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June 1, 2022 10:44
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// SPDX-License-Identifier: MIT | |
// author: yoyoismee.eth -- it's opensource but also feel free to send me coffee/beer. | |
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pragma solidity 0.8.14; | |
import "@openzeppelin/contracts/security/ReentrancyGuard.sol"; | |
import "@openzeppelin/contracts/token/ERC20/IERC20.sol"; | |
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol"; | |
interface IFlashLoanReceiver { | |
function executeOperation(address _reserve, uint256 _amount, uint256 _fee, bytes calldata _params) external; | |
} | |
// flash kub protocol | |
contract FlashKub is ReentrancyGuard{ | |
using SafeERC20 for IERC20; | |
IERC20 constant KUSDT = IERC20(0x7d984C24d2499D840eB3b7016077164e15E5faA6); | |
mapping(address => uint256) share; | |
uint feeBips = 9; // 0.09 % fees | |
uint256 totalShare; | |
function deposit(uint amount) external nonReentrant{ | |
uint initialBal = KUSDT.balanceOf(address(this)); | |
if (totalShare == 0){ | |
totalShare = amount; | |
share[msg.sender] += amount; | |
}else{ | |
uint newShare = amount * initialBal / totalShare; | |
totalShare += newShare; | |
share[msg.sender] += newShare; | |
} | |
KUSDT.safeTransferFrom(msg.sender,address(this), amount); | |
} | |
function flashloan(address _receiver, address _reserve, uint256 _amount, bytes memory _params) external{ | |
_flashLoan(_receiver,_reserve,_amount,_params); | |
} | |
function flashloan(address _receiver, uint _amount, bytes memory _params) external{ | |
_flashLoan(_receiver,address(KUSDT),_amount,_params); | |
} | |
function flashloan( uint _amount, bytes memory _params) external{ | |
_flashLoan(msg.sender,address(KUSDT),_amount,_params); | |
} | |
function withdraw(uint amount) external nonReentrant{ | |
require(amount <= share[msg.sender]); | |
uint initialBal = KUSDT.balanceOf(address(this)); | |
uint toSend = amount * initialBal / totalShare; | |
totalShare -= amount; | |
share[msg.sender] -= amount; | |
KUSDT.safeTransfer(msg.sender, toSend); | |
} | |
function _flashLoan(address _receiver, address _reserve, uint256 _amount, bytes memory _params) | |
public | |
nonReentrant | |
{ | |
uint256 availableLiquidityBefore = KUSDT.balanceOf(address(this)); | |
require( | |
availableLiquidityBefore >= _amount, | |
"There is not enough liquidity available to borrow" | |
); | |
//calculate amount fee | |
uint256 amountFee = _amount * feeBips / 10000; | |
//get the FlashLoanReceiver instance | |
IFlashLoanReceiver receiver = IFlashLoanReceiver(_receiver); | |
//transfer funds to the receiver | |
KUSDT.safeTransfer(_receiver, _amount); | |
//execute action of the receiver | |
receiver.executeOperation(address(KUSDT), _amount, amountFee, _params); | |
//check that the actual balance of the core contract includes the returned amount | |
uint256 availableLiquidityAfter = KUSDT.balanceOf(address(this)); | |
require( | |
availableLiquidityAfter == availableLiquidityBefore + amountFee, | |
"The actual balance of the protocol is inconsistent" | |
); | |
} | |
} |
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