Morgan ERC721 NFT Marketplace

A complete ERC721 NFT marketplace smart contract with minting, listing, buying, and platform fee distribution built with Hardhat + TypeScript and OpenZeppelin. Deployable to Sepolia and Base mainnet.

Features

• Minting: Anyone can mint NFTs with metadata URIs
• Listing: NFT owners can list their tokens for sale at any price
• Buying: Purchase listed NFTs with automatic fee distribution
• Platform Fees: Configurable platform fee percentage with designated recipient
• Events: Full event emission for Minted, Listed, Bought, Transfer, and admin actions
• Security: ReentrancyGuard protection and comprehensive validation

Quick Setup

1. Install dependencies

cd /Volumes/Work/2025/Wu/Morgan-ERC721/smart-contract
npm install

2. Configure environment

cp .env.example .env

Edit .env and set:

• PRIVATE_KEY: Your deployer wallet private key
• SEPOLIA_RPC_URL: Sepolia RPC endpoint (Alchemy/Infura)
• BASE_RPC_URL: Base mainnet RPC endpoint
• ETHERSCAN_API_KEY: For contract verification
• PLATFORM_FEE_RECIPIENT: Required - Address to receive platform fees
• PLATFORM_FEE_PERCENTAGE: Fee in basis points (default 250 = 2.5%)

3. Compile

npm run compile

4. Run tests

npm test

5. Deploy

Sepolia testnet:

npm run deploy:sepolia

Base mainnet:

npm run deploy:base

6. Interact with deployed contract

After deployment, add CONTRACT_ADDRESS to your .env, then:

npm run interact:sepolia
# or
npm run interact:base

Contract Functions

Minting

function mint(address to, string memory uri) external returns (uint256)

Mint a new NFT to any address with metadata URI.

Listing

function listNFT(uint256 tokenId, uint256 price) external
function cancelListing(uint256 tokenId) external

List your NFT for sale or cancel an active listing.

Buying

function buyNFT(uint256 tokenId) external payable

Purchase a listed NFT. Payment is split between seller and platform automatically.

Admin Functions (Owner Only)

function setPlatformFeePercentage(uint256 newFeePercentage) external
function setPlatformFeeRecipient(address newRecipient) external

Events

• Minted(uint256 tokenId, address to, string uri)
• Listed(uint256 tokenId, address seller, uint256 price)
• Bought(uint256 tokenId, address buyer, address seller, uint256 price, uint256 platformFee)
• ListingCancelled(uint256 tokenId, address seller)
• Transfer(address from, address to, uint256 tokenId) - Standard ERC721

Project Structure

• contracts/MyERC721.sol — Full marketplace contract with ERC721URIStorage, listing logic, and fee distribution
• scripts/deploy.ts — Deployment script with platform fee configuration
• test/sample-test.ts — Comprehensive test suite covering minting, listing, buying, and fee management
• hardhat.config.ts — Network configs for Sepolia and Base with Etherscan verification

Security Features

• ReentrancyGuard on purchase function
• Automatic listing cancellation on transfer
• Input validation on all state-changing functions
• Platform fee capped at 100%
• Overpayment refund mechanism

Usage Example

After deploying, interact with your contract:

// Mint an NFT
const tx = await contract.mint(userAddress, "ipfs://metadata-uri");
// Event: Minted(tokenId, userAddress, "ipfs://metadata-uri")

// List NFT for sale
await contract.listNFT(tokenId, ethers.parseEther("1.0"));
// Event: Listed(tokenId, sellerAddress, price)

// Buy listed NFT (from different account)
await contract.buyNFT(tokenId, { value: ethers.parseEther("1.0") });
// Event: Bought(tokenId, buyerAddress, sellerAddress, price, platformFee)
// Seller receives: price - (price * platformFeePercentage / 10000)
// Platform receives: price * platformFeePercentage / 10000

// Cancel listing
await contract.cancelListing(tokenId);
// Event: ListingCancelled(tokenId, sellerAddress)

See scripts/interact.ts for a complete working example.

Notes

• Platform fee is calculated in basis points (100 = 1%, 250 = 2.5%, 1000 = 10%)
• Listings are automatically cancelled when NFT is transferred
• Sellers receive price - platformFee, platform receives platformFee
• Uses @nomicfoundation/hardhat-toolbox with ethers v6
• Keep your private key secure and never commit .env