protected function getCacheFilename(string $entryIdentifier): string
    {
        $urlParts = \parse_url($entryIdentifier);
        $parts = [
            $urlParts['scheme'],
            $urlParts['host'],
            isset($urlParts['port']) ? (int)$urlParts['port'] : ('https' === $urlParts['scheme'] ? 443 : 80),
        ];

        $path = \implode('/', $parts) . '/' . \trim($urlParts['path'], '/');
        $cacheFilename = GeneralUtility::getFileAbsFileName(self::CACHE_DIRECTORY . $path);
        $fileExtension = (string)PathUtility::pathinfo(PathUtility::basename($cacheFilename), PATHINFO_EXTENSION);
        if (empty($fileExtension) || !GeneralUtility::inList($this->configuration->get('fileTypes'), $fileExtension)) {
            $cacheFilename = \rtrim($cacheFilename, '/') . '/index.html';
        }

        return $cacheFilename;
    }