public function verify($id, $receipt)
 {
     $data = $this->decodeReceipt($receipt);
     if (empty($data->receipt) === true || empty($data->userId) === true) {
         throw new NonFatalException('missing receipt or userId');
     }
     $secret = Config::get('amazon.iap.secret');
     $suffix = "/version/2.0/verify/developer/{$secret}/user/{$data->userId}/purchaseToken/{$data->receipt}";
     $url = (Environment::is(Environment::PRODUCTION) ? self::PRODUCTION_API : self::SANDBOX_API) . $suffix;
     $request = new URLRequest($url);
     $response = $request->getJSON(false);
     if (empty($response) === true) {
         throw new Exception('invalid receipt', 400);
     }
     if (empty($response->message) === false) {
         throw new NonFatalException($response->message, $request->lastResponseCode);
     }
     $productId = empty($response->sku) ? null : $response->sku;
     return $id === $productId;
 }