* Get the upload directory path.
	 *
	 * @since 1.8.7
	 *
	 * @return string
	 */
	public static function get_upload_dir(): string {

		static $upload_dir;

		if ( $upload_dir ) {
			/**
			 * Since wpforms_upload_dir() relies on hooks, and hooks can be added unpredictably,
			 * we need to cache the result of this method.
			 * Otherwise, it is the risk to save cache file to one dir and try to get from another.
			 */
			return $upload_dir;
		}

		$wpforms_upload_dir  = wpforms_upload_dir();
		$wpforms_upload_path = ! empty( $wpforms_upload_dir['path'] )
			? $wpforms_upload_dir['path']
			: WP_CONTENT_DIR . '/uploads/wpforms';
		$upload_dir          = trailingslashit( wp_normalize_path( $wpforms_upload_path ) );

		return $upload_dir;
	}

	/**
	 * Get the cache directory path.
	 *
	 * @since 1.8.6
	 *
	 * @return string
	 */
	public static function get_cache_dir(): string {

		static $cache_dir;

		if ( $cache_dir ) {
			/**
			 * Since wpforms_upload_dir() relies on hooks, and hooks can be added unpredictably,
			 * we need to cache the result of this method.
			 * Otherwise, it is the risk to save cache file to one dir and try to get from another.
			 */
			return $cache_dir;
		}

		$cache_dir = self::get_upload_dir() . 'cache/';

		return $cache_dir;
	}

	/**
	 * Check whether the file is already updated.
	 *
	 * @since 1.8.7
	 *
	 * @param string $filename  Filename.
	 * @param string $cache_key Cache key.
	 *
	 * @return bool
	 */
	public static function is_file_updated( string $filename, string $cache_key = '' ): bool {

		$filename  = wp_normalize_path( $filename );
		$cache_key = $cache_key ? $cache_key : 'wpforms_' . $filename . '_file';

		if ( ! is_file( $filename ) ) {
			return false;
		}

		$cached_stat = Transient::get( $cache_key );
		$stat        = array_intersect_key(
			stat( $filename ),
			[
				'size'  => 0,
				'mtime' => 0,
				'ctime' => 0,
			]
		);

		if ( $cached_stat === $stat ) {
			return true;
		}

		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged, WordPress.WP.AlternativeFunctions.unlink_unlink
		@unlink( $filename );

		return false;
	}

	/**
	 * Save file updated stat.
	 *
	 * @since 1.8.7
	 *
	 * @param string $filename  Filename.
	 * @param string $cache_key Cache key.
	 *
	 * @return void
	 */
	public static function save_file_updated_stat( string $filename, string $cache_key = '' ) {

		$filename  = wp_normalize_path( $filename );
		$cache_key = $cache_key ? $cache_key : 'wpforms_' . $filename . '_file';

		clearstatcache( true, $filename );

		$stat = array_intersect_key(
			stat( $filename ),
			[
				'size'  => 0,
				'mtime' => 0,
				'ctime' => 0,
			]
		);

		Transient::set( $cache_key, $stat );
	}
}