🗓️ DailyCheckIn – Wallet-Based Attendance DApp

A simple decentralized daily check-in application built with Solidity and deployed on the Ethereum Testnet.
This project demonstrates how blockchain can securely record user attendance using wallet-based authentication, ensuring transparency, immutability, and decentralization.

📜 Project Description DailyCheckIn allows users to mark their daily attendance through their crypto wallet.
Each wallet address can check in once every 24 hours, and the record is stored permanently on-chain.

This project is ideal for beginners learning Solidity and exploring wallet authentication, timestamp validation, and on-chain record keeping.
It can easily be extended to build loyalty systems, streak trackers, or community engagement tools.

⚙️ What It Does

• Users connect their wallet (e.g., MetaMask).
• Each wallet can check in once per day.
• The smart contract records the timestamp of each user’s last check-in.
• Anyone can view their latest check-in time and verify activity on-chain.
• The contract maintains the total number of check-ins performed by all users.

In simple terms — it’s a Web3 attendance system powered by smart contracts.

🌟 Features 🧠 Beginner-Friendly: Clean, well-commented Solidity code that’s easy to understand.
🔒 One Check-In Per Day: Prevents multiple submissions within 24 hours.
⛓️ Fully On-Chain: Every check-in is verifiable through blockchain explorers.
💼 Wallet-Based Authentication: No sign-up or password needed — your wallet is your identity.
📊 Global Tracking: Tracks the total number of check-ins recorded.
⚙️ Upgradeable Design: Perfect base for adding rewards, streaks, or gamification later.

📄 Smart Contract Language: Solidity ^0.8.20
Framework: Remix / Hardhat Compatible
Network: Ethereum Testnet

Deployed Contract:
0x55D2e8369Fabd459c93ea267Ba702CcE157B3f55
View on Etherscan:
https://etherscan.io/address/0x55D2e8369Fabd459c93ea267Ba702CcE157B3f55

💻 Smart Contract Code // SPDX-License-Identifier: MIT pragma solidity ^0.8.0;

/* Daily Check-In Smart Contract

• Users can check in once per day (based on block timestamp)
• The contract stores when each wallet last checked in
• Anyone can view their last check-in time
• Owner can view total check-ins */

contract DailyCheckIn { address public owner;

// Mapping to store each user's last check-in timestamp
mapping(address => uint256) public lastCheckIn;

// Count total number of check-ins
uint256 public totalCheckIns;

// Event that logs every successful check-in
event CheckedIn(address indexed user, uint256 time);

constructor() {
    owner = msg.sender; // deployer is the owner
}

// Function for users to check in
function checkIn() public {
    // Get the last check-in time
    uint256 lastTime = lastCheckIn[msg.sender];

    // Ensure the user can only check in once per day (86400 seconds)
    require(
        block.timestamp - lastTime >= 1 days,
        "You can only check in once per day"
    );

    // Update their last check-in time
    lastCheckIn[msg.sender] = block.timestamp;

    // Increase total check-in counter
    totalCheckIns++;

    // Emit event
    emit CheckedIn(msg.sender, block.timestamp);
}

// View function: check if user already checked in today
function hasCheckedInToday(address _user) public view returns (bool) {
    if (block.timestamp - lastCheckIn[_user] < 1 days) {
        return true;
    }
    return false;
}

// View function: get time since last check-in
function timeSinceLastCheckIn(address _user) public view returns (uint256) {
    if (lastCheckIn[_user] == 0) return 0;
    return block.timestamp - lastCheckIn[_user];
}

}

🚀 How to Run Locally

1. Clone the Repository
   git clone https://github.com/your-username/dailycheckin.git
   cd dailycheckin

2. Open Remix IDE
   Visit https://remix.ethereum.org
   Create a new file: DailyCheckIn.sol
   Paste the smart contract code above

3. Compile & Deploy
   Select Solidity Compiler version ^0.8.20
   Choose Injected Web3 (MetaMask) as the environment
   Click Deploy and confirm the transaction in MetaMask

4. Interact with the Contract
   checkIn() – Record your daily attendance
   hasCheckedInToday(address) – Check if a user has already checked in
   lastCheckIn(address) – View your most recent check-in timestamp

🧩 Future Enhancements

• Streak Tracking: Count consecutive check-in days per wallet
• Reward System: Distribute tokens or NFTs for consistent check-ins
• Frontend Dashboard: Build a React-based UI to visualize check-in data
• Calendar Integration: Show check-in history and activity logs
• Identity Verification: Optional off-chain or DID-based user verification

🙌 Acknowledgments Ethereum Testnet for contract deployment
Remix IDE for smart contract testing and deployment
Etherscan for blockchain record verification and transparency

Pro Tip: Start small — deploy locally, test features, then build your frontend. Every transaction is a step toward mastering Web3.

Made with ❤️ by Ashu
Track your day, the Web3 way.