('html,body').animate({
               scrollTop: targetTop,
               easing: settings.easing
           }, settings.scrollTime);
       };

       /**
        * doScroll
        *
        * runs navigation() when criteria are met
        */
       var doScroll = function (e) {
           var target = $(e.target).closest("[data-scroll-nav]").attr('data-scroll-nav') ||
           $(e.target).closest("[data-scroll-goto]").attr('data-scroll-goto');
           navigate(parseInt(target));
       };

       /**
        * keyNavigation
        *
        * sets up keyboard navigation behavior
        */
       var keyNavigation = function (e) {
           var key = e.which;
           if($('html,body').is(':animated') && (key == settings.upKey || key == settings.downKey)) {
               return false;
           }
           if(key == settings.upKey && active > 0) {
               navigate(parseInt(active) - 1);
               return false;
           } else if(key == settings.downKey && active < lastIndex) {
               navigate(parseInt(active) + 1);
               return false;
           }
           return true;
       };

       /**
        * updateActive
        *
        * sets the currently active item
        */
       var updateActive = function(ndx) {
           if(settings.onPageChange && ndx && (active != ndx)) settings.onPageChange(ndx);

           active = ndx;
           $('[data-scroll-nav]').removeClass(settings.activeClass);
           $('[data-scroll-nav=' + ndx + ']').addClass(settings.activeClass);
       };

       /**
        * watchActive
        *
        * watches currently active item and updates accordingly
        */
       var watchActive = function() {
           var winTop = $(window).scrollTop();

           var visible = $('[data-scroll-index]').filter(function(ndx, div) {
               return winTop >= $(div).offset().top + settings.topOffset &&
               winTop < $(div).offset().top + (settings.topOffset) + $(div).outerHeight()
           });
           var newActive = visible.first().attr('data-scroll-index');
           updateActive(newActive);
       };

       /*
        * runs methods
        */
       $(window).on('scroll',watchActive).scroll();

       $(window).on('keydown', keyNavigation);

       $('body').on('click','[data-scroll-nav], [data-scroll-goto]', function(e){
           e.preventDefault();
           doScroll(e);
       });

   };

}(jQuery));