ject_id   Object id.
	 * @param  string  $object_type Object type. Accetps: post, term, user.
	 * @param  boolean $include     Add or Remove object.
	 */
	public static function exclude_object( $object_id, $object_type, $include ) {
		$field_id = "exclude_{$object_type}s";
		$ids      = Helper::get_settings( 'sitemap.' . $field_id );

		if ( empty( $ids ) ) {
			$ids = $object_id;
		} else {
			$ids = array_filter( wp_parse_id_list( $ids ) );

			// Add object.
			if ( $include && ! in_array( $object_id, $ids, true ) ) {
				$ids[] = $object_id;
			}

			// Remove object.
			if ( ! $include && in_array( $object_id, $ids, true ) ) {
				$ids = array_diff( $ids, [ $object_id ] );
			}

			$ids = implode( ',', $ids );
		}

		$opt = cmb2_options( 'rank-math-options-sitemap' );
		$opt->update( $field_id, $ids, true );
	}

	/**
	 * Get the GMT modification date for the last modified post in the post type.
	 *
	 * @param  string|array $post_types Post type or array of types.
	 * @param  boolean      $return_all Flag to return array of values.
	 * @return string|array|false
	 *
	 * @copyright Copyright (C) 2008-2019, Yoast BV
	 * The following code is a derivative work of the code from the Yoast(https://github.com/Yoast/wordpress-seo/), which is licensed under GPL v3.
	 */
	public static function get_last_modified_gmt( $post_types, $return_all = false ) {
		global $wpdb;

		if ( empty( $post_types ) ) {
			return false;
		}

		static $post_type_dates = null;
		if ( ! is_array( $post_types ) ) {
			$post_types = [ $post_types ];
		}

		foreach ( $post_types as $post_type ) {
			if ( ! isset( $post_type_dates[ $post_type ] ) ) { // If we hadn't seen post type before. R.
				$post_type_dates = null;
				break;
			}
		}

		if ( is_null( $post_type_dates ) ) {
			$post_type_dates = [];
			$post_type_names = get_post_types( [ 'public' => true ] );

			if ( ! empty( $post_type_names ) ) {
				$sql = "
				SELECT post_type, MAX( GREATEST( p.post_modified_gmt, p.post_date_gmt ) ) AS date
				FROM $wpdb->posts as p
				LEFT JOIN {$wpdb->postmeta} AS pm ON ( p.ID = pm.post_id AND pm.meta_key = 'rank_math_robots')
				WHERE (
					( pm.meta_key = 'rank_math_robots' AND pm.meta_value NOT LIKE '%noindex%' ) OR
				    pm.post_id IS NULL
				)
				AND p.post_status IN ( 'publish','inherit' )
					AND p.post_type IN ('" . implode( "','", $post_type_names ) . "')
				GROUP BY p.post_type
				ORDER BY p.post_modified_gmt DESC";

				foreach ( $wpdb->get_results( $sql ) as $obj ) { // phpcs:ignore
					$post_type_dates[ $obj->post_type ] = $obj->date;
				}
			}
		}

		$dates = array_intersect_key( $post_type_dates, array_flip( $post_types ) );
		if ( count( $dates ) > 0 ) {
			return $return_all ? $dates : max( $dates );
		}

		return false;
	}

	/**
	 * Check if cache is enabled.
	 *
	 * @return boolean
	 */
	public static function is_cache_enabled() {
		static $xml_sitemap_caching;
		if ( isset( $xml_sitemap_caching ) ) {
			return $xml_sitemap_caching;
		}

		/**
		 * Filter to enable/disable XML sitemap caching.
		 *
		 * @param boolean $true Enable or disable caching.
		 */
		$xml_sitemap_caching = apply_filters( 'rank_math/sitemap/enable_caching', true );
		return $xml_sitemap_caching;
	}

	/**
	 * Check if `object` is indexable.
	 *
	 * @param int/object $object Post|Term Object.
	 * @param string     $type   Object Type.
	 *
	 * @return boolean
	 */
	public static function is_object_indexable( $object, $type = 'post' ) {
		/**
		 * Filter: 'rank_math/sitemap/include_noindex' - Include noindex data in Sitemap.
		 *
		 * @param bool   $value Whether to include noindex terms in Sitemap.
		 * @param string $type  Object Type.
		 *
		 * @return boolean
		 */
		if ( apply_filters( 'rank_math/sitemap/include_noindex', false, $type ) ) {
			return true;
		}

		$method = 'post' === $type ? 'is_post_indexable' : 'is_term_indexable';

		return Helper::$method( $object );
	}

	/**
	 * Redirect duplicate sitemaps.
	 *
	 * @param int $count       Total number of entries.
	 * @param int $max_entries Entries per sitemap.
	 */
	public static function maybe_redirect( $count, $max_entries ) {
		$current_page = (int) get_query_var( 'sitemap_n' );
		if ( ! $current_page && $count > $max_entries ) {
			Helper::redirect( preg_replace( '/\.xml$/', '1.xml', Helper::get_current_page_url() ) );
			die();
		}

		if ( $count < $max_entries && $current_page ) {
			Helper::redirect( preg_replace( '/' . preg_quote( $current_page ) . '\.xml$/', '.xml', Helper::get_current_page_url() ) );
			die();
		}
	}

	/**
	 * Get the sitemap index slug.
	 */
	public static function get_sitemap_index_slug() {
		/**
		 * Filter: 'rank_math/sitemap/index_slug' - Modify the sitemap index slug.
		 *
		 * @param string $slug Sitemap index slug.
		 *
		 * @return string
		 */
		return apply_filters( 'rank_math/sitemap/index/slug', 'sitemap_index' );
	}
}