class-wp-bootstrap-navwalker.php

<?php
/**
 * WP Bootstrap Navwalker
 *
 * @package WP-Bootstrap-Navwalker
 */

/*
 * Class Name: WP_Bootstrap_Navwalker
 * Plugin Name: WP Bootstrap Navwalker
 * Plugin URI:  https://github.com/wp-bootstrap/wp-bootstrap-navwalker
 * Description: A custom WordPress nav walker class to implement the Bootstrap 4 navigation style in a custom theme using the WordPress built in menu manager.
 * Author: Edward McIntyre - @twittem, WP Bootstrap, William Patton - @pattonwebz
 * Version: 4.1.0
 * Author URI: https://github.com/wp-bootstrap
 * GitHub Plugin URI: https://github.com/wp-bootstrap/wp-bootstrap-navwalker
 * GitHub Branch: master
 * License: GPL-3.0+
 * License URI: http://www.gnu.org/licenses/gpl-3.0.txt
*/

/* Check if Class Exists. */
if ( ! class_exists( 'WP_Bootstrap_Navwalker' ) ) {
  /**
   * WP_Bootstrap_Navwalker class.
   *
   * @extends Walker_Nav_Menu
   */
  class WP_Bootstrap_Navwalker extends Walker_Nav_Menu {

    /**
     * Starts the list before the elements are added.
     *
     * @since WP 3.0.0
     *
     * @see Walker_Nav_Menu::start_lvl()
     *
     * @param string   $output Used to append additional content (passed by reference).
     * @param int      $depth  Depth of menu item. Used for padding.
     * @param stdClass $args   An object of wp_nav_menu() arguments.
     */
    public function start_lvl( &$output, $depth = 0, $args = array() ) {
      if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
        $t = '';
        $n = '';
      } else {
        $t = "\t";
        $n = "\n";
      }
      $indent = str_repeat( $t, $depth );
      // Default class to add to the file.
      $classes = array( 'dropdown-menu' );
      /**
       * Filters the CSS class(es) applied to a menu list element.
       *
       * @since WP 4.8.0
       *
       * @param array    $classes The CSS classes that are applied to the menu `<ul>` element.
       * @param stdClass $args    An object of `wp_nav_menu()` arguments.
       * @param int      $depth   Depth of menu item. Used for padding.
       */
      $class_names = join( ' ', apply_filters( 'nav_menu_submenu_css_class', $classes, $args, $depth ) );
      $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
      /**
       * The `.dropdown-menu` container needs to have a labelledby
       * attribute which points to it's trigger link.
       *
       * Form a string for the labelledby attribute from the the latest
       * link with an id that was added to the $output.
       */
      $labelledby = '';
      // find all links with an id in the output.
      preg_match_all( '/(<a.*?id=\"|\')(.*?)\"|\'.*?>/im', $output, $matches );
      // with pointer at end of array check if we got an ID match.
      if ( end( $matches[2] ) ) {
        // build a string to use as aria-labelledby.
        $labelledby = 'aria-labelledby="' . end( $matches[2] ) . '"';
      }
      $output .= "{$n}{$indent}<ul$class_names $labelledby role=\"menu\">{$n}";
    }

    /**
     * Starts the element output.
     *
     * @since WP 3.0.0
     * @since WP 4.4.0 The {@see 'nav_menu_item_args'} filter was added.
     *
     * @see Walker_Nav_Menu::start_el()
     *
     * @param string   $output Used to append additional content (passed by reference).
     * @param WP_Post  $item   Menu item data object.
     * @param int      $depth  Depth of menu item. Used for padding.
     * @param stdClass $args   An object of wp_nav_menu() arguments.
     * @param int      $id     Current item ID.
     */
    public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
      if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
        $t = '';
        $n = '';
      } else {
        $t = "\t";
        $n = "\n";
      }
      $indent = ( $depth ) ? str_repeat( $t, $depth ) : '';

      $classes = empty( $item->classes ) ? array() : (array) $item->classes;

      // Initialize some holder variables to store specially handled item
      // wrappers and icons.
      $linkmod_classes = array();
      $icon_classes    = array();

      /**
       * Get an updated $classes array without linkmod or icon classes.
       *
       * NOTE: linkmod and icon class arrays are passed by reference and
       * are maybe modified before being used later in this function.
       */
      $classes = self::seporate_linkmods_and_icons_from_classes( $classes, $linkmod_classes, $icon_classes, $depth );

      // Join any icon classes plucked from $classes into a string.
      $icon_class_string = join( ' ', $icon_classes );

      /**
       * Filters the arguments for a single nav menu item.
       *
       *  WP 4.4.0
       *
       * @param stdClass $args  An object of wp_nav_menu() arguments.
       * @param WP_Post  $item  Menu item data object.
       * @param int      $depth Depth of menu item. Used for padding.
       */
      $args = apply_filters( 'nav_menu_item_args', $args, $item, $depth );

      // Add .dropdown or .active classes where they are needed.
      if ( isset( $args->has_children ) && $args->has_children ) {
        $classes[] = 'dropdown';
      }
      if ( in_array( 'current-menu-item', $classes, true ) || in_array( 'current-menu-parent', $classes, true ) ) {
        $classes[] = 'active';
      }

      // Add some additional default classes to the item.
      $classes[] = 'menu-item-' . $item->ID;
      $classes[] = 'nav-item';

      // Allow filtering the classes.
      $classes = apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args, $depth );

      // Form a string of classes in format: class="class_names".
      $class_names = join( ' ', $classes );
      $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';

      /**
       * Filters the ID applied to a menu item's list item element.
       *
       * @since WP 3.0.1
       * @since WP 4.1.0 The `$depth` parameter was added.
       *
       * @param string   $menu_id The ID that is applied to the menu item's `<li>` element.
       * @param WP_Post  $item    The current menu item.
       * @param stdClass $args    An object of wp_nav_menu() arguments.
       * @param int      $depth   Depth of menu item. Used for padding.
       */
      $id = apply_filters( 'nav_menu_item_id', 'menu-item-' . $item->ID, $item, $args, $depth );
      $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';

      $output .= $indent . '<li itemscope="itemscope" itemtype="https://www.schema.org/SiteNavigationElement"' . $id . $class_names . '>';

      // initialize array for holding the $atts for the link item.
      $atts = array();

      // Set title from item to the $atts array - if title is empty then
      // default to item title.
      if ( empty( $item->attr_title ) ) {
        $atts['title'] = ! empty( $item->title ) ? strip_tags( $item->title ) : '';
      } else {
        $atts['title'] = $item->attr_title;
      }

      $atts['target'] = ! empty( $item->target ) ? $item->target : '';
      $atts['rel']    = ! empty( $item->xfn ) ? $item->xfn : '';
      // If item has_children add atts to <a>.
      if ( isset( $args->has_children ) && $args->has_children && 0 === $depth && $args->depth > 1 ) {
        $atts['href']          = '#';
        $atts['data-toggle']   = 'dropdown';
        $atts['aria-haspopup'] = 'true';
        $atts['aria-expanded'] = 'false';
        $atts['class']         = 'dropdown-toggle nav-link';
        $atts['id']            = 'menu-item-dropdown-' . $item->ID;
      } else {
        $atts['href'] = ! empty( $item->url ) ? $item->url : '#';
        // Items in dropdowns use .dropdown-item instead of .nav-link.
        if ( $depth > 0 ) {
          $atts['class'] = 'dropdown-item';
        } else {
          $atts['class'] = 'nav-link';
        }
      }

      // update atts of this item based on any custom linkmod classes.
      $atts = self::update_atts_for_linkmod_type( $atts, $linkmod_classes );
      // Allow filtering of the $atts array before using it.
      $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args, $depth );

      // Build a string of html containing all the atts for the item.
      $attributes = '';
      foreach ( $atts as $attr => $value ) {
        if ( ! empty( $value ) ) {
          $value       = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
          $attributes .= ' ' . $attr . '="' . $value . '"';
        }
      }

      /**
       * Set a typeflag to easily test if this is a linkmod or not.
       */
      $linkmod_type = self::get_linkmod_type( $linkmod_classes );

      /**
       * START appending the internal item contents to the output.
       */
      $item_output = isset( $args->before ) ? $args->before : '';
      /**
       * This is the start of the internal nav item. Depending on what
       * kind of linkmod we have we may need different wrapper elements.
       */
      if ( '' !== $linkmod_type ) {
        // is linkmod, output the required element opener.
        $item_output .= self::linkmod_element_open( $linkmod_type, $attributes );
      } else {
        // With no link mod type set this must be a standard <a> tag.
        $item_output .= '<a' . $attributes . '>';
      }

      /**
       * Initiate empty icon var, then if we have a string containing any
       * icon classes form the icon markup with an <i> element. This is
       * output inside of the item before the $title (the link text).
       */
      $icon_html = '';
      if ( ! empty( $icon_class_string ) ) {
        // append an <i> with the icon classes to what is output before links.
        $icon_html = '<i class="' . esc_attr( $icon_class_string ) . '" aria-hidden="true"></i> ';
      }

      /** This filter is documented in wp-includes/post-template.php */
      $title = apply_filters( 'the_title', $item->title, $item->ID );

      /**
       * Filters a menu item's title.
       *
       * @since WP 4.4.0
       *
       * @param string   $title The menu item's title.
       * @param WP_Post  $item  The current menu item.
       * @param stdClass $args  An object of wp_nav_menu() arguments.
       * @param int      $depth Depth of menu item. Used for padding.
       */
      $title = apply_filters( 'nav_menu_item_title', $title, $item, $args, $depth );

      /**
       * If the .sr-only class was set apply to the nav items text only.
       */
      if ( in_array( 'sr-only', $linkmod_classes, true ) ) {
        $title         = self::wrap_for_screen_reader( $title );
        $keys_to_unset = array_keys( $linkmod_classes, 'sr-only' );
        foreach ( $keys_to_unset as $k ) {
          unset( $linkmod_classes[ $k ] );
        }
      }

      // Put the item contents into $output.
      $item_output .= isset( $args->link_before ) ? $args->link_before . $icon_html . $title . $args->link_after : '';
      /**
       * This is the end of the internal nav item. We need to close the
       * correct element depending on the type of link or link mod.
       */
      if ( '' !== $linkmod_type ) {
        // is linkmod, output the required element opener.
        $item_output .= self::linkmod_element_close( $linkmod_type, $attributes );
      } else {
        // With no link mod type set this must be a standard <a> tag.
        $item_output .= '</a>';
      }

      $item_output .= isset( $args->after ) ? $args->after : '';

      /**
       * END appending the internal item contents to the output.
       */
      $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );

    }

    /**
     * Traverse elements to create list from elements.
     *
     * Display one element if the element doesn't have any children otherwise,
     * display the element and its children. Will only traverse up to the max
     * depth and no ignore elements under that depth. It is possible to set the
     * max depth to include all depths, see walk() method.
     *
     * This method should not be called directly, use the walk() method instead.
     *
     * @since WP 2.5.0
     *
     * @see Walker::start_lvl()
     *
     * @param object $element           Data object.
     * @param array  $children_elements List of elements to continue traversing (passed by reference).
     * @param int    $max_depth         Max depth to traverse.
     * @param int    $depth             Depth of current element.
     * @param array  $args              An array of arguments.
     * @param string $output            Used to append additional content (passed by reference).
     */
    public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
      if ( ! $element ) {
        return; }
      $id_field = $this->db_fields['id'];
      // Display this element.
      if ( is_object( $args[0] ) ) {
        $args[0]->has_children = ! empty( $children_elements[ $element->$id_field ] ); }
      parent::display_element( $element, $children_elements, $max_depth, $depth, $args, $output );
    }

    /**
     * Menu Fallback
     * =============
     * If this function is assigned to the wp_nav_menu's fallback_cb variable
     * and a menu has not been assigned to the theme location in the WordPress
     * menu manager the function with display nothing to a non-logged in user,
     * and will add a link to the WordPress menu manager if logged in as an admin.
     *
     * @param array $args passed from the wp_nav_menu function.
     */
    public static function fallback( $args ) {
      if ( current_user_can( 'edit_theme_options' ) ) {

        /* Get Arguments. */
        $container       = $args['container'];
        $container_id    = $args['container_id'];
        $container_class = $args['container_class'];
        $menu_class      = $args['menu_class'];
        $menu_id         = $args['menu_id'];

        // initialize var to store fallback html.
        $fallback_output = '';

        if ( $container ) {
          $fallback_output .= '<' . esc_attr( $container );
          if ( $container_id ) {
            $fallback_output .= ' id="' . esc_attr( $container_id ) . '"';
          }
          if ( $container_class ) {
            $fallback_output .= ' class="' . esc_attr( $container_class ) . '"';
          }
          $fallback_output .= '>';
        }
        $fallback_output .= '<ul';
        if ( $menu_id ) {
          $fallback_output .= ' id="' . esc_attr( $menu_id ) . '"'; }
        if ( $menu_class ) {
          $fallback_output .= ' class="' . esc_attr( $menu_class ) . '"'; }
        $fallback_output .= '>';
        $fallback_output .= '<li><a href="' . esc_url( admin_url( 'nav-menus.php' ) ) . '" title="' . esc_attr__( 'Add a menu', 'wp-bootstrap-navwalker' ) . '">' . esc_html__( 'Add a menu', 'wp-bootstrap-navwalker' ) . '</a></li>';
        $fallback_output .= '</ul>';
        if ( $container ) {
          $fallback_output .= '</' . esc_attr( $container ) . '>';
        }

        // if $args has 'echo' key and it's true echo, otherwise return.
        if ( array_key_exists( 'echo', $args ) && $args['echo'] ) {
          echo $fallback_output; // WPCS: XSS OK.
        } else {
          return $fallback_output;
        }
      }
    }

    /**
     * Find any custom linkmod or icon classes and store in their holder
     * arrays then remove them from the main classes array.
     *
     * Supported linkmods: .disabled, .dropdown-header, .dropdown-divider, .sr-only
     * Supported iconsets: Font Awesome 4/5, Glypicons
     *
     * NOTE: This accepts the linkmod and icon arrays by reference.
     *
     * @since 4.0.0
     *
     * @param array   $classes         an array of classes currently assigned to the item.
     * @param array   $linkmod_classes an array to hold linkmod classes.
     * @param array   $icon_classes    an array to hold icon classes.
     * @param integer $depth           an integer holding current depth level.
     *
     * @return array  $classes         a maybe modified array of classnames.
     */
    private function seporate_linkmods_and_icons_from_classes( $classes, &$linkmod_classes, &$icon_classes, $depth ) {
      // Loop through $classes array to find linkmod or icon classes.
      foreach ( $classes as $key => $class ) {
        // If any special classes are found, store the class in it's
        // holder array and and unset the item from $classes.
        if ( preg_match( '/^disabled|^sr-only/i', $class ) ) {
          // Test for .disabled or .sr-only classes.
          $linkmod_classes[] = $class;
          unset( $classes[ $key ] );
        } elseif ( preg_match( '/^dropdown-header|^dropdown-divider|^dropdown-item-text/i', $class ) && $depth > 0 ) {
          // Test for .dropdown-header or .dropdown-divider and a
          // depth greater than 0 - IE inside a dropdown.
          $linkmod_classes[] = $class;
          unset( $classes[ $key ] );
        } elseif ( preg_match( '/^fa-(\S*)?|^fa(s|r|l|b)?(\s?)?$/i', $class ) ) {
          // Font Awesome.
          $icon_classes[] = $class;
          unset( $classes[ $key ] );
        } elseif ( preg_match( '/^glyphicon-(\S*)?|^glyphicon(\s?)$/i', $class ) ) {
          // Glyphicons.
          $icon_classes[] = $class;
          unset( $classes[ $key ] );
        }
      }

      return $classes;
    }

    /**
     * Return a string containing a linkmod type and update $atts array
     * accordingly depending on the decided.
     *
     * @since 4.0.0
     *
     * @param array $linkmod_classes array of any link modifier classes.
     *
     * @return string                empty for default, a linkmod type string otherwise.
     */
    private function get_linkmod_type( $linkmod_classes = array() ) {
      $linkmod_type = '';
      // Loop through array of linkmod classes to handle their $atts.
      if ( ! empty( $linkmod_classes ) ) {
        foreach ( $linkmod_classes as $link_class ) {
          if ( ! empty( $link_class ) ) {

            // check for special class types and set a flag for them.
            if ( 'dropdown-header' === $link_class ) {
              $linkmod_type = 'dropdown-header';
            } elseif ( 'dropdown-divider' === $link_class ) {
              $linkmod_type = 'dropdown-divider';
            } elseif ( 'dropdown-item-text' === $link_class ) {
              $linkmod_type = 'dropdown-item-text';
            }
          }
        }
      }
      return $linkmod_type;
    }

    /**
     * Update the attributes of a nav item depending on the limkmod classes.
     *
     * @since 4.0.0
     *
     * @param array $atts            array of atts for the current link in nav item.
     * @param array $linkmod_classes an array of classes that modify link or nav item behaviors or displays.
     *
     * @return array                 maybe updated array of attributes for item.
     */
    private function update_atts_for_linkmod_type( $atts = array(), $linkmod_classes = array() ) {
      if ( ! empty( $linkmod_classes ) ) {
        foreach ( $linkmod_classes as $link_class ) {
          if ( ! empty( $link_class ) ) {
            // update $atts with a space and the extra classname...
            // so long as it's not a sr-only class.
            if ( 'sr-only' !== $link_class ) {
              $atts['class'] .= ' ' . esc_attr( $link_class );
            }
            // check for special class types we need additional handling for.
            if ( 'disabled' === $link_class ) {
              // Convert link to '#' and unset open targets.
              $atts['href'] = '#';
              unset( $atts['target'] );
            } elseif ( 'dropdown-header' === $link_class || 'dropdown-divider' === $link_class || 'dropdown-item-text' === $link_class ) {
              // Store a type flag and unset href and target.
              unset( $atts['href'] );
              unset( $atts['target'] );
            }
          }
        }
      }
      return $atts;
    }

    /**
     * Wraps the passed text in a screen reader only class.
     *
     * @since 4.0.0
     *
     * @param string $text the string of text to be wrapped in a screen reader class.
     * @return string      the string wrapped in a span with the class.
     */
    private function wrap_for_screen_reader( $text = '' ) {
      if ( $text ) {
        $text = '<span class="sr-only">' . $text . '</span>';
      }
      return $text;
    }

    /**
     * Returns the correct opening element and attributes for a linkmod.
     *
     * @since 4.0.0
     *
     * @param string $linkmod_type a sting containing a linkmod type flag.
     * @param string $attributes   a string of attributes to add to the element.
     *
     * @return string              a string with the openign tag for the element with attribibutes added.
     */
    private function linkmod_element_open( $linkmod_type, $attributes = '' ) {
      $output = '';
      if ( 'dropdown-item-text' === $linkmod_type ) {
        $output .= '<span class="dropdown-item-text"' . $attributes . '>';
      } elseif ( 'dropdown-header' === $linkmod_type ) {
        // For a header use a span with the .h6 class instead of a real
        // header tag so that it doesn't confuse screen readers.
        $output .= '<span class="dropdown-header h6"' . $attributes . '>';
      } elseif ( 'dropdown-divider' === $linkmod_type ) {
        // this is a divider.
        $output .= '<div class="dropdown-divider"' . $attributes . '>';
      }
      return $output;
    }

    /**
     * Return the correct closing tag for the linkmod element.
     *
     * @since 4.0.0
     *
     * @param string $linkmod_type a string containing a special linkmod type.
     *
     * @return string              a string with the closing tag for this linkmod type.
     */
    private function linkmod_element_close( $linkmod_type ) {
      $output = '';
      if ( 'dropdown-header' === $linkmod_type || 'dropdown-item-text' === $linkmod_type ) {
        // For a header use a span with the .h6 class instead of a real
        // header tag so that it doesn't confuse screen readers.
        $output .= '</span>';
      } elseif ( 'dropdown-divider' === $linkmod_type ) {
        // this is a divider.
        $output .= '</div>';
      }
      return $output;
    }
  }
}