<?php
/**
 * Sitemaps: WP_Sitemaps_Index class.
 *
 * Generates the sitemap index.
 *
 * @package WordPress
 * @subpackage Sitemaps
 * @since 5.5.0
 */

/**
 * Class WP_Sitemaps_Index.
 * Builds the sitemap index page that lists the links to all of the sitemaps.
 *
 * @since 5.5.0
 */
#[AllowDynamicProperties]
class WP_Sitemaps_Index {
    /**
     * The main registry of supported sitemaps.
     *
     * @since 5.5.0
     * @var WP_Sitemaps_Registry
     */
    protected $registry;

    /**
     * Maximum number of sitemaps to include in an index.
     *
     * @since 5.5.0
     *
     * @var int Maximum number of sitemaps.
     */
    private $max_sitemaps = 50000;

    /**
     * WP_Sitemaps_Index constructor.
     *
     * @since 5.5.0
     *
     * @param WP_Sitemaps_Registry $registry Sitemap provider registry.
     */
    public function __construct( WP_Sitemaps_Registry $registry ) {
        $this->registry = $registry;
    }

    /**
     * Gets a sitemap list for the index.
     *
     * @since 5.5.0
     *
     * @return array[] Array of all sitemaps.
     */
    public function get_sitemap_list() {
        $sitemaps = array();

        $providers = $this->registry->get_providers();
        /* @var WP_Sitemaps_Provider $provider */
        foreach ( $providers as $name => $provider ) {
            $sitemap_entries = $provider->get_sitemap_entries();

            // Prevent issues with array_push and empty arrays on PHP < 7.3.
            if ( ! $sitemap_entries ) {
                continue;
            }

            // Using array_push is more efficient than array_merge in a loop.
            array_push( $sitemaps, ...$sitemap_entries );
            if ( count( $sitemaps ) >= $this->max_sitemaps ) {
                break;
            }
        }

        return array_slice( $sitemaps, 0, $this->max_sitemaps, true );
    }

    /**
     * Builds the URL for the sitemap index.
     *
     * @since 5.5.0
     *
     * @global WP_Rewrite $wp_rewrite WordPress rewrite component.
     *
     * @return string The sitemap index URL.
     */
    public function get_index_url() {
        global $wp_rewrite;

        if ( ! $wp_rewrite->using_permalinks() ) {
            return home_url( '/?sitemap=index' );
        }

        return home_url( '/wp-sitemap.xml' );
    }
}