This is an educational project with the purpose of acquiring hands-on experience in web3 application development using smart contracts written in Solidity.
The Decentralized Lottery project consists of 2 parts:
Hardhat App: This component is responsible for managing smart contracts and includes deployment scripts, using the popular development environment for Ethereum smart contracts.
Next.js App: This part serves as the frontend of the application and interacts with on-chain logic within the Ethereum ecosystem.
The Decentralized Lottery is a blockchain-based lottery system. It integrates Chainlink's Verifiable Random Function (VRF) to ensure fair and random winner selection, Chainlink's Automation for triggers lottery ending, and includes features for player management, automated lottery upkeep, and secure prize distribution. The contract governs entry rules, maintains the lottery's operational state, and handles the drawing and announcement of winners in an autonomous and transparent manner.
- Solidity
- Chainlink (VRF, Automation)
- Hardhat
- Ethers.js
- Next.js
- Moralis
- IPFS
git clone https://github.com/v7m/decentralized-lottery-hardhat.git
cd decentralized-lottery-hardhat
yarn
yarn hardhat deploy
yarn hardhat test
yarn hardhat coverage
To check linting:
yarn hardhat check
- Setup environment variables
To get started, configure the following environment variables, SEPOLIA_RPC_URL and PRIVATE_KEY. You can store them in a .env file, similar to the example provided in .env.example.
PRIVATE_KEY: This should be the private key associated with your account. NOTE: For development purposes, please use a key that doesn't contain any real funds.SEPOLIA_RPC_URL: This is the URL of the Sepolia testnet node you're using. You can set up a free testnet node with Alchemy.
- Obtain testnet ETH
Visit faucets.chain.link to acquire some testnet ETH and LINK. Your newly acquired ETH and LINK will appear in your Metamask wallet.
- Setup a Chainlink VRF subscription ID
Go to vrf.chain.link and create a new subscription to obtain a subscription ID. If you already have one, you can reuse it. If you need guidance, you can follow the provided instructions here. After this step, you should have:
- A subscription ID
- Your subscription should be funded with LINK
- Deploy
Add your SEPOLIA_SUBSCRIPRION_ID to .env file.
Then run:
yarn hardhat deploy --network sepolia
And copy / remember the contract address.
- Add your contract address as a Chainlink VRF Consumer
Return to vrf.chain.link, and within your subscription, locate the option to Add consumer and insert your contract address. Additionally, ensure that the contract is funded with a minimum of 2 LINK tokens.
- Register a Chainlink Keepers Automation
Go to automation.chain.link and register a new upkeep. Select Custom logic as your trigger mechanism for automation, and make sure to fund the contract with a minimum of 8 LINK tokens.
- Enter lottery
Your contract is now configured as a tamper-proof, autonomously verifiable random lottery. Enter the lottery by running:
yarn hardhat run scripts/enter.js --network sepolia
Next, remove the comment from the line coinmarketcap: COINMARKETCAP_API_KEY in your hardhat.config.js to enable USD estimation. However, please be aware that every time you run your tests, it will consume an API call. Thus, so it might make sense to keep CoinMarketCap disabled until it's required, which can be done by commenting the line again.
If you're deploying to a testnet or the mainnet, you can enable contract verification by obtaining an API Key from Etherscan and configuring it as an environment variable called ETHERSCAN_API_KEY. Simply place it in your .env file following the example in .env.example.
As it stands, having your API key configured will enable automatic verification of Sepolia contracts.
However, you can manual verify with:
yarn hardhat verify --constructor-args arguments.js <DEPLOYED_CONTRACT_ADDRESS>