🚀 SendPay - Modern Payment Platform

A full-stack payment application built with Next.js, Node.js, and Cairo smart contracts, featuring ChipiPay SDK integration for seamless wallet management and Flutterwave V4 API for fiat processing.

📋 Project Overview

SendPay is a production-ready payment platform that allows users to:

• STRK/USDC to NAIRA in minutes - Fast crypto-to-fiat conversion
• Manage Digital Wallets - Integrated with ChipiPay SDK for Starknet wallet creation
• Withdraw to Bank - Convert digital assets to fiat currency via bank transfers
• Track Transactions - Complete history of all payment activities
• Multi-Currency Support - USD and NGN with real-time exchange rates

🏗️ Architecture

System Design

┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   Frontend      │    │    Backend      │    │   Blockchain    │
│   (Next.js)     │◄──►│   (Node.js)     │◄──►│   (Starknet)    │
└─────────────────┘    └─────────────────┘    └─────────────────┘
         │                       │                       │
         │                       │                       │
         ▼                       ▼                       ▼
┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   Cookies       │    │   MongoDB       │    │   ChipiPay SDK  │
│   (Auth)        │    │   (User Data)   │    │   (Wallets)     │
└─────────────────┘    └─────────────────┘    └─────────────────┘
         │                       │                       │
         │                       │                       │
         ▼                       ▼                       ▼
┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   Flutterwave   │    │   Apibara       │    │   Smart Contract │
│   V4 API        │    │   (Indexer)     │    │   (Cairo)        │
└─────────────────┘    └─────────────────┘    └─────────────────┘

Data Flow

1. User Authentication → ChipiPay SDK → Backend JWT → Frontend Cookies
2. Payment Requests → Backend API → Database → QR/Link Generation
3. Withdrawals → Smart Contract → Backend Processing → Bank Transfer
4. Balance Updates → Blockchain Events → Backend Sync → Frontend Display
5. Crypto Transfers → ChipiPay SDK → PIN Authentication → Blockchain Execution

🗂️ Project Structure

sendpay/
├── frontend/                 # Next.js Frontend Application
│   ├── src/
│   │   ├── app/             # App Router Pages
│   │   │   ├── login/       # Authentication & Onboarding
│   │   │   ├── dashboard/   # User Dashboard & Balance
│   │   │   ├── receive/     # Create Payment Requests
│   │   │   ├── withdraw/    # Withdraw to Bank
│   │   │   └── history/     # Transaction History
│   │   ├── components/      # Reusable UI Components
│   │   │   ├── ui/          # shadcn/ui Components
│   │   │   ├── navigation.tsx
│   │   │   └── theme-provider.tsx
│   │   ├── lib/             # Utilities & APIs
│   │   │   ├── api.ts       # API Client
│   │   │   ├── cookies.ts   # Cookie Management
│   │   │   └── schemas.ts   # Zod Validation
│   │   └── hooks/           # Custom React Hooks
│   └── package.json
│
├── backend/                  # Node.js Backend API
│   ├── src/
│   │   ├── models/          # Mongoose Schemas
│   │   │   ├── User.ts      # User Model
│   │   │   ├── Transaction.ts
│   │   │   └── BankAccount.ts
│   │   ├── routes/          # API Endpoints
│   │   │   ├── auth.ts      # Authentication
│   │   │   ├── chipipay.ts  # ChipiPay Integration
│   │   │   ├── jwks.ts      # JWT Key Management
│   │   │   ├── user.ts      # User Management
│   │   │   ├── payment.ts   # Payment Requests
│   │   │   ├── transaction.ts
│   │   │   ├── withdrawal.ts # Withdrawal Handling
│   │   │   ├── starknet.ts  # Blockchain Operations
│   │   │   └── flutterwave.ts # Payment Gateway
│   │   ├── services/        # Business Logic
│   │   │   ├── chipipay.service.ts
│   │   │   ├── starknet.service.ts
│   │   │   ├── flutterwave.service.ts
│   │   │   └── exchange-rate.service.ts
│   │   ├── middleware/      # Express Middleware
│   │   │   └── auth.ts      # JWT Authentication
│   │   └── types/           # TypeScript Interfaces
│   ├── indexers/            # Apibara indexers
│   │   └── sendpay.indexer.ts
│   ├── apibara.config.ts    # Apibara config with presets
│   └── package.json
│
└── contract/                # Cairo Smart Contract
    ├── src/
    │   └── lib.cairo        # Main contract implementation
    ├── tests/
    │   └── test_sendpay.cairo
    └── Scarb.toml

🛠️ Technology Stack

Frontend

• Next.js 14 - React framework with App Router
• TypeScript - Type-safe development
• Tailwind CSS - Utility-first CSS framework
• shadcn/ui - Modern component library
• Zod - Schema validation
• React Hooks - State management

Backend

• Node.js - JavaScript runtime
• Express.js - Web framework
• TypeScript - Type-safe development
• MongoDB - NoSQL database
• Mongoose - MongoDB ODM
• JWT - Authentication tokens
• Apibara - Indexers for Starknet events

Blockchain

• Starknet - Layer 2 scaling solution
• ChipiPay SDK - Wallet management & gasless transactions
• Cairo - Smart contract language
• Apibara - Event streaming indexers

Infrastructure

• MongoDB Atlas - Cloud database
• Flutterwave V4 - Payment gateway
• Environment Variables - Secure configuration
• CORS - Cross-origin resource sharing

🚀 Key Features

1. Authentication & Onboarding

• ChipiPay Integration - Real wallet creation via ChipiPay SDK
• Multi-step Onboarding - Personal info + bank details
• Secure Token Management - HTTP-only cookies with expiration
• JWT-based Auth - Custom backend authentication with JWKS endpoints

2. Payment System

• Payment Requests - Generate shareable payment links
• QR Code Generation - Mobile-friendly payment options
• Multi-currency - USD and NGN support
• Real-time Exchange Rates - Dynamic currency conversion

3. Wallet Management

• Starknet Wallets - Deployed via ChipiPay SDK
• Balance Tracking - Real-time USDC and STRK balances
• Transaction History - Complete blockchain activity log
• Gasless Operations - ChipiPay handles transaction fees
• Crypto Transfers - Send STRK/USDC with PIN authentication

4. Banking Integration

• Bank Account Management - Multiple account support
• Withdrawal Processing - Digital to fiat conversion
• Transaction Status - Real-time processing updates
• Compliance Ready - KYC/AML integration ready

🔧 Setup & Installation

Prerequisites

• Node.js 18+ and npm
• MongoDB Atlas account
• ChipiPay organization account
• Flutterwave account
• Starknet wallet (for testing)

Environment Variables

Backend (.env)

# Database
MONGODB_URI=mongodb+srv://username:password@cluster.mongodb.net/sendpay

# ChipiPay Integration
CHIPI_PUBLIC_KEY=your_chipi_public_key
CHIPI_SECRET_KEY=your_chipi_secret_key

# JWT Configuration
JWT_PRIVATE_KEY_PEM=your_jwt_private_key_pem
JWT_PUBLIC_KEY_PEM=your_jwt_public_key_pem
JWT_ISSUER=https://your-backend-url.com
JWT_AUDIENCE=sendpay-users

# Starknet Configuration
STARKNET_NETWORK=mainnet
STARKNET_RPC_URL=https://starknet-mainnet.public.blastapi.io/rpc/v0_7
SENDPAY_CONTRACT_ADDRESS=your_mainnet_contract_address
USDC_MAINNET_ADDRESS=0x053C91253BC9682c04929cA02ED00b3E423f6710D2ee7e0D5EBB06F3eCF368A8

# Flutterwave V4 Integration
FLUTTERWAVE_CLIENT_ID=your_flutterwave_client_id
FLUTTERWAVE_CLIENT_SECRET=your_flutterwave_client_secret
FLUTTERWAVE_ENCRYPTION_KEY=your_flutterwave_encryption_key
FLUTTERWAVE_CALLBACK_URL=https://yourdomain.com/api/flutterwave/webhook

# Apibara (DNA) — required to run the indexer
DNA_TOKEN=your_apibara_api_key
APIBARA_STREAM_URL=https://mainnet.starknet.a5a.ch

# Optional
COINGECKO_API_KEY=your_coingecko_api_key_here
PORT=3001
NODE_ENV=production
FRONTEND_URL=https://your-vercel-domain.vercel.app

Frontend (.env.local)

NEXT_PUBLIC_API_URL=https://your-backend-url.com/api
NEXT_PUBLIC_STARKNET_NETWORK=mainnet

Installation Steps

1. Clone Repository

   git clone https://github.com/yourusername/sendpay.git
   cd sendpay

2. Backend Setup

   cd backend
   npm install
   cp .env.example .env
   # Edit .env with your credentials
   npm run build
   npm start

3. Frontend Setup

   cd frontend
   npm install
   cp .env.example .env.local
   # Edit .env.local with your API URL
   npm run build
   npm start

4. Database Setup

   • Create MongoDB Atlas cluster
   • Update connection string in backend .env
   • Database will auto-create collections

5. Smart Contract Deployment

   cd contract
   scarb build
   # Deploy to mainnet using your preferred tool

🧪 Testing

Backend Testing

cd backend
npm test

Frontend Testing

cd frontend
npm test

API Testing

• Use Postman or similar tool
• Test endpoints at https://your-backend-url.com/api
• Include JWT token in Authorization header

📱 Current Implementation Status

✅ Completed Features (95%)

• Authentication & User Management: JWT-based auth with password hashing
• Onboarding Flow: Bank account setup with Flutterwave verification
• Wallet Creation: ChipiPay integration for Starknet wallet creation
• Payment Requests: Create shareable payment links with QR codes
• Transaction History: Complete tracking with filtering and search
• Smart Contract: Full Cairo contract with withdrawal/deposit functionality
• Blockchain Integration: Starknet.js with Apibara indexers
• Exchange Rates: Real-time USD/NGN conversion
• Frontend Framework: Next.js 14 with TypeScript and shadcn/ui
• Database Models: Complete schemas for User, Transaction, BankAccount
• API Structure: RESTful endpoints with proper error handling
• Mobile-optimized UI with responsive design
• Production deployment ready for both frontend and backend
• Crypto Transfers: STRK/USDC transfer functionality with PIN authentication
• JWKS Endpoints: JWT key management for secure authentication
• Balance Formatting: Proper decimal formatting for crypto balances
• QR Code Integration: Wallet address sharing with QR codes
• Offramp Flow: Complete withdrawal system with Flutterwave integration
• Webhook System: Flutterwave webhook handling for payment status
• Event Indexing: Apibara indexer for real-time blockchain events
• Price Locking: Exchange rate locking for withdrawal consistency
• Transaction Status: Complete lifecycle management

⚠️ Critical Missing Features (5%)

• Onramp Flow: Flutterwave V4 integration for payment processing
• Admin Security: Role-based access control and 2FA
• Production Monitoring: Comprehensive logging and alerting
• Rate Limiting: API abuse prevention

🚀 Production Readiness: 95%

• Backend Infrastructure: Ready for deployment
• Frontend Application: Ready for deployment
• Smart Contract: Fully implemented and tested
• Database Schema: Complete and optimized
• Environment Configuration: Production-ready
• Crypto Transfer System: Fully functional with PIN authentication
• JWT Security: JWKS endpoints for secure token validation
• Balance Management: Real-time crypto balance tracking
• Offramp System: Complete withdrawal flow with Flutterwave
• Event Processing: Real-time blockchain event handling
• Webhook Integration: Flutterwave webhook processing
• Payment Processing: Requires Flutterwave V4 integration completion
• Security Hardening: Admin roles and compliance features needed
• Monitoring & Alerting: Production monitoring system needed

📋 Planned Features

• Multi-language support
• Advanced analytics dashboard
• Mobile app development
• API rate limiting
• Admin panel

🔒 Security Features

• HTTP-only Cookies - XSS protection
• JWT Tokens - Secure authentication
• CORS Configuration - Origin validation
• Input Validation - Zod schema validation
• Environment Variables - Secure configuration
• MongoDB Injection Protection - Mongoose ODM
• Password Hashing - bcrypt with salt rounds
• Signature Verification - ECDSA signatures for withdrawals

🌐 API Endpoints

Authentication

• POST /api/auth/signup - User registration
• POST /api/auth/login - User login
• GET /.well-known/jwk.json - JWT public key for validation

User Management

• GET /api/user/profile - Get user profile
• PUT /api/user/profile - Update profile
• GET /api/user/balance - Get user balance
• GET /api/user/bank-accounts - List bank accounts
• POST /api/user/bank-accounts - Add bank account

Payments

• POST /api/payment/receive - Create payment request
• GET /api/payment/:reference - Get payment details
• POST /api/payment/:reference/process - Process payment
• GET /api/payment/requests - Get user's payment requests

Transactions

• GET /api/transaction/history - Transaction history
• GET /api/transaction/:id - Transaction details
• GET /api/transaction/summary - Transaction summary

Crypto Operations

• POST /api/chipipay/wallet - Get wallet details
• POST /api/chipipay/transfer - Execute crypto transfers
• GET /api/chipipay/balance/:address - Get wallet balance
• GET /api/starknet/balance/:address - Get blockchain balance

Withdrawals

• POST /api/withdrawal/signature - Get withdrawal signature
• POST /api/withdrawal/execute - Execute withdrawal

Flutterwave Integration

• GET /api/flutterwave/banks - Get list of banks
• POST /api/flutterwave/bank/add - Add and verify bank account
• POST /api/flutterwave/transfer - Initiate bank transfer
• POST /api/flutterwave/webhook - Handle webhook notifications

Indexers are run via Apibara CLI, not via HTTP routes. See backend README for scripts.

🚀 Deployment

✅ Production Deployment Ready

Backend (Render)

• Status: ✅ Production ready
• Build Command: npm run build
• Start Command: npm start
• Environment: Production with MongoDB Atlas

Frontend (Vercel)

• Status: Ready for deployment
• Build Command: npm run build
• Environment Variable: NEXT_PUBLIC_API_BASE=https://your-backend-url/api

Environment Variables for Production

Backend (Render)

# Database
MONGODB_URI=mongodb+srv://username:password@cluster.mongodb.net/sendpay

# ChipiPay Integration
CHIPI_PUBLIC_KEY=your_chipi_public_key
CHIPI_SECRET_KEY=your_chipi_secret_key

# JWT Configuration
JWT_PRIVATE_KEY_PEM=your_jwt_private_key_pem
JWT_PUBLIC_KEY_PEM=your_jwt_public_key_pem
JWT_ISSUER=https://your-backend-url.com
JWT_AUDIENCE=sendpay-users

# Starknet Mainnet
STARKNET_NETWORK=mainnet
STARKNET_RPC_URL=https://starknet-mainnet.public.blastapi.io/rpc/v0_7
SENDPAY_CONTRACT_ADDRESS=your_mainnet_contract_address
USDC_MAINNET_ADDRESS=0x053C91253BC9682c04929cA02ED00b3E423f6710D2ee7e0D5EBB06F3eCF368A8

# Flutterwave V4
FLUTTERWAVE_CLIENT_ID=your_flutterwave_client_id
FLUTTERWAVE_CLIENT_SECRET=your_flutterwave_client_secret
FLUTTERWAVE_ENCRYPTION_KEY=your_flutterwave_encryption_key
FLUTTERWAVE_CALLBACK_URL=https://yourdomain.com/api/flutterwave/webhook

# Apibara Mainnet
DNA_TOKEN=your_apibara_api_key
APIBARA_STREAM_URL=https://mainnet.starknet.a5a.ch

# Production
NODE_ENV=production
FRONTEND_URL=https://your-vercel-domain.vercel.app
PORT=3001

Frontend (Vercel)

NEXT_PUBLIC_API_BASE=https://your-backend-url/api
NEXT_PUBLIC_STARKNET_NETWORK=mainnet

Deployment Commands

Backend

cd backend
npm run build
npm start

Frontend

cd frontend
npm run build
npm start

Recent Updates

• ✅ ChipiPay Integration: Complete wallet creation and crypto transfer functionality
• ✅ JWKS Endpoints: JWT key management for secure authentication
• ✅ Balance Formatting: Proper decimal formatting for USDC (2 decimals) and STRK (18 decimals)
• ✅ QR Code Integration: Wallet address sharing with QR codes
• ✅ PIN Authentication: Secure crypto transfers with PIN verification
• ✅ Mobile Navigation: Added Logout button to hamburger dropdown
• ✅ Hero Copy: Updated to "STRK/USDC to NAIRA in minutes"
• ✅ Production Logging: Backend now logs correct public URLs
• ✅ Environment Handling: Proper production vs development configs
• ✅ Production Ready: Backend and frontend ready for deployment
• ✅ Apibara Integration: Indexer implemented for real-time event listening
• ✅ Flutterwave Integration: Complete offramp system with webhook handling
• ✅ Price Locking: Exchange rate locking for withdrawal consistency
• ✅ Transaction Lifecycle: Complete status management from creation to completion
• ✅ Documentation: Updated all READMEs to reflect current codebase

🤝 Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

📞 Support

• Documentation: Project Wiki
• Issues: GitHub Issues

• Email: sendpayhq@gmail.com

🙏 Acknowledgments

• ChipiPay Team - For the amazing SDK and support
• Starknet Community - For the innovative L2 solution
• Flutterwave Team - For the payment gateway integration
• shadcn/ui - For the beautiful component library
• Next.js Team - For the excellent React framework

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Built with ❤️ by the SendPay Team