### Installation Configuration

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Configures installation rules for the application and its components. It sets the installation prefix to be adjacent to the executable for in-place running and defines destinations for data and libraries.

```cmake
set(BUILD_BUNDLE_DIR "$<TARGET_FILE_DIR:${BINARY_NAME}>")
set(CMAKE_VS_INCLUDE_INSTALL_TO_DEFAULT_BUILD 1)
if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
  set(CMAKE_INSTALL_PREFIX "${BUILD_BUNDLE_DIR}" CACHE PATH "..." FORCE)
endif()

set(INSTALL_BUNDLE_DATA_DIR "${CMAKE_INSTALL_PREFIX}/data")
set(INSTALL_BUNDLE_LIB_DIR "${CMAKE_INSTALL_PREFIX}")
```

--------------------------------

### Install Application Target

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Installs the main application executable to the runtime destination.

```cmake
install(TARGETS ${BINARY_NAME} RUNTIME DESTINATION "${CMAKE_INSTALL_PREFIX}"
  COMPONENT Runtime)
```

--------------------------------

### Install Flutterwave Flutter SDK

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/README.md

Add the flutterwave_standard package to your pubspec.yaml file and run flutter pub get to install it.

```yaml
dependencies:
  flutterwave_standard: 1.1.0
```

--------------------------------

### Installation Rules for Flutter Linux App Bundle

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/linux/CMakeLists.txt

Defines how the application bundle is installed, including cleaning the build directory, installing the executable, data files, libraries, and assets.

```cmake
# === Installation ===
# By default, "installing" just makes a relocatable bundle in the build
# directory.
set(BUILD_BUNDLE_DIR "${PROJECT_BINARY_DIR}/bundle")
if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
  set(CMAKE_INSTALL_PREFIX "${BUILD_BUNDLE_DIR}" CACHE PATH "..." FORCE)
endif()

# Start with a clean build bundle directory every time.
install(CODE "
  file(REMOVE_RECURSE \"${BUILD_BUNDLE_DIR}/\")
  " COMPONENT Runtime)

set(INSTALL_BUNDLE_DATA_DIR "${CMAKE_INSTALL_PREFIX}/data")
set(INSTALL_BUNDLE_LIB_DIR "${CMAKE_INSTALL_PREFIX}/lib")

install(TARGETS ${BINARY_NAME} RUNTIME DESTINATION "${CMAKE_INSTALL_PREFIX}"
  COMPONENT Runtime)

install(FILES "${FLUTTER_ICU_DATA_FILE}" DESTINATION "${INSTALL_BUNDLE_DATA_DIR}"
  COMPONENT Runtime)

install(FILES "${FLUTTER_LIBRARY}" DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
  COMPONENT Runtime)

foreach(bundled_library ${PLUGIN_BUNDLED_LIBRARIES})
  install(FILES "${bundled_library}"
    DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
    COMPONENT Runtime)
endforeach(bundled_library)

# Copy the native assets provided by the build.dart from all packages.
set(NATIVE_ASSETS_DIR "${PROJECT_BUILD_DIR}native_assets/linux/")
install(DIRECTORY "${NATIVE_ASSETS_DIR}"
   DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
   COMPONENT Runtime)

# Fully re-copy the assets directory on each build to avoid having stale files
# from a previous install.
set(FLUTTER_ASSET_DIR_NAME "flutter_assets")
install(CODE "
  file(REMOVE_RECURSE \"${INSTALL_BUNDLE_DATA_DIR}/${FLUTTER_ASSET_DIR_NAME}\")
  " COMPONENT Runtime)
install(DIRECTORY "${PROJECT_BUILD_DIR}/${FLUTTER_ASSET_DIR_NAME}"
  DESTINATION "${INSTALL_BUNDLE_DATA_DIR}" COMPONENT Runtime)

# Install the AOT library on non-Debug builds only.
if(NOT CMAKE_BUILD_TYPE MATCHES "Debug")
  install(FILES "${AOT_LIBRARY}" DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
    COMPONENT Runtime)
endif()
```

--------------------------------

### Usage Examples

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/subaccount.md

Demonstrates how to use the SubAccount class for various split payment scenarios.

```APIDOC
## Usage Example

### Split Payment with Two Sub-Accounts

```dart
import 'package:flutterwave_standard/flutterwave.dart';

// Create sub-accounts for 50-50 split
final List<SubAccount> subAccounts = [
  SubAccount(
    id: "AC_xxxxxxxxxx",
    transactionSplitRatio: 50,
    transactionChargeType: "percentage",
    transactionPercentage: 50.0
  ),
  SubAccount(
    id: "AC_yyyyyyyyyy",
    transactionSplitRatio: 50,
    transactionChargeType: "percentage",
    transactionPercentage: 50.0
  )
];

final Flutterwave flutterwave = Flutterwave(
  publicKey: "YOUR_PUBLIC_KEY",
  txRef: "txn_${DateTime.now().millisecondsSinceEpoch}",
  amount: "10000",
  customer: Customer(email: "customer@example.com"),
  paymentOptions: "card, ussd",
  customization: Customization(title: "Split Payment"),
  redirectUrl: "https://example.com/callback",
  isTestMode: true,
  currency: "NGN",
  subAccounts: subAccounts
);

final ChargeResponse response = await flutterwave.charge(context);
```

### Variable Split with Multiple Sub-Accounts

```dart
final List<SubAccount> subAccounts = [
  SubAccount(
    id: "AC_1234567",
    transactionSplitRatio: 60,
    transactionChargeType: "percentage",
    transactionPercentage: 60.0
  ),
  SubAccount(
    id: "AC_7654321",
    transactionSplitRatio: 40,
    transactionChargeType: "percentage",
    transactionPercentage: 40.0
  )
];

final Flutterwave flutterwave = Flutterwave(
  publicKey: "YOUR_PUBLIC_KEY",
  txRef: "txn_split_60_40",
  amount: "50000",
  customer: Customer(email: "merchant@example.com"),
  paymentOptions: "card",
  customization: Customization(title: "Vendor Payment"),
  redirectUrl: "https://example.com",
  isTestMode: true,
  currency: "NGN",
  subAccounts: subAccounts
);

final response = await flutterwave.charge(context);
```

### Flat Amount Split

```dart
final List<SubAccount> subAccounts = [
  SubAccount(
    id: "AC_partner_main",
    transactionChargeType: "flat",
    transactionPercentage: 5000.0  // Fixed 5000
  ),
  SubAccount(
    id: "AC_partner_secondary",
    transactionChargeType: "flat",
    transactionPercentage: 2000.0  // Fixed 2000
  )
];

final Flutterwave flutterwave = Flutterwave(
  publicKey: "YOUR_PUBLIC_KEY",
  txRef: "txn_flat_split",
  amount: "25000",
  customer: Customer(email: "customer@example.com"),
  paymentOptions: "card, ussd, bank transfer",
  customization: Customization(title: "Commission Split"),
  redirectUrl: "https://example.com",
  isTestMode: true,
  currency: "NGN",
  subAccounts: subAccounts
);

final response = await flutterwave.charge(context);
```

## Charge Type Reference

| Type | Description | Example Values |
|---|---|---|
| percentage | Allocate as a percentage of transaction amount | 50.0 (50%), 25.0 (25%) |
| flat | Allocate as a fixed amount | 5000.0 (5000 in transaction currency) |
```

--------------------------------

### Customer Usage Examples

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/customer.md

Demonstrates creating Customer objects with different fields and how their JSON representation looks.

```dart
import 'package:flutterwave_standard/flutterwave.dart';

// Basic customer with required fields only
final Customer customer1 = Customer(
  email: "john@example.com"
);
//toJson() returns: {"email": "john@example.com"}

// Full customer with all fields
final Customer customer2 = Customer(
  email: "jane@example.com",
  name: "Jane Smith",
  phoneNumber: "+234812345678"
);
// toJson() returns: {
//   "email": "jane@example.com",
//   "phonenumber": "+234812345678",
//   "name": "Jane Smith"
// }

// Empty fields are excluded from JSON
final Customer customer3 = Customer(
  email: "bob@example.com",
  name: "Bob Jones",
  phoneNumber: null
);
// toJson() returns: {
//   "email": "bob@example.com",
//   "name": "Bob Jones"
// }
```

--------------------------------

### SubAccount Configuration Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/configuration.md

Configure sub-accounts with ID, split ratio, and charge type. Get sub-account IDs from the Flutterwave Dashboard.

```dart
final List<SubAccount> subAccounts = [
  SubAccount(
    id: "AC_xxxxx",
    transactionSplitRatio: 70,
    transactionChargeType: "percentage",
    transactionPercentage: 70.0
  ),
  SubAccount(
    id: "AC_yyyyy",
    transactionSplitRatio: 30,
    transactionChargeType: "percentage",
    transactionPercentage: 30.0
  )
];
```

--------------------------------

### Redirect URL Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/endpoints.md

This is an example of a redirect URL with transaction status query parameters.

```url
https://example.com/callback?status=successful&tx_ref=txn_123&transaction_id=FLW-123456
```

--------------------------------

### Install Bundled Plugin Libraries

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Installs any bundled libraries provided by plugins to the library directory as part of the runtime component, if they exist.

```cmake
if(PLUGIN_BUNDLED_LIBRARIES)
  install(FILES "${PLUGIN_BUNDLED_LIBRARIES}"
    DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
    COMPONENT Runtime)
endif()
```

--------------------------------

### Install AOT Library

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Installs the Ahead-Of-Time (AOT) compiled library, but only for Profile and Release build configurations.

```cmake
install(FILES "${AOT_LIBRARY}" DESTINATION "${INSTALL_BUNDLE_DATA_DIR}"
  CONFIGURATIONS Profile;Release
  COMPONENT Runtime)
```

--------------------------------

### Manage API Keys with a Configuration Class

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/configuration.md

This example shows how to manage test and production API keys using a static configuration class. This approach helps in centralizing key management and conditionally selecting the appropriate key based on the environment.

```dart
// In your config file or secrets manager
class FlutterwaveConfig {
  static const String TEST_PUBLIC_KEY = "FLWPUBK_TEST-xxx";
  static const String PROD_PUBLIC_KEY = "FLWPUBK_LIVE-xxx";
  
  static String getPublicKey(bool isTestMode) {
    return isTestMode ? TEST_PUBLIC_KEY : PROD_PUBLIC_KEY;
  }
}

// Usage
final Flutterwave flutterwave = Flutterwave(
  publicKey: FlutterwaveConfig.getPublicKey(isTestMode),
  // ... other parameters ...
);
```

--------------------------------

### Full Customization Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/customization.md

Creates a Customization instance with title, description, and logo. The toJson() method returns a JSON object with all provided fields.

```dart
final Customization customization2 = Customization(
  title: "Order Payment",
  description: "Pay for your premium subscription",
  logo: "https://example.com/images/logo.png"
);
// toJson() returns: {
//   "title": "Order Payment",
//   "description": "Pay for your premium subscription",
//   "logo": "https://example.com/images/logo.png"
// }
```

--------------------------------

### Install Native Assets

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Installs native assets provided by the build.dart script from all packages to the library directory as part of the runtime component.

```cmake
set(NATIVE_ASSETS_DIR "${PROJECT_BUILD_DIR}native_assets/windows/")
install(DIRECTORY "${NATIVE_ASSETS_DIR}"
   DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
   COMPONENT Runtime)
```

--------------------------------

### Implement Simple Payment Flow

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/INTEGRATION-GUIDE.md

This example demonstrates a basic payment flow using the Flutterwave SDK. It includes handling loading states, processing payments, and displaying success, cancellation, or error messages to the user.

```dart
import 'package:flutter/material.dart';
import 'package:flutterwave_standard/flutterwave.dart';
import 'package:uuid/uuid.dart';

class PaymentButton extends StatefulWidget {
  final String amount;
  final String email;
  
  const PaymentButton({
    required this.amount,
    required this.email,
  });

  @override
  State<PaymentButton> createState() => _PaymentButtonState();
}

class _PaymentButtonState extends State<PaymentButton> {
  bool _isLoading = false;

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: _isLoading ? null : _processPayment,
      child: _isLoading
          ? SizedBox(
              width: 20,
              height: 20,
              child: CircularProgressIndicator(
                strokeWidth: 2,
                valueColor: AlwaysStoppedAnimation<Color>(
                  Theme.of(context).colorScheme.onPrimary,
                ),
              ),
            )
          : const Text('Pay Now'),
    );
  }

  Future<void> _processPayment() async {
    if (!mounted) return;

    setState(() => _isLoading = true);

    try {
      final Customer customer = Customer(
        email: widget.email,
      );

      final Flutterwave flutterwave = Flutterwave(
        publicKey: "YOUR_PUBLIC_KEY",
        txRef: const Uuid().v4(),
        amount: widget.amount,
        customer: customer,
        paymentOptions: "card, ussd, bank transfer",
        customization: Customization(title: "Payment"),
        redirectUrl: "https://example.com/payment-callback",
        isTestMode: true,
        currency: "NGN",
      );

      final ChargeResponse? response = await flutterwave.charge(context);

      if (!mounted) return;

      if (response?.success == true) {
        _showSuccess(response!.transactionId);
      } else if (response?.status == "cancelled") {
        _showCancelled();
      } else {
        _showError(response?.status ?? "Unknown error");
      }
    } catch (e) {
      if (mounted) {
        _showError(e.toString());
      }
    } finally {
      if (mounted) {
        setState(() => _isLoading = false);
      }
    }
  }

  void _showSuccess(String? txnId) {
    showDialog(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('✓ Payment Successful'),
        content: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            const Text('Your payment has been processed.'),
            if (txnId != null) ...[
              const SizedBox(height: 16),
              Text('Transaction ID: $txnId'),
            ],
          ],
        ),
        actions: [ 
          TextButton(
            onPressed: () => Navigator.pop(context),
            child: const Text('OK'),
          ),
        ],
      ),
    );
  }

  void _showCancelled() {
    showDialog(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('Payment Cancelled'),
        content: const Text('You cancelled the payment.'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context),
            child: const Text('OK'),
          ),
        ],
      ),
    );
  }

  void _showError(String message) {
    showDialog(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('✗ Payment Failed'),
        content: Text(message),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context),
            child: const Text('OK'),
          ),
        ],
      ),
    );
  }
}
```

--------------------------------

### Empty Customization Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/customization.md

Initializes a Customization instance without any parameters. The toJson() method will return an empty JSON object.

```dart
final Customization customization3 = Customization();
// toJson() returns: {}
```

--------------------------------

### Project and CMake Version Setup

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Sets the minimum required CMake version and defines the project name and languages. It also explicitly opts into modern CMake behaviors.

```cmake
cmake_minimum_required(VERSION 3.14)
project(example LANGUAGES CXX)
```

```cmake
cmake_policy(VERSION 3.14...3.25)
```

--------------------------------

### Install Flutter Assets

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Installs the Flutter assets directory. It ensures the directory is completely re-copied on each build to prevent stale files and places it in the data directory.

```cmake
set(FLUTTER_ASSET_DIR_NAME "flutter_assets")
install(CODE "
  file(REMOVE_RECURSE \"${INSTALL_BUNDLE_DATA_DIR}/${FLUTTER_ASSET_DIR_NAME}\")
  " COMPONENT Runtime)
install(DIRECTORY "${PROJECT_BUILD_DIR}/${FLUTTER_ASSET_DIR_NAME}"
  DESTINATION "${INSTALL_BUNDLE_DATA_DIR}" COMPONENT Runtime)
```

--------------------------------

### Split Payment with Two Sub-Accounts

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/subaccount.md

Example demonstrating a 50-50 split payment configuration using two sub-accounts with percentage-based allocation.

```dart
import 'package:flutterwave_standard/flutterwave.dart';

// Create sub-accounts for 50-50 split
final List<SubAccount> subAccounts = [
  SubAccount(
    id: "AC_xxxxxxxxxx",
    transactionSplitRatio: 50,
    transactionChargeType: "percentage",
    transactionPercentage: 50.0
  ),
  SubAccount(
    id: "AC_yyyyyyyyyy",
    transactionSplitRatio: 50,
    transactionChargeType: "percentage",
    transactionPercentage: 50.0
  )
];

final Flutterwave flutterwave = Flutterwave(
  publicKey: "YOUR_PUBLIC_KEY",
  txRef: "txn_${DateTime.now().millisecondsSinceEpoch}",
  amount: "10000",
  customer: Customer(email: "customer@example.com"),
  paymentOptions: "card, ussd",
  customization: Customization(title: "Split Payment"),
  redirectUrl: "https://example.com/callback",
  isTestMode: true,
  currency: "NGN",
  subAccounts: subAccounts
);

final ChargeResponse response = await flutterwave.charge(context);
```

--------------------------------

### Install ICU Data and Flutter Library

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/CMakeLists.txt

Installs the ICU data file and the main Flutter library to the data and library directories, respectively, as part of the runtime component.

```cmake
install(FILES "${FLUTTER_ICU_DATA_FILE}" DESTINATION "${INSTALL_BUNDLE_DATA_DIR}"
  COMPONENT Runtime)
```

```cmake
install(FILES "${FLUTTER_LIBRARY}" DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
  COMPONENT Runtime)
```

--------------------------------

### Basic Customization Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/customization.md

Creates a Customization instance with only a title. The toJson() method will return a JSON object containing just the title.

```dart
final Customization customization1 = Customization(
  title: "Complete Your Payment"
);
// toJson() returns: {"title": "Complete Your Payment"}
```

--------------------------------

### Webhook Payload Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/endpoints.md

An example of a webhook payload received from Flutterwave for event notifications like charge completion.

```json
{
  "event": "charge.completed",
  "data": {
    "id": 123456,
    "tx_ref": "txn_123456",
    "amount": 5000,
    "currency": "NGN",
    "status": "successful",
    "customer": {
      "id": 1,
      "email": "customer@example.com",
      "name": "John Doe",
      "phone_number": "+234812345678"
    }
  }
}
```

--------------------------------

### Verification API Response Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/endpoints.md

An example JSON response from the Flutterwave Verification API upon successful retrieval of transaction data.

```json
{
  "status": "success",
  "message": "Transaction retrieved",
  "data": {
    "id": 123456,
    "tx_ref": "txn_123456",
    "amount": 5000,
    "currency": "NGN",
    "status": "successful",
    "customer": {
      "email": "customer@example.com"
    }
  }
}
```

--------------------------------

### Payment Initialization Request Body with Split Payments

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/endpoints.md

Example of a request body for initializing payments with split sub-accounts. Define sub-account IDs, ratios, and charges.

```json
{
  "tx_ref": "txn_split_1234",
  "publicKey": "FLWPUBK_TEST-xxxx",
  "amount": "10000",
  "currency": "NGN",
  "payment_options": "card, ussd",
  "redirect_url": "https://example.com/callback",
  "customer": {
    "email": "merchant@example.com"
  },
  "subaccounts": [
    {
      "id": "AC_primary",
      "transaction_split_ratio": 70,
      "transaction_charge_type": "percentage",
      "transaction_charge": 70.0
    },
    {
      "id": "AC_secondary",
      "transaction_split_ratio": 30,
      "transaction_charge_type": "percentage",
      "transaction_charge": 30.0
    }
  ]
}
```

--------------------------------

### Charge Completed Webhook Payload Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/README.md

This is an example of the JSON payload received when a charge is completed. It includes transaction details and customer information.

```json
{
  "event": "charge.completed",
  "data": {
    "id": 123,
    "tx_ref": "txn_123",
    "status": "successful",
    "amount": 5000,
    "customer": {
      "email": "user@example.com"
    }
  }
}
```

--------------------------------

### Specify Payment Options

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/README.md

Define the payment methods to be offered to the user. This example shows how to enable card, USSD, bank transfer, and mobile money options.

```dart
paymentOptions: "card, ussd, bank transfer, mobile money"
```

--------------------------------

### Handle Deferred Payment Methods

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/transaction-status.md

This example shows how to handle payments from deferred methods like Bank Transfer or USSD Push. It includes a backend verification step to confirm payment status before completing an order.

```dart
void handlePaymentCompletion(ChargeResponse response) {
  if (response.success != true) {
    // Payment definitely failed
    showError("Payment failed: ${response.status}");
    return;
  }
  
  // For instant methods, success is final
  // For deferred methods, verify on backend
  verifyTransactionOnBackend(
    response.transactionId,
    response.txRef
  ).then((verified) {
    if (verified) {
      // Payment confirmed
      completeOrder();
    } else {
      // Payment still pending
      showWarning("Payment pending - we'll confirm shortly");
    }
  });
}
```

--------------------------------

### Transaction Verification Response Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/README.md

A sample JSON response structure for a successful transaction verification. It includes the status, amount, and currency of the transaction.

```json
{
  "status": "success",
  "data": {
    "status": "successful",
    "amount": 5000,
    "currency": "NGN"
  }
}
```

--------------------------------

### Commit Message Example

Source: https://github.com/flutterwave/flutter-v3/blob/master/CONTRIBUTING.md

Use a clear and descriptive message for your commits. For larger changes, provide a more detailed explanation beyond a one-liner.

```markdown
$ git commit -m "A brief summary of the commit
>
> A paragraph describing what changed and its impact."
```

--------------------------------

### Payment Initialization Error Response

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/endpoints.md

An example of an error response from the payment initialization endpoint. Includes status, message, and optional detailed errors.

```json
{
  "status": "error",
  "message": "Invalid API key",
  "errors": [
    {
      "message": "Unauthorized: invalid API key provided"
    }
  ]
}
```

--------------------------------

### Usage Example: Handling Transaction Errors during Payment

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/transaction-error.md

Demonstrates how to catch TransactionError during a payment process and display a user-friendly error message using a dialog.

```dart
import 'package:flutterwave_standard/flutterwave.dart';

void makePayment(BuildContext context) async {
  try {
    final Flutterwave flutterwave = Flutterwave(
      publicKey: "YOUR_PUBLIC_KEY",
      txRef: "txn_123",
      amount: "5000",
      customer: Customer(email: "user@example.com"),
      paymentOptions: "card",
      customization: Customization(title: "Payment"),
      redirectUrl: "https://example.com",
      isTestMode: true,
      currency: "NGN"
    );

    final ChargeResponse response = await flutterwave.charge(context);
  } catch (error) {
    if (error is TransactionError) {
      print('Transaction Error: ${error.message}');
      
      // Show user-friendly error message
      showDialog(
        context: context,
        builder: (context) => AlertDialog(
          title: Text('Payment Error'),
          content: Text(error.toString()),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context),
              child: Text('OK'),
            )
          ],
        ),
      );
    } else {
      print('Unexpected error: $error');
    }
  }
}
```

--------------------------------

### Customer Constructor

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/customer.md

Initializes a new Customer instance with email, name, and phone number. Email is required.

```APIDOC
## Customer Constructor

### Description
Initializes a new Customer instance. The email is a required field for transaction receipt and communication. The name and phoneNumber are optional.

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Method Signature
```dart
Customer({required String email, String? name, String? phoneNumber})
```

### Parameters
#### Parameters
- **email** (String) - Required - Customer's email address for transaction receipt and communication
- **name** (String) - Optional - Customer's full name
- **phoneNumber** (String) - Optional - Customer's phone number in international format (e.g., +234123456789)

### Returns
A new Customer instance.
```

--------------------------------

### Initiate Payment with Flutterwave SDK

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/flutterwave.md

Demonstrates a basic payment flow using the `charge` method. Ensure you have the necessary Flutterwave and Flutter dependencies. Replace placeholder keys and URLs with your actual values.

```dart
import 'package:flutter/material.dart';
import 'package:flutterwave_standard/flutterwave.dart';

void makePayment(BuildContext context) async {
  final Customer customer = Customer(
    email: "customer@example.com",
    name: "John Doe",
    phoneNumber: "+234123456789"
  );

  final Flutterwave flutterwave = Flutterwave(
    publicKey: "YOUR_PUBLIC_KEY",
    txRef: "txn_${DateTime.now().millisecondsSinceEpoch}",
    amount: "5000",
    customer: customer,
    paymentOptions: "card, ussd, bank transfer",
    customization: Customization(
      title: "Payment for Order",
      description: "Premium subscription",
      logo: "https://example.com/logo.png"
    ),
    redirectUrl: "https://example.com/payment-callback",
    isTestMode: true,
    currency: "NGN"
  );

  try {
    final ChargeResponse response = await flutterwave.charge(context);
    
    if (response.success == true) {
      print('Payment successful! Transaction ID: ${response.transactionId}');
      // Verify transaction with backend
    } else if (response.status == "cancelled") {
      print('User cancelled the payment');
    } else {
      print('Payment failed: ${response.status}');
    }
  } catch (e) {
    print('Error: $e');
  }
}
```

--------------------------------

### Flutterwave SDK File Organization

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/INDEX.md

Illustrates the directory structure for the Flutterwave SDK documentation.

```bash
/output/
├── README.md                          # Start here
├── INTEGRATION-GUIDE.md              # Implementation guide
├── INDEX.md                          # This file
├── configuration.md                  # Configuration reference
├── types.md                          # Type definitions
├── endpoints.md                      # HTTP endpoints
├── errors.md                         # Error reference
└── api-reference/                   # Individual class docs
    ├── flutterwave.md               # Main payment class
    ├── charge-response.md           # Response handling
    ├── customer.md                  # Customer model
    ├── customization.md             # UI customization
    ├── subaccount.md                # Split payments
    ├── transaction-error.md         # Error class
    ├── transaction-status.md        # Status constants
    └── utils.md                     # Utility functions
```

--------------------------------

### Initiating and Handling a Payment

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/charge-response.md

This snippet demonstrates how to initiate a payment using the Flutterwave SDK and handle the ChargeResponse. It includes logic for successful transactions, cancellations, and failures, along with a placeholder for backend verification.

```dart
import 'package:flutter/material.dart';
import 'package:flutterwave_standard/flutterwave.dart';

void examplePayment(BuildContext context) async {
  final Customer customer = Customer(
    email: "user@example.com"
  );

  final Flutterwave flutterwave = Flutterwave(
    publicKey: "YOUR_PUBLIC_KEY",
    txRef: "txn_${DateTime.now().millisecondsSinceEpoch}",
    amount: "5000",
    customer: customer,
    paymentOptions: "card, ussd",
    customization: Customization(title: "Payment"),
    redirectUrl: "https://example.com",
    isTestMode: true,
    currency: "NGN"
  );

  try {
    final ChargeResponse response = await flutterwave.charge(context);

    // Handle successful transaction
    if (response.success == true) {
      print('Transaction ID: ${response.transactionId}');
      print('Status: ${response.status}');
      print('Ref: ${response.txRef}');
      
      // Backend verification should be done here
      // Call your backend API with transactionId and txRef
      final verified = await verifyTransactionBackend(
        response.transactionId,
        response.txRef
      );
      
      if (verified) {
        showDialog(
          context: context,
          builder: (context) => AlertDialog(
            title: Text('Payment Successful'),
            content: Text('Transaction: ${response.transactionId}'),
          ),
        );
      }
    }
    // Handle cancellation
    else if (response.status == "cancelled") {
      print('Payment cancelled by user');
    }
    // Handle failure
    else {
      print('Payment failed with status: ${response.status}');
    }
  } catch (e) {
    print('Error: $e');
  }
}

// Example backend verification
Future<bool> verifyTransactionBackend(String? txnId, String? txRef) async {
  // Call your backend API to verify the transaction
  // using the transactionId and txRef
  return true;
}

```

--------------------------------

### Initiate Split Payments for Marketplace

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/INTEGRATION-GUIDE.md

This snippet demonstrates how to set up split payments for a marketplace, distributing funds between vendors and the platform. Ensure sub-account configurations are correct.

```dart
List<SubAccount> _createSplitAccounts({
  required double vendorAmount,
  required double platformAmount,
  required double totalAmount,
}) {
  final vendorPercentage = (vendorAmount / totalAmount) * 100;
  final platformPercentage = (platformAmount / totalAmount) * 100;

  return [
    SubAccount(
      id: "AC_vendor_main",
      transactionSplitRatio: vendorPercentage.toInt(),
      transactionChargeType: "percentage",
      transactionPercentage: vendorPercentage,
    ),
    SubAccount(
      id: "AC_platform_fee",
      transactionSplitRatio: platformPercentage.toInt(),
      transactionChargeType: "percentage",
      transactionPercentage: platformPercentage,
    ),
  ];
}

void _initiateMarketplacePayment(
  String vendorId,
  double amount,
) async {
  final subAccounts = _createSplitAccounts(
    vendorAmount: amount * 0.9,
    platformAmount: amount * 0.1,
    totalAmount: amount,
  );

  final Flutterwave flutterwave = Flutterwave(
    publicKey: config.publicKey,
    txRef: _generateUniqueTxRef(),
    amount: amount.toStringAsFixed(2),
    currency: "NGN",
    customer: Customer(
      email: currentUser.email,
      name: currentUser.fullName,
    ),
    paymentOptions: "card, ussd",
    customization: Customization(
      title: "Marketplace Purchase",
    ),
    redirectUrl: config.redirectUrl,
    isTestMode: isTestMode,
    subAccounts: subAccounts,
  );

  final response = await flutterwave.charge(context);
  // Handle response and record split in database...
}
```

--------------------------------

### Full Customization Configuration

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/configuration.md

Configure Customization with title, description, and logo.

```dart
final Customization customization = Customization(
  title: "Acme Corp Payment",
  description: "Premium Subscription Annual Plan",
  logo: "https://acme.com/logo.svg"
);
```

--------------------------------

### Find GTK, GLIB, and GIO modules

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/linux/flutter/CMakeLists.txt

Uses PkgConfig to find and check for the required GTK, GLIB, and GIO system-level dependencies.

```cmake
find_package(PkgConfig REQUIRED)
pkg_check_modules(GTK REQUIRED IMPORTED_TARGET gtk+-3.0)
pkg_check_modules(GLIB REQUIRED IMPORTED_TARGET glib-2.0)
pkg_check_modules(GIO REQUIRED IMPORTED_TARGET gio-2.0)
```

--------------------------------

### No Customization Configuration

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/configuration.md

Initialize Customization with no optional fields set.

```dart
final Customization customization = Customization();
```

--------------------------------

### Customization Constructor

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/customization.md

Initializes a new Customization instance with optional title, description, and logo parameters.

```dart
Customization({
  String? title,
  String? description,
  String? logo
})
```

--------------------------------

### Full Customer Configuration

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/configuration.md

Configure a customer with email, name, and phone number.

```dart
final Customer customer = Customer(
  email: "customer@example.com",
  name: "John Doe",
  phoneNumber: "+234812345678"
);
```

--------------------------------

### Customer Constructor

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/customer.md

Initializes a new Customer instance. Email is a required parameter.

```dart
Customer({
  required String email,
  String? name,
  String? phoneNumber
})
```

--------------------------------

### Verify Transaction API Request

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/README.md

This is an example of the API request format for verifying a transaction on the backend. It includes the HTTP method, endpoint, and authorization header.

```http
GET /v3/transactions/{transaction_id}/verify
Authorization: Bearer SECRET_KEY
```

--------------------------------

### Catching Transaction Errors in a try-catch block

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/transaction-error.md

Provides a best practice example for handling potential TransactionErrors during asynchronous operations, distinguishing them from other general exceptions.

```dart
try {
  final response = await flutterwave.charge(context);
  // Handle successful response
} on TransactionError catch (e) {
  // Handle transaction-specific errors
  print('Transaction failed: ${e.message}');
} catch (e) {
  // Handle other exceptions
  print('Unexpected error: $e');
}
```

--------------------------------

### Setting Up Flutter Library and Headers

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/flutter/CMakeLists.txt

This snippet configures the Flutter library path and includes essential header files for Flutter Windows development. It also sets up build directories and AOT library paths.

```cmake
cmake_minimum_required(VERSION 3.14)

set(EPHEMERAL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ephemeral")

# Configuration provided via flutter tool.
include(${EPHEMERAL_DIR}/generated_config.cmake)

# TODO: Move the rest of this into files in ephemeral. See
# https://github.com/flutter/flutter/issues/57146.
set(WRAPPER_ROOT "${EPHEMERAL_DIR}/cpp_client_wrapper")

# Set fallback configurations for older versions of the flutter tool.
if (NOT DEFINED FLUTTER_TARGET_PLATFORM)
  set(FLUTTER_TARGET_PLATFORM "windows-x64")
endif()

# === Flutter Library ===
set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/flutter_windows.dll")

# Published to parent scope for install step.
set(FLUTTER_LIBRARY ${FLUTTER_LIBRARY} PARENT_SCOPE)
set(FLUTTER_ICU_DATA_FILE "${EPHEMERAL_DIR}/icudtl.dat" PARENT_SCOPE)
set(PROJECT_BUILD_DIR "${PROJECT_DIR}/build/" PARENT_SCOPE)
set(AOT_LIBRARY "${PROJECT_DIR}/build/windows/app.so" PARENT_SCOPE)

list(APPEND FLUTTER_LIBRARY_HEADERS
  "flutter_export.h"
  "flutter_windows.h"
  "flutter_messenger.h"
  "flutter_plugin_registrar.h"
  "flutter_texture_registrar.h"
)
list(TRANSFORM FLUTTER_LIBRARY_HEADERS PREPEND "${EPHEMERAL_DIR}/")
add_library(flutter INTERFACE)
target_include_directories(flutter INTERFACE
  "${EPHEMERAL_DIR}"
)
target_link_libraries(flutter INTERFACE "${FLUTTER_LIBRARY}.lib")
add_dependencies(flutter flutter_assemble)
```

--------------------------------

### Basic Flutterwave Constructor Configuration

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/configuration.md

Initialize Flutterwave with required parameters for basic payment processing.

```dart
final Flutterwave flutterwave = Flutterwave(
  publicKey: "FLWPUBK_TEST-xxxxxxxxxxxxxxxxxxxx",
  txRef: "txn_${DateTime.now().millisecondsSinceEpoch}",
  amount: "5000",
  currency: "NGN",
  customer: Customer(email: "user@example.com"),
  paymentOptions: "card, ussd",
  customization: Customization(title: "Payment"),
  redirectUrl: "https://example.com/callback",
  isTestMode: true
);
```

--------------------------------

### Implement TransactionCallBack for Payment Handling

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/types.md

Example of implementing the TransactionCallBack interface to handle the result of a payment transaction. It checks for success, cancellation, or error based on the ChargeResponse object.

```dart
import 'package:flutterwave_standard/flutterwave.dart';

class PaymentHandler implements TransactionCallBack {
  @override
  onTransactionComplete(ChargeResponse? chargeResponse) {
    if (chargeResponse == null) {
      print('Payment was cancelled (response is null)');
      return;
    }
    
    if (chargeResponse.success == true) {
      print('Payment successful: ${chargeResponse.transactionId}');
      // Process successful payment
    } else {
      print('Payment failed: ${chargeResponse.status}');
      // Handle failure
    }
  }
}

// Usage in widget
class PaymentWidget extends StatefulWidget {
  @override
  State<PaymentWidget> createState() => _PaymentWidgetState();
}

class _PaymentWidgetState extends State<PaymentWidget> 
    implements TransactionCallBack {
  
  @override
  onTransactionComplete(ChargeResponse? chargeResponse) {
    // Handle transaction completion
    if (chargeResponse?.success == true) {
      Navigator.pop(context, chargeResponse);
    } else {
      // Show error
    }
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(),
    );
  }
}
```

--------------------------------

### Flutterwave Configuration Management

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/INTEGRATION-GUIDE.md

Manages Flutterwave API keys and redirect URLs for both test and production environments. Provides methods to get the appropriate values based on the environment.

```dart
class FlutterwaveConfig {
  static const _testPublicKey = 'FLWPUBK_TEST-xxxx';
  static const _prodPublicKey = 'FLWPUBK_LIVE-xxxx';
  
  static const _testRedirectUrl = 'https://sandbox.example.com/callback';
  static const _prodRedirectUrl = 'https://example.com/callback';
  
  static String getPublicKey(bool isProduction) {
    return isProduction ? _prodPublicKey : _testPublicKey;
  }
  
  static String getRedirectUrl(bool isProduction) {
    return isProduction ? _prodRedirectUrl : _testRedirectUrl;
  }
  
  static bool isTestMode(bool isProduction) {
    return !isProduction;
  }
}
```

--------------------------------

### Define Flutter library and headers

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/linux/flutter/CMakeLists.txt

Sets the path for the Flutter Linux GTK shared library and its associated header files. These are published to the parent scope for use in the install step.

```cmake
set(FLUTTER_LIBRARY "${EPHEMERAL_DIR}/libflutter_linux_gtk.so")

# Published to parent scope for install step.
set(FLUTTER_LIBRARY ${FLUTTER_LIBRARY} PARENT_SCOPE)
set(FLUTTER_ICU_DATA_FILE "${EPHEMERAL_DIR}/icudtl.dat" PARENT_SCOPE)
set(PROJECT_BUILD_DIR "${PROJECT_DIR}/build/" PARENT_SCOPE)
set(AOT_LIBRARY "${PROJECT_DIR}/build/lib/libapp.so" PARENT_SCOPE)
```

--------------------------------

### Initiate Payment with Full Customer Information

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/INTEGRATION-GUIDE.md

Use this snippet to initiate a standard payment when you have complete customer details. Ensure the Flutterwave SDK and necessary configurations are set up.

```dart
void _initiateFullPayment() async {
  final Customer customer = Customer(
    email: currentUser.email,
    name: currentUser.fullName,
    phoneNumber: currentUser.phoneNumber,
  );

  final Flutterwave flutterwave = Flutterwave(
    publicKey: flutterwaveConfig.publicKey,
    txRef: _generateUniqueTxRef(),
    amount: cartTotal.toStringAsFixed(2),
    customer: customer,
    paymentOptions: "card, ussd, bank transfer, mobile money",
    customization: Customization(
      title: "Complete Your Order",
      description: "Order #${orderId}",
      logo: "https://myapp.com/logo.png",
    ),
    redirectUrl: "https://myapp.com/order/success",
    isTestMode: !kReleaseMode,
    currency: "NGN",
    meta: {
      "userId": currentUser.id,
      "orderId": orderId,
      "cartItems": cartItems.length,
    },
  );

  final response = await flutterwave.charge(context);
  // Handle response...
}

String _generateUniqueTxRef() {
  final timestamp = DateTime.now().millisecondsSinceEpoch;
  final random = Random().nextInt(10000);
  return "ord_${orderId}_${timestamp}_${random}";
}
```

--------------------------------

### Verify Transaction Backend Implementation

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/endpoints.md

A Dart function for backend implementation to verify a transaction using the Flutterwave Verification API. It makes a GET request and checks the response status.

```dart
// On your backend
Future<bool> verifyTransaction(String transactionId) async {
  final response = await http.get(
    Uri.parse('https://api.flutterwave.com/v3/transactions/$transactionId/verify'),
    headers: {
      'Authorization': 'Bearer YOUR_SECRET_KEY'
    }
  );
  
  if (response.statusCode == 200) {
    final json = jsonDecode(response.body);
    return json['data']['status'] == 'successful';
  }
  return false;
}
```

--------------------------------

### Get Base URL

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/utils.md

Selects the appropriate API base URL based on the test mode flag. Use this to construct full API endpoints for sandbox or production environments.

```dart
static String getBaseUrl(final bool isTestMode)
```

```dart
import 'package:flutterwave_standard/utils.dart';

// Get sandbox URL
String testUrl = Utils.getBaseUrl(true);
// Result: "https://ravesandboxapi.flutterwave.com/v3/sdkcheckout/"

// Get production URL
String prodUrl = Utils.getBaseUrl(false);
// Result: "https://api.ravepay.co/v3/sdkcheckout/"

// Construct full endpoint
String endpoint = Utils.getBaseUrl(true) + Utils.STANDARD_PAYMENT;
// Result: "https://ravesandboxapi.flutterwave.com/v3/sdkcheckout/payments"
```

--------------------------------

### Perform Health Check

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/INTEGRATION-GUIDE.md

Performs a health check by making a GET request to the backend's health endpoint. Returns true if the API is reachable and returns a 200 status code.

```dart
Future<bool> _performHealthCheck() async {
  try {
    // Verify API connectivity
    final response = await http.get(
      Uri.parse('${config.backendUrl}/api/health'),
    );
    
    return response.statusCode == 200;
  } catch (e) {
    return false;
  }
}
```

--------------------------------

### Check Transaction Status

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/types.md

Example demonstrating how to check the status of a transaction using TransactionStatus constants after a charge. It covers successful, cancelled, and error states, and also shows direct string comparison.

```dart
import 'package:flutterwave_standard/flutterwave.dart';

// Check transaction status
final ChargeResponse response = await flutterwave.charge(context);

if (response.status == TransactionStatus.SUCCESSFUL) {
  print('Payment was successful');
  // Proceed with order completion
} else if (response.status == TransactionStatus.CANCELLED) {
  print('User cancelled payment');
  // Allow user to try again
} else if (response.status == TransactionStatus.ERROR) {
  print('Payment failed');
  // Show error message
}

// Or using direct string comparison
if (response.status == "successful") {
  // Transaction successful
}
```

--------------------------------

### Handle Charge Response

Source: https://github.com/flutterwave/flutter-v3/blob/master/README.md

Await the result of the `.charge()` method to get a `ChargeResponse`. This response object contains details about the payment's success or failure. Remember that `ChargeResponse` can be null if the user cancels the transaction.

```dart
final ChargeResponse response = await flutterwave.charge(context);
```

--------------------------------

### Apply Standard Build Settings

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/runner/CMakeLists.txt

Applies a standard set of build settings to the application target. This can be customized for applications with different build requirements.

```cmake
apply_standard_settings(${BINARY_NAME})
```

--------------------------------

### Apply Standard Build Settings

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/linux/runner/CMakeLists.txt

Applies a standard set of build settings to the specified target. This can be removed if custom build settings are required.

```cmake
# Apply the standard set of build settings. This can be removed for applications
# that need different build settings.
apply_standard_settings(${BINARY_NAME})
```

--------------------------------

### Link Dependencies and Include Directories

Source: https://github.com/flutterwave/flutter-v3/blob/master/example/windows/runner/CMakeLists.txt

Links necessary libraries (flutter, flutter_wrapper_app, dwmapi.lib) and sets the source directory as an include directory for the application target. Add any custom application-specific dependencies here.

```cmake
# Add dependency libraries and include directories. Add any application-specific
# dependencies here.
target_link_libraries(${BINARY_NAME} PRIVATE flutter flutter_wrapper_app)
target_link_libraries(${BINARY_NAME} PRIVATE "dwmapi.lib")
target_include_directories(${BINARY_NAME} PRIVATE "${CMAKE_SOURCE_DIR}")
```

--------------------------------

### Flutterwave Constructor

Source: https://github.com/flutterwave/flutter-v3/blob/master/_autodocs/api-reference/flutterwave.md

Initializes the Flutterwave SDK with essential details for processing payments. This includes API keys, transaction specifics, customer information, and customization options.

```APIDOC
## Constructor Flutterwave

### Description
Initializes the Flutterwave SDK with essential details for processing payments. This includes API keys, transaction specifics, customer information, and customization options.

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **publicKey** (String) - Required - Flutterwave API public key for authentication
- **txRef** (String) - Required - Unique transaction reference for idempotency
- **amount** (String) - Required - Transaction amount as a string
- **customer** (Customer) - Required - Customer information for the transaction
- **paymentOptions** (String) - Required - Comma-separated payment methods (e.g., "card, ussd, bank transfer")
- **customization** (Customization) - Required - UI customization options for the payment modal
- **redirectUrl** (String) - Required - URL to redirect after payment completion
- **isTestMode** (bool) - Required - If true, uses sandbox environment; if false, uses production
- **currency** (String) - Required - Transaction currency code (e.g., "NGN", "USD")
- **paymentPlanId** (String) - Optional - Payment plan ID for recurring payments
- **subAccounts** (List<SubAccount>) - Optional - Sub-accounts for split payments
- **meta** (Map<dynamic, dynamic>) - Optional - Additional metadata for the transaction

### Request Example
```dart
Flutterwave(
  publicKey: "YOUR_PUBLIC_KEY",
  txRef: "unique_tx_ref_123",
  amount: "100.50",
  customer: Customer(email: "user@example.com", name: "John Doe"),
  paymentOptions: "card, ussd",
  customization: Customization(title: "Pay Now"),
  redirectUrl: "https://example.com/callback",
  isTestMode: true,
  currency: "NGN"
)
```

### Response
#### Success Response (200)
Returns a new Flutterwave instance.

#### Response Example
```dart
// Instance of Flutterwave
```
```