public function thumbnailURL($size = 'large')
    {
        if (!in_array($size, ['large', 'medium', 'small'])) {
            return false;
        }

        $info = $this->parseLink();
        $service = $this->getService();

        if (!$info || !$service) {
            return false;
        }

        if ($service == 'YouTube') {
            if ($size == 'large') {
                $img = 'hqdefault.jpg';
            } elseif ($size == 'medium') {
                $img = 'mqdefault.jpg';
            } else {
                $img = 'default.jpg';
            }
            return 'https://i.ytimg.com/vi/' . $this->VideoID . '/' . $img;
        }

        if ($service == 'Vimeo') {
            $data = $this->getCachedJsonResponse(
                'https://vimeo.com/api/v2/video/' . $this->VideoID . '.json'
            );

            if (!$data) {
                return false;
            }

            if ($size == 'large' && (!empty($data[0]['thumbnail_large']))) {
                return $data[0]['thumbnail_large'];
            } elseif ($size == 'medium' && (!empty($data[0]['thumbnail_medium']))) {
                return $data[0]['thumbnail_medium'];
            } elseif (!empty($data[0]['thumbnail_small'])) {
                return $data[0]['thumbnail_small'];
            }
        }

        return false;
    }