// File: contracts/YENCrypto.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

import "./Math.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/interfaces/IERC165.sol";
import "./abdk-libraries-solidity/ABDKMath64x64.sol";
import "./interfaces/IStakingToken.sol";
import "./interfaces/IRankedMintingToken.sol";
import "./interfaces/IBurnableToken.sol";
import "./interfaces/IBurnRedeemable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

contract YENCrypto is Context, IRankedMintingToken, IStakingToken, IBurnableToken, Ownable, ERC20("YEN Crypto", "YEN") {
    using Math for uint256;
    using ABDKMath64x64 for int128;
    using ABDKMath64x64 for uint256;
    using SafeERC20 for IERC20;

    // INTERNAL TYPE TO DESCRIBE A YEN MINT INFO
    struct MintInfo {
        address user;
        uint256 term;
        uint256 maturityTs;
        uint256 rank;
        uint256 amplifier;
        uint256 eaaRate;
    }

    // INTERNAL TYPE TO DESCRIBE A YEN STAKE
    struct StakeInfo {
        uint256 term;
        uint256 maturityTs;
        uint256 amount;
        uint256 apy;
    }

    uint256 public startTime;
    address public FundAddress;
    // PUBLIC CONSTANTS

    uint256 public constant SECONDS_IN_DAY = 3_600 * 24;
    uint256 public constant DAYS_IN_YEAR = 365;

    uint256 public constant GENESIS_RANK = 1;

    uint256 public constant MIN_TERM = 1 * SECONDS_IN_DAY - 1;
    uint256 public constant MAX_TERM_START = 100 * SECONDS_IN_DAY;
    uint256 public constant MAX_TERM_END = 1_000 * SECONDS_IN_DAY;
    uint256 public constant TERM_AMPLIFIER = 15;
    uint256 public constant TERM_AMPLIFIER_THRESHOLD = 5_000;
    uint256 public constant REWARD_AMPLIFIER_START = 100;
    uint256 public constant REWARD_AMPLIFIER_END = 1;
    uint256 public constant EAA_PM_START = 10;
    uint256 public constant EAA_PM_STEP = 1;
    uint256 public constant EAA_RANK_STEP = 100_000;
    uint256 public constant WITHDRAWAL_WINDOW_DAYS = 7;
    uint256 public constant MAX_PENALTY_PCT = 99;

    uint256 public constant YEN_MIN_STAKE = 0;

    uint256 public constant YEN_MIN_BURN = 0;

    uint256 public constant YEN_APY_START = 20;
    uint256 public constant YEN_APY_DAYS_STEP = 90;
    uint256 public constant YEN_APY_END = 2;

    // PUBLIC STATE, READABLE VIA NAMESAKE GETTERS

    uint256 public immutable genesisTs;
    uint256 public globalRank = GENESIS_RANK;
    uint256 public activeMinters;
    uint256 public totalTransactions;
    // user address => YEN mint info
    mapping(address => MintInfo) public userMints;
    // user address => YEN stake info
    mapping(address => StakeInfo) public userStakes;
    // user address => YEN burn amount
    mapping(address => uint256) public userBurns;

    // CONSTRUCTOR
    constructor(uint256 _startTime, address _FundAddress) {
        genesisTs = block.timestamp;
        startTime = _startTime;
        FundAddress = _FundAddress;
    }

    modifier chargeFee(){
        require(msg.value >= 0.005 ether, "insufficient fee");
        payable(FundAddress).transfer(msg.value);
        _;
    }

    // PRIVATE METHODS

    /**
     * @dev calculates current MaxTerm based on Global Rank
     *      (if Global Rank crosses over TERM_AMPLIFIER_THRESHOLD)
     */
    function _calculateMaxTerm() private view returns (uint256) {
        if (globalRank > TERM_AMPLIFIER_THRESHOLD) {
            uint256 delta = globalRank.fromUInt().log_2().mul(TERM_AMPLIFIER.fromUInt()).toUInt();
            uint256 newMax = MAX_TERM_START + delta * SECONDS_IN_DAY;
            return Math.min(newMax, MAX_TERM_END);
        }
        return MAX_TERM_START;
    }

    /**
     * @dev calculates Withdrawal Penalty depending on lateness
     */
    function _penalty(uint256 secsLate) private pure returns (uint256) {
        // =MIN(2^(daysLate+3)/window-1,99)
        uint256 daysLate = secsLate / SECONDS_IN_DAY;
        if (daysLate > WITHDRAWAL_WINDOW_DAYS - 1) return MAX_PENALTY_PCT;
        uint256 penalty = (uint256(1) << (daysLate + 3)) / WITHDRAWAL_WINDOW_DAYS - 1;
        return Math.min(penalty, MAX_PENALTY_PCT);
    }

    /**
     * @dev calculates net Mint Reward (adjusted for Penalty)
     */
    function _calculateMintReward(
        uint256 cRank,
        uint256 term,
        uint256 maturityTs,
        uint256 amplifier,
        uint256 eeaRate
    ) private view returns (uint256) {
        uint256 secsLate = block.timestamp - maturityTs;
        uint256 penalty = _penalty(secsLate);
        uint256 rankDelta = Math.max(globalRank - cRank, 2);
        uint256 EAA = (1_000 + eeaRate);
        uint256 reward = getGrossReward(rankDelta, amplifier, term, EAA);
        return (reward * (100 - penalty)) / 100;
    }

    /**
     * @dev cleans up User Mint storage (gets some Gas credit;))
     */
    function _cleanUpUserMint() private {
        delete userMints[_msgSender()];
        activeMinters--;
    }

    /**
     * @dev calculates Reward Amplifier
     */
    function _calculateRewardAmplifier() private view returns (uint256) {
        uint256 amplifierDecrease = (block.timestamp - genesisTs) / SECONDS_IN_DAY;
        if (amplifierDecrease < REWARD_AMPLIFIER_START) {
            return Math.max(REWARD_AMPLIFIER_START - amplifierDecrease, REWARD_AMPLIFIER_END);
        } else {
            return REWARD_AMPLIFIER_END;
        }
    }

    /**
     * @dev calculates Early Adopter Amplifier Rate (in 1/000ths)
     *      actual EAA is (1_000 + EAAR) / 1_000
     */
    function _calculateEAARate() private view returns (uint256) {
        uint256 decrease = (EAA_PM_STEP * globalRank) / EAA_RANK_STEP;
        if (decrease > EAA_PM_START) return 0;
        return EAA_PM_START - decrease;
    }

    /**
     * @dev calculates APY (in %)
     */
    function _calculateAPY() private view returns (uint256) {
        uint256 decrease = (block.timestamp - genesisTs) / (SECONDS_IN_DAY * YEN_APY_DAYS_STEP);
        if (YEN_APY_START - YEN_APY_END < decrease) return YEN_APY_END;
        return YEN_APY_START - decrease;
    }


    // PUBLIC CONVENIENCE GETTERS

    /**
     * @dev calculates gross Mint Reward
     */
    function getGrossReward(
        uint256 rankDelta,
        uint256 amplifier,
        uint256 term,
        uint256 eaa
    ) public pure returns (uint256) {
        int128 log128 = rankDelta.fromUInt().log_2();
        int128 reward128 = log128.mul(amplifier.fromUInt()).mul(term.fromUInt()).mul(eaa.fromUInt());
        return reward128.div(uint256(1_000).fromUInt()).toUInt();
    }

    /**
     * @dev returns User Mint object associated with User account address
     */
    function getUserMint() external view returns (MintInfo memory) {
        return userMints[_msgSender()];
    }

    /**
     * @dev returns YEN Stake object associated with User account address
     */
    function getUserStake() external view returns (StakeInfo memory) {
        return userStakes[_msgSender()];
    }

    /**
     * @dev returns current AMP
     */
    function getCurrentAMP() external view returns (uint256) {
        return _calculateRewardAmplifier();
    }

    /**
     * @dev returns current EAA Rate
     */
    function getCurrentEAAR() external view returns (uint256) {
        return _calculateEAARate();
    }

    /**
     * @dev returns current APY
     */
    function getCurrentAPY() external view returns (uint256) {
        return _calculateAPY();
    }

    /**
     * @dev returns current MaxTerm
     */
    function getCurrentMaxTerm() external view returns (uint256) {
        return _calculateMaxTerm();
    }

    // PUBLIC STATE-CHANGING METHODS

    /**
     * @dev accepts User cRank claim provided all checks pass (incl. no current claim exists)
     */
    function claimRank(uint256 term) payable external chargeFee{
        uint256 termSec = term * SECONDS_IN_DAY;
        require(termSec > MIN_TERM, "CRank: Term less than min");
        require(termSec < _calculateMaxTerm() + 1, "CRank: Term more than current max term");
        require(userMints[_msgSender()].rank == 0, "CRank: Mint already in progress");

        // create and store new MintInfo
        MintInfo memory mintInfo = MintInfo({
        user : _msgSender(),
        term : term,
        maturityTs : block.timestamp + termSec,
        rank : globalRank,
        amplifier : _calculateRewardAmplifier(),
        eaaRate : _calculateEAARate()
        });
        userMints[_msgSender()] = mintInfo;
        activeMinters++;
        totalTransactions++;
        emit RankClaimed(_msgSender(), term, globalRank++);
    }

    /**
     * @dev ends minting upon maturity (and within permitted Withdrawal Time Window), gets minted YEN
     */
    function claimMintReward()  external {
        MintInfo memory mintInfo = userMints[_msgSender()];
        require(mintInfo.rank > 0, "CRank: No mint exists");
        require(block.timestamp > mintInfo.maturityTs, "CRank: Mint maturity not reached");

        // calculate reward and mint tokens
        uint256 rewardAmount = _calculateMintReward(
            mintInfo.rank,
            mintInfo.term,
            mintInfo.maturityTs,
            mintInfo.amplifier,
            mintInfo.eaaRate
        ) * 1 ether;
        _mint(_msgSender(), rewardAmount);

        _cleanUpUserMint();
        totalTransactions++;
        emit MintClaimed(_msgSender(), rewardAmount);
    }

    /**
     * @dev  ends minting upon maturity (and within permitted Withdrawal time Window)
     *       mints YEN coins and splits them between User and designated other address
     */
    function claimMintRewardAndShare(address other, uint256 pct) external{
        MintInfo memory mintInfo = userMints[_msgSender()];
        require(other != address(0), "CRank: Cannot share with zero address");
        require(pct > 0, "CRank: Cannot share zero percent");
        require(pct < 101, "CRank: Cannot share 100+ percent");
        require(mintInfo.rank > 0, "CRank: No mint exists");
        require(block.timestamp > mintInfo.maturityTs, "CRank: Mint maturity not reached");

        // calculate reward
        uint256 rewardAmount = _calculateMintReward(
            mintInfo.rank,
            mintInfo.term,
            mintInfo.maturityTs,
            mintInfo.amplifier,
            mintInfo.eaaRate
        ) * 1 ether;
        uint256 sharedReward = (rewardAmount * pct) / 100;
        uint256 ownReward = rewardAmount - sharedReward;

        // mint reward tokens
        _mint(_msgSender(), ownReward);
        _mint(other, sharedReward);

        _cleanUpUserMint();
        totalTransactions++;
        emit MintClaimed(_msgSender(), rewardAmount);
    }


    /**
     * @dev burns YEN tokens and creates Proof-Of-Burn record to be used by connected DeFi services
     */
    function burn(address user, uint256 amount) public {
        require(amount > YEN_MIN_BURN, "Burn: Below min limit");
        require(
            IERC165(_msgSender()).supportsInterface(type(IBurnRedeemable).interfaceId),
            "Burn: not a supported contract"
        );

        _spendAllowance(user, _msgSender(), amount);
        _burn(user, amount);
        userBurns[user] += amount;
        IBurnRedeemable(_msgSender()).onTokenBurned(user, amount);
        totalTransactions++;
    }

    function updateStartTime(uint256 _startTime) external onlyOwner {
        startTime = _startTime;
    }

    //in case of mis-transfer tokens
    function recovery(address erc20Token, uint256 amount) external onlyOwner {
        require(erc20Token != address(this), "can not transfer yen");

        if (erc20Token != address(0)) {
            IERC20(erc20Token).safeTransfer(msg.sender, amount);
        } else {
            Address.sendValue(payable(msg.sender), amount);
        }
    }
}

// File: contracts/Math.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

import "./abdk-libraries-solidity/ABDKMath64x64.sol";

library Math {
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a > b) return b;
        return a;
    }

    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a > b) return a;
        return b;
    }

    function logX64(uint256 x) internal pure returns (int128) {
        return ABDKMath64x64.log_2(ABDKMath64x64.fromUInt(x));
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.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 Contracts guidelines: functions revert
 * instead 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, IERC20Metadata {
    mapping(address => uint256) private _balances;

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

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

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override 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 this function is
     * overridden;
     *
     * 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 override returns (uint8) {
        return 18;
    }

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

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, 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}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, 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}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        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) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, spender) + 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) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * This 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:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
        }
        _balances[to] += amount;

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, 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:
     *
     * - `account` 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 += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(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);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(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 Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @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 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 {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been 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 _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// File: @openzeppelin/contracts/interfaces/IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC165.sol)

pragma solidity ^0.8.0;

import "../utils/introspection/IERC165.sol";

// File: contracts/abdk-libraries-solidity/ABDKMath64x64.sol



// SPDX-License-Identifier: BSD-4-Clause
/*
 * ABDK Math 64.64 Smart Contract Library.  Copyright © 2019 by ABDK Consulting.
 * Author: Mikhail Vladimirov <mikhail.vladimirov@gmail.com>
 */
pragma solidity ^0.8.0;

/**
 * Smart contract library of mathematical functions operating with signed
 * 64.64-bit fixed point numbers.  Signed 64.64-bit fixed point number is
 * basically a simple fraction whose numerator is signed 128-bit integer and
 * denominator is 2^64.  As long as denominator is always the same, there is no
 * need to store it, thus in Solidity signed 64.64-bit fixed point numbers are
 * represented by int128 type holding only the numerator.
 */
library ABDKMath64x64 {
    /*
     * Minimum value signed 64.64-bit fixed point number may have.
     */
    int128 private constant MIN_64x64 = -0x80000000000000000000000000000000;

    /*
     * Maximum value signed 64.64-bit fixed point number may have.
     */
    int128 private constant MAX_64x64 = 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF;

    /**
     * Convert signed 256-bit integer number into signed 64.64-bit fixed point
     * number.  Revert on overflow.
     *
     * @param x signed 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
    function fromInt (int256 x) internal pure returns (int128) {
    unchecked {
        require (x >= -0x8000000000000000 && x <= 0x7FFFFFFFFFFFFFFF);
        return int128 (x << 64);
    }
    }

    /**
     * Convert signed 64.64 fixed point number into signed 64-bit integer number
     * rounding down.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64-bit integer number
   */
    function toInt (int128 x) internal pure returns (int64) {
    unchecked {
        return int64 (x >> 64);
    }
    }

    /**
     * Convert unsigned 256-bit integer number into signed 64.64-bit fixed point
     * number.  Revert on overflow.
     *
     * @param x unsigned 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
    function fromUInt (uint256 x) internal pure returns (int128) {
    unchecked {
        require (x <= 0x7FFFFFFFFFFFFFFF);
        return int128 (int256 (x << 64));
    }
    }

    /**
     * Convert signed 64.64 fixed point number into unsigned 64-bit integer
     * number rounding down.  Revert on underflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @return unsigned 64-bit integer number
   */
    function toUInt (int128 x) internal pure returns (uint64) {
    unchecked {
        require (x >= 0);
        return uint64 (uint128 (x >> 64));
    }
    }

    /**
     * Convert signed 128.128 fixed point number into signed 64.64-bit fixed point
     * number rounding down.  Revert on overflow.
     *
     * @param x signed 128.128-bin fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function from128x128 (int256 x) internal pure returns (int128) {
    unchecked {
        int256 result = x >> 64;
        require (result >= MIN_64x64 && result <= MAX_64x64);
        return int128 (result);
    }
    }

    /**
     * Convert signed 64.64 fixed point number into signed 128.128 fixed point
     * number.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 128.128 fixed point number
   */
    function to128x128 (int128 x) internal pure returns (int256) {
    unchecked {
        return int256 (x) << 64;
    }
    }

    /**
     * Calculate x + y.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function add (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
        int256 result = int256(x) + y;
        require (result >= MIN_64x64 && result <= MAX_64x64);
        return int128 (result);
    }
    }

    /**
     * Calculate x - y.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function sub (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
        int256 result = int256(x) - y;
        require (result >= MIN_64x64 && result <= MAX_64x64);
        return int128 (result);
    }
    }

    /**
     * Calculate x * y rounding down.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function mul (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
        int256 result = int256(x) * y >> 64;
        require (result >= MIN_64x64 && result <= MAX_64x64);
        return int128 (result);
    }
    }

    /**
     * Calculate x * y rounding towards zero, where x is signed 64.64 fixed point
     * number and y is signed 256-bit integer number.  Revert on overflow.
     *
     * @param x signed 64.64 fixed point number
   * @param y signed 256-bit integer number
   * @return signed 256-bit integer number
   */
    function muli (int128 x, int256 y) internal pure returns (int256) {
    unchecked {
        if (x == MIN_64x64) {
            require (y >= -0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF &&
            y <= 0x1000000000000000000000000000000000000000000000000);
            return -y << 63;
        } else {
            bool negativeResult = false;
            if (x < 0) {
                x = -x;
                negativeResult = true;
            }
            if (y < 0) {
                y = -y; // We rely on overflow behavior here
                negativeResult = !negativeResult;
            }
            uint256 absoluteResult = mulu (x, uint256 (y));
            if (negativeResult) {
                require (absoluteResult <=
                    0x8000000000000000000000000000000000000000000000000000000000000000);
                return -int256 (absoluteResult); // We rely on overflow behavior here
            } else {
                require (absoluteResult <=
                    0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
                return int256 (absoluteResult);
            }
        }
    }
    }

    /**
     * Calculate x * y rounding down, where x is signed 64.64 fixed point number
     * and y is unsigned 256-bit integer number.  Revert on overflow.
     *
     * @param x signed 64.64 fixed point number
   * @param y unsigned 256-bit integer number
   * @return unsigned 256-bit integer number
   */
    function mulu (int128 x, uint256 y) internal pure returns (uint256) {
    unchecked {
        if (y == 0) return 0;

        require (x >= 0);

        uint256 lo = (uint256 (int256 (x)) * (y & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)) >> 64;
        uint256 hi = uint256 (int256 (x)) * (y >> 128);

        require (hi <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
        hi <<= 64;

        require (hi <=
            0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF - lo);
        return hi + lo;
    }
    }

    /**
     * Calculate x / y rounding towards zero.  Revert on overflow or when y is
     * zero.
     *
     * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function div (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
        require (y != 0);
        int256 result = (int256 (x) << 64) / y;
        require (result >= MIN_64x64 && result <= MAX_64x64);
        return int128 (result);
    }
    }

    /**
     * Calculate x / y rounding towards zero, where x and y are signed 256-bit
     * integer numbers.  Revert on overflow or when y is zero.
     *
     * @param x signed 256-bit integer number
   * @param y signed 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
    function divi (int256 x, int256 y) internal pure returns (int128) {
    unchecked {
        require (y != 0);

        bool negativeResult = false;
        if (x < 0) {
            x = -x; // We rely on overflow behavior here
            negativeResult = true;
        }
        if (y < 0) {
            y = -y; // We rely on overflow behavior here
            negativeResult = !negativeResult;
        }
        uint128 absoluteResult = divuu (uint256 (x), uint256 (y));
        if (negativeResult) {
            require (absoluteResult <= 0x80000000000000000000000000000000);
            return -int128 (absoluteResult); // We rely on overflow behavior here
        } else {
            require (absoluteResult <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
            return int128 (absoluteResult); // We rely on overflow behavior here
        }
    }
    }

    /**
     * Calculate x / y rounding towards zero, where x and y are unsigned 256-bit
     * integer numbers.  Revert on overflow or when y is zero.
     *
     * @param x unsigned 256-bit integer number
   * @param y unsigned 256-bit integer number
   * @return signed 64.64-bit fixed point number
   */
    function divu (uint256 x, uint256 y) internal pure returns (int128) {
    unchecked {
        require (y != 0);
        uint128 result = divuu (x, y);
        require (result <= uint128 (MAX_64x64));
        return int128 (result);
    }
    }

    /**
     * Calculate -x.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function neg (int128 x) internal pure returns (int128) {
    unchecked {
        require (x != MIN_64x64);
        return -x;
    }
    }

    /**
     * Calculate |x|.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function abs (int128 x) internal pure returns (int128) {
    unchecked {
        require (x != MIN_64x64);
        return x < 0 ? -x : x;
    }
    }

    /**
     * Calculate 1 / x rounding towards zero.  Revert on overflow or when x is
     * zero.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function inv (int128 x) internal pure returns (int128) {
    unchecked {
        require (x != 0);
        int256 result = int256 (0x100000000000000000000000000000000) / x;
        require (result >= MIN_64x64 && result <= MAX_64x64);
        return int128 (result);
    }
    }

    /**
     * Calculate arithmetics average of x and y, i.e. (x + y) / 2 rounding down.
     *
     * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function avg (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
        return int128 ((int256 (x) + int256 (y)) >> 1);
    }
    }

    /**
     * Calculate geometric average of x and y, i.e. sqrt (x * y) rounding down.
     * Revert on overflow or in case x * y is negative.
     *
     * @param x signed 64.64-bit fixed point number
   * @param y signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function gavg (int128 x, int128 y) internal pure returns (int128) {
    unchecked {
        int256 m = int256 (x) * int256 (y);
        require (m >= 0);
        require (m <
            0x4000000000000000000000000000000000000000000000000000000000000000);
        return int128 (sqrtu (uint256 (m)));
    }
    }

    /**
     * Calculate x^y assuming 0^0 is 1, where x is signed 64.64 fixed point number
     * and y is unsigned 256-bit integer number.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @param y uint256 value
   * @return signed 64.64-bit fixed point number
   */
    function pow (int128 x, uint256 y) internal pure returns (int128) {
    unchecked {
        bool negative = x < 0 && y & 1 == 1;

        uint256 absX = uint128 (x < 0 ? -x : x);
        uint256 absResult;
        absResult = 0x100000000000000000000000000000000;

        if (absX <= 0x10000000000000000) {
            absX <<= 63;
            while (y != 0) {
                if (y & 0x1 != 0) {
                    absResult = absResult * absX >> 127;
                }
                absX = absX * absX >> 127;

                if (y & 0x2 != 0) {
                    absResult = absResult * absX >> 127;
                }
                absX = absX * absX >> 127;

                if (y & 0x4 != 0) {
                    absResult = absResult * absX >> 127;
                }
                absX = absX * absX >> 127;

                if (y & 0x8 != 0) {
                    absResult = absResult * absX >> 127;
                }
                absX = absX * absX >> 127;

                y >>= 4;
            }

            absResult >>= 64;
        } else {
            uint256 absXShift = 63;
            if (absX < 0x1000000000000000000000000) { absX <<= 32; absXShift -= 32; }
            if (absX < 0x10000000000000000000000000000) { absX <<= 16; absXShift -= 16; }
            if (absX < 0x1000000000000000000000000000000) { absX <<= 8; absXShift -= 8; }
            if (absX < 0x10000000000000000000000000000000) { absX <<= 4; absXShift -= 4; }
            if (absX < 0x40000000000000000000000000000000) { absX <<= 2; absXShift -= 2; }
            if (absX < 0x80000000000000000000000000000000) { absX <<= 1; absXShift -= 1; }

            uint256 resultShift = 0;
            while (y != 0) {
                require (absXShift < 64);

                if (y & 0x1 != 0) {
                    absResult = absResult * absX >> 127;
                    resultShift += absXShift;
                    if (absResult > 0x100000000000000000000000000000000) {
                        absResult >>= 1;
                        resultShift += 1;
                    }
                }
                absX = absX * absX >> 127;
                absXShift <<= 1;
                if (absX >= 0x100000000000000000000000000000000) {
                    absX >>= 1;
                    absXShift += 1;
                }

                y >>= 1;
            }

            require (resultShift < 64);
            absResult >>= 64 - resultShift;
        }
        int256 result = negative ? -int256 (absResult) : int256 (absResult);
        require (result >= MIN_64x64 && result <= MAX_64x64);
        return int128 (result);
    }
    }

    /**
     * Calculate sqrt (x) rounding down.  Revert if x < 0.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function sqrt (int128 x) internal pure returns (int128) {
    unchecked {
        require (x >= 0);
        return int128 (sqrtu (uint256 (int256 (x)) << 64));
    }
    }

    /**
     * Calculate binary logarithm of x.  Revert if x <= 0.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function log_2 (int128 x) internal pure returns (int128) {
    unchecked {
        require (x > 0);

        int256 msb = 0;
        int256 xc = x;
        if (xc >= 0x10000000000000000) { xc >>= 64; msb += 64; }
        if (xc >= 0x100000000) { xc >>= 32; msb += 32; }
        if (xc >= 0x10000) { xc >>= 16; msb += 16; }
        if (xc >= 0x100) { xc >>= 8; msb += 8; }
        if (xc >= 0x10) { xc >>= 4; msb += 4; }
        if (xc >= 0x4) { xc >>= 2; msb += 2; }
        if (xc >= 0x2) msb += 1;  // No need to shift xc anymore

        int256 result = msb - 64 << 64;
        uint256 ux = uint256 (int256 (x)) << uint256 (127 - msb);
        for (int256 bit = 0x8000000000000000; bit > 0; bit >>= 1) {
            ux *= ux;
            uint256 b = ux >> 255;
            ux >>= 127 + b;
            result += bit * int256 (b);
        }

        return int128 (result);
    }
    }

    /**
     * Calculate natural logarithm of x.  Revert if x <= 0.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function ln (int128 x) internal pure returns (int128) {
    unchecked {
        require (x > 0);

        return int128 (int256 (
                uint256 (int256 (log_2 (x))) * 0xB17217F7D1CF79ABC9E3B39803F2F6AF >> 128));
    }
    }

    /**
     * Calculate binary exponent of x.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function exp_2 (int128 x) internal pure returns (int128) {
    unchecked {
        require (x < 0x400000000000000000); // Overflow

        if (x < -0x400000000000000000) return 0; // Underflow

        uint256 result = 0x80000000000000000000000000000000;

        if (x & 0x8000000000000000 > 0)
            result = result * 0x16A09E667F3BCC908B2FB1366EA957D3E >> 128;
        if (x & 0x4000000000000000 > 0)
            result = result * 0x1306FE0A31B7152DE8D5A46305C85EDEC >> 128;
        if (x & 0x2000000000000000 > 0)
            result = result * 0x1172B83C7D517ADCDF7C8C50EB14A791F >> 128;
        if (x & 0x1000000000000000 > 0)
            result = result * 0x10B5586CF9890F6298B92B71842A98363 >> 128;
        if (x & 0x800000000000000 > 0)
            result = result * 0x1059B0D31585743AE7C548EB68CA417FD >> 128;
        if (x & 0x400000000000000 > 0)
            result = result * 0x102C9A3E778060EE6F7CACA4F7A29BDE8 >> 128;
        if (x & 0x200000000000000 > 0)
            result = result * 0x10163DA9FB33356D84A66AE336DCDFA3F >> 128;
        if (x & 0x100000000000000 > 0)
            result = result * 0x100B1AFA5ABCBED6129AB13EC11DC9543 >> 128;
        if (x & 0x80000000000000 > 0)
            result = result * 0x10058C86DA1C09EA1FF19D294CF2F679B >> 128;
        if (x & 0x40000000000000 > 0)
            result = result * 0x1002C605E2E8CEC506D21BFC89A23A00F >> 128;
        if (x & 0x20000000000000 > 0)
            result = result * 0x100162F3904051FA128BCA9C55C31E5DF >> 128;
        if (x & 0x10000000000000 > 0)
            result = result * 0x1000B175EFFDC76BA38E31671CA939725 >> 128;
        if (x & 0x8000000000000 > 0)
            result = result * 0x100058BA01FB9F96D6CACD4B180917C3D >> 128;
        if (x & 0x4000000000000 > 0)
            result = result * 0x10002C5CC37DA9491D0985C348C68E7B3 >> 128;
        if (x & 0x2000000000000 > 0)
            result = result * 0x1000162E525EE054754457D5995292026 >> 128;
        if (x & 0x1000000000000 > 0)
            result = result * 0x10000B17255775C040618BF4A4ADE83FC >> 128;
        if (x & 0x800000000000 > 0)
            result = result * 0x1000058B91B5BC9AE2EED81E9B7D4CFAB >> 128;
        if (x & 0x400000000000 > 0)
            result = result * 0x100002C5C89D5EC6CA4D7C8ACC017B7C9 >> 128;
        if (x & 0x200000000000 > 0)
            result = result * 0x10000162E43F4F831060E02D839A9D16D >> 128;
        if (x & 0x100000000000 > 0)
            result = result * 0x100000B1721BCFC99D9F890EA06911763 >> 128;
        if (x & 0x80000000000 > 0)
            result = result * 0x10000058B90CF1E6D97F9CA14DBCC1628 >> 128;
        if (x & 0x40000000000 > 0)
            result = result * 0x1000002C5C863B73F016468F6BAC5CA2B >> 128;
        if (x & 0x20000000000 > 0)
            result = result * 0x100000162E430E5A18F6119E3C02282A5 >> 128;
        if (x & 0x10000000000 > 0)
            result = result * 0x1000000B1721835514B86E6D96EFD1BFE >> 128;
        if (x & 0x8000000000 > 0)
            result = result * 0x100000058B90C0B48C6BE5DF846C5B2EF >> 128;
        if (x & 0x4000000000 > 0)
            result = result * 0x10000002C5C8601CC6B9E94213C72737A >> 128;
        if (x & 0x2000000000 > 0)
            result = result * 0x1000000162E42FFF037DF38AA2B219F06 >> 128;
        if (x & 0x1000000000 > 0)
            result = result * 0x10000000B17217FBA9C739AA5819F44F9 >> 128;
        if (x & 0x800000000 > 0)
            result = result * 0x1000000058B90BFCDEE5ACD3C1CEDC823 >> 128;
        if (x & 0x400000000 > 0)
            result = result * 0x100000002C5C85FE31F35A6A30DA1BE50 >> 128;
        if (x & 0x200000000 > 0)
            result = result * 0x10000000162E42FF0999CE3541B9FFFCF >> 128;
        if (x & 0x100000000 > 0)
            result = result * 0x100000000B17217F80F4EF5AADDA45554 >> 128;
        if (x & 0x80000000 > 0)
            result = result * 0x10000000058B90BFBF8479BD5A81B51AD >> 128;
        if (x & 0x40000000 > 0)
            result = result * 0x1000000002C5C85FDF84BD62AE30A74CC >> 128;
        if (x & 0x20000000 > 0)
            result = result * 0x100000000162E42FEFB2FED257559BDAA >> 128;
        if (x & 0x10000000 > 0)
            result = result * 0x1000000000B17217F7D5A7716BBA4A9AE >> 128;
        if (x & 0x8000000 > 0)
            result = result * 0x100000000058B90BFBE9DDBAC5E109CCE >> 128;
        if (x & 0x4000000 > 0)
            result = result * 0x10000000002C5C85FDF4B15DE6F17EB0D >> 128;
        if (x & 0x2000000 > 0)
            result = result * 0x1000000000162E42FEFA494F1478FDE05 >> 128;
        if (x & 0x1000000 > 0)
            result = result * 0x10000000000B17217F7D20CF927C8E94C >> 128;
        if (x & 0x800000 > 0)
            result = result * 0x1000000000058B90BFBE8F71CB4E4B33D >> 128;
        if (x & 0x400000 > 0)
            result = result * 0x100000000002C5C85FDF477B662B26945 >> 128;
        if (x & 0x200000 > 0)
            result = result * 0x10000000000162E42FEFA3AE53369388C >> 128;
        if (x & 0x100000 > 0)
            result = result * 0x100000000000B17217F7D1D351A389D40 >> 128;
        if (x & 0x80000 > 0)
            result = result * 0x10000000000058B90BFBE8E8B2D3D4EDE >> 128;
        if (x & 0x40000 > 0)
            result = result * 0x1000000000002C5C85FDF4741BEA6E77E >> 128;
        if (x & 0x20000 > 0)
            result = result * 0x100000000000162E42FEFA39FE95583C2 >> 128;
        if (x & 0x10000 > 0)
            result = result * 0x1000000000000B17217F7D1CFB72B45E1 >> 128;
        if (x & 0x8000 > 0)
            result = result * 0x100000000000058B90BFBE8E7CC35C3F0 >> 128;
        if (x & 0x4000 > 0)
            result = result * 0x10000000000002C5C85FDF473E242EA38 >> 128;
        if (x & 0x2000 > 0)
            result = result * 0x1000000000000162E42FEFA39F02B772C >> 128;
        if (x & 0x1000 > 0)
            result = result * 0x10000000000000B17217F7D1CF7D83C1A >> 128;
        if (x & 0x800 > 0)
            result = result * 0x1000000000000058B90BFBE8E7BDCBE2E >> 128;
        if (x & 0x400 > 0)
            result = result * 0x100000000000002C5C85FDF473DEA871F >> 128;
        if (x & 0x200 > 0)
            result = result * 0x10000000000000162E42FEFA39EF44D91 >> 128;
        if (x & 0x100 > 0)
            result = result * 0x100000000000000B17217F7D1CF79E949 >> 128;
        if (x & 0x80 > 0)
            result = result * 0x10000000000000058B90BFBE8E7BCE544 >> 128;
        if (x & 0x40 > 0)
            result = result * 0x1000000000000002C5C85FDF473DE6ECA >> 128;
        if (x & 0x20 > 0)
            result = result * 0x100000000000000162E42FEFA39EF366F >> 128;
        if (x & 0x10 > 0)
            result = result * 0x1000000000000000B17217F7D1CF79AFA >> 128;
        if (x & 0x8 > 0)
            result = result * 0x100000000000000058B90BFBE8E7BCD6D >> 128;
        if (x & 0x4 > 0)
            result = result * 0x10000000000000002C5C85FDF473DE6B2 >> 128;
        if (x & 0x2 > 0)
            result = result * 0x1000000000000000162E42FEFA39EF358 >> 128;
        if (x & 0x1 > 0)
            result = result * 0x10000000000000000B17217F7D1CF79AB >> 128;

        result >>= uint256 (int256 (63 - (x >> 64)));
        require (result <= uint256 (int256 (MAX_64x64)));

        return int128 (int256 (result));
    }
    }

    /**
     * Calculate natural exponent of x.  Revert on overflow.
     *
     * @param x signed 64.64-bit fixed point number
   * @return signed 64.64-bit fixed point number
   */
    function exp (int128 x) internal pure returns (int128) {
    unchecked {
        require (x < 0x400000000000000000); // Overflow

        if (x < -0x400000000000000000) return 0; // Underflow

        return exp_2 (
            int128 (int256 (x) * 0x171547652B82FE1777D0FFDA0D23A7D12 >> 128));
    }
    }

    /**
     * Calculate x / y rounding towards zero, where x and y are unsigned 256-bit
     * integer numbers.  Revert on overflow or when y is zero.
     *
     * @param x unsigned 256-bit integer number
   * @param y unsigned 256-bit integer number
   * @return unsigned 64.64-bit fixed point number
   */
    function divuu (uint256 x, uint256 y) private pure returns (uint128) {
    unchecked {
        require (y != 0);

        uint256 result;

        if (x <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF)
            result = (x << 64) / y;
        else {
            uint256 msb = 192;
            uint256 xc = x >> 192;
            if (xc >= 0x100000000) { xc >>= 32; msb += 32; }
            if (xc >= 0x10000) { xc >>= 16; msb += 16; }
            if (xc >= 0x100) { xc >>= 8; msb += 8; }
            if (xc >= 0x10) { xc >>= 4; msb += 4; }
            if (xc >= 0x4) { xc >>= 2; msb += 2; }
            if (xc >= 0x2) msb += 1;  // No need to shift xc anymore

            result = (x << 255 - msb) / ((y - 1 >> msb - 191) + 1);
            require (result <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);

            uint256 hi = result * (y >> 128);
            uint256 lo = result * (y & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);

            uint256 xh = x >> 192;
            uint256 xl = x << 64;

            if (xl < lo) xh -= 1;
            xl -= lo; // We rely on overflow behavior here
            lo = hi << 128;
            if (xl < lo) xh -= 1;
            xl -= lo; // We rely on overflow behavior here

            assert (xh == hi >> 128);

            result += xl / y;
        }

        require (result <= 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
        return uint128 (result);
    }
    }

    /**
     * Calculate sqrt (x) rounding down, where x is unsigned 256-bit integer
     * number.
     *
     * @param x unsigned 256-bit integer number
   * @return unsigned 128-bit integer number
   */
    function sqrtu (uint256 x) private pure returns (uint128) {
    unchecked {
        if (x == 0) return 0;
        else {
            uint256 xx = x;
            uint256 r = 1;
            if (xx >= 0x100000000000000000000000000000000) { xx >>= 128; r <<= 64; }
            if (xx >= 0x10000000000000000) { xx >>= 64; r <<= 32; }
            if (xx >= 0x100000000) { xx >>= 32; r <<= 16; }
            if (xx >= 0x10000) { xx >>= 16; r <<= 8; }
            if (xx >= 0x100) { xx >>= 8; r <<= 4; }
            if (xx >= 0x10) { xx >>= 4; r <<= 2; }
            if (xx >= 0x8) { r <<= 1; }
            r = (r + x / r) >> 1;
            r = (r + x / r) >> 1;
            r = (r + x / r) >> 1;
            r = (r + x / r) >> 1;
            r = (r + x / r) >> 1;
            r = (r + x / r) >> 1;
            r = (r + x / r) >> 1; // Seven iterations should be enough
            uint256 r1 = x / r;
            return uint128 (r < r1 ? r : r1);
        }
    }
    }
}

// File: contracts/interfaces/IStakingToken.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

interface IStakingToken {
    event Staked(address indexed user, uint256 amount, uint256 term);

    event Withdrawn(address indexed user, uint256 amount, uint256 reward);

//    function stake(uint256 amount, uint256 term) external;

//    function withdraw() external;
}

// File: contracts/interfaces/IRankedMintingToken.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

interface IRankedMintingToken {
    event RankClaimed(address indexed user, uint256 term, uint256 rank);

    event MintClaimed(address indexed user, uint256 rewardAmount);

    function claimRank(uint256 term) payable external;

    function claimMintReward() external;
}

// File: contracts/interfaces/IBurnableToken.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

interface IBurnableToken {
    function burn(address user, uint256 amount) external;
}

// File: contracts/interfaces/IBurnRedeemable.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;

interface IBurnRedeemable {
    event Redeemed(
        address indexed user,
        address indexed yenContract,
        address indexed tokenContract,
        uint256 yenAmount,
        uint256 tokenAmount
    );

    function onTokenBurned(address user, uint256 amount) external;
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^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() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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 {
        _transferOwnership(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");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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
     * ====
     *
     * [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://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");

        (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");

        (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");

        (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");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason 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 {
            // 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/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (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);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/draft-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;

    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'
        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) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    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");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    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");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// 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/introspection/IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-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);
}