NFT Marketplace

​NFT Marketplace is a decentralized NFT exchange that allows users to buy any ERC-721 compatible NFTs with coins and tokens.
These are the goals we had in mind when designing the protocol:
  • Make it as accessible as possible to sellers by not requiring them to perform blockchain transactions when listing their NFTs for sale, hence saving on gas fees.
  • Pay royalties by implementing the ERC-2981 standard as well as our own solution detailed in the IERC721Autentica interface.
  • Temporarily suspend the smart contract in the event of an emergency.
,-.
`-'
/|\
,-. | ,-.
`-' / \ `-'
/|\ /|\
,-. | Investor |
`-' / \ ^ / \
/|\ |
| Creator pay Autentica
/ \ ^ investor ^ ,-.
| [2] | `-'
Seller | pay | pay | /|\
^ +- creator ---+-- Autentica --+ |
| [1] | $$$$$$$$$$ / \
| | $ $
| | +------$ tradeForCoins lt;------+ Buyer ^
| +------------------------------+ | $ $ | +-----------------+ | |
| | | | $$$$$$$$$$ | | | | |
| | | | +--------| canPerformTrade |<--------+ |
| | | | | | | |
+--- pay owner -----| NFT Marketplace |<-----+ $$$$$$$$$$ | +-----------------+ |
| | | | $ $ | |
| | | +------$ tradeForTokens lt;------+ |
| | | $ $ |
| +--------------------------+---+ $$$$$$$$$$ |
| ^ | |
| | | |
+----approves marketplace ----------+ +--------------------------------------- sends NFT ---------------------------------+
* [1] the creator is payed if he is no longer the owner and the royalties are set to >0%
* [2] the investor is payed from creator's proceeds only if the NFT was minted by an investor

The smart contract's main public functions are canPerformTrade, tradeForCoins and tradeForTokens. All of these functions are meant to be called by the Buyer via Autentica Marketplace. The first function called canPerformTrade is used to check if the user is allowed to perform a trade using the specified parameters, while the remaining two functions, tradeForCoins and tradeForTokens are used to perform an actual trade using coins (the native cryptocurrency of the platform, i.e.: ETH) or tokens (i.e.: AUT/USDT/USDC).
Behind the scenes, tradeForCoins and tradeForTokens functions are actually calling canPerformTrade and determine whether or not the user is allowed to perform a trade with the specified parameters, but the reason for why canPerformTrade is exposed publicly is to allow the user to check if the trade is possible without actually performing it. This avoids having to pay gas fees if the transaction fails due to unmet conditions.

canPerformTrade is executed to check if the user is allowed to perform a trade using the specified parameters.
/**
* @notice Validate the trade.
*
* @param collection The ERC-721 smart contract.
* @param tokenId The unique identifier of the ERC-721 token within the `collection` smart contract.
* @param price The price of the NFT in `token` tokens.
* @param currency The type of currency (ERC-20 or native currency)
* @param buyer Buyer address.
* @param marketplaceFee Marketplace fee.
* @param signature ECDSA signature.
*
*/
function canPerformTrade(
address collection,
uint256 tokenId,
uint256 price,
address currency,
address buyer,
uint256 marketplaceFee,
Signature calldata signature
) public view returns (bool)
This function validates the following conditions:
  • The smart contract is not paused;
  • The collection smart contract is a valid ERC-721 smart contract;
  • The owner approved this smart contract to transfer the NFT identified by tokenId on their behalf;
  • The royalty fee for the creator and marketplaceFee do not exceed 100%;
  • The ECDSA signature that encodes all these parameters and a few others has been signed by an authorized user.

/**
* @notice Trades an NFT for a given amount of coins (the native cryptocurrency of the platform, i.e.: ETH).
*
* @param collection The ERC-721 smart contract.
* @param tokenId The unique identifier of the ERC-721 token within the `collection` smart contract.
* @param price The price of the NFT in coins.
* @param buyer Buyer address.
* @param marketplaceFee Marketplace fee.
* @param signature ECDSA signature.
*
* @dev Requirements
*
* - The `collection` smart contract must be an ERC-721 smart contract.
* - The owner of the NFT identified by `tokenId` within the `collection` smart contract must have approved
* this smart contract to manage its NFTs.
* - The `price` and `msg.value` must be equal.
* - The sum of all the fees cannot be greater than 100%.
* - The ECDSA signature must be signed by someone with the admin or operator role.
*/
function tradeForCoins(
address collection,
uint256 tokenId,
uint256 price,
address buyer,
uint256 marketplaceFee,
Signature calldata signature
) external payable nonReentrant
This function performs the following actions:
  • Guards against reentrancy;
  • Executes canPerformTrade to validate the parameters;
  • Sends the proceeds to each party involved if the amount is greater than zero:
    • Owner: The owner of the NFT;
    • Investor:
      • The investor who minted the NFT on behalf of the creator.
      • Note: The investor is payed from the proceeds of the creator.
    • Creator: The creator of the NFT if the royalty fee is greater than 0% and the creator is no longer the owner.
    • Marketplace: The Autentica Marketplace.
  • Transfers the NFT to the buyer.
  • Emits the TradedForCoins event.

/**
* @notice Trades an NFT for a given amount of ERC-20 tokens (i.e.: AUT/USDT/USDC).
*
* @param collection The ERC-721 smart contract.
* @param tokenId The unique identifier of the ERC-721 token within the `collection` smart contract.
* @param price The price of the NFT in `token` tokens.
* @param token The ERC-20 smart contract.
* @param buyer Buyer address.
* @param marketplaceFee Marketplace fee.
* @param signature ECDSA signature.
*
* Requirements:
*
* - The `collection` smart contract must be an ERC-721 smart contract.
* - The owner of the NFT identified by `tokenId` within the `collection` smart contract must have approved
* this smart contract to manage its NFTs.
* - The sum of all the fees cannot be greater than 100%.
* - The ECDSA signature must be signed by someone with the admin or operator role.
*/
function tradeForTokens(
address collection,
uint256 tokenId,
uint256 price,
address token,
address buyer,
uint256 marketplaceFee,
Signature calldata signature
) external nonReentrant
​
This function performs the following actions:
  • Guards against reentrancy;
  • Validates that the ERC-20 token address is allowed to be used for trading;
  • Executes canPerformTrade to validate the parameters;
  • Sends the proceeds to each party involved if the amount is greater than zero:
    • Owner: The owner of the NFT;
    • Investor:
      • The investor who minted the NFT on behalf of the creator.
      • Note: The investor is payed from the proceeds of the creator.
    • Creator: The creator of the NFT if the royalty fee is greater than 0% and the creator is no longer the owner.
    • Marketplace: The Autentica Marketplace.
  • Transfers the NFT to the buyer.
  • Emits the TradedForTokens event.

/**
* @dev Emitted when a trade occured between the `seller` (the owner of the ERC-721 token
* represented by `tokenId` within the `collection` smart contract) and `buyer` which
* payed the specified `price` in coins (the native cryptocurrency of the platform, i.e.: ETH).
*/
event TradedForCoins(
address indexed collection,
uint256 indexed tokenId,
address indexed seller,
address buyer,
uint256 price,
uint256 ownerProceeds,
uint256 creatorProceeds,
uint256 investorProceeds
);

/**
* @dev Emitted when a trade occured between the `seller` (the owner of the ERC-721 token
* represented by `tokenId` within the `collection` smart contract) and `buyer` which
* payed the specified `price` in tokens that are represented by the `token`
* ERC-20 smart contract address.
*/
event TradedForTokens(
address indexed collection,
uint256 indexed tokenId,
address indexed seller,
address buyer,
address token,
uint256 price,
uint256 ownerProceeds,
uint256 creatorProceeds,
uint256 investorProceeds
);

The source code for the smart contract can be found in the NFTMarketplace.sol file located in the contracts folder within our smart-contracts repository.

Network
Address
Binance Smart Chain
Ethereum (Rinkeby)
Binance Smart Chain (testnet)
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