contract BaseJumpRateModelV2 {
    using SafeMath for uint256;

    event NewInterestParams(
        uint256 baseRatePerBlock,
        uint256 multiplierPerBlock,
        uint256 jumpMultiplierPerBlock,
        uint256 kink
    );

    /**
     * @notice The address of the owner, i.e. the Timelock contract, which can update parameters directly
     */
    address public owner;

    /**
     * @notice The approximate number of blocks per year that is assumed by the interest rate model
     */
    uint256 public constant blocksPerYear = 2102400;

    /**
     * @notice The multiplier of utilization rate that gives the slope of the interest rate
     */
    uint256 public multiplierPerBlock;

    /**
     * @notice The base interest rate which is the y-intercept when utilization rate is 0
     */
    uint256 public baseRatePerBlock;

    /**
     * @notice The multiplierPerBlock after hitting a specified utilization point
     */
    uint256 public jumpMultiplierPerBlock;

    /**
     * @notice The utilization point at which the jump multiplier is applied
     */
    uint256 public kink;

    /**
     * @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 multiplierPerBlock after hitting a specified utilization point
     * @param kink_ The utilization point at which the jump multiplier is applied
     * @param owner_ The address of the owner, i.e. the Timelock contract (which has the ability to update parameters directly)
     */
    constructor(
        uint256 baseRatePerYear,
        uint256 multiplierPerYear,
        uint256 jumpMultiplierPerYear,
        uint256 kink_,
        address owner_
    ) internal {
        owner = owner_;

        updateJumpRateModelInternal(
            baseRatePerYear,
            multiplierPerYear,
            jumpMultiplierPerYear,
            kink_
        );
    }

    /**
     * @notice Update the parameters of the interest rate model (only callable by owner, i.e. Timelock)
     * @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 multiplierPerBlock after hitting a specified utilization point
     * @param kink_ The utilization point at which the jump multiplier is applied
     */
    function updateJumpRateModel(
        uint256 baseRatePerYear,
        uint256 multiplierPerYear,
        uint256 jumpMultiplierPerYear,
        uint256 kink_
    ) external {
        require(msg.sender == owner, "only the owner may call this function.");

        updateJumpRateModelInternal(
            baseRatePerYear,
            multiplierPerYear,
            jumpMultiplierPerYear,
            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(
        uint256 cash,
        uint256 borrows,
        uint256 reserves
    ) public pure returns (uint256) {
        // 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 block, 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 block as a mantissa (scaled by 1e18)
     */
    function getBorrowRateInternal(
        uint256 cash,
        uint256 borrows,
        uint256 reserves
    ) internal view returns (uint256) {
        uint256 util = utilizationRate(cash, borrows, reserves);

        if (util <= kink) {
            return util.mul(multiplierPerBlock).div(1e18).add(baseRatePerBlock);
        } else {
            uint256 normalRate =
                kink.mul(multiplierPerBlock).div(1e18).add(baseRatePerBlock);
            uint256 excessUtil = util.sub(kink);
            return
                excessUtil.mul(jumpMultiplierPerBlock).div(1e18).add(
                    normalRate
                );
        }
    }

    /**
     * @notice Calculates the current supply rate per block
     * @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 block as a mantissa (scaled by 1e18)
     */
    function getSupplyRate(
        uint256 cash,
        uint256 borrows,
        uint256 reserves,
        uint256 reserveFactorMantissa
    ) public view returns (uint256) {
        uint256 oneMinusReserveFactor =
            uint256(1e18).sub(reserveFactorMantissa);
        uint256 borrowRate = getBorrowRateInternal(cash, borrows, reserves);
        uint256 rateToPool = borrowRate.mul(oneMinusReserveFactor).div(1e18);
        return
            utilizationRate(cash, borrows, reserves).mul(rateToPool).div(1e18);
    }

    /**
     * @notice Internal function to update the parameters of the 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 multiplierPerBlock after hitting a specified utilization point
     * @param kink_ The utilization point at which the jump multiplier is applied
     */
    function updateJumpRateModelInternal(
        uint256 baseRatePerYear,
        uint256 multiplierPerYear,
        uint256 jumpMultiplierPerYear,
        uint256 kink_
    ) internal {
        baseRatePerBlock = baseRatePerYear.div(blocksPerYear);
        multiplierPerBlock = (multiplierPerYear.mul(1e18)).div(
            blocksPerYear.mul(kink_)
        );
        jumpMultiplierPerBlock = jumpMultiplierPerYear.div(blocksPerYear);
        kink = kink_;

        emit NewInterestParams(
            baseRatePerBlock,
            multiplierPerBlock,
            jumpMultiplierPerBlock,
            kink
        );
    }
}
/**
 * @title Logic for Compound's JumpRateModel Contract V2.
 * @author Compound (modified by Dharma Labs, refactored by Arr00)
 * @notice Version 2 modifies Version 1 by enabling updateable parameters.
 */
function updateJumpRateModel(
    uint256 baseRatePerYear,
    uint256 multiplierPerYear,
    uint256 jumpMultiplierPerYear,
    uint256 kink_
) external {
    require(msg.sender == owner, "only the owner may call this function.");

    updateJumpRateModelInternal(
        baseRatePerYear,
        multiplierPerYear,
        jumpMultiplierPerYear,
        kink_
    );
}

/**
 * @notice Update the parameters of the interest rate model (only callable by owner, i.e. Timelock)
 * @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 multiplierPerBlock after hitting a specified utilization point
 * @param kink_ The utilization point at which the jump multiplier is applied
 */