<?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( 'Understrap_WP_Bootstrap_Navwalker' ) ) {
	/**
	 * WP_Bootstrap_Navwalker class.
	 *
	 * @extends Walker_Nav_Menu
	 */
	class Understrap_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', 'understrap' ) . '">' . esc_html__( 'Add a menu', 'understrap' ) . '</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;
		}
	}
}
