// File: /contracts/Krakatoa.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.12;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/utils/cryptography/EIP712.sol";
import "./Additional.sol";

contract Krakatoa is Ownable, Additional, EIP712("Krakatoa", "2.0") {
    using ECDSA for bytes32;

    enum OrderStatus {Unknown, Pending, WithdrawnFee, Withdrawn, Refunded}
    enum OfferStatus {Unknown, Partial, Processed, Canceled}

    event OrderStatusChanged(uint64 indexed orderId, OrderStatus indexed status);
    event OfferStatusChanged(uint64 indexed offerId, OfferStatus indexed status, uint8 quantity);

    bytes32 private constant OFFER_TYPE = keccak256("Offer(uint64 offerId,address buyer,uint8 quantity,uint256 price,uint64 productId,uint256 finalTimestamp)");

    struct Product {
        address seller;
        uint64 productId;
        uint256 price;
        uint256 nonce;
    }

    struct Order {
        uint256 price;
        uint256 fee;
        address buyer;
        OrderStatus status;
        address seller;
        uint64 product;
    }

    struct Offer {
        uint64 offerId;
        address buyer;
        uint8 quantity;
        uint256 price;
        uint64 productId;
        uint256 finalTimestamp;
    }

    struct OfferInfo {
        uint256 price;
        address buyer;
        uint8 quantity;
        OfferStatus status;
        uint64[] orders;
    }

    struct OrderInfo {
        uint256 price;
        uint256 fee;
        uint64 productId;
        OrderStatus status;
    }

    address public immutable token;

    mapping(uint64 => Order) private _orders;
    mapping(uint64 => uint) private _nonces;
    mapping(uint64 => OfferInfo) private _offers;

    constructor(address _token) {
        token = _token;
    }

    modifier checkSignature(bytes memory data, bytes memory signature) {
        require(signerRole() == keccak256(data).toEthSignedMessageHash().recover(signature), "KR: Invalid signature");
        _;
    }

    modifier checkRequest(uint64 orderId, uint256 finalTimestamp) {
        require(block.timestamp < finalTimestamp, "KR: Signed transaction expired");
        require(_orders[orderId].status == OrderStatus.Unknown, "KR: Order already processed");
        //Prevents to execute another transaction for the same order
        _orders[orderId].status = OrderStatus.Pending;
        _;
    }

    /**
     * @dev make direct sell on krakatoa
     * @param orderId order id
     * @param products products to sell
     * @param finalTimestamp timestamp of the end of the order
     * @param signature signature of the order
     */
    function directSell(uint64 orderId, Product[] calldata products, uint256 finalTimestamp, bytes calldata signature) external
    checkSignature(abi.encode(_msgSender(), orderId, products, finalTimestamp), signature)
    {
        _directSell(_msgSender(), orderId, products, finalTimestamp);
    }

    /**
     * @dev Make p2c sell on krakatoa
     * @param orderId order id
     * @param product product to sell
     * @param finalTimestamp timestamp of the end of the order
     * @param signature signature of the order
     */
    function p2cSell(uint64 orderId, Product calldata product, uint256 finalTimestamp, bytes calldata signature) external
    checkSignature(abi.encode(_msgSender(), orderId, product, finalTimestamp), signature)
    {
        _p2cSell(_msgSender(), orderId, product, finalTimestamp);
    }


    modifier checkOfferSignature(Offer memory offer, bytes calldata offerSignature) {
        require(ECDSA.recover(_hashTypedDataV4(keccak256(abi.encode(OFFER_TYPE, offer))), offerSignature) == offer.buyer, "KR: Invalid offer signature");
        _;
    }

    /**
     * @dev Make p2c sell for offer
     * @param orderId order id
     * @param product product to sell
     * @param offer offer to commit
     * @param offerSignature signature of the offer
     * @param signature signature of the order
     */
    function p2cSellOffer(uint64 orderId, Product calldata product, Offer calldata offer, bytes calldata offerSignature, bytes calldata signature) external
    checkSignature(abi.encode(_msgSender(), orderId, product, offer, offerSignature), signature)
    checkOfferSignature(offer, offerSignature)
    {
        _p2cSell(offer.buyer, orderId, _checkOffer(product, offer), offer.finalTimestamp);

        _commitOffer(offer, orderId);
    }

    /**
     * @dev Make direct sell by offer
     * @param orderId order id
     * @param product product to sell
     * @param offer offer to commit
     * @param offerSignature signature of the offer
     * @param signature signature of the order
     */
    function directSellOffer(uint64 orderId, Product calldata product, Offer calldata offer, bytes calldata offerSignature, bytes calldata signature) external
    checkSignature(abi.encode(_msgSender(), orderId, product, offer, offerSignature), signature)
    checkOfferSignature(offer, offerSignature)
    {
        Product[] memory products = new Product[](1);
        products[0] = _checkOffer(product, offer);
        _directSell(offer.buyer, orderId, products, offer.finalTimestamp);

        _commitOffer(offer, orderId);
    }

    /**
     * @dev Cancel the offer
     * @param offer offer to cancel
     * @param offerSignature signature of the offer
     * @param signature signature of the order
     */
    function cancelOffer(Offer memory offer, bytes calldata offerSignature, bytes calldata signature) external
    checkSignature(abi.encode(_msgSender(), offer, offerSignature), signature)
    checkOfferSignature(offer, offerSignature)
    {
        uint64 offerId = offer.offerId;
        require(_offers[offerId].status <= OfferStatus.Partial, "KR: Order already processed");
        _offers[offerId].status = OfferStatus.Canceled;
        _offers[offerId].price = offer.price;
        _offers[offerId].buyer = offer.buyer;

        emit OfferStatusChanged(offerId, OfferStatus.Canceled, _offers[offerId].quantity);
    }

    /**
     * @dev Get the order info
     * @param buyer buyer of the order
     * @param orderId order id
     * @param products products to sell
     * @param finalTimestamp timestamp of the end of the order
     */
    function _directSell(address buyer, uint64 orderId, Product[] memory products, uint256 finalTimestamp) internal
    checkRequest(orderId, finalTimestamp)
    {
        require(products.length > 0 && products.length < 255, "KR: Invalid products count");
        uint256 total = 0;
        uint256 fees = 0;
        uint256[] memory prices = new uint256[](products.length);

        for (uint8 i = 0; i < products.length; i++) {
            Product memory product = products[i];
            require(_nonces[product.productId] < product.nonce, "KR: Item already sold");
            require(product.seller != address(0), "KR: Wrong seller");
            total += product.price;
            uint256 fee = _getFee(product.price);
            fees += fee;
            prices[i] = product.price - fee;
        }

        require(IERC20(token).balanceOf(buyer) >= total, "KR: Not enough tokens on the wallet");
        require(IERC20(token).allowance(buyer, address(this)) >= total, "KR: Not enough approved value");

        for (uint8 i = 0; i < products.length; i++) {
            Product memory product = products[i];
            _nonces[product.productId] = product.nonce;

            require(IERC20(token).transferFrom(buyer, product.seller, prices[i]), "KR: Unable to send funds");
        }

        require(IERC20(token).transferFrom(buyer, feeWallet(), fees), "KR: Unable to send fee");

        _orders[orderId].price = total;
        _orders[orderId].fee = fees;
        _orders[orderId].buyer = buyer;
        _orders[orderId].status = OrderStatus.Withdrawn;
        emit OrderStatusChanged(orderId, OrderStatus.Withdrawn);
    }

    /**
     * @dev Get the order info
     * @param buyer buyer of the order
     * @param orderId order id
     * @param product product to sell
     * @param finalTimestamp timestamp of the end of the order
     */
    function _p2cSell(address buyer, uint64 orderId, Product memory product, uint256 finalTimestamp) internal
    checkRequest(orderId, finalTimestamp)
    {
        require(_nonces[product.productId] < product.nonce, "KR: Item already sold");
        require(IERC20(token).transferFrom(buyer, address(this), product.price), "KR: Unable to transfer funds");

        uint256 fee = _getFee(product.price);
        _nonces[product.productId] = product.nonce;
        _orders[orderId] = Order(product.price - fee, fee, buyer, OrderStatus.Pending, product.seller, product.productId);

        emit OrderStatusChanged(orderId, OrderStatus.Pending);
    }

    /**
     * @dev Check the offer
     * @param product product to sell
     * @param offer offer to commit
     */
    function _checkOffer(Product calldata product, Offer calldata offer) internal returns (Product memory) {
        uint64 offerId = offer.offerId;
        require(offer.finalTimestamp >= block.timestamp, "KR: Offer expired");
        require(_offers[offerId].status <= OfferStatus.Partial, "KR: Order already processed");
        require(_offers[offerId].quantity < offer.quantity, "KR: Quantity is exhausted");
        require(offer.productId == 0 || offer.productId == product.productId, "KR: Wrong product");
        _offers[offerId].status = OfferStatus.Processed;

        return Product(product.seller, product.productId, offer.price, product.nonce);
    }

    /**
     * @dev Commit the offer
     * @param offer offer to commit
     * @param orderId order id
     */
    function _commitOffer(Offer calldata offer, uint64 orderId) internal {
        uint64 offerId = offer.offerId;
        uint8 quantity = _offers[offerId].quantity + 1;
        OfferStatus status = quantity == offer.quantity ? OfferStatus.Processed : OfferStatus.Partial;

        _offers[offerId].price = offer.price;
        _offers[offerId].buyer = offer.buyer;
        _offers[offerId].quantity = quantity;
        _offers[offerId].status = status;
        _offers[offerId].orders.push(orderId);

        emit OfferStatusChanged(offerId, status, _offers[offerId].quantity);
    }

    /**
     * @dev Withdraw orders funds
     * @param orders orders to withdraw
     * @param signature signature of the order
     */
    function withdrawOrders(uint64[] calldata orders, bytes calldata signature) external
    checkSignature(abi.encode(orders), signature)
    {
        bool[] memory isWithdraw;
        _processOrders(orders, isWithdraw, 1);
    }

    /**
     * @dev Refund orders funds
     * @param orders orders to refund
     * @param signature signature of the order
     */
    function refundOrders(uint64[] calldata orders, bytes calldata signature) external
    checkSignature(abi.encode(orders), signature)
    {
        bool[] memory isWithdraw;
        _processOrders(orders, isWithdraw, 2);
    }

    /**
     * @dev Withdraw or refund orders funds
     * @param orders orders to process
     * @param isWithdraw true - withdraw, false - refund
     * @param signature signature of the order
     */
    function processOrders(uint64[] calldata orders, bool[] calldata isWithdraw, bytes calldata signature) external
    checkSignature(abi.encode(orders, isWithdraw), signature)
    {
        require(orders.length == isWithdraw.length, "KR: Invalid data");

        _processOrders(orders, isWithdraw, 0);
    }

    function _processOrders(uint64[] memory orders, bool[] memory isWithdraw, uint8 _type) internal {
        uint256 fee = 0;
        uint256 total = 0;

        for (uint8 i = 0; i < orders.length; ++i) {
            Order memory r = _orders[orders[i]];
            if (_type == 1 || (_type == 0 && isWithdraw[i])) {
                _orders[orders[i]].status = OrderStatus.Withdrawn;

                require(r.status == OrderStatus.Pending || r.status == OrderStatus.WithdrawnFee, "KR: Order already processed");
                require(r.seller == _msgSender(), "KR: Recipient of order is not seller");

                total += r.price;

                if (r.status != OrderStatus.WithdrawnFee) {
                    fee += r.fee;
                }

                emit OrderStatusChanged(orders[i], OrderStatus.Withdrawn);
            } else {
                _orders[orders[i]].status = OrderStatus.Refunded;

                require(r.status == OrderStatus.Pending, "KR: Order already withdrawed");
                require(r.buyer == _msgSender(), "KR: Recipient of order is not buyer");

                total += r.price + r.fee;

                emit OrderStatusChanged(orders[i], OrderStatus.Refunded);
            }
        }

        if (total > 0) {
            require(IERC20(token).transfer(_msgSender(), total), "KR: Unable to send funds");
        }

        if (fee > 0) {
            require(IERC20(token).transfer(feeWallet(), fee), "KR: Unable to send fee");
        }
    }

    /**
    * @dev Withdraw or refund orders funds by admin
    * @param orders orders to withdraw
    * @param isWithdraw true - withdraw, false - refund
    * @param signature signature of the order
    */
    function processOrdersByAdmin(uint64[] calldata orders, bool[] calldata isWithdraw, bytes calldata signature) external onlyAdmin
    checkSignature(abi.encode(orders, isWithdraw), signature)
    {
        require(orders.length == isWithdraw.length, "KR: Invalid data");

        uint256 fee = 0;

        for (uint8 i = 0; i < orders.length; ++i) {
            Order memory r = _orders[orders[i]];
            _orders[orders[i]].status = isWithdraw[i] ? OrderStatus.Withdrawn : OrderStatus.Refunded;
            require(r.status == OrderStatus.Pending || (isWithdraw[i] && r.status == OrderStatus.WithdrawnFee), "KR: Order already processed");

            if (isWithdraw[i]) {
                if (r.status != OrderStatus.WithdrawnFee) {
                    fee += r.fee;
                }
                require(IERC20(token).transfer(r.seller, r.price), "KR: Unable to send funds");
            } else {
                require(IERC20(token).transfer(r.buyer, r.price + r.fee), "KR: Unable to send funds");
            }

            emit OrderStatusChanged(orders[i], isWithdraw[i] ? OrderStatus.Withdrawn : OrderStatus.Refunded);
        }

        if (fee > 0) {
            require(IERC20(token).transfer(feeWallet(), fee), "KR: Unable to send fee");
        }
    }

    /**
     * @dev Withdraw fee
     * @param orders orders to withdraw
     * @param signature signature of the order
     */
    function withdrawFee(uint64[] calldata orders, bytes calldata signature) external onlyAdmin
    checkSignature(abi.encode(orders), signature)
    {
        address signer = keccak256(abi.encode(orders)).toEthSignedMessageHash().recover(signature);
        require(signerRole() == signer, "KR: Invalid signature");

        uint value = 0;

        for (uint16 i = 0; i < orders.length; ++i) {
            uint64 orderId = orders[i];
            require(_orders[orderId].status == OrderStatus.Pending, "KR: Order already processed");

            value += _orders[orderId].fee;
            _orders[orderId].status = OrderStatus.WithdrawnFee;

            emit OrderStatusChanged(orderId, OrderStatus.WithdrawnFee);
        }

        require(IERC20(token).transfer(feeWallet(), value), "KR: Unable to send fee");
    }

    /**
     * @dev Withdraw order to wallet
     * @param orders orders to withdraw
     * @param wallet wallet to withdraw
     * @param signature signature of the order
     */
    function withdrawOrderTo(uint64[] calldata orders, address payable wallet, bytes calldata signature) external onlyOwner
    checkSignature(abi.encode(orders, wallet), signature)
    {
        uint value = 0;

        for (uint16 i = 0; i < orders.length; ++i) {
            Order memory r = _orders[orders[i]];
            _orders[orders[i]].status = OrderStatus.Withdrawn;

            require(r.status == OrderStatus.Pending || r.status == OrderStatus.WithdrawnFee, string.concat("KR: Order already processed: ", Strings.toString(orders[i])));

            value += r.price;

            if (r.status != OrderStatus.WithdrawnFee) {
                value += r.fee;
            }

            emit OrderStatusChanged(orders[i], OrderStatus.Withdrawn);
        }

        require(IERC20(token).transfer(wallet, value), "KR: Unable to send funds");
    }

    /**
     * @dev Get the order info
     */
    function getOrder(uint64 orderId) external view returns (OrderInfo memory) {
        Order memory r = _orders[orderId];
        return OrderInfo(r.price, r.fee, r.product, r.status);
    }

    /**
     * @dev Get the offer info
     */
    function getOffer(uint64 offerId) external view returns (OfferInfo memory) {
        return _offers[offerId];
    }

    /**
     * @dev Get orders info
     */
    function getOrders(uint64[] calldata orderIds) external view returns (OrderInfo[] memory orders) {
        orders = new OrderInfo[](orderIds.length);
        for (uint8 i = 0; i < orderIds.length; ++i) {
            Order memory r = _orders[orderIds[i]];
            orders[i] = OrderInfo(r.price, r.fee, r.product, r.status);
        }
    }

    /**
     * @dev Check the offer
     */
    function checkOffer(Offer calldata offer, bytes calldata signature) external view
    checkOfferSignature(offer, signature)
    returns (Offer calldata)
    {
        uint64 offerId = offer.offerId;
        require(offer.finalTimestamp >= block.timestamp, "KR: Offer expired");
        require(_offers[offerId].status <= OfferStatus.Partial, "KR: Order already processed");
        require(_offers[offerId].quantity < offer.quantity, "KR: Quantity is exhausted");
        return offer;
    }
}

// File: /contracts/Additional.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

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

contract Additional is Ownable {
    address private _feeWallet;
    address private _signerRole;
    address private _adminRole;
    uint16 private _commission;

    event CommissionChanged(uint16 indexed previousCommission, uint16 indexed newCommission);
    event FeeWalletChanged(address indexed previousOwner, address indexed newOwner);
    event SugnerRoleChanged(address indexed previousOwner, address indexed newOwner);
    event AdminRoleChanged(address indexed previousOwner, address indexed newOwner);

     modifier onlyAdmin() {
         require(_adminRole == _msgSender(), "KR: Caller is not the admin");
        _;
    }


    /**
    * @dev Initializes the contract setting the deployer as the initial fee wallet.
    */
    constructor() {
        _feeWallet = 0x6952143ceD1F519c6aedc9C03b10B9A1b7CdA133;
        _signerRole = 0x2085DFc2619d10b1b5c0CeFDdf9fa13DFDeEAe3E;
        _adminRole = 0x6952143ceD1F519c6aedc9C03b10B9A1b7CdA133;
        _commission = 500; //default commission 5%
    }

    /**
     * @dev Returns the commission on the contract.
     */
    function getCommission() external view returns (uint16) {
        return _commission;
    }

    /**
     * @dev Returns the address of the current fee wallet.
     */
    function getFeeWallet() external view returns (address) {
        return _feeWallet;
    }

    /**
     * @dev Returns the address of the current fee wallet.
     */
    function feeWallet() internal view returns (address payable) {
        return payable(_feeWallet);
    }

    /**
     * @dev Returns the address of the current admin wallet.
     */
    function adminRole() public view returns (address) {
        return _adminRole;
    }

    /**
     * @dev Returns the address of the current backend wallet.
     */
    function signerRole() public view returns (address) {
        return _signerRole;
    }

    /**
     * @dev Change commission of the contract to a new value.
     * Can only be called by the current admin.
     */
    function changeCommission(uint16 commission_) external onlyAdmin {
        uint16 oldComission = _commission;
        _commission = commission_;

        emit CommissionChanged(oldComission, commission_);
    }

    /**
     * @dev Change fee wallet of the contract to a new account (`newFeeWallet`).
     * Can only be called by the current owner.
     */
    function changeFeeWallet(address newFeeWallet) external onlyOwner {
        require(newFeeWallet != address(0), "KR: new fee wallet is the zero address");
        address oldFeeWallet = _feeWallet;
        _feeWallet = newFeeWallet;
        emit FeeWalletChanged(oldFeeWallet, newFeeWallet);
    }

    /**
     * @dev Change signer wallet of the contract to a new account.
     * Can only be called by the current owner.
     */
    function changeSignerRole(address newSignerRole) external onlyOwner {
        require(newSignerRole != address(0), "KR: new signer wallet is the zero address");
         address oldSignerRole = _signerRole;
        _signerRole = newSignerRole;
        emit SugnerRoleChanged(oldSignerRole, newSignerRole);
    }

    /**
     * @dev Change admin wallet of the contract to a new account.
     * Can only be called by the current owner.
     */
    function changeAdminRole(address newAdminRole) external onlyOwner {
        require(newAdminRole != address(0), "KR: new admin wallet is the zero address");
         address oldAdminRole = _adminRole;
        _adminRole = newAdminRole;
        emit AdminRoleChanged(oldAdminRole, newAdminRole);
    }

    function getFeeValue(uint price) external view returns(uint, uint) { 
        uint fee = _getFee(price);
        return (fee,  price - fee);
    }

    function _getFee(uint price) internal view returns(uint) { 
        return price * _commission / 10000;
    }
}

// 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/utils/cryptography/EIP712.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/cryptography/EIP712.sol)

pragma solidity ^0.8.0;

import "./ECDSA.sol";

/**
 * @dev https://eips.ethereum.org/EIPS/eip-712[EIP 712] is a standard for hashing and signing of typed structured data.
 *
 * The encoding specified in the EIP is very generic, and such a generic implementation in Solidity is not feasible,
 * thus this contract does not implement the encoding itself. Protocols need to implement the type-specific encoding
 * they need in their contracts using a combination of `abi.encode` and `keccak256`.
 *
 * This contract implements the EIP 712 domain separator ({_domainSeparatorV4}) that is used as part of the encoding
 * scheme, and the final step of the encoding to obtain the message digest that is then signed via ECDSA
 * ({_hashTypedDataV4}).
 *
 * The implementation of the domain separator was designed to be as efficient as possible while still properly updating
 * the chain id to protect against replay attacks on an eventual fork of the chain.
 *
 * NOTE: This contract implements the version of the encoding known as "v4", as implemented by the JSON RPC method
 * https://docs.metamask.io/guide/signing-data.html[`eth_signTypedDataV4` in MetaMask].
 *
 * _Available since v3.4._
 */
abstract contract EIP712 {
    /* solhint-disable var-name-mixedcase */
    // Cache the domain separator as an immutable value, but also store the chain id that it corresponds to, in order to
    // invalidate the cached domain separator if the chain id changes.
    bytes32 private immutable _CACHED_DOMAIN_SEPARATOR;
    uint256 private immutable _CACHED_CHAIN_ID;
    address private immutable _CACHED_THIS;

    bytes32 private immutable _HASHED_NAME;
    bytes32 private immutable _HASHED_VERSION;
    bytes32 private immutable _TYPE_HASH;

    /* solhint-enable var-name-mixedcase */

    /**
     * @dev Initializes the domain separator and parameter caches.
     *
     * The meaning of `name` and `version` is specified in
     * https://eips.ethereum.org/EIPS/eip-712#definition-of-domainseparator[EIP 712]:
     *
     * - `name`: the user readable name of the signing domain, i.e. the name of the DApp or the protocol.
     * - `version`: the current major version of the signing domain.
     *
     * NOTE: These parameters cannot be changed except through a xref:learn::upgrading-smart-contracts.adoc[smart
     * contract upgrade].
     */
    constructor(string memory name, string memory version) {
        bytes32 hashedName = keccak256(bytes(name));
        bytes32 hashedVersion = keccak256(bytes(version));
        bytes32 typeHash = keccak256(
            "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
        );
        _HASHED_NAME = hashedName;
        _HASHED_VERSION = hashedVersion;
        _CACHED_CHAIN_ID = block.chainid;
        _CACHED_DOMAIN_SEPARATOR = _buildDomainSeparator(typeHash, hashedName, hashedVersion);
        _CACHED_THIS = address(this);
        _TYPE_HASH = typeHash;
    }

    /**
     * @dev Returns the domain separator for the current chain.
     */
    function _domainSeparatorV4() internal view returns (bytes32) {
        if (address(this) == _CACHED_THIS && block.chainid == _CACHED_CHAIN_ID) {
            return _CACHED_DOMAIN_SEPARATOR;
        } else {
            return _buildDomainSeparator(_TYPE_HASH, _HASHED_NAME, _HASHED_VERSION);
        }
    }

    function _buildDomainSeparator(
        bytes32 typeHash,
        bytes32 nameHash,
        bytes32 versionHash
    ) private view returns (bytes32) {
        return keccak256(abi.encode(typeHash, nameHash, versionHash, block.chainid, address(this)));
    }

    /**
     * @dev Given an already https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct[hashed struct], this
     * function returns the hash of the fully encoded EIP712 message for this domain.
     *
     * This hash can be used together with {ECDSA-recover} to obtain the signer of a message. For example:
     *
     * ```solidity
     * bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
     *     keccak256("Mail(address to,string contents)"),
     *     mailTo,
     *     keccak256(bytes(mailContents))
     * )));
     * address signer = ECDSA.recover(digest, signature);
     * ```
     */
    function _hashTypedDataV4(bytes32 structHash) internal view virtual returns (bytes32) {
        return ECDSA.toTypedDataHash(_domainSeparatorV4(), structHash);
    }
}

// File: @openzeppelin/contracts/utils/cryptography/ECDSA.sol



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

pragma solidity ^0.8.0;

import "../Strings.sol";

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
    enum RecoverError {
        NoError,
        InvalidSignature,
        InvalidSignatureLength,
        InvalidSignatureS,
        InvalidSignatureV // Deprecated in v4.8
    }

    function _throwError(RecoverError error) private pure {
        if (error == RecoverError.NoError) {
            return; // no error: do nothing
        } else if (error == RecoverError.InvalidSignature) {
            revert("ECDSA: invalid signature");
        } else if (error == RecoverError.InvalidSignatureLength) {
            revert("ECDSA: invalid signature length");
        } else if (error == RecoverError.InvalidSignatureS) {
            revert("ECDSA: invalid signature 's' value");
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature` or error string. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     *
     * Documentation for signature generation:
     * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
     * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
     *
     * _Available since v4.3._
     */
    function tryRecover(bytes32 hash, bytes memory signature) internal pure returns (address, RecoverError) {
        if (signature.length == 65) {
            bytes32 r;
            bytes32 s;
            uint8 v;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            /// @solidity memory-safe-assembly
            assembly {
                r := mload(add(signature, 0x20))
                s := mload(add(signature, 0x40))
                v := byte(0, mload(add(signature, 0x60)))
            }
            return tryRecover(hash, v, r, s);
        } else {
            return (address(0), RecoverError.InvalidSignatureLength);
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature`. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     */
    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, signature);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `r` and `vs` short-signature fields separately.
     *
     * See https://eips.ethereum.org/EIPS/eip-2098[EIP-2098 short signatures]
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address, RecoverError) {
        bytes32 s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
        uint8 v = uint8((uint256(vs) >> 255) + 27);
        return tryRecover(hash, v, r, s);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `r and `vs` short-signature fields separately.
     *
     * _Available since v4.2._
     */
    function recover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, r, vs);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
     * `r` and `s` signature fields separately.
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address, RecoverError) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
            return (address(0), RecoverError.InvalidSignatureS);
        }

        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(hash, v, r, s);
        if (signer == address(0)) {
            return (address(0), RecoverError.InvalidSignature);
        }

        return (signer, RecoverError.NoError);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `v`,
     * `r` and `s` signature fields separately.
     */
    function recover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, v, r, s);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
        // 32 is the length in bytes of hash,
        // enforced by the type signature above
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from `s`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes memory s) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n", Strings.toString(s.length), s));
    }

    /**
     * @dev Returns an Ethereum Signed Typed Data, created from a
     * `domainSeparator` and a `structHash`. This produces hash corresponding
     * to the one signed with the
     * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`]
     * JSON-RPC method as part of EIP-712.
     *
     * See {recover}.
     */
    function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
    }
}

// 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);
    }
}

// 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/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);
    }
}