UserProfileRegistry Smart Contract

A decentralized user profile management system built with Solidity that allows users to register, update, and retrieve their profiles on the Ethereum blockchain.

📋 Table of Contents

• Overview
• Features
• Contract Structure
• Functions
• Events
• Getting Started
• Usage Examples
• Security Considerations
• License

🔍 Overview

The UserProfileRegistry contract provides a simple and secure way to store user profile information on the blockchain. Each Ethereum address can register one unique profile containing personal information such as name, email, age, and a custom user ID.

✨ Features

• User Registration: Register a new user profile with personal details
• Profile Updates: Modify existing profile information
• Profile Retrieval: Get profile data for any registered user
• Registration Verification: Check if a user is registered
• Event Logging: Track registration and update activities
• Access Control: Users can only update their own profiles

🏗️ Contract Structure

UserProfile Struct

struct UserProfile {
    uint256 userId;                    // Custom user identifier
    uint256 age;                      // User's age
    string name;                      // User's name
    string email;                     // User's email address
    uint256 registrationTimestamp;    // When the profile was created
    bool isRegistered;                // Registration status
}

State Variables

• mapping(address => UserProfile) public profiles - Stores user profiles
• mapping(address => bool) public isRegistered - Tracks registration status

📝 Functions

Core Functions

registerUser()

function registerUser(string memory _name, uint256 _userId, uint256 _age, string memory _email) public

Registers a new user profile. Each address can only register once.

Parameters:

• _name: User's full name
• _userId: Custom user identifier
• _age: User's age
• _email: User's email address

Requirements:

• User must not be already registered

updateProfile()

function updateProfile(string memory _name, uint256 _userId, uint256 _age, string memory _email) public

Updates an existing user profile.

Parameters:

• Same as registerUser()

Requirements:

• User must be registered

getProfile()

function getProfile(address _user) external view returns (uint256, string memory, string memory, uint256, uint256)

Retrieves complete profile information for a given address.

Returns:

• User ID, name, email, age, registration timestamp

fetchUserInfo()

function fetchUserInfo(address _user) external view returns (string memory, string memory, uint256, uint256)

Alternative getter function for basic profile information.

Returns:

• Name, email, age, user ID

Utility Functions

isUserRegistered()

function isUserRegistered(address _user) external view returns (bool)

Checks if a user is registered.

getUserCount()

function getUserCount() external view returns (uint256)

Returns total number of registered users (placeholder implementation).

📢 Events

UserRegistered

event UserRegistered(address indexed user, string name, uint256 timestamp)

Emitted when a new user registers.

UserUpdated

event UserUpdated(address indexed user, string name)

Emitted when a user updates their profile.

🚀 Getting Started

Prerequisites

• Remix IDE or local development environment
• MetaMask or similar Ethereum wallet
• Test ETH for deployment (Sepolia, Goerli, or local testnet)

Deployment

1. Using Remix:

   • Open Remix IDE
   • Create a new file UserProfileRegistry.sol
   • Paste the contract code
   • Compile with Solidity ^0.8.17
   • Deploy using Injected Provider (MetaMask)

2. Using Hardhat/Truffle:

   # Install dependencies
   npm install
   
   # Compile contracts
   npx hardhat compile
   
   # Deploy to testnet
   npx hardhat run scripts/deploy.js --network sepolia

💡 Usage Examples

JavaScript (Web3.js)

// Register a new user
await contract.methods.registerUser(
    "John Doe",
    12345,
    25,
    "john@example.com"
).send({ from: userAddress });

// Update profile
await contract.methods.updateProfile(
    "John Smith",
    12345,
    26,
    "johnsmith@example.com"
).send({ from: userAddress });

// Get profile data
const profile = await contract.methods.getProfile(userAddress).call();
console.log(profile);

Solidity Integration

// Import and use in another contract
import "./UserProfileRegistry.sol";

contract MyDApp {
    UserProfileRegistry registry;
    
    constructor(address _registryAddress) {
        registry = UserProfileRegistry(_registryAddress);
    }
    
    function checkUser(address _user) public view returns (bool) {
        return registry.isUserRegistered(_user);
    }
}

🔒 Security Considerations

• Access Control: Users can only update their own profiles
• Input Validation: Consider adding validation for email format and name length
• Reentrancy: Current functions are safe from reentrancy attacks
• Gas Optimization: Profile updates could be optimized to only change specific fields

Recommended Improvements

• Add input validation (email format, name length limits)
• Implement profile deletion functionality
• Add admin controls for emergency situations
• Consider using OpenZeppelin's security patterns

🧪 Testing

Test the contract thoroughly before mainnet deployment:

// Test registration
it("should register a new user", async () => {
    await registry.registerUser("Test User", 1, 25, "test@example.com");
    const isRegistered = await registry.isUserRegistered(accounts[0]);
    assert.equal(isRegistered, true);
});

// Test duplicate registration prevention
it("should prevent duplicate registration", async () => {
    await registry.registerUser("Test User", 1, 25, "test@example.com");
    await expectRevert(
        registry.registerUser("Test User 2", 2, 30, "test2@example.com"),
        "User already registered"
    );
});

📄 License

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

🤝 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

📞 Support

If you have questions or need help:

• Open an issue on GitHub
• Check the Solidity documentation
• Visit Ethereum Stack Exchange

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⚠️ Disclaimer: This contract is for educational purposes. Perform thorough testing and security audits before using in production.