└── Flashloan.sol


/Flashloan.sol:
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  1 | pragma solidity >=0.6.6 <0.8.0;
  2 | 
  3 | // SPDX-License-Identifier: Unlicensed
  4 | 
  5 | import "@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol";
  6 | import "@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol";
  7 | import "@uniswap/v2-periphery/contracts/interfaces/IERC20.sol";
  8 | import "@uniswap/v2-periphery/contracts/libraries/UniswapV2Library.sol";
  9 | import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol";
 10 | 
 11 | contract FlashLoan {
 12 |     using SafeMath for uint256;
 13 |     
 14 |     address private immutable _owner;
 15 |     address public  immutable _wbnbAddress;
 16 |     
 17 |     uint private _deadline = 3 minutes;
 18 |     
 19 |     IUniswapV2Router02 public _currentTargetRouter;
 20 |     
 21 |     IUniswapV2Router02 public _pcsRouter;
 22 |     IUniswapV2Factory  public _pcsFactory;
 23 |     
 24 |     /**
 25 |      * Construct the contract.
 26 |      */
 27 |     constructor(address pcsRouterAddress, address targetRouterAddress) public {
 28 |         _owner = msg.sender;
 29 |         
 30 |         _currentTargetRouter = IUniswapV2Router02(targetRouterAddress);
 31 |         _pcsRouter           = IUniswapV2Router02(pcsRouterAddress);
 32 |         
 33 |         _wbnbAddress         = _pcsRouter.WETH();
 34 |         _pcsFactory          = IUniswapV2Factory(_pcsRouter.factory());
 35 |     } 
 36 |     
 37 |     /**
 38 |      * Set target router to swap tokens.
 39 |      */
 40 |     function setTargetRouter(address routerAddress) public {
 41 |         require(msg.sender == _owner);
 42 |         _currentTargetRouter = IUniswapV2Router02(routerAddress);
 43 |     }
 44 |     
 45 |     /**
 46 |      * Borrow token from PancakeSwap.
 47 |      */
 48 |     function borrow(address token0, address token1, uint256 amount0, uint256 amount1) external {
 49 |         address pairAddress = _pcsFactory.getPair(token0, token1);
 50 |         require(pairAddress != address(0), "Pair does not exist.");
 51 |         
 52 |         IUniswapV2Pair pair = IUniswapV2Pair(pairAddress);
 53 |         
 54 |         (uint112 reserve0, uint112 reserve1,) = pair.getReserves();
 55 |         require(reserve0 != 0 && reserve1 != 0, "Liquidity does not exist for that pair.");
 56 |         
 57 |         pair.swap(amount0, amount1, address(this), bytes("not empty"));
 58 |     }
 59 |     
 60 |     /**
 61 |      * This function gets triggered by PancakeSwap itself after borrow.
 62 |      */
 63 |     function pancakeCall(address _sender, uint _amount0, uint _amount1, bytes calldata _data) external {
 64 |         address[] memory path = new address[](2);
 65 |         uint amountToken = _amount0 == 0 ? _amount1 : _amount0;
 66 |         
 67 |         address token0 = IUniswapV2Pair(msg.sender).token0();
 68 |         address token1 = IUniswapV2Pair(msg.sender).token1();
 69 |         
 70 |         require(msg.sender == UniswapV2Library.pairFor(address(_pcsFactory), token0, token1));
 71 |         require(_amount0 == 0 || _amount1 == 0);
 72 |         
 73 |         // if _amount0 is zero sell token1 for token0
 74 |         // else sell token0 for token1 as a result
 75 |         path[0] = _amount0 == 0 ? token1 : token0;
 76 |         path[1] = _amount0 == 0 ? token0 : token1;
 77 |         
 78 |         // IERC20 token that we will sell for otherToken
 79 |         IERC20 token = IERC20(_amount0 == 0 ? token1 : token0);
 80 |         token.approve(address(_currentTargetRouter), amountToken);
 81 | 
 82 |         // calculate the amount of token how much input token should be reimbursed
 83 |         uint amountRequired = UniswapV2Library.getAmountsIn(
 84 |             address(_pcsFactory),
 85 |             amountToken,
 86 |             path
 87 |         )[0];
 88 | 
 89 |         // swap token and obtain equivalent otherToken amountRequired as a result
 90 |         uint amountReceived = _currentTargetRouter.swapExactTokensForTokens(
 91 |             amountToken,
 92 |             amountRequired,
 93 |             path,
 94 |             msg.sender,
 95 |             _deadline
 96 |         )[1];
 97 |     
 98 |         // fail if we didn't get enough tokens
 99 |         if (amountReceived > amountRequired) {
100 |             token.transfer(msg.sender, amountToken);
101 |             require(amountReceived > amountRequired, "Router didn't give enough tokens.");
102 |         }
103 |         
104 |         IERC20 otherToken = IERC20(_amount0 == 0 ? token0 : token1);
105 |         otherToken.transfer(msg.sender, amountRequired);
106 |         otherToken.transfer(_owner, amountReceived.sub(amountRequired));
107 |     }
108 | }
109 | 


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