// File: /contracts/Votium.sol



// SPDX-License-Identifier: MIT
// Votium

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/utils/math/Math.sol";

import "./Ownable.sol";

contract Votium is Ownable {
    using SafeERC20 for IERC20;

    /* ========== STATE VARIABLES ========== */

    // relevant time constraints
    uint256 epochDuration = 86400 * 14; // 2 weeks
    uint256 roundDuration = 86400 * 5; // 5 days
    uint256 deadlineDuration = 60 * 60 * 6; // 6 hours

    mapping(address => bool) public tokenAllowed; // token allow list
    mapping(address => bool) public approvedTeam; // for team functions that do not require multi-sig security

    address public feeAddress; // address to receive platform fees
    uint256 public platformFee = 400; // 4%
    uint256 public constant DENOMINATOR = 10000; // denominates weights 10000 = 100%
    address public distributor; // address of distributor contract

    bool public requireAllowlist = true; // begin with erc20 allow list in effect

    struct Incentive {
        address token;
        uint256 amount;
        uint256 maxPerVote;
        uint256 distributed;
        uint256 recycled;
        address depositor;
    }

    mapping(uint256 => address[]) public roundGauges; // round => gauge array
    mapping(uint256 => mapping(address => bool)) public inRoundGauges; // round => gauge => bool
    mapping(uint256 => mapping(address => Incentive[])) public incentives; // round => gauge => incentive array
    mapping(uint256 => mapping(address => uint256)) public votesReceived; // round => gauge => votes

    mapping(address => uint256) public virtualBalance; // token => amount

    uint256 public lastRoundProcessed; // last round that was processed by multi-sig

    mapping(address => uint256) public toTransfer; // token => amount
    address[] public toTransferList; // list of tokens to transfer

    /* ========== CONSTRUCTOR ========== */

    constructor(
        address _approved,
        address _approved2,
        address _feeAddress,
        address _distributor
    ) {
        approvedTeam[_approved] = true;
        approvedTeam[_approved2] = true;
        feeAddress = _feeAddress;
        distributor = _distributor;
        lastRoundProcessed = (block.timestamp / epochDuration) - 1348;
    }

    /* ========== PUBLIC FUNCTIONS ========== */

    function gaugesLength(uint256 _round) public view returns (uint256) {
        return roundGauges[_round].length;
    }

    function incentivesLength(
        uint256 _round,
        address _gauge
    ) public view returns (uint256) {
        return incentives[_round][_gauge].length;
    }

    function currentEpoch() public view returns (uint256) {
        return (block.timestamp / epochDuration) * epochDuration;
    }

    // Display current or next active round
    function activeRound() public view returns (uint256) {
        if (
            block.timestamp < currentEpoch() + roundDuration - deadlineDuration
        ) {
            return currentEpoch() / epochDuration - 1348; // 1348 is the votium genesis round
        } else {
            return currentEpoch() / epochDuration - 1347;
        }
    }

    // Deposit vote incentive for a single gauge in a single round
    function depositIncentive(
        address _token,
        uint256 _amount,
        uint256 _round,
        address _gauge,
        uint256 _maxPerVote
    ) public {
        require(_round >= activeRound(), "!roundEnded");
        require(_round <= activeRound() + 6, "!farFuture");
        uint256 rewardTotal = _takeDeposit(_token, _amount, 1);
        Incentive memory incentive = Incentive({
            token: _token,
            amount: rewardTotal,
            maxPerVote: _maxPerVote,
            distributed: 0,
            recycled: 0,
            depositor: msg.sender
        });
        incentives[_round][_gauge].push(incentive);
        if (!inRoundGauges[_round][_gauge]) {
            roundGauges[_round].push(_gauge);
            inRoundGauges[_round][_gauge] = true;
        }
        emit NewIncentive(
            _token,
            rewardTotal,
            _round,
            _gauge,
            _maxPerVote,
            false
        );
    }

    // evenly split deposit across a single gauge in multiple rounds
    function depositSplitRounds(
        address _token,
        uint256 _amount,
        uint256 _numRounds,
        address _gauge,
        uint256 _maxPerVote
    ) public {
        require(_numRounds < 8, "!farFuture");
        require(_numRounds > 1, "!numRounds");
        uint256 rewardTotal = _takeDeposit(_token, _amount, _numRounds);
        require(rewardTotal / _numRounds > 0, "!rewardTotal");
        uint256 round = activeRound();
        for (uint256 i = 0; i < _numRounds; i++) {
            Incentive memory incentive = Incentive({
                token: _token,
                amount: rewardTotal / _numRounds,
                maxPerVote: _maxPerVote,
                distributed: 0,
                recycled: 0,
                depositor: msg.sender
            });
            incentives[round + i][_gauge].push(incentive);
            if (!inRoundGauges[round + i][_gauge]) {
                roundGauges[round + i].push(_gauge);
                inRoundGauges[round + i][_gauge] = true;
            }
            emit NewIncentive(
                _token,
                rewardTotal / _numRounds,
                round + i,
                _gauge,
                _maxPerVote,
                false
            );
        }
    }

    // evenly split deposit across multiple gauges in a single round
    function depositSplitGauges(
        address _token,
        uint256 _amount,
        uint256 _round,
        address[] calldata _gauges,
        uint256 _maxPerVote
    ) public {
        require(_round >= activeRound(), "!roundEnded");
        require(_round <= activeRound() + 6, "!farFuture");
        require(_gauges.length > 1, "!gauges");
        uint256 rewardTotal = _takeDeposit(_token, _amount, _gauges.length);
        require(rewardTotal / _gauges.length > 0, "!rewardTotal");
        for (uint256 i = 0; i < _gauges.length; i++) {
            Incentive memory incentive = Incentive({
                token: _token,
                amount: rewardTotal / _gauges.length,
                maxPerVote: _maxPerVote,
                distributed: 0,
                recycled: 0,
                depositor: msg.sender
            });
            incentives[_round][_gauges[i]].push(incentive);
            if (!inRoundGauges[_round][_gauges[i]]) {
                roundGauges[_round].push(_gauges[i]);
                inRoundGauges[_round][_gauges[i]] = true;
            }
            emit NewIncentive(
                _token,
                rewardTotal / _gauges.length,
                _round,
                _gauges[i],
                _maxPerVote,
                false
            );
        }
    }

    // evenly split deposit across multiple gauges in multiple rounds
    function depositSplitGaugesRounds(
        address _token,
        uint256 _amount,
        uint256 _numRounds,
        address[] calldata _gauges,
        uint256 _maxPerVote
    ) public {
        require(_numRounds < 8, "!farFuture");
        require(_numRounds > 1, "!numRounds");
        require(_gauges.length > 1, "!gauges");
        uint256 rewardTotal = _takeDeposit(_token, _amount, _numRounds * _gauges.length);
        require(rewardTotal / (_numRounds * _gauges.length) > 0, "!rewardTotal");
        uint256 round = activeRound();
        for (uint256 i = 0; i < _numRounds; i++) {
            for (uint256 j = 0; j < _gauges.length; j++) {
                Incentive memory incentive = Incentive({
                    token: _token,
                    amount: rewardTotal / (_numRounds * _gauges.length),
                    maxPerVote: _maxPerVote,
                    distributed: 0,
                    recycled: 0,
                    depositor: msg.sender
                });
                incentives[round + i][_gauges[j]].push(incentive);
                if (!inRoundGauges[round + i][_gauges[j]]) {
                    roundGauges[round + i].push(_gauges[j]);
                    inRoundGauges[round + i][_gauges[j]] = true;
                }
                emit NewIncentive(
                    _token,
                    rewardTotal / (_numRounds * _gauges.length),
                    round + i,
                    _gauges[j],
                    _maxPerVote,
                    false
                );
            }
        }
    }

    // deposit same token to multiple gauges with different amounts in a single round
    function depositUnevenSplitGauges(
        address _token,
        uint256 _round,
        address[] calldata _gauges,
        uint256[] calldata _amounts,
        uint256 _maxPerVote
    ) public {
        require(_gauges.length == _amounts.length, "!length");
        require(_round >= activeRound(), "!roundEnded");
        require(_round <= activeRound() + 6, "!farFuture");
        uint256 totalDeposit = 0;
        for (uint256 i = 0; i < _gauges.length; i++) {
            require(_amounts[i] > 0, "!amount");
            totalDeposit += _amounts[i];
        }
        _takeDeposit(_token, totalDeposit, 1);
        for (uint256 i = 0; i < _gauges.length; i++) {
            Incentive memory incentive = Incentive({
                token: _token,
                amount: (_amounts[i] * (DENOMINATOR - platformFee)) /
                    DENOMINATOR,
                maxPerVote: _maxPerVote,
                distributed: 0,
                recycled: 0,
                depositor: msg.sender
            });
            incentives[_round][_gauges[i]].push(incentive);
            if (!inRoundGauges[_round][_gauges[i]]) {
                roundGauges[_round].push(_gauges[i]);
                inRoundGauges[_round][_gauges[i]] = true;
            }
            emit NewIncentive(
                _token,
                (_amounts[i] * (DENOMINATOR - platformFee)) / DENOMINATOR,
                _round,
                _gauges[i],
                _maxPerVote,
                false
            );
        }
    }

    function increaseIncentive(
        uint256 _round,
        address _gauge,
        uint256 _incentive,
        uint256 _increase,
        uint256 _maxPerVote
    ) public {
        require(_maxPerVote != incentives[_round][_gauge][_incentive].maxPerVote || _increase > 0, "!change");
        require(_round >= activeRound(), "!deadline");
        require(
            incentives[_round][_gauge][_incentive].depositor == msg.sender,
            "!depositor"
        );
        if(_maxPerVote > 0) {
            require(_maxPerVote >= incentives[_round][_gauge][_incentive].maxPerVote, "!increaseOnly");
            require(incentives[_round][_gauge][_incentive].maxPerVote != 0, "!increaseOnly");
        }
        if(_maxPerVote != incentives[_round][_gauge][_incentive].maxPerVote) {
            incentives[_round][_gauge][_incentive].maxPerVote = _maxPerVote;
        }
        uint256 reward = 0;
        if(_increase > 0) {
            reward = _takeDeposit(
                incentives[_round][_gauge][_incentive].token,
                _increase,
                1
            );
            incentives[_round][_gauge][_incentive].amount += reward;
        }
        emit IncreasedIncentive(
            incentives[_round][_gauge][_incentive].token,
            incentives[_round][_gauge][_incentive].amount,
            reward,
            _round,
            _gauge,
            _maxPerVote
        );
    }

    // function for depositor to withdraw unprocessed incentives
    // this should only happen if a gauge does not exist or is killed before the round ends
    // fees are not returned
    function withdrawUnprocessed(
        uint256 _round,
        address _gauge,
        uint256 _incentive
    ) public {
        require(
            _round <= lastRoundProcessed || _round + 3 < activeRound(),
            "!roundNotProcessed"
        ); // allow 3 rounds for processing before withdraw can be forced
        require(
            incentives[_round][_gauge][_incentive].depositor == msg.sender,
            "!depositor"
        );
        require(
            incentives[_round][_gauge][_incentive].distributed == 0,
            "!distributed"
        );
        require(
            incentives[_round][_gauge][_incentive].recycled == 0,
            "!recycled"
        );
        uint256 amount = incentives[_round][_gauge][_incentive].amount;
        incentives[_round][_gauge][_incentive].amount = 0;
        uint256 adjustedAmount = amount * IERC20(incentives[_round][_gauge][_incentive].token).balanceOf(address(this)) / virtualBalance[incentives[_round][_gauge][_incentive].token];
        amount = amount > adjustedAmount ? adjustedAmount : amount; // use lower amount to avoid over-withdrawal for negative rebase tokens
        IERC20(incentives[_round][_gauge][_incentive].token).safeTransfer(
            msg.sender,
            amount
        );
        virtualBalance[incentives[_round][_gauge][_incentive].token] -= amount;
        emit WithdrawUnprocessed(_round, _gauge, _incentive, amount);
    }

    // function for depositor to recycle unprocessed incentives instead of withdrawing (maybe gauge was not active yet or was killed and revived)
    function recycleUnprocessed(
        uint256 _round,
        address _gauge,
        uint256 _incentive
    ) public {
        require(_round <= lastRoundProcessed, "!roundNotProcessed");
        require(
            incentives[_round][_gauge][_incentive].depositor == msg.sender ||
                msg.sender == owner(),
            "!auth"
        );
        require(
            incentives[_round][_gauge][_incentive].distributed == 0,
            "!distributed"
        );
        require(
            incentives[_round][_gauge][_incentive].recycled == 0,
            "!recycled"
        );
        Incentive memory original = incentives[_round][_gauge][_incentive];
        incentives[_round][_gauge][_incentive].recycled = original.amount;
        _recycleReward(
            original.token,
            original.amount,
            _gauge,
            original.maxPerVote,
            original.depositor
        );
    }

    /* ========== APPROVED TEAM FUNCTIONS ========== */

    // transfer stored rewards to distributor (to rescue tokens sent directly to contract)
    // does not change virtual balance
    function rescueToDistributor(address _token) public onlyTeam {
        uint256 bal = IERC20(_token).balanceOf(address(this)) -
            virtualBalance[_token];
        require(bal > 0, "!balance");
        IERC20(_token).safeTransfer(distributor, bal);
    }

    // allow/deny token
    function allowToken(address _token, bool _allow) public onlyTeam {
        tokenAllowed[_token] = _allow;
        emit TokenAllow(_token, _allow);
    }

    // allow/deny multiple tokens
    function allowTokens(
        address[] memory _tokens,
        bool _allow
    ) public onlyTeam {
        for (uint256 i = 0; i < _tokens.length; i++) {
            tokenAllowed[_tokens[i]] = _allow;
            emit TokenAllow(_tokens[i], _allow);
        }
    }

    /* ========== INTERNAL FUNCTIONS ========== */

    // rewards are recycled automatically if processed without consuming entire reward (maxPerVote)
    function _recycleReward(
        address _token,
        uint256 _amount,
        address _gauge,
        uint256 _maxPerVote,
        address _depositor
    ) internal {
        uint256 _round = activeRound();
        Incentive memory incentive = Incentive({
            token: _token,
            amount: _amount,
            maxPerVote: _maxPerVote,
            distributed: 0,
            recycled: 0,
            depositor: _depositor
        });
        incentives[_round][_gauge].push(incentive);
        emit NewIncentive(_token, _amount, _round, _gauge, _maxPerVote, true);
    }

    // take deposit and send fees to feeAddress, return rewardTotal
    function _takeDeposit(
        address _token,
        uint256 _amount,
        uint256 _split
    ) internal returns (uint256) {
        if (requireAllowlist == true) {
            require(tokenAllowed[_token] == true, "!allowlist");
        }
        require(_amount / _split > 0, "!zero");
        uint256 fee = (_amount * platformFee) / DENOMINATOR;
        uint256 rewardTotal = _amount - fee;
        IERC20(_token).safeTransferFrom(msg.sender, feeAddress, fee);
        IERC20(_token).safeTransferFrom(msg.sender, address(this), rewardTotal);
        virtualBalance[_token] += (rewardTotal / _split) * _split; // prevent rounding errors
        return rewardTotal;
    }

    /* ========== MUTLI-SIG FUNCTIONS ========== */

    // submit vote totals and transfer rewards to distributor
    function endRound(
        uint256 _round,
        address[] memory _gauges,
        uint256[] memory _totals
    ) public onlyOwner {
        require(_gauges.length == _totals.length, "!gauges/totals");
        require(_round < activeRound(), "!activeRound");
        require(_round - 1 == lastRoundProcessed, "!lastRoundProcessed");
        for (uint256 i = 0; i < _gauges.length; i++) {
            require(votesReceived[_round][_gauges[i]] == 0, "!duplicate");
            votesReceived[_round][_gauges[i]] = _totals[i];
            for (
                uint256 n = 0;
                n < incentives[_round][_gauges[i]].length;
                n++
            ) {
                Incentive storage incentive = incentives[_round][_gauges[i]][n];
                uint256 reward;
                if (incentive.maxPerVote > 0) {
                    reward = incentive.maxPerVote * _totals[i];
                    if (reward > incentive.amount) {
                        reward = incentive.amount;
                    } else {
                        // recycle unused reward
                        _recycleReward(
                            incentive.token,
                            incentive.amount - reward,
                            _gauges[i],
                            incentive.maxPerVote,
                            incentive.depositor
                        );
                        incentives[_round][_gauges[i]][n].recycled =
                            incentive.amount -
                            reward;
                    }
                    incentives[_round][_gauges[i]][n].distributed = reward;
                } else {
                    reward = incentive.amount;
                    incentives[_round][_gauges[i]][n].distributed = reward;
                }
                toTransfer[incentive.token] += reward;
                toTransferList.push(incentive.token);
            }
        }
        lastRoundProcessed = _round;
        for (uint256 i = 0; i < toTransferList.length; i++) {
            if(toTransfer[toTransferList[i]] == 0) continue; // skip if already transferred
            IERC20(toTransferList[i]).safeTransfer(
                distributor,
                (toTransfer[toTransferList[i]] *
                    IERC20(toTransferList[i]).balanceOf(address(this))) /
                    virtualBalance[toTransferList[i]]   // account for rebasing tokens
            );
            virtualBalance[toTransferList[i]] -= toTransfer[toTransferList[i]];
            toTransfer[toTransferList[i]] = 0;
        }
        delete toTransferList;
    }

    // toggle whitelist requirement
    function setAllowlistRequired(bool _requireAllowlist) public onlyOwner {
        requireAllowlist = _requireAllowlist;
        emit AllowlistRequirement(_requireAllowlist);
    }

    // update fee address
    function updateFeeAddress(address _feeAddress) public onlyOwner {
        feeAddress = _feeAddress;
    }

    // update fee amount
    function updateFeeAmount(uint256 _feeAmount) public onlyOwner {
        require(_feeAmount < 400, "max fee"); // Max fee 4%
        platformFee = _feeAmount;
        emit UpdatedFee(_feeAmount);
    }

    // add or remove address from team functions
    function modifyTeam(address _member, bool _approval) public onlyOwner {
        approvedTeam[_member] = _approval;
        emit ModifiedTeam(_member, _approval);
    }

    // update token distributor address
    function updateDistributor(address _distributor) public onlyOwner {
        distributor = _distributor;
        emit UpdatedDistributor(distributor);
    }

    // Fallback executable function
    function execute(
        address _to,
        uint256 _value,
        bytes calldata _data
    ) external onlyOwner returns (bool, bytes memory) {
        (bool success, bytes memory result) = _to.call{value: _value}(_data);
        return (success, result);
    }

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

    modifier onlyTeam() {
        require(approvedTeam[msg.sender] == true, "Team only");
        _;
    }

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

    event NewIncentive(
        address _token,
        uint256 _amount,
        uint256 _round,
        address _gauge,
        uint256 _maxPerVote,
        bool _recycled
    );
    event TokenAllow(address _token, bool _allow);
    event AllowlistRequirement(bool _requireAllowlist);
    event UpdatedFee(uint256 _feeAmount);
    event ModifiedTeam(address _member, bool _approval);
    event UpdatedDistributor(address _distributor);
    event WithdrawUnprocessed(
        uint256 _round,
        address _gauge,
        uint256 _incentive,
        uint256 _amount
    );
    event IncreasedIncentive(
        address _token,
        uint256 _total,
        uint256 _increase,
        uint256 _round,
        address _gauge,
        uint256 _maxPerVote
    );
}

// File: /contracts/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/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 = 0xe39b8617D571CEe5e75e1EC6B2bb40DdC8CF6Fa3; // Votium multi-sig address

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


    /**
     * @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 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: @openzeppelin/contracts/utils/math/Math.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/math/Math.sol)

pragma solidity ^0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    enum Rounding {
        Down, // Toward negative infinity
        Up, // Toward infinity
        Zero // Toward zero
    }

    /**
     * @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.
        return (a & b) + (a ^ b) / 2;
    }

    /**
     * @dev Returns the ceiling of the division of two numbers.
     *
     * This differs from standard division with `/` in that it rounds up instead
     * of rounding down.
     */
    function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b - 1) / b can overflow on addition, so we distribute.
        return a == 0 ? 0 : (a - 1) / b + 1;
    }

    /**
     * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
     * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
     * with further edits by Uniswap Labs also under MIT license.
     */
    function mulDiv(uint256 x, uint256 y, uint256 denominator) internal pure returns (uint256 result) {
        unchecked {
            // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
            // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
            // variables such that product = prod1 * 2^256 + prod0.
            uint256 prod0; // Least significant 256 bits of the product
            uint256 prod1; // Most significant 256 bits of the product
            assembly {
                let mm := mulmod(x, y, not(0))
                prod0 := mul(x, y)
                prod1 := sub(sub(mm, prod0), lt(mm, prod0))
            }

            // Handle non-overflow cases, 256 by 256 division.
            if (prod1 == 0) {
                // Solidity will revert if denominator == 0, unlike the div opcode on its own.
                // The surrounding unchecked block does not change this fact.
                // See https://docs.soliditylang.org/en/latest/control-structures.html#checked-or-unchecked-arithmetic.
                return prod0 / denominator;
            }

            // Make sure the result is less than 2^256. Also prevents denominator == 0.
            require(denominator > prod1, "Math: mulDiv overflow");

            ///////////////////////////////////////////////
            // 512 by 256 division.
            ///////////////////////////////////////////////

            // Make division exact by subtracting the remainder from [prod1 prod0].
            uint256 remainder;
            assembly {
                // Compute remainder using mulmod.
                remainder := mulmod(x, y, denominator)

                // Subtract 256 bit number from 512 bit number.
                prod1 := sub(prod1, gt(remainder, prod0))
                prod0 := sub(prod0, remainder)
            }

            // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
            // See https://cs.stackexchange.com/q/138556/92363.

            // Does not overflow because the denominator cannot be zero at this stage in the function.
            uint256 twos = denominator & (~denominator + 1);
            assembly {
                // Divide denominator by twos.
                denominator := div(denominator, twos)

                // Divide [prod1 prod0] by twos.
                prod0 := div(prod0, twos)

                // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                twos := add(div(sub(0, twos), twos), 1)
            }

            // Shift in bits from prod1 into prod0.
            prod0 |= prod1 * twos;

            // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
            // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
            // four bits. That is, denominator * inv = 1 mod 2^4.
            uint256 inverse = (3 * denominator) ^ 2;

            // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
            // in modular arithmetic, doubling the correct bits in each step.
            inverse *= 2 - denominator * inverse; // inverse mod 2^8
            inverse *= 2 - denominator * inverse; // inverse mod 2^16
            inverse *= 2 - denominator * inverse; // inverse mod 2^32
            inverse *= 2 - denominator * inverse; // inverse mod 2^64
            inverse *= 2 - denominator * inverse; // inverse mod 2^128
            inverse *= 2 - denominator * inverse; // inverse mod 2^256

            // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
            // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
            // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
            // is no longer required.
            result = prod0 * inverse;
            return result;
        }
    }

    /**
     * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
     */
    function mulDiv(uint256 x, uint256 y, uint256 denominator, Rounding rounding) internal pure returns (uint256) {
        uint256 result = mulDiv(x, y, denominator);
        if (rounding == Rounding.Up && mulmod(x, y, denominator) > 0) {
            result += 1;
        }
        return result;
    }

    /**
     * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded down.
     *
     * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
     */
    function sqrt(uint256 a) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }

        // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
        //
        // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
        // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
        //
        // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
        // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
        // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
        //
        // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
        uint256 result = 1 << (log2(a) >> 1);

        // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
        // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
        // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
        // into the expected uint128 result.
        unchecked {
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            return min(result, a / result);
        }
    }

    /**
     * @notice Calculates sqrt(a), following the selected rounding direction.
     */
    function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = sqrt(a);
            return result + (rounding == Rounding.Up && result * result < a ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 2, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 128;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 64;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 32;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 16;
            }
            if (value >> 8 > 0) {
                value >>= 8;
                result += 8;
            }
            if (value >> 4 > 0) {
                value >>= 4;
                result += 4;
            }
            if (value >> 2 > 0) {
                value >>= 2;
                result += 2;
            }
            if (value >> 1 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log2(value);
            return result + (rounding == Rounding.Up && 1 << result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 10, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >= 10 ** 64) {
                value /= 10 ** 64;
                result += 64;
            }
            if (value >= 10 ** 32) {
                value /= 10 ** 32;
                result += 32;
            }
            if (value >= 10 ** 16) {
                value /= 10 ** 16;
                result += 16;
            }
            if (value >= 10 ** 8) {
                value /= 10 ** 8;
                result += 8;
            }
            if (value >= 10 ** 4) {
                value /= 10 ** 4;
                result += 4;
            }
            if (value >= 10 ** 2) {
                value /= 10 ** 2;
                result += 2;
            }
            if (value >= 10 ** 1) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log10(value);
            return result + (rounding == Rounding.Up && 10 ** result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 256, rounded down, of a positive value.
     * Returns 0 if given 0.
     *
     * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
     */
    function log256(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 16;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 8;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 4;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 2;
            }
            if (value >> 8 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 256, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log256(value);
            return result + (rounding == Rounding.Up && 1 << (result << 3) < value ? 1 : 0);
        }
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^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 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) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     *
     * Furthermore, `isContract` will also return true if the target contract within
     * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
     * which only has an effect at the end of a transaction.
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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://consensys.net/diligence/blog/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/v0.8.0/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");

        (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 functionCallWithValue(target, data, 0, "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");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // 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
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/IERC20Permit.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 Address for address;

    /**
     * @dev Transfer `value` amount of `token` from the calling contract to `to`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    /**
     * @dev Transfer `value` amount of `token` from `from` to `to`, spending the approval given by `from` to the
     * calling contract. If `token` returns no value, non-reverting calls are assumed to be successful.
     */
    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'
        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));
    }

    /**
     * @dev Increase the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 oldAllowance = token.allowance(address(this), spender);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, oldAllowance + value));
    }

    /**
     * @dev Decrease the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, oldAllowance - value));
        }
    }

    /**
     * @dev Set the calling contract's allowance toward `spender` to `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful. Compatible with tokens that require the approval to be set to
     * 0 before setting it to a non-zero value.
     */
    function forceApprove(IERC20 token, address spender, uint256 value) internal {
        bytes memory approvalCall = abi.encodeWithSelector(token.approve.selector, spender, value);

        if (!_callOptionalReturnBool(token, approvalCall)) {
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, 0));
            _callOptionalReturn(token, approvalCall);
        }
    }

    /**
     * @dev Use a ERC-2612 signature to set the `owner` approval toward `spender` on `token`.
     * Revert on invalid signature.
     */
    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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");
        require(returndata.length == 0 || abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
    }

    /**
     * @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).
     *
     * This is a variant of {_callOptionalReturn} that silents catches all reverts and returns a bool instead.
     */
    function _callOptionalReturnBool(IERC20 token, bytes memory data) private returns (bool) {
        // 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 cannot use {Address-functionCall} here since this should return false
        // and not revert is the subcall reverts.

        (bool success, bytes memory returndata) = address(token).call(data);
        return
            success && (returndata.length == 0 || abi.decode(returndata, (bool))) && Address.isContract(address(token));
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/extensions/IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

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