public function addSynonymsAction(string $baseWord, string $synonyms, $overrideExisting)
    {
        if (empty($baseWord) || empty($synonyms)) {
            $this->addFlashMessage(
                'Please provide a base word and synonyms.',
                'Missing parameter',
                FlashMessage::ERROR
            );
        } else {
            $baseWord = mb_strtolower($baseWord);
            $synonyms = mb_strtolower($synonyms);

            $coreAdmin = $this->selectedSolrCoreConnection->getAdminService();
            if ($overrideExisting && $coreAdmin->getSynonyms($baseWord)) {
                $coreAdmin->deleteSynonym($baseWord);
            }
            $coreAdmin->addSynonym($baseWord, GeneralUtility::trimExplode(',', $synonyms, true));
            $coreAdmin->reloadCore();

            $this->addFlashMessage(
                '"' . $synonyms . '" added as synonyms for base word "' . $baseWord . '"'
            );
        }

        $this->redirect('index');
    }