This is kind of over my head, I am successfully created the serverside validation for the subscription but I don’t know where to put it ( From logic perspective ) on my Flutter app.

Now in Flutter, I have to listen to the purchase stream to get purchase details ( token and ..etc ), and here’s the weird part, one below function I get responses under PurchaseStatus.purchased and PurchaseStatus.restored when the purchase has been canceled and expired at the same time.

So the _handleSuccessfullySubscribed(); get’s run!

I have another function for server-side validation but don’t know where to place it in my code without doing an infinite loop here.

void _initiated() async {
  await _subscription?.cancel();

  _subscription = _inAppPurchase.purchaseStream.listen((purchases) async {
    for (final purchase in purchases) {
      switch (purchase.status) {
        case PurchaseStatus.purchased:
        case PurchaseStatus.restored:
          // handle if purchased here
          _handleSuccessfullySubscribed();
          break;

        case PurchaseStatus.pending:
          // handle if pending here
          log('Purchase is pending');
          break;

        case PurchaseStatus.canceled:
          // handle if canceled here
          log('Purchase is canceled');
          break;

        case PurchaseStatus.error:
          // handle if error here
          log('Purchase has an error');
          break;
        default:
      }

      if (purchase.pendingCompletePurchase) {
        await _inAppPurchase.completePurchase(purchase);
      }
    }
  });

  await _inAppPurchase.restorePurchases();
}

The validation function

@override
Future<Either<Failure, Unit>> verifySubscription(
    {required String token, required String productId}) async {
  try {
    final settings = locator<ISettingsRepository>();

    final InternetConnectionChecker connectionChecker =
        InternetConnectionChecker();
    final either = await settings.get();

    either.fold((f) {
      // return left(const Failure(code: FailureCode.unexpected));
    }, (settings) async {
      if (settings.membership == Membership.paid &&
          (await connectionChecker.connectionStatus) ==
              InternetConnectionStatus.connected) {
        await locator<Dio>().post('google-subscriptions/v1/validate', data: {
          "productId": productId,
          "purchaseToken": token,
          "packageName": "app.expamle"
        });
      }
    });

    return right(unit);
  } on DioException catch (_) {
    _handleFailedSubscribed();
    return left(const Failure(code: FailureCode.unexpected));
  }
}

The whole class

class IapRepository extends IIapRepository {
  IapRepository(this._inAppPurchase, this._settingsDAO) {
    _initiated();
  }

  final InAppPurchase _inAppPurchase;
  final SettingsDAO _settingsDAO;

  StreamSubscription<void>? _subscription;

  void _initiated() async {
    await _subscription?.cancel();

    _subscription = _inAppPurchase.purchaseStream.listen((purchases) async {
      for (final purchase in purchases) {
        switch (purchase.status) {
          case PurchaseStatus.purchased:
          case PurchaseStatus.restored:
            // handle if purchased here
            log(''' Purchase details: 
productID ${purchase.productID}
purchaseID ${purchase.purchaseID}
status ${purchase.status}
transactionDate ${purchase.transactionDate}
verificationData ${purchase.verificationData.localVerificationData} - ${purchase.verificationData.serverVerificationData} - ${purchase.verificationData.source}

''');

            _handleSuccessfullySubscribed();
            break;

          case PurchaseStatus.pending:
            // handle if pending here
            log('Purchase is pending');
            break;

          case PurchaseStatus.canceled:
            // handle if canceled here
            log('Purchase is canceled');
            break;

          case PurchaseStatus.error:
            // handle if error here
            log('Purchase has an error');
            break;
          default:
        }

        if (purchase.pendingCompletePurchase) {
          await _inAppPurchase.completePurchase(purchase);
        }
      }
    });

    await _inAppPurchase.restorePurchases();
  }

  void _handleSuccessfullySubscribed() async {
    await _settingsDAO.customUpdate(
      r"UPDATE settings SET details = json_set(details, '$.membership', ?) WHERE id = 1;",
      variables: [
        Variable<String>(Membership.paid.name),
      ],
      updates: {
        _settingsDAO.settingsTable,
      },
    );

    final settings = await _settingsDAO.get();

    log('Settings data log ${settings.data}');
  }

  void _handleFailedSubscribed() async {
    await _settingsDAO.customUpdate(
      r"UPDATE settings SET details = json_set(details, '$.membership', ?) WHERE id = 1;",
      variables: [
        Variable<String>(Membership.free.name),
      ],
      updates: {
        _settingsDAO.settingsTable,
      },
    );

    final settings = await _settingsDAO.get();

    log('Settings data log ${settings.data}');
  }

  @override
  Future<Either<Failure, List<ProductDetails>>> getProducts() async {
    try {
      final bool isAvailable = await _inAppPurchase.isAvailable();

      if (!isAvailable) {
        return left(const Failure(code: FailureCode.unexpected));
      }

      final Set<String> productsIds = {
        'expample',
      };

      final ProductDetailsResponse response =
          await _inAppPurchase.queryProductDetails(productsIds);

      final List<ProductDetails> products = response.productDetails;

      return right(products);
    } catch (e) {
      return left(const Failure(code: FailureCode.unexpected));
    }
  }

  @override
  Future<Either<Failure, Unit>> subscribe(ProductDetails details) async {
    try {
      await _inAppPurchase.buyNonConsumable(
          purchaseParam: PurchaseParam(productDetails: details));

      return right(unit);
    } catch (e) {
      return left(const Failure(code: FailureCode.unexpected));
    }
  }

  @override
  Future<Either<Failure, Unit>> verifySubscription(
      {required String token, required String productId}) async {
    try {
      final settings = locator<ISettingsRepository>();

      final InternetConnectionChecker connectionChecker =
          InternetConnectionChecker();
      final either = await settings.get();

      either.fold((f) {
        // return left(const Failure(code: FailureCode.unexpected));
      }, (settings) async {
        if (settings.membership == Membership.paid &&
            (await connectionChecker.connectionStatus) ==
                InternetConnectionStatus.connected) {
          await locator<Dio>().post('google-subscriptions/v1/validate', data: {
            "productId": productId,
            "purchaseToken": token,
            "packageName": "app.example"
          });
        }
      });

      return right(unit);
    } on DioException catch (_) {
      _handleFailedSubscribed();
      return left(const Failure(code: FailureCode.unexpected));
    }
  }
}