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This project is a comprehensive cross-chain payment gateway that enables seamless token exchanges across multiple blockchain networks using 1inch's Fusion SDK. The platform provides both same-chain and cross-chain payment solutions, allowing merchants to accept payments in any supported token while receiving their preferred token on their desired blockchain.

Key Features: • Cross-chain payments: Users can pay with tokens on one chain (e.g., WBNB on BSC) while merchants receive different tokens on another chain (e.g., USDC on Ethereum) • Same-chain swaps: Direct token exchanges within the same blockchain network • Multi-chain support: Supports Ethereum, BSC, Polygon, Arbitrum, Optimism, Avalanche, Base, and more • Merchant dashboard: Complete order management system with real-time status tracking • User authentication: Secure JWT-based authentication with email verification • Order history: Comprehensive tracking of all payment transactions • Real-time price feeds: Live USD pricing for accurate payment calculations • Wallet integration: MetaMask and other Web3 wallet support with automatic network switching

The platform acts as a bridge between different blockchain ecosystems, solving the liquidity and cross-chain interoperability challenges that merchants face when accepting cryptocurrency payments. Merchants can specify their preferred receiving token and chain, while customers can pay with whatever tokens they have available, making crypto payments as seamless as traditional payment methods.

Technology Stack: • Frontend: React 18 + TypeScript + Vite + Tailwind CSS • Backend: Node.js + Express + TypeScript • Database: MongoDB with Mongoose ODM • Authentication: JWT tokens with HTTP-only cookies • Blockchain Integration: 1inch Fusion SDK v2.3.8 + Cross-chain SDK v1.0.2 • Web3 Libraries: Ethers.js v6 + Wagmi + RainbowKit • Wallet Connection: MetaMask integration with automatic network switching • Deployment: Render cloud platform

Architecture Deep Dive:

1. Cross-Chain Payment Flow:

   • Uses 1inch Fusion SDK's hub-and-spoke model with HashLock mechanisms
   • Implements secret-based atomic swaps for secure cross-chain transfers
   • Creates merkle tree structures for multi-fill orders
   • Automatic network switching and token approval handling

2. State Management:

   • Frontend uses React Context for authentication state
   • Backend implements order mapping system linking merchant orders to 1inch quotes
   • Real-time order status tracking with automated checker jobs
   • MongoDB stores order history, user data, and payment mappings

3. Security Implementation:

   • JWT authentication with secure HTTP-only cookies
   • CORS configuration for cross-origin requests
   • Input validation using Zod schemas
   • Rate limiting on API endpoints
   • Secure secret generation for atomic swaps

4. Notable Technical Solutions:

   a) Cross-Chain Order Validation:

   • Built custom validation layer to ensure order parameters match between frontend and 1inch API
   • Implements chain ID and token address verification
   • Handles token balance checking before approvals

   b) Price Oracle Integration:

   • Real-time USD price fetching across multiple chains
   • Supports price calculations for cross-chain value matching
   • Handles different token decimals and precision

   c) Network Management:

   • Dynamic network configuration for 15+ blockchain networks
   • Automatic RPC endpoint management
   • Fallback mechanisms for network switching

   d) Order Lifecycle Management:

   • Creates unique mappings between merchant orders and 1inch quotes
   • Implements background jobs for order status monitoring
   • Handles partial fills and multi-step atomic swaps

5. Partner Technology Benefits:

   • 1inch Fusion SDK: Provides best price execution and MEV protection
   • 1inch Cross-chain SDK: Enables atomic cross-chain swaps without bridges
   • MongoDB: Scales seamlessly for order and user management
   • Render: Provides reliable cloud deployment with automatic scaling

6. Hacky/Notable Implementations:

   • Custom proxy middleware that intercepts 1inch API calls to inject merchant order validation
   • Dynamic contract address management for Limit Order Protocol across chains
   • Secret hash generation using browser crypto API for client-side security
   • Automatic token approval optimization to prevent unnecessary gas costs
   • Environment variable management for seamless local/production deployment

The project successfully bridges the gap between traditional payment expectations and Web3 capabilities, making cross-chain payments accessible to both merchants and customers without requiring deep blockchain knowledge.