<?php
/**
* WP_Navigation_Fallback class
*
* Manages fallback behavior for Navigation menus.
*
* @package WordPress
* @subpackage Navigation
* @since 6.3.0
*/

/**
* Manages fallback behavior for Navigation menus.
*
* @access public
* @since 6.3.0
*/
class WP_Navigation_Fallback {

/**
* Updates the wp_navigation custom post type schema, in order to expose
* additional fields in the embeddable links of WP_REST_Navigation_Fallback_Controller.
*
* The Navigation Fallback endpoint may embed the full Navigation Menu object
* into the response as the `self` link. By default, the Posts Controller
* will only expose a limited subset of fields but the editor requires
* additional fields to be available in order to utilize the menu.
*
* Used with the `rest_wp_navigation_item_schema` hook.
*
* @since 6.4.0
*
* @param array $schema The schema for the `wp_navigation` post.
* @return array The modified schema.
*/
public static function update_wp_navigation_post_schema( $schema ) {
// Expose top level fields.
$schema['properties']['status']['context'] = array_merge( $schema['properties']['status']['context'], array( 'embed' ) );
$schema['properties']['content']['context'] = array_merge( $schema['properties']['content']['context'], array( 'embed' ) );

/*
* Exposes sub properties of content field.
* These sub properties aren't exposed by the posts controller by default,
* for requests where context is `embed`.
*
* @see WP_REST_Posts_Controller::get_item_schema()
*/
$schema['properties']['content']['properties']['raw']['context'] = array_merge( $schema['properties']['content']['properties']['raw']['context'], array( 'embed' ) );
$schema['properties']['content']['properties']['rendered']['context'] = array_merge( $schema['properties']['content']['properties']['rendered']['context'], array( 'embed' ) );
$schema['properties']['content']['properties']['block_version']['context'] = array_merge( $schema['properties']['content']['properties']['block_version']['context'], array( 'embed' ) );

/*
* Exposes sub properties of title field.
* These sub properties aren't exposed by the posts controller by default,
* for requests where context is `embed`.
*
* @see WP_REST_Posts_Controller::get_item_schema()
*/
$schema['properties']['title']['properties']['raw']['context'] = array_merge( $schema['properties']['title']['properties']['raw']['context'], array( 'embed' ) );

return $schema;
}

/**
* Gets (and/or creates) an appropriate fallback Navigation Menu.
*
* @since 6.3.0
*
* @return WP_Post|null the fallback Navigation Post or null.
*/
public static function get_fallback() {
/**
* Filters whether or not a fallback should be created.
*
* @since 6.3.0
*
* @param bool $create Whether to create a fallback navigation menu. Default true.
*/
$should_create_fallback = apply_filters( 'wp_navigation_should_create_fallback', true );

$fallback = static::get_most_recently_published_navigation();

if ( $fallback || ! $should_create_fallback ) {
return $fallback;
}

$fallback = static::create_classic_menu_fallback();

if ( $fallback && ! is_wp_error( $fallback ) ) {
// Return the newly created fallback post object which will now be the most recently created navigation menu.
return $fallback instanceof WP_Post ? $fallback : static::get_most_recently_published_navigation();
}

$fallback = static::create_default_fallback();

if ( $fallback && ! is_wp_error( $fallback ) ) {
// Return the newly created fallback post object which will now be the most recently created navigation menu.
return $fallback instanceof WP_Post ? $fallback : static::get_most_recently_published_navigation();
}

return null;
}

/**
* Finds the most recently published `wp_navigation` post type.
*
* @since 6.3.0
*
* @return WP_Post|null the first non-empty Navigation or null.
*/
private static function get_most_recently_published_navigation() {

$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,
);

$navigation_post = new WP_Query( $parsed_args );

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

return null;
}

/**
* Creates a Navigation Menu post from a Classic Menu.
*
* @since 6.3.0
*
* @return int|WP_Error The post ID of the default fallback menu or a WP_Error object.
*/
private static function create_classic_menu_fallback() {
// See if we have a classic menu.
$classic_nav_menu = static::get_fallback_classic_menu();

if ( ! $classic_nav_menu ) {
return new WP_Error( 'no_classic_menus', __( 'No Classic Menus found.' ) );
}

// If there is a classic menu then convert it to blocks.
$classic_nav_menu_blocks = WP_Classic_To_Block_Menu_Converter::convert( $classic_nav_menu );

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

if ( empty( $classic_nav_menu_blocks ) ) {
return new WP_Error( 'cannot_convert_classic_menu', __( 'Unable to convert Classic Menu to blocks.' ) );
}

// Create a new navigation menu from the classic menu.
$classic_menu_fallback = 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.
);

return $classic_menu_fallback;
}

/**
* Determines the most appropriate classic navigation menu to use as a fallback.
*
* @since 6.3.0
*
* @return WP_Term|null The most appropriate classic navigation menu to use as a fallback.
*/
private static function get_fallback_classic_menu() {
$classic_nav_menus = wp_get_nav_menus();

if ( ! $classic_nav_menus || is_wp_error( $classic_nav_menus ) ) {
return null;
}

$nav_menu = static::get_nav_menu_at_primary_location();

if ( $nav_menu ) {
return $nav_menu;
}

$nav_menu = static::get_nav_menu_with_primary_slug( $classic_nav_menus );

if ( $nav_menu ) {
return $nav_menu;
}

return static::get_most_recently_created_nav_menu( $classic_nav_menus );
}


/**
* Sorts the classic menus and returns the most recently created one.
*
* @since 6.3.0
*
* @param WP_Term[] $classic_nav_menus Array of classic nav menu term objects.
* @return WP_Term The most recently created classic nav menu.
*/
private static function get_most_recently_created_nav_menu( $classic_nav_menus ) {
usort(
$classic_nav_menus,
static function ( $a, $b ) {
return $b->term_id - $a->term_id;
}
);

return $classic_nav_menus[0];
}

/**
* Returns the classic menu with the slug `primary` if it exists.
*
* @since 6.3.0
*
* @param WP_Term[] $classic_nav_menus Array of classic nav menu term objects.
* @return WP_Term|null The classic nav menu with the slug `primary` or null.
*/
private static function get_nav_menu_with_primary_slug( $classic_nav_menus ) {
foreach ( $classic_nav_menus as $classic_nav_menu ) {
if ( 'primary' === $classic_nav_menu->slug ) {
return $classic_nav_menu;
}
}

return null;
}


/**
* Gets the classic menu assigned to the `primary` navigation menu location
* if it exists.
*
* @since 6.3.0
*
* @return WP_Term|null The classic nav menu assigned to the `primary` location or null.
*/
private static function get_nav_menu_at_primary_location() {
$locations = get_nav_menu_locations();

if ( isset( $locations['primary'] ) ) {
$primary_menu = wp_get_nav_menu_object( $locations['primary'] );

if ( $primary_menu ) {
return $primary_menu;
}
}

return null;
}

/**
* Creates a default Navigation Block Menu fallback.
*
* @since 6.3.0
*
* @return int|WP_Error The post ID of the default fallback menu or a WP_Error object.
*/
private static function create_default_fallback() {

$default_blocks = static::get_default_fallback_blocks();

// Create a new navigation menu from the fallback blocks.
$default_fallback = wp_insert_post(
array(
'post_content' => $default_blocks,
'post_title' => _x( 'Navigation', 'Title of a Navigation menu' ),
'post_name' => 'navigation',
'post_status' => 'publish',
'post_type' => 'wp_navigation',
),
true // So that we can check whether the result is an error.
);

return $default_fallback;
}

/**
* Gets the rendered markup for the default fallback blocks.
*
* @since 6.3.0
*
* @return string default blocks markup to use a the fallback.
*/
private static function get_default_fallback_blocks() {
$registry = WP_Block_Type_Registry::get_instance();

// If `core/page-list` is not registered then use empty blocks.
return $registry->is_registered( 'core/page-list' ) ? '<!-- wp:page-list /-->' : '';
}
}