public function onGetSidebarThumbnail()
    {
        $path = Input::get('path');
        $lastModified = Input::get('lastModified');

        $thumbnailParams = $this->getThumbnailParams();
        $thumbnailParams['width'] = 300;
        $thumbnailParams['height'] = 255;
        $thumbnailParams['mode'] = 'auto';

        $path = MediaLibrary::validatePath($path);

        if (!is_numeric($lastModified)) {
            throw new ApplicationException('Invalid input data');
        }

        /*
         * If the thumbnail file exists, just return the thumbnail markup,
         * otherwise generate a new thumbnail.
         */
        $thumbnailPath = $this->thumbnailExists($thumbnailParams, $path, $lastModified);
        if ($thumbnailPath) {
            return [
                'markup' => $this->makePartial('thumbnail-image', [
                    'isError' => $this->thumbnailIsError($thumbnailPath),
                    'imageUrl' => $this->getThumbnailImageUrl($thumbnailPath)
                ])
            ];
        }

        $thumbnailInfo = $thumbnailParams;
        $thumbnailInfo['path'] = $path;
        $thumbnailInfo['lastModified'] = $lastModified;
        $thumbnailInfo['id'] = 'sidebar-thumbnail';

        return $this->generateThumbnail($thumbnailInfo, $thumbnailParams, true);
    }