// File: contracts/governance/VotingEscrowV3.sol



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

import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/math/Math.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";

import "./VotingEscrowCheckpoint.sol";
import "../utils/CoreUtility.sol";
import "../utils/ManagedPausable.sol";
import "../interfaces/IVotingEscrow.sol";
import "../utils/ProxyUtility.sol";

import "../anyswap/AnyCallAppBase.sol";
import "../anyswap/AnyswapChessPool.sol";
import "../interfaces/IAnyswapV6ERC20.sol";

contract VotingEscrowV3 is
    IVotingEscrow,
    OwnableUpgradeable,
    ReentrancyGuard,
    CoreUtility,
    VotingEscrowCheckpoint,
    ManagedPausable,
    ProxyUtility,
    AnyCallAppBase
{
    /// @dev Reserved storage slots for future base contract upgrades
    uint256[29] private _reservedSlots;

    using Math for uint256;
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    event LockCreated(address indexed account, uint256 amount, uint256 unlockTime);

    event AmountIncreased(address indexed account, uint256 increasedAmount);

    event AmountDecreased(address indexed account, uint256 decreasedAmount);

    event UnlockTimeIncreased(address indexed account, uint256 newUnlockTime);

    event Withdrawn(address indexed account, uint256 amount);

    event CrossChainSent(
        address indexed account,
        uint256 toChainID,
        uint256 amount,
        uint256 unlockTime
    );

    event CrossChainReceived(
        address indexed account,
        uint256 fromChainID,
        uint256 amount,
        uint256 newUnlockTime
    );

    event CrossChainVotingEscrowUpdated(uint256 chainID, address votingEscrow);

    uint8 public constant decimals = 18;

    uint256 public constant MIN_CROSS_CHAIN_SENDER_LOCK_PERIOD = 4 weeks;
    uint256 public constant MIN_CROSS_CHAIN_RECEIVER_LOCK_PERIOD = 3 weeks;

    address public immutable override token;

    /// @notice Address of AnyswapChessPool (on BNB Chain) or AnyswapChess (on other chains).
    address public immutable anyswapChess;

    string public name;
    string public symbol;

    address public addressWhitelist;

    mapping(address => LockedBalance) public locked;

    /// @notice Mapping of unlockTime => total amount that will be unlocked at unlockTime
    mapping(uint256 => uint256) public scheduledUnlock;

    /// @notice max lock time allowed at the moment
    uint256 public maxTimeAllowed;

    /// @notice Contract to be called when an account's locked CHESS is decreased
    address public callback;

    /// @notice Amount of Chess locked now. Expired locks are not included.
    uint256 public totalLocked;

    /// @notice Total veCHESS at the end of the last checkpoint's week
    uint256 public nextWeekSupply;

    /// @notice Mapping of week => vote-locked chess total supplies
    ///
    ///         Key is the start timestamp of a week on each Thursday. Value is
    ///         vote-locked chess total supplies captured at the start of each week
    mapping(uint256 => uint256) public veSupplyPerWeek;

    /// @notice Start timestamp of the trading week in which the last checkpoint is made
    uint256 public checkpointWeek;

    /// @notice Mapping of chain ID => VotingEscrow address on that chain
    mapping(uint256 => address) public crossChainVotingEscrows;

    constructor(
        address token_,
        uint256 maxTime_,
        address anyswapChess_,
        address anyCallProxy_
    ) public VotingEscrowCheckpoint(maxTime_) AnyCallAppBase(anyCallProxy_, true, true) {
        token = token_;
        anyswapChess = anyswapChess_;
    }

    /// @dev Initialize the contract. The contract is designed to be used with OpenZeppelin's
    ///      `TransparentUpgradeableProxy`. This function should be called by the proxy's
    ///      constructor (via the `_data` argument).
    function initialize(
        string memory name_,
        string memory symbol_,
        uint256 maxTimeAllowed_
    ) external initializer {
        __Ownable_init();
        require(maxTimeAllowed_ <= _maxTime, "Cannot exceed max time");
        maxTimeAllowed = maxTimeAllowed_;
        _initializeV2(msg.sender, name_, symbol_);
    }

    /// @dev Initialize the part added in V2. If this contract is upgraded from the previous
    ///      version, call `upgradeToAndCall` of the proxy and put a call to this function
    ///      in the `data` argument.
    ///
    ///      In the previous version, name and symbol were not correctly initialized via proxy.
    function initializeV2(
        address pauser_,
        string memory name_,
        string memory symbol_
    ) external onlyProxyAdmin {
        _initializeV2(pauser_, name_, symbol_);
    }

    function _initializeV2(
        address pauser_,
        string memory name_,
        string memory symbol_
    ) private {
        _initializeManagedPausable(pauser_);
        require(bytes(name).length == 0 && bytes(symbol).length == 0);
        name = name_;
        symbol = symbol_;

        // Initialize totalLocked, nextWeekSupply and checkpointWeek
        uint256 nextWeek = _endOfWeek(block.timestamp);
        uint256 totalLocked_ = 0;
        uint256 nextWeekSupply_ = 0;
        for (
            uint256 weekCursor = nextWeek;
            weekCursor <= nextWeek + _maxTime;
            weekCursor += 1 weeks
        ) {
            totalLocked_ = totalLocked_.add(scheduledUnlock[weekCursor]);
            nextWeekSupply_ = nextWeekSupply_.add(
                (scheduledUnlock[weekCursor].mul(weekCursor - nextWeek)) / _maxTime
            );
        }
        totalLocked = totalLocked_;
        nextWeekSupply = nextWeekSupply_;
        checkpointWeek = nextWeek - 1 weeks;
    }

    function maxTime() external view override returns (uint256) {
        return _maxTime;
    }

    function getTimestampDropBelow(address account, uint256 threshold)
        external
        view
        override
        returns (uint256)
    {
        LockedBalance memory lockedBalance = locked[account];
        if (lockedBalance.amount == 0 || lockedBalance.amount < threshold) {
            return 0;
        }
        return lockedBalance.unlockTime.sub(threshold.mul(_maxTime).div(lockedBalance.amount));
    }

    function balanceOf(address account) external view override returns (uint256) {
        return _balanceOfAtTimestamp(account, block.timestamp);
    }

    function totalSupply() external view override returns (uint256) {
        return _veTotalSupply(scheduledUnlock, checkpointWeek, nextWeekSupply, totalLocked);
    }

    function getLockedBalance(address account)
        external
        view
        override
        returns (LockedBalance memory)
    {
        return locked[account];
    }

    function balanceOfAtTimestamp(address account, uint256 timestamp)
        external
        view
        override
        returns (uint256)
    {
        return _balanceOfAtTimestamp(account, timestamp);
    }

    function totalSupplyAtTimestamp(uint256 timestamp) external view returns (uint256) {
        return _totalSupplyAtTimestamp(timestamp);
    }

    function createLock(uint256 amount, uint256 unlockTime) external nonReentrant whenNotPaused {
        _assertNotContract();
        require(
            unlockTime + 1 weeks == _endOfWeek(unlockTime),
            "Unlock time must be end of a week"
        );
        LockedBalance memory lockedBalance = locked[msg.sender];
        require(amount > 0, "Zero value");
        require(lockedBalance.amount == 0, "Withdraw old tokens first");
        require(unlockTime > block.timestamp, "Can only lock until time in the future");
        require(
            unlockTime <= block.timestamp + maxTimeAllowed,
            "Voting lock cannot exceed max lock time"
        );

        _checkpointAndUpdateLock(0, 0, amount, unlockTime);
        locked[msg.sender].unlockTime = unlockTime;
        locked[msg.sender].amount = amount;
        IERC20(token).safeTransferFrom(msg.sender, address(this), amount);
        emit LockCreated(msg.sender, amount, unlockTime);
    }

    function increaseAmount(address account, uint256 amount) external nonReentrant whenNotPaused {
        LockedBalance memory lockedBalance = locked[account];
        require(amount > 0, "Zero value");
        require(lockedBalance.unlockTime > block.timestamp, "Cannot add to expired lock");

        uint256 newAmount = lockedBalance.amount.add(amount);
        _checkpointAndUpdateLock(
            lockedBalance.amount,
            lockedBalance.unlockTime,
            newAmount,
            lockedBalance.unlockTime
        );
        locked[account].amount = newAmount;
        IERC20(token).safeTransferFrom(msg.sender, address(this), amount);
        emit AmountIncreased(account, amount);
    }

    function increaseUnlockTime(uint256 unlockTime) external nonReentrant whenNotPaused {
        require(
            unlockTime + 1 weeks == _endOfWeek(unlockTime),
            "Unlock time must be end of a week"
        );
        LockedBalance memory lockedBalance = locked[msg.sender];

        require(lockedBalance.unlockTime > block.timestamp, "Lock expired");
        require(unlockTime > lockedBalance.unlockTime, "Can only increase lock duration");
        require(
            unlockTime <= block.timestamp + maxTimeAllowed,
            "Voting lock cannot exceed max lock time"
        );

        _checkpointAndUpdateLock(
            lockedBalance.amount,
            lockedBalance.unlockTime,
            lockedBalance.amount,
            unlockTime
        );
        locked[msg.sender].unlockTime = unlockTime;
        emit UnlockTimeIncreased(msg.sender, unlockTime);
    }

    function withdraw() external nonReentrant {
        LockedBalance memory lockedBalance = locked[msg.sender];
        require(block.timestamp >= lockedBalance.unlockTime, "The lock is not expired");
        uint256 amount = uint256(lockedBalance.amount);

        lockedBalance.unlockTime = 0;
        lockedBalance.amount = 0;
        locked[msg.sender] = lockedBalance;

        IERC20(token).safeTransfer(msg.sender, amount);

        emit Withdrawn(msg.sender, amount);
    }

    /// @notice Transfer locked CHESS to the VotingEscrow on another chain. User should pay cross
    ///         chain fee in native currency (e.g. ETH on Ethereum) when calling this function.
    ///         Exact fee amount can be queried from the AnyCall proxy contract, i.e.
    ///         `IAnyCallV6Proxy(thisContract.anyCallProxy()).calcSrcFees(thisContract, toChainID, 96)`.
    /// @param amount Amount of locked CHESS
    /// @param toChainID Target chain ID
    function veChessCrossChain(uint256 amount, uint256 toChainID)
        external
        payable
        nonReentrant
        whenNotPaused
    {
        LockedBalance memory lockedBalance = locked[msg.sender];
        require(amount > 0, "Zero value");
        require(
            lockedBalance.unlockTime > block.timestamp + MIN_CROSS_CHAIN_SENDER_LOCK_PERIOD,
            "Lock period too short"
        );

        uint256 newAmount = lockedBalance.amount.sub(amount);
        _checkpointAndUpdateLock(
            lockedBalance.amount,
            lockedBalance.unlockTime,
            newAmount,
            lockedBalance.unlockTime
        );
        locked[msg.sender].amount = newAmount;

        // Deposit CHESS to AnySwap pool
        address underlying = IAnyswapV6ERC20(anyswapChess).underlying();
        if (underlying != address(0)) {
            // anyswapChess is an AnyswapChessPool contract
            require(token == underlying);
            IERC20(token).safeTransfer(anyswapChess, amount);
        } else {
            // anyswapChess is an AnyswapChess contract
            IAnyswapV6ERC20(anyswapChess).burn(address(this), amount);
        }

        address to = crossChainVotingEscrows[toChainID];
        require(to != address(0), "Unknown chain ID");
        _anyCall(to, toChainID, abi.encode(msg.sender, amount, lockedBalance.unlockTime));

        if (callback != address(0)) {
            IVotingEscrowCallback(callback).syncWithVotingEscrow(msg.sender);
        }

        // Unlock time can only be reset after the callback is invoked, because some veCHESS-related
        // contracts won't refresh the user's locked balance in `syncWithVotingEscrow()` if
        // unlock time is zero.
        if (newAmount == 0) {
            locked[msg.sender].unlockTime = 0;
        }

        emit AmountDecreased(msg.sender, amount);
        emit CrossChainSent(msg.sender, toChainID, amount, lockedBalance.unlockTime);
    }

    function _checkAnyExecuteFrom(address from, uint256 fromChainID)
        internal
        override
        returns (bool)
    {
        return from == crossChainVotingEscrows[fromChainID];
    }

    function _checkAnyFallbackTo(address to, uint256 fromChainID) internal override returns (bool) {
        return to == crossChainVotingEscrows[fromChainID];
    }

    /// @dev Receive cross chain veCHESS transfer.
    function _anyExecute(uint256 fromChainID, bytes calldata data) internal override {
        (address account, uint256 amount, uint256 unlockTime) =
            abi.decode(data, (address, uint256, uint256));
        _receiveCrossChain(account, amount, unlockTime, fromChainID);
    }

    /// @dev When `veChessCrossChain` failed, this function is called by the anyCall proxy
    ///      to add locked CHESS back to the account.
    function _anyFallback(bytes memory data) internal override {
        (address account, uint256 amount, uint256 unlockTime) =
            abi.decode(data, (address, uint256, uint256));
        _receiveCrossChain(account, amount, unlockTime, 0);
    }

    function _receiveCrossChain(
        address account,
        uint256 amount,
        uint256 unlockTime,
        uint256 fromChainID
    ) private nonReentrant {
        require(
            unlockTime + 1 weeks == _endOfWeek(unlockTime),
            "Unlock time must be end of a week"
        );
        LockedBalance memory lockedBalance = locked[account];
        if (lockedBalance.amount == 0) {
            require(
                !Address.isContract(account) ||
                    (addressWhitelist != address(0) &&
                        IAddressWhitelist(addressWhitelist).check(account)),
                "Smart contract depositors not allowed"
            );
        }
        uint256 newAmount = lockedBalance.amount.add(amount);
        uint256 newUnlockTime =
            lockedBalance.unlockTime.max(unlockTime).max(
                _endOfWeek(block.timestamp) + MIN_CROSS_CHAIN_RECEIVER_LOCK_PERIOD
            );
        _checkpointAndUpdateLock(
            lockedBalance.amount,
            lockedBalance.unlockTime,
            newAmount,
            newUnlockTime
        );
        locked[account].amount = newAmount;
        locked[account].unlockTime = newUnlockTime;

        // Withdraw CHESS from AnySwap pool
        address underlying = IAnyswapV6ERC20(anyswapChess).underlying();
        if (underlying != address(0)) {
            // anyswapChess is an AnyswapChessPool contract
            require(token == underlying);
            AnyswapChessPool(anyswapChess).withdrawUnderlying(amount);
        } else {
            // anyswapChess is an AnyswapChess contract
            IAnyswapV6ERC20(anyswapChess).mint(address(this), amount);
        }
        emit AmountIncreased(account, amount);
        if (newUnlockTime != lockedBalance.unlockTime) {
            emit UnlockTimeIncreased(account, newUnlockTime);
        }
        emit CrossChainReceived(account, fromChainID, amount, newUnlockTime);
    }

    function updateAddressWhitelist(address newWhitelist) external onlyOwner {
        require(
            newWhitelist == address(0) || Address.isContract(newWhitelist),
            "Must be null or a contract"
        );
        addressWhitelist = newWhitelist;
    }

    function updateCallback(address newCallback) external onlyOwner {
        require(
            newCallback == address(0) || Address.isContract(newCallback),
            "Must be null or a contract"
        );
        callback = newCallback;
    }

    function updateCrossChainVotingEscrow(uint256 chainID, address votingEscrow)
        external
        onlyOwner
    {
        crossChainVotingEscrows[chainID] = votingEscrow;
        emit CrossChainVotingEscrowUpdated(chainID, votingEscrow);
    }

    function _assertNotContract() private view {
        if (msg.sender != tx.origin) {
            if (
                addressWhitelist != address(0) &&
                IAddressWhitelist(addressWhitelist).check(msg.sender)
            ) {
                return;
            }
            revert("Smart contract depositors not allowed");
        }
    }

    function _balanceOfAtTimestamp(address account, uint256 timestamp)
        private
        view
        returns (uint256)
    {
        require(timestamp >= block.timestamp, "Must be current or future time");
        LockedBalance memory lockedBalance = locked[account];
        if (timestamp > lockedBalance.unlockTime) {
            return 0;
        }
        return (lockedBalance.amount.mul(lockedBalance.unlockTime - timestamp)) / _maxTime;
    }

    function _totalSupplyAtTimestamp(uint256 timestamp) private view returns (uint256) {
        uint256 weekCursor = _endOfWeek(timestamp);
        uint256 total = 0;
        for (; weekCursor <= timestamp + _maxTime; weekCursor += 1 weeks) {
            total = total.add((scheduledUnlock[weekCursor].mul(weekCursor - timestamp)) / _maxTime);
        }
        return total;
    }

    /// @dev Pre-conditions:
    ///
    ///      - `newAmount > 0`
    ///      - `newUnlockTime > block.timestamp`
    ///      - `newUnlockTime + 1 weeks == _endOfWeek(newUnlockTime)`, i.e. aligned to a trading week
    ///
    ///      The latter two conditions gaurantee that `newUnlockTime` is no smaller than
    ///      `_endOfWeek(block.timestamp)`.
    function _checkpointAndUpdateLock(
        uint256 oldAmount,
        uint256 oldUnlockTime,
        uint256 newAmount,
        uint256 newUnlockTime
    ) private {
        uint256 newNextWeekSupply;
        uint256 newTotalLocked;
        (checkpointWeek, newNextWeekSupply, newTotalLocked) = _veCheckpoint(
            scheduledUnlock,
            checkpointWeek,
            nextWeekSupply,
            totalLocked,
            veSupplyPerWeek
        );
        (nextWeekSupply, totalLocked) = _veUpdateLock(
            newNextWeekSupply,
            newTotalLocked,
            oldAmount,
            oldUnlockTime,
            newAmount,
            newUnlockTime,
            scheduledUnlock
        );
    }

    function updateMaxTimeAllowed(uint256 newMaxTimeAllowed) external onlyOwner {
        require(newMaxTimeAllowed <= _maxTime, "Cannot exceed max time");
        require(newMaxTimeAllowed > maxTimeAllowed, "Cannot shorten max time allowed");
        maxTimeAllowed = newMaxTimeAllowed;
    }

    /// @notice Recalculate `nextWeekSupply` from scratch. This function eliminates accumulated
    ///         rounding errors in `nextWeekSupply`, which is incrementally updated in
    ///         `createLock`, `increaseAmount` and `increaseUnlockTime`. It is almost
    ///         never required.
    /// @dev Search "rounding error" in test cases for details about the rounding errors.
    function calibrateSupply() external {
        uint256 nextWeek = checkpointWeek + 1 weeks;
        nextWeekSupply = _totalSupplyAtTimestamp(nextWeek);
    }
}

// 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/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/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/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/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-upgradeable/access/OwnableUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

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

    function __Ownable_init_unchained() internal initializer {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

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

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

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

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
    uint256[49] private __gap;
}

// File: contracts/governance/VotingEscrowCheckpoint.sol



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

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

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

/// @dev This abstract contract incrementally calculates the total amount of veCHESS in each week.
///      A derived contract should maintain the following state variables:
///
///      * `mapping(uint256 => uint256) scheduledUnlock`, amount of CHESS that will be
///        unlocked in each week in the future.
///      * `mapping(uint256 => uint256) veSupplyPerWeek`, total veCHESS in each week in the past.
///      * `uint256 checkpointWeek`, start timestamp of the week when the checkpoint was updated
///         the last time.
///      * `uint256 nextWeekSupply`, total veCHESS at the end of the last checkpoint's week.
///      * `uint256 totalLocked`, amount of CHESS locked now.
abstract contract VotingEscrowCheckpoint is CoreUtility {
    using SafeMath for uint256;

    uint256 internal immutable _maxTime;

    constructor(uint256 maxTime_) internal {
        _maxTime = maxTime_;
    }

    /// @dev Update checkpoint to the given week and record weekly supply in the past.
    ///      This function should be called before any update to `scheduledUnlock`.
    ///      It writes new values to the `veSupplyPerWeek` mapping. Caller is responsible for
    ///      setting `checkpointWeek`, `nextWeekSupply` and `totalLocked` to the return values.
    /// @param scheduledUnlock amount of CHESS that will be unlocked in each week
    /// @param checkpointWeek the old checkpoint timestamp
    /// @param nextWeekSupply total veCHESS at the end of the last checkpoint's week
    /// @param totalLocked amount of CHESS locked in the last checkpoint
    /// @param veSupplyPerWeek total veCHESS in each week, written by this function
    /// @return newCheckpointWeek the new checkpoint timestamp
    /// @return newNextWeekSupply total veCHESS at the end of this trading week
    /// @return newTotalLocked amount of CHESS locked now
    function _veCheckpoint(
        mapping(uint256 => uint256) storage scheduledUnlock,
        uint256 checkpointWeek,
        uint256 nextWeekSupply,
        uint256 totalLocked,
        mapping(uint256 => uint256) storage veSupplyPerWeek
    )
        internal
        returns (
            uint256 newCheckpointWeek,
            uint256 newNextWeekSupply,
            uint256 newTotalLocked
        )
    {
        uint256 nextWeek = _endOfWeek(block.timestamp);
        for (uint256 w = checkpointWeek + 1 weeks; w < nextWeek; w += 1 weeks) {
            veSupplyPerWeek[w] = nextWeekSupply;
            // Remove CHESS unlocked at the beginning of the next week from total locked amount.
            totalLocked = totalLocked.sub(scheduledUnlock[w]);
            // Calculate supply at the end of the next week.
            nextWeekSupply = nextWeekSupply.sub(totalLocked.mul(1 weeks) / _maxTime);
        }
        newCheckpointWeek = nextWeek - 1 weeks;
        newNextWeekSupply = nextWeekSupply;
        newTotalLocked = totalLocked;
    }

    /// @dev Update `scheduledUnlock` and the checkpoint according to the change of a user's locked CHESS.
    ///      This function should be called after the checkpoint is updated by `veCheckpoint()`.
    ///      It updates the `scheduledUnlock` mapping. Caller is responsible for setting
    ///      `nextWeekSupply` and `totalLocked` to the return values.
    /// @param nextWeekSupply total veCHESS at the end of this trading week before this change
    /// @param totalLocked amount of CHESS locked before this change
    /// @param oldAmount old amount of locked CHESS
    /// @param oldUnlockTime old unlock timestamp
    /// @param newAmount new amount of locked CHESS
    /// @param newUnlockTime new unlock timestamp
    /// @param scheduledUnlock amount of CHESS that will be unlocked in each week, updated by this function
    /// @return newNextWeekSupply total veCHESS at at the end of this trading week after this change
    /// @return newTotalLocked amount of CHESS locked after this change
    function _veUpdateLock(
        uint256 nextWeekSupply,
        uint256 totalLocked,
        uint256 oldAmount,
        uint256 oldUnlockTime,
        uint256 newAmount,
        uint256 newUnlockTime,
        mapping(uint256 => uint256) storage scheduledUnlock
    ) internal returns (uint256 newNextWeekSupply, uint256 newTotalLocked) {
        uint256 nextWeek = _endOfWeek(block.timestamp);
        newTotalLocked = totalLocked;
        newNextWeekSupply = nextWeekSupply;
        // Remove the old schedule if there is one
        if (oldAmount > 0 && oldUnlockTime >= nextWeek) {
            newTotalLocked = newTotalLocked.sub(oldAmount);
            newNextWeekSupply = newNextWeekSupply.sub(
                oldAmount.mul(oldUnlockTime - nextWeek) / _maxTime
            );
        }
        newTotalLocked = newTotalLocked.add(newAmount);
        // Round up on division when added to the total supply, so that the total supply is never
        // smaller than the sum of all accounts' veCHESS balance.
        newNextWeekSupply = newNextWeekSupply.add(
            newAmount.mul(newUnlockTime - nextWeek).add(_maxTime - 1) / _maxTime
        );

        if (oldUnlockTime == newUnlockTime) {
            scheduledUnlock[oldUnlockTime] = scheduledUnlock[oldUnlockTime].sub(oldAmount).add(
                newAmount
            );
        } else {
            if (oldUnlockTime >= nextWeek) {
                scheduledUnlock[oldUnlockTime] = scheduledUnlock[oldUnlockTime].sub(oldAmount);
            }
            scheduledUnlock[newUnlockTime] = scheduledUnlock[newUnlockTime].add(newAmount);
        }
    }

    /// @dev Calculate the current total veCHESS amount from the last checkpoint.
    /// @param scheduledUnlock amount of CHESS that will be unlocked in each week
    /// @param checkpointWeek the last checkpoint timestamp
    /// @param nextWeekSupply total veCHESS at the end of the last checkpoint's week
    /// @param totalLocked amount of CHESS locked in the last checkpoint
    /// @return Current total veCHESS amount
    function _veTotalSupply(
        mapping(uint256 => uint256) storage scheduledUnlock,
        uint256 checkpointWeek,
        uint256 nextWeekSupply,
        uint256 totalLocked
    ) internal view returns (uint256) {
        uint256 nextWeek = _endOfWeek(block.timestamp);
        uint256 thisWeek = nextWeek - 1 weeks;
        if (checkpointWeek + 1 weeks < nextWeek) {
            for (uint256 w = checkpointWeek + 1 weeks; w < thisWeek; w += 1 weeks) {
                // Remove CHESS unlocked at the beginning of the next week from total locked amount.
                totalLocked = totalLocked.sub(scheduledUnlock[w]);
                // Calculate supply at the end of the next week.
                nextWeekSupply = nextWeekSupply.sub(totalLocked.mul(1 weeks) / _maxTime);
            }
            totalLocked = totalLocked.sub(scheduledUnlock[thisWeek]);
            return nextWeekSupply.sub(totalLocked.mul(block.timestamp - thisWeek) / _maxTime);
        } else {
            return nextWeekSupply.add(totalLocked.mul(nextWeek - block.timestamp) / _maxTime);
        }
    }

    /// @dev Calculate the total veCHESS amount at a given trading week boundary. The given week
    ///      start timestamp must be later than the last checkpoint. For older weeks,
    ///      derived contract should read from the `veSupplyPerWeek` mapping instead.
    /// @param week Start timestamp of a trading week, must be greater than `checkpointWeek`
    /// @param scheduledUnlock amount of CHESS that will be unlocked in each week
    /// @param checkpointWeek the last checkpoint timestamp
    /// @param nextWeekSupply total veCHESS at the end of the last checkpoint's week
    /// @param totalLocked amount of CHESS locked in the last checkpoint
    /// @return Total veCHESS amount at `week`
    function _veTotalSupplyAtWeek(
        uint256 week,
        mapping(uint256 => uint256) storage scheduledUnlock,
        uint256 checkpointWeek,
        uint256 nextWeekSupply,
        uint256 totalLocked
    ) internal view returns (uint256) {
        if (checkpointWeek + 1 weeks < week) {
            for (uint256 w = checkpointWeek + 1 weeks; w < week; w += 1 weeks) {
                // Remove CHESS unlocked at the beginning of the next week from total locked amount.
                totalLocked = totalLocked.sub(scheduledUnlock[w]);
                // Calculate supply at the end of the next week.
                nextWeekSupply = nextWeekSupply.sub(totalLocked.mul(1 weeks) / _maxTime);
            }
        }
        return nextWeekSupply;
    }
}

// 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/ManagedPausable.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract of an emergency stop mechanism that can be triggered by an authorized account.
 *
 * This module is modified based on Pausable in OpenZeppelin v3.3.0, adding public functions to
 * pause, unpause and manage the pauser role. It is also designed to be used by upgradable
 * contracts, like PausableUpgradable but with compact storage slots and no dependencies.
 */
abstract contract ManagedPausable {
    /**
     * @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);

    event PauserRoleTransferred(address indexed previousPauser, address indexed newPauser);

    uint256 private constant FALSE = 0;
    uint256 private constant TRUE = 1;

    uint256 private _initialized;

    uint256 private _paused;

    address private _pauser;

    function _initializeManagedPausable(address pauser_) internal {
        require(_initialized == FALSE);
        _initialized = TRUE;
        _paused = FALSE;
        _pauser = pauser_;
    }

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

    function pauser() public view returns (address) {
        return _pauser;
    }

    function renouncePauserRole() external onlyPauser {
        emit PauserRoleTransferred(_pauser, address(0));
        _pauser = address(0);
    }

    function transferPauserRole(address newPauser) external onlyPauser {
        require(newPauser != address(0));
        emit PauserRoleTransferred(_pauser, newPauser);
        _pauser = newPauser;
    }

    modifier onlyPauser() {
        require(_pauser == msg.sender, "Pausable: only pauser");
        _;
    }

    /**
     * @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 == FALSE, "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 != FALSE, "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function pause() external onlyPauser whenNotPaused {
        _paused = TRUE;
        emit Paused(msg.sender);
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function unpause() external onlyPauser whenPaused {
        _paused = FALSE;
        emit Unpaused(msg.sender);
    }
}

// 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/ProxyUtility.sol



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

abstract contract ProxyUtility {
    /// @dev Storage slot with the admin of the contract.
    bytes32 private constant _ADMIN_SLOT = bytes32(uint256(keccak256("eip1967.proxy.admin")) - 1);

    /// @dev Revert if the proxy admin is not the caller
    modifier onlyProxyAdmin() {
        bytes32 slot = _ADMIN_SLOT;
        address proxyAdmin;
        assembly {
            proxyAdmin := sload(slot)
        }
        require(msg.sender == proxyAdmin, "Only proxy admin");
        _;
    }
}

// File: contracts/anyswap/AnyCallAppBase.sol



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

interface IAnyCallV6Proxy {
    function executor() external view returns (address);

    function anyCall(
        address to,
        bytes calldata data,
        address fallbackAddress,
        uint256 toChainID,
        uint256 flags
    ) external payable;
}

interface IAnyCallExecutor {
    function context()
        external
        view
        returns (
            address from,
            uint256 fromChainID,
            uint256 nonce
        );
}

interface IAnyFallback {
    function anyFallback(address to, bytes calldata data) external;
}

abstract contract AnyCallAppBase {
    uint256 private constant ANY_CALL_FLAG_PAY_ON_DEST = 0;
    uint256 private constant ANY_CALL_FLAG_PAY_ON_SRC = 2;

    address public immutable anyCallProxy;
    uint256 public immutable anyCallFlag;
    bool public immutable anyCallExecuteFallback;

    constructor(
        address anyCallProxy_,
        bool anyCallPayOnSrc_,
        bool anyCallExecuteFallback_
    ) internal {
        anyCallProxy = anyCallProxy_;
        anyCallFlag = anyCallPayOnSrc_ ? ANY_CALL_FLAG_PAY_ON_SRC : ANY_CALL_FLAG_PAY_ON_DEST;
        anyCallExecuteFallback = anyCallExecuteFallback_;
    }

    modifier onlyExecutor() {
        require(msg.sender == IAnyCallV6Proxy(anyCallProxy).executor());
        _;
    }

    function _anyCall(
        address to,
        uint256 toChainID,
        bytes memory data
    ) internal {
        uint256 callValue = anyCallFlag == ANY_CALL_FLAG_PAY_ON_DEST ? 0 : msg.value;
        address fallbackAddress = anyCallExecuteFallback ? address(this) : address(0);
        IAnyCallV6Proxy(anyCallProxy).anyCall{value: callValue}(
            to,
            data,
            fallbackAddress,
            toChainID,
            anyCallFlag
        );
    }

    function anyExecute(bytes calldata data)
        external
        onlyExecutor
        returns (bool success, bytes memory result)
    {
        (address from, uint256 fromChainID, ) =
            IAnyCallExecutor(IAnyCallV6Proxy(anyCallProxy).executor()).context();
        bytes4 selector = data.length >= 32 ? bytes4(abi.decode(data[0:32], (bytes32))) : bytes4(0);
        if (from == address(this) && selector == IAnyFallback.anyFallback.selector) {
            (address to, bytes memory fallbackData) =
                abi.decode(data[4:data.length], (address, bytes));
            require(_checkAnyFallbackTo(to, fromChainID), "Invalid anyFallback to");
            _anyFallback(fallbackData);
            return (true, "");
        }

        require(
            _checkAnyExecuteFrom(from, fromChainID) && from != address(0),
            "Invalid anyExecute from"
        );
        _anyExecute(fromChainID, data);
        return (true, "");
    }

    function _checkAnyExecuteFrom(address from, uint256 fromChainID)
        internal
        virtual
        returns (bool);

    function _checkAnyFallbackTo(address to, uint256 fromChainID) internal virtual returns (bool);

    function _anyExecute(uint256 fromChainID, bytes calldata data) internal virtual;

    function _anyFallback(bytes memory data) internal virtual;
}

// File: contracts/anyswap/AnyswapChessPool.sol



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

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

import "../governance/ChessRoles.sol";

import "../interfaces/IAnyswapV6ERC20.sol";

contract AnyswapChessPool is IAnyswapV6ERC20, ERC20, ChessRoles, Ownable {
    using SafeERC20 for IERC20;

    address public immutable override underlying;

    constructor(
        string memory name_,
        string memory symbol_,
        address underlying_
    ) public ERC20(name_, symbol_) {
        require(underlying_ != address(0) && underlying_ != address(this));
        underlying = underlying_;
        require(decimals() == ERC20(underlying_).decimals());
    }

    function addMinter(address account) external onlyOwner {
        _addMinter(account);
    }

    function removeMinter(address account) external onlyOwner {
        _removeMinter(account);
    }

    function mint(address to, uint256 amount) external override onlyMinter returns (bool) {
        _mint(to, amount);
        return true;
    }

    function burn(address from, uint256 amount) external override onlyMinter returns (bool) {
        _burn(from, amount);
        return true;
    }

    function deposit() external returns (uint256) {
        uint256 amount = IERC20(underlying).balanceOf(msg.sender);
        IERC20(underlying).safeTransferFrom(msg.sender, address(this), amount);
        _mint(msg.sender, amount);
        return amount;
    }

    function deposit(uint256 amount) external returns (uint256) {
        IERC20(underlying).safeTransferFrom(msg.sender, address(this), amount);
        _mint(msg.sender, amount);
        return amount;
    }

    function deposit(uint256 amount, address to) external returns (uint256) {
        IERC20(underlying).safeTransferFrom(msg.sender, address(this), amount);
        _mint(to, amount);
        return amount;
    }

    function depositVault(uint256 amount, address to) external onlyMinter returns (uint256) {
        _mint(to, amount);
        return amount;
    }

    function withdraw() external returns (uint256) {
        return _withdraw(msg.sender, balanceOf(msg.sender), msg.sender);
    }

    function withdraw(uint256 amount) external returns (uint256) {
        return _withdraw(msg.sender, amount, msg.sender);
    }

    function withdraw(uint256 amount, address to) external returns (uint256) {
        return _withdraw(msg.sender, amount, to);
    }

    function withdrawVault(
        address from,
        uint256 amount,
        address to
    ) external onlyMinter returns (uint256) {
        return _withdraw(from, amount, to);
    }

    function _withdraw(
        address from,
        uint256 amount,
        address to
    ) internal returns (uint256) {
        _burn(from, amount);
        IERC20(underlying).safeTransfer(to, amount);
        return amount;
    }

    function withdrawUnderlying(uint256 amount) external onlyMinter {
        IERC20(underlying).safeTransfer(msg.sender, amount);
    }
}

// File: contracts/interfaces/IAnyswapV6ERC20.sol



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

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

interface IAnyswapV6ERC20 is IERC20 {
    function underlying() external view returns (address);

    function mint(address to, uint256 amount) external returns (bool);

    function burn(address from, uint256 amount) external returns (bool);
}

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



// SPDX-License-Identifier: MIT

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

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

    function __Context_init_unchained() internal initializer {
    }
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
    uint256[50] private __gap;
}

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



// SPDX-License-Identifier: MIT

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

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

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

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

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

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

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

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

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

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

// 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/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/governance/ChessRoles.sol



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

import "@openzeppelin/contracts/utils/EnumerableSet.sol";

abstract contract ChessRoles {
    using EnumerableSet for EnumerableSet.AddressSet;

    EnumerableSet.AddressSet private _minterMembers;

    event MinterAdded(address indexed minter);
    event MinterRemoved(address indexed minter);

    modifier onlyMinter() {
        require(isMinter(msg.sender), "Only minter");
        _;
    }

    function isMinter(address account) public view returns (bool) {
        return _minterMembers.contains(account);
    }

    function getMinterMember(uint256 index) external view returns (address) {
        return _minterMembers.at(index);
    }

    function getMinterCount() external view returns (uint256) {
        return _minterMembers.length();
    }

    function _addMinter(address minter) internal {
        if (_minterMembers.add(minter)) {
            emit MinterAdded(minter);
        }
    }

    function _removeMinter(address minter) internal {
        if (_minterMembers.remove(minter)) {
            emit MinterRemoved(minter);
        }
    }
}

// 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/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));
    }
}