protected function extractFeeds(string $html) : array
    {
        $dom = new \DOMDocument();
        $dom->loadHTML($html);

        $links = $dom->getElementsByTagName('link');
        $feeds = [];
        foreach ($links as $link) {
            if ($this->isFeedLink($link)) {
                $feeds[] = $link->getAttribute('href');
            }
        }

        return $feeds;
    }