interface IERC3156FlashLender {

    /**
     * @dev The amount of currency available to be lended.
     * @param token The loan currency.
     * @return The amount of `token` that can be borrowed.
     */
    function maxFlashLoan(
        address token
    ) external view returns (uint256);

    /**
     * @dev The fee to be charged for a given loan.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @return The amount of `token` to be charged for the loan, on top of the returned principal.
     */
    function flashFee(
        address token,
        uint256 amount
    ) external view returns (uint256);

    /**
     * @dev Initiate a flash loan.
     * @param receiver The receiver of the tokens in the loan, and the receiver of the callback.
     * @param token The loan currency.
     * @param amount The amount of tokens lent.
     * @param data Arbitrary data structure, intended to contain user-defined parameters.
     */
    function flashLoan(
        IERC3156FlashBorrower receiver,
        address token,
        uint256 amount,
        bytes calldata data
    ) external returns (bool);
}
// Dependency file: contracts/interfaces/IERC3156FlashLender.sol
// pragma solidity >=0.6.0 <=0.8.0;
// import "contracts/interfaces/IERC3156FlashBorrower.sol";
function flashFee(
    address token,
    uint256 amount
) external view returns (uint256);

/**
 * @dev The fee to be charged for a given loan.
 * @param token The loan currency.
 * @param amount The amount of tokens lent.
 * @return The amount of `token` to be charged for the loan, on top of the returned principal.
 */