Raffle Contract

Overview

This repository contains a smart contract for a decentralized raffle system built on the Ethereum blockchain using Solidity. The contract leverages Chainlink VRF (Verifiable Random Function) v2.5 for random number generation to ensure fairness in selecting the raffle winner.

Table of Contents

• Raffle Contract
  • Overview
  • Table of Contents
  • Getting Started
    • Prerequisites
    • Installation
    • Deployment on Ethereum Sepolia
    • Interactions
    • Testing
  • Contract Details
    • Raffle Contract
      • State Variables
      • Functions
      • Events
  • License

Getting Started

These instructions will help you set up the project on your local machine for development and testing purposes.

Prerequisites

• Node.js
• npm
• Foundry
• A web3 wallet, such as Metamask
• A small balance of Sepolia $ETH and $LINK: These can be acquired from faucets.

Installation

Clone the repository and install the necessary dependencies:

git clone https://github.com/yourusername/raffle-contract.git
cd raffle-contract
make install

Deployment on Ethereum Sepolia

To deploy the smart contract on Ethereum Sepolia, you need to configure environment variables and deploy the contract using Foundry.

Ideally, you would create your own Chainlink VRF subscription on Ethereum Sepolia network and add your own admin public key address and VRF subscription ID into the config file.

However, you are free to use my Chainlink subscription. If the LINK balance drops to low, shoot me a message and I will top it up.

1. Create a keystore that encrypts and stores your private key securely:

cast wallet import <keystore account name> –interactive

You will need to type in your private key and then a password that you must remember to decrypt the private key later.

2. Create a .env file in the project root and add your environment variables:

SEPOLIA_RPC_URL=<Your Sepolia RPC URL>
ACCOUNT=<Your keystore account name>
ETHERSCAN_API_KEY=<Your Etherscan API Key>

3. Deploy the contract the contract on Sepolia:

make deploy-sepolia

You will need to enter the aforementioned keystore password to complete the deployment

4. Automate upkeep of the contract (resetting the contract state for a new raffle after a previous one has completed):

Go to https://automation.chain.link/, connect your wallet, and select "Register new Upkeep".

Select "Custom Logic", click "Next", provide a name for your contract, enter an initial amount of LINK to fund the Upkeep with (there is a link to a faucet, in case you don't have any testnet LINK), and then click "Register Upkeep". Your web3 wallet will prompt you to send a transaction and sign a message. Your Upkeep is now setup and maintenance of the contract is automated. Congrats!

Interactions

The repository contains scripts to interact with the deployed contract.

1. Create a subscription:

forge script script/CreateSubscription.s.sol:CreateSubscription --broadcast

2. Fund the subscription:

forge script script/FundSubscription.s.sol:FundSubscription --broadcast

3. Add a consumer:

forge script script/AddConsumer.s.sol:AddConsumer --broadcast

Testing

To run the tests, use the following command:

forge test

Contract Details

Raffle Contract

The Raffle contract allows users to buy tickets and enter a raffle. The contract uses Chainlink VRF v2.5 for random number generation to ensure fairness.

State Variables

• i_entranceFee: The cost to enter the raffle.
• i_interval: The duration of the raffle in seconds.
• i_keyHash: The gas lane key hash.
• i_subscriptionId: The subscription ID for the VRF coordinator.
• i_callbackGasLimit: The gas limit for the callback.
• s_lastTimeStamp: The last time the raffle was run.
• s_players: The array of addresses of players in the raffle.
• s_recentWinner: The address of the most recent winner.
• s_raffleState: The state of the raffle (OPEN or CALCULATING).

Functions

• enterRaffle: Allows users to enter the raffle by paying the entrance fee.
• checkUpkeep: Checks if the raffle is ready to pick a winner.
• performUpkeep: Requests random words from the VRF coordinator.
• fulfillRandomWords: Picks a winner and transfers the prize.

Events

• RaffleEntered: Emitted when a player enters the raffle.
• WinnerPicked: Emitted when a winner is picked.
• RequestedRaffleWinner: Emitted when a random word request is made.

License

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