protected function getFacetNamesWithConfiguredField(array $allFacets)
    {
        $facets = [];

        foreach ($allFacets as $facetName => $facetConfiguration) {
            $facetName = substr($facetName, 0, -1);

            if (empty($facetConfiguration['field'])) {
                // TODO later check for query and date, too
                continue;
            }

            $facets[] = $facetName;
        }

        return $facets;
    }