// File: /contracts/SwapCore.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.8.19;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/utils/math/Math.sol";
import "./PriceOracleInterface.sol";
import "./Withdrawable.sol";

using SafeERC20 for IERC20;

abstract contract IERC20Extented is IERC20 {
    function decimals() virtual public view returns (uint8);
}

contract SwapCore is Ownable, Withdrawable {
    address private priceOracle;
    bool private isPaused = true;

    uint256 swapFee = 0;
    uint256 private statisticsTotalSwaps = 0;
    uint256 private statisticsTotalValueSwappedBase = 0;
    uint256 private statisticsTotalValueSwappedPair = 0;
    uint256 private statisticsFeesAccruedBase = 0;
    uint256 private statisticsFeesAccruedPair = 0;
    uint256 private minimumBaseTokenPerSwap = 0;
    uint256 private maximumBaseTokenPerSwap = 0;
    uint256 private minimumPairTokenPerSwap = 0;
    uint256 private maximumPairTokenPerSwap = 0;
    address private baseTokenContract = address(0);
    uint8 private baseTokenDecimals = 0;
    uint8 private pairTokenDecimals = 0;
    address private pairTokenContract = address(0);

    event BaseTokenContractChanged(address previous, address currentAddress);
    event PairTokenContractChanged(address previous, address currentAddress);

    event debugString(string  message );
    event debugNumber(uint256  message );

    event SwapPaused();
    event SwapResumed();
    event FeeConfigurationChanged(uint256 perviousfee, uint256 newfee);
    event BaseTokenMinimumLimitChanged(
        uint256 previousminimum,
        uint256 currentminimum
    );
    event BaseTokenMaximumLimitChanged(
        uint256 previousmaximum,
        uint256 currentmaximum
    );
    event PairTokenMinimumLimitChanged(
        uint256 previousminimum,
        uint256 currentminimum
    );
    event PairTokenMaximumLimitChanged(
        uint256 previousmaximum,
        uint256 currentmaximum
    );

    function pause() public onlyOwner {
        require(isPaused == false);
        isPaused = true;
        emit SwapPaused();
    }

    function resume() public onlyOwner {
        require(isPaused == true);
        isPaused = false;
        emit SwapResumed();
    }

    function isSwapPaused() public view returns (bool) {
        return isPaused;
    }

    function setBaseTokenContract(address contractAddress) public onlyOwner {
        address previous = baseTokenContract;
        baseTokenContract = contractAddress;
        emit BaseTokenContractChanged(previous, baseTokenContract);

        if (contractAddress != address(0)) {
            IERC20Extented targetContract = IERC20Extented(contractAddress);
            baseTokenDecimals = targetContract.decimals();
        }
        emit debugNumber(baseTokenDecimals);
    }

    function setPairTokenContract(address contractAddress) public onlyOwner {
        address previous = pairTokenContract;
        pairTokenContract = contractAddress;
        emit PairTokenContractChanged(previous, pairTokenContract);

        if (contractAddress != address(0)) {
            IERC20Extented targetContract = IERC20Extented(contractAddress);
            pairTokenDecimals = targetContract.decimals();
        }

        emit debugNumber(pairTokenDecimals);
    }

    function SetMinimumBaseTokenPerSwap(uint256 minimum) public onlyOwner {
        uint256 previous = minimumBaseTokenPerSwap;
        minimumBaseTokenPerSwap = minimum;
        emit BaseTokenMinimumLimitChanged(previous, minimum);
    }

    function SetMaximumBaseTokenPerSwap(uint256 maximum) public onlyOwner {
        uint256 previous = maximumBaseTokenPerSwap;
        maximumBaseTokenPerSwap = maximum;
        emit BaseTokenMaximumLimitChanged(previous, maximum);
    }

    function SetMinimumPairTokenPerSwap(uint256 minimum) public onlyOwner {
        uint256 previous = minimumPairTokenPerSwap;
        minimumPairTokenPerSwap = minimum;
        emit PairTokenMinimumLimitChanged(previous, minimum);
    }

    function SetMaximumPairTokenPerSwap(uint256 maximum) public onlyOwner {
        uint256 previous = maximumPairTokenPerSwap;
        maximumPairTokenPerSwap = maximum;
        emit PairTokenMaximumLimitChanged(previous, maximum);
    }

    function setSwapFee(uint256 percentile) public onlyOwner {
        //
        // The maximum fee can be 99.99% so that would be 99.99 * 10^2 - 9999
        // require(
        //     percentile <= 9999,
        //     "Fee can be from 0% to 99.99% or 9999 as uint"
        // );
        uint256 previousFee = swapFee;
        swapFee = percentile;
        emit FeeConfigurationChanged(previousFee, percentile);
    }

    function getSwapFee() public view returns (uint256) {
        return swapFee;
    }

    function setPriceOracle(address priceOracleAddress) public onlyOwner {
        priceOracle = priceOracleAddress;
    }

    function abs(int x) private pure returns (int) {
        return x >= 0 ? x : -x;
    }

    function quoteSwapToBase(
        uint256 baseQuantity
    )
        public
        view
        returns (
            uint256 quantity,
            uint8 quantityDecimals,
            uint quoteUsed,
            uint8 quoteDecimals
        )
    {
        require(isPaused == false, "Swap is paused, cannot quote swaps");
        require(
            priceOracle != address(0),
            "Price Oracle not configured. Cannot swap"
        );
        require(
            baseTokenContract != address(0),
            "Base Token contract not configured. Cannot swap"
        );
        require(
            pairTokenContract != address(0),
            "Pair Token contract not configured. Cannot swap"
        );
        require(
            baseQuantity >= minimumBaseTokenPerSwap,
            "Swap bellow minimum allowed for base"
        );
        require(
            baseQuantity <= maximumBaseTokenPerSwap,
            "Swap above maximum allowed for base"
        );

        PriceOracleInterface oracle = PriceOracleInterface(priceOracle);

        PriceOracleStructures.PriceOracleData memory quote = oracle.getQuote();

        require(
            oracle.IsQuoteTooDeviant(quote) == false,
            "Quote is too old, cannot swap now"
        );
        require(
            oracle.IsQuoteTooOld(quote) == false,
            "Quote is too old, cannot swap now"
        );

        uint powerDifferential = quote.decimals - baseTokenDecimals;

        uint256 quoteNormalized2 = Math.mulDiv((uint256) (quote.answer), 1, 10 ** powerDifferential);

        uint256 pairQuantityWithoutFee =
        
        Math.mulDiv(baseQuantity, 
                    quoteNormalized2, 
                    10 ** baseTokenDecimals);

        uint256 fees = Math.mulDiv(pairQuantityWithoutFee, swapFee, 10**4);

        return (
            pairQuantityWithoutFee + fees,
            baseTokenDecimals,
            uint(quote.answer),
            quote.decimals
        );
    }

    function divide(uint256 a, uint256 b) private pure returns (uint256) {
        require(b != 0, "division by zero will result in infinity.");
        return (a * 1e18) / b;
    }

    function quoteSwapToPair(
        uint256 baseQuantity
    )
        public
        view
        returns (
            uint256 quantity,
            uint8 quantityDecimals,
            uint quoteUsed,
            uint8 quoteDecimals
        )
    {
        require(
            priceOracle != address(0),
            "Price Oracle not configured. Cannot swap"
        );
        require(
            baseQuantity >= minimumPairTokenPerSwap,
            "Swap bellow minimum allowed for pair"
        );
        require(
            baseQuantity <= maximumPairTokenPerSwap,
            "Swap above maximum allowed for pair"
        );

        PriceOracleInterface oracle = PriceOracleInterface(priceOracle);

        PriceOracleStructures.PriceOracleData memory quote = oracle.getQuote();

        require(
            oracle.IsQuoteTooDeviant(quote) == false,
            "Quote is too old, cannot swap now"
        );
        require(
            oracle.IsQuoteTooOld(quote) == false,
            "Quote is too old, cannot swap now"
        );
  
        uint powerDifferential = quote.decimals - pairTokenDecimals;

        uint256 pairQuantityWithoutFee = 
           Math.mulDiv(baseQuantity, 
           ((uint)(quote.answer) / 10 ** powerDifferential),  10 ** pairTokenDecimals);
        
        uint256 fees = Math.mulDiv(pairQuantityWithoutFee, swapFee, 10**4);

        return (
            pairQuantityWithoutFee + fees,
            pairTokenDecimals,
            uint(quote.answer),
            quote.decimals
        );
    }

    function SwapToBase(uint256 baseQuantity) public {
        require(isPaused == false, "Swap is paused, cannot quote swaps");
        require(
            priceOracle != address(0),
            "Price Oracle not configured. Cannot swap"
        );
        require(
            baseTokenContract != address(0),
            "Base Token contract not configured. Cannot swap"
        );
        require(
            pairTokenContract != address(0),
            "Pair Token contract not configured. Cannot swap"
        );
        require(
            baseQuantity >= minimumBaseTokenPerSwap,
            "Swap bellow minimum allowed for base"
        );
        require(
            baseQuantity <= maximumBaseTokenPerSwap,
            "Swap above maximum allowed for base"
        );
        require(
            baseTokenDecimals != 0,
            "Base token decimals is 0 thus invalid"
        );
        require(
            pairTokenDecimals != 0,
            "Base token decimals is 0 thus invalid"
        );
        require(
            pairTokenDecimals == baseTokenDecimals,
            "Base token decimals and pair token decimals do not match"
        );

        PriceOracleInterface oracle = PriceOracleInterface(priceOracle);

        PriceOracleStructures.PriceOracleData memory quote = oracle.getQuote();     

        require(        
            oracle.IsQuoteTooDeviant(quote) == false,        
            "Quote is too old, cannot swap now"        
        );
        
        require(        
            oracle.IsQuoteTooOld(quote) == false,        
            "Quote is too old, cannot swap now"        
        );

        uint powerDifferential = quote.decimals - baseTokenDecimals;

        uint256 quoteNormalized2 = Math.mulDiv((uint256) (quote.answer), 1, 10 ** powerDifferential);

        uint256 pairQuantityWithoutFee =
        
        Math.mulDiv(baseQuantity, 
                    quoteNormalized2, 
                    10 ** baseTokenDecimals);

        uint256 fees = Math.mulDiv(pairQuantityWithoutFee, swapFee, 10**4);

        statisticsFeesAccruedPair += fees;
        statisticsTotalSwaps++;

        IERC20 baseContract = IERC20(baseTokenContract);
        IERC20 pairContract = IERC20(pairTokenContract);

        pairContract.safeTransferFrom(
            msg.sender,
            address(this),
            pairQuantityWithoutFee + fees
        );
        baseContract.safeTransfer(msg.sender, baseQuantity);

    }

    function SwapToPair(uint256 baseQuantity) public {
        require(isPaused == false, "Swap is paused, cannot quote swaps");
        require(
            priceOracle != address(0),
            "Price Oracle not configured. Cannot swap"
        );
        require(
            baseTokenContract != address(0),
            "Base Token contract not configured. Cannot swap"
        );
        require(
            pairTokenContract != address(0),
            "Pair Token contract not configured. Cannot swap"
        );
        require(
            baseQuantity >= minimumBaseTokenPerSwap,
            "Swap bellow minimum allowed for base"
        );
        require(
            baseQuantity <= maximumBaseTokenPerSwap,
            "Swap above maximum allowed for base"
        );

        require(
            baseTokenDecimals != 0,
            "Base token decimals is 0 thus invalid"
        );
        require(
            pairTokenDecimals != 0,
            "Base token decimals is 0 thus invalid"
        );
        require(
            pairTokenDecimals == baseTokenDecimals,
            "Base token decimals and pair token decimals do not match"
        );

        PriceOracleInterface oracle = PriceOracleInterface(priceOracle);

        PriceOracleStructures.PriceOracleData memory quote = oracle.getQuote();     
         require(
             oracle.IsQuoteTooDeviant(quote) == false,
             "Quote is too old, cannot swap now"
         );
         require(
             oracle.IsQuoteTooOld(quote) == false,
             "Quote is too old, cannot swap now"
         );

        
        uint powerDifferential = quote.decimals - pairTokenDecimals;

        uint256 pairQuantityWithoutFee = 
           Math.mulDiv(baseQuantity, 
           ((uint)(quote.answer) / 10 ** powerDifferential),  10 ** pairTokenDecimals);
        
        uint256 fees = Math.mulDiv(pairQuantityWithoutFee, swapFee, 10**4);

        statisticsFeesAccruedPair += fees;
        statisticsTotalSwaps++;

        IERC20 baseContract = IERC20(baseTokenContract);
        IERC20 pairContract = IERC20(pairTokenContract);

        baseContract.safeTransferFrom(msg.sender, address(this), baseQuantity);
        pairContract.safeTransfer(msg.sender, pairQuantityWithoutFee - fees);
    }

    function getFeesAccrued()
        public
        view
        onlyOwner
        returns (uint256 feesAccruedInBase, uint256 feesAccruedInPair)
    {
        return (statisticsFeesAccruedBase, statisticsFeesAccruedPair);
    }

    function getLiquidityStatus()
        public
        view
        returns (
            uint256 baseLiquidity,
            uint8 baseDecimals,
            uint256 pairLiquidity,
            uint8 pairDecimals
        )
    {
        require(
            baseTokenContract != address(0),
            "Base Token contract not configured."
        );
        require(
            pairTokenContract != address(0),
            "Pair Token contract not configured."
        );

        IERC20 baseContract = IERC20(baseTokenContract);
        IERC20 pairContract = IERC20(pairTokenContract);

        return (
            baseContract.balanceOf(address(this)),
            baseTokenDecimals,
            pairContract.balanceOf(address(this)),
            pairTokenDecimals
        );
    }

    receive() external payable {}

    function removeThisOnProd() public onlyOwner
    {

    }
}

// File: /contracts/Withdrawable.sol



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

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

contract Withdrawable is Ownable {
 
  event ERC20Withdrawal(address tokenContract, uint256 tokenQuantity, address destinationAddress);
  event ETHWithdrawal(uint256 ethQuantity, address destinationAddress);

  function withdrawERC20(address tokenContract, uint256 tokenQuantity, address destinationAddress) public onlyOwner  {

    require(tokenContract != address(0));
    require(tokenQuantity != 0);
    require(destinationAddress != address(0));

    IERC20 contractInterface = IERC20(tokenContract);
    //contractInterface.approve(address(this), tokenQuantity);
    contractInterface.transfer(destinationAddress, tokenQuantity);

    emit ERC20Withdrawal(tokenContract,tokenQuantity,destinationAddress);

  }

  function withdrawETH(uint256 ethQuantity, address destinationAddress) public onlyOwner {
    
    require(ethQuantity != 0);
    require(destinationAddress != address(0));

    (bool success, ) = destinationAddress.call{value: ethQuantity}("");

    if (success)
      emit ETHWithdrawal(ethQuantity, destinationAddress);

  }

}

// File: /contracts/PriceOracleInterface.sol



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

interface PriceOracleInterface
{
     function getQuote() external view returns(PriceOracleStructures.PriceOracleData memory);

     function IsQuoteTooDeviant(PriceOracleStructures.PriceOracleData memory quote) external view returns(bool) ;

     function IsQuoteTooOld(PriceOracleStructures.PriceOracleData memory quote) external view returns(bool) ;
     
}

library PriceOracleStructures
{
    struct PriceOracleData
          {
            uint8 decimals;
            uint80 roundId;
            int256 answer;
            uint256 startedAt;
            uint256 updatedAt; 
            uint80 answeredInRound;
          }
}
// File: @openzeppelin/contracts/utils/math/Math.sol



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

pragma solidity ^0.8.0;

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

    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a > b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow.
        return (a & b) + (a ^ b) / 2;
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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



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

pragma solidity ^0.8.0;

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

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

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



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

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     *
     * Furthermore, `isContract` will also return true if the target contract within
     * the same transaction is already scheduled for destruction by `SELFDESTRUCT`,
     * which only has an effect at the end of a transaction.
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.8.0/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, "Address: low-level call failed");
    }

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

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

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

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

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

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

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

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
            // The easiest way to bubble the revert reason is using memory via assembly
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.3) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/IERC20Permit.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

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

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

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

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

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

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

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

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

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address-functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        require(returndata.length == 0 || abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     *
     * This is a variant of {_callOptionalReturn} that silents catches all reverts and returns a bool instead.
     */
    function _callOptionalReturnBool(IERC20 token, bytes memory data) private returns (bool) {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We cannot use {Address-functionCall} here since this should return false
        // and not revert is the subcall reverts.

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

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



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

pragma solidity ^0.8.0;

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

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

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

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



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

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

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

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 amount) external returns (bool);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (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. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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);
    }
}