Building a Decentralized Lottery on Avalanche

This document tracks the development process of the Lotto dApp, designed to facilitate learning blockchain development.

Tech Stack Choices

• Blockchain: Avalanche (AVAX) - Chosen for high throughput and community adoption.
• Smart Contract Framework: Hardhat - Industry standard for Ethereum/EVM development.
• Interaction Library: Viem - A modern, lightweight, and type-safe alternative to Ethers.js.
• Frontend: React (via Vite) - Fast and popular web framework.

Note: For detailed syntax and usage examples of the blockchain tools (Viem, Hardhat, Ignition), see BLOCKCHAIN_DEV_REFERENCE.md.

Architecture

Smart Contract (Lotto.sol)

The core logic resides here.

• State Variables:
  • ticketPrice: Cost to enter.
  • lotteryEnd: Timestamp when the lottery closes.
  • players: Array of addresses that entered.
• Functions:
  • enter(): Payable function to join.
  • pickWinner(): Selects a winner and transfers funds.

Randomness Note

True randomness is difficult on deterministic blockchains. In production, we would use Chainlink VRF (Verifiable Random Function). For this learning exercise, we will use a pseudo-random number generator using block difficulty/timestamp. Warning: This is exploitable by miners/validators in high-stakes environments but acceptable for a simple learning project.

Yield Strategy (Stretch Goal)

To separate concerns, we can use a "Strategy" pattern. The Lotto contract holds funds, but delegate them to a strategy contract that interacts with Aave/Benqi. For the MVP, we will use a BasicStrategy that just holds the funds.

Guide: Want to implement this? Check out the YIELD_INTEGRATION_GUIDE.md for a deep dive into integrating Aave and Yield Yak.

Development Log

1. Setup: Initialized Hardhat project with Viem.
2. Contract: Implemented Lotto.sol with entry and winner picking logic.
3. Testing: Wrote and verified tests in test/Lotto.ts covering:
   • Deployment parameters.
   • Player entry.
   • Ticket price validation.
4. Frontend: Scaffolding React application...