x402_dio

A Dio-based client library for the x402 payment protocol. It provides a Dio interceptor that automatically handles "402 Payment Required" flows across multiple blockchain ecosystems, currently supporting EVM (Ethereum) and SVM (Solana).

This package is an alternative to the main x402 package (which uses http). It leverages the power of Dio interceptors for seamless integration into existing Dio-based applications.

Features

• Dio Integration: Adds automatic x402 handling via the X402Interceptor.
• Multi-Chain Support: Uses x402 signers for EVM and SVM support.
• Automated Handshake: Simplifies the negotiation between client signers and server requirements.
• Flexible Configuration: Prioritize signers and add custom approval logic.

Getting Started

Add the dependencies to your pubspec.yaml:

dependencies:
  dio: ^5.9.0
  x402: ^0.1.0     # For signers (EvmSigner, SvmSigner)
  x402_dio: ^0.1.0 # For X402Interceptor

Usage

The primary way to use this package is by adding the X402Interceptor to your Dio instance.

Using X402Interceptor

The X402Interceptor detects 402 responses, finds a compatible signer from your provided list, signs the payment requirement, and automatically retries the request.

import 'package:dio/dio.dart';
import 'package:x402/x402.dart';
import 'package:x402_dio/x402_dio.dart';

void main() async {
  // 1. Setup your signers
  final evmSigner = EvmSigner.fromHex(
    chainId: 8453, 
    privateKeyHex: 'YOUR_EVM_PRIVATE_KEY',
  );
  
  final svmSigner = await SvmSigner.fromHex(
    privateKeyHex: 'YOUR_SVM_PRIVATE_KEY', 
    network: SolanaNetwork.devnet,
  );

  // 2. Configure Dio
  final dio = Dio();
  dio.interceptors.add(X402Interceptor(
    dio: dio,
    signers: [
      evmSigner, // The first signer is checked first
      svmSigner,
    ],
    // Optional: Ask for user confirmation before paying
    onPaymentRequired: (req, resource, signer) async {
      print('Payment of ${req.amount} required for ${resource.url}');
      return true; // Return true to approve, false to deny
    },
  ));

// 3. Make requests normally (402 is handled automatically by the interceptor)
try {
  final response = await dio.get('https://api.example.com/premium');

  if (response.statusCode == 200) {
    print('Success: ${response.data}');
    // HTTP 402 is fully handled by X402Interceptor (payment + retry),
    // so it will never reach this point and does not need to be checked here.
  } else {
    print('Unexpected status: ${response.statusCode}');
  }
} on DioException catch (e) {
  // You only end up here if:
  // - payment was denied
  // - payment signing failed
  // - no compatible signer was found
  // - the server still rejected the paid request
  if (e.response?.statusCode == 402) {
    print('Payment could not be completed');
  } else {
    print('Request failed: ${e.message}');
  }
}
}

Related Packages

• x402: The main client library (http-based).
• x402_core: Internal protocol definitions.
• x402_evm: EVM implementation details.
• x402_svm: SVM implementation details.