🎰 CryptoLottery DApp

A decentralized lottery application built with Next.js, Solidity, and Web3. Users can participate in a blockchain-based lottery by entering with 0.1 ETH, and the contract owner can pick a random winner who receives the entire pot.

🌟 Features

• Decentralized Lottery: Built on Ethereum blockchain using smart contracts
• Web3 Integration: Connect with MetaMask wallet
• Real-time Updates: Live lottery pot and player count updates
• Winner History: View previous lottery winners
• Responsive Design: Modern UI with CSS modules
• Gas Optimization: Efficient smart contract design

🏗️ Architecture

Frontend (Next.js)

• Framework: Next.js 12.2.5 with React 18
• Web3: Web3.js for blockchain interaction
• Styling: CSS Modules for component-specific styles
• State Management: React Context API for global state

Backend (Smart Contracts)

• Language: Solidity ^0.8.15
• Framework: Truffle for development and deployment
• Networks: Goerli and Sepolia testnets
• Provider: Infura for blockchain connectivity

📁 Project Structure

CryptoLottery/
├── backend/                    # Smart contract development
│   ├── contracts/
│   │   └── Lottery.sol        # Main lottery contract
│   ├── migrations/
│   │   └── 1_deploy.js        # Deployment script
│   ├── build/
│   │   └── contracts/
│   │       └── Lottery.json   # Compiled contract ABI
│   └── truffle-config.js      # Truffle configuration
├── components/                 # React components
│   ├── ConnectWalletBtn.js    # Wallet connection button
│   ├── Header.js              # App header
│   ├── LotteryCard.js       # Lottery information card
│   ├── Table.js              # Players table
│   ├── TableRow.js           # Individual table row
│   └── UserCard.js           # User information card
├── context/
│   └── context.js            # React context for state management
├── pages/
│   ├── _app.js               # Next.js app wrapper
│   ├── index.js              # Main lottery page
│   └── api/
│       └── hello.js          # API route
├── styles/                   # CSS modules
│   ├── globals.css           # Global styles
│   ├── Header.module.css     # Header styles
│   ├── Home.module.css       # Home page styles
│   ├── PotCard.module.css    # Pot card styles
│   ├── Table.module.css      # Table styles
│   └── TableRow.module.css   # Table row styles
├── utils/
│   ├── constants.js          # Contract constants
│   ├── Lottery.json          # Contract ABI
│   └── lotteryContract.js    # Contract interaction utilities
└── package.json              # Dependencies and scripts

🚀 Getting Started

Prerequisites

• Node.js (v14 or higher)
• npm or yarn
• MetaMask browser extension
• Truffle (for smart contract development)
• Goerli or Sepolia testnet ETH

Installation

1. Clone the repository

   git clone <repository-url>
   cd CryptoLottery

2. Install dependencies

   npm install
   # or
   yarn install

3. Set up environment variables Create a .env file in the backend directory with your wallet mnemonic:

   MNEMONIC=your_wallet_mnemonic_phrase_here
   INFURA_PROJECT_ID=your_infura_project_id
   

4. Deploy smart contracts

   cd backend
   truffle compile
   truffle migrate --network goerli  # or sepolia

5. Update contract address After deployment, update the contract address in utils/constants.js with the deployed contract address.

6. Start the development server

   npm run dev
   # or
   yarn dev

7. Open the application Navigate to http://localhost:3000 in your browser.

🎮 How to Use

For Players

1. Connect Wallet: Click "Connect Wallet" and approve the connection in MetaMask
2. Enter Lottery: Click "Enter Lottery" and confirm the 0.1 ETH transaction
3. View Status: See your entry in the players table and current lottery pot
4. Wait for Winner: The contract owner will pick a winner when ready

For Contract Owner

1. Connect as Owner: Use the owner wallet to connect
2. Pick Winner: Click "Pick Winner" to randomly select and pay the winner
3. View History: See all previous winners in the winners list

🔧 Smart Contract Details

Lottery Contract Functions

• enter(): Enter the lottery with 0.1 ETH minimum
• getPlayers(): Get list of current players
• getBalance(): Get current lottery pot
• getLotteryId(): Get current lottery round ID
• pickWinner(): Pick random winner (owner only)
• getWinners(): Get list of all winners

Security Features

• Access Control: Only contract owner can pick winners
• Minimum Entry: 0.1 ETH minimum to prevent spam
• Random Selection: Uses block timestamp and owner address for randomness
• Automatic Reset: Players array resets after each winner selection

🛠️ Development

Available Scripts

npm run dev      # Start development server
npm run build    # Build for production
npm run start    # Start production server
npm run lint     # Run ESLint

Smart Contract Development

cd backend
truffle compile          # Compile contracts
truffle test            # Run tests
truffle migrate         # Deploy to local network
truffle migrate --network goerli  # Deploy to Goerli

🌐 Network Configuration

The application is configured for:

• Goerli Testnet: Primary test network
• Sepolia Testnet: Alternative test network
• Infura: Blockchain node provider

📦 Dependencies

Frontend

• next: React framework
• react: UI library
• web3: Ethereum JavaScript API
• @truffle/hdwallet-provider: Wallet provider for Truffle
• truncate-eth-address: Address formatting utility

Backend

• truffle: Development framework
• @truffle/hdwallet-provider: HD wallet provider
• solc: Solidity compiler

🔒 Security Considerations

• Testnet Only: This is for testing purposes only
• Private Key Security: Never commit private keys or mnemonics
• Gas Limits: Set appropriate gas limits for transactions
• Randomness: Current randomness is not cryptographically secure
• Access Control: Only deploy with trusted owner addresses

🚀 Deployment

Frontend Deployment

1. Build the application: npm run build
2. Deploy to Vercel, Netlify, or your preferred platform
3. Update contract address for production network

Smart Contract Deployment

1. Update truffle-config.js with production network settings
2. Deploy to mainnet: truffle migrate --network mainnet
3. Verify contract on Etherscan
4. Update frontend with production contract address

🤝 Contributing

1. Fork the repository
2. Create a feature branch: git checkout -b feature-name
3. Commit changes: git commit -m 'Add feature'
4. Push to branch: git push origin feature-name
5. Submit a pull request

📄 License

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

⚠️ Disclaimer

This is a demonstration project for educational purposes. The lottery system uses pseudo-random number generation and should not be used for real money without proper security audits and improvements.

🆘 Support

For support and questions:

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

🔗 Links

• Next.js Documentation
• Truffle Documentation
• Web3.js Documentation
• MetaMask Documentation