// File: contracts/vaults/AladdinCRV.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

import "@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/token/ERC20/SafeERC20Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/utils/ReentrancyGuardUpgradeable.sol";

import "../interfaces/IAladdinCRV.sol";
import "../interfaces/IConvexBasicRewards.sol";
import "../interfaces/IConvexCRVDepositor.sol";
import "../interfaces/IConvexVirtualBalanceRewardPool.sol";
import "../interfaces/ICVXMining.sol";
import "../interfaces/IEllipsisMerkleDistributor.sol";

// solhint-disable no-empty-blocks, reason-string
contract AladdinCRV is ERC20Upgradeable, OwnableUpgradeable, ReentrancyGuardUpgradeable, IAladdinCRV {
  using SafeMathUpgradeable for uint256;
  using SafeERC20Upgradeable for IERC20Upgradeable;

  uint256 private constant FEE_DENOMINATOR = 1e9;
  uint256 private constant MAX_WITHDRAW_FEE = 1e8; // 10%
  uint256 private constant MAX_PLATFORM_FEE = 2e8; // 20%
  uint256 private constant MAX_HARVEST_BOUNTY = 1e8; // 10%

  // The address of cvxCRV token.
  address private constant CVXCRV = 0x62B9c7356A2Dc64a1969e19C23e4f579F9810Aa7;
  // The address of CRV token.
  address private constant CRV = 0xD533a949740bb3306d119CC777fa900bA034cd52;
  // The address of CVX token.
  address private constant CVX = 0x4e3FBD56CD56c3e72c1403e103b45Db9da5B9D2B;
  // The address of 3CRV token.
  address private constant THREE_CRV = 0x6c3F90f043a72FA612cbac8115EE7e52BDe6E490;
  // The address of Convex cvxCRV Staking Contract.
  address private constant CVXCRV_STAKING = 0x3Fe65692bfCD0e6CF84cB1E7d24108E434A7587e;
  // The address of Convex CVX Mining Contract.
  address private constant CVX_MINING = 0x3c75BFe6FbfDa3A94E7E7E8c2216AFc684dE5343;
  // The address of Convex 3CRV Rewards Contract.
  address private constant THREE_CRV_REWARDS = 0x7091dbb7fcbA54569eF1387Ac89Eb2a5C9F6d2EA;

  /// @dev The address of ZAP contract, will be used to swap tokens.
  address public zap;

  /// @dev The percentage of token to take on withdraw
  uint256 public withdrawFeePercentage;
  /// @dev The percentage of rewards to take for platform on harvest
  uint256 public platformFeePercentage;
  /// @dev The percentage of rewards to take for caller on harvest
  uint256 public harvestBountyPercentage;
  /// @dev The address of recipient of platform fee
  address public platform;

  function initialize(
    address _zap,
    address _platform,
    uint256 _withdrawFeePercentage,
    uint256 _platformFeePercentage,
    uint256 _harvestBountyPercentage
  ) external initializer {
    ERC20Upgradeable.__ERC20_init("Aladdin cvxCRV", "aCRV");
    OwnableUpgradeable.__Ownable_init();
    ReentrancyGuardUpgradeable.__ReentrancyGuard_init();

    require(_zap != address(0), "AladdinCRV: zero zap address");
    require(_platform != address(0), "AladdinCRV: zero platform address");
    require(_withdrawFeePercentage <= MAX_WITHDRAW_FEE, "AladdinCRV: fee too large");
    require(_platformFeePercentage <= MAX_PLATFORM_FEE, "AladdinCRV: fee too large");
    require(_harvestBountyPercentage <= MAX_HARVEST_BOUNTY, "AladdinCRV: fee too large");

    zap = _zap;
    platform = _platform;
    withdrawFeePercentage = _withdrawFeePercentage;
    platformFeePercentage = _platformFeePercentage;
    harvestBountyPercentage = _harvestBountyPercentage;
  }

  /********************************** View Functions **********************************/

  /// @dev Return the total amount of cvxCRV staked.
  function totalUnderlying() public view override returns (uint256) {
    // TODO: stakeFor exists in CVXCRV_STAKING, maybe we need maintain correct underlying balance here.
    return IConvexBasicRewards(CVXCRV_STAKING).balanceOf(address(this));
  }

  /// @dev Return the amount of cvxCRV staked for user
  /// @param _user - The address of the account
  function balanceOfUnderlying(address _user) external view override returns (uint256) {
    uint256 _totalSupply = totalSupply();
    if (_totalSupply == 0) return 0;
    uint256 _balance = balanceOf(_user);
    return _balance.mul(totalUnderlying()) / _totalSupply;
  }

  /// @dev Return the amount of pending CRV rewards
  function pendingCRVRewards() public view returns (uint256) {
    return IConvexBasicRewards(CVXCRV_STAKING).earned(address(this));
  }

  /// @dev Return the amount of pending CVX rewards
  function pendingCVXRewards() external view returns (uint256) {
    return ICVXMining(CVX_MINING).ConvertCrvToCvx(pendingCRVRewards());
  }

  /// @dev Return the amount of pending 3CRV rewards
  function pending3CRVRewards() external view returns (uint256) {
    return IConvexVirtualBalanceRewardPool(THREE_CRV_REWARDS).earned(address(this));
  }

  /********************************** Mutated Functions **********************************/

  /// @dev Deposit cvxCRV token to this contract
  /// @param _recipient - The address who will receive the aCRV token.
  /// @param _amount - The amount of cvxCRV to deposit.
  /// @return share - The amount of aCRV received.
  function deposit(address _recipient, uint256 _amount) public override nonReentrant returns (uint256 share) {
    require(_amount > 0, "AladdinCRV: zero amount deposit");
    uint256 _before = IERC20Upgradeable(CVXCRV).balanceOf(address(this));
    IERC20Upgradeable(CVXCRV).safeTransferFrom(msg.sender, address(this), _amount);
    _amount = IERC20Upgradeable(CVXCRV).balanceOf(address(this)).sub(_before);
    return _deposit(_recipient, _amount);
  }

  /// @dev Deposit all cvxCRV token of the sender to this contract
  /// @param _recipient The address who will receive the aCRV token.
  /// @return share - The amount of aCRV received.
  function depositAll(address _recipient) external override returns (uint256 share) {
    uint256 _balance = IERC20Upgradeable(CVXCRV).balanceOf(msg.sender);
    return deposit(_recipient, _balance);
  }

  /// @dev Deposit CRV token to this contract
  /// @param _recipient - The address who will receive the aCRV token.
  /// @param _amount - The amount of CRV to deposit.
  /// @return share - The amount of aCRV received.
  function depositWithCRV(address _recipient, uint256 _amount) public override nonReentrant returns (uint256 share) {
    uint256 _before = IERC20Upgradeable(CRV).balanceOf(address(this));
    IERC20Upgradeable(CRV).safeTransferFrom(msg.sender, address(this), _amount);
    _amount = IERC20Upgradeable(CRV).balanceOf(address(this)).sub(_before);

    _amount = _zapToken(_amount, CRV, _amount, CVXCRV);
    return _deposit(_recipient, _amount);
  }

  /// @dev Deposit all CRV token of the sender to this contract
  /// @param _recipient The address who will receive the aCRV token.
  /// @return share - The amount of aCRV received.
  function depositAllWithCRV(address _recipient) external override returns (uint256 share) {
    uint256 _balance = IERC20Upgradeable(CRV).balanceOf(msg.sender);
    return depositWithCRV(_recipient, _balance);
  }

  /// @dev Withdraw cvxCRV in proportion to the amount of shares sent
  /// @param _recipient - The address who will receive the withdrawn token.
  /// @param _shares - The amount of aCRV to send.
  /// @param _minimumOut - The minimum amount of token should be received.
  /// @param _option - The withdraw option (as cvxCRV or CRV or CVX or ETH or stake to convex).
  /// @return withdrawn - The amount of token returned to the user.
  function withdraw(
    address _recipient,
    uint256 _shares,
    uint256 _minimumOut,
    WithdrawOption _option
  ) public override nonReentrant returns (uint256 withdrawn) {
    uint256 _withdrawed = _withdraw(_shares);
    if (_option == WithdrawOption.Withdraw) {
      require(_withdrawed >= _minimumOut, "AladdinCRV: insufficient output");
      IERC20Upgradeable(CVXCRV).safeTransfer(_recipient, _withdrawed);
    } else {
      _withdrawed = _withdrawAs(_recipient, _withdrawed, _minimumOut, _option);
    }

    emit Withdraw(msg.sender, _recipient, _shares, _option);
    return _withdrawed;
  }

  /// @dev Withdraw all cvxCRV in proportion to the amount of shares sent
  /// @param _recipient - The address who will receive the withdrawn token.
  /// @param _minimumOut - The minimum amount of token should be received.
  /// @param _option - The withdraw option (as cvxCRV or CRV or CVX or ETH or stake to convex).
  /// @return withdrawn - The amount of token returned to the user.
  function withdrawAll(
    address _recipient,
    uint256 _minimumOut,
    WithdrawOption _option
  ) external override returns (uint256) {
    uint256 _shares = balanceOf(msg.sender);
    return withdraw(_recipient, _shares, _minimumOut, _option);
  }

  /// @dev Harvest the pending reward and convert to cvxCRV.
  /// @param _recipient - The address of account to receive harvest bounty.
  /// @param _minimumOut - The minimum amount of cvxCRV should get.
  function harvest(address _recipient, uint256 _minimumOut) public override nonReentrant returns (uint256) {
    return _harvest(_recipient, _minimumOut);
  }

  /********************************** Restricted Functions **********************************/

  /// @dev Update the withdraw fee percentage.
  /// @param _feePercentage - The fee percentage to update.
  function updateWithdrawFeePercentage(uint256 _feePercentage) external onlyOwner {
    require(_feePercentage <= MAX_WITHDRAW_FEE, "AladdinCRV: fee too large");
    withdrawFeePercentage = _feePercentage;

    emit UpdateWithdrawalFeePercentage(_feePercentage);
  }

  /// @dev Update the platform fee percentage.
  /// @param _feePercentage - The fee percentage to update.
  function updatePlatformFeePercentage(uint256 _feePercentage) external onlyOwner {
    require(_feePercentage <= MAX_PLATFORM_FEE, "AladdinCRV: fee too large");
    platformFeePercentage = _feePercentage;

    emit UpdatePlatformFeePercentage(_feePercentage);
  }

  /// @dev Update the harvest bounty percentage.
  /// @param _percentage - The fee percentage to update.
  function updateHarvestBountyPercentage(uint256 _percentage) external onlyOwner {
    require(_percentage <= MAX_HARVEST_BOUNTY, "AladdinCRV: fee too large");
    harvestBountyPercentage = _percentage;

    emit UpdateHarvestBountyPercentage(_percentage);
  }

  /// @dev Update the recipient
  function updatePlatform(address _platform) external onlyOwner {
    require(_platform != address(0), "AladdinCRV: zero platform address");
    platform = _platform;

    emit UpdatePlatform(_platform);
  }

  /// @dev Update the zap contract
  function updateZap(address _zap) external onlyOwner {
    require(_zap != address(0), "AladdinCRV: zero zap address");
    zap = _zap;

    emit UpdateZap(_zap);
  }

  /// @dev Claim EPS airdrop, only used in BSC.
  function claimEPS(
    address _distributor,
    address _recipient,
    uint256 merkleIndex,
    uint256 index,
    uint256 amount,
    bytes32[] calldata merkleProof
  ) external onlyOwner {
    address eps = 0xA7f552078dcC247C2684336020c03648500C6d9F;
    IEllipsisMerkleDistributor(_distributor).claim(merkleIndex, index, amount, merkleProof);
    IERC20Upgradeable(eps).safeTransfer(_recipient, IERC20Upgradeable(eps).balanceOf(address(this)));
  }

  /********************************** Internal Functions **********************************/

  function _deposit(address _recipient, uint256 _amount) internal returns (uint256) {
    require(_amount > 0, "AladdinCRV: zero amount deposit");
    uint256 _underlying = totalUnderlying();
    uint256 _totalSupply = totalSupply();

    IERC20Upgradeable(CVXCRV).safeApprove(CVXCRV_STAKING, 0);
    IERC20Upgradeable(CVXCRV).safeApprove(CVXCRV_STAKING, _amount);
    IConvexBasicRewards(CVXCRV_STAKING).stake(_amount);

    uint256 _shares;
    if (_totalSupply == 0) {
      _shares = _amount;
    } else {
      _shares = _amount.mul(_totalSupply) / _underlying;
    }
    _mint(_recipient, _shares);

    emit Deposit(msg.sender, _recipient, _amount);
    return _shares;
  }

  function _withdraw(uint256 _shares) internal returns (uint256 _withdrawable) {
    require(_shares > 0, "AladdinCRV: zero share withdraw");
    require(_shares <= balanceOf(msg.sender), "AladdinCRV: shares not enough");
    uint256 _amount = _shares.mul(totalUnderlying()) / totalSupply();
    _burn(msg.sender, _shares);

    if (totalSupply() == 0) {
      // If user is last to withdraw, harvest before exit
      // The first parameter is actually not used.
      _harvest(msg.sender, 0);
      IConvexBasicRewards(CVXCRV_STAKING).withdraw(totalUnderlying(), false);
      _withdrawable = IERC20Upgradeable(CVXCRV).balanceOf(address(this));
    } else {
      // Otherwise compute share and unstake
      _withdrawable = _amount;
      // Substract a small withdrawal fee to prevent users "timing"
      // the harvests. The fee stays staked and is therefore
      // redistributed to all remaining participants.
      uint256 _withdrawFee = (_withdrawable * withdrawFeePercentage) / FEE_DENOMINATOR;
      _withdrawable = _withdrawable - _withdrawFee; // never overflow here
      IConvexBasicRewards(CVXCRV_STAKING).withdraw(_withdrawable, false);
    }
    return _withdrawable;
  }

  function _withdrawAs(
    address _recipient,
    uint256 _amount,
    uint256 _minimumOut,
    WithdrawOption _option
  ) internal returns (uint256) {
    if (_option == WithdrawOption.WithdrawAndStake) {
      // simply stake the cvxCRV for _recipient
      require(_amount >= _minimumOut, "AladdinCRV: insufficient output");
      IERC20Upgradeable(CVXCRV).safeApprove(CVXCRV_STAKING, 0);
      IERC20Upgradeable(CVXCRV).safeApprove(CVXCRV_STAKING, _amount);
      require(IConvexBasicRewards(CVXCRV_STAKING).stakeFor(_recipient, _amount), "AladdinCRV: stakeFor failed");
    } else if (_option == WithdrawOption.WithdrawAsCRV) {
      _amount = _zapToken(_amount, CVXCRV, _minimumOut, CRV);
      IERC20Upgradeable(CRV).safeTransfer(_recipient, _amount);
    } else if (_option == WithdrawOption.WithdrawAsETH) {
      _amount = _zapToken(_amount, CVXCRV, _minimumOut, address(0));

      // solhint-disable-next-line avoid-low-level-calls
      (bool success, ) = _recipient.call{ value: _amount }("");
      require(success, "AladdinCRV: ETH transfer failed");
    } else if (_option == WithdrawOption.WithdrawAsCVX) {
      _amount = _zapToken(_amount, CVXCRV, _minimumOut, CVX);
      IERC20Upgradeable(CVX).safeTransfer(_recipient, _amount);
    } else {
      revert("AladdinCRV: unsupported option");
    }
    return _amount;
  }

  function _harvest(address _recipient, uint256 _minimumOut) internal returns (uint256) {
    IConvexBasicRewards(CVXCRV_STAKING).getReward();
    // 1. CVX => ETH
    uint256 _amount = _zapToken(IERC20Upgradeable(CVX).balanceOf(address(this)), CVX, 0, address(0));
    // 2. 3CRV => USDT => ETH
    _amount += _zapToken(IERC20Upgradeable(THREE_CRV).balanceOf(address(this)), THREE_CRV, 0, address(0));
    // 3. ETH => CRV
    _zapToken(_amount, address(0), 0, CRV);
    // 3. CRV => cvxCRV (stake or swap)
    _amount = IERC20Upgradeable(CRV).balanceOf(address(this));
    _zapToken(_amount, CRV, _amount, CVXCRV);

    _amount = IERC20Upgradeable(CVXCRV).balanceOf(address(this));
    require(_amount >= _minimumOut, "AladdinCRV: insufficient rewards");

    emit Harvest(msg.sender, _amount);

    uint256 _totalSupply = totalSupply();
    if (_amount > 0 && _totalSupply > 0) {
      uint256 _stakeAmount = _amount;
      uint256 _platformFee = platformFeePercentage;
      uint256 _harvestBounty = harvestBountyPercentage;
      if (_platformFee > 0) {
        _platformFee = (_platformFee * _stakeAmount) / FEE_DENOMINATOR;
        _stakeAmount = _stakeAmount - _platformFee; // never overflow here
      }
      if (_harvestBounty > 0) {
        _harvestBounty = (_harvestBounty * _stakeAmount) / FEE_DENOMINATOR;
        _stakeAmount = _stakeAmount - _harvestBounty; // never overflow here
      }
      // This is the amount of underlying after staking harvested rewards.
      uint256 _underlying = totalUnderlying() + _stakeAmount;
      // This is the share for platform fee.
      _platformFee = (_platformFee * _totalSupply) / _underlying;
      // This is the share for harvest bounty.
      _harvestBounty = (_harvestBounty * _totalSupply) / _underlying;

      IERC20Upgradeable(CVXCRV).safeApprove(CVXCRV_STAKING, 0);
      IERC20Upgradeable(CVXCRV).safeApprove(CVXCRV_STAKING, _amount);
      IConvexBasicRewards(CVXCRV_STAKING).stake(_amount);
      _mint(platform, _platformFee);
      _mint(_recipient, _harvestBounty);
    }
    return _amount;
  }

  function _zapToken(
    uint256 _amount,
    address _fromToken,
    uint256 _minimumOut,
    address _toToken
  ) internal returns (uint256) {
    if (_amount == 0) return 0;

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory data) = zap.delegatecall(
      abi.encodeWithSignature("zap(address,uint256,address,uint256)", _fromToken, _amount, _toToken, _minimumOut)
    );
    require(success, "AladdinCRV: zap failed");
    return abi.decode(data, (uint256));
  }

  receive() external payable {}
}

// File: @openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "../../utils/ContextUpgradeable.sol";
import "./IERC20Upgradeable.sol";
import "../../math/SafeMathUpgradeable.sol";
import "../../proxy/Initializable.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20Upgradeable is Initializable, ContextUpgradeable, IERC20Upgradeable {
    using SafeMathUpgradeable 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.
     */
    function __ERC20_init(string memory name_, string memory symbol_) internal initializer {
        __Context_init_unchained();
        __ERC20_init_unchained(name_, symbol_);
    }

    function __ERC20_init_unchained(string memory name_, string memory symbol_) internal initializer {
        _name = name_;
        _symbol = symbol_;
        _decimals = 18;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual returns (string memory) {
        return _symbol;
    }

    /**
     * @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 virtual returns (uint8) {
        return _decimals;
    }

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

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual 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 Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal virtual {
        _decimals = decimals_;
    }

    /**
     * @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 { }
    uint256[44] private __gap;
}

// File: @openzeppelin/contracts-upgradeable/token/ERC20/SafeERC20Upgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

import "./IERC20Upgradeable.sol";
import "../../math/SafeMathUpgradeable.sol";
import "../../utils/AddressUpgradeable.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 SafeERC20Upgradeable {
    using SafeMathUpgradeable for uint256;
    using AddressUpgradeable for address;

    function safeTransfer(IERC20Upgradeable token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20Upgradeable 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(IERC20Upgradeable 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(IERC20Upgradeable 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(IERC20Upgradeable 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(IERC20Upgradeable token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

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

// File: @openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

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;
}

// File: @openzeppelin/contracts-upgradeable/utils/ReentrancyGuardUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;
import "../proxy/Initializable.sol";

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuardUpgradeable is Initializable {
    // 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;

    function __ReentrancyGuard_init() internal initializer {
        __ReentrancyGuard_init_unchained();
    }

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

// File: contracts/interfaces/IAladdinCRV.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

import "@openzeppelin/contracts-upgradeable/token/ERC20/IERC20Upgradeable.sol";

interface IAladdinCRV is IERC20Upgradeable {
  event Harvest(address indexed _caller, uint256 _amount);
  event Deposit(address indexed _sender, address indexed _recipient, uint256 _amount);
  event Withdraw(
    address indexed _sender,
    address indexed _recipient,
    uint256 _shares,
    IAladdinCRV.WithdrawOption _option
  );

  event UpdateWithdrawalFeePercentage(uint256 _feePercentage);
  event UpdatePlatformFeePercentage(uint256 _feePercentage);
  event UpdateHarvestBountyPercentage(uint256 _percentage);
  event UpdatePlatform(address indexed _platform);
  event UpdateZap(address indexed _zap);

  enum WithdrawOption {
    Withdraw,
    WithdrawAndStake,
    WithdrawAsCRV,
    WithdrawAsCVX,
    WithdrawAsETH
  }

  /// @dev return the total amount of cvxCRV staked.
  function totalUnderlying() external view returns (uint256);

  /// @dev return the amount of cvxCRV staked for user
  function balanceOfUnderlying(address _user) external view returns (uint256);

  function deposit(address _recipient, uint256 _amount) external returns (uint256);

  function depositAll(address _recipient) external returns (uint256);

  function depositWithCRV(address _recipient, uint256 _amount) external returns (uint256);

  function depositAllWithCRV(address _recipient) external returns (uint256);

  function withdraw(
    address _recipient,
    uint256 _shares,
    uint256 _minimumOut,
    WithdrawOption _option
  ) external returns (uint256);

  function withdrawAll(
    address _recipient,
    uint256 _minimumOut,
    WithdrawOption _option
  ) external returns (uint256);

  function harvest(address _recipient, uint256 _minimumOut) external returns (uint256);
}

// File: contracts/interfaces/IConvexBasicRewards.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

interface IConvexBasicRewards {
  function stakeFor(address, uint256) external returns (bool);

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

  function earned(address) external view returns (uint256);

  function withdrawAll(bool) external returns (bool);

  function withdraw(uint256, bool) external returns (bool);

  function withdrawAndUnwrap(uint256, bool) external returns (bool);

  function getReward() external returns (bool);

  function stake(uint256) external returns (bool);
}

// File: contracts/interfaces/IConvexCRVDepositor.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

interface IConvexCRVDepositor {
  function deposit(
    uint256 _amount,
    bool _lock,
    address _stakeAddress
  ) external;

  function deposit(uint256 _amount, bool _lock) external;

  function lockIncentive() external view returns (uint256);
}

// File: contracts/interfaces/IConvexVirtualBalanceRewardPool.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

interface IConvexVirtualBalanceRewardPool {
  function earned(address account) external view returns (uint256);
}

// File: contracts/interfaces/ICVXMining.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

// solhint-disable func-name-mixedcase
interface ICVXMining {
  function ConvertCrvToCvx(uint256 _amount) external view returns (uint256);
}

// File: contracts/interfaces/IEllipsisMerkleDistributor.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

interface IEllipsisMerkleDistributor {
  function claim(
    uint256 merkleIndex,
    uint256 index,
    uint256 amount,
    bytes32[] calldata merkleProof
  ) external;
}

// File: @openzeppelin/contracts-upgradeable/utils/ContextUpgradeable.sol



// 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;
}

// File: @openzeppelin/contracts-upgradeable/token/ERC20/IERC20Upgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20Upgradeable {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

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

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

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

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

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

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

// File: @openzeppelin/contracts-upgradeable/math/SafeMathUpgradeable.sol



// 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 SafeMathUpgradeable {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

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

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

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

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

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

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

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

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

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

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

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

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

// File: @openzeppelin/contracts-upgradeable/proxy/Initializable.sol



// 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));
    }
}

// File: @openzeppelin/contracts-upgradeable/utils/AddressUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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);
            }
        }
    }
}