<?php
/**
 * Server-side rendering of the `core/navigation` block.
 *
 * @package WordPress
 */

/**
 * Helper functions used to render the navigation block.
 */
class WP_Navigation_Block_Renderer {
	/**
	 * Used to determine which blocks are wrapped in an <li>.
	 *
	 * @var array
	 */
	private static $nav_blocks_wrapped_in_list_item = array(
		'core/navigation-link',
		'core/home-link',
		'core/site-title',
		'core/site-logo',
		'core/navigation-submenu',
	);

	/**
	 * Used to determine which blocks need an <li> wrapper.
	 *
	 * @var array
	 */
	private static $needs_list_item_wrapper = array(
		'core/site-title',
		'core/site-logo',
	);

	/**
	 * Keeps track of all the navigation names that have been seen.
	 *
	 * @var array
	 */
	private static $seen_menu_names = array();

	/**
	 * Returns whether or not this is responsive navigation.
	 *
	 * @param array $attributes The block attributes.
	 * @return bool Returns whether or not this is responsive navigation.
	 */
	private static function is_responsive( $attributes ) {
		/**
		 * This is for backwards compatibility after the `isResponsive` attribute was been removed.
		 */

		$has_old_responsive_attribute = ! empty( $attributes['isResponsive'] ) && $attributes['isResponsive'];
		return isset( $attributes['overlayMenu'] ) && 'never' !== $attributes['overlayMenu'] || $has_old_responsive_attribute;
	}

	/**
	 * Returns whether or not a navigation has a submenu.
	 *
	 * @param WP_Block_List $inner_blocks The list of inner blocks.
	 * @return bool Returns whether or not a navigation has a submenu.
	 */
	private static function has_submenus( $inner_blocks ) {
		foreach ( $inner_blocks as $inner_block ) {
			$inner_block_content = $inner_block->render();
			$p                   = new WP_HTML_Tag_Processor( $inner_block_content );
			if ( $p->next_tag(
				array(
					'name'       => 'LI',
					'class_name' => 'has-child',
				)
			) ) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Determine whether the navigation blocks is interactive.
	 *
	 * @param array         $attributes   The block attributes.
	 * @param WP_Block_List $inner_blocks The list of inner blocks.
	 * @return bool Returns whether or not to load the view script.
	 */
	private static function is_interactive( $attributes, $inner_blocks ) {
		$has_submenus       = static::has_submenus( $inner_blocks );
		$is_responsive_menu = static::is_responsive( $attributes );
		return ( $has_submenus && ( $attributes['openSubmenusOnClick'] || $attributes['showSubmenuIcon'] ) ) || $is_responsive_menu;
	}

	/**
	 * Returns whether or not a block needs a list item wrapper.
	 *
	 * @param WP_Block $block The block.
	 * @return bool Returns whether or not a block needs a list item wrapper.
	 */
	private static function does_block_need_a_list_item_wrapper( $block ) {
		return in_array( $block->name, static::$needs_list_item_wrapper, true );
	}

	/**
	 * Returns the markup for a single inner block.
	 *
	 * @param WP_Block $inner_block The inner block.
	 * @return string Returns the markup for a single inner block.
	 */
	private static function get_markup_for_inner_block( $inner_block ) {
		$inner_block_content = $inner_block->render();
		if ( ! empty( $inner_block_content ) ) {
			if ( static::does_block_need_a_list_item_wrapper( $inner_block ) ) {
				return '<li class="wp-block-navigation-item">' . $inner_block_content . '</li>';
			}

			return $inner_block_content;
		}
	}

	/**
	 * Returns the html for the inner blocks of the navigation block.
	 *
	 * @param array         $attributes   The block attributes.
	 * @param WP_Block_List $inner_blocks The list of inner blocks.
	 * @return string Returns the html for the inner blocks of the navigation block.
	 */
	private static function get_inner_blocks_html( $attributes, $inner_blocks ) {
		$has_submenus   = static::has_submenus( $inner_blocks );
		$is_interactive = static::is_interactive( $attributes, $inner_blocks );

		$style                = static::get_styles( $attributes );
		$class                = static::get_classes( $attributes );
		$container_attributes = get_block_wrapper_attributes(
			array(
				'class' => 'wp-block-navigation__container ' . $class,
				'style' => $style,
			)
		);

		$inner_blocks_html = '';
		$is_list_open      = false;

		foreach ( $inner_blocks as $inner_block ) {
			$is_list_item = in_array( $inner_block->name, static::$nav_blocks_wrapped_in_list_item, true );

			if ( $is_list_item && ! $is_list_open ) {
				$is_list_open       = true;
				$inner_blocks_html .= sprintf(
					'<ul %1$s>',
					$container_attributes
				);
			}

			if ( ! $is_list_item && $is_list_open ) {
				$is_list_open       = false;
				$inner_blocks_html .= '</ul>';
			}

			$inner_blocks_html .= static::get_markup_for_inner_block( $inner_block );
		}

		if ( $is_list_open ) {
			$inner_blocks_html .= '</ul>';
		}

		// Add directives to the submenu if needed.
		if ( $has_submenus && $is_interactive ) {
			$tags              = new WP_HTML_Tag_Processor( $inner_blocks_html );
			$inner_blocks_html = block_core_navigation_add_directives_to_submenu( $tags, $attributes );
		}

		return $inner_blocks_html;
	}

	/**
	 * Gets the inner blocks for the navigation block from the navigation post.
	 *
	 * @param array $attributes The block attributes.
	 * @return WP_Block_List Returns the inner blocks for the navigation block.
	 */
	private static function get_inner_blocks_from_navigation_post( $attributes ) {
		$navigation_post = get_post( $attributes['ref'] );
		if ( ! isset( $navigation_post ) ) {
			return new WP_Block_List( array(), $attributes );
		}

		// Only published posts are valid. If this is changed then a corresponding change
		// must also be implemented in `use-navigation-menu.js`.
		if ( 'publish' === $navigation_post->post_status ) {
			$parsed_blocks = parse_blocks( $navigation_post->post_content );

			// 'parse_blocks' includes a null block with '\n\n' as the content when
			// it encounters whitespace. This code strips it.
			$blocks = block_core_navigation_filter_out_empty_blocks( $parsed_blocks );

			if ( function_exists( 'get_hooked_block_markup' ) ) {
				// Run Block Hooks algorithm to inject hooked blocks.
				$markup         = block_core_navigation_insert_hooked_blocks( $blocks, $navigation_post );
				$root_nav_block = parse_blocks( $markup )[0];

				$blocks = isset( $root_nav_block['innerBlocks'] ) ? $root_nav_block['innerBlocks'] : $blocks;
			}

			// TODO - this uses the full navigation block attributes for the
			// context which could be refined.
			return new WP_Block_List( $blocks, $attributes );
		}
	}

	/**
	 * Gets the inner blocks for the navigation block from the fallback.
	 *
	 * @param array $attributes The block attributes.
	 * @return WP_Block_List Returns the inner blocks for the navigation block.
	 */
	private static function get_inner_blocks_from_fallback( $attributes ) {
		$fallback_blocks = block_core_navigation_get_fallback_blocks();

		// Fallback my have been filtered so do basic test for validity.
		if ( empty( $fallback_blocks ) || ! is_array( $fallback_blocks ) ) {
			return new WP_Block_List( array(), $attributes );
		}

		return new WP_Block_List( $fallback_blocks, $attributes );
	}

	/**
	 * Gets the inner blocks for the navigation block.
	 *
	 * @param array    $attributes The block attributes.
	 * @param WP_Block $block The parsed block.
	 * @return WP_Block_List Returns the inner blocks for the navigation block.
	 */
	private static function get_inner_blocks( $attributes, $block ) {
		$inner_blocks = $block->inner_blocks;

		// Ensure that blocks saved with the legacy ref attribute name (navigationMenuId) continue to render.
		if ( array_key_exists( 'navigationMenuId', $attributes ) ) {
			$attributes['ref'] = $attributes['navigationMenuId'];
		}

		// If:
		// - the gutenberg plugin is active
		// - `__unstableLocation` is defined
		// - we have menu items at the defined location
		// - we don't have a relationship to a `wp_navigation` Post (via `ref`).
		// ...then create inner blocks from the classic menu assigned to that location.
		if (
			defined( 'IS_GUTENBERG_PLUGIN' ) && IS_GUTENBERG_PLUGIN &&
			array_key_exists( '__unstableLocation', $attributes ) &&
			! array_key_exists( 'ref', $attributes ) &&
			! empty( block_core_navigation_get_menu_items_at_location( $attributes['__unstableLocation'] ) )
		) {
			$inner_blocks = block_core_navigation_get_inner_blocks_from_unstable_location( $attributes );
		}

		// Load inner blocks from the navigation post.
		if ( array_key_exists( 'ref', $attributes ) ) {
			$inner_blocks = static::get_inner_blocks_from_navigation_post( $attributes );
		}

		// If there are no inner blocks then fallback to rendering an appropriate fallback.
		if ( empty( $inner_blocks ) ) {
			$inner_blocks = static::get_inner_blocks_from_fallback( $attributes );
		}

		/**
		 * Filter navigation block $inner_blocks.
		 * Allows modification of a navigation block menu items.
		 *
		 * @since 6.1.0
		 *
		 * @param \WP_Block_List $inner_blocks
		 */
		$inner_blocks = apply_filters( 'block_core_navigation_render_inner_blocks', $inner_blocks );

		$post_ids = block_core_navigation_get_post_ids( $inner_blocks );
		if ( $post_ids ) {
			_prime_post_caches( $post_ids, false, false );
		}

		return $inner_blocks;
	}

	/**
	 * Gets the name of the current navigation, if it has one.
	 *
	 * @param array $attributes The block attributes.
	 * @return string Returns the name of the navigation.
	 */
	private static function get_navigation_name( $attributes ) {

		$navigation_name = $attributes['ariaLabel'] ?? '';

		// Load the navigation post.
		if ( array_key_exists( 'ref', $attributes ) ) {
			$navigation_post = get_post( $attributes['ref'] );
			if ( ! isset( $navigation_post ) ) {
				return $navigation_name;
			}

			// Only published posts are valid. If this is changed then a corresponding change
			// must also be implemented in `use-navigation-menu.js`.
			if ( 'publish' === $navigation_post->post_status ) {
				$navigation_name = $navigation_post->post_title;

				// This is used to count the number of times a navigation name has been seen,
				// so that we can ensure every navigation has a unique id.
				if ( isset( static::$seen_menu_names[ $navigation_name ] ) ) {
					++static::$seen_menu_names[ $navigation_name ];
				} else {
					static::$seen_menu_names[ $navigation_name ] = 1;
				}
			}
		}

		return $navigation_name;
	}

	/**
	 * Returns the layout class for the navigation block.
	 *
	 * @param array $attributes The block attributes.
	 * @return string Returns the layout class for the navigation block.
	 */
	private static function get_layout_class( $attributes ) {
		$layout_justification = array(
			'left'          => 'items-justified-left',
			'right'         => 'items-justified-right',
			'center'        => 'items-justified-center',
			'space-between' => 'items-justified-space-between',
		);

		$layout_class = '';
		if (
			isset( $attributes['layout']['justifyContent'] ) &&
			isset( $layout_justification[ $attributes['layout']['justifyContent'] ] )
		) {
			$layout_class .= $layout_justification[ $attributes['layout']['justifyContent'] ];
		}
		if ( isset( $attributes['layout']['orientation'] ) && 'vertical' === $attributes['layout']['orientation'] ) {
			$layout_class .= ' is-vertical';
		}

		if ( isset( $attributes['layout']['flexWrap'] ) && 'nowrap' === $attributes['layout']['flexWrap'] ) {
			$layout_class .= ' no-wrap';
		}
		return $layout_class;
	}

	/**
	 * Return classes for the navigation block.
	 *
	 * @param array $attributes The block attributes.
	 * @return string Returns the classes for the navigation block.
	 */
	private static function get_classes( $attributes ) {
		// Restore legacy classnames for submenu positioning.
		$layout_class       = static::get_layout_class( $attributes );
		$colors             = block_core_navigation_build_css_colors( $attributes );
		$font_sizes         = block_core_navigation_build_css_font_sizes( $attributes );
		$is_responsive_menu = static::is_responsive( $attributes );

		// Manually add block support text decoration as CSS class.
		$text_decoration       = $attributes['style']['typography']['textDecoration'] ?? null;
		$text_decoration_class = sprintf( 'has-text-decoration-%s', $text_decoration );

		// Sets the is-collapsed class when the navigation is set to always use the overlay.
		// This saves us from needing to do this check in the view.js file (see the collapseNav function).
		$is_collapsed_class = static::is_always_overlay( $attributes ) ? array( 'is-collapsed' ) : array();

		$classes = array_merge(
			$colors['css_classes'],
			$font_sizes['css_classes'],
			$is_responsive_menu ? array( 'is-responsive' ) : array(),
			$layout_class ? array( $layout_class ) : array(),
			$text_decoration ? array( $text_decoration_class ) : array(),
			$is_collapsed_class
		);
		return implode( ' ', $classes );
	}

	private static function is_always_overlay( $attributes ) {
		return isset( $attributes['overlayMenu'] ) && 'always' === $attributes['overlayMenu'];
	}

	/**
	 * Get styles for the navigation block.
	 *
	 * @param array $attributes The block attributes.
	 * @return string Returns the styles for the navigation block.
	 */
	private static function get_styles( $attributes ) {
		$colors       = block_core_navigation_build_css_colors( $attributes );
		$font_sizes   = block_core_navigation_build_css_font_sizes( $attributes );
		$block_styles = isset( $attributes['styles'] ) ? $attributes['styles'] : '';
		return $block_styles . $colors['inline_styles'] . $font_sizes['inline_styles'];
	}

	/**
	 * Get the responsive container markup
	 *
	 * @param array         $attributes The block attributes.
	 * @param WP_Block_List $inner_blocks The list of inner blocks.
	 * @param string        $inner_blocks_html The markup for the inner blocks.
	 * @return string Returns the container markup.
	 */
	private static function get_responsive_container_markup( $attributes, $inner_blocks, $inner_blocks_html ) {
		$is_interactive  = static::is_interactive( $attributes, $inner_blocks );
		$colors          = block_core_navigation_build_css_colors( $attributes );
		$modal_unique_id = wp_unique_id( 'modal-' );

		$responsive_container_classes = array(
			'wp-block-navigation__responsive-container',
			implode( ' ', $colors['overlay_css_classes'] ),
		);
		$open_button_classes          = array(
			'wp-block-navigation__responsive-container-open',
		);

		$should_display_icon_label = isset( $attributes['hasIcon'] ) && true === $attributes['hasIcon'];
		$toggle_button_icon        = '<svg width="24" height="24" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" aria-hidden="true" focusable="false"><rect x="4" y="7.5" width="16" height="1.5" /><rect x="4" y="15" width="16" height="1.5" /></svg>';
		if ( isset( $attributes['icon'] ) ) {
			if ( 'menu' === $attributes['icon'] ) {
				$toggle_button_icon = '<svg width="24" height="24" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M5 5v1.5h14V5H5zm0 7.8h14v-1.5H5v1.5zM5 19h14v-1.5H5V19z" /></svg>';
			}
		}
		$toggle_button_content       = $should_display_icon_label ? $toggle_button_icon : __( 'Menu' );
		$toggle_close_button_icon    = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" width="24" height="24" aria-hidden="true" focusable="false"><path d="M13 11.8l6.1-6.3-1-1-6.1 6.2-6.1-6.2-1 1 6.1 6.3-6.5 6.7 1 1 6.5-6.6 6.5 6.6 1-1z"></path></svg>';
		$toggle_close_button_content = $should_display_icon_label ? $toggle_close_button_icon : __( 'Close' );
		$toggle_aria_label_open      = $should_display_icon_label ? 'aria-label="' . __( 'Open menu' ) . '"' : ''; // Open button label.
		$toggle_aria_label_close     = $should_display_icon_label ? 'aria-label="' . __( 'Close menu' ) . '"' : ''; // Close button label.

		// Add Interactivity API directives to the markup if needed.
		$open_button_directives          = '';
		$responsive_container_directives = '';
		$responsive_dialog_directives    = '';
		$close_button_directives         = '';
		if ( $is_interactive ) {
			$open_button_directives                  = '
				data-wp-on--click="actions.openMenuOnClick"
				data-wp-on--keydown="actions.handleMenuKeydown"
			';
			$responsive_container_directives         = '
				data-wp-class--has-modal-open="state.isMenuOpen"
				data-wp-class--is-menu-open="state.isMenuOpen"
				data-wp-watch="callbacks.initMenu"
				data-wp-on--keydown="actions.handleMenuKeydown"
				data-wp-on--focusout="actions.handleMenuFocusout"
				tabindex="-1"
			';
			$responsive_dialog_directives            = '
				data-wp-bind--aria-modal="state.ariaModal"
				data-wp-bind--aria-label="state.ariaLabel"
				data-wp-bind--role="state.roleAttribute"
			';
			$close_button_directives                 = '
				data-wp-on--click="actions.closeMenuOnClick"
			';
			$responsive_container_content_directives = '
				data-wp-watch="callbacks.focusFirstElement"
			';
		}

		return sprintf(
			'<button aria-haspopup="dialog" %3$s class="%6$s" %10$s>%8$s</button>
				<div class="%5$s" style="%7$s" id="%1$s" %11$s>
					<div class="wp-block-navigation__responsive-close" tabindex="-1">
						<div class="wp-block-navigation__responsive-dialog" %12$s>
							<button %4$s class="wp-block-navigation__responsive-container-close" %13$s>%9$s</button>
							<div class="wp-block-navigation__responsive-container-content" %14$s id="%1$s-content">
								%2$s
							</div>
						</div>
					</div>
				</div>',
			esc_attr( $modal_unique_id ),
			$inner_blocks_html,
			$toggle_aria_label_open,
			$toggle_aria_label_close,
			esc_attr( implode( ' ', $responsive_container_classes ) ),
			esc_attr( implode( ' ', $open_button_classes ) ),
			esc_attr( safecss_filter_attr( $colors['overlay_inline_styles'] ) ),
			$toggle_button_content,
			$toggle_close_button_content,
			$open_button_directives,
			$responsive_container_directives,
			$responsive_dialog_directives,
			$close_button_directives,
			$responsive_container_content_directives
		);
	}

	/**
	 * Get the wrapper attributes
	 *
	 * @param array         $attributes    The block attributes.
	 * @param WP_Block_List $inner_blocks  A list of inner blocks.
	 * @return string Returns the navigation block markup.
	 */
	private static function get_nav_wrapper_attributes( $attributes, $inner_blocks ) {
		$nav_menu_name      = static::get_unique_navigation_name( $attributes );
		$is_interactive     = static::is_interactive( $attributes, $inner_blocks );
		$is_responsive_menu = static::is_responsive( $attributes );
		$style              = static::get_styles( $attributes );
		$class              = static::get_classes( $attributes );
		$wrapper_attributes = get_block_wrapper_attributes(
			array(
				'class'      => $class,
				'style'      => $style,
				'aria-label' => $nav_menu_name,
			)
		);

		if ( $is_responsive_menu ) {
			$nav_element_directives = static::get_nav_element_directives( $is_interactive, $attributes );
			$wrapper_attributes    .= ' ' . $nav_element_directives;
		}

		return $wrapper_attributes;
	}

	/**
	 * Gets the nav element directives.
	 *
	 * @param bool  $is_interactive Whether the block is interactive.
	 * @param array $attributes     The block attributes.
	 * @return string the directives for the navigation element.
	 */
	private static function get_nav_element_directives( $is_interactive, $attributes ) {
		if ( ! $is_interactive ) {
			return '';
		}
		// When adding to this array be mindful of security concerns.
		$nav_element_context    = wp_json_encode(
			array(
				'overlayOpenedBy' => array(),
				'type'            => 'overlay',
				'roleAttribute'   => '',
				'ariaLabel'       => __( 'Menu' ),
			),
			JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_AMP
		);
		$nav_element_directives = '
			data-wp-interactive=\'{"namespace":"core/navigation"}\'
			data-wp-context=\'' . $nav_element_context . '\'
		';

		/*
		* When the navigation's 'overlayMenu' attribute is set to 'always', JavaScript
		* is not needed for collapsing the menu because the class is set manually.
		*/
		if ( ! static::is_always_overlay( $attributes ) ) {
			$nav_element_directives .= 'data-wp-init="callbacks.initNav"';
			$nav_element_directives .= ' '; // space separator
			$nav_element_directives .= 'data-wp-class--is-collapsed="context.isCollapsed"';
		}

		return $nav_element_directives;
	}

	/**
	 * Handle view script module loading.
	 *
	 * @param array         $attributes   The block attributes.
	 * @param WP_Block      $block        The parsed block.
	 * @param WP_Block_List $inner_blocks The list of inner blocks.
	 */
	private static function handle_view_script_module_loading( $attributes, $block, $inner_blocks ) {
		if ( static::is_interactive( $attributes, $inner_blocks ) ) {
			wp_enqueue_script_module( '@wordpress/block-library/navigation' );
		}
	}

	/**
	 * Returns the markup for the navigation block.
	 *
	 * @param array         $attributes The block attributes.
	 * @param WP_Block_List $inner_blocks The list of inner blocks.
	 * @return string Returns the navigation wrapper markup.
	 */
	private static function get_wrapper_markup( $attributes, $inner_blocks ) {
		$inner_blocks_html = static::get_inner_blocks_html( $attributes, $inner_blocks );
		if ( static::is_responsive( $attributes ) ) {
			return static::get_responsive_container_markup( $attributes, $inner_blocks, $inner_blocks_html );
		}
		return $inner_blocks_html;
	}

	/**
	 * Returns a unique name for the navigation.
	 *
	 * @param array $attributes The block attributes.
	 * @return string Returns a unique name for the navigation.
	 */
	private static function get_unique_navigation_name( $attributes ) {
		$nav_menu_name = static::get_navigation_name( $attributes );

		// If the menu name has been used previously then append an ID
		// to the name to ensure uniqueness across a given post.
		if ( isset( static::$seen_menu_names[ $nav_menu_name ] ) && static::$seen_menu_names[ $nav_menu_name ] > 1 ) {
			$count         = static::$seen_menu_names[ $nav_menu_name ];
			$nav_menu_name = $nav_menu_name . ' ' . ( $count );
		}

		return $nav_menu_name;
	}

	/**
	 * Renders the navigation block.
	 *
	 * @param array    $attributes The block attributes.
	 * @param string   $content    The saved content.
	 * @param WP_Block $block      The parsed block.
	 * @return string Returns the navigation block markup.
	 */
	public static function render( $attributes, $content, $block ) {
		/**
		 * Deprecated:
		 * The rgbTextColor and rgbBackgroundColor attributes
		 * have been deprecated in favor of
		 * customTextColor and customBackgroundColor ones.
		 * Move the values from old attrs to the new ones.
		 */
		if ( isset( $attributes['rgbTextColor'] ) && empty( $attributes['textColor'] ) ) {
			$attributes['customTextColor'] = $attributes['rgbTextColor'];
		}

		if ( isset( $attributes['rgbBackgroundColor'] ) && empty( $attributes['backgroundColor'] ) ) {
			$attributes['customBackgroundColor'] = $attributes['rgbBackgroundColor'];
		}

		unset( $attributes['rgbTextColor'], $attributes['rgbBackgroundColor'] );

		$inner_blocks = static::get_inner_blocks( $attributes, $block );
		// Prevent navigation blocks referencing themselves from rendering.
		if ( block_core_navigation_block_contains_core_navigation( $inner_blocks ) ) {
			return '';
		}

		static::handle_view_script_module_loading( $attributes, $block, $inner_blocks );

		return sprintf(
			'<nav %1$s>%2$s</nav>',
			static::get_nav_wrapper_attributes( $attributes, $inner_blocks ),
			static::get_wrapper_markup( $attributes, $inner_blocks )
		);
	}
}

// These functions are used for the __unstableLocation feature and only active
// when the gutenberg plugin is active.
if ( defined( 'IS_GUTENBERG_PLUGIN' ) && IS_GUTENBERG_PLUGIN ) {
	/**
	 * Returns the menu items for a WordPress menu location.
	 *
	 * @param string $location The menu location.
	 * @return array Menu items for the location.
	 */
	function block_core_navigation_get_menu_items_at_location( $location ) {
		if ( empty( $location ) ) {
			return;
		}

		// Build menu data. The following approximates the code in
		// `wp_nav_menu()` and `gutenberg_output_block_nav_menu`.

		// Find the location in the list of locations, returning early if the
		// location can't be found.
		$locations = get_nav_menu_locations();
		if ( ! isset( $locations[ $location ] ) ) {
			return;
		}

		// Get the menu from the location, returning early if there is no
		// menu or there was an error.
		$menu = wp_get_nav_menu_object( $locations[ $location ] );
		if ( ! $menu || is_wp_error( $menu ) ) {
			return;
		}

		$menu_items = wp_get_nav_menu_items( $menu->term_id, array( 'update_post_term_cache' => false ) );
		_wp_menu_item_classes_by_context( $menu_items );

		return $menu_items;
	}


	/**
	 * Sorts a standard array of menu items into a nested structure keyed by the
	 * id of the parent menu.
	 *
	 * @param array $menu_items Menu items to sort.
	 * @return array An array keyed by the id of the parent menu where each element
	 *               is an array of menu items that belong to that parent.
	 */
	function block_core_navigation_sort_menu_items_by_parent_id( $menu_items ) {
		$sorted_menu_items = array();
		foreach ( (array) $menu_items as $menu_item ) {
			$sorted_menu_items[ $menu_item->menu_order ] = $menu_item;
		}
		unset( $menu_items, $menu_item );

		$menu_items_by_parent_id = array();
		foreach ( $sorted_menu_items as $menu_item ) {
			$menu_items_by_parent_id[ $menu_item->menu_item_parent ][] = $menu_item;
		}

		return $menu_items_by_parent_id;
	}

	/**
	 * Gets the inner blocks for the navigation block from the unstable location attribute.
	 *
	 * @param array $attributes The block attributes.
	 * @return WP_Block_List Returns the inner blocks for the navigation block.
	 */
	function block_core_navigation_get_inner_blocks_from_unstable_location( $attributes ) {
		$menu_items = block_core_navigation_get_menu_items_at_location( $attributes['__unstableLocation'] );
		if ( empty( $menu_items ) ) {
			return new WP_Block_List( array(), $attributes );
		}

		$menu_items_by_parent_id = block_core_navigation_sort_menu_items_by_parent_id( $menu_items );
		$parsed_blocks           = block_core_navigation_parse_blocks_from_menu_items( $menu_items_by_parent_id[0], $menu_items_by_parent_id );
		return new WP_Block_List( $parsed_blocks, $attributes );
	}
}

/**
 * Add Interactivity API directives to the navigation-submenu and page-list
 * blocks markup using the Tag Processor.
 *
 * @param WP_HTML_Tag_Processor $tags             Markup of the navigation block.
 * @param array                 $block_attributes Block attributes.
 *
 * @return string Submenu markup with the directives injected.
 */
function block_core_navigation_add_directives_to_submenu( $tags, $block_attributes ) {
	while ( $tags->next_tag(
		array(
			'tag_name'   => 'LI',
			'class_name' => 'has-child',
		)
	) ) {
		// Add directives to the parent `<li>`.
		$tags->set_attribute( 'data-wp-interactive', '{ "namespace": "core/navigation" }' );
		$tags->set_attribute( 'data-wp-context', '{ "submenuOpenedBy": {}, "type": "submenu" }' );
		$tags->set_attribute( 'data-wp-watch', 'callbacks.initMenu' );
		$tags->set_attribute( 'data-wp-on--focusout', 'actions.handleMenuFocusout' );
		$tags->set_attribute( 'data-wp-on--keydown', 'actions.handleMenuKeydown' );

		// This is a fix for Safari. Without it, Safari doesn't change the active
		// element when the user clicks on a button. It can be removed once we add
		// an overlay to capture the clicks, instead of relying on the focusout
		// event.
		$tags->set_attribute( 'tabindex', '-1' );

		if ( ! isset( $block_attributes['openSubmenusOnClick'] ) || false === $block_attributes['openSubmenusOnClick'] ) {
			$tags->set_attribute( 'data-wp-on--mouseenter', 'actions.openMenuOnHover' );
			$tags->set_attribute( 'data-wp-on--mouseleave', 'actions.closeMenuOnHover' );
		}

		// Add directives to the toggle submenu button.
		if ( $tags->next_tag(
			array(
				'tag_name'   => 'BUTTON',
				'class_name' => 'wp-block-navigation-submenu__toggle',
			)
		) ) {
			$tags->set_attribute( 'data-wp-on--click', 'actions.toggleMenuOnClick' );
			$tags->set_attribute( 'data-wp-bind--aria-expanded', 'state.isMenuOpen' );
			// The `aria-expanded` attribute for SSR is already added in the submenu block.
		}
		// Add directives to the submenu.
		if ( $tags->next_tag(
			array(
				'tag_name'   => 'UL',
				'class_name' => 'wp-block-navigation__submenu-container',
			)
		) ) {
			$tags->set_attribute( 'data-wp-on--focus', 'actions.openMenuOnFocus' );
		}

		// Iterate through subitems if exist.
		block_core_navigation_add_directives_to_submenu( $tags, $block_attributes );
	}
	return $tags->get_updated_html();
}

/**
 * Build an array with CSS classes and inline styles defining the colors
 * which will be applied to the navigation markup in the front-end.
 *
 * @param array $attributes Navigation block attributes.
 *
 * @return array Colors CSS classes and inline styles.
 */
function block_core_navigation_build_css_colors( $attributes ) {
	$colors = array(
		'css_classes'           => array(),
		'inline_styles'         => '',
		'overlay_css_classes'   => array(),
		'overlay_inline_styles' => '',
	);

	// Text color.
	$has_named_text_color  = array_key_exists( 'textColor', $attributes );
	$has_custom_text_color = array_key_exists( 'customTextColor', $attributes );

	// If has text color.
	if ( $has_custom_text_color || $has_named_text_color ) {
		// Add has-text-color class.
		$colors['css_classes'][] = 'has-text-color';
	}

	if ( $has_named_text_color ) {
		// Add the color class.
		$colors['css_classes'][] = sprintf( 'has-%s-color', $attributes['textColor'] );
	} elseif ( $has_custom_text_color ) {
		// Add the custom color inline style.
		$colors['inline_styles'] .= sprintf( 'color: %s;', $attributes['customTextColor'] );
	}

	// Background color.
	$has_named_background_color  = array_key_exists( 'backgroundColor', $attributes );
	$has_custom_background_color = array_key_exists( 'customBackgroundColor', $attributes );

	// If has background color.
	if ( $has_custom_background_color || $has_named_background_color ) {
		// Add has-background class.
		$colors['css_classes'][] = 'has-background';
	}

	if ( $has_named_background_color ) {
		// Add the background-color class.
		$colors['css_classes'][] = sprintf( 'has-%s-background-color', $attributes['backgroundColor'] );
	} elseif ( $has_custom_background_color ) {
		// Add the custom background-color inline style.
		$colors['inline_styles'] .= sprintf( 'background-color: %s;', $attributes['customBackgroundColor'] );
	}

	// Overlay text color.
	$has_named_overlay_text_color  = array_key_exists( 'overlayTextColor', $attributes );
	$has_custom_overlay_text_color = array_key_exists( 'customOverlayTextColor', $attributes );

	// If has overlay text color.
	if ( $has_custom_overlay_text_color || $has_named_overlay_text_color ) {
		// Add has-text-color class.
		$colors['overlay_css_classes'][] = 'has-text-color';
	}

	if ( $has_named_overlay_text_color ) {
		// Add the overlay color class.
		$colors['overlay_css_classes'][] = sprintf( 'has-%s-color', $attributes['overlayTextColor'] );
	} elseif ( $has_custom_overlay_text_color ) {
		// Add the custom overlay color inline style.
		$colors['overlay_inline_styles'] .= sprintf( 'color: %s;', $attributes['customOverlayTextColor'] );
	}

	// Overlay background color.
	$has_named_overlay_background_color  = array_key_exists( 'overlayBackgroundColor', $attributes );
	$has_custom_overlay_background_color = array_key_exists( 'customOverlayBackgroundColor', $attributes );

	// If has overlay background color.
	if ( $has_custom_overlay_background_color || $has_named_overlay_background_color ) {
		// Add has-background class.
		$colors['overlay_css_classes'][] = 'has-background';
	}

	if ( $has_named_overlay_background_color ) {
		// Add the overlay background-color class.
		$colors['overlay_css_classes'][] = sprintf( 'has-%s-background-color', $attributes['overlayBackgroundColor'] );
	} elseif ( $has_custom_overlay_background_color ) {
		// Add the custom overlay background-color inline style.
		$colors['overlay_inline_styles'] .= sprintf( 'background-color: %s;', $attributes['customOverlayBackgroundColor'] );
	}

	return $colors;
}

/**
 * Build an array with CSS classes and inline styles defining the font sizes
 * which will be applied to the navigation markup in the front-end.
 *
 * @param array $attributes Navigation block attributes.
 *
 * @return array Font size CSS classes and inline styles.
 */
function block_core_navigation_build_css_font_sizes( $attributes ) {
	// CSS classes.
	$font_sizes = array(
		'css_classes'   => array(),
		'inline_styles' => '',
	);

	$has_named_font_size  = array_key_exists( 'fontSize', $attributes );
	$has_custom_font_size = array_key_exists( 'customFontSize', $attributes );

	if ( $has_named_font_size ) {
		// Add the font size class.
		$font_sizes['css_classes'][] = sprintf( 'has-%s-font-size', $attributes['fontSize'] );
	} elseif ( $has_custom_font_size ) {
		// Add the custom font size inline style.
		$font_sizes['inline_styles'] = sprintf( 'font-size: %spx;', $attributes['customFontSize'] );
	}

	return $font_sizes;
}

/**
 * Returns the top-level submenu SVG chevron icon.
 *
 * @return string
 */
function block_core_navigation_render_submenu_icon() {
	return '<svg xmlns="http://www.w3.org/2000/svg" width="12" height="12" viewBox="0 0 12 12" fill="none" aria-hidden="true" focusable="false"><path d="M1.50002 4L6.00002 8L10.5 4" stroke-width="1.5"></path></svg>';
}

/**
 * Filter out empty "null" blocks from the block list.
 * 'parse_blocks' includes a null block with '\n\n' as the content when
 * it encounters whitespace. This is not a bug but rather how the parser
 * is designed.
 *
 * @param array $parsed_blocks the parsed blocks to be normalized.
 * @return array the normalized parsed blocks.
 */
function block_core_navigation_filter_out_empty_blocks( $parsed_blocks ) {
	$filtered = array_filter(
		$parsed_blocks,
		static function ( $block ) {
			return isset( $block['blockName'] );
		}
	);

	// Reset keys.
	return array_values( $filtered );
}

/**
 * Returns true if the navigation block contains a nested navigation block.
 *
 * @param WP_Block_List $inner_blocks Inner block instance to be normalized.
 * @return bool true if the navigation block contains a nested navigation block.
 */
function block_core_navigation_block_contains_core_navigation( $inner_blocks ) {
	foreach ( $inner_blocks as $block ) {
		if ( 'core/navigation' === $block->name ) {
			return true;
		}
		if ( $block->inner_blocks && block_core_navigation_block_contains_core_navigation( $block->inner_blocks ) ) {
			return true;
		}
	}

	return false;
}

/**
 * Retrieves the appropriate fallback to be used on the front of the
 * site when there is no menu assigned to the Nav block.
 *
 * This aims to mirror how the fallback mechanic for wp_nav_menu works.
 * See https://developer.wordpress.org/reference/functions/wp_nav_menu/#more-information.
 *
 * @return array the array of blocks to be used as a fallback.
 */
function block_core_navigation_get_fallback_blocks() {
	$page_list_fallback = array(
		array(
			'blockName' => 'core/page-list',
		),
	);

	$registry = WP_Block_Type_Registry::get_instance();

	// If `core/page-list` is not registered then return empty blocks.
	$fallback_blocks = $registry->is_registered( 'core/page-list' ) ? $page_list_fallback : array();

	if ( class_exists( 'WP_Navigation_Fallback' ) ) {
		$navigation_post = WP_Navigation_Fallback::get_fallback();
	} else {
		$navigation_post = Gutenberg_Navigation_Fallback::get_fallback();
	}

	// Use the first non-empty Navigation as fallback if available.
	if ( $navigation_post ) {
		$parsed_blocks  = parse_blocks( $navigation_post->post_content );
		$maybe_fallback = block_core_navigation_filter_out_empty_blocks( $parsed_blocks );

		// Normalizing blocks may result in an empty array of blocks if they were all `null` blocks.
		// In this case default to the (Page List) fallback.
		$fallback_blocks = ! empty( $maybe_fallback ) ? $maybe_fallback : $fallback_blocks;

		if ( function_exists( 'get_hooked_block_markup' ) ) {
			// Run Block Hooks algorithm to inject hooked blocks.
			// We have to run it here because we need the post ID of the Navigation block to track ignored hooked blocks.
			$markup = block_core_navigation_insert_hooked_blocks( $fallback_blocks, $navigation_post );
			$blocks = parse_blocks( $markup );

			if ( isset( $blocks[0]['innerBlocks'] ) ) {
				$fallback_blocks = $blocks[0]['innerBlocks'];
			}
		}
	}

	/**
	 * Filters the fallback experience for the Navigation block.
	 *
	 * Returning a falsey value will opt out of the fallback and cause the block not to render.
	 * To customise the blocks provided return an array of blocks - these should be valid
	 * children of the `core/navigation` block.
	 *
	 * @since 5.9.0
	 *
	 * @param array[] $fallback_blocks default fallback blocks provided by the default block mechanic.
	 */
	return apply_filters( 'block_core_navigation_render_fallback', $fallback_blocks );
}

/**
 * Iterate through all inner blocks recursively and get navigation link block's post IDs.
 *
 * @param WP_Block_List $inner_blocks Block list class instance.
 *
 * @return array Array of post IDs.
 */
function block_core_navigation_get_post_ids( $inner_blocks ) {
	$post_ids = array_map( 'block_core_navigation_from_block_get_post_ids', iterator_to_array( $inner_blocks ) );
	return array_unique( array_merge( ...$post_ids ) );
}

/**
 * Get post IDs from a navigation link block instance.
 *
 * @param WP_Block $block Instance of a block.
 *
 * @return array Array of post IDs.
 */
function block_core_navigation_from_block_get_post_ids( $block ) {
	$post_ids = array();

	if ( $block->inner_blocks ) {
		$post_ids = block_core_navigation_get_post_ids( $block->inner_blocks );
	}

	if ( 'core/navigation-link' === $block->name || 'core/navigation-submenu' === $block->name ) {
		if ( $block->attributes && isset( $block->attributes['kind'] ) && 'post-type' === $block->attributes['kind'] && isset( $block->attributes['id'] ) ) {
			$post_ids[] = $block->attributes['id'];
		}
	}

	return $post_ids;
}

/**
 * Renders the `core/navigation` block on server.
 *
 * @param array    $attributes The block attributes.
 * @param string   $content    The saved content.
 * @param WP_Block $block      The parsed block.
 *
 * @return string Returns the navigation block markup.
 */
function render_block_core_navigation( $attributes, $content, $block ) {
	return WP_Navigation_Block_Renderer::render( $attributes, $content, $block );
}

/**
 * Register the navigation block.
 *
 * @uses render_block_core_navigation()
 * @throws WP_Error An WP_Error exception parsing the block definition.
 */
function register_block_core_navigation() {
	register_block_type_from_metadata(
		__DIR__ . '/navigation',
		array(
			'render_callback' => 'render_block_core_navigation',
		)
	);

	wp_register_script_module(
		'@wordpress/block-library/navigation',
		defined( 'IS_GUTENBERG_PLUGIN' ) && IS_GUTENBERG_PLUGIN ? gutenberg_url( '/build/interactivity/navigation.min.js' ) : includes_url( 'blocks/navigation/view.min.js' ),
		array( '@wordpress/interactivity' ),
		defined( 'GUTENBERG_VERSION' ) ? GUTENBERG_VERSION : get_bloginfo( 'version' )
	);
}

add_action( 'init', 'register_block_core_navigation' );

/**
 * Filter that changes the parsed attribute values of navigation blocks contain typographic presets to contain the values directly.
 *
 * @param array $parsed_block The block being rendered.
 *
 * @return array The block being rendered without typographic presets.
 */
function block_core_navigation_typographic_presets_backcompatibility( $parsed_block ) {
	if ( 'core/navigation' === $parsed_block['blockName'] ) {
		$attribute_to_prefix_map = array(
			'fontStyle'      => 'var:preset|font-style|',
			'fontWeight'     => 'var:preset|font-weight|',
			'textDecoration' => 'var:preset|text-decoration|',
			'textTransform'  => 'var:preset|text-transform|',
		);
		foreach ( $attribute_to_prefix_map as $style_attribute => $prefix ) {
			if ( ! empty( $parsed_block['attrs']['style']['typography'][ $style_attribute ] ) ) {
				$prefix_len      = strlen( $prefix );
				$attribute_value = &$parsed_block['attrs']['style']['typography'][ $style_attribute ];
				if ( 0 === strncmp( $attribute_value, $prefix, $prefix_len ) ) {
					$attribute_value = substr( $attribute_value, $prefix_len );
				}
				if ( 'textDecoration' === $style_attribute && 'strikethrough' === $attribute_value ) {
					$attribute_value = 'line-through';
				}
			}
		}
	}

	return $parsed_block;
}

add_filter( 'render_block_data', 'block_core_navigation_typographic_presets_backcompatibility' );

/**
 * Turns menu item data into a nested array of parsed blocks
 *
 * @deprecated 6.3.0 Use WP_Navigation_Fallback::parse_blocks_from_menu_items() instead.
 *
 * @param array $menu_items               An array of menu items that represent
 *                                        an individual level of a menu.
 * @param array $menu_items_by_parent_id  An array keyed by the id of the
 *                                        parent menu where each element is an
 *                                        array of menu items that belong to
 *                                        that parent.
 * @return array An array of parsed block data.
 */
function block_core_navigation_parse_blocks_from_menu_items( $menu_items, $menu_items_by_parent_id ) {

	_deprecated_function( __FUNCTION__, '6.3.0', 'WP_Navigation_Fallback::parse_blocks_from_menu_items' );

	if ( empty( $menu_items ) ) {
		return array();
	}

	$blocks = array();

	foreach ( $menu_items as $menu_item ) {
		$class_name       = ! empty( $menu_item->classes ) ? implode( ' ', (array) $menu_item->classes ) : null;
		$id               = ( null !== $menu_item->object_id && 'custom' !== $menu_item->object ) ? $menu_item->object_id : null;
		$opens_in_new_tab = null !== $menu_item->target && '_blank' === $menu_item->target;
		$rel              = ( null !== $menu_item->xfn && '' !== $menu_item->xfn ) ? $menu_item->xfn : null;
		$kind             = null !== $menu_item->type ? str_replace( '_', '-', $menu_item->type ) : 'custom';

		$block = array(
			'blockName' => isset( $menu_items_by_parent_id[ $menu_item->ID ] ) ? 'core/navigation-submenu' : 'core/navigation-link',
			'attrs'     => array(
				'className'     => $class_name,
				'description'   => $menu_item->description,
				'id'            => $id,
				'kind'          => $kind,
				'label'         => $menu_item->title,
				'opensInNewTab' => $opens_in_new_tab,
				'rel'           => $rel,
				'title'         => $menu_item->attr_title,
				'type'          => $menu_item->object,
				'url'           => $menu_item->url,
			),
		);

		$block['innerBlocks']  = isset( $menu_items_by_parent_id[ $menu_item->ID ] )
			? block_core_navigation_parse_blocks_from_menu_items( $menu_items_by_parent_id[ $menu_item->ID ], $menu_items_by_parent_id )
			: array();
		$block['innerContent'] = array_map( 'serialize_block', $block['innerBlocks'] );

		$blocks[] = $block;
	}

	return $blocks;
}

/**
 * Get the classic navigation menu to use as a fallback.
 *
 * @deprecated 6.3.0 Use WP_Navigation_Fallback::get_classic_menu_fallback() instead.
 *
 * @return object WP_Term The classic navigation.
 */
function block_core_navigation_get_classic_menu_fallback() {

	_deprecated_function( __FUNCTION__, '6.3.0', 'WP_Navigation_Fallback::get_classic_menu_fallback' );

	$classic_nav_menus = wp_get_nav_menus();

	// If menus exist.
	if ( $classic_nav_menus && ! is_wp_error( $classic_nav_menus ) ) {
		// Handles simple use case where user has a classic menu and switches to a block theme.

		// Returns the menu assigned to location `primary`.
		$locations = get_nav_menu_locations();
		if ( isset( $locations['primary'] ) ) {
			$primary_menu = wp_get_nav_menu_object( $locations['primary'] );
			if ( $primary_menu ) {
				return $primary_menu;
			}
		}

		// Returns a menu if `primary` is its slug.
		foreach ( $classic_nav_menus as $classic_nav_menu ) {
			if ( 'primary' === $classic_nav_menu->slug ) {
				return $classic_nav_menu;
			}
		}

		// Otherwise return the most recently created classic menu.
		usort(
			$classic_nav_menus,
			static function ( $a, $b ) {
				return $b->term_id - $a->term_id;
			}
		);
		return $classic_nav_menus[0];
	}
}

/**
 * Converts a classic navigation to blocks.
 *
 * @deprecated 6.3.0 Use WP_Navigation_Fallback::get_classic_menu_fallback_blocks() instead.
 *
 * @param  object $classic_nav_menu WP_Term The classic navigation object to convert.
 * @return array the normalized parsed blocks.
 */
function block_core_navigation_get_classic_menu_fallback_blocks( $classic_nav_menu ) {

	_deprecated_function( __FUNCTION__, '6.3.0', 'WP_Navigation_Fallback::get_classic_menu_fallback_blocks' );

	// BEGIN: Code that already exists in wp_nav_menu().
	$menu_items = wp_get_nav_menu_items( $classic_nav_menu->term_id, array( 'update_post_term_cache' => false ) );

	// Set up the $menu_item variables.
	_wp_menu_item_classes_by_context( $menu_items );

	$sorted_menu_items = array();
	foreach ( (array) $menu_items as $menu_item ) {
		$sorted_menu_items[ $menu_item->menu_order ] = $menu_item;
	}

	unset( $menu_items, $menu_item );

	// END: Code that already exists in wp_nav_menu().

	$menu_items_by_parent_id = array();
	foreach ( $sorted_menu_items as $menu_item ) {
		$menu_items_by_parent_id[ $menu_item->menu_item_parent ][] = $menu_item;
	}

	$inner_blocks = block_core_navigation_parse_blocks_from_menu_items(
		isset( $menu_items_by_parent_id[0] )
			? $menu_items_by_parent_id[0]
			: array(),
		$menu_items_by_parent_id
	);

	return serialize_blocks( $inner_blocks );
}

/**
 * If there's a classic menu then use it as a fallback.
 *
 * @deprecated 6.3.0 Use WP_Navigation_Fallback::create_classic_menu_fallback() instead.
 *
 * @return array the normalized parsed blocks.
 */
function block_core_navigation_maybe_use_classic_menu_fallback() {

	_deprecated_function( __FUNCTION__, '6.3.0', 'WP_Navigation_Fallback::create_classic_menu_fallback' );

	// See if we have a classic menu.
	$classic_nav_menu = block_core_navigation_get_classic_menu_fallback();

	if ( ! $classic_nav_menu ) {
		return;
	}

	// If we have a classic menu then convert it to blocks.
	$classic_nav_menu_blocks = block_core_navigation_get_classic_menu_fallback_blocks( $classic_nav_menu );

	if ( empty( $classic_nav_menu_blocks ) ) {
		return;
	}

	// Create a new navigation menu from the classic menu.
	$wp_insert_post_result = wp_insert_post(
		array(
			'post_content' => $classic_nav_menu_blocks,
			'post_title'   => $classic_nav_menu->name,
			'post_name'    => $classic_nav_menu->slug,
			'post_status'  => 'publish',
			'post_type'    => 'wp_navigation',
		),
		true // So that we can check whether the result is an error.
	);

	if ( is_wp_error( $wp_insert_post_result ) ) {
		return;
	}

	// Fetch the most recently published navigation which will be the classic one created above.
	return block_core_navigation_get_most_recently_published_navigation();
}

/**
 * Finds the most recently published `wp_navigation` Post.
 *
 * @deprecated 6.3.0 Use WP_Navigation_Fallback::get_most_recently_published_navigation() instead.
 *
 * @return WP_Post|null the first non-empty Navigation or null.
 */
function block_core_navigation_get_most_recently_published_navigation() {

	_deprecated_function( __FUNCTION__, '6.3.0', 'WP_Navigation_Fallback::get_most_recently_published_navigation' );

	// Default to the most recently created menu.
	$parsed_args = array(
		'post_type'              => 'wp_navigation',
		'no_found_rows'          => true,
		'update_post_meta_cache' => false,
		'update_post_term_cache' => false,
		'order'                  => 'DESC',
		'orderby'                => 'date',
		'post_status'            => 'publish',
		'posts_per_page'         => 1, // get only the most recent.
	);

	$navigation_post = new WP_Query( $parsed_args );
	if ( count( $navigation_post->posts ) > 0 ) {
		return $navigation_post->posts[0];
	}

	return null;
}

/**
 * Insert hooked blocks into a Navigation block.
 *
 * Given a Navigation block's inner blocks and its corresponding `wp_navigation` post object,
 * this function inserts hooked blocks into it, and returns the serialized inner blocks in a
 * mock Navigation block wrapper.
 *
 * If there are any hooked blocks that need to be inserted as the Navigation block's first or last
 * children, the `wp_navigation` post's `_wp_ignored_hooked_blocks` meta is checked to see if any
 * of those hooked blocks should be exempted from insertion.
 *
 * @param array   $inner_blocks Parsed inner blocks of a Navigation block.
 * @param WP_Post $post         `wp_navigation` post object corresponding to the block.
 * @return string Serialized inner blocks in mock Navigation block wrapper, with hooked blocks inserted, if any.
 */
function block_core_navigation_insert_hooked_blocks( $inner_blocks, $post ) {
	$before_block_visitor = null;
	$after_block_visitor  = null;
	$hooked_blocks        = get_hooked_blocks();
	$attributes           = array();

	if ( isset( $post->ID ) ) {
		$ignored_hooked_blocks = get_post_meta( $post->ID, '_wp_ignored_hooked_blocks', true );
		if ( ! empty( $ignored_hooked_blocks ) ) {
			$ignored_hooked_blocks  = json_decode( $ignored_hooked_blocks, true );
			$attributes['metadata'] = array(
				'ignoredHookedBlocks' => $ignored_hooked_blocks,
			);
		}
	}

	$mock_anchor_parent_block = array(
		'blockName'    => 'core/navigation',
		'attrs'        => $attributes,
		'innerBlocks'  => $inner_blocks,
		'innerContent' => array_fill( 0, count( $inner_blocks ), null ),
	);
	$before_block_visitor     = null;
	$after_block_visitor      = null;

	if ( ! empty( $hooked_blocks ) || has_filter( 'hooked_block_types' ) ) {
		$before_block_visitor = make_before_block_visitor( $hooked_blocks, $post );
		$after_block_visitor  = make_after_block_visitor( $hooked_blocks, $post );
	}

	return traverse_and_serialize_block( $mock_anchor_parent_block, $before_block_visitor, $after_block_visitor );
}

/**
 * Updates the post meta with the list of ignored hooked blocks when the navigation is created or updated via the REST API.
 *
 * @param WP_Post $post Post object.
 */
function block_core_navigation_update_ignore_hooked_blocks_meta( $post ) {
	// We run the Block Hooks mechanism so it will return the list of ignored hooked blocks
	// in the mock root Navigation block's metadata attribute.
	// We ignore the rest of the returned `$markup`; `$post->post_content` already has the hooked
	// blocks inserted, whereas `$markup` will have them inserted twice.
	$blocks                = parse_blocks( $post->post_content );
	$markup                = block_core_navigation_insert_hooked_blocks( $blocks, $post );
	$root_nav_block        = parse_blocks( $markup )[0];
	$ignored_hooked_blocks = isset( $root_nav_block['attrs']['metadata']['ignoredHookedBlocks'] )
		? $root_nav_block['attrs']['metadata']['ignoredHookedBlocks']
		: array();

	if ( ! empty( $ignored_hooked_blocks ) ) {
		$existing_ignored_hooked_blocks = get_post_meta( $post->ID, '_wp_ignored_hooked_blocks', true );
		if ( ! empty( $existing_ignored_hooked_blocks ) ) {
			$existing_ignored_hooked_blocks = json_decode( $existing_ignored_hooked_blocks, true );
			$ignored_hooked_blocks          = array_unique( array_merge( $ignored_hooked_blocks, $existing_ignored_hooked_blocks ) );
		}
		update_post_meta( $post->ID, '_wp_ignored_hooked_blocks', json_encode( $ignored_hooked_blocks ) );
	}
}

// Injection of hooked blocks into the Navigation block relies on some functions present in WP >= 6.5
// that are not present in Gutenberg's WP 6.5 compatibility layer.
if ( function_exists( 'get_hooked_block_markup' ) ) {
	add_action( 'rest_insert_wp_navigation', 'block_core_navigation_update_ignore_hooked_blocks_meta', 10, 3 );
}

/**
 * Hooks into the REST API response for the core/navigation block and adds the first and last inner blocks.
 *
 * @param WP_REST_Response $response The response object.
 * @param WP_Post          $post     Post object.
 * @param WP_REST_Request  $request  Request object.
 * @return WP_REST_Response The response object.
 */
function block_core_navigation_insert_hooked_blocks_into_rest_response( $response, $post ) {
	if ( ! isset( $response->data['content']['raw'] ) || ! isset( $response->data['content']['rendered'] ) ) {
		return $response;
	}
	$parsed_blocks = parse_blocks( $response->data['content']['raw'] );
	$content       = block_core_navigation_insert_hooked_blocks( $parsed_blocks, $post );

	// Remove mock Navigation block wrapper.
	$start   = strpos( $content, '-->' ) + strlen( '-->' );
	$end     = strrpos( $content, '<!--' );
	$content = substr( $content, $start, $end - $start );

	$response->data['content']['raw']      = $content;
	$response->data['content']['rendered'] = apply_filters( 'the_content', $content );

	return $response;
}

// Injection of hooked blocks into the Navigation block relies on some functions present in WP >= 6.5
// that are not present in Gutenberg's WP 6.5 compatibility layer.
if ( function_exists( 'get_hooked_block_markup' ) ) {
	add_filter( 'rest_prepare_wp_navigation', 'block_core_navigation_insert_hooked_blocks_into_rest_response', 10, 3 );
}