WooCommerce Free - Add random character on the filename

if ( class_exists( 'DNDMFU_WC_MAIN' ) ) {
    add_filter( 'wp_unique_filename', function( $file_name, $ext ) {
        $upload_name = dndmfu_wc_get_filename();
        if ( isset( $_POST[ $upload_name ] ) ) {
            $name = pathinfo( $file_name );
            $file_name = $name['filename'] .'-'. mt_rand(1000,9999) .'-'. time() . $ext;
        }
        return $file_name;
    }, 10, 2 );
}