# Flutter iOS Integration
source: https://developer.mastercard.com/mastercard-gateway/documentation/integrations-types/mobile-integration/integrate-mobile-payments/mc-gw-ios-sdk/flutter-ios-integration/index.md

## Compatibility {#compatibility}

The Gateway SDK requires a minimum of iOS 11+ and is compatible with Swift 5 projects.

## Installation {#installation}

Follow these steps to add the Gateway SDK into your Xcode Project:

1. From your Merchant Admin portal, download the latest version of the SDK as a zip file.  

   For more information about downloading the SDK, see [Mobile SDK Integration](https://developer.mastercard.com/mastercard-gateway/documentation/integrations-types/mobile-integration/integrate-mobile-payments/mob-sdk-int/index.md).

2. Drag the `Gateway-SDK.xcframework` folder in your Xcode project.

3. Add the library to your targets "Frameworks, Libraries, and Embedded Content".

4. Do import Gateway of the framework where needed.

```swift
// AppDelegate.swift
import Gateway
```

5. You can also set the `Gateway-SDK.xcframework` as a local swift package with the `.binaryTarget` option.
6. SDK depends on the `uSDK.xcframework` bundled in the zip file format. Ensure to include this in your project.

## Initialize the SDK {#initialize-the-sdk}

The iOS SDK must be initialized before using it. It is recommended to perform this operation in your AppDelegate class.
Warning: Contact your payment service provider to know your gateway region.

To initialize the SDK in a Flutter application, implement the platform-specific code that handles method calls from Flutter. Follow these steps to initialize the SDK:

1. Add the following code to handle SDK initialization in platform-specific code:
2. Ensure that your `MethodChannel` is set up correctly to call the `initialiseGatewaySDK` method. This is typically done in the `Appdelegate` or another appropriate place in your iOS swift code.

```swift
func initialiseSDK(call: FlutterMethodCall, result: FlutterResult) {
    // Extract and cast arguments
    guard let merchantDetails = call.arguments as? [String: Any],
          let merchantId = merchantDetails["merchantId"] as? String,
          let merchantName = merchantDetails["merchantName"] as? String,
          let merchantUrl = merchantDetails["merchantUrl"] as? String,
          let region = merchantDetails["region"] as? String else {
        return
    }

    // Initialize the GatewaySDK
    GatewaySDK.shared.initialize(
        merchantId: merchantId,
        merchantName: merchantName,
        merchantUrl: merchantUrl,
        region: region
    )

    result("Success")
}
```

3. To initialize the SDK from dart, refer to the following code.

```dart
// Define the MethodChannel
static const MethodChannel _channel = MethodChannel('com.yourcompany.gateway_sdk');

// Prepare arguments for the method call
final Map<String, dynamic> arguments = {
  'merchantId': merchantId,       // Your merchant ID
  'merchantName': merchantName,   // Your merchant name
  'merchantUrl': merchantUrl,     // Your merchant URL
  'region': region,               // Your region
};

// Invoke the method and handle the result
_channel.invokeMethod('initialiseGatewaySDK', arguments).then((result) {
  // Handle success result here
}).catchError((error) {
  // Handle error result here
});
```

### Session overview {#session-overview}

The Gateway SDK flow is based around the concept of a session. A session is a temporary container for any request fields and values of operations that reference a session. For more information, see the [Payment Session](https://developer.mastercard.com/mastercard-gateway/documentation/integrations-types/hosted-session/integrate-hosted-session/create-payment-session/index.md) documentation.

#### Key benefits {#key-benefits}

The key benefits are as follows:

* Reduces PCI compliance costs as you do not handle or store any payment details.
* Eases integration as you do not need to directly handle the values for the request fields stored in a session.
* Reduces internal fraud as your staff have limited access to payer's details.
* Allows you to update the request fields and values stored against a session. This is useful when a credit card expires or other details of a payer change.
* Allows you to retrieve the request fields and values contained in a session by specifying the session identifier.

### Create a session {#create-a-session}

Create a session with the gateway to initiate the payment flow on a mobile device.

To prepare the session for mobile transactions:

* Two API calls must be made.
* Ensure that these requests are made from your private server since they are protected by an API password.

|  Request Parameter  | Example |
|---------------------|---------|
| authenticationLimit | 25      |

### Update the session {#update-the-session}

This table describes the request parameters for update the session.

|       Request Parameter       | Existence |       Example       |
|-------------------------------|-----------|---------------------|
| order.id                      | Required  | your-order-id       |
| order.amount                  | Required  | 1.23                |
| order.currency                | Required  | AUD                 |
| authentication.acceptVersions | Required  | 3DS2                |
| authentication.channel        | Required  | PAYER_APP           |
| authentication.purpose        | Required  | PAYMENT_TRANSACTION |

Warning: To authenticate the payer, load the specified API fields into the session before calling within the SDK. The API design determines how and when they are loaded into the session.

Once a session is created on your server, you should:

1. Return the session information back to the mobile application.
2. Pass this information to the SDK with the collect card information.

Warning: The apiVersion should remain the same for the whole transaction lifecycle, from session creation to final payment.

## Collecting card information {#collecting-card-information}

The SDK method to updateSession is optional to use but is recommended to help with merchant server PCI scope. However, the card and token information can be loaded through a different API design and must be present in the session before the call is made in the SDK to authenticate the payer.

### Manual card entry {#manual-card-entry}

Follow these steps to make a manual card entry.

1. Pass the information directly to the gateway using an existing session ID.
2. To update card information, implement the platform-specific code to handle method call from Flutter.

```swift
func updateSession(call: FlutterMethodCall, result: @escaping FlutterResult) {
    guard let sessionDetails = call.arguments as? [String: Any],
          let name = sessionDetails["nameOnCard"] as? String,
          let number = sessionDetails["number"] as? String,
          let expiryMonth = sessionDetails["month"] as? String,
          let expiryYear = sessionDetails["year"] as? String,
          let sessionId = sessionDetails["sessionId"] as? String,
          let currency = sessionDetails["currency"] as? String,
          let amount = sessionDetails["amount"] as? String,
          let orderId = sessionDetails["orderId"] as? String,
          let cvv = sessionDetails["securityCode"] as? String,
          let apiVersion = sessionDetails["apiVersion"] as? String else {
        return
    }

    // The GatewayMap object provides support for building a nested map structure using key-based dot(.) notation.
    // Each parameter is similarly defined in your online integration guide.
    var request = GatewayMap()
    request.sourceOfFunds.provided.card.nameOnCard.value = name
    request.sourceOfFunds.provided.card.number.value = number
    request.sourceOfFunds.provided.card.securityCode.value = cvv
    request.sourceOfFunds.provided.card.expiry.month.value = expiryMonth
    request.sourceOfFunds.provided.card.expiry.year.value = expiryYear

    GatewayAPI.shared.updateSession(sessionId, apiVersion: apiVersion, payload: request) { response in
        // Handle the response and invoke the callback function to update the Dart code.
    }
}
```

3. You can call the preceding method similar to the following method:

```dart
// Assuming `gatewayChannel` is an object that has `invokeMethod` function
// and `updateSessionMethod` is a string representing the method name

gatewayChannel.invokeMethod(updateSessionMethod, {
  'nameOnCard': cardHolderName,     // Cardholder's name
  'number': cardNumber,             // Card number
  'securityCode': cvvCode,          // CVV code
  'month': expiryMonth,             // Expiry month
  'year': expiryYear,               // Expiry year
  'sessionId': sessionId,           // Session ID
  'amount': '1.97',                 // Amount to be processed
  'currency': 'USD',                // Currency code
  'orderId': 'your-order-id',       // Order ID
  'apiVersion': 61,                 // API version
});
```

### Tokenization {#tokenization}

The SDK provides support to update a session with card information, you can use that session to perform several operations with the gateway. Tokenization provides a way to retain a card on file and can be performed on your server with a valid session.

#### Create a card token {#create-a-card-token}

Follow these steps to use the mobile SDK to help creating a card token.

1. Create and Update a session using the SDK.
2. Update the session with the customer's card details through the Gateway SDK.GatewayAPIupdateSession method.
3. Return the Session ID to your server and call the Create or Update Token method on the gateway with your private API credentials.
4. A token ID is returned and can be retained on your servers as a card-on-file.

For more information about Tokenization, see the [Create or Update Token](https://developer.mastercard.com/mastercard-gateway/documentation/api-reference/v100/rest/api-ops/index.md#tokenization) documentation.

### Apple Pay {#apple-pay}

The Gateway SDK includes a helper utility for collecting information from an Apple Pay Wallet.

Warning: You can integrate Apple Pay using the native iOS SDK. For more information, refer to [Apple Pay](https://developer.mastercard.com/mastercard-gateway/documentation/integrations-types/mobile-integration/integrate-mobile-payments/mc-gw-ios-sdk/index.md#apple-pay).

<br />

### Payer authentication {#payer-authentication}

#### EMV 3-D Secure {#emv-3-d-secure}

EMV 3-D Secure or EMV 3-D Secure authentication is designed to protect online purchases against credit card fraud by allowing you to authenticate the payer before submitting an Authorization or Pay transaction.

The EMV 3-D Secure, also known as 3DS2 in the gateway, is the new version designed to enhance security in online purchases while providing frictionless checkouts to payers who are considered low risk by the Access Control Server (ACS).

The ACS may determine the risk using merchant information, device fingerprinting, previous interactions with the payer, or both. The ACS subjects the payer to a challenge, for example, entering a PIN, only where additional verification is required to authenticate the payer, thereby providing increased conversion rates.

Supported authentication schemes include Mastercard Identity Check, Visa Secure, and American Express SafeKey.

Authentication within the mobile SDKs is limited to 3DS2 only. If 3DS2 is not available, the authentication does not proceed. However, you can still proceed with the payment if the gateway recommends you do so.

For more information about EMV 3-D Secure Authentication, see the [EMV 3-D Secure Authentication](https://developer.mastercard.com/mastercard-gateway/documentation/security-and-fraud/authentication/3d-secure-auth/index.md) documentation.

### Authentication details {#authentication-details}

The embedded mobile SDK collects device metrics to send to the gateway along with your transaction information when you perform mobile SDK authentication, that is, verify the identity of a cardholder in a mobile application.

Provide as much information as possible about the payer and the transaction to increase the likelihood of the authentication being successful.

This additional information can be added to your session with an Update session request.

|             Parameter              | Existence |                              Description                              |
|------------------------------------|-----------|-----------------------------------------------------------------------|
| `order.merchantCategoryCode`       | Optional  | Same as the code in your merchant profile.                            |
| `billing.address` parameter group  | Optional  | It is recommended you include this in your request whenever possible. |
| `shipping.address` parameter group | Optional  | It is recommended you include this in your request whenever possible. |
| customer parameter group           | Optional  | It is recommended you include this in your request whenever possible. |

The device parameter group as seen in the documentation is only relevant for browser-based payments. It should not be used for mobile based payer authentications. These metrics help the system to determine how or if to authenticate the cardholder. During authentication, the user can expect to experience one of two authentication flows:

1. Frictionless: The Access Control Server (ACS) has collected enough information about the cardholder to authenticate them. No other action is needed by the user.
2. Challenge: The ACS requires the cardholder to complete an additional authentication step, which is to enter a onetime-password, login to their issuing bank, and so on. The embedded mobile SDK handles displaying a native device interface for this challenge. The UI for these screens can be customized by passing `UICustomization` params into the Gateway SDK during initialization.

For more information, see [Authenticate Payer](https://developer.mastercard.com/mastercard-gateway/documentation/api-reference/v100/rest/api-ops/index.md#authentication) documentation.
Warning: The parameter group for `authentication.PSD2.exemption` is currently not supported in the SDK.

### Perform authentication {#perform-authentication}

Payer authentication is considered a transaction on its own in the gateway, and therefore needs a unique transaction ID.

If you are collecting payment for an order, you can:

* Correlate a payment and an authentication transaction by using the same order ID for each transaction.
* Each transaction is displayed as a separate transaction in the gateway's web portal, such as UUID.

```kotlin
AuthenticationHandler.authenticate(
    activityContext,
    session,
    "your-auth-transaction-id",
    callback
)
```

Warning: The `your-auth-transaction-id` is a unique identifier for this transaction which distinguishes it from any other transaction on the order. This is needed as the gateway uses the `your-auth-transaction-id` to look up the authentication results that it stored when you asked the SDK to authenticate the payer. The gateway then passes the required information to the acquirer for the pay request.

### Interpret the response {#interpret-the-response}

The authenticate method returns an `AuthenticationResponse` object that contains:

* Important information about the outcome.
* Actions performed during the operation.

The most important field to consume is response.recommendation. It may contain the value PROCEED or DO_NOT_PROCEED.

* PROCEED: Indicates "OK to continue with a payment or authorization".
* DO_NOT_PROCEED: Indicates something failed during the authentication operation. The `AuthenticationError` object can be used to determine more.

From Mastercard Gateway API version 70 and later, you can get the following errors:

* `AuthenticationError.recommendation_ResubmitWithAlternativePaymentDetails`: Indicates that you should ask the payer for alternative payment details. For example, a new card or another payment method, and resubmit the request with the new details.
* `AuthenticationError.recommendation_AbandonOrder`: Indicates the payment service provider, scheme, or issuer require you to abandon the order.
* `AuthenticationError.recommendation_DoNotProceed`: Indicates that the gateway fails the request, but there is no way for this transaction to succeed.

For more information, see the Integration guides.

Follow these steps to perform authentication:

1. To perform authentication, implement platform-specific code to handle method calls from Flutter.

```swift
func performAuthentication(call: FlutterMethodCall, result: @escaping FlutterResult) {
    // Retrieve sessionID, orderId, apiVersion, and transactionID from call.arguments passed from Dart code.
    // Refer to updateSession function for extraction logic.

    let authenticationId = UUID().uuidString

    let request = AuthenticationRequest(
        navController: navController,
        apiVersion: apiVersion,
        sessionId: sessionId,
        orderId: orderId,
        transactionId: authenticationId
    )

    AuthenticationHandler.shared.authenticate(request) { response in
        switch response.recommendation {
        case .doNotProceed, .proceed:
            // Handle the success response and invoke the callback function to update the Dart code.
            break

        @unknown default:
            // Handle the error response and invoke the callback function to update the Dart code.
            break
        }
    }
}
```

2. If the authentication fails, you can examine the response.error for more information about the cause.

```dart
// Assuming `gatewayChannel` is an object that has `invokeMethod` function
// and `authenticateMethod` is a string representing the method name

gatewayChannel.invokeMethod(authenticateMethod, {
  "session": 'session-object',
  "authenticationId": authenticationId,
}).then((result) {
  // Extract the recommendation from the result
  final recommendation = result['recommendation'];

  // Check the recommendation and handle accordingly
  if (recommendation == 'PROCEED') {
    // Continue to payment/authorization
    handlePaymentAuthorization();
  } else if (recommendation == 'DO_NOT_PROCEED') {
    // Handle authentication not successful, re-enter card details
  }
});
```