Hardhat Smartcontract Lottery

A tamper proof autonomous verifiably random lottery
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Table of Contents

1. About The Project
   • Built With
2. Getting Started
   • Prerequisites
   • Quickstart
3. Usage
4. Testing
   • Coverage
5. Deployment to a testnet or mainnet
   • Estimate gas cost in USD
   • Verify on etherscan
6. Linting

About The Project

This is a decentralized automated lottery using Chainlink Automation and Chainlink VRF, hardhat, solidity, typescript.

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Built With

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Getting Started

Prerequisites

• git
  • You'll know you did it right if you can run git --version and you see a response like git version x.x.x
• Nodejs
  • You'll know you've installed nodejs right if you can run:
    • node --version and get an ouput like: vx.x.x
• Yarn instead of npm
  • You'll know you've installed yarn right if you can run:
    • yarn --version and get an output like: x.x.x
    • You might need to install it with npm or corepack

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Quickstart

git clone https://github.com/guillaumedebavelaere/hardhat-smartcontract-lottery
cd hardhat-smartcontract-lottery
yarn

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Usage

yarn hardhat deploy

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Testing

yarn hardhat test

Coverage

yarn hardhat coverage

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Deployment to a testnet or mainnet

1. Setup environment variabltes

You'll want to set your GOERLI_RPC_URL and PRIVATE_KEY as environment variables. You can add them to a .env file.

• PRIVATE_KEY: The private key of your account (like from metamask).
• GOERLI_RPC_URL: This is url of the goerli testnet node you're working with. You can get setup with one for free from Alchemy

1. Get testnet ETH

Head over to faucets.chain.link and get some tesnet ETH & LINK.

1. Setup a Chainlink VRF Subscription ID

Head over to vrf.chain.link and setup a new subscription, and get a subscriptionId. You can reuse an old subscription if you already have one.

You can follow the instructions if you get lost. You should leave this step with:

1. A subscription ID

2. Your subscription should be funded with LINK

3. Deploy

In your .env add a variable GOERLI_SUBSCRIPTION_ID filled with the subscription id.

Then run:

yarn hardhat deploy --network goerli

And copy / remember the contract address.

1. Add your contract address as a Chainlink VRF Consumer

Go back to vrf.chain.link and under your subscription add Add consumer and add your contract address. You should also fund the contract with a minimum of 1 LINK.

5. Register a Chainlink Keepers Upkeep

You can follow the documentation if you get lost.

Go to automation.chain.link and register a new upkeep. Choose Custom logic as your trigger mechanism for automation.

1. Enter your lottery!

You're contract is now setup to be a tamper proof autonomous verifiably random lottery. Enter the lottery by running:

yarn hardhat run scripts/enter.ts --network goerli

Estimate gas cost in USD

To get a USD estimation of gas cost, you'll need a COINMARKETCAP_API_KEY environment variable. You can get one for free from CoinMarketCap.

Then, uncomment the line coinmarketcap: COINMARKETCAP_API_KEY, in hardhat.config.js to get the USD estimation. Just note, everytime you run your tests it will use an API call, so it might make sense to have using coinmarketcap disabled until you need it. You can disable it by just commenting the line back out.

Verify on etherscan

If you deploy to a testnet or mainnet, you can verify it if you get an API Key from Etherscan and set it as an environemnt variable named ETHERSCAN_API_KEY. You can pop it into your .env file as seen in the .env.example.

In it's current state, if you have your api key set, it will auto verify goerli contracts!

However, you can manual verify with:

yarn hardhat verify --constructor-args arguments.js DEPLOYED_CONTRACT_ADDRESS

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Linting

To check linting / code formatting:

yarn lint

or, to fix:

yarn lint:fix

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