Contract Source Code:

// SPDX-License-Identifier: BSD-3-Clause
pragma solidity 0.8.19;

/**
 * @title Moonwell's InterestRateModel Interface
 * @author Moonwell
 */
abstract contract InterestRateModel {
    /// @notice Indicator that this is an InterestRateModel contract (for inspection)
    bool public constant isInterestRateModel = true;

    /**
     * @notice Calculates the current borrow interest rate per timestamp
     * @param cash The total amount of cash the market has
     * @param borrows The total amount of borrows the market has outstanding
     * @param reserves The total amount of reserves the market has
     * @return The borrow rate per timestamp (as a percentage, and scaled by 1e18)
     */
    function getBorrowRate(
        uint cash,
        uint borrows,
        uint reserves
    ) external view virtual returns (uint);

    /**
     * @notice Calculates the current supply interest rate per timestamp
     * @param cash The total amount of cash the market has
     * @param borrows The total amount of borrows the market has outstanding
     * @param reserves The total amount of reserves the market has
     * @param reserveFactorMantissa The current reserve factor the market has
     * @return The supply rate per timestamp (as a percentage, and scaled by 1e18)
     */
    function getSupplyRate(
        uint cash,
        uint borrows,
        uint reserves,
        uint reserveFactorMantissa
    ) external view virtual returns (uint);
}

// SPDX-License-Identifier: BSD-3-Clause
pragma solidity 0.8.19;

import "./InterestRateModel.sol";
import "./SafeMath.sol";

/**
 * @title Moonwell's JumpRateModel Contract
 * @author Compound
 * @author Moonwell
 */
contract JumpRateModel is InterestRateModel {
    using SafeMath for uint;

    event NewInterestParams(
        uint baseRatePerTimestamp,
        uint multiplierPerTimestamp,
        uint jumpMultiplierPerTimestamp,
        uint kink
    );

    /**
     * @notice The approximate number of timestamps per year that is assumed by the interest rate model
     */
    uint public constant timestampsPerYear = 60 * 60 * 24 * 365;

    /**
     * @notice The multiplier of utilization rate that gives the slope of the interest rate
     */
    uint public multiplierPerTimestamp;

    /**
     * @notice The base interest rate which is the y-intercept when utilization rate is 0
     */
    uint public baseRatePerTimestamp;

    /**
     * @notice The multiplierPerTimestamp after hitting a specified utilization point
     */
    uint public jumpMultiplierPerTimestamp;

    /**
     * @notice The utilization point at which the jump multiplier is applied
     */
    uint public kink;

    /// @dev we know that we do not need to use safemath, however safemath is still used for safety
    /// and to not modify existing code.

    /**
     * @notice Construct an interest rate model
     * @param baseRatePerYear The approximate target base APR, as a mantissa (scaled by 1e18)
     * @param multiplierPerYear The rate of increase in interest rate wrt utilization (scaled by 1e18)
     * @param jumpMultiplierPerYear The multiplierPerTimestamp after hitting a specified utilization point
     * @param kink_ The utilization point at which the jump multiplier is applied
     */
    constructor(
        uint baseRatePerYear,
        uint multiplierPerYear,
        uint jumpMultiplierPerYear,
        uint kink_
    ) {
        baseRatePerTimestamp = baseRatePerYear
            .mul(1e18)
            .div(timestampsPerYear)
            .div(1e18);
        multiplierPerTimestamp = multiplierPerYear
            .mul(1e18)
            .div(timestampsPerYear)
            .div(1e18);
        jumpMultiplierPerTimestamp = jumpMultiplierPerYear
            .mul(1e18)
            .div(timestampsPerYear)
            .div(1e18);
        kink = kink_;

        emit NewInterestParams(
            baseRatePerTimestamp,
            multiplierPerTimestamp,
            jumpMultiplierPerTimestamp,
            kink
        );
    }

    /**
     * @notice Calculates the utilization rate of the market: `borrows / (cash + borrows - reserves)`
     * @param cash The amount of cash in the market
     * @param borrows The amount of borrows in the market
     * @param reserves The amount of reserves in the market (currently unused)
     * @return The utilization rate as a mantissa between [0, 1e18]
     */
    function utilizationRate(
        uint cash,
        uint borrows,
        uint reserves
    ) public pure returns (uint) {
        // Utilization rate is 0 when there are no borrows
        if (borrows == 0) {
            return 0;
        }

        return borrows.mul(1e18).div(cash.add(borrows).sub(reserves));
    }

    /**
     * @notice Calculates the current borrow rate per timestamp, with the error code expected by the market
     * @param cash The amount of cash in the market
     * @param borrows The amount of borrows in the market
     * @param reserves The amount of reserves in the market
     * @return The borrow rate percentage per timestamp as a mantissa (scaled by 1e18)
     */
    function getBorrowRate(
        uint cash,
        uint borrows,
        uint reserves
    ) public view override returns (uint) {
        uint util = utilizationRate(cash, borrows, reserves);

        if (util <= kink) {
            return
                util.mul(multiplierPerTimestamp).div(1e18).add(
                    baseRatePerTimestamp
                );
        } else {
            uint normalRate = kink.mul(multiplierPerTimestamp).div(1e18).add(
                baseRatePerTimestamp
            );
            uint excessUtil = util.sub(kink);
            return
                excessUtil.mul(jumpMultiplierPerTimestamp).div(1e18).add(
                    normalRate
                );
        }
    }

    /**
     * @notice Calculates the current supply rate per timestamp
     * @param cash The amount of cash in the market
     * @param borrows The amount of borrows in the market
     * @param reserves The amount of reserves in the market
     * @param reserveFactorMantissa The current reserve factor for the market
     * @return The supply rate percentage per timestamp as a mantissa (scaled by 1e18)
     */
    function getSupplyRate(
        uint cash,
        uint borrows,
        uint reserves,
        uint reserveFactorMantissa
    ) public view override returns (uint) {
        uint oneMinusReserveFactor = uint(1e18).sub(reserveFactorMantissa);
        uint borrowRate = getBorrowRate(cash, borrows, reserves);
        uint rateToPool = borrowRate.mul(oneMinusReserveFactor).div(1e18);
        return
            utilizationRate(cash, borrows, reserves).mul(rateToPool).div(1e18);
    }
}

// SPDX-License-Identifier: BSD-3-Clause
pragma solidity 0.8.19;

// From https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/Math.sol
// Subject to the MIT license.

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting with custom message on overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, errorMessage);

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on underflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot underflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction underflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on underflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot underflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, errorMessage);

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers.
     * Reverts on division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers.
     * Reverts with custom message on division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}