ERC721 Marketplace Contract

Contract Outline

State Variables

• uint public listingCounter: A counter to keep track of the number of listings.

Structs

• struct Listing: A struct representing an ERC721 listing with fields for the listingId, order creator, ERC721 token address, token ID, price, signature, deadline and isSold.

Mapping

• mapping(uint => Listing) public listings: A mapping that associates listing IDs with their respective Listing structs.

createListing Function

Parameters

• address _tokenAddress: The address of the ERC721 token.
• uint _tokenID: The token ID of the ERC721 token.
• uint _price: The price of the listing in ether.
• bytes memory _signature: The seller's signature of the order data.
• uint _deadline: The deadline for the listing.

Preconditions

• Owner Check:

  • Check that msg.sender is the owner of the token using ownerOf(_tokenID).

• Approval Check:

  • Check that msg.sender has approved the contract to spend the ERC721 token using isApprovedForAll(msg.sender, address(this)).

• Token Address Validation:

  • Check that _tokenAddress is not the zero address (address(0)).
  • Check if _tokenAddress has code (is a smart contract).

• Price Check:

  • Check that _price is greater than 0.

• Deadline Check:

  • Check that _deadline is greater than block.timestamp.

Logic

• Create a new Listing struct with the provided information.
• Increment listingCounter to generate a new listing ID.
• Store the Listing in the listings mapping using the new listing ID.

executeListing Function

Parameters

• uint _listingId: The ID of the listing to be executed.

Preconditions

• Listing ID Check:

  • Check that _listingId is less than listingCounter.

• Payment Check:

  • Check that msg.value is equal to the price of the listing.

• Deadline Check:

  • Check that block.timestamp is less than or equal to the listing's deadline.

• Signature Verification:

  • Verify that the _signature is signed by the listing's owner.

Logic

• Retrieve the Listing information from storage based on _listingId.
• Transfer ether from the buyer to the seller.
• Transfer the ERC721 token from the seller to the buyer.
• Mark the listing as completed (optional, but useful for preventing double purchases).