Flashloan with NFTs

A proof of concept project to show how do a flashloan with NFTs. Loosely based on EIP-3156

Design Requirements

1. The owner of the NFT effectively keeps their NFT in their wallet at all times
2. The owner can set and is paid a premium when anyone uses their NFT
3. Premiums are settled in ether
4. A borrower can temporary move a token to their wallet

Interfaces

IERC721FlashLoanFacilitator.sol

interface IERC721FlashLoanFacilitator {
    /**
     * @dev Receive a flash loan. Must return the borrowed token before returning.
     * @param _tokenContract The addresses of the ERC721 contract to loan
     * @param _tokenId The NFT token id to loan
     * @param _owner The original owner of the token
     * @param _premium The additional amount of tokens to repay.
     * @param _params Variadic packed params to pass to the receiver as extra information
     * @return True if the execution was successful
     */
    function executeOperation(
        address _tokenContract,
        uint256 _tokenId,
        address _owner,
        uint256 _premium,
        bytes calldata _params
    ) external returns (bool);
}

IERC721FlashLoan.sol

interface IERC721FlashLoan {
    /**
     * @dev The premium to be charged to loan the NFT.
     * @param _tokenContract The addresses of the ERC721 contract to loan
     * @param _tokenId The NFT token id to loan
     * @return The amount of ether needed to complete the flashloan
     */
    function getPremiumForToken(
        address _tokenContract,
        uint256 _tokenId
    ) external view returns (uint256);

    /**
     * @dev Allows the msg.sender access to an approved NFT through a smartcontract within one transaction,
     * @param _facilitatorAddress The address of the contract implementing the IERC721FlashLoanFacilitator interface
     * @param _tokenContract The addresses of the ERC721 contract to loan
     * @param _tokenId The NFT token id to loan
     * @param _params Variadic packed params to pass to the receiver as extra information
     **/
    function flashLoan( address _facilitatorContract, address _tokenContract, uint256 _tokenId, bytes calldata _params) external payable;
}

Workflow

Setup

1. Deploy the flashloan contract like FlashLoanNFT.sol

For the NFT lender

1. NFT lender calls the NFT contract's setApprovalForAll({flashloan_contract_address}, true)
2. NFT lender calls the flashloan contract's approveForFlashLoans method and sets a premium for each NFT he/she wants to enable for flashloan.

For the NFT borrower

1. Deploy a facilitator contract like NFTWithRedeemableFlashLoanFacilitator
2. Call NFT contract's setApprovalForAll({facilitators_contract_address}, true)
3. Call the flashloan contract's flashloan method with the necessary premium
4. Profit!

Installing

npm install

Testing

npm test

Deloying the FlashLoanNFT contract

npx hardhat deploy