NexaPay - Cross-Chain Payment Platform

A decentralized payment platform that enables seamless cross-chain transactions using Stargate bridges, with automatic fee collection for testnet and mainnet networks.

Features

• 🌐 Cross-Chain Payments: Send payments across multiple EVM chains using Stargate bridges
• 💰 Automatic Fee Collection: 5% fee automatically deducted and sent to appropriate wallet based on network
• 🔄 Network Detection: Automatic detection of testnet vs mainnet for fee routing
• 🛡️ Secure: Smart contract-based payments with proper validation
• 📱 Modern UI: Beautiful, responsive interface built with Next.js and Tailwind CSS
• 🔐 Authentication: JWT-based authentication system
• 📊 Analytics: Real-time transaction tracking and analytics

Fee Collection System

The platform automatically collects a 5% fee on all transactions, with intelligent routing:

• Testnet Transactions: Fees sent to TESTNET_FEE_WALLET_ADDRESS
• Mainnet Transactions: Fees sent to MAINNET_FEE_WALLET_ADDRESS

Supported Networks

Mainnet Networks:

• Ethereum (Chain ID: 1)
• Polygon (Chain ID: 137)
• BSC (Chain ID: 56)
• Avalanche (Chain ID: 43114)
• Base (Chain ID: 8453)

Testnet Networks:

• Sepolia (Chain ID: 11155111)
• Mumbai/Polygon Testnet (Chain ID: 80001)
• BSC Testnet (Chain ID: 97)
• Fuji/Avalanche Testnet (Chain ID: 43113)

Quick Start

1. Clone the Repository

git clone <repository-url>
cd nexapay

2. Install Dependencies

npm install

3. Setup Environment Variables

Run the setup script to configure fee collection:

node scripts/setup-env.js

This will prompt you for:

• MAINNET_FEE_WALLET_ADDRESS: Your mainnet fee collection wallet
• TESTNET_FEE_WALLET_ADDRESS: Your testnet fee collection wallet
• FEE_PERCENTAGE: Fee percentage in basis points (default: 500 = 5%)

4. Deploy Smart Contract

# Deploy to testnet (recommended first)
npx hardhat run scripts/deploy.js --network sepolia

# Deploy to mainnet
npx hardhat run scripts/deploy.js --network polygon

5. Update Frontend Configuration

After deployment, update your .env file with the deployed contract address:

NEXT_PUBLIC_NEXAPAY_CONTRACT=0xYourDeployedContractAddress

6. Start Development Server

npm run dev

Environment Variables

Create a .env file with the following variables:

# Fee Collection Configuration
MAINNET_FEE_WALLET_ADDRESS=0xYourMainnetFeeWalletAddress
TESTNET_FEE_WALLET_ADDRESS=0xYourTestnetFeeWalletAddress
FEE_PERCENTAGE=500

# Contract Configuration
NEXT_PUBLIC_NEXAPAY_CONTRACT=0xYourDeployedContractAddress

# Database Configuration
MONGODB_URI=mongodb://localhost:27017/nexapay

# JWT Configuration
JWT_SECRET=your-jwt-secret-key-here

# Email Configuration
SMTP_HOST=smtp.gmail.com
SMTP_PORT=587
SMTP_USER=[email protected]
SMTP_PASS=your-app-password

# Environment
NODE_ENV=development

Smart Contract

NexaPayPayment.sol

The main smart contract that handles payments and fee collection:

• Automatic Network Detection: Uses block.chainid to determine testnet vs mainnet
• Fee Routing: Automatically sends fees to the appropriate wallet based on network
• Token Support: Configurable list of supported ERC20 tokens
• Owner Functions: Ability to update fee wallets, percentages, and supported tokens

Key Functions

• pay(): Process payment with automatic fee deduction
• setMainnetFeeWallet(): Update mainnet fee wallet (owner only)
• setTestnetFeeWallet(): Update testnet fee wallet (owner only)
• setFeePercentage(): Update fee percentage (owner only)
• setTokenSupport(): Add/remove supported tokens (owner only)

Fee Collection Examples

Testnet Transaction

// On Sepolia testnet
// Payment: 100 USDC
// Fee: 5 USDC (5%)
// Merchant receives: 95 USDC
// Fee sent to: TESTNET_FEE_WALLET_ADDRESS

Mainnet Transaction

// On Polygon mainnet
// Payment: 1000 USDT
// Fee: 50 USDT (5%)
// Merchant receives: 950 USDT
// Fee sent to: MAINNET_FEE_WALLET_ADDRESS

Development

Scripts

# Setup environment variables
node scripts/setup-env.js

# Deploy contract
npm run deploy

# Compile contracts
npx hardhat compile

# Run tests
npx hardhat test

# Start development server
npm run dev

Testing

1. Testnet Testing: Always test on testnet first
2. Fee Verification: Verify fees are sent to correct wallets
3. Cross-Chain Testing: Test payments across different networks
4. Token Support: Test with different ERC20 tokens

Security Considerations

• ✅ Fee wallets are set during deployment and can be updated by owner
• ✅ Fee percentage is capped at 10% (1000 basis points)
• ✅ Owner-only functions for critical updates
• ✅ Automatic network detection prevents fee routing errors
• ✅ Proper input validation and error handling

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Test thoroughly on testnet
5. Submit a pull request

License

MIT License - see LICENSE file for details

Support

For support and questions:

• Create an issue in the repository
• Check the documentation
• Review the smart contract code

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Note: Always test on testnet before deploying to mainnet. The fee collection system is designed to be secure and efficient, automatically routing fees to the appropriate wallets based on the network.