// File: contracts/swap/LiquidityGaugeV2.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;
pragma experimental ABIEncoderV2;

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

import "../interfaces/ILiquidityGauge.sol";
import "../interfaces/IChessSchedule.sol";
import "../interfaces/IChessController.sol";
import "../interfaces/IFundV3.sol";
import "../interfaces/ITrancheIndexV2.sol";
import "../interfaces/IStableSwap.sol";
import "../interfaces/IVotingEscrow.sol";

import "../utils/CoreUtility.sol";
import "../utils/SafeDecimalMath.sol";

interface ISwapBonus {
    function bonusToken() external view returns (address);

    function getBonus() external returns (uint256);
}

contract LiquidityGaugeV2 is ILiquidityGauge, ITrancheIndexV2, CoreUtility, ERC20 {
    using Math for uint256;
    using SafeMath for uint256;
    using SafeDecimalMath for uint256;
    using SafeERC20 for IERC20;

    struct Distribution {
        uint256 amountQ;
        uint256 amountB;
        uint256 amountR;
        uint256 quoteAmount;
    }

    uint256 private constant MAX_ITERATIONS = 500;
    uint256 private constant MAX_BOOSTING_FACTOR = 3e18;
    uint256 private constant MAX_BOOSTING_FACTOR_MINUS_ONE = MAX_BOOSTING_FACTOR - 1e18;

    address public immutable stableSwap;
    IERC20 private immutable _quoteToken;
    IChessSchedule public immutable chessSchedule;
    IChessController public immutable chessController;
    IFundV3 public immutable fund;
    IVotingEscrow private immutable _votingEscrow;
    address public immutable swapBonus;
    IERC20 private immutable _bonusToken;

    uint256 private _workingSupply;
    mapping(address => uint256) private _workingBalances;

    uint256 public latestVersion;
    mapping(uint256 => Distribution) public distributions;
    mapping(uint256 => uint256) public distributionTotalSupplies;
    mapping(address => Distribution) public userDistributions;
    mapping(address => uint256) public userVersions;

    uint256 private _chessIntegral;
    uint256 private _chessIntegralTimestamp;
    mapping(address => uint256) private _chessUserIntegrals;
    mapping(address => uint256) private _claimableChess;

    uint256 private _bonusIntegral;
    mapping(address => uint256) private _bonusUserIntegral;
    mapping(address => uint256) private _claimableBonus;

    /// @dev Per-gauge CHESS emission rate. The product of CHESS emission rate
    ///      and weekly percentage of the gauge
    uint256 private _rate;

    constructor(
        string memory name_,
        string memory symbol_,
        address stableSwap_,
        address chessSchedule_,
        address chessController_,
        address fund_,
        address votingEscrow_,
        address swapBonus_
    ) public ERC20(name_, symbol_) {
        stableSwap = stableSwap_;
        _quoteToken = IERC20(IStableSwap(stableSwap_).quoteAddress());
        chessSchedule = IChessSchedule(chessSchedule_);
        chessController = IChessController(chessController_);
        fund = IFundV3(fund_);
        _votingEscrow = IVotingEscrow(votingEscrow_);
        swapBonus = swapBonus_;
        _bonusToken = IERC20(ISwapBonus(swapBonus_).bonusToken());
        _chessIntegralTimestamp = block.timestamp;
    }

    modifier onlyStableSwap() {
        require(msg.sender == stableSwap, "Only stable swap");
        _;
    }

    function getRate() external view returns (uint256) {
        return _rate / 1e18;
    }

    function mint(address account, uint256 amount) external override onlyStableSwap {
        uint256 oldWorkingBalance = _workingBalances[account];
        uint256 oldWorkingSupply = _workingSupply;
        uint256 oldBalance = balanceOf(account);
        _checkpoint(account, oldBalance, oldWorkingBalance, oldWorkingSupply);

        _mint(account, amount);
        _updateWorkingBalance(account, oldWorkingBalance, oldWorkingSupply, oldBalance.add(amount));
    }

    function burnFrom(address account, uint256 amount) external override onlyStableSwap {
        uint256 oldWorkingBalance = _workingBalances[account];
        uint256 oldWorkingSupply = _workingSupply;
        uint256 oldBalance = balanceOf(account);
        _checkpoint(account, oldBalance, oldWorkingBalance, oldWorkingSupply);

        _burn(account, amount);
        _updateWorkingBalance(account, oldWorkingBalance, oldWorkingSupply, oldBalance.sub(amount));
    }

    function _transfer(
        address,
        address,
        uint256
    ) internal override {
        revert("Transfer is not allowed");
    }

    function workingBalanceOf(address account) external view override returns (uint256) {
        return _workingBalances[account];
    }

    function workingSupply() external view override returns (uint256) {
        return _workingSupply;
    }

    function claimableRewards(address account)
        external
        override
        returns (
            uint256 chessAmount,
            uint256 bonusAmount,
            uint256 amountQ,
            uint256 amountB,
            uint256 amountR,
            uint256 quoteAmount
        )
    {
        return _checkpoint(account, balanceOf(account), _workingBalances[account], _workingSupply);
    }

    function claimRewards(address account) external override {
        uint256 balance = balanceOf(account);
        uint256 oldWorkingBalance = _workingBalances[account];
        uint256 oldWorkingSupply = _workingSupply;
        (
            uint256 chessAmount,
            uint256 bonusAmount,
            uint256 amountQ,
            uint256 amountB,
            uint256 amountR,
            uint256 quoteAmount
        ) = _checkpoint(account, balance, oldWorkingBalance, oldWorkingSupply);
        _updateWorkingBalance(account, oldWorkingBalance, oldWorkingSupply, balance);

        if (chessAmount != 0) {
            chessSchedule.mint(account, chessAmount);
            delete _claimableChess[account];
        }
        if (bonusAmount != 0) {
            _bonusToken.safeTransfer(account, bonusAmount);
            delete _claimableBonus[account];
        }
        if (amountQ != 0 || amountB != 0 || amountR != 0 || quoteAmount != 0) {
            uint256 version = latestVersion;
            if (amountQ != 0) {
                fund.trancheTransfer(TRANCHE_Q, account, amountQ, version);
            }
            if (amountB != 0) {
                fund.trancheTransfer(TRANCHE_B, account, amountB, version);
            }
            if (amountR != 0) {
                fund.trancheTransfer(TRANCHE_R, account, amountR, version);
            }
            if (quoteAmount != 0) {
                _quoteToken.safeTransfer(account, quoteAmount);
            }
            delete userDistributions[account];
        }
    }

    function syncWithVotingEscrow(address account) external {
        uint256 balance = balanceOf(account);
        uint256 oldWorkingBalance = _workingBalances[account];
        uint256 oldWorkingSupply = _workingSupply;
        _checkpoint(account, balance, oldWorkingBalance, oldWorkingSupply);
        _updateWorkingBalance(account, oldWorkingBalance, oldWorkingSupply, balance);
    }

    function distribute(
        uint256 amountQ,
        uint256 amountB,
        uint256 amountR,
        uint256 quoteAmount,
        uint256 version
    ) external override onlyStableSwap {
        // Update global state
        distributions[version].amountQ = amountQ;
        distributions[version].amountB = amountB;
        distributions[version].amountR = amountR;
        distributions[version].quoteAmount = quoteAmount;
        distributionTotalSupplies[version] = totalSupply();
        latestVersion = version;
    }

    function _updateWorkingBalance(
        address account,
        uint256 oldWorkingBalance,
        uint256 oldWorkingSupply,
        uint256 newBalance
    ) private {
        uint256 newWorkingBalance = newBalance;
        uint256 veBalance = _votingEscrow.balanceOf(account);
        if (veBalance > 0) {
            uint256 veTotalSupply = _votingEscrow.totalSupply();
            uint256 maxWorkingBalance = newWorkingBalance.multiplyDecimal(MAX_BOOSTING_FACTOR);
            uint256 boostedWorkingBalance =
                newWorkingBalance.add(
                    totalSupply().mul(veBalance).multiplyDecimal(MAX_BOOSTING_FACTOR_MINUS_ONE).div(
                        veTotalSupply
                    )
                );
            newWorkingBalance = maxWorkingBalance.min(boostedWorkingBalance);
        }
        _workingSupply = oldWorkingSupply.sub(oldWorkingBalance).add(newWorkingBalance);
        _workingBalances[account] = newWorkingBalance;
    }

    function _checkpoint(
        address account,
        uint256 balance,
        uint256 weight,
        uint256 totalWeight
    )
        private
        returns (
            uint256 chessAmount,
            uint256 bonusAmount,
            uint256 amountQ,
            uint256 amountB,
            uint256 amountR,
            uint256 quoteAmount
        )
    {
        chessAmount = _chessCheckpoint(account, weight, totalWeight);
        bonusAmount = _bonusCheckpoint(account, weight, totalWeight);
        (amountQ, amountB, amountR, quoteAmount) = _distributionCheckpoint(account, balance);
    }

    function _chessCheckpoint(
        address account,
        uint256 weight,
        uint256 totalWeight
    ) private returns (uint256 amount) {
        // Update global state
        uint256 timestamp = _chessIntegralTimestamp;
        uint256 integral = _chessIntegral;
        uint256 endWeek = _endOfWeek(timestamp);
        uint256 rate = _rate;
        if (rate == 0) {
            // CHESS emission may update in the middle of a week due to cross-chain lag.
            // We re-calculate the rate if it was zero after the last checkpoint.
            uint256 weeklySupply = chessSchedule.getWeeklySupply(timestamp);
            if (weeklySupply != 0) {
                rate = (weeklySupply / (endWeek - timestamp)).mul(
                    chessController.getFundRelativeWeight(address(this), timestamp)
                );
            }
        }
        for (uint256 i = 0; i < MAX_ITERATIONS && timestamp < block.timestamp; i++) {
            uint256 endTimestamp = endWeek.min(block.timestamp);
            if (totalWeight != 0) {
                integral = integral.add(
                    rate.mul(endTimestamp - timestamp).decimalToPreciseDecimal().div(totalWeight)
                );
            }
            if (endTimestamp == endWeek) {
                rate = chessSchedule.getRate(endWeek).mul(
                    chessController.getFundRelativeWeight(address(this), endWeek)
                );
                endWeek += 1 weeks;
            }
            timestamp = endTimestamp;
        }
        _chessIntegralTimestamp = block.timestamp;
        _chessIntegral = integral;
        _rate = rate;

        // Update per-user state
        amount = _claimableChess[account].add(
            weight.multiplyDecimalPrecise(integral.sub(_chessUserIntegrals[account]))
        );
        _claimableChess[account] = amount;
        _chessUserIntegrals[account] = integral;
    }

    function _bonusCheckpoint(
        address account,
        uint256 weight,
        uint256 totalWeight
    ) private returns (uint256 amount) {
        // Update global state
        uint256 newBonus = ISwapBonus(swapBonus).getBonus();
        uint256 integral = _bonusIntegral;
        if (totalWeight != 0 && newBonus != 0) {
            integral = integral.add(newBonus.divideDecimalPrecise(totalWeight));
            _bonusIntegral = integral;
        }

        // Update per-user state
        uint256 oldUserIntegral = _bonusUserIntegral[account];
        if (oldUserIntegral == integral) {
            return _claimableBonus[account];
        }
        amount = _claimableBonus[account].add(
            weight.multiplyDecimalPrecise(integral.sub(oldUserIntegral))
        );
        _claimableBonus[account] = amount;
        _bonusUserIntegral[account] = integral;
    }

    function _distributionCheckpoint(address account, uint256 balance)
        private
        returns (
            uint256 amountQ,
            uint256 amountB,
            uint256 amountR,
            uint256 quoteAmount
        )
    {
        uint256 version = userVersions[account];
        uint256 newVersion = latestVersion;

        // Update per-user state
        Distribution storage userDist = userDistributions[account];
        amountQ = userDist.amountQ;
        amountB = userDist.amountB;
        amountR = userDist.amountR;
        quoteAmount = userDist.quoteAmount;
        if (version == newVersion) {
            return (amountQ, amountB, amountR, quoteAmount);
        }
        for (uint256 i = version; i < newVersion; i++) {
            if (amountQ != 0 || amountB != 0 || amountR != 0) {
                (amountQ, amountB, amountR) = fund.doRebalance(amountQ, amountB, amountR, i);
            }
            Distribution storage dist = distributions[i + 1];
            uint256 distTotalSupply = distributionTotalSupplies[i + 1];
            if (distTotalSupply != 0) {
                amountQ = amountQ.add(dist.amountQ.mul(balance).div(distTotalSupply));
                amountB = amountB.add(dist.amountB.mul(balance).div(distTotalSupply));
                amountR = amountR.add(dist.amountR.mul(balance).div(distTotalSupply));
                quoteAmount = quoteAmount.add(dist.quoteAmount.mul(balance).div(distTotalSupply));
            }
        }
        userDist.amountQ = amountQ;
        userDist.amountB = amountB;
        userDist.amountR = amountR;
        userDist.quoteAmount = quoteAmount;
        userVersions[account] = newVersion;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../../utils/Context.sol";
import "./IERC20.sol";
import "../../math/SafeMath.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 ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;

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

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

    /**
     * @dev Returns the 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 { }
}

// 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/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: contracts/interfaces/ILiquidityGauge.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface ILiquidityGauge is IERC20 {
    function mint(address account, uint256 amount) external;

    function burnFrom(address account, uint256 amount) external;

    function workingSupply() external view returns (uint256);

    function workingBalanceOf(address account) external view returns (uint256);

    function claimableRewards(address account)
        external
        returns (
            uint256 chessAmount,
            uint256 bonusAmount,
            uint256 amountQ,
            uint256 amountB,
            uint256 amountR,
            uint256 quoteAmount
        );

    function claimRewards(address account) external;

    function distribute(
        uint256 amountQ,
        uint256 amountB,
        uint256 amountR,
        uint256 quoteAmount,
        uint256 version
    ) external;
}

// File: contracts/interfaces/IChessSchedule.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

interface IChessSchedule {
    function getWeeklySupply(uint256 timestamp) external view returns (uint256);

    function getRate(uint256 timestamp) external view returns (uint256);

    function mint(address account, uint256 amount) external;

    function addMinter(address account) external;
}

// File: contracts/interfaces/IChessController.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

interface IChessController {
    function getFundRelativeWeight(address account, uint256 timestamp) external returns (uint256);
}

// File: contracts/interfaces/IFundV3.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;
pragma experimental ABIEncoderV2;

import "./ITwapOracleV2.sol";

interface IFundV3 {
    /// @notice A linear transformation matrix that represents a rebalance.
    ///
    ///         ```
    ///             [        1        0        0 ]
    ///         R = [ ratioB2Q  ratioBR        0 ]
    ///             [ ratioR2Q        0  ratioBR ]
    ///         ```
    ///
    ///         Amounts of the three tranches `q`, `b` and `r` can be rebalanced by multiplying the matrix:
    ///
    ///         ```
    ///         [ q', b', r' ] = [ q, b, r ] * R
    ///         ```
    struct Rebalance {
        uint256 ratioB2Q;
        uint256 ratioR2Q;
        uint256 ratioBR;
        uint256 timestamp;
    }

    function tokenUnderlying() external view returns (address);

    function tokenQ() external view returns (address);

    function tokenB() external view returns (address);

    function tokenR() external view returns (address);

    function tokenShare(uint256 tranche) external view returns (address);

    function primaryMarket() external view returns (address);

    function primaryMarketUpdateProposal() external view returns (address, uint256);

    function strategy() external view returns (address);

    function strategyUpdateProposal() external view returns (address, uint256);

    function underlyingDecimalMultiplier() external view returns (uint256);

    function twapOracle() external view returns (ITwapOracleV2);

    function feeCollector() external view returns (address);

    function endOfDay(uint256 timestamp) external pure returns (uint256);

    function trancheTotalSupply(uint256 tranche) external view returns (uint256);

    function trancheBalanceOf(uint256 tranche, address account) external view returns (uint256);

    function trancheAllBalanceOf(address account)
        external
        view
        returns (
            uint256,
            uint256,
            uint256
        );

    function trancheBalanceVersion(address account) external view returns (uint256);

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

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

    function trancheTransfer(
        uint256 tranche,
        address recipient,
        uint256 amount,
        uint256 version
    ) external;

    function trancheTransferFrom(
        uint256 tranche,
        address sender,
        address recipient,
        uint256 amount,
        uint256 version
    ) external;

    function trancheApprove(
        uint256 tranche,
        address spender,
        uint256 amount,
        uint256 version
    ) external;

    function getRebalanceSize() external view returns (uint256);

    function getRebalance(uint256 index) external view returns (Rebalance memory);

    function getRebalanceTimestamp(uint256 index) external view returns (uint256);

    function currentDay() external view returns (uint256);

    function splitRatio() external view returns (uint256);

    function historicalSplitRatio(uint256 version) external view returns (uint256);

    function fundActivityStartTime() external view returns (uint256);

    function isFundActive(uint256 timestamp) external view returns (bool);

    function getEquivalentTotalB() external view returns (uint256);

    function getEquivalentTotalQ() external view returns (uint256);

    function historicalEquivalentTotalB(uint256 timestamp) external view returns (uint256);

    function historicalNavs(uint256 timestamp) external view returns (uint256 navB, uint256 navR);

    function extrapolateNav(uint256 price)
        external
        view
        returns (
            uint256,
            uint256,
            uint256
        );

    function doRebalance(
        uint256 amountQ,
        uint256 amountB,
        uint256 amountR,
        uint256 index
    )
        external
        view
        returns (
            uint256 newAmountQ,
            uint256 newAmountB,
            uint256 newAmountR
        );

    function batchRebalance(
        uint256 amountQ,
        uint256 amountB,
        uint256 amountR,
        uint256 fromIndex,
        uint256 toIndex
    )
        external
        view
        returns (
            uint256 newAmountQ,
            uint256 newAmountB,
            uint256 newAmountR
        );

    function refreshBalance(address account, uint256 targetVersion) external;

    function refreshAllowance(
        address owner,
        address spender,
        uint256 targetVersion
    ) external;

    function shareTransfer(
        address sender,
        address recipient,
        uint256 amount
    ) external;

    function shareTransferFrom(
        address spender,
        address sender,
        address recipient,
        uint256 amount
    ) external returns (uint256 newAllowance);

    function shareIncreaseAllowance(
        address sender,
        address spender,
        uint256 addedValue
    ) external returns (uint256 newAllowance);

    function shareDecreaseAllowance(
        address sender,
        address spender,
        uint256 subtractedValue
    ) external returns (uint256 newAllowance);

    function shareApprove(
        address owner,
        address spender,
        uint256 amount
    ) external;

    function historicalUnderlying(uint256 timestamp) external view returns (uint256);

    function getTotalUnderlying() external view returns (uint256);

    function getStrategyUnderlying() external view returns (uint256);

    function getTotalDebt() external view returns (uint256);

    event RebalanceTriggered(
        uint256 indexed index,
        uint256 indexed day,
        uint256 navSum,
        uint256 navB,
        uint256 navROrZero,
        uint256 ratioB2Q,
        uint256 ratioR2Q,
        uint256 ratioBR
    );
    event Settled(uint256 indexed day, uint256 navB, uint256 navR, uint256 interestRate);
    event InterestRateUpdated(uint256 baseInterestRate, uint256 floatingInterestRate);
    event BalancesRebalanced(
        address indexed account,
        uint256 version,
        uint256 balanceQ,
        uint256 balanceB,
        uint256 balanceR
    );
    event AllowancesRebalanced(
        address indexed owner,
        address indexed spender,
        uint256 version,
        uint256 allowanceQ,
        uint256 allowanceB,
        uint256 allowanceR
    );
}

// File: contracts/interfaces/ITrancheIndexV2.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

/// @notice Amounts of QUEEN, BISHOP and ROOK are sometimes stored in a `uint256[3]` array.
///         This contract defines index of each tranche in this array.
///
///         Solidity does not allow constants to be defined in interfaces. So this contract follows
///         the naming convention of interfaces but is implemented as an `abstract contract`.
abstract contract ITrancheIndexV2 {
    uint256 internal constant TRANCHE_Q = 0;
    uint256 internal constant TRANCHE_B = 1;
    uint256 internal constant TRANCHE_R = 2;

    uint256 internal constant TRANCHE_COUNT = 3;
}

// File: contracts/interfaces/IStableSwap.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

import "../interfaces/IFundV3.sol";

interface IStableSwapCore {
    function getQuoteOut(uint256 baseIn) external view returns (uint256 quoteOut);

    function getQuoteIn(uint256 baseOut) external view returns (uint256 quoteIn);

    function getBaseOut(uint256 quoteIn) external view returns (uint256 baseOut);

    function getBaseIn(uint256 quoteOut) external view returns (uint256 baseIn);

    function buy(
        uint256 version,
        uint256 baseOut,
        address recipient,
        bytes calldata data
    ) external returns (uint256 realBaseOut);

    function sell(
        uint256 version,
        uint256 quoteOut,
        address recipient,
        bytes calldata data
    ) external returns (uint256 realQuoteOut);
}

interface IStableSwap is IStableSwapCore {
    function fund() external view returns (IFundV3);

    function baseTranche() external view returns (uint256);

    function baseAddress() external view returns (address);

    function quoteAddress() external view returns (address);

    function allBalances() external view returns (uint256, uint256);

    function getOraclePrice() external view returns (uint256);

    function getCurrentD() external view returns (uint256);

    function getCurrentPriceOverOracle() external view returns (uint256);

    function getCurrentPrice() external view returns (uint256);

    function getPriceOverOracleIntegral() external view returns (uint256);

    function addLiquidity(uint256 version, address recipient) external returns (uint256);

    function removeLiquidity(
        uint256 version,
        uint256 lpIn,
        uint256 minBaseOut,
        uint256 minQuoteOut
    ) external returns (uint256 baseOut, uint256 quoteOut);

    function removeLiquidityUnwrap(
        uint256 version,
        uint256 lpIn,
        uint256 minBaseOut,
        uint256 minQuoteOut
    ) external returns (uint256 baseOut, uint256 quoteOut);

    function removeBaseLiquidity(
        uint256 version,
        uint256 lpIn,
        uint256 minBaseOut
    ) external returns (uint256 baseOut);

    function removeQuoteLiquidity(
        uint256 version,
        uint256 lpIn,
        uint256 minQuoteOut
    ) external returns (uint256 quoteOut);

    function removeQuoteLiquidityUnwrap(
        uint256 version,
        uint256 lpIn,
        uint256 minQuoteOut
    ) external returns (uint256 quoteOut);
}

// File: contracts/interfaces/IVotingEscrow.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;
pragma experimental ABIEncoderV2;

interface IAddressWhitelist {
    function check(address account) external view returns (bool);
}

interface IVotingEscrowCallback {
    function syncWithVotingEscrow(address account) external;
}

interface IVotingEscrow {
    struct LockedBalance {
        uint256 amount;
        uint256 unlockTime;
    }

    function token() external view returns (address);

    function maxTime() external view returns (uint256);

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

    function totalSupply() external view returns (uint256);

    function balanceOfAtTimestamp(address account, uint256 timestamp)
        external
        view
        returns (uint256);

    function getTimestampDropBelow(address account, uint256 threshold)
        external
        view
        returns (uint256);

    function getLockedBalance(address account) external view returns (LockedBalance memory);
}

// File: contracts/utils/CoreUtility.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

import "@openzeppelin/contracts/math/SafeMath.sol";

abstract contract CoreUtility {
    using SafeMath for uint256;

    /// @dev UTC time of a day when the fund settles.
    uint256 internal constant SETTLEMENT_TIME = 14 hours;

    /// @dev Return end timestamp of the trading week containing a given timestamp.
    ///
    ///      A trading week starts at UTC time `SETTLEMENT_TIME` on a Thursday (inclusive)
    ///      and ends at the same time of the next Thursday (exclusive).
    /// @param timestamp The given timestamp
    /// @return End timestamp of the trading week.
    function _endOfWeek(uint256 timestamp) internal pure returns (uint256) {
        return ((timestamp.add(1 weeks) - SETTLEMENT_TIME) / 1 weeks) * 1 weeks + SETTLEMENT_TIME;
    }
}

// File: contracts/utils/SafeDecimalMath.sol



// SPDX-License-Identifier: MIT
//
// Copyright (c) 2019 Synthetix
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
pragma solidity >=0.6.10 <0.8.0;

import "@openzeppelin/contracts/math/SafeMath.sol";

library SafeDecimalMath {
    using SafeMath for uint256;

    /* Number of decimal places in the representations. */
    uint256 private constant decimals = 18;
    uint256 private constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint256 private constant UNIT = 10**uint256(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint256 private constant PRECISE_UNIT = 10**uint256(highPrecisionDecimals);
    uint256 private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR =
        10**uint256(highPrecisionDecimals - decimals);

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint256 x, uint256 y) internal pure returns (uint256) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y).div(UNIT);
    }

    function multiplyDecimalPrecise(uint256 x, uint256 y) internal pure returns (uint256) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y).div(PRECISE_UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint256 x, uint256 y) internal pure returns (uint256) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    function divideDecimalPrecise(uint256 x, uint256 y) internal pure returns (uint256) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(PRECISE_UNIT).div(y);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint256 i) internal pure returns (uint256) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint256 i) internal pure returns (uint256) {
        uint256 quotientTimesTen = i.mul(10).div(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen = quotientTimesTen.add(10);
        }

        return quotientTimesTen.div(10);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, and the max value of
     * uint256 on overflow.
     */
    function saturatingMul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        return c / a != b ? type(uint256).max : c;
    }

    function saturatingMultiplyDecimal(uint256 x, uint256 y) internal pure returns (uint256) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return saturatingMul(x, y).div(UNIT);
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

// File: @openzeppelin/contracts/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: contracts/interfaces/ITwapOracleV2.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

import "./ITwapOracle.sol";

interface ITwapOracleV2 is ITwapOracle {
    function getLatest() external view returns (uint256);
}

// File: contracts/interfaces/ITwapOracle.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.10 <0.8.0;

interface ITwapOracle {
    enum UpdateType {PRIMARY, SECONDARY, OWNER, CHAINLINK, UNISWAP_V2}

    function getTwap(uint256 timestamp) external view returns (uint256);
}