🌼 Token Vendor — SpeedRunEthereum Challenge

A minimal ERC-20 + vending machine dApp built with Scaffold-ETH 2 (Next.js + Viem + Wagmi + Hardhat). The app lets users buy your ERC-20, transfer it, and sell it back to the Vendor using the standard approve → transferFrom pattern.

This repository is a completed submission for the Token Vendor challenge on speedrunethereum.com.

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🚀 Live

• App: https://nextjs-llt7ljkl8-dormins-projects.vercel.app/
• Network: Sepolia (chain id 11155111)
• Contracts
  • Vendor — 0x98219Dc8ECAFDe3B5ed9dAd5DD8bc14963Dd0F87
  • YourToken — 0x35f5CB22E33E7063514a26b3D8680B3Bc86F8176

Paste any address above into a block explorer to view code/txs.

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✨ What’s inside

• YourToken.sol — ERC‑20 (OpenZeppelin). Fixed supply, minted in the constructor to deployer.
• Vendor.sol — Vending machine contract:
  • tokensPerEth = 100
  • buyTokens() payable — swaps ETH → tokens
  • sellTokens(uint256) — requires prior approve, swaps tokens → ETH
  • withdraw() — owner‑only, withdraws all ETH
  • Events: BuyTokens, SellTokens, Withdraw
• Deploy script transfers 1000 * 10**18 tokens to the Vendor and transfers Vendor ownership to the frontend/owner address.

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🛠 Quickstart (local)

Recommended Node: v20.18.x (Hardhat does not officially support Node 21).

# 1) Install deps (root)
yarn

# 2) Start local chain
cd packages/hardhat
yarn chain

# 3) In a new terminal: deploy locally
cd packages/hardhat
yarn deploy --reset

# 4) In a third terminal: start the dapp
cd packages/nextjs
yarn start
# open http://localhost:3000

Environment

packages/hardhat/.env

ALCHEMY_API_KEY=
ETHERSCAN_V2_API_KEY=
DEPLOYER_PRIVATE_KEY_ENCRYPTED={...}
FRONTEND_ADDRESS=0xyourOwnerWallet

packages/nextjs/.env.local (optional; defaults are provided)

NEXT_PUBLIC_ALCHEMY_API_KEY=
NEXT_PUBLIC_WALLET_CONNECT_PROJECT_ID=

Ensure .env* files are gitignored. Do not commit private keys or encrypted key blobs.

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🔍 Verify (optional)

From packages/hardhat:

yarn verify --network sepolia 0x35f5CB22E33E7063514a26b3D8680B3Bc86F8176   # YourToken (no args)
yarn verify --network sepolia 0x98219Dc8ECAFDe3B5ed9dAd5DD8bc14963Dd0F87  "0x35f5CB22E33E7063514a26b3D8680B3Bc86F8176"  # Vendor(tokenAddress)

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📋 How to use (on Sepolia)

1. Connect wallet (burner or MetaMask) on Sepolia.
2. Buy: enter tokens to buy → wallet pays amount / tokensPerEth ETH.
3. Transfer: send tokens to any address via transfer.
4. Sell: approve(Vendor, amount) then sellTokens(amount) to receive ETH back.

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🧩 Tech stack

• Solidity, Hardhat, hardhat‑deploy
• OpenZeppelin ERC20, Ownable
• Next.js (app router), Viem, Wagmi, RainbowKit
• Tailwind + daisyUI

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✅ Submission notes

• tokensPerEth hard‑coded to 100.
• Vendor preloaded with 1000 YTK in the deploy script.
• Vendor ownership transferred to FRONTEND_ADDRESS from .env.
• Frontend route: /token-vendor includes Buy / Transfer / Approve+Sell UX and shows balances.

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🔐 Security

• Addresses are public by design. Never commit private keys, mnemonics or the encrypted key JSON.
• Keep owner funds in a non‑burner wallet.

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📦 Scripts

# Deploy to Sepolia
cd packages/hardhat
yarn deploy --network sepolia --reset

# Verify on Sepolia (see Verify above)

# Build frontend
cd packages/nextjs
yarn build

# Deploy frontend to Vercel (once linked)
vercel --prod

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📄 License

MIT