// File: contracts/vaults/Vault.sol



pragma solidity ^0.6.0;

import "./base/BaseVaultV2.sol";
import "./base/VaultWithAutoStake.sol";
import "./base/VaultWithFees.sol";
import "./base/VaultWithReferralProgram.sol";

/// @title CVXVault
/// @notice Vault for staking of CVX and receive rewards in cvxCRV
contract Vault is
    BaseVaultV2,
    VaultWithAutoStake,
    VaultWithFees,
    VaultWithReferralProgram
{
    constructor(string memory _name, string memory _symbol)
        public
        BaseVaultV2(_name, _symbol)
    {}

    function configure(
        address _initialToken,
        address _initialController,
        address _governance,
        uint256 _rewardsDuration,
        address _tokenToAutostake,
        address _votingStakingRewards,
        bool _enableFees,
        address _depositFeeWallet,
        address _referralProgram,
        address _treasury,
        address[] memory _rewardsTokens,
        string memory _namePostfix,
        string memory _symbolPostfix
    ) public onlyOwner initializer {
        _configureVaultWithAutoStake(_tokenToAutostake, _votingStakingRewards);
        _configureVaultWithFees(_depositFeeWallet, _enableFees);
        _configureVaultWithReferralProgram(_referralProgram, _treasury);
        _configure(
            _initialToken,
            _initialController,
            _governance,
            _rewardsDuration,
            _rewardsTokens,
            _namePostfix,
            _symbolPostfix
        );
    }

    function _deposit(address _from, uint256 _amount)
        internal
        override
        returns (uint256)
    {
        _amount = _getFeesOnDeposit(stakingToken, _amount);
        super._deposit(_from, _amount);
        _registerUserInReferralProgramIfNeeded(_from);
        return _amount;
    }

    function _getReward(
        bool _claimUnderlying,
        address _for,
        address _rewardToken,
        address _stakingToken
    ) internal override returns (uint256 claimedReward) {
        if (_claimUnderlying) {
            _controller.getRewardStrategy(_stakingToken);
        }
        claimedReward = _controller.claim(_stakingToken, _rewardToken);
        uint256 reward = rewards[_for][_rewardToken];
        if (reward > 0) {
            rewards[_for][_rewardToken] = 0;
            reward = _getFeesOnClaimForToken(_for, _rewardToken, reward);
            _autoStakeForOrSendTo(_rewardToken, reward, _for);
        }
        emit RewardPaid(_rewardToken, _for, reward);
    }
}

// File: contracts/vaults/base/BaseVaultV2.sol



pragma solidity ^0.6.0;

import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/utils/EnumerableSet.sol";

import "@openzeppelin/contracts/proxy/Initializable.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/utils/Pausable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

import "./utils/ERC20Vault.sol";

import "../../interfaces/vault/IVaultCore.sol";
import "../../interfaces/vault/IVaultTransfers.sol";
import "../../interfaces/IController.sol";
import "../../interfaces/IStrategy.sol";

/// @title EURxbVault
/// @notice Base vault contract, used to manage funds of the clients
abstract contract BaseVaultV2 is
    IVaultCore,
    IVaultTransfers,
    ERC20Vault,
    Ownable,
    ReentrancyGuard,
    Pausable,
    Initializable
{
    using EnumerableSet for EnumerableSet.AddressSet;
    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    /// @notice Controller instance, to simplify controller-related actions
    IController internal _controller;

    IERC20 public stakingToken;
    uint256 public periodFinish;
    uint256 public rewardsDuration;
    uint256 public lastUpdateTime;
    address public rewardsDistribution;

    // token => reward per token stored
    mapping(address => uint256) public rewardsPerTokensStored;

    // reward token => reward rate
    mapping(address => uint256) public rewardRates;

    // valid token => user => amount
    mapping(address => mapping(address => uint256))
    public userRewardPerTokenPaid;

    // user => valid token => amount
    mapping(address => mapping(address => uint256)) public rewards;

    EnumerableSet.AddressSet internal _validTokens;

    address public trustworthyEarnCaller;

    /* ========== EVENTS ========== */

    event RewardAdded(address what, uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address what, address indexed user, uint256 reward);
    event RewardsDurationUpdated(uint256 newDuration);

    constructor(string memory _name, string memory _symbol)
        public
        ERC20Vault(_name, _symbol)
    {
        trustworthyEarnCaller = _msgSender();
    }

    /// @notice Default initialize method for solving migration linearization problem
    /// @dev Called once only by deployer
    /// @param _initialToken Business token logic address
    /// @param _initialController Controller instance address
    function _configure(
        address _initialToken,
        address _initialController,
        address _governance,
        uint256 _rewardsDuration,
        address[] memory _rewardsTokens,
        string memory _namePostfix,
        string memory _symbolPostfix
    ) internal {
        setController(_initialController);
        transferOwnership(_governance);
        stakingToken = IERC20(_initialToken);
        rewardsDuration = _rewardsDuration;
        _name = string(abi.encodePacked(_name, _namePostfix));
        _symbol = string(abi.encodePacked(_symbol, _symbolPostfix));
        for (uint256 i = 0; i < _rewardsTokens.length; i++) {
            _validTokens.add(_rewardsTokens[i]);
        }
    }

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public override returns (bool) {
        _updateAllRewards(sender);
        _updateAllRewards(recipient);
        _transfer(sender, recipient, amount);
        _approve(
            sender,
            _msgSender(),
            _allowances[sender][_msgSender()].sub(
                amount,
                "ERC20: transfer amount exceeds allowance"
            )
        );
        return true;
    }


    function transfer(address recipient, uint256 amount)
        public
        override
        returns (bool)
    {
        address sender = _msgSender();
        _updateAllRewards(sender);
        _updateAllRewards(recipient);
        _transfer(sender, recipient, amount);
        return true;
    }

    function setTrustworthyEarnCaller(address _who) external onlyOwner {
        trustworthyEarnCaller = _who;
    }

    /// @notice Usual setter with check if passet param is new
    /// @param _newController New value
    function setController(address _newController) public onlyOwner {
        require(address(_controller) != _newController, "!new");
        _controller = IController(_newController);
    }

    function setRewardsDistribution(address _rewardsDistribution)
        external
        onlyOwner
    {
        rewardsDistribution = _rewardsDistribution;
    }

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

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

    function setRewardsDuration(uint256 _rewardsDuration) external onlyOwner {
        require(block.timestamp > periodFinish, "!periodFinish");
        rewardsDuration = _rewardsDuration;
        emit RewardsDurationUpdated(rewardsDuration);
    }

    function addRewardToken(address _rewardToken) external onlyOwner {
        require(_validTokens.add(_rewardToken), "!add");
    }

    function removeRewardToken(address _rewardToken) external onlyOwner {
        require(_validTokens.remove(_rewardToken), "!remove");
    }

    function isTokenValid(address _rewardToken) external view returns (bool) {
        return _validTokens.contains(_rewardToken);
    }

    function getRewardToken(uint256 _index) external view returns (address) {
        return _validTokens.at(_index);
    }

    function getRewardTokensCount() external view returns (uint256) {
        return _validTokens.length();
    }

    function lastTimeRewardApplicable() public view returns (uint256) {
        return Math.min(block.timestamp, periodFinish);
    }

    function rewardPerToken(address _rewardToken)
        public
        view
        onlyValidToken(_rewardToken)
        returns (uint256)
    {
        if (_totalSupply == 0) {
            return rewardsPerTokensStored[_rewardToken];
        }
        return
        rewardsPerTokensStored[_rewardToken].add(
            lastTimeRewardApplicable()
            .sub(lastUpdateTime)
            .mul(rewardRates[_rewardToken])
            .mul(1e18)
            .div(_totalSupply)
        );
    }

    function earned(address _rewardToken, address _account)
        public
        view
        virtual
        onlyValidToken(_rewardToken)
        returns (uint256)
    {
        return
        _balances[_account]
        .mul(
            rewardPerToken(_rewardToken).sub(
                userRewardPerTokenPaid[_rewardToken][_account]
            )
        )
        .div(1e18)
        .add(rewards[_account][_rewardToken]);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function _deposit(address _from, uint256 _amount)
        internal
        virtual
        returns (uint256)
    {
        require(_amount > 0, "Cannot stake 0");
        stakingToken.safeTransferFrom(msg.sender, address(this), _amount);
        _mint(_from, _amount);
        emit Staked(_from, _amount);
        return _amount;
    }

    function deposit(uint256 amount)
        public
        override
        nonReentrant
        whenNotPaused
        updateReward(msg.sender)
    {
        _deposit(msg.sender, amount);
    }

    function depositFor(uint256 _amount, address _for)
        public
        override
        nonReentrant
        whenNotPaused
        updateReward(_for)
    {
        _deposit(_for, _amount);
    }

    function depositAll()
        public
        override
        nonReentrant
        whenNotPaused
        updateReward(msg.sender)
    {
        uint256 _balance = stakingToken.balanceOf(msg.sender);
        require(_balance > 0, "0balance");
        _deposit(msg.sender, _balance);
    }

    function _withdrawFrom(address _from, uint256 _amount)
        internal
        virtual
        returns (uint256)
    {
        require(_amount > 0, "Cannot withdraw 0");
        _burn(msg.sender, _amount);
        address strategyAddress = IController(_controller).strategies(
            address(stakingToken)
        );
        uint256 amountOnVault = stakingToken.balanceOf(address(this));
        if (amountOnVault < _amount) {
            IStrategy(strategyAddress).withdraw(_amount.sub(amountOnVault));
        }
        stakingToken.safeTransfer(_from, _amount);
        emit Withdrawn(_from, _amount);
        return _amount;
    }

    function _withdraw(uint256 _amount) internal returns (uint256) {
        return _withdrawFrom(msg.sender, _amount);
    }

    function withdraw(uint256 _amount) public virtual override {
        withdraw(_amount, true);
    }

    function withdrawAll() public virtual override {
        withdraw(_balances[msg.sender], true);
    }

    function withdraw(uint256 _amount, bool _claimUnderlying)
        public
        virtual
        nonReentrant
        updateReward(msg.sender)
    {
        _getRewardAll(_claimUnderlying);
        _withdraw(_amount);
    }

    function _getReward(
        bool _claimUnderlying,
        address _for,
        address _rewardToken,
        address _stakingToken
    ) internal virtual returns (uint256 claimedReward) {
        if (_claimUnderlying) {
            _controller.getRewardStrategy(_stakingToken);
        }
        claimedReward = _controller.claim(_stakingToken, _rewardToken);
        uint256 reward = rewards[_for][_rewardToken];
        if (reward > 0) {
            rewards[_for][_rewardToken] = 0;
            IERC20(_rewardToken).safeTransfer(_for, reward);
        }
        emit RewardPaid(_rewardToken, _for, reward);
    }

    function _getRewardAll(bool _claimUnderlying) internal virtual {
        bool rewardExists;
        for (uint256 i = 0; i < _validTokens.length(); i++) {
            uint256 claimedReward = _getReward(
                _claimUnderlying,
                msg.sender,
                _validTokens.at(i),
                address(stakingToken)
            );
            if (claimedReward > 0) {
                rewardExists = true;
            }
        }
        if (rewardExists) {
            lastUpdateTime = block.timestamp;
            periodFinish = block.timestamp.add(rewardsDuration);
        }
    }

    function getReward(bool _claimUnderlying)
        public
        virtual
        nonReentrant
        updateReward(msg.sender)
    {
        _getRewardAll(_claimUnderlying);
    }

    /* ========== RESTRICTED FUNCTIONS ========== */

    function notifyRewardAmount(address _rewardToken, uint256 _reward)
        external
        virtual
        onlyRewardsDistribution
        onlyValidToken(_rewardToken)
        updateReward(address(0))
    {
        if (block.timestamp >= periodFinish) {
            rewardRates[_rewardToken] = _reward.div(rewardsDuration);
        } else {
            uint256 remaining = periodFinish.sub(block.timestamp);
            uint256 leftover = remaining.mul(rewardRates[_rewardToken]);
            rewardRates[_rewardToken] = _reward.add(leftover).div(
                rewardsDuration
            );
        }

        // Ensure the provided reward amount is not more than the balance in the contract.
        // This keeps the reward rate in the right range, preventing overflows due to
        // very high values of rewardRate in the earned and rewardsPerToken functions;
        // Reward + leftover must be less than 2^256 / 10^18 to avoid overflow.
        uint256 balance = IERC20(_rewardToken).balanceOf(address(this));
        require(
            rewardRates[_rewardToken] <= balance.div(rewardsDuration),
            "Provided reward too high"
        );
        emit RewardAdded(_rewardToken, _reward);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyValidToken(address _rewardToken) {
        require(_validTokens.contains(_rewardToken), "!valid");
        _;
    }

    function userReward(address _account, address _token)
        external
        view
        onlyValidToken(_token)
        returns (uint256)
    {
        return rewards[_account][_token];
    }

    function _updateReward(address _what, address _account) internal virtual {
        rewardsPerTokensStored[_what] = rewardPerToken(_what);
        if (_account != address(0)) {
            rewards[_account][_what] = earned(_what, _account);
            userRewardPerTokenPaid[_what][_account] = rewardsPerTokensStored[
            _what
            ];
        }
    }

    function _updateAllRewards(address _account) internal virtual {
        for (uint256 i = 0; i < _validTokens.length(); i++) {
            _updateReward(_validTokens.at(i), _account);
        }
        lastUpdateTime = lastTimeRewardApplicable();
    }

    modifier updateReward(address _account) {
        _updateAllRewards(_account);
        _;
    }

    modifier onlyRewardsDistribution() {
        require(
            msg.sender == rewardsDistribution,
            "Caller is not RewardsDistribution contract"
        );
        _;
    }

    /// @notice Transfer tokens to controller, controller transfers it to strategy and earn (farm)
    function earn() external virtual override {
        require(_msgSender() == trustworthyEarnCaller, "!trustworthyEarnCaller");
        uint256 _bal = stakingToken.balanceOf(address(this));
        if (_bal > 0) {
            stakingToken.safeTransfer(address(_controller), _bal);
            _controller.earn(address(stakingToken), _bal);
        }
        bool rewardExists;
        for (uint256 i = 0; i < _validTokens.length(); i++) {
            uint256 claimedReward = _controller.claim(address(stakingToken), _validTokens.at(i));
            if (claimedReward > 0) {
                rewardExists = true;
            }
        }
        if (rewardExists) {
            lastUpdateTime = block.timestamp;
            periodFinish = block.timestamp.add(rewardsDuration);
        }
    }

    function token() external view override returns (address) {
        return address(stakingToken);
    }

    function controller() external view override returns (address) {
        return address(_controller);
    }

    function balance() public view override returns (uint256) {
        IStrategy strategy = IStrategy(
            _controller.strategies(address(stakingToken))
        );
        return stakingToken.balanceOf(address(this)).add(strategy.balanceOf());
    }

    function _rewardPerTokenForDuration(
        address _rewardsToken,
        uint256 _duration
    ) internal view returns (uint256) {
        if (_totalSupply == 0) {
            return rewardsPerTokensStored[_rewardsToken];
        }
        return
        rewardsPerTokensStored[_rewardsToken].add(
            _duration.mul(rewardRates[_rewardsToken]).mul(1e18).div(
                _totalSupply
            )
        );
    }

    function potentialRewardReturns(
        address _rewardsToken,
        uint256 _duration,
        address _account
    ) external view returns (uint256) {
        uint256 _rewardsAmount = _balances[_account]
        .mul(
            _rewardPerTokenForDuration(_rewardsToken, _duration).sub(
                userRewardPerTokenPaid[_rewardsToken][msg.sender]
            )
        )
        .div(1e18)
        .add(rewards[_account][_rewardsToken]);
        return _rewardsAmount;
    }
}

// File: contracts/vaults/base/VaultWithAutoStake.sol



pragma solidity ^0.6.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";

import "../../interfaces/IAutoStakeFor.sol";

abstract contract VaultWithAutoStake {
    using SafeERC20 for IERC20;

    address public votingStakingRewards;
    address public tokenToAutostake;

    function _configureVaultWithAutoStake(
        address _tokenToAutostake,
        address _votingStakingRewards
    ) internal {
        votingStakingRewards = _votingStakingRewards;
        tokenToAutostake = _tokenToAutostake;
    }

    function _autoStakeForOrSendTo(
        address _token,
        uint256 _amount,
        address _receiver
    ) internal {
        if (_token == tokenToAutostake) {
            IERC20(_token).safeApprove(votingStakingRewards, 0);
            IERC20(_token).safeApprove(votingStakingRewards, _amount);
            IAutoStakeFor(votingStakingRewards).stakeFor(_receiver, _amount);
        } else {
            IERC20(_token).safeTransfer(_receiver, _amount);
        }
    }
}

// File: contracts/vaults/base/VaultWithFees.sol



pragma solidity ^0.6.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "../../interfaces/ITreasury.sol";
import "../../interfaces/IFeeReceiving.sol";

abstract contract VaultWithFees is Ownable {
    using SafeERC20 for IERC20;
    using SafeMath for uint256;
    using Address for address;

    struct ClaimFee {
        uint64 percentage;
        address to;
        bool needFeeReceiving;
    }

    mapping(address => mapping(address => bool)) claimFeeToAvaibleTokens;
    ClaimFee[] internal claimFee;
    uint64 public sumClaimFee;
    bool public claimFeesEnabled;

    struct DepositFee {
        uint64 percentage;
        address to;
    }

    DepositFee public depositFee;

    uint64 public constant PCT_BASE = 100000;

    event SetDepositFee(uint256 fee);
    event SetDepositWallet(address to);

    function _configureVaultWithFees(
        address _depositFeeWallet,
        bool _enableClaimFees
    ) internal {
        claimFeesEnabled = _enableClaimFees;
        depositFee.to = _depositFeeWallet;
    }

    function setFeesEnabled(bool _isFeesEnabled) external onlyOwner {
        claimFeesEnabled = _isFeesEnabled;
    }

    function addClaimFeeReceiver(
        address _to,
        uint64 _percentage,
        bool _needFeeReceiving,
        address[] calldata _tokens
    ) external onlyOwner {
        require(sumClaimFee + _percentage <= PCT_BASE, "!sumClaimFee overflow");
        ClaimFee storage newWeight;
        newWeight.to = _to;
        newWeight.percentage = _percentage;
        newWeight.needFeeReceiving = _needFeeReceiving;
        for (uint256 i = 0; i < _tokens.length; i++) {
            claimFeeToAvaibleTokens[_to][_tokens[i]] = true;
        }
        claimFee.push(newWeight);
        sumClaimFee = sumClaimFee + _percentage;
    }

    function claimFeeReceiversCount() external view returns (uint256) {
        return claimFee.length;
    }

    function claimFeeReceivers(uint256 _index)
        external
        view
        returns (
            uint64,
            address,
            bool
        )
    {
        return (
            claimFee[_index].percentage,
            claimFee[_index].to,
            claimFee[_index].needFeeReceiving
        );
    }

    function removeClaimFeeReceiver(uint256 _index) external onlyOwner {
        require(_index < claimFee.length, "indexOutOfBound");
        sumClaimFee = sumClaimFee - claimFee[_index].percentage;
        claimFee[_index] = claimFee[claimFee.length - 1];
        claimFee.pop();
    }

    function setClaimFeePercentage(uint256 _index, uint64 _percentage)
        external
        onlyOwner
    {
        require(_index < claimFee.length, "indexOutOfBound");
        require(uint256(sumClaimFee).add(uint256(_percentage)) <= uint256(uint64(-1)), "checkPercentageOverflow");
        sumClaimFee = sumClaimFee + _percentage - claimFee[_index].percentage;
        claimFee[_index].percentage = _percentage;
    }

    function setDepositFee(uint64 _newPercentage) external onlyOwner {
        require(
            _newPercentage < PCT_BASE &&
                _newPercentage != depositFee.percentage,
            "Invalid percentage"
        );
        depositFee.percentage = _newPercentage;
        emit SetDepositFee(_newPercentage);
    }

    function setDepositWallet(address _to) external onlyOwner {
        depositFee.to = _to;
        emit SetDepositWallet(_to);
    }

    function _getFeesOnClaimForToken(
        address _for,
        address _rewardToken,
        uint256 _amount
    ) internal returns (uint256) {
        if (!claimFeesEnabled) {
            return _amount;
        }
        uint256 fee;
        for (uint256 i = 0; i < claimFee.length; i++) {
            fee = uint256(claimFee[i].percentage).mul(_amount).div(PCT_BASE);
            if (claimFeeToAvaibleTokens[claimFee[i].to][_rewardToken]) {
                IERC20(_rewardToken).safeTransfer(claimFee[i].to, fee);
            }
            _amount = _amount.sub(fee);
            if (claimFee[i].to.isContract() && claimFee[i].needFeeReceiving) {
                IFeeReceiving(claimFee[i].to).feeReceiving(_for, _rewardToken, fee);
            }
        }
        return _amount;
    }

    function _getFeesOnDeposit(IERC20 _stakingToken, uint256 _amount)
        internal
        returns (uint256 _sumWithoutFee)
    {
        if (depositFee.percentage > 0) {
            uint256 _fee = uint256(depositFee.percentage).mul(_amount).div(PCT_BASE);
            _stakingToken.safeTransfer(depositFee.to, _fee);
            _sumWithoutFee = _amount.sub(_fee);
        } else {
            _sumWithoutFee = _amount;
        }
    }
}

// File: contracts/vaults/base/VaultWithReferralProgram.sol



pragma solidity ^0.6.0;

import "../../interfaces/IReferralProgram.sol";

/// @title WithReferalProgramVault
/// @notice Vault for consumers of the system
abstract contract VaultWithReferralProgram {
    /// @notice The referral program
    IReferralProgram public referralProgram;
    address public treasury;

    function _configureVaultWithReferralProgram(
        address _referralProgram,
        address _treasury
    ) internal {
        referralProgram = IReferralProgram(_referralProgram);
        treasury = _treasury;
    }

    function _registerUserInReferralProgramIfNeeded(address _user) internal {
        (bool _userExists, ) = referralProgram.users(_user);
        if (!_userExists) {
            referralProgram.registerUser(treasury, _user);
        }
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

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

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

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

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

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

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

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

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

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

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

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

            bytes32 lastvalue = set._values[lastIndex];

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

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

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

            return true;
        } else {
            return false;
        }
    }

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

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

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

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

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

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

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

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

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

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }

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

   /**
    * @dev Returns the value stored at position `index` in the set. O(1).
    *
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }


    // UintSet

    struct UintSet {
        Set _inner;
    }

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

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

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

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

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

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



// SPDX-License-Identifier: MIT

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

import "../utils/Address.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 !Address.isContract(address(this));
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

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

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

        _;

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

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./Context.sol";

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

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

    bool private _paused;

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

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

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

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

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

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

// File: contracts/vaults/base/utils/ERC20Vault.sol



pragma solidity >=0.6.0 <0.8.0;

// SPDX-License-Identifier: MIT

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Context.sol";

contract ERC20Vault is Context, IERC20 {
    using SafeMath for uint256;

    mapping(address => uint256) internal _balances;

    mapping(address => mapping(address => uint256)) internal _allowances;

    uint256 internal _totalSupply;

    string internal _name;
    string internal _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) public {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @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 18;
    }

    /**
     * @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");

        _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");

        _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");

        _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);
    }
}

// File: contracts/interfaces/vault/IVaultCore.sol



pragma solidity ^0.6.0;

interface IVaultCore {
    function token() external view returns (address);

    function controller() external view returns (address);

    function balance() external view returns (uint256);

    function earn() external;
}

// File: contracts/interfaces/vault/IVaultTransfers.sol



pragma solidity ^0.6.0;

interface IVaultTransfers {
    function deposit(uint256 _amount) external;

    function depositFor(uint256 _amount, address _for) external;

    function depositAll() external;

    function withdraw(uint256 _amount) external;

    function withdrawAll() external;
}

// File: contracts/interfaces/IController.sol



pragma solidity ^0.6.0;

interface IController {
    function withdraw(address, uint256) external;

    function earn(address, uint256) external;

    function rewards() external view returns (address);

    function vaults(address) external view returns (address);

    function strategies(address) external view returns (address);

    function approvedStrategies(address, address) external view returns (bool);

    function setVault(address, address) external;

    function setStrategy(address, address) external;

    function converters(address, address) external view returns (address);

    function claim(address, address) external returns (uint256);

    function getRewardStrategy(address _strategy) external;
}

// File: contracts/interfaces/IStrategy.sol



pragma solidity ^0.6.0;

interface IStrategy {
    function want() external view returns (address);

    function deposit() external;

    /// NOTE: must exclude any tokens used in the yield
    /// Controller role - withdraw should return to Controller
    function withdraw(address) external;

    /// Controller | Vault role - withdraw should always return to Vault
    function withdraw(uint256) external;

    function balanceOf() external view returns (uint256);

    function setController(address) external;

    function setWant(address) external;

    function getRewards() external;

    function claim(address) external returns (uint256);
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

// File: contracts/interfaces/IAutoStakeFor.sol



pragma solidity ^0.6.0;

interface IAutoStakeFor {
    function stakeFor(address _for, uint256 amount) external;
}

// File: contracts/interfaces/ITreasury.sol



pragma solidity ^0.6.0;

/*
@dev The Treasury contract accumulates all the Management fees sent from the strategies.
It's an intermediate contract that can convert between different tokens,
currently normalizing all rewards into provided default token.
*/
interface ITreasury {
    function toVoters() external;

    function toGovernance(address _token, uint256 _amount) external;

    function convertToRewardsToken(address _token, uint256 amount, uint256 amountOutMin) external;
}

// File: contracts/interfaces/IFeeReceiving.sol



pragma solidity ^0.6.0;

interface IFeeReceiving {
    function feeReceiving(
        address _for,
        address _token,
        uint256 _amount
    ) external;
}

// File: contracts/interfaces/IReferralProgram.sol



pragma solidity ^0.6.0;

interface IReferralProgram {
    struct User {
        bool exists;
        address referrer;
    }

    function users(address wallet)
        external
        returns (bool exists, address referrer);

    function registerUser(address referrer, address referral) external;

    function feeReceiving(
        address _for,
        address _token,
        uint256 _amount
    ) external;
}