🎰 Ethereum Lottery Smart Contract

This project is a decentralized lottery smart contract built on Ethereum using Solidity and Hardhat. Players can enter the lottery by sending ETH, and a winner is randomly selected to receive the entire prize pool.

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🚀 Features

• Players enter by sending a fixed entry fee (e.g., 0.01 ETH)
• Random winner selection using block.prevrandao (PoS-compatible)
• Only the contract owner can trigger the lottery draw
• Fully tested using Hardhat & Chai
• Deployable on the Sepolia testnet

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1. Clone the repository:

   git clone https://github.com/DevFreAkeD/lottery-smart-contract.git
   cd lottery-smart-contract

2. Install dependencies:

   npm install

3. Set up Hardhat:

   npx hardhat

   Select "Create a basic sample project" if prompted.

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📜 Smart Contract (Solidity)

Create contracts/Lottery.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

contract Lottery {
    address public owner;
    address[] public players;
    uint public entryFee;
    
    constructor(uint _entryFee) {
        owner = msg.sender;
        entryFee = _entryFee;
    }

    function enter() public payable {
        require(msg.value == entryFee, "Incorrect entry fee");
        players.push(msg.sender);
    }

    function pickWinner() public onlyOwner {
        require(players.length > 0, "No players joined");
        uint winnerIndex = random() % players.length;
        address winner = players[winnerIndex];
        payable(winner).transfer(address(this).balance);
        delete players;
    }

    function random() private view returns (uint) {
        return uint(keccak256(abi.encodePacked(block.timestamp, block.prevrandao, players.length)));
    }

    modifier onlyOwner() {
        require(msg.sender == owner, "Only owner can call this");
        _;
    }
}

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🔧 Compile the Contract

Run:

npx hardhat compile

You should see "Compilation finished successfully".

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🚀 Deploy the Contract

Create scripts/deploy.js:

const hre = require("hardhat");

async function main() {
    const entryFee = hre.ethers.parseEther("0.01"); // 0.01 ETH entry fee
    const Lottery = await hre.ethers.getContractFactory("Lottery");
    const lottery = await Lottery.deploy(entryFee);
    await lottery.waitForDeployment();
    
    console.log(`Lottery deployed to: ${lottery.target}`);
}

main().catch((error) => {
    console.error(error);
    process.exitCode = 1;
});

Deploy Locally:

npx hardhat run scripts/deploy.js --network hardhat

Deploy on Sepolia Testnet:

1. Get Sepolia test ETH from:
   • Alchemy Faucet
   • QuickNode Faucet
2. Set up hardhat.config.js:

require("@nomicfoundation/hardhat-toolbox");

module.exports = {
  networks: {
    sepolia: {
      url: "https://eth-sepolia.g.alchemy.com/v2/YOUR_ALCHEMY_API_KEY",
      accounts: ["YOUR_PRIVATE_KEY"]
    }
  },
  solidity: "0.8.19",
};

3. Deploy:

npx hardhat run scripts/deploy.js --network sepolia

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✅ Run Tests

To ensure the contract works as expected, run:

npx hardhat test

Create test/Lottery.js:

const { expect } = require("chai");
const { ethers } = require("hardhat");

describe("Lottery", function () {
    let Lottery, lottery, owner, addr1, addr2;

    beforeEach(async function () {
        [owner, addr1, addr2] = await ethers.getSigners();
        Lottery = await ethers.getContractFactory("Lottery");
        lottery = await Lottery.deploy(ethers.parseEther("0.01"));
    });

    it("should allow players to enter", async function () {
        await lottery.connect(addr1).enter({ value: ethers.parseEther("0.01") });
        expect(await lottery.players(0)).to.equal(addr1.address);
    });

    it("should only allow the owner to pick a winner", async function () {
        await expect(lottery.connect(addr1).pickWinner()).to.be.revertedWith("Only owner can call this");
    });
});

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📢 Connect with Me

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