/**
 * @file
 * Builds a nested accordion widget.
 *
 * Invoke on an HTML list element with the jQuery plugin pattern.
 *
 * @example
 * $('.toolbar-menu').drupalToolbarMenu();
 */

(function ($, Drupal, drupalSettings) {

  'use strict';

  /**
   * Store the open menu tray.
   */
  var activeItem = Drupal.url(drupalSettings.path.currentPath);

  $.fn.drupalToolbarMenu = function () {

    var ui = {
      handleOpen: Drupal.t('Extend'),
      handleClose: Drupal.t('Collapse')
    };

    /**
     * Handle clicks from the disclosure button on an item with sub-items.
     *
     * @param {Object} event
     *   A jQuery Event object.
     */
    function toggleClickHandler(event) {
      var $toggle = $(event.target);
      var $item = $toggle.closest('li');
      // Toggle the list item.
      toggleList($item);
      // Close open sibling menus.
      var $openItems = $item.siblings().filter('.open');
      toggleList($openItems, false);
    }

    /**
     * Handle clicks from a menu item link.
     *
     * @param {Object} event
     *   A jQuery Event object.
     */
    function linkClickHandler(event) {
      // If the toolbar is positioned fixed (and therefore hiding content
      // underneath), then users expect clicks in the administration menu tray
      // to take them to that destination but for the menu tray to be closed
      // after clicking: otherwise the toolbar itself is obstructing the view
      // of the destination they chose.
      if (!Drupal.toolbar.models.toolbarModel.get('isFixed')) {
        Drupal.toolbar.models.toolbarModel.set('activeTab', null);
      }
      // Stopping propagation to make sure that once a toolbar-box is clicked
      // (the whitespace part), the page is not redirected anymore.
      event.stopPropagation();
    }

    /**
     * Toggle the open/close state of a list is a menu.
     *
     * @param {jQuery} $item
     *   The li item to be toggled.
     *
     * @param {Boolean} switcher
     *   A flag that forces toggleClass to add or a remove a class, rather than
     *   simply toggling its presence.
     */
    function toggleList($item, switcher) {
      var $toggle = $item.children('.toolbar-box').children('.toolbar-handle');
      switcher = (typeof switcher !== 'undefined') ? switcher : !$item.hasClass('open');
      // Toggle the item open state.
      $item.toggleClass('open', switcher);
      // Twist the toggle.
      $toggle.toggleClass('open', switcher);
      // Adjust the toggle text.
      $toggle
        .find('.action')
        // Expand Structure, Collapse Structure.
        .text((switcher) ? ui.handleClose : ui.handleOpen);
    }

    /**
     * Add markup to the menu elements.
     *
     * Items with sub-elements have a list toggle attached to them. Menu item
     * links and the corresponding list toggle are wrapped with in a div
     * classed with .toolbar-box. The .toolbar-box div provides a positioning
     * context for the item list toggle.
     *
     * @param {jQuery} $menu
     *   The root of the menu to be initialized.
     */
    function initItems($menu) {
      var options = {
        class: 'toolbar-icon toolbar-handle',
        action: ui.handleOpen,
        text: ''
      };
      // Initialize items and their links.
      $menu.find('li > a').wrap('<div class="toolbar-box">');
      // Add a handle to each list item if it has a menu.
      $menu.find('li').each(function (index, element) {
        var $item = $(element);
        if ($item.children('ul.toolbar-menu').length) {
          var $box = $item.children('.toolbar-box');
          options.text = Drupal.t('@label', {'@label': $box.find('a').text()});
          $item.children('.toolbar-box')
            .append(Drupal.theme('toolbarMenuItemToggle', options));
        }
      });
    }

    /**
     * Adds a level class to each list based on its depth in the menu.
     *
     * This function is called recursively on each sub level of lists elements
     * until the depth of the menu is exhausted.
     *
     * @param {jQuery} $lists
     *   A jQuery object of ul elements.
     *
     * @param {number} level
     *   The current level number to be assigned to the list elements.
     */
    function markListLevels($lists, level) {
      level = (!level) ? 1 : level;
      var $lis = $lists.children('li').addClass('level-' + level);
      $lists = $lis.children('ul');
      if ($lists.length) {
        markListLevels($lists, level + 1);
      }
    }

    /**
     * On page load, open the active menu item.
     *
     * Marks the trail of the active link in the menu back to the root of the
     * menu with .menu-item--active-trail.
     *
     * @param {jQuery} $menu
     *   The root of the menu.
     */
    function openActiveItem($menu) {
      var pathItem = $menu.find('a[href="' + location.pathname + '"]');
      if (pathItem.length && !activeItem) {
        activeItem = location.pathname;
      }
      if (activeItem) {
        var $activeItem = $menu.find('a[href="' + activeItem + '"]').addClass('menu-item--active');
        var $activeTrail = $activeItem.parentsUntil('.root', 'li').addClass('menu-item--active-trail');
        toggleList($activeTrail, true);
      }
    }

    // Return the jQuery object.
    return this.each(function (selector) {
      var $menu = $(this).once('toolbar-menu');
      if ($menu.length) {
        // Bind event handlers.
        $menu
          .on('click.toolbar', '.toolbar-box', toggleClickHandler)
          .on('click.toolbar', '.toolbar-box a', linkClickHandler);

        $menu.addClass('root');
        initItems($menu);
        markListLevels($menu);
        // Restore previous and active states.
        openActiveItem($menu);
      }
    });
  };

  /**
   * A toggle is an interactive element often bound to a click handler.
   *
   * @param {object} options
   *   Options for the button.
   * @param {string} options.class
   *   Class to set on the button.
   * @param {string} options.action
   *   Action for the button.
   * @param {string} options.text
   *   Used as label for the button.
   *
   * @return {string}
   *   A string representing a DOM fragment.
   */
  Drupal.theme.toolbarMenuItemToggle = function (options) {
    return '<button class="' + options['class'] + '"><span class="action">' + options.action + '</span><span class="label">' + options.text + '</span></button>';
  };

}(jQuery, Drupal, drupalSettings));
