<?php

namespace AcademicCrew\PageGenerator;

use AcademicCrew\Core\Loader;

/**
 * Keeps the auto-generated member / course / project pages out of navigation.
 *
 * Three layers, because a page can reach a menu several ways:
 *
 *   1. Interception — every `wp_update_nav_menu_item` call (core's auto-add,
 *      a re-import, the menu editor, another plugin) is checked, and an item
 *      that targets a generated page is deleted the instant it is written.
 *   2. Cleanup — belt and braces: any lingering `nav_menu_item` for a generated
 *      page is dropped on the page's own save, right after every import, and
 *      once (per sweep version) for items added before this guard existed. The
 *      initial page insert is already guarded by PageGeneratorBase::create_page().
 *   3. Render-time — generated pages are filtered out of `wp_nav_menu`,
 *      `wp_list_pages`, and `wp_page_menu` output, whatever attached them.
 */
class NavMenuGuard {

    private const FLAGS = [
        '_academiccrew_is_member_page',
        '_academiccrew_is_course_page',
        '_academiccrew_is_collaboration_page',
    ];

    /** Bumped when the sweep logic changes, to force a one-time re-run. */
    private const SWEEP_VERSION = '3';

    /** @var int[]|null */
    private ?array $ids = null;

    public function register( Loader $loader ): void {
        // 1. Interception — reject any menu item pointing at a generated page,
        //    whatever wrote it (core auto-add, a re-import, the menu editor).
        $loader->add_action( 'wp_update_nav_menu_item', $this, 'reject_generated_page_item', 10, 3 );

        // 2. Cleanup.
        $loader->add_action( 'save_post',                  $this, 'purge_after_save', 12, 2 );
        $loader->add_action( 'save_post_academiccrew_member', $this, 'purge_linked_page', 30, 1 );
        $loader->add_action( 'save_post_academiccrew_course', $this, 'purge_linked_page', 30, 1 );
        $loader->add_action( 'save_post_acc_collaboration', $this, 'purge_linked_page', 30, 1 );
        $loader->add_action( 'wp_loaded',                  $this, 'maybe_sweep_all' );

        // 3. Render-time. Only the front-end nav walker (`wp_nav_menu`) and the
        //    page-list fallbacks — NOT `wp_get_nav_menu_items`, which the menu
        //    editor and core's own auto-add dedup rely on.
        $loader->add_filter( 'wp_nav_menu_objects',    $this, 'strip_menu_objects',  10, 1 );
        $loader->add_filter( 'wp_page_menu_args',      $this, 'exclude_from_page_menu' );
        $loader->add_filter( 'wp_list_pages_excludes', $this, 'add_to_excludes' );
        // The Page List block (`core/page-list`), wp_list_pages(), wp_page_menu()
        // and Avada's page-hierarchy fallback all read get_pages() — strip the
        // generated pages there so they never show as menu sub-items.
        $loader->add_filter( 'get_pages',              $this, 'strip_from_page_lists', 10, 2 );

        $loader->add_action( 'academiccrew_generated_page_ids_flush', $this, 'flush' );
    }

    // ── 1. Interception ───────────────────────────────────────────

    /**
     * Fires after every nav-menu item is written. If it targets an
     * auto-generated member / course / project page, delete it immediately —
     * this is what stops a re-import (which regenerates the linked page and
     * re-triggers core's auto-add) from putting the page back in the menu.
     *
     * @param int   $menu_id
     * @param int   $menu_item_db_id
     * @param array $args  processed menu-item args (menu-item-object, -object-id, …)
     */
    public function reject_generated_page_item( $menu_id, $menu_item_db_id, $args = [] ): void {
        $object    = is_array( $args ) ? ( $args['menu-item-object'] ?? '' ) : '';
        $object_id = is_array( $args ) ? (int) ( $args['menu-item-object-id'] ?? 0 ) : 0;

        // Fall back to the stored meta when the args don't carry the object id.
        if ( ! $object_id && $menu_item_db_id ) {
            $object    = (string) get_post_meta( (int) $menu_item_db_id, '_menu_item_object', true );
            $object_id = (int) get_post_meta( (int) $menu_item_db_id, '_menu_item_object_id', true );
        }

        if ( 'page' !== $object || ! $object_id ) {
            return;
        }
        if ( $this->has_flag( $object_id ) || in_array( $object_id, $this->generated_ids(), true ) ) {
            wp_delete_post( (int) $menu_item_db_id, true );
            $this->flush();
        }
    }

    // ── 2. Cleanup ─────────────────────────────────────────────────

    /**
     * Runs after core's auto-add (save_post priority 10): if a generated page
     * still gained a menu item, drop it.
     *
     * @param int      $post_id
     * @param \WP_Post $post
     */
    public function purge_after_save( int $post_id, $post ): void {
        if ( ! ( $post instanceof \WP_Post ) || 'page' !== $post->post_type ) {
            return;
        }
        if ( $this->has_flag( $post_id ) ) {
            $this->delete_menu_items_for( $post_id );
            $this->flush();
        }
    }

    /** Sweep the page linked to a member / course / project that was just saved. */
    public function purge_linked_page( int $cpt_id ): void {
        $page_id = (int) get_post_meta( $cpt_id, '_academiccrew_linked_page_id', true );
        if ( $page_id ) {
            $this->delete_menu_items_for( $page_id );
            $this->flush();
        }
    }

    /** One-time (per SWEEP_VERSION) removal of items added before this guard. */
    public function maybe_sweep_all(): void {
        if ( get_option( 'academiccrew_navmenu_swept' ) === self::SWEEP_VERSION ) {
            return;
        }
        foreach ( $this->generated_ids() as $page_id ) {
            $this->delete_menu_items_for( $page_id );
        }
        $this->flush();
        update_option( 'academiccrew_navmenu_swept', self::SWEEP_VERSION, true );
    }

    private function delete_menu_items_for( int $page_id ): void {
        $items = get_posts( [
            'post_type'      => 'nav_menu_item',
            'post_status'    => 'any',
            'posts_per_page' => -1,
            'fields'         => 'ids',
            'meta_key'       => '_menu_item_object_id',
            'meta_value'     => (string) $page_id,
        ] );
        foreach ( $items as $item_id ) {
            if ( 'nav_menu_item' === get_post_type( (int) $item_id ) ) {
                wp_delete_post( (int) $item_id, true );
            }
        }
    }

    // ── 3. Render-time ─────────────────────────────────────────────

    /**
     * @param array $items array of menu-item objects (each with ->object, ->object_id)
     * @return array
     */
    public function strip_menu_objects( $items ) {
        if ( ! is_array( $items ) ) {
            return $items;
        }
        $ids = $this->generated_ids();
        if ( ! $ids ) {
            return $items;
        }
        return array_values( array_filter( $items, function ( $item ) use ( $ids ) {
            return ! $this->item_targets_generated_page( $item, $ids );
        } ) );
    }

    private function item_targets_generated_page( $item, array $ids ): bool {
        $type   = $item->type   ?? ( $item->menu_item_type ?? '' );
        $object = $item->object ?? ( $item->menu_item_object ?? '' );
        $obj_id = (int) ( $item->object_id ?? ( $item->menu_item_object_id ?? 0 ) );

        return 'post_type' === $type
            && 'page' === $object
            && in_array( $obj_id, $ids, true );
    }

    /**
     * Drop generated pages from every get_pages() result on the front end:
     * the Page List block (`core/page-list`), wp_list_pages(), wp_page_menu()
     * and Avada's page-hierarchy menu fallback all go through here. Left intact
     * in wp-admin so the "Parent page" dropdowns keep working.
     *
     * @param mixed $pages \WP_Post[] or int[] from get_pages()
     * @param array $args
     * @return mixed
     */
    public function strip_from_page_lists( $pages, $args = [] ) {
        if ( is_admin() || ! is_array( $pages ) || ! $pages ) {
            return $pages;
        }
        $ids = $this->generated_ids();
        if ( ! $ids ) {
            return $pages;
        }
        return array_values( array_filter( $pages, static function ( $page ) use ( $ids ) {
            $pid = (int) ( is_object( $page ) ? ( $page->ID ?? 0 ) : $page );
            return ! in_array( $pid, $ids, true );
        } ) );
    }

    public function exclude_from_page_menu( array $args ): array {
        $ids = $this->generated_ids();
        if ( $ids ) {
            $existing        = array_filter( array_map( 'intval', explode( ',', (string) ( $args['exclude'] ?? '' ) ) ) );
            $args['exclude'] = implode( ',', array_unique( array_merge( $existing, $ids ) ) );
        }
        return $args;
    }

    /** @param int[] $excludes */
    public function add_to_excludes( array $excludes ): array {
        return array_values( array_unique( array_merge( $excludes, $this->generated_ids() ) ) );
    }

    // ── Shared ────────────────────────────────────────────────────

    public function flush(): void {
        $this->ids = null;
        delete_transient( 'academiccrew_generated_page_ids' );
    }

    private function has_flag( int $page_id ): bool {
        foreach ( self::FLAGS as $flag ) {
            if ( get_post_meta( $page_id, $flag, true ) ) {
                return true;
            }
        }
        return false;
    }

    /** @return int[] */
    private function generated_ids(): array {
        if ( $this->ids !== null ) {
            return $this->ids;
        }
        $cached = get_transient( 'academiccrew_generated_page_ids' );
        if ( is_array( $cached ) ) {
            return $this->ids = $cached;
        }

        $ids = get_posts( [
            'post_type'      => 'page',
            // Include trash — a trashed generated page can still carry a stale
            // menu item that a re-import would otherwise leave behind.
            'post_status'    => [ 'publish', 'draft', 'pending', 'private', 'future', 'trash' ],
            'posts_per_page' => -1,
            'fields'         => 'ids',
            'meta_query'     => [
                'relation' => 'OR',
                ...array_map( static fn( $f ) => [ 'key' => $f, 'compare' => 'EXISTS' ], self::FLAGS ),
            ],
        ] );
        $ids = array_map( 'intval', $ids );

        set_transient( 'academiccrew_generated_page_ids', $ids, HOUR_IN_SECONDS );
        return $this->ids = $ids;
    }
}