xPay2

Problem Statement

This project extends the native capabilities of x402 by adding features like credit, early resource returns, and seamless monetization of any Web2 API — with any integration effort. xPay2 is a proxy service that adds payment functionality to any existing API without requiring code changes. Developers paste their backend URL, set a price, and get a paid public endpoint powered by the x402 protocol and USDC payments on Base.https://github.com/Ashar2shahid/xPay2

Solution

xPay2 - HTTP 402 Payment Gatewayhttps://github.com/Ashar2shahid/xPay2Turn any API into a paid service instantly with HTTP 402 Payment Required protocolxPay2 is a proxy service that adds payment functionality to any existing API without requiring code changes. Developers paste their backend URL, set a price, and get a paid public endpoint powered by the x402 protocol and USDC payments on Base.🚀 Features🔌 Zero Backend Integration- Works with any HTTP API, no code changes needed💳 HTTP 402 Protocol- Standards-compliant payment-required responses⚡ Credit System- Prepaid API usage with instant, gasless requests🔐 EIP-712 Signatures- Cryptographically secure authentication📊 Usage Analytics- Track all requests, payments, and settlements🌐 Multi-Chain Support- Base, Optimism, Arbitrum, Polygon💰 USDC Payments- Stable, predictable pricing🎯 Quick StartPrerequisitesNode.js 18+USDC on Base networkPrivate key with USDC balanceInstallation# Clone the repository git clone <repo-url> cd ethindia-xPay2 # Install dependencies npm install # Set up environment variables cp .env.example .env # Add your EVM_PRIVATE_KEY and ADDRESS to .env # Initialize the database npm run init-db # Start the development server npm run devCreate Your First Paid Endpoint# 1. Create a project with a paid endpoint curl -X POST http://localhost:3000/api/projects \ -H "Content-Type: application/json" \ -d '{ "name": "My API", "description": "My paid API service", "defaultPrice": 0.01, "currency": "USD", "payTo": "0xYourAddress", "paymentChains": ["base"], "endpoints": [{ "url": "https://api.example.com", "path": "/data", "method": "GET", "price": 0.01, "description": "Get data endpoint" }] }' # 2. Your proxy URL is now live! # http://localhost:3000/api/proxy/{project-slug}/data # 3. Requests without payment return 402 curl http://localhost:3000/api/proxy/{project-slug}/data # Returns: 402 Payment Required with payment instructions # 4. Use x402-fetch to make paid requests # See examples/ directory for client code💡 Credit SystemThe credit system enables prepaid API usage with instant, gasless requests:How It WorksOverpay once- Pay $0.05 for a $0.01 endpointGet $0.04 in credits- Automatically stored in your accountUse credits instantly- Make requests with zero-value signaturesNo gas fees- Credit usage skips on-chain settlementExample Flow// First request: Pay $0.05 for $0.01 endpoint // → Creates $0.04 in credits // Subsequent requests: Use zero-value authentication // → Deducts $0.01 from credits (now $0.03) // → Instant response, no on-chain transaction // → No gas fees // Continue until credits depleted // → System returns 402 asking for paymentEnable Credits# Enable credits for an endpoint curl -X PATCH http://localhost:3000/api/endpoints/{endpoint-id} \ -H "Content-Type: application/json" \ -d '{ "creditsEnabled": true, "minTopupAmount": 0.01 }'🧪 TestingRun the comprehensive test suite:node e2e-test.jsTest Coverage:✅ 20/20 tests passingBasic payment flowCredit creation via overpaymentZero-value authenticationCredit exhaustion handlingEdge cases (invalid signatures, expired timestamps)🏗️ Architecture┌─────────────┐ │ Client │ │ (x402-fetch)│ └──────┬──────┘ │ X-Payment: <signature> ▼ ┌─────────────────────────────────┐ │ xPay2 Proxy │ │ ┌──────────────────────────┐ │ │ │ 1. Verify Payment │ │ │ │ - EIP-712 signature │ │ │ │ - Credit balance │ │ │ └──────────────────────────┘ │ │ ┌──────────────────────────┐ │ │ │ 2. Forward Request │ │ │ │ - Add headers │ │ │ │ - Proxy to backend │ │ │ └──────────────────────────┘ │ │ ┌──────────────────────────┐ │ │ │ 3. Settle Payment │ │ │ │ - On-chain (if paid) │ │ │ │ - Skip (if credits) │ │ │ └──────────────────────────┘ │ └────────┬────────────────────────┘ │ Response + Receipt ▼ ┌─────────────────┐ │ Your Backend │ │ (no changes!) │ └─────────────────┘🔧 API ReferenceCreate ProjectPOST /api/projects Content-Type: application/json { "name": "My API", "description": "API description", "defaultPrice": 0.02, "currency": "USD", "payTo": "0xYourAddress", "paymentChains": ["base"], "endpoints": [...] }Enable CreditsPATCH /api/endpoints/{endpointId} Content-Type: application/json { "creditsEnabled": true, "minTopupAmount": 0.01 }Make Paid RequestGET /api/proxy/{project-slug}/{endpoint-path} X-Payment: <base64-encoded-x402-payment>📊 Response HeadersAll proxied requests include tracking headers:X-Proxy-Payment-Status- Payment verification statusX-Proxy-Settlement-Status- On-chain settlement statusX-Credit-Balance- Remaining credit balance (if credits enabled)X-Credit-Used- Whether credits were used for this requestX-Credit-Total-Deposited- Total credits ever depositedX-Credit-Total-Spent- Total credits ever spent🛠️ Tech StackNext.js- Pages Router for API routesSQLite + Drizzle ORM- Lightweight databaseviem- Ethereum interactions and EIP-712 signingx402- HTTP 402 protocol implementationBigNumber.js- Precise decimal arithmeticBase Network- Layer 2 for cheap USDC transfers🔐 Security FeaturesEIP-712 Signature VerificationFull cryptographic verification of all signaturesValidates against USDC's EIP-712 domainTimestamp validation (validAfter/validBefore)Nonce-based replay protectionBigNumber ArithmeticEliminates JavaScript floating-point errorsEnsures exact credit calculationsPrevents balance discrepanciesExample:// Without BigNumber ❌ 0.03 - 0.01 = 0.019999999999999997 // With BigNumber ✅ new BigNumber(0.03).minus(0.01) = 0.02📝 Environment Variables# Required EVM_PRIVATE_KEY=0x... # Private key for settlement ADDRESS=0x... # Address to receive payments # Optional FACILITATOR_URL=https://facilitator.coinbase.com ENABLE_SETTLEMENT=true # Enable on-chain settlement NEXT_PUBLIC_APP_URL=http://localhost:3000🚀 Deployment# Build for production npm run build # Start production server npm start # Or deploy to Vercel vercel deploy📚 ExamplesSee theexamples/directory for:Client implementation with x402-fetchCredit usage patternsError handlingMulti-endpoint projects🤝 ContributingContributions welcome! Please readCfor development guidelines.📄 LicenseMIT🔗 LinksxBUEBuilt with ❤️ for ETHIndia 2024