Contract Diff Checker

Contract Name:
StratX2_PCS

Contract Source Code:

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "./StratX2.sol";

contract StratX2_PCS is StratX2 {
    constructor(
        address[] memory _addresses,
        uint256 _pid,
        bool _isCAKEStaking,
        bool _isSameAssetDeposit,
        bool _isAutoComp,
        address[] memory _earnedToAUTOPath,
        address[] memory _earnedToToken0Path,
        address[] memory _earnedToToken1Path,
        address[] memory _token0ToEarnedPath,
        address[] memory _token1ToEarnedPath,
        uint256 _controllerFee,
        uint256 _buyBackRate,
        uint256 _entranceFeeFactor,
        uint256 _withdrawFeeFactor
    ) public {
        wbnbAddress = _addresses[0];
        govAddress = _addresses[1];
        autoFarmAddress = _addresses[2];
        AUTOAddress = _addresses[3];

        wantAddress = _addresses[4];
        token0Address = _addresses[5];
        token1Address = _addresses[6];
        earnedAddress = _addresses[7];

        farmContractAddress = _addresses[8];
        pid = _pid;
        isCAKEStaking = _isCAKEStaking;
        isSameAssetDeposit = _isSameAssetDeposit;
        isAutoComp = _isAutoComp;

        uniRouterAddress = _addresses[9];
        earnedToAUTOPath = _earnedToAUTOPath;
        earnedToToken0Path = _earnedToToken0Path;
        earnedToToken1Path = _earnedToToken1Path;
        token0ToEarnedPath = _token0ToEarnedPath;
        token1ToEarnedPath = _token1ToEarnedPath;

        controllerFee = _controllerFee;
        rewardsAddress = _addresses[10];
        buyBackRate = _buyBackRate;
        buyBackAddress = _addresses[11];
        entranceFeeFactor = _entranceFeeFactor;
        withdrawFeeFactor = _withdrawFeeFactor;

        transferOwnership(autoFarmAddress);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "./helpers/ERC20.sol";

import "./libraries/Address.sol";

import "./libraries/SafeERC20.sol";

import "./libraries/EnumerableSet.sol";

import "./helpers/Ownable.sol";

import "./interfaces/IPancakeswapFarm.sol";

import "./interfaces/IPancakeRouter01.sol";

import "./interfaces/IPancakeRouter02.sol";

interface IWBNB is IERC20 {
    function deposit() external payable;

    function withdraw(uint256 wad) external;
}

import "./helpers/ReentrancyGuard.sol";

import "./helpers/Pausable.sol";

abstract contract StratX2 is Ownable, ReentrancyGuard, Pausable {
    // Maximises yields in pancakeswap

    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    bool public isCAKEStaking; // only for staking CAKE using pancakeswap's native CAKE staking contract.
    bool public isSameAssetDeposit;
    bool public isAutoComp; // this vault is purely for staking. eg. WBNB-AUTO staking vault.

    address public farmContractAddress; // address of farm, eg, PCS, Thugs etc.
    uint256 public pid; // pid of pool in farmContractAddress
    address public wantAddress;
    address public token0Address;
    address public token1Address;
    address public earnedAddress;
    address public uniRouterAddress; // uniswap, pancakeswap etc

    address public wbnbAddress;
    address public autoFarmAddress;
    address public AUTOAddress;
    address public govAddress; // timelock contract
    bool public onlyGov = true;

    uint256 public lastEarnBlock = 0;
    uint256 public wantLockedTotal = 0;
    uint256 public sharesTotal = 0;

    uint256 public controllerFee = 0; // 70;
    uint256 public constant controllerFeeMax = 10000; // 100 = 1%
    uint256 public constant controllerFeeUL = 300;

    uint256 public buyBackRate = 0; // 250;
    uint256 public constant buyBackRateMax = 10000; // 100 = 1%
    uint256 public constant buyBackRateUL = 800;
    address public buyBackAddress = 0x000000000000000000000000000000000000dEaD;
    address public rewardsAddress;

    uint256 public entranceFeeFactor = 9990; // < 0.1% entrance fee - goes to pool + prevents front-running
    uint256 public constant entranceFeeFactorMax = 10000;
    uint256 public constant entranceFeeFactorLL = 9950; // 0.5% is the max entrance fee settable. LL = lowerlimit

    uint256 public withdrawFeeFactor = 10000; // 0.1% withdraw fee - goes to pool
    uint256 public constant withdrawFeeFactorMax = 10000;
    uint256 public constant withdrawFeeFactorLL = 9950; // 0.5% is the max entrance fee settable. LL = lowerlimit

    uint256 public slippageFactor = 0; // 5% default slippage tolerance
    uint256 public constant slippageFactorUL = 995;

    address[] public earnedToAUTOPath;
    address[] public earnedToToken0Path;
    address[] public earnedToToken1Path;
    address[] public token0ToEarnedPath;
    address[] public token1ToEarnedPath;

    event SetSettings(
        uint256 _entranceFeeFactor,
        uint256 _withdrawFeeFactor,
        uint256 _controllerFee,
        uint256 _buyBackRate,
        uint256 _slippageFactor
    );

    event SetGov(address _govAddress);
    event SetOnlyGov(bool _onlyGov);
    event SetUniRouterAddress(address _uniRouterAddress);
    event SetBuyBackAddress(address _buyBackAddress);
    event SetRewardsAddress(address _rewardsAddress);

    modifier onlyAllowGov() {
        require(msg.sender == govAddress, "!gov");
        _;
    }

    // Receives new deposits from user
    function deposit(address _userAddress, uint256 _wantAmt)
        public
        virtual
        onlyOwner
        nonReentrant
        whenNotPaused
        returns (uint256)
    {
        IERC20(wantAddress).safeTransferFrom(
            address(msg.sender),
            address(this),
            _wantAmt
        );

        uint256 sharesAdded = _wantAmt;
        if (wantLockedTotal > 0 && sharesTotal > 0) {
            sharesAdded = _wantAmt
                .mul(sharesTotal)
                .mul(entranceFeeFactor)
                .div(wantLockedTotal)
                .div(entranceFeeFactorMax);
        }
        sharesTotal = sharesTotal.add(sharesAdded);

        if (isAutoComp) {
            _farm();
        } else {
            wantLockedTotal = wantLockedTotal.add(_wantAmt);
        }

        return sharesAdded;
    }

    function farm() public virtual nonReentrant whenNotPaused {
        _farm();
    }

    function _farm() internal virtual {
        require(isAutoComp, "!isAutoComp");
        uint256 wantAmt = IERC20(wantAddress).balanceOf(address(this));
        wantLockedTotal = wantLockedTotal.add(wantAmt);
        IERC20(wantAddress).safeIncreaseAllowance(farmContractAddress, wantAmt);

        if (isCAKEStaking) {
            IPancakeswapFarm(farmContractAddress).enterStaking(wantAmt); // Just for CAKE staking, we dont use deposit()
        } else {
            IPancakeswapFarm(farmContractAddress).deposit(pid, wantAmt);
        }
    }

    function _unfarm(uint256 _wantAmt) internal virtual {
        if (isCAKEStaking) {
            IPancakeswapFarm(farmContractAddress).leaveStaking(_wantAmt); // Just for CAKE staking, we dont use withdraw()
        } else {
            IPancakeswapFarm(farmContractAddress).withdraw(pid, _wantAmt);
        }
    }

    function withdraw(address _userAddress, uint256 _wantAmt)
        public
        virtual
        onlyOwner
        nonReentrant
        returns (uint256)
    {
        require(_wantAmt > 0, "_wantAmt <= 0");

        uint256 sharesRemoved = _wantAmt.mul(sharesTotal).div(wantLockedTotal);
        if (sharesRemoved > sharesTotal) {
            sharesRemoved = sharesTotal;
        }
        sharesTotal = sharesTotal.sub(sharesRemoved);

        if (withdrawFeeFactor < withdrawFeeFactorMax) {
            _wantAmt = _wantAmt.mul(withdrawFeeFactor).div(
                withdrawFeeFactorMax
            );
        }

        if (isAutoComp) {
            _unfarm(_wantAmt);
        }

        uint256 wantAmt = IERC20(wantAddress).balanceOf(address(this));
        if (_wantAmt > wantAmt) {
            _wantAmt = wantAmt;
        }

        if (wantLockedTotal < _wantAmt) {
            _wantAmt = wantLockedTotal;
        }

        wantLockedTotal = wantLockedTotal.sub(_wantAmt);

        IERC20(wantAddress).safeTransfer(autoFarmAddress, _wantAmt);

        return sharesRemoved;
    }

    // 1. Harvest farm tokens
    // 2. Converts farm tokens into want tokens
    // 3. Deposits want tokens

    function earn() public virtual nonReentrant whenNotPaused {
        require(isAutoComp, "!isAutoComp");
        if (onlyGov) {
            require(msg.sender == govAddress, "!gov");
        }

        // Harvest farm tokens
        _unfarm(0);

        if (earnedAddress == wbnbAddress) {
            _wrapBNB();
        }

        // Converts farm tokens into want tokens
        uint256 earnedAmt = IERC20(earnedAddress).balanceOf(address(this));

        earnedAmt = distributeFees(earnedAmt);
        earnedAmt = buyBack(earnedAmt);

        if (isCAKEStaking || isSameAssetDeposit) {
            lastEarnBlock = block.number;
            _farm();
            return;
        }

        IERC20(earnedAddress).safeApprove(uniRouterAddress, 0);
        IERC20(earnedAddress).safeIncreaseAllowance(
            uniRouterAddress,
            earnedAmt
        );

        if (earnedAddress != token0Address) {
            // Swap half earned to token0
            _safeSwap(
                uniRouterAddress,
                earnedAmt.div(2),
                slippageFactor,
                earnedToToken0Path,
                address(this),
                block.timestamp.add(600)
            );
        }

        if (earnedAddress != token1Address) {
            // Swap half earned to token1
            _safeSwap(
                uniRouterAddress,
                earnedAmt.div(2),
                slippageFactor,
                earnedToToken1Path,
                address(this),
                block.timestamp.add(600)
            );
        }

        // Get want tokens, ie. add liquidity
        uint256 token0Amt = IERC20(token0Address).balanceOf(address(this));
        uint256 token1Amt = IERC20(token1Address).balanceOf(address(this));
        if (token0Amt > 0 && token1Amt > 0) {
            IERC20(token0Address).safeIncreaseAllowance(
                uniRouterAddress,
                token0Amt
            );
            IERC20(token1Address).safeIncreaseAllowance(
                uniRouterAddress,
                token1Amt
            );
            IPancakeRouter02(uniRouterAddress).addLiquidity(
                token0Address,
                token1Address,
                token0Amt,
                token1Amt,
                0,
                0,
                address(this),
                block.timestamp.add(600)
            );
        }

        lastEarnBlock = block.number;

        _farm();
    }

    function buyBack(uint256 _earnedAmt) internal virtual returns (uint256) {
        if (buyBackRate <= 0) {
            return _earnedAmt;
        }

        uint256 buyBackAmt = _earnedAmt.mul(buyBackRate).div(buyBackRateMax);

        if (earnedAddress == AUTOAddress) {
            IERC20(earnedAddress).safeTransfer(buyBackAddress, buyBackAmt);
        } else {
            IERC20(earnedAddress).safeIncreaseAllowance(
                uniRouterAddress,
                buyBackAmt
            );

            _safeSwap(
                uniRouterAddress,
                buyBackAmt,
                slippageFactor,
                earnedToAUTOPath,
                buyBackAddress,
                block.timestamp.add(600)
            );
        }

        return _earnedAmt.sub(buyBackAmt);
    }

    function distributeFees(uint256 _earnedAmt)
        internal
        virtual
        returns (uint256)
    {
        if (_earnedAmt > 0) {
            // Performance fee
            if (controllerFee > 0) {
                uint256 fee =
                    _earnedAmt.mul(controllerFee).div(controllerFeeMax);
                IERC20(earnedAddress).safeTransfer(rewardsAddress, fee);
                _earnedAmt = _earnedAmt.sub(fee);
            }
        }

        return _earnedAmt;
    }

    function convertDustToEarned() public virtual whenNotPaused {
        require(isAutoComp, "!isAutoComp");
        require(!isCAKEStaking, "isCAKEStaking");

        // Converts dust tokens into earned tokens, which will be reinvested on the next earn().

        // Converts token0 dust (if any) to earned tokens
        uint256 token0Amt = IERC20(token0Address).balanceOf(address(this));
        if (token0Address != earnedAddress && token0Amt > 0) {
            IERC20(token0Address).safeIncreaseAllowance(
                uniRouterAddress,
                token0Amt
            );

            // Swap all dust tokens to earned tokens
            _safeSwap(
                uniRouterAddress,
                token0Amt,
                slippageFactor,
                token0ToEarnedPath,
                address(this),
                block.timestamp.add(600)
            );
        }

        // Converts token1 dust (if any) to earned tokens
        uint256 token1Amt = IERC20(token1Address).balanceOf(address(this));
        if (token1Address != earnedAddress && token1Amt > 0) {
            IERC20(token1Address).safeIncreaseAllowance(
                uniRouterAddress,
                token1Amt
            );

            // Swap all dust tokens to earned tokens
            _safeSwap(
                uniRouterAddress,
                token1Amt,
                slippageFactor,
                token1ToEarnedPath,
                address(this),
                block.timestamp.add(600)
            );
        }
    }

    function pause() public virtual onlyAllowGov {
        _pause();
    }

    function unpause() public virtual onlyAllowGov {
        _unpause();
    }

    function setSettings(
        uint256 _entranceFeeFactor,
        uint256 _withdrawFeeFactor,
        uint256 _controllerFee,
        uint256 _buyBackRate,
        uint256 _slippageFactor
    ) public virtual onlyAllowGov {
        require(
            _entranceFeeFactor >= entranceFeeFactorLL,
            "_entranceFeeFactor too low"
        );
        require(
            _entranceFeeFactor <= entranceFeeFactorMax,
            "_entranceFeeFactor too high"
        );
        entranceFeeFactor = _entranceFeeFactor;

        require(
            _withdrawFeeFactor >= withdrawFeeFactorLL,
            "_withdrawFeeFactor too low"
        );
        require(
            _withdrawFeeFactor <= withdrawFeeFactorMax,
            "_withdrawFeeFactor too high"
        );
        withdrawFeeFactor = _withdrawFeeFactor;

        require(_controllerFee <= controllerFeeUL, "_controllerFee too high");
        controllerFee = _controllerFee;

        require(_buyBackRate <= buyBackRateUL, "_buyBackRate too high");
        buyBackRate = _buyBackRate;

        require(
            _slippageFactor <= slippageFactorUL,
            "_slippageFactor too high"
        );
        slippageFactor = _slippageFactor;

        emit SetSettings(
            _entranceFeeFactor,
            _withdrawFeeFactor,
            _controllerFee,
            _buyBackRate,
            _slippageFactor
        );
    }

    function setGov(address _govAddress) public virtual onlyAllowGov {
        govAddress = _govAddress;
        emit SetGov(_govAddress);
    }

    function setOnlyGov(bool _onlyGov) public virtual onlyAllowGov {
        onlyGov = _onlyGov;
        emit SetOnlyGov(_onlyGov);
    }

    function setUniRouterAddress(address _uniRouterAddress)
        public
        virtual
        onlyAllowGov
    {
        uniRouterAddress = _uniRouterAddress;
        emit SetUniRouterAddress(_uniRouterAddress);
    }

    function setBuyBackAddress(address _buyBackAddress)
        public
        virtual
        onlyAllowGov
    {
        buyBackAddress = _buyBackAddress;
        emit SetBuyBackAddress(_buyBackAddress);
    }

    function setRewardsAddress(address _rewardsAddress)
        public
        virtual
        onlyAllowGov
    {
        rewardsAddress = _rewardsAddress;
        emit SetRewardsAddress(_rewardsAddress);
    }

    function inCaseTokensGetStuck(
        address _token,
        uint256 _amount,
        address _to
    ) public virtual onlyAllowGov {
        require(_token != earnedAddress, "!safe");
        require(_token != wantAddress, "!safe");
        IERC20(_token).safeTransfer(_to, _amount);
    }

    function _wrapBNB() internal virtual {
        // BNB -> WBNB
        uint256 bnbBal = address(this).balance;
        if (bnbBal > 0) {
            IWBNB(wbnbAddress).deposit{value: bnbBal}(); // BNB -> WBNB
        }
    }

    function wrapBNB() public virtual onlyAllowGov {
        _wrapBNB();
    }

    function _safeSwap(
        address _uniRouterAddress,
        uint256 _amountIn,
        uint256 _slippageFactor,
        address[] memory _path,
        address _to,
        uint256 _deadline
    ) internal virtual {
        uint256[] memory amounts =
            IPancakeRouter02(_uniRouterAddress).getAmountsOut(_amountIn, _path);
        uint256 amountOut = amounts[amounts.length.sub(1)];

        IPancakeRouter02(_uniRouterAddress)
            .swapExactTokensForTokensSupportingFeeOnTransferTokens(
            _amountIn,
            amountOut.mul(_slippageFactor).div(1000),
            _path,
            _to,
            _deadline
        );
    }
}

pragma solidity 0.6.12;

import "./Context.sol";
import "../libraries/SafeMath.sol";
import "../interfaces/IERC20.sol";

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol
contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender)
        public
        view
        virtual
        override
        returns (uint256)
    {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * Requirements:
     *
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(
            sender,
            _msgSender(),
            _allowances[sender][_msgSender()].sub(
                amount,
                "ERC20: transfer amount exceeds allowance"
            )
        );
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue)
        public
        virtual
        returns (bool)
    {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].add(addedValue)
        );
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue)
        public
        virtual
        returns (bool)
    {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].sub(
                subtractedValue,
                "ERC20: decreased allowance below zero"
            )
        );
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(
            amount,
            "ERC20: transfer amount exceeds balance"
        );
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(
            amount,
            "ERC20: burn amount exceeds balance"
        );
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

pragma solidity 0.6.12;

// import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol";
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 v3.3._
     */
    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 v3.3._
     */
    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);
            }
        }
    }
}

pragma solidity 0.6.12;

import "./SafeMath.sol";
import "./Address.sol";
import "../interfaces/IERC20.sol";

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol
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"
            );
        }
    }
}

pragma solidity 0.6.12;

// import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/EnumerableSet.sol";
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping(bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) {
            // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value)
        private
        view
        returns (bool)
    {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function _at(Set storage set, uint256 index)
        private
        view
        returns (bytes32)
    {
        require(
            set._values.length > index,
            "EnumerableSet: index out of bounds"
        );
        return set._values[index];
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value)
        internal
        returns (bool)
    {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value)
        internal
        returns (bool)
    {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value)
        internal
        view
        returns (bool)
    {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(Bytes32Set storage set, uint256 index)
        internal
        view
        returns (bytes32)
    {
        return _at(set._inner, index);
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value)
        internal
        returns (bool)
    {
        return _add(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value)
        internal
        returns (bool)
    {
        return _remove(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value)
        internal
        view
        returns (bool)
    {
        return _contains(set._inner, bytes32(uint256(value)));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(AddressSet storage set, uint256 index)
        internal
        view
        returns (address)
    {
        return address(uint256(_at(set._inner, index)));
    }

    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value)
        internal
        returns (bool)
    {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value)
        internal
        view
        returns (bool)
    {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(UintSet storage set, uint256 index)
        internal
        view
        returns (uint256)
    {
        return uint256(_at(set._inner, index));
    }
}

pragma solidity 0.6.12;

import "./Context.sol";

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol
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 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;
    }
}

pragma solidity 0.6.12;

interface IPancakeswapFarm {

    // Deposit LP tokens to MasterChef for CAKE allocation.
    function deposit(uint256 _pid, uint256 _amount) external;

    // Withdraw LP tokens from MasterChef.
    function withdraw(uint256 _pid, uint256 _amount) external;

    // Stake CAKE tokens to MasterChef
    function enterStaking(uint256 _amount) external;

    // Withdraw CAKE tokens from STAKING.
    function leaveStaking(uint256 _amount) external;

}

pragma solidity 0.6.12;

interface IPancakeRouter01 {
   
    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

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

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

    function getAmountsOut(uint256 amountIn, address[] calldata path)
        external
        view
        returns (uint256[] memory amounts);

}

pragma solidity 0.6.12;

import "./IPancakeRouter01.sol";

interface IPancakeRouter02 is IPancakeRouter01 {
    
    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external;

}

pragma solidity 0.6.12;

// "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/ReentrancyGuard.sol";
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;
    }
}

pragma solidity 0.6.12;

import "./Context.sol";

// "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Pausable.sol";
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 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());
    }
}

pragma solidity 0.6.12;

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Context.sol
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;
    }
}

pragma solidity ^0.6.12;

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/SafeMath.sol
library SafeMath {
    /**
     * @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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * 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);
        uint256 c = a - b;

        return c;
    }

    /**
     * @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) {
        // 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 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts 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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message 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,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts 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) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

pragma solidity ^0.6.12;

// import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/IERC20.sol";
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
    );
}

Please enter a contract address above to load the contract details and source code.

Context size (optional):