// File: /Users/hoangquan/Desktop/Self/keyTango/rapid-unwind/contracts/RapidUnwind.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.7.0;
pragma experimental ABIEncoderV2;
import './interfaces/IERC20WithPermit.sol';
import './interfaces/ISwapRouter.sol';
import './interfaces/ISwapFactory.sol';
import './interfaces/IERC20Pair.sol';

import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
import '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
import '@openzeppelin/contracts/access/Ownable.sol';
import '@openzeppelin/contracts/utils/Pausable.sol';
import '@openzeppelin/contracts/utils/ReentrancyGuard.sol';

contract Constant {
	address public constant WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
	address public constant uniRouterV2 = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
	address public constant uniswapV2Factory = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f;
	address public constant sushiRouter = 0xd9e1cE17f2641f24aE83637ab66a2cca9C378B9F;
	address public constant sushiFactory = 0xC0AEe478e3658e2610c5F7A4A2E1777cE9e4f2Ac;
	uint256 public constant deadline = 0xf000000000000000000000000000000000000000000000000000000000000000;
}

contract RapidHelper {
	using SafeERC20 for IERC20;

	function permitApprove(
		address _token,
		address _owner,
		uint256 _deadlinePermit,
		uint8 v,
		bytes32 r,
		bytes32 s
	) internal returns (bool) {
		IERC20WithPermit(_token).permit(_owner, address(this), type(uint256).max, _deadlinePermit, v, r, s);
		return true;
	}
}

contract RapidUni is Constant, RapidHelper {
	using SafeERC20 for IERC20;

	function getPath(address _tokenIn, address _tokenOut) private view returns (address[] memory path) {
		address pair = ISwapFactory(uniswapV2Factory).getPair(_tokenIn, _tokenOut);
		if (pair == address(0)) {
			path = new address[](3);
			path[0] = _tokenIn;
			path[1] = WETH;
			path[2] = _tokenOut;
		} else {
			path = new address[](2);
			path[0] = _tokenIn;
			path[1] = _tokenOut;
		}
	}

	function _uniswapTokenForToken(
		address _tokenIn,
		address _tokenOut,
		uint256 amount,
		uint256 expectedAmount,
		uint256 _deadline
	) internal {
		ISwapRouter(uniRouterV2).swapExactTokensForTokens(amount, expectedAmount, getPath(_tokenIn, _tokenOut), address(this), _deadline);
	}

	function _uniswapETHForToken(
		address _tokenOut,
		uint256 expectedAmount,
		uint256 _deadline,
		uint256 _amount
	) internal {
		ISwapRouter(uniRouterV2).swapExactETHForTokens{ value: _amount }(expectedAmount, getPath(WETH, _tokenOut), address(this), _deadline); // amounts[0] = WETH, amounts[1] = DAI
	}

	function _removeUniLpETH(address _token, uint256 _lpAmount) private returns (uint256 amountToken, uint256 amountETH) {
		(amountToken, amountETH) = ISwapRouter(uniRouterV2).removeLiquidityETH(_token, _lpAmount, 0, 0, address(this), deadline);
	}

	function _removeUniLpTokens(
		address _tokenA,
		address _tokenB,
		uint256 _lpAmount
	) private returns (uint256 amount0, uint256 amount1) {
		(amount0, amount1) = ISwapRouter(uniRouterV2).removeLiquidity(_tokenA, _tokenB, _lpAmount, 0, 0, address(this), deadline);
	}

	function _rapidUni(
		address _tokenOut,
		address[] memory standardTokens,
		uint256[] memory standardTokensAmounts,
		uint256[] memory amountOutMin1,
		address[] memory eip712Tokens,
		uint256[] memory eip712TokensAmounts,
		uint256[] memory amountOutMin2,
		uint8[] memory v,
		bytes32[] memory r,
		bytes32[] memory s
	) internal returns (bool) {
		for (uint256 i = 0; i < standardTokens.length; i++) {
			if (IERC20(standardTokens[i]).allowance(address(this), uniRouterV2) == 0) {
				IERC20(standardTokens[i]).safeApprove(uniRouterV2, type(uint256).max);
			}
			IERC20(standardTokens[i]).safeTransferFrom(msg.sender, address(this), standardTokensAmounts[i]);
			_uniswapTokenForToken(standardTokens[i], _tokenOut, standardTokensAmounts[i], amountOutMin1[i], deadline);
		}
		for (uint256 i = 0; i < eip712Tokens.length; i++) {
			if (IERC20WithPermit(eip712Tokens[i]).allowance(msg.sender, address(this)) == 0) {
				permitApprove(eip712Tokens[i], msg.sender, deadline, v[i], r[i], s[i]);
			}
			IERC20WithPermit(eip712Tokens[i]).transferFrom(msg.sender, address(this), eip712TokensAmounts[i]);
			if (IERC20WithPermit(eip712Tokens[i]).allowance(address(this), uniRouterV2) == 0) {
				IERC20WithPermit(eip712Tokens[i]).approve(uniRouterV2, type(uint256).max);
			}
			_uniswapTokenForToken(eip712Tokens[i], _tokenOut, eip712TokensAmounts[i], amountOutMin2[i], deadline);
		}

		if (msg.value > 0) {
			_uniswapETHForToken(_tokenOut, 0, deadline, msg.value);
		}
		return true;
	}

	function _rapidUniLP(
		uint256 deadlinePermit,
		address _tokenOut,
		address[] memory lpTokens,
		uint256[] memory lpTokensAmount,
		uint8[] memory v,
		bytes32[] memory r,
		bytes32[] memory s
	) internal returns (bool) {
		for (uint256 i = 0; i < lpTokens.length; i++) {
			require(lpTokens[i] != address(0), 'Invalid-pool-address');
			require(lpTokensAmount[i] > 0, 'Invalid-amount');
			IERC20Pair pair = IERC20Pair(lpTokens[i]);
			address token0 = pair.token0();
			address token1 = pair.token1();
			if (IERC20(lpTokens[i]).allowance(msg.sender, address(this)) == 0) {
				permitApprove(lpTokens[i], msg.sender, deadlinePermit, v[i], r[i], s[i]);
			}
		
			IERC20(lpTokens[i]).safeTransferFrom(msg.sender, address(this), lpTokensAmount[i]);
			if (IERC20(lpTokens[i]).allowance(address(this), uniRouterV2) == 0) {
				IERC20(lpTokens[i]).safeApprove(uniRouterV2, type(uint256).max);
			}	
			if (token0 == WETH || token1 == WETH) {
				address _token = token0 == WETH ? token1 : token0;
				(uint256 amountToken, uint256 amountETH) = _removeUniLpETH(_token, lpTokensAmount[i]);
				_uniswapETHForToken(_tokenOut, 0, deadline, amountETH);
				if (IERC20(_token).allowance(address(this), uniRouterV2) == 0) {
					IERC20(_token).safeApprove(uniRouterV2, type(uint256).max);
				}
				_uniswapTokenForToken(_token, _tokenOut, amountToken, 0, deadline);
			} else {
				(uint256 amount0, uint256 amount1) = _removeUniLpTokens(token0, token1, lpTokensAmount[i]);
				if (token0 == _tokenOut) {
					if (IERC20(token1).allowance(address(this), uniRouterV2) == 0) {
						IERC20(token1).safeApprove(uniRouterV2, type(uint256).max);
					}
					_uniswapTokenForToken(token1, _tokenOut, amount1, 0, deadline);
				} else if (token1 == _tokenOut) {
					if (IERC20(token0).allowance(address(this), uniRouterV2) == 0) {
						IERC20(token0).safeApprove(uniRouterV2, type(uint256).max);
					}
					_uniswapTokenForToken(token0, _tokenOut, amount0, 0, deadline);
				} else {
					if (IERC20(token1).allowance(address(this), uniRouterV2) == 0) {
						IERC20(token1).safeApprove(uniRouterV2, type(uint256).max);
					}
					if (IERC20(token0).allowance(address(this), uniRouterV2) == 0) {
						IERC20(token0).safeApprove(uniRouterV2, type(uint256).max);
					}
					_uniswapTokenForToken(token0, _tokenOut, amount0, 0, deadline);
					_uniswapTokenForToken(token1, _tokenOut, amount1, 0, deadline);
				}
			}
		}
		return true;
	}
}

contract RapidSushi is Constant, RapidHelper {
	using SafeERC20 for IERC20;

	function getPathSushi(address _tokenIn, address _tokenOut) private view returns (address[] memory path) {
		address pair = ISwapFactory(sushiFactory).getPair(_tokenIn, _tokenOut);
		if (pair == address(0)) {
			path = new address[](3);
			path[0] = _tokenIn;
			path[1] = WETH;
			path[2] = _tokenOut;
		} else {
			path = new address[](2);
			path[0] = _tokenIn;
			path[1] = _tokenOut;
		}
	}

	function _sushiswapTokenForToken(
		address _tokenIn,
		address _tokenOut,
		uint256 amount,
		uint256 expectedAmount,
		uint256 _deadline
	) internal {
		ISwapRouter(sushiRouter).swapExactTokensForTokens(amount, expectedAmount, getPathSushi(_tokenIn, _tokenOut), address(this), _deadline);
	}

	function _sushiswapETHForToken(
		address _tokenOut,
		uint256 expectedAmount,
		uint256 _deadline,
		uint256 _amount
	) internal {
		ISwapRouter(sushiRouter).swapExactETHForTokens{ value: _amount }(expectedAmount, getPathSushi(WETH, _tokenOut), address(this), _deadline); // amounts[0] = WETH, amounts[1] = DAI
	}

	function _removeSushiLpETH(address _token, uint256 _lpAmount) private returns (uint256 amountToken, uint256 amountETH) {
		(amountToken, amountETH) = ISwapRouter(sushiRouter).removeLiquidityETH(_token, _lpAmount, 0, 0, address(this), deadline);
	}

	function _removeSushiLpTokens(
		address _tokenA,
		address _tokenB,
		uint256 _lpAmount
	) private returns (uint256 amount0, uint256 amount1) {
		(amount0, amount1) = ISwapRouter(sushiRouter).removeLiquidity(_tokenA, _tokenB, _lpAmount, 0, 0, address(this), deadline);
	}

	function _rapidSushi(
		address _tokenOut,
		address[] memory standardTokens,
		uint256[] memory standardTokensAmounts,
		uint256[] memory amountOutMin1,
		address[] memory eip712Tokens,
		uint256[] memory eip712TokensAmounts,
		uint256[] memory amountOutMin2,
		uint8[] memory v,
		bytes32[] memory r,
		bytes32[] memory s
	) internal returns (bool) {
		for (uint256 i = 0; i < standardTokens.length; i++) {
			if (IERC20(standardTokens[i]).allowance(address(this), sushiRouter) == 0) {
				IERC20(standardTokens[i]).safeApprove(sushiRouter, type(uint256).max);
			}
			IERC20(standardTokens[i]).safeTransferFrom(msg.sender, address(this), standardTokensAmounts[i]);
			_sushiswapTokenForToken(standardTokens[i], _tokenOut, standardTokensAmounts[i], amountOutMin1[i], deadline);
		}
		for (uint256 i = 0; i < eip712Tokens.length; i++) {
			if (IERC20WithPermit(eip712Tokens[i]).allowance(msg.sender, address(this)) == 0) {
				permitApprove(eip712Tokens[i], msg.sender, deadline, v[i], r[i], s[i]);
			}
			IERC20WithPermit(eip712Tokens[i]).transferFrom(msg.sender, address(this), eip712TokensAmounts[i]);
			if (IERC20WithPermit(eip712Tokens[i]).allowance(address(this), sushiRouter) == 0) {
				IERC20WithPermit(eip712Tokens[i]).approve(sushiRouter, type(uint256).max);
			}
			_sushiswapTokenForToken(eip712Tokens[i], _tokenOut, eip712TokensAmounts[i], amountOutMin2[i], deadline);
		}

		if (msg.value > 0) {
			_sushiswapETHForToken(_tokenOut, 0, deadline, msg.value);
		}
		return true;
	}

	function _rapidSushiLP(
		uint256 deadlinePermit,
		address _tokenOut,
		address[] memory lpTokens,
		uint256[] memory lpTokensAmount,
		uint8[] memory v,
		bytes32[] memory r,
		bytes32[] memory s
	) internal returns (bool) {
		for (uint256 i = 0; i < lpTokens.length; i++) {
			require(lpTokens[i] != address(0), 'Invalid-pool-address');
			require(lpTokensAmount[i] > 0, 'Invalid-amount');
			IERC20Pair pair = IERC20Pair(lpTokens[i]);
			address token0 = pair.token0();
			address token1 = pair.token1();
			if (IERC20(lpTokens[i]).allowance(msg.sender, address(this)) == 0) {
				permitApprove(lpTokens[i], msg.sender, deadlinePermit, v[i], r[i], s[i]);
			}

			IERC20(lpTokens[i]).safeTransferFrom(msg.sender, address(this), lpTokensAmount[i]);
			IERC20(lpTokens[i]).safeApprove(sushiRouter, lpTokensAmount[i]);

			if (token0 == WETH || token1 == WETH) {
				address _token = token0 == WETH ? token1 : token0;
				(uint256 amountToken, uint256 amountETH) = _removeSushiLpETH(_token, lpTokensAmount[i]);
				_sushiswapETHForToken(_tokenOut, 0, deadline, amountETH);
				if (IERC20(_token).allowance(address(this), sushiRouter) == 0) {
					IERC20(_token).safeApprove(sushiRouter, type(uint256).max);
				}
				_sushiswapTokenForToken(_token, _tokenOut, amountToken, 0, deadline);
			} else {
				(uint256 amount0, uint256 amount1) = _removeSushiLpTokens(token0, token1, lpTokensAmount[i]);
				if (token0 == _tokenOut) {
					if (IERC20(token1).allowance(address(this), sushiRouter) == 0) {
						IERC20(token1).safeApprove(sushiRouter, type(uint256).max);
					}
					_sushiswapTokenForToken(token1, _tokenOut, amount1, 0, deadline);
				} else if (token1 == _tokenOut) {
					if (IERC20(token0).allowance(address(this), sushiRouter) == 0) {
						IERC20(token0).safeApprove(sushiRouter, type(uint256).max);
					}
					_sushiswapTokenForToken(token0, _tokenOut, amount0, 0, deadline);
				} else {
					if (IERC20(token0).allowance(address(this), sushiRouter) == 0) {
						IERC20(token0).safeApprove(sushiRouter, type(uint256).max);
					}
					if (IERC20(token1).allowance(address(this), sushiRouter) == 0) {
						IERC20(token1).safeApprove(sushiRouter, type(uint256).max);
					}
					_sushiswapTokenForToken(token0, _tokenOut, amount0, 0, deadline);
					_sushiswapTokenForToken(token1, _tokenOut, amount1, 0, deadline);
				}
			}
		}
		return true;
	}
}

contract RapidUnwind is RapidUni, RapidSushi, Ownable, Pausable, ReentrancyGuard {
	using SafeMath for uint256;
	using SafeERC20 for IERC20;
	using Address for address payable;

	uint256 private fee;
	address private feeCollector;

	function changeFee(uint256 _fee) external onlyOwner() {
		fee = _fee;
	}

	function changeFeeCollector(address _feeCollector) external onlyOwner() {
		feeCollector = _feeCollector;
	}

	function pause() external onlyOwner() {
		_pause();
	}

	function unPause() external onlyOwner() {
		_unpause();
	}

	function rapidUnwindToken(
		bool flag,
		address _tokenOut,
		address[] memory standardTokens,
		uint256[] memory standardTokensAmounts,
		uint256[] memory amountOutMin1,
		address[] memory eip712Tokens,
		uint256[] memory eip712TokensAmounts,
		uint256[] memory amountOutMin2,
		uint8[] memory v,
		bytes32[] memory r,
		bytes32[] memory s
	) external payable whenNotPaused() nonReentrant() returns (bool) {
		require(standardTokens.length == standardTokensAmounts.length, 'Invalid-length');
		require(eip712Tokens.length == eip712TokensAmounts.length && eip712Tokens.length == v.length, 'Invalid-length');
		uint256 balanceTokenOutBefore = IERC20(_tokenOut).balanceOf(address(this));
		if (flag) {
			_rapidUni(_tokenOut, standardTokens, standardTokensAmounts, amountOutMin1, eip712Tokens, eip712TokensAmounts, amountOutMin2, v, r, s);
		} else {
			_rapidSushi(_tokenOut, standardTokens, standardTokensAmounts, amountOutMin1, eip712Tokens, eip712TokensAmounts, amountOutMin2, v, r, s);
		}
		uint256 rapidBalance = IERC20(_tokenOut).balanceOf(address(this)).sub(balanceTokenOutBefore);
		if (fee > 0 && feeCollector != address(0)) {
			uint256 feeBalance = rapidBalance.mul(fee).div(1000);
			rapidBalance = rapidBalance.sub(feeBalance);
		}

		IERC20(_tokenOut).safeTransfer(msg.sender, rapidBalance);
	}
	
	function rapidUnwindLpToken(
		bool flag,
		uint256 deadlinePermit,
		address _tokenOut,
		address[] memory lpTokens,
		uint256[] memory lpTokensAmount,
		uint8[] memory v,
		bytes32[] memory r,
		bytes32[] memory s
	) external whenNotPaused() nonReentrant() returns (bool) {
		uint256 balanceTokenOutBefore = IERC20(_tokenOut).balanceOf(address(this));
		if (flag) {
			_rapidUniLP(deadlinePermit, _tokenOut, lpTokens, lpTokensAmount, v, r, s);
		} else { 
			_rapidSushiLP(deadlinePermit, _tokenOut, lpTokens, lpTokensAmount, v, r, s);
		}
		uint256 rapidBalance = IERC20(_tokenOut).balanceOf(address(this)).sub(balanceTokenOutBefore);
		if (fee > 0 && feeCollector != address(0)) {
			uint256 feeBalance = rapidBalance.mul(fee).div(1000);
			rapidBalance = rapidBalance.sub(feeBalance);
		}
		IERC20(_tokenOut).safeTransfer(msg.sender, rapidBalance);
	}

	function adminWithDrawFee(address _token) external onlyOwner() {
		if (_token != address(0)) {
			uint256 amountWithDraw = IERC20(_token).balanceOf(address(this));
			IERC20(_token).safeTransfer(feeCollector, amountWithDraw);
		} else {
			payable(feeCollector).sendValue(address(this).balance);
		}
	}

	receive() external payable {}
}

// File: /Users/hoangquan/Desktop/Self/keyTango/rapid-unwind/contracts/interfaces/IERC20Pair.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface IERC20Pair {
	function token0() external pure returns (address);

	function token1() external pure returns (address);

	function balanceOf(address user) external view returns (uint256);

	function totalSupply() external view returns (uint256);

	function getReserves()
		external
		view
		returns (
			uint112 _reserve0,
			uint112 _reserve1,
			uint32 _blockTimestampLast
		);

	function permit(
		address owner,
		address spender,
		uint256 value,
		uint256 deadline,
		uint8 v,
		bytes32 r,
		bytes32 s
	) external;
}

// File: /Users/hoangquan/Desktop/Self/keyTango/rapid-unwind/contracts/interfaces/IERC20WithPermit.sol



//SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.7.0;

interface IERC20WithPermit {
	function transferFrom(
		address from,
		address to,
		uint256 value
	) external returns (bool);

	function approve(address spender, uint256 value) external returns (bool);

	function allowance(address owner, address spender) external view returns (uint256);

	function permit(
		address owner,
		address spender,
		uint256 value,
		uint256 deadline,
		uint8 v,
		bytes32 r,
		bytes32 s
	) external;
}

// File: /Users/hoangquan/Desktop/Self/keyTango/rapid-unwind/contracts/interfaces/ISwapFactory.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface ISwapFactory {
	function getPair(address tokenA, address tokenB) external view returns (address);
}

// File: /Users/hoangquan/Desktop/Self/keyTango/rapid-unwind/contracts/interfaces/ISwapRouter.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.7.0;

interface ISwapRouter {
	function WETH() external pure returns (address);

	function swapExactETHForTokens(
		uint256 amountOutMin,
		address[] calldata path,
		address to,
		uint256 deadline
	) external payable returns (uint256[] memory amounts);

	function swapExactTokensForTokens(
		uint256 amountIn,
		uint256 amountOutMin,
		address[] calldata path,
		address to,
		uint256 deadline
	) external returns (uint256[] memory amounts);

	function removeLiquidity(
		address tokenA,
		address tokenB,
		uint256 liquidity,
		uint256 amountAMin,
		uint256 amountBMin,
		address to,
		uint256 deadline
	) external returns (uint256 amountA, uint256 amountB);

	function removeLiquidityETH(
		address token,
		uint256 liquidity,
		uint256 amountTokenMin,
		uint256 amountETHMin,
		address to,
		uint256 deadline
	) external returns (uint256 amountToken, uint256 amountETH);
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/Context.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/utils/Pausable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor () internal {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// File: @openzeppelin/contracts/utils/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}