private static function getAnchorClass($sortColumn, &$anchorAttributes = [])
    {
        $class = [];

        $anchorClass = config('columnsortable.anchor_class', null);
        if ($anchorClass !== null) {
            $class[] = $anchorClass;
        }

        $activeClass = config('columnsortable.active_anchor_class', null);
        if ($activeClass !== null && self::shouldShowActive($sortColumn)) {
            $class[] = $activeClass;
        }

        $directionClassPrefix = config('columnsortable.direction_anchor_class_prefix', null);
        if ($directionClassPrefix !== null && self::shouldShowActive($sortColumn)) {
            $class[] = $directionClassPrefix.(request()->get('direction') === 'asc' ? config('columnsortable.asc_suffix', '-asc') :
                    config('columnsortable.desc_suffix', '-desc'));
        }

        if (isset($anchorAttributes['class'])) {
            $class = array_merge($class, explode(' ', $anchorAttributes['class']));
            unset($anchorAttributes['class']);
        }

        return (empty($class)) ? '' : ' class="'.implode(' ', $class).'"';
    }