App\Http\Controllers\DocumentController::getPreview PHP Method

    public function getPreview(DocumentRequest $request)
    {
        $document = $request->entity();
        if (empty($document->preview)) {
            return Response::view('error', ['error' => 'Preview does not exist!'], 404);
        }
        $direct_url = $document->getDirectPreviewUrl();
        if ($direct_url) {
            return redirect($direct_url);
        }
        $previewType = pathinfo($document->preview, PATHINFO_EXTENSION);
        $response = Response::make($document->getRawPreview(), 200);
        $response->header('content-type', Document::$types[$previewType]['mime']);
        return $response;
    }