//SPDX-License-Identifier: Unlicense
pragma solidity =0.7.6;

import '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
import '@openzeppelin/contracts/math/SafeMath.sol';
import '@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol';
import './interface/IUniswapV2Pair.sol';
import './interface/IUniswapV2Factory.sol';
import './interface/IUniswapV2Router.sol';

contract Staking is OwnableUpgradeable {
  using SafeMath for uint256;
  using SafeERC20 for IERC20;

  struct PoolInfo {
    IERC20 stakeToken;
    bool isNativePool;
    uint256 rewardPerBlock;
    uint256 lastRewardBlock;
    uint256 accTokenPerShare;
    uint256 depositedAmount;
    uint256 rewardsAmount;
    uint256 lockupDuration;
    uint256 depositLimit;
  }

  struct UserInfo {
    uint256 amount;
    uint256 rewardDebt;
    uint256 pendingRewards;
    uint256 lastClaim;
  }

  IUniswapV2Router02 public uniswapV2Router;
  IERC20 public rewardToken;
  address public devAddress;
  uint256 public nativeEarlyWithdrawlDevFee;
  uint256 public nativeEarlyWithdrawlLpFee;
  uint256 public nativeRegularWithdrawlDevFee;
  uint256 public nativeRegularWithdrawlLpFee;
  uint256 public lpEarlyWithdrawlFee;
  uint256 public lpRegularWithdrawlFee;
  uint256 public nonNativeDepositDevFee;
  uint256 public nonNativeDepositLpFee;
  uint256 public kawaLpPoolId;
  uint256 public xkawaLpPoolId;
  uint256 public freeTaxDuration;

  PoolInfo[] public pools;
  mapping(address => mapping(uint256 => UserInfo)) public userInfo;
  mapping(uint256 => address[]) private userList;

  event Deposit(address indexed user, uint256 indexed pid, uint256 amount);
  event Withdraw(address indexed user, uint256 indexed pid, uint256 amount);
  event Claim(address indexed user, uint256 indexed pid, uint256 amount);

  function initialize() public initializer {
    uniswapV2Router = IUniswapV2Router02(
      0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D
    );
    devAddress = address(0x93837577c98E01CFde883c23F64a0f608A70B90F);
    nativeEarlyWithdrawlDevFee = 3;
    nativeEarlyWithdrawlLpFee = 2;
    nativeRegularWithdrawlDevFee = 2;
    nativeRegularWithdrawlLpFee = 1;
    lpEarlyWithdrawlFee = 3;
    lpRegularWithdrawlFee = 1;
    nonNativeDepositDevFee = 3;
    nonNativeDepositLpFee = 1;
    kawaLpPoolId = 2;
    xkawaLpPoolId = 3;
    freeTaxDuration = 180 * 24 * 60 * 60 * 1000; // 180 days

    __Ownable_init();
  }

  receive() external payable {}

  /////////////// Owner functions ////////////////

  function updateUniswapV2Router(address newAddress) external onlyOwner {
    require(
      newAddress != address(uniswapV2Router),
      'The router already has that address'
    );
    uniswapV2Router = IUniswapV2Router02(newAddress);
  }

  function setRewardToken(address _rewardToken) external onlyOwner {
    rewardToken = IERC20(_rewardToken);
  }

  function setDevAddress(address _devAddress) external onlyOwner {
    devAddress = _devAddress;
  }

  function setNativeEarlyWithdrawlDevFee(uint256 _fee) external onlyOwner {
    nativeEarlyWithdrawlDevFee = _fee;
  }

  function setNativeEarlyWithdrawlLpFee(uint256 _fee) external onlyOwner {
    nativeEarlyWithdrawlLpFee = _fee;
  }

  function setNativeRegularWithdrawlDevFee(uint256 _fee) external onlyOwner {
    nativeRegularWithdrawlDevFee = _fee;
  }

  function setNativeRegularWithdrawlLpFee(uint256 _fee) external onlyOwner {
    nativeRegularWithdrawlLpFee = _fee;
  }

  function setLpEarlyWithdrawlFee(uint256 _fee) external onlyOwner {
    lpEarlyWithdrawlFee = _fee;
  }

  function setLpRegularWithdrawlFee(uint256 _fee) external onlyOwner {
    lpRegularWithdrawlFee = _fee;
  }

  function setNonNativeDepositDevFee(uint256 _fee) external onlyOwner {
    nonNativeDepositDevFee = _fee;
  }

  function setNonNativeDepositLpFee(uint256 _fee) external onlyOwner {
    nonNativeDepositLpFee = _fee;
  }

  function setKawaLpPoolId(uint256 pid) external onlyOwner {
    kawaLpPoolId = pid;
  }

  function setXkawaLpPoolId(uint256 pid) external onlyOwner {
    xkawaLpPoolId = pid;
  }

  function setFreeTaxDuration(uint256 _duration) external onlyOwner {
    freeTaxDuration = _duration;
  }

  function addPool(
    address _stakeToken,
    bool _isNativePool,
    uint256 _rewardPerBlock,
    uint256 _lockupDuration,
    uint256 _depositLimit
  ) external onlyOwner {
    pools.push(
      PoolInfo({
        stakeToken: IERC20(_stakeToken),
        isNativePool: _isNativePool,
        rewardPerBlock: _rewardPerBlock,
        lastRewardBlock: block.number,
        accTokenPerShare: 0,
        depositedAmount: 0,
        rewardsAmount: 0,
        lockupDuration: _lockupDuration,
        depositLimit: _depositLimit
      })
    );
  }

  function updatePool(
    uint256 pid,
    address _stakeToken,
    bool _isNativePool,
    uint256 _rewardPerBlock,
    uint256 _lockupDuration,
    uint256 _depositLimit
  ) external onlyOwner {
    require(pid >= 0 && pid < pools.length, 'invalid pool id');
    PoolInfo storage pool = pools[pid];
    pool.stakeToken = IERC20(_stakeToken);
    pool.isNativePool = _isNativePool;
    pool.rewardPerBlock = _rewardPerBlock;
    pool.lockupDuration = _lockupDuration;
    pool.depositLimit = _depositLimit;
  }

  function emergencyWithdraw(address _token, uint256 _amount)
    external
    onlyOwner
  {
    uint256 _bal = IERC20(_token).balanceOf(address(this));
    if (_amount > _bal) _amount = _bal;

    IERC20(_token).safeTransfer(_msgSender(), _amount);
  }

  /////////////// Main functions ////////////////

  function deposit(uint256 pid, uint256 amount) external {
    require(amount > 0, 'invalid deposit amount');

    PoolInfo storage pool = pools[pid];
    UserInfo storage user = userInfo[msg.sender][pid];

    uint256 depositAmount = amount;
    uint256 totalFeePercent = nonNativeDepositDevFee
      .add(nonNativeDepositLpFee)
      .add(nonNativeDepositLpFee);
    uint256 feeAmount = amount.mul(totalFeePercent).div(100);

    if (!pool.isNativePool && !isTaxFree(pid, msg.sender)) {
      depositAmount = amount.sub(feeAmount);
    }

    require(
      user.amount.add(depositAmount) <= pool.depositLimit,
      'exceeds deposit limit'
    );

    updatePool(pid);

    if (user.amount > 0) {
      uint256 pending = user.amount.mul(pool.accTokenPerShare).div(1e12).sub(
        user.rewardDebt
      );
      if (pending > 0) {
        user.pendingRewards = user.pendingRewards.add(pending);
      }
    } else {
      userList[pid].push(msg.sender);
    }

    if (depositAmount > 0) {
      pool.stakeToken.safeTransferFrom(
        address(msg.sender),
        address(this),
        amount
      );
      user.amount = user.amount.add(depositAmount);
      pool.depositedAmount = pool.depositedAmount.add(depositAmount);
    }
    user.rewardDebt = user.amount.mul(pool.accTokenPerShare).div(1e12);
    user.lastClaim = block.timestamp;
    emit Deposit(msg.sender, pid, amount);

    // swap and distribute here
    if (!pool.isNativePool && feeAmount > 0) {
      swapTokensForEth(pool.stakeToken, feeAmount);
      uint256 amountETH = address(this).balance;
      uint256 lpETH = amountETH.mul(nonNativeDepositLpFee).div(totalFeePercent);
      uint256 devETH = amountETH.sub(lpETH).sub(lpETH);
      sendEthToAddress(devAddress, devETH);
      distributeETHToLpStakers(kawaLpPoolId, lpETH);
      distributeETHToLpStakers(xkawaLpPoolId, lpETH);
    }
  }

  function withdraw(uint256 pid, uint256 amount) public {
    PoolInfo storage pool = pools[pid];
    UserInfo storage user = userInfo[msg.sender][pid];

    require(user.amount >= amount, 'Withdrawing more than you have!');

    bool isRegularWithdrawl = (block.timestamp >
      user.lastClaim + pool.lockupDuration);

    updatePool(pid);

    uint256 pending = user.amount.mul(pool.accTokenPerShare).div(1e12).sub(
      user.rewardDebt
    );
    if (pending > 0) {
      user.pendingRewards = user.pendingRewards.add(pending);
    }

    uint256 lpFee = 0;
    uint256 devFee = 0;
    if (pool.isNativePool && !isTaxFree(pid, msg.sender)) {
      if (pid == kawaLpPoolId || pid == xkawaLpPoolId) {
        if (isRegularWithdrawl) {
          devFee = amount.mul(lpRegularWithdrawlFee).div(100);
        } else {
          devFee = amount.mul(lpEarlyWithdrawlFee).div(100);
        }
      } else if (isRegularWithdrawl) {
        lpFee = amount.mul(nativeRegularWithdrawlLpFee).div(100);
        devFee = amount.mul(nativeRegularWithdrawlDevFee).div(100);
      } else {
        lpFee = amount.mul(nativeEarlyWithdrawlLpFee).div(100);
        devFee = amount.mul(nativeEarlyWithdrawlDevFee).div(100);
      }
    }
    uint256 withdrawAmount = amount.sub(lpFee).sub(lpFee).sub(devFee);

    if (amount > 0) {
      pool.stakeToken.safeTransfer(address(msg.sender), withdrawAmount);
      user.amount = user.amount.sub(amount);
      pool.depositedAmount = pool.depositedAmount.sub(amount);
    }

    if (user.amount == 0) {
      removeFromUserList(pid, msg.sender);
    }

    user.rewardDebt = user.amount.mul(pool.accTokenPerShare).div(1e12);
    user.lastClaim = block.timestamp;
    emit Withdraw(msg.sender, pid, amount);

    // swap and distribute here
    if (pool.isNativePool && !isTaxFree(pid, msg.sender)) {
      if (pid == kawaLpPoolId || pid == xkawaLpPoolId) {
        if (devFee > 0) {
          distributeTokensToStakers(pid, devFee);
        }
      } else if (isRegularWithdrawl) {
        if (devFee > 0) {
          distributeTokensToStakers(pid, devFee);
        }
        if (lpFee > 0) {
          swapTokensForEth(pool.stakeToken, lpFee.add(lpFee));
          uint256 amountETH = address(this).balance;
          uint256 lpETH = amountETH.div(2);
          distributeETHToLpStakers(kawaLpPoolId, lpETH);
          distributeETHToLpStakers(xkawaLpPoolId, lpETH);
        }
      } else {
        uint256 feeAmount = devFee.add(lpFee).add(lpFee);
        uint256 totalFeePercent = nativeRegularWithdrawlDevFee
          .add(nativeRegularWithdrawlLpFee)
          .add(nativeRegularWithdrawlLpFee);
        if (feeAmount > 0) {
          swapTokensForEth(pool.stakeToken, feeAmount);
          uint256 amountETH = address(this).balance;
          uint256 lpETH = amountETH.mul(nativeRegularWithdrawlLpFee).div(
            totalFeePercent
          );
          uint256 devETH = amountETH.sub(lpETH).sub(lpETH);
          if (devETH > 0) {
            sendEthToAddress(devAddress, devETH);
          }
          if (lpETH > 0) {
            distributeETHToLpStakers(kawaLpPoolId, lpETH);
            distributeETHToLpStakers(xkawaLpPoolId, lpETH);
          }
        }
      }
    }
  }

  function withdrawAll(uint256 pid) external {
    UserInfo storage user = userInfo[msg.sender][pid];

    withdraw(pid, user.amount);
  }

  function claim(uint256 pid) public {
    PoolInfo storage pool = pools[pid];
    UserInfo storage user = userInfo[msg.sender][pid];

    updatePool(pid);

    uint256 pending = user.amount.mul(pool.accTokenPerShare).div(1e12).sub(
      user.rewardDebt
    );
    if (pending > 0 || user.pendingRewards > 0) {
      user.pendingRewards = user.pendingRewards.add(pending);
      uint256 claimedAmount = safeRewardTokenTransfer(
        pid,
        msg.sender,
        user.pendingRewards
      );
      emit Claim(msg.sender, pid, claimedAmount);
      user.pendingRewards = user.pendingRewards.sub(claimedAmount);
      pool.rewardsAmount = pool.rewardsAmount.sub(claimedAmount);
    }
    user.rewardDebt = user.amount.mul(pool.accTokenPerShare).div(1e12);
  }

  /////////////// Internal functions ////////////////

  function updatePool(uint256 pid) internal {
    PoolInfo storage pool = pools[pid];

    if (block.number <= pool.lastRewardBlock) {
      return;
    }
    uint256 depositedAmount = pool.depositedAmount;
    if (pool.depositedAmount == 0) {
      pool.lastRewardBlock = block.number;
      return;
    }
    uint256 multiplier = block.number.sub(pool.lastRewardBlock);
    uint256 tokenReward = multiplier.mul(pool.rewardPerBlock);
    pool.rewardsAmount = pool.rewardsAmount.add(tokenReward);
    pool.accTokenPerShare = pool.accTokenPerShare.add(
      tokenReward.mul(1e12).div(depositedAmount)
    );
    pool.lastRewardBlock = block.number;
  }

  function safeRewardTokenTransfer(
    uint256 pid,
    address to,
    uint256 amount
  ) internal returns (uint256) {
    PoolInfo storage pool = pools[pid];
    uint256 _bal = rewardToken.balanceOf(address(this));
    if (amount > pool.rewardsAmount) amount = pool.rewardsAmount;
    if (amount > _bal) amount = _bal;
    rewardToken.safeTransfer(to, amount);
    return amount;
  }

  function removeFromUserList(uint256 pid, address _addr) internal {
    for (uint256 i = 0; i < userList[pid].length; i++) {
      if (userList[pid][i] == _addr) {
        userList[pid][i] = userList[pid][userList[pid].length - 1];
        userList[pid].pop();
        return;
      }
    }
  }

  function swapTokensForEth(IERC20 token, uint256 tokenAmount) private {
    // generate the uniswap pair path of token -> weth
    address[] memory path = new address[](2);
    path[0] = address(token);
    path[1] = uniswapV2Router.WETH();

    token.safeApprove(address(uniswapV2Router), tokenAmount);

    // make the swap
    uniswapV2Router.swapExactTokensForETH(
      tokenAmount,
      0, // accept any amount of ETH
      path,
      address(this),
      block.timestamp
    );
  }

  function distributeTokensToStakers(uint256 pid, uint256 tokenAmount) private {
    PoolInfo storage pool = pools[pid];
    for (uint256 i = 0; i < userList[pid].length; i++) {
      address userAddress = userList[pid][i];
      uint256 amount = tokenAmount.mul(userInfo[userAddress][pid].amount).div(
        pool.depositedAmount
      );
      userInfo[userAddress][pid].amount = userInfo[userAddress][pid].amount.add(
        amount
      );
      pool.depositedAmount = pool.depositedAmount.add(amount);
    }
  }

  function distributeETHToLpStakers(uint256 pid, uint256 amountETH) private {
    PoolInfo storage pool = pools[pid];
    for (uint256 i = 0; i < userList[pid].length; i++) {
      address userAddress = userList[pid][i];
      uint256 amount = amountETH.mul(userInfo[userAddress][pid].amount).div(
        pool.depositedAmount
      );
      sendEthToAddress(userAddress, amount);
    }
  }

  function sendEthToAddress(address _addr, uint256 amountETH) private {
    payable(_addr).call{value: amountETH}('');
  }

  function isTaxFree(uint256 pid, address _user) private view returns (bool) {
    UserInfo storage user = userInfo[_user][pid];
    if (user.amount > 0) {
      uint256 diff = block.timestamp.sub(user.lastClaim);
      if (diff > freeTaxDuration) {
        return true;
      }
    }
    return false;
  }

  /////////////// Get functions ////////////////

  function pendingRewards(uint256 pid, address _user)
    external
    view
    returns (uint256)
  {
    PoolInfo storage pool = pools[pid];
    UserInfo storage user = userInfo[_user][pid];
    uint256 accTokenPerShare = pool.accTokenPerShare;
    uint256 depositedAmount = pool.depositedAmount;
    if (block.number > pool.lastRewardBlock && depositedAmount != 0) {
      uint256 multiplier = block.number.sub(pool.lastRewardBlock);
      uint256 tokenReward = multiplier.mul(pool.rewardPerBlock);
      accTokenPerShare = accTokenPerShare.add(
        tokenReward.mul(1e12).div(depositedAmount)
      );
    }
    return
      user.amount.mul(accTokenPerShare).div(1e12).sub(user.rewardDebt).add(
        user.pendingRewards
      );
  }

  function getPoolCount() external view returns (uint256) {
    return pools.length;
  }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

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");
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/ContextUpgradeable.sol";
import "../proxy/Initializable.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 OwnableUpgradeable is Initializable, ContextUpgradeable {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function __Ownable_init() internal initializer {
        __Context_init_unchained();
        __Ownable_init_unchained();
    }

    function __Ownable_init_unchained() internal initializer {
        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;
    }
    uint256[49] private __gap;
}

interface IUniswapV2Pair {
  event Approval(address indexed owner, address indexed spender, uint256 value);
  event Transfer(address indexed from, address indexed to, uint256 value);

  function name() external pure returns (string memory);

  function symbol() external pure returns (string memory);

  function decimals() external pure returns (uint8);

  function totalSupply() external view returns (uint256);

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

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

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

  function transfer(address to, uint256 value) external returns (bool);

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

  function DOMAIN_SEPARATOR() external view returns (bytes32);

  function PERMIT_TYPEHASH() external pure returns (bytes32);

  function nonces(address owner) external view returns (uint256);

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

  event Mint(address indexed sender, uint256 amount0, uint256 amount1);
  event Burn(
    address indexed sender,
    uint256 amount0,
    uint256 amount1,
    address indexed to
  );
  event Swap(
    address indexed sender,
    uint256 amount0In,
    uint256 amount1In,
    uint256 amount0Out,
    uint256 amount1Out,
    address indexed to
  );
  event Sync(uint112 reserve0, uint112 reserve1);

  function MINIMUM_LIQUIDITY() external pure returns (uint256);

  function factory() external view returns (address);

  function token0() external view returns (address);

  function token1() external view returns (address);

  function getReserves()
    external
    view
    returns (
      uint112 reserve0,
      uint112 reserve1,
      uint32 blockTimestampLast
    );

  function price0CumulativeLast() external view returns (uint256);

  function price1CumulativeLast() external view returns (uint256);

  function kLast() external view returns (uint256);

  function mint(address to) external returns (uint256 liquidity);

  function burn(address to) external returns (uint256 amount0, uint256 amount1);

  function swap(
    uint256 amount0Out,
    uint256 amount1Out,
    address to,
    bytes calldata data
  ) external;

  function skim(address to) external;

  function sync() external;

  function initialize(address, address) external;
}

interface IUniswapV2Factory {
  event PairCreated(
    address indexed token0,
    address indexed token1,
    address pair,
    uint256
  );

  function feeTo() external view returns (address);

  function feeToSetter() external view returns (address);

  function getPair(address tokenA, address tokenB)
    external
    view
    returns (address pair);

  function allPairs(uint256) external view returns (address pair);

  function allPairsLength() external view returns (uint256);

  function createPair(address tokenA, address tokenB)
    external
    returns (address pair);

  function setFeeTo(address) external;

  function setFeeToSetter(address) external;
}

interface IUniswapV2Router01 {
  function factory() external pure returns (address);

  function WETH() external pure returns (address);

  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 addLiquidityETH(
    address token,
    uint256 amountTokenDesired,
    uint256 amountTokenMin,
    uint256 amountETHMin,
    address to,
    uint256 deadline
  )
    external
    payable
    returns (
      uint256 amountToken,
      uint256 amountETH,
      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 removeLiquidityETH(
    address token,
    uint256 liquidity,
    uint256 amountTokenMin,
    uint256 amountETHMin,
    address to,
    uint256 deadline
  ) external returns (uint256 amountToken, uint256 amountETH);

  function removeLiquidityWithPermit(
    address tokenA,
    address tokenB,
    uint256 liquidity,
    uint256 amountAMin,
    uint256 amountBMin,
    address to,
    uint256 deadline,
    bool approveMax,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) external returns (uint256 amountA, uint256 amountB);

  function removeLiquidityETHWithPermit(
    address token,
    uint256 liquidity,
    uint256 amountTokenMin,
    uint256 amountETHMin,
    address to,
    uint256 deadline,
    bool approveMax,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) external returns (uint256 amountToken, uint256 amountETH);

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

  function swapTokensForExactTokens(
    uint256 amountOut,
    uint256 amountInMax,
    address[] calldata path,
    address to,
    uint256 deadline
  ) external returns (uint256[] memory amounts);

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

  function swapTokensForExactETH(
    uint256 amountOut,
    uint256 amountInMax,
    address[] calldata path,
    address to,
    uint256 deadline
  ) external returns (uint256[] memory amounts);

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

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

  function quote(
    uint256 amountA,
    uint256 reserveA,
    uint256 reserveB
  ) external pure returns (uint256 amountB);

  function getAmountOut(
    uint256 amountIn,
    uint256 reserveIn,
    uint256 reserveOut
  ) external pure returns (uint256 amountOut);

  function getAmountIn(
    uint256 amountOut,
    uint256 reserveIn,
    uint256 reserveOut
  ) external pure returns (uint256 amountIn);

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

  function getAmountsIn(uint256 amountOut, address[] calldata path)
    external
    view
    returns (uint256[] memory amounts);
}

interface IUniswapV2Router02 is IUniswapV2Router01 {
  function removeLiquidityETHSupportingFeeOnTransferTokens(
    address token,
    uint256 liquidity,
    uint256 amountTokenMin,
    uint256 amountETHMin,
    address to,
    uint256 deadline
  ) external returns (uint256 amountETH);

  function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
    address token,
    uint256 liquidity,
    uint256 amountTokenMin,
    uint256 amountETHMin,
    address to,
    uint256 deadline,
    bool approveMax,
    uint8 v,
    bytes32 r,
    bytes32 s
  ) external returns (uint256 amountETH);

  function swapExactTokensForTokensSupportingFeeOnTransferTokens(
    uint256 amountIn,
    uint256 amountOutMin,
    address[] calldata path,
    address to,
    uint256 deadline
  ) external;

  function swapExactETHForTokensSupportingFeeOnTransferTokens(
    uint256 amountOutMin,
    address[] calldata path,
    address to,
    uint256 deadline
  ) external payable;

  function swapExactTokensForETHSupportingFeeOnTransferTokens(
    uint256 amountIn,
    uint256 amountOutMin,
    address[] calldata path,
    address to,
    uint256 deadline
  ) external;
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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);
            }
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;
import "../proxy/Initializable.sol";

/*
 * @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 ContextUpgradeable is Initializable {
    function __Context_init() internal initializer {
        __Context_init_unchained();
    }

    function __Context_init_unchained() internal initializer {
    }
    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;
    }
    uint256[50] private __gap;
}

// SPDX-License-Identifier: MIT

// solhint-disable-next-line compiler-version
pragma solidity >=0.4.24 <0.8.0;

import "../utils/AddressUpgradeable.sol";

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since a proxied contract can't have a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {UpgradeableProxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 */
abstract contract Initializable {

    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Modifier to protect an initializer function from being invoked twice.
     */
    modifier initializer() {
        require(_initializing || _isConstructor() || !_initialized, "Initializable: contract is already initialized");

        bool isTopLevelCall = !_initializing;
        if (isTopLevelCall) {
            _initializing = true;
            _initialized = true;
        }

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

    /// @dev Returns true if and only if the function is running in the constructor
    function _isConstructor() private view returns (bool) {
        return !AddressUpgradeable.isContract(address(this));
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library AddressUpgradeable {
    /**
     * @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);
    }

    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);
            }
        }
    }
}
{"success": true, "error": null, "results": {"detectors": [{"check": "reentrancy-no-eth", "impact": "Medium", "confidence": "Medium"}, {"check": "tautology", "impact": "Medium", "confidence": "High"}, {"check": "unchecked-lowlevel", "impact": "Medium", "confidence": "Medium"}, {"check": "reentrancy-eth", "impact": "High", "confidence": "Medium"}, {"check": "unused-return", "impact": "Medium", "confidence": "Medium"}]}}