# Hardhat Simple Storage 🚀 [![Solidity](https://img.shields.io/badge/Solidity-^0.8.8-black?logo=solidity&logoColor=white)](https://soliditylang.org/) [![Hardhat](https://img.shields.io/badge/Hardhat-2.x-FFF04D?logo=hardhat)](https://hardhat.org/) [![Yarn](https://img.shields.io/badge/yarn-1.22-2C8EBB?logo=yarn&logoColor=white)](https://yarnpkg.com/) > **A hands-on learning project** building and shipping Solidity smart contracts with **Hardhat** — from a local node all the way to a verified deployment on the **Sepolia testnet**. This is my personal study ground for Web 3.0 smart-contract development. --- ## 📌 What I Learned in This Project This repository documents my learning journey building smart contracts. Here's what it covers: | # | Concept | What I explored | |---|---------|-----------------| | 1 | **Solidity fundamentals** | Data types (`uint`, `int`, `address`, `string`, `bytes`), `state` vs `memory` vs `calldata`, `view`/`pure` functions, `structs`, `mappings`, `arrays` | | 2 | **Hardhat workflow** | Local blockchain node (`hardhat` & `ganache`), compile, deploy, `hardhat console`, custom `tasks` | | 3 | **Contract deployment** | Both the classic `scripts/` flow and the modern **hardhat-deploy** pattern with reusable `deploy/` scripts | | 4 | **Real-world oracle integration** | **Chainlink price feeds** to value donations in USD (`PriceConverter`, `FundMe`) with mock deployment for local testing | | 5 | **Testing** | Unit tests + **staging tests against Sepolia**, `--grep` filtering, coverage reports | | 6 | **Gas optimization** | Coding patterns to reduce gas (prefer `private`, use `constant`/`immutable`) — verified with `hardhat-gas-reporter` | | 7 | **Code quality** | `solhint` best-practice linting, `prettier` + `prettier-plugin-solidity` formatting | | 8 | **Block explorer verification** | Auto-verification of contracts on Etherscan | | 9 | **Version control** | Git + Gitea workflow for source control | | 10 | **Security awareness** | Studied historical exploited contracts via [rekt.news](https://rekt.news/leaderboard/) | --- ## 📦 Smart Contracts | Contract | Purpose | |----------|---------| | [`SimpleStorage.sol`](contracts/SimpleStorage.sol) | Core concepts: storage variables, data types, `structs`, `mappings`, `view`/`pure` functions | | [`FundMe.sol`](contracts/FundMe.sol) | Real-world pattern: accept ETH, track funders, withdraw with a minimum funding value in **USD** | | [`PriceConverter.sol`](contracts/PriceConverter.sol) | Library that converts ETH amounts to USD using a **Chainlink price feed** | --- ## ✅ Live Versions — Verified on Sepolia Testnet This project has been **successfully deployed AND verified** on the EthSepolia testnet: | Deployed via | Contract Address | Etherscan (verified) | |---|---|---| | `deploy.js` script | `0xc2022b56eBC140B5FebCf9FBaB14c17db4C315C4` | [View code](https://sepolia.etherscan.io/address/0xc2022b56eBC140B5FebCf9FBaB14c17db4C315C4#code) | | `yarn hardhat deploy --network sepolia` | `0x3a827C119e1D746bb3C7bcbbf95c55246C8CcBdd` | [View code](https://sepolia.etherscan.io/address/0x3a827C119e1D746bb3C7bcbbf95c55246C8CcBdd#code) | --- ## 🛠️ Tech Stack - **Solidity `^0.8.8`** — smart contract language (EVM-compatible: Ethereum, Avalanche, Fantom, Polygon) - **Hardhat 2.x** — development environment - **Ethers.js** — Ethereum JavaScript library - **hardhat-deploy** — cleaner deployment workflow - **Chainlink** — decentralized price feeds - **Node.js + Yarn** — package management --- ## 🚀 Getting Started ### Prerequisites - Node.js 18+ (this project used `nvm install 18`) - Yarn (`corepack enable`) - WSL on Windows (for the smoothest local setup) ### Install & Compile ```bash git clone https://github.com/hoelee/hardhat-simple-storage.git cd hardhat-simple-storage yarn add --dev hardhat prettier prettier-plugin-solidity dotenv \ @nomiclabs/hardhat-ethers@npm:hardhat-deploy-ethers ethers \ hardhat-gas-reporter solidity-coverage solhint yarn hardhat compile ``` ### Run Tests (Local) ```bash yarn hardhat test # unit tests yarn hardhat test --grep # run matching tests only yarn hardhat coverage # test coverage report ``` ### Local Development Node ```bash yarn hardhat node # run local blockchain in a dedicated terminal yarn hardhat console --network localhost # interactive Solidity REPL yarn hardhat deploy --tags mocks --network localhost # deploy local price-feed mocks ``` ### Deploy to Sepolia ```bash # classic script yarn hardhat run scripts/deploy.js --network sepolia # hardhat-deploy pattern yarn hardhat deploy --network sepolia ``` ### Gas Reporting & Code Quality ```bash yarn hardhat test # produces ./gas-report.txt when ETHERSCAN_API_KEY .env is set yarn solhint contracts/*.sol yarn prettier --write . # format Solidity + JS ``` --- ## 🧠 Key Takeaways (Gas Optimization) Working on-chain made me think hard about **cost**: - Prefer `private` over `public` — avoids auto-generated (and expensive) getters - Use `constant` / `immutable` for values set once at deploy time - Remember: blockchain storage (`store`) and retrieval (`read`) cost the most gas — minimize them > Blockchain charges a higher gas fee for storage operations than for bytecode; write minimal, optimized state. --- ## 📁 Project Structure ``` hardhat-simple-storage/ ├── contracts/ # Solidity source (SimpleStorage, FundMe, PriceConverter) ├── deploy/ # hardhat-deploy scripts (mocks, fund-me, storage) ├── deployments/ # Saved deployment artifacts per network (localhost, sepolia) ├── ignition/ # Hardhat Ignition module ├── scripts/ # Classic deploy / fund / withdraw scripts ├── tasks/ # Custom Hardhat tasks (e.g. block-number) ├── test/ # unit/ + staging/ (Sepolia) tests ├── utils/ # Shared utilities ├── helper-hardhat-config.js # Per-network config (price feeds, RPC URLs) └── hardhat.config.js # Hardhat configuration ``` --- ## ⚠️ Known Issues - The dependency combination is old — worth a dependency-upgrade pass. - Personal-study project; feel free to fork and improve it. **Found a bug or have an idea?** Open an issue using the issues tab above. 🙏 --- ## 🛡️ Security Note The [rekt.news leaderboard](https://rekt.news/leaderboard/) is a great reference for learning from real-world exploited contracts — every smart-contract developer should study it to avoid repeating the mistakes of the past. --- ## 💼 Looking for a Web 3.0 Developer? Hi, I'm **Mr Hoelee** 👋 — I enjoy building pragmatic, secure smart-contract solutions and I am **open to Web 3.0 remote work**. - 📱 WhatsApp: **+60 17-585 5290** ([click to chat](https://wa.me/60175885290)) - ✉️ Email: **[me@hoelee.com](mailto:me@hoelee.com)** - 📺 Portfolio: **[hoelee.com](https://hoelee.com)** I bring a full-stack background (PHP, Java, JavaScript) plus hands-on Blockchain (Solidity, Hardhat, ethers.js) experience to the table. Let's build something great together! --- ## ☕ Support If you find this project useful, you can [buy me a coffee](https://buymeacoffee.com/hoelee) — every cup fuels more learning. ⛽ --- ## 📄 License `UNLICENSED` — free to use, learn from, and build upon.