public function getAvailableDirective(Request $request)
    {
        if (null === $this->uaParser) {
            return $this->getChromeDirectives();
        }

        switch ($this->uaParser->getBrowser($request->headers->get('user-agent'))) {
            case UserAgentParserInterface::BROWSER_CHROME:
            case UserAgentParserInterface::BROWSER_OPERA:
            case UserAgentParserInterface::BROWSER_OTHER:
                return $this->getChromeDirectives();
            case UserAgentParserInterface::BROWSER_FIREFOX:
                return $this->getFirefoxDirectives();
            case UserAgentParserInterface::BROWSER_SAFARI:
                return $this->getLevel1();
        }
    }