// File: contracts/LICENSE.sol



// Copyright (c) 2022-2023 Fellowship
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
// documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice (including the next paragraph) shall be included in all copies
// or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
// WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// File: contracts/DutchAuctionRefundMinter.sol



// SPDX-License-Identifier: MIT
// Copyright (c) 2022-2023 Fellowship

pragma solidity ^0.8.12;

import "@openzeppelin/contracts/utils/math/Math.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "./LimitedPaymentDistributor.sol";
import "./Mintable.sol";
import "./TimedSale.sol";

contract DutchAuctionRefundMinter is LimitedPaymentDistributor, TimedSale {
    uint256 public immutable walletLimit;
    uint256 public immutable mintLimit;
    string private limitRevertMessage;

    /// @notice ERC-721 contract whose tokens are minted by this auction
    /// @dev Must implement Mintable and number tokens sequentially from zero
    Mintable public tokenContract;

    /// @notice Starting price for the Dutch auction (in wei)
    uint256 public startPrice;

    /// @notice Resting price where price descent ends (in wei)
    uint256 public restPrice;

    /// @notice Lowest price at which a token was minted (in wei)
    uint256 public lowestPrice;

    /// @notice Amount that the price drops (in wei) every slot (every 12 seconds)
    uint256 public priceDropPerSlot;

    /// @notice Number of reserveTokens that have been minted
    uint256 public reserveCount = 0;

    /// @notice Number of tokens that have been minted per address
    mapping(address => uint256) public mintCount;
    /// @notice Total amount paid to mint per address
    mapping(address => uint256) public mintPayment;

    uint256 private previousPayment = 0;

    /// @notice An event emitted upon token purchases
    event Purchase(address purchaser, uint256 tokenId, uint256 price);

    /// @notice An event emitted when reserve tokens are minted
    event Reservation(address recipient, uint256 quantity, uint256 totalReserved);

    /// @notice An event emitted when a refund is sent to a minter
    event Refund(address recipient, uint256 amount);

    /// @notice An error returned when the auction has reached its `mintLimit`
    error SoldOut();

    constructor(
        Mintable tokenContract_,
        uint256 startTime_,
        uint256 startPrice_,
        uint256 restPrice_,
        uint256 priceDrop,
        uint256 walletLimit_,
        uint256 mintLimit_
    ) TimedSale(startTime_) {
        // CHECKS inputs
        require(address(tokenContract_) != address(0), "Token contract must not be the zero address");

        require(startPrice_ > 1e15, "Start price too low: check that prices are in wei");
        require(restPrice_ > 1e15, "Rest price too low: check that prices are in wei");
        require(startPrice_ >= restPrice_, "Start price must not be lower than rest price");

        require(walletLimit_ < mintLimit_, "Mint limit should be greater than wallet limit");

        uint256 priceDifference;
        unchecked {
            priceDifference = startPrice_ - restPrice_;
        }
        require(priceDrop * 25 <= priceDifference, "Auction must last at least 5 minutes");
        require(priceDrop * (5 * 60 * 24) >= priceDifference, "Auction must not last longer than 24 hours");

        // EFFECTS
        tokenContract = tokenContract_;
        lowestPrice = startPrice = startPrice_;
        restPrice = restPrice_;
        priceDropPerSlot = priceDrop;

        mintLimit = mintLimit_;
        walletLimit = walletLimit_ != 0 ? walletLimit_ : mintLimit_;
        limitRevertMessage = string.concat("Limited to ", Strings.toString(walletLimit), " purchases per wallet");
    }

    // PUBLIC FUNCTIONS

    /// @notice Mint a token on the `tokenContract` contract. Must include at least `currentPrice`.
    function mint() public payable virtual started whenNotPaused {
        // CHECKS state and inputs
        uint totalCount = tokenContract.totalSupply();
        if (totalCount >= mintLimit) revert SoldOut();
        uint256 price = msg.value;
        require(price >= currentPrice(), "Insufficient payment");
        require(mintCount[msg.sender] < walletLimit, limitRevertMessage);

        // EFFECTS
        unchecked {
            // Unchecked arithmetic: mintCount cannot exceed walletLimit
            mintCount[msg.sender]++;
            // Unchecked arithmetic: can't exceed this.balance; not expected to exceed walletLimit * startPrice
            mintPayment[msg.sender] += price;
        }

        if (price < lowestPrice) {
            lowestPrice = price;
        }

        emit Purchase(msg.sender, totalCount, price);

        // INTERACTIONS: call mint on known contract (tokenContract.mint contains no external interactions)
        tokenContract.mint(msg.sender);
    }

    /// @notice Mint multiple tokens on the `tokenContract` contract. Must pay at least `currentPrice` * `quantity`.
    /// @param quantity The number of tokens to mint: must not be greater than `walletLimit`
    function mintMultiple(uint256 quantity) public payable virtual started whenNotPaused {
        // CHECKS state and inputs
        uint firstId = tokenContract.totalSupply();
        if (firstId >= mintLimit) revert SoldOut();
        uint256 alreadyMinted = mintCount[msg.sender];
        require(quantity > 0, "Must mint at least one token");
        require(quantity <= walletLimit && alreadyMinted < walletLimit, limitRevertMessage);

        uint256 payment = msg.value;
        uint256 price = payment / quantity;
        require(price >= currentPrice(), "Insufficient payment");

        // EFFECTS
        unchecked {
            // Unchecked arithmetic: firstId + quantity is less than mintLimit + walletLimit
            if (firstId + quantity > mintLimit) {
                // Reduce quantity to the remaining supply
                // Unchecked arithmetic: already checked that firstId is less than mintLimit
                quantity = mintLimit - firstId;
            }
            // Unchecked arithmetic: alreadyMinted + quantity is less than 2 * walletLimit
            if (alreadyMinted + quantity > walletLimit) {
                // Reduce quantity to the remaining wallet allowance
                // Unchecked arithmetic: already checked that firstId is less than mintLimit
                quantity = walletLimit - alreadyMinted;
            }

            // Unchecked arithmetic: mintCount cannot exceed walletLimit
            mintCount[msg.sender] = alreadyMinted + quantity;
            // Unchecked arithmetic: can't exceed total existing wei; not expected to exceed walletLimit * startPrice
            mintPayment[msg.sender] += payment;
        }

        if (price < lowestPrice) {
            lowestPrice = price;
        }

        unchecked {
            for (uint256 i = 0; i < quantity; i++) {
                emit Purchase(msg.sender, firstId + i, price);
            }
        }

        // INTERACTIONS: call mint on known contract (tokenContract.mint contains no external interactions)
        tokenContract.mintBatch(msg.sender, quantity);
    }

    /// @notice Mint multiple tokens for the contract owner. Must pay at least `currentPrice` * `quantity`.
    /// @param quantity The number of tokens to mint
    function mintMultipleAbsentee(uint256 quantity) public payable virtual started whenNotPaused onlyOwner {
        // CHECKS state and inputs
        uint firstId = tokenContract.totalSupply();
        if (firstId >= mintLimit) revert SoldOut();
        require(quantity > 0, "Must mint at least one token");

        uint256 payment = msg.value;
        uint256 price = payment / quantity;
        require(price >= currentPrice(), "Insufficient payment");

        // EFFECTS
        unchecked {
            // Unchecked arithmetic: firstId + quantity is less than mintLimit + walletLimit
            if (firstId + quantity > mintLimit) {
                // Reduce quantity to the remaining supply
                // Unchecked arithmetic: already checked that firstId is less than mintLimit
                quantity = mintLimit - firstId;
            }

            // Unchecked arithmetic: mintCount cannot exceed mintLimit
            mintCount[msg.sender] += quantity;
            // Unchecked arithmetic: can't exceed total existing wei; not expected to exceed walletLimit * startPrice
            mintPayment[msg.sender] += payment;
        }

        if (price < lowestPrice) {
            lowestPrice = price;
        }

        unchecked {
            for (uint256 i = 0; i < quantity; i++) {
                emit Purchase(msg.sender, firstId + i, price);
            }
        }

        // INTERACTIONS: call mint on known contract (tokenContract.mint contains no external interactions)
        tokenContract.mintBatch(msg.sender, quantity);
    }

    /// @notice Send any available refund to the message sender
    function refund() external returns (uint256) {
        // CHECK available refund
        uint256 refundAmount = refundAvailable(msg.sender);
        require(refundAmount > 0, "No refund available");

        // EFFECTS
        unchecked {
            // Unchecked arithmetic: refundAmount will always be less than mintPayment
            mintPayment[msg.sender] -= refundAmount;
        }

        emit Refund(msg.sender, refundAmount);

        // INTERACTIONS
        (bool refunded, ) = msg.sender.call{value: refundAmount}("");
        require(refunded, "Refund transfer was reverted");

        return refundAmount;
    }

    // OWNER AND ADMIN FUNCTIONS

    /// @notice Mint reserve tokens to the designated `recipient`
    /// @dev Can only be called by the contract `owner`. Reverts if the auction has already started.
    function reserve(address recipient, uint256 quantity) external unstarted onlyOwner {
        // CHECKS contract state
        uint totalCount = tokenContract.totalSupply();
        if (totalCount + quantity > mintLimit) revert SoldOut();

        // EFFECTS
        unchecked {
            // Unchecked arithmetic: neither value can exceed mintLimit
            reserveCount += quantity;
        }

        emit Reservation(recipient, quantity, reserveCount);

        // INTERACTIONS
        tokenContract.mintBatch(recipient, quantity);
    }

    /// @notice withdraw auction proceeds
    /// @dev Can only be called by the contract `owner` or a payee. Reverts if the final price is unknown or all
    ///  proceeds have already been withdrawn.
    function withdraw() external onlyPayee {
        // CHECKS contract state
        uint totalCount = tokenContract.totalSupply();
        bool soldOut = totalCount >= mintLimit;
        uint256 finalPrice = lowestPrice;
        if (!soldOut) {
            // Only allow a withdraw before the auction is sold out if the price has finished falling
            require(currentPrice() == restPrice, "Price is still falling");
            finalPrice = restPrice;
        }

        uint256 totalPayment = (totalCount - reserveCount) * finalPrice;
        require(totalPayment > previousPayment, "All funds have been withdrawn");

        // EFFECTS
        uint256 outstandingPayment = totalPayment - previousPayment;
        uint256 balance = address(this).balance;
        if (outstandingPayment > balance) {
            // Escape hatch to prevent stuck funds, but this shouldn't happen
            require(balance > 0, "All funds have been withdrawn");
            outstandingPayment = balance;
        }

        previousPayment += outstandingPayment;
        withdraw(outstandingPayment);
    }

    /// @notice Update the tokenContract contract address
    /// @dev Can only be called by the contract `owner`. Reverts if the auction has already started.
    function setMintable(Mintable tokenContract_) external unstarted onlyOwner {
        // CHECKS inputs
        require(address(tokenContract_) != address(0), "Token contract must not be the zero address");
        // EFFECTS
        tokenContract = tokenContract_;
    }

    /// @notice Update the auction price range and rate of decrease
    /// @dev Since the values are validated against each other, they are all set together. Can only be called by the
    ///  contract `owner`. Reverts if the auction has already started.
    function setPriceRange(uint256 startPrice_, uint256 restPrice_, uint256 priceDrop) external unstarted onlyOwner {
        // CHECKS inputs
        require(startPrice_ > 1e15, "Start price too low: check that prices are in wei");
        require(restPrice_ > 1e15, "Rest price too low: check that prices are in wei");
        require(startPrice_ >= restPrice_, "Start price must not be lower than rest price");

        uint256 priceDifference;
        unchecked {
            priceDifference = startPrice_ - restPrice_;
        }
        require(priceDrop * 25 <= priceDifference, "Auction must last at least 5 minutes");
        require(priceDrop * (5 * 60 * 24) >= priceDifference, "Auction must not last longer than 24 hours");

        // EFFECTS
        startPrice = startPrice_;
        restPrice = restPrice_;
        priceDropPerSlot = priceDrop;
    }

    // VIEW FUNCTIONS

    /// @notice Query the current price
    function currentPrice() public view returns (uint256) {
        uint256 time = timeElapsed();
        unchecked {
            uint256 drop = priceDropPerSlot * (time / 12);
            if (startPrice < restPrice + drop) return restPrice;
            return startPrice - drop;
        }
    }

    /// @notice Query the refund available for the specified `minter`
    function refundAvailable(address minter) public view returns (uint256) {
        uint256 minted = mintCount[minter];
        if (minted == 0) return 0;

        uint totalCount = tokenContract.totalSupply();
        bool soldOut = totalCount >= mintLimit;
        uint256 refundPrice = soldOut ? lowestPrice : currentPrice();

        uint256 payment = mintPayment[minter];
        uint256 newPayment;
        uint256 refundAmount;
        unchecked {
            // Unchecked arithmetic: newPayment cannot exceed walletLimit * startPrice
            newPayment = minted * refundPrice;
            // Unchecked arithmetic: value only used if newPayment < payment
            refundAmount = payment - newPayment;
        }

        return (newPayment < payment) ? refundAmount : 0;
    }
}

// File: contracts/LimitedPaymentDistributor.sol



// SPDX-License-Identifier: MIT
// Copyright (c) 2022 Fellowship

pragma solidity ^0.8.7;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

/// @title Limited Payment Distributor
/// @notice Distributes limited amounts of Ethereum or tokens to payees according to their shares
/// @dev While `owner` already has full control, this contract uses `ReentrancyGuard` to prevent any footgun shenanigans
///  that could result from calling `setShares` during `withdraw`
contract LimitedPaymentDistributor is Ownable, ReentrancyGuard {
    uint256 private shareCount;
    address[] private payees;
    mapping(address => PayeeInfo) private payeeInfo;

    struct PayeeInfo {
        uint128 index;
        uint128 shares;
    }

    error PaymentsNotConfigured();
    error OnlyPayee();
    error FailedPaying(address payee, bytes data);

    /// @dev Check that caller is owner or payee
    modifier onlyPayee() {
        if (shareCount == 0) revert PaymentsNotConfigured();
        if (msg.sender != owner()) {
            // Get the stored index for the sender
            uint256 index = payeeInfo[msg.sender].index;
            // Check that they are actually at that index
            if (payees[index] != msg.sender) revert OnlyPayee();
        }

        _;
    }

    modifier paymentsConfigured() {
        if (shareCount == 0) revert PaymentsNotConfigured();
        _;
    }

    receive() external payable {}

    // OWNER FUNCTIONS

    /// @notice Sets `payees_` who receive funds from this contract in accordance with shares in the `shares` array
    /// @dev `payees_` and `shares` must have the same length and non-zero values
    function setShares(address[] calldata payees_, uint128[] calldata shares) external onlyOwner nonReentrant {
        // CHECKS inputs
        require(payees_.length > 0, "Must set at least one payee");
        require(payees_.length < type(uint128).max, "Too many payees");
        require(payees_.length == shares.length, "Payees and shares must have the same length");

        // CHECKS + EFFECTS: check each payee before setting values
        shareCount = 0;
        payees = payees_;
        unchecked {
            // Unchecked arithmetic: already checked that the number of payees is less than uint128 max
            for (uint128 i = 0; i < payees_.length; i++) {
                address payee = payees_[i];
                uint128 payeeShares = shares[i];
                require(payee != address(0), "Payees must not be the zero address");
                require(payeeShares > 0, "Payees shares must not be zero");

                // Unchecked arithmetic: since number of payees is less than uint128 max and share values are uint128,
                // `shareCount` cannot exceed uint256 max.
                shareCount += payeeShares;
                PayeeInfo storage info = payeeInfo[payee];
                info.index = i;
                info.shares = payeeShares;
            }
        }
    }

    // INTERNAL FUNCTIONS

    /// @notice Distributes the specified `amount` from the contract balance to the `payees`
    function withdraw(uint256 amount) internal {
        uint256 shareSplit = amount / shareCount;

        // INTERACTIONS
        bool success;
        bytes memory data;
        for (uint256 i = 0; i < payees.length; i++) {
            address payee = payees[i];
            unchecked {
                (success, data) = payee.call{value: shareSplit * payeeInfo[payee].shares}("");
            }
            if (!success) revert FailedPaying(payee, data);
        }
    }

    /// @notice Distributes a specified `amount` of tokens held by this contract to the `payees`
    function withdrawToken(IERC20 token, uint256 amount) internal {
        uint256 shareSplit = amount / shareCount;

        // INTERACTIONS
        bool success;
        bytes memory data;
        for (uint256 i = 0; i < payees.length; i++) {
            address payee = payees[i];

            unchecked {
                // Based on token/ERC20/utils/SafeERC20.sol and utils/Address.sol from OpenZeppelin Contracts v4.7.0
                (success, data) = address(token).call(
                    abi.encodeWithSelector(token.transfer.selector, payee, shareSplit * payeeInfo[payee].shares)
                );
            }
            if (!success) {
                if (data.length > 0) revert FailedPaying(payee, data);
                revert FailedPaying(payee, "Transfer reverted");
            } else if (data.length > 0 && !abi.decode(data, (bool))) {
                revert FailedPaying(payee, "Transfer failed");
            }
        }
    }
}

// File: contracts/Mintable.sol



// SPDX-License-Identifier: MIT
// Copyright (c) 2023 Fellowship

pragma solidity ^0.8.7;

import "@openzeppelin/contracts/token/ERC721/IERC721.sol";

abstract contract Mintable is IERC721 {
    function mint(address to) external virtual;

    function mintBatch(address to, uint256 amount) external virtual;

    function totalSupply() external view virtual returns (uint256);
}

// File: contracts/Pausable.sol



// SPDX-License-Identifier: MIT
// Copyright (c) 2022 Fellowship

pragma solidity ^0.8.7;

import "@openzeppelin/contracts/access/Ownable.sol";

contract Pausable is Ownable {
    /// @notice Whether or not this contract is paused
    /// @dev The exact meaning of "paused" will vary by contract, but in general paused contracts should prevent most
    ///  interactions from non-owners
    bool public isPaused = false;

    event Paused();
    event Unpaused();

    error ContractIsPaused();
    error ContractNotPaused();

    modifier whenPaused() {
        if (!isPaused) revert ContractNotPaused();
        _;
    }

    modifier whenNotPaused() {
        if (isPaused) revert ContractIsPaused();
        _;
    }

    // OWNER FUNCTIONS

    /// @notice Pause this contract
    /// @dev Can only be called by the contract `owner`
    function pause() public virtual whenNotPaused onlyOwner {
        // EFFECTS (checks already handled by modifiers)
        isPaused = true;
        emit Paused();
    }

    /// @notice Resume this contract
    /// @dev Can only be called by the contract `owner`
    function unpause() public virtual whenPaused onlyOwner {
        // EFFECTS (checks already handled by modifiers)
        isPaused = false;
        emit Unpaused();
    }

    // VIEW FUNCTIONS

    /// @notice Query if this contract implements an interface
    /// @param interfaceId The interface identifier, as specified in ERC-165
    /// @return `true` if `interfaceID` is implemented and is not 0xffffffff, `false` otherwise
    function supportsInterface(bytes4 interfaceId) public pure virtual returns (bool) {
        return
            interfaceId == 0x7f5828d0 || // ERC-173 Contract Ownership Standard
            interfaceId == 0x01ffc9a7; // ERC-165 Standard Interface Detection
    }
}

// File: contracts/TimedSale.sol



// SPDX-License-Identifier: MIT
// Copyright (c) 2022 - 2023 Fellowship

pragma solidity ^0.8.7;
import "./Pausable.sol";

contract TimedSale is Pausable {
    /// @notice Timestamp when this auction starts allowing minting
    uint256 public startTime;

    uint256 private pauseStart;
    uint256 internal pastPauseDelay;

    /// @notice An error returned when the auction has already started
    error AlreadyStarted();
    /// @notice An error returned when the auction has not yet started
    error NotYetStarted();

    constructor(uint startTime_) {
        // CHECKS inputs
        require(startTime_ >= block.timestamp, "Start time cannot be in the past");

        // EFFECTS
        startTime = startTime_;
    }

    modifier started() {
        if (!isStarted()) revert NotYetStarted();
        _;
    }
    modifier unstarted() {
        if (isStarted()) revert AlreadyStarted();
        _;
    }

    // OWNER FUNCTIONS

    /// @notice Pause this contract
    /// @dev Can only be called by the contract `owner`
    function pause() public override {
        // CHECKS + EFFECTS: `Pausable` handles checking permissions and setting pause state
        super.pause();
        // More EFFECTS
        pauseStart = block.timestamp;
    }

    /// @notice Resume this contract
    /// @dev Can only be called by the contract `owner`. Pricing tiers will pick up where they left off.
    function unpause() public override {
        // CHECKS + EFFECTS: `Pausable` handles checking permissions and setting pause state
        super.unpause();
        // More EFFECTS
        if (block.timestamp <= startTime) {
            return;
        }
        // Find the amount time the auction should have been live, but was paused
        unchecked {
            // Unchecked arithmetic: computed value will be < block.timestamp and >= 0
            if (pauseStart < startTime) {
                pastPauseDelay = block.timestamp - startTime;
            } else {
                pastPauseDelay += (block.timestamp - pauseStart);
            }
        }
    }

    /// @notice Update the auction start time
    /// @dev Can only be called by the contract `owner`. Reverts if the auction has already started.
    function setStartTime(uint256 startTime_) external unstarted onlyOwner {
        // CHECKS inputs
        require(startTime_ >= block.timestamp, "New start time cannot be in the past");
        // EFFECTS
        startTime = startTime_;
    }

    // INTERNAL FUNCTIONS

    function isStarted() internal view virtual returns (bool) {
        return (isPaused ? pauseStart : block.timestamp) >= startTime;
    }

    function timeElapsed() internal view returns (uint256) {
        if (!isStarted()) return 0;
        unchecked {
            // pastPauseDelay cannot be greater than the time passed since startTime
            if (!isPaused) {
                return block.timestamp - startTime - pastPauseDelay;
            }

            // pastPauseDelay cannot be greater than the time between startTime and pauseStart
            return pauseStart - startTime - pastPauseDelay;
        }
    }
}

// File: contracts/OPENZEPPELIN_LICENSE.sol



// OpenZeppelin Contracts
//
// Copyright (c) 2016-2023 zOS Global Limited and contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
// documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
// Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
// WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// 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/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/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/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

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

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Note that the caller is responsible to confirm that the recipient is capable of receiving ERC721
     * or else they may be permanently lost. Usage of {safeTransferFrom} prevents loss, though the caller must
     * understand this adds an external call which potentially creates a reentrancy vulnerability.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (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) {
                return prod0 / denominator;
            }

            // Make sure the result is less than 2^256. Also prevents denominator == 0.
            require(denominator > prod1);

            ///////////////////////////////////////////////
            // 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 10, 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 * 8) < value ? 1 : 0);
        }
    }
}

// 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/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

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

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

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

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

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/Strings.sol)

pragma solidity ^0.8.0;

import "./math/Math.sol";

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _SYMBOLS = "0123456789abcdef";
    uint8 private constant _ADDRESS_LENGTH = 20;

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        unchecked {
            uint256 length = Math.log10(value) + 1;
            string memory buffer = new string(length);
            uint256 ptr;
            /// @solidity memory-safe-assembly
            assembly {
                ptr := add(buffer, add(32, length))
            }
            while (true) {
                ptr--;
                /// @solidity memory-safe-assembly
                assembly {
                    mstore8(ptr, byte(mod(value, 10), _SYMBOLS))
                }
                value /= 10;
                if (value == 0) break;
            }
            return buffer;
        }
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        unchecked {
            return toHexString(value, Math.log256(value) + 1);
        }
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }

    /**
     * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
     */
    function toHexString(address addr) internal pure returns (string memory) {
        return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
    }
}