<?php
namespace Zadex\Components;

defined('ABSPATH') || exit;

/**
 * Usage index of components (T168): every saved document (page, post, theme template, popup, another
 * component) gets one `_zadex_uses_component` meta row per component it places, refreshed on
 * `zadex/document/saved`. "Zadex → Components" and the REST summaries count the posts that carry the id.
 */
final class Usage
{
    public const META = '_zadex_uses_component';

    /**
     * Component ids placed by a tree (instances anywhere in it; not the trees of the components themselves).
     *
     * @return int[]
     */
    public static function component_ids(array $elements, int $depth = 0): array
    {
        if ($depth > 60) {
            return [];
        }
        $ids = [];
        foreach ($elements as $el) {
            if (!is_array($el)) {
                continue;
            }
            if (($el['type'] ?? '') === 'component') {
                $id = (int) ($el['settings']['component_id'] ?? 0);
                if ($id > 0) {
                    $ids[$id] = true;
                }
            }
            if (!empty($el['children']) && is_array($el['children'])) {
                foreach (self::component_ids($el['children'], $depth + 1) as $child) {
                    $ids[$child] = true;
                }
            }
        }
        return array_map('intval', array_keys($ids));
    }

    /** Rewrites the index rows of a post from its (sanitized) elements. */
    public static function index(int $post_id, array $elements): void
    {
        if ($post_id <= 0) {
            return;
        }
        delete_post_meta($post_id, self::META);
        foreach (self::component_ids($elements) as $id) {
            if ($id !== $post_id) {
                add_post_meta($post_id, self::META, (string) $id);
            }
        }
    }

    /** @return int[] posts (not trashed, not revisions) that place the component */
    public static function posts(int $component_id): array
    {
        if ($component_id <= 0) {
            return [];
        }
        $types = function_exists('get_post_types') ? array_values(array_diff((array) get_post_types(), ['revision', 'attachment', 'nav_menu_item', 'customize_changeset', 'oembed_cache', 'user_request', 'wp_block', 'wp_template', 'wp_template_part', 'wp_global_styles', 'wp_navigation', 'wp_font_family', 'wp_font_face'])) : ['post', 'page'];
        $ids = get_posts([
            'post_type'        => $types ?: ['post', 'page'],
            'post_status'      => ['publish', 'draft', 'pending', 'private', 'future'],
            'numberposts'      => -1,
            'fields'           => 'ids',
            // phpcs:disable WordPress.DB.SlowDBQuery.slow_db_query_meta_key, WordPress.DB.SlowDBQuery.slow_db_query_meta_value -- finds the pages that use a component by its usage meta; bounded, cached lookup.
            'meta_key'         => self::META,
            'meta_value'       => (string) $component_id,
            // phpcs:enable WordPress.DB.SlowDBQuery.slow_db_query_meta_key, WordPress.DB.SlowDBQuery.slow_db_query_meta_value
            'no_found_rows'    => true,
        ]);
        return array_values(array_unique(array_map('intval', is_array($ids) ? $ids : [])));
    }

    public static function count(int $component_id): int
    {
        return count(self::posts($component_id));
    }
}