define(['jquery', 'underscore'], function ($, _) {
  'use strict';
  var windowWidth = $(window).width(),
    initialResize = true;
  if (!!Modernizr) {
    $(window).on(
      'resize',
      _.debounce(function () {
        // Skip the resize execution, if the width of the browser is the same as initialized and it's not the first resize.
        if ($(window).width() === windowWidth && !initialResize) {
          return;
        }

        initialResize = false;

        var $mainMenuContainer = $('.main-navigation');

        // Add the .js-dropdown class to all sub-menus within the main menu container.
        addDropdownClassToSubmenus($mainMenuContainer);

        if (Modernizr.mq('(min-width: 992px)') && Modernizr.touchevents) {
          // Remove any previous dropdown buttons from mobile layout.
          removeDropdownButtonsFromMenuItems($mainMenuContainer);

          // Hide all submenus (display: block).
          showAllSubmenus($mainMenuContainer);

          // Register the custom click event to simulate click/hover.
          registerMenuHoverClick('ul.js-dropdown');
        } else if (Modernizr.mq('(max-width: 991px)')) {
          // mobile layout (from 0 to 991px).
          // Disable custom click event from desktop layout.
          disableMenuHoverClick('ul.js-dropdown');

          // Remove any previous dropdown buttons.
          removeDropdownButtonsFromMenuItems($mainMenuContainer);

          // Hide all submenus (display: hidden).
          hideAllSubmenus($mainMenuContainer);

          // Add buttons for mobile dropdown
          addDropdownButtonsToMenuItems($mainMenuContainer);
        } else {
          // Disable custom click event from desktop layout.
          disableMenuHoverClick('ul.js-dropdown');

          // Remove any previous dropdown buttons from mobile layout.
          removeDropdownButtonsFromMenuItems($mainMenuContainer);

          // Hide all submenus (display: block).
          showAllSubmenus($mainMenuContainer);
        }
      }, 100)
    );
    // Trigger the initial resize.
    $(window).trigger('resize');
  }

  /**
   * Add the .js-dropdown class to all sub-menus of the menu container.
   *
   * @param $menuContainer The menu container (a jQuery object).
   */
  function addDropdownClassToSubmenus($menuContainer) {
    $menuContainer.find('.sub-menu').addClass('js-dropdown');
  }

  /**
   * Register custom click event for each menu item with a submenu.
   *
   * @param submenuClass A class of submenus.
   */
  function registerMenuHoverClick(submenuClass) {
    $(submenuClass).each(function (i, elm) {
      $(elm)
        .children('.menu-item-has-children')
        .on('click.td', 'a', function (ev) {
          ev.preventDefault();

          // Clear the hover state if you switch to other dropdown menu
          $(elm).children('.is-hover').removeClass('is-hover');

          $(ev.delegateTarget).addClass('is-hover');
          $(ev.delegateTarget).off('click.td');
        });
    });
  }
  /**
   * Add dropdown buttons with show/hide submenu event.
   *
   * @param $mainMenuContainer A main menu container.
   */
  function addDropdownButtonsToMenuItems($mainMenuContainer) {
    var $dropdownButton = $('<button />', {
      class: 'dropdown-toggle dropdown-toggle--close',
      'aria-expanded': false,
    }).append('<i class="fa fa-chevron-down" aria-hidden="true"></i>');

    $mainMenuContainer
      .find('.menu-item-has-children > a')
      .after($dropdownButton);

    $mainMenuContainer
      .find('.menu-item-has-children > button.dropdown-toggle')
      .on('click.tdm', function (ev) {
        ev.preventDefault();

        $(ev.currentTarget).siblings('.sub-menu').toggle();

        $(ev.currentTarget)
          .toggleClass('dropdown-toggle--close')
          .toggleClass('dropdown-toggle--open');

        $(ev.currentTarget)
          .children('i.fa')
          .toggleClass('fa-chevron-down')
          .toggleClass('fa-chevron-up');
      });
  }

  function disableMenuHoverClick(submenuClass) {
    $(submenuClass).each(function (i, elm) {
      $(elm).children('.menu-item-has-children').off('click.td');
    });
  }
  function removeDropdownButtonsFromMenuItems($mainMenuContainer) {
    $mainMenuContainer
      .find('.menu-item-has-children > button.dropdown-toggle')
      .remove();
  }
  /**
   * Hide all menu submenus.
   *
   * @param $mainMenuContainer A main menu container.
   */
  function hideAllSubmenus($mainMenuContainer) {
    $mainMenuContainer.find('.sub-menu').hide();
  }
  /**
   * Show all menu submenus.
   *
   * @param $mainMenuContainer A main menu container.
   */
  function showAllSubmenus($mainMenuContainer) {
    $mainMenuContainer.find('.sub-menu').show();
  }
});
