cf_rate_model.sol

pragma solidity ^0.4.24;
// produced by the Solididy File Flattener (c) David Appleton 2018
// contact : [email protected]
// released under Apache 2.0 licence
contract ErrorReporter {

    /**
      * @dev `error` corresponds to enum Error; `info` corresponds to enum FailureInfo, and `detail` is an arbitrary
      * contract-specific code that enables us to report opaque error codes from upgradeable contracts.
      **/
    event Failure(uint error, uint info, uint detail);

    enum Error {
        NO_ERROR,
        OPAQUE_ERROR, // To be used when reporting errors from upgradeable contracts; the opaque code should be given as `detail` in the `Failure` event
        UNAUTHORIZED,
        INTEGER_OVERFLOW,
        INTEGER_UNDERFLOW,
        DIVISION_BY_ZERO,
        BAD_INPUT,
        TOKEN_INSUFFICIENT_ALLOWANCE,
        TOKEN_INSUFFICIENT_BALANCE,
        TOKEN_TRANSFER_FAILED,
        MARKET_NOT_SUPPORTED,
        SUPPLY_RATE_CALCULATION_FAILED,
        BORROW_RATE_CALCULATION_FAILED,
        TOKEN_INSUFFICIENT_CASH,
        TOKEN_TRANSFER_OUT_FAILED,
        INSUFFICIENT_LIQUIDITY,
        INSUFFICIENT_BALANCE,
        INVALID_COLLATERAL_RATIO,
        MISSING_ASSET_PRICE,
        EQUITY_INSUFFICIENT_BALANCE,
        INVALID_CLOSE_AMOUNT_REQUESTED,
        ASSET_NOT_PRICED,
        INVALID_LIQUIDATION_DISCOUNT,
        INVALID_COMBINED_RISK_PARAMETERS,
        ZERO_ORACLE_ADDRESS,
        CONTRACT_PAUSED
    }

    /*
     * Note: FailureInfo (but not Error) is kept in alphabetical order
     *       This is because FailureInfo grows significantly faster, and
     *       the order of Error has some meaning, while the order of FailureInfo
     *       is entirely arbitrary.
     */
    enum FailureInfo {
        ACCEPT_ADMIN_PENDING_ADMIN_CHECK,
        BORROW_ACCOUNT_LIQUIDITY_CALCULATION_FAILED,
        BORROW_ACCOUNT_SHORTFALL_PRESENT,
        BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED,
        BORROW_AMOUNT_LIQUIDITY_SHORTFALL,
        BORROW_AMOUNT_VALUE_CALCULATION_FAILED,
        BORROW_CONTRACT_PAUSED,
        BORROW_MARKET_NOT_SUPPORTED,
        BORROW_NEW_BORROW_INDEX_CALCULATION_FAILED,
        BORROW_NEW_BORROW_RATE_CALCULATION_FAILED,
        BORROW_NEW_SUPPLY_INDEX_CALCULATION_FAILED,
        BORROW_NEW_SUPPLY_RATE_CALCULATION_FAILED,
        BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED,
        BORROW_NEW_TOTAL_BORROW_CALCULATION_FAILED,
        BORROW_NEW_TOTAL_CASH_CALCULATION_FAILED,
        BORROW_ORIGINATION_FEE_CALCULATION_FAILED,
        BORROW_TRANSFER_OUT_FAILED,
        EQUITY_WITHDRAWAL_AMOUNT_VALIDATION,
        EQUITY_WITHDRAWAL_CALCULATE_EQUITY,
        EQUITY_WITHDRAWAL_MODEL_OWNER_CHECK,
        EQUITY_WITHDRAWAL_TRANSFER_OUT_FAILED,
        LIQUIDATE_ACCUMULATED_BORROW_BALANCE_CALCULATION_FAILED,
        LIQUIDATE_ACCUMULATED_SUPPLY_BALANCE_CALCULATION_FAILED_BORROWER_COLLATERAL_ASSET,
        LIQUIDATE_ACCUMULATED_SUPPLY_BALANCE_CALCULATION_FAILED_LIQUIDATOR_COLLATERAL_ASSET,
        LIQUIDATE_AMOUNT_SEIZE_CALCULATION_FAILED,
        LIQUIDATE_BORROW_DENOMINATED_COLLATERAL_CALCULATION_FAILED,
        LIQUIDATE_CLOSE_AMOUNT_TOO_HIGH,
        LIQUIDATE_CONTRACT_PAUSED,
        LIQUIDATE_DISCOUNTED_REPAY_TO_EVEN_AMOUNT_CALCULATION_FAILED,
        LIQUIDATE_NEW_BORROW_INDEX_CALCULATION_FAILED_BORROWED_ASSET,
        LIQUIDATE_NEW_BORROW_INDEX_CALCULATION_FAILED_COLLATERAL_ASSET,
        LIQUIDATE_NEW_BORROW_RATE_CALCULATION_FAILED_BORROWED_ASSET,
        LIQUIDATE_NEW_SUPPLY_INDEX_CALCULATION_FAILED_BORROWED_ASSET,
        LIQUIDATE_NEW_SUPPLY_INDEX_CALCULATION_FAILED_COLLATERAL_ASSET,
        LIQUIDATE_NEW_SUPPLY_RATE_CALCULATION_FAILED_BORROWED_ASSET,
        LIQUIDATE_NEW_TOTAL_BORROW_CALCULATION_FAILED_BORROWED_ASSET,
        LIQUIDATE_NEW_TOTAL_CASH_CALCULATION_FAILED_BORROWED_ASSET,
        LIQUIDATE_NEW_TOTAL_SUPPLY_BALANCE_CALCULATION_FAILED_BORROWER_COLLATERAL_ASSET,
        LIQUIDATE_NEW_TOTAL_SUPPLY_BALANCE_CALCULATION_FAILED_LIQUIDATOR_COLLATERAL_ASSET,
        LIQUIDATE_FETCH_ASSET_PRICE_FAILED,
        LIQUIDATE_TRANSFER_IN_FAILED,
        LIQUIDATE_TRANSFER_IN_NOT_POSSIBLE,
        REPAY_BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED,
        REPAY_BORROW_CONTRACT_PAUSED,
        REPAY_BORROW_NEW_BORROW_INDEX_CALCULATION_FAILED,
        REPAY_BORROW_NEW_BORROW_RATE_CALCULATION_FAILED,
        REPAY_BORROW_NEW_SUPPLY_INDEX_CALCULATION_FAILED,
        REPAY_BORROW_NEW_SUPPLY_RATE_CALCULATION_FAILED,
        REPAY_BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED,
        REPAY_BORROW_NEW_TOTAL_BORROW_CALCULATION_FAILED,
        REPAY_BORROW_NEW_TOTAL_CASH_CALCULATION_FAILED,
        REPAY_BORROW_TRANSFER_IN_FAILED,
        REPAY_BORROW_TRANSFER_IN_NOT_POSSIBLE,
        SET_ASSET_PRICE_CHECK_ORACLE,
        SET_MARKET_INTEREST_RATE_MODEL_OWNER_CHECK,
        SET_ORACLE_OWNER_CHECK,
        SET_ORIGINATION_FEE_OWNER_CHECK,
        SET_PAUSED_OWNER_CHECK,
        SET_PENDING_ADMIN_OWNER_CHECK,
        SET_RISK_PARAMETERS_OWNER_CHECK,
        SET_RISK_PARAMETERS_VALIDATION,
        SUPPLY_ACCUMULATED_BALANCE_CALCULATION_FAILED,
        SUPPLY_CONTRACT_PAUSED,
        SUPPLY_MARKET_NOT_SUPPORTED,
        SUPPLY_NEW_BORROW_INDEX_CALCULATION_FAILED,
        SUPPLY_NEW_BORROW_RATE_CALCULATION_FAILED,
        SUPPLY_NEW_SUPPLY_INDEX_CALCULATION_FAILED,
        SUPPLY_NEW_SUPPLY_RATE_CALCULATION_FAILED,
        SUPPLY_NEW_TOTAL_BALANCE_CALCULATION_FAILED,
        SUPPLY_NEW_TOTAL_CASH_CALCULATION_FAILED,
        SUPPLY_NEW_TOTAL_SUPPLY_CALCULATION_FAILED,
        SUPPLY_TRANSFER_IN_FAILED,
        SUPPLY_TRANSFER_IN_NOT_POSSIBLE,
        SUPPORT_MARKET_FETCH_PRICE_FAILED,
        SUPPORT_MARKET_OWNER_CHECK,
        SUPPORT_MARKET_PRICE_CHECK,
        SUSPEND_MARKET_OWNER_CHECK,
        WITHDRAW_ACCOUNT_LIQUIDITY_CALCULATION_FAILED,
        WITHDRAW_ACCOUNT_SHORTFALL_PRESENT,
        WITHDRAW_ACCUMULATED_BALANCE_CALCULATION_FAILED,
        WITHDRAW_AMOUNT_LIQUIDITY_SHORTFALL,
        WITHDRAW_AMOUNT_VALUE_CALCULATION_FAILED,
        WITHDRAW_CAPACITY_CALCULATION_FAILED,
        WITHDRAW_CONTRACT_PAUSED,
        WITHDRAW_NEW_BORROW_INDEX_CALCULATION_FAILED,
        WITHDRAW_NEW_BORROW_RATE_CALCULATION_FAILED,
        WITHDRAW_NEW_SUPPLY_INDEX_CALCULATION_FAILED,
        WITHDRAW_NEW_SUPPLY_RATE_CALCULATION_FAILED,
        WITHDRAW_NEW_TOTAL_BALANCE_CALCULATION_FAILED,
        WITHDRAW_NEW_TOTAL_SUPPLY_CALCULATION_FAILED,
        WITHDRAW_TRANSFER_OUT_FAILED,
        WITHDRAW_TRANSFER_OUT_NOT_POSSIBLE
    }


    /**
      * @dev use this when reporting a known error from the money market or a non-upgradeable collaborator
      */
    function fail(Error err, FailureInfo info) internal returns (uint) {
        emit Failure(uint(err), uint(info), 0);

        return uint(err);
    }


    /**
      * @dev use this when reporting an opaque error from an upgradeable collaborator contract
      */
    function failOpaque(FailureInfo info, uint opaqueError) internal returns (uint) {
        emit Failure(uint(Error.OPAQUE_ERROR), uint(info), opaqueError);

        return uint(Error.OPAQUE_ERROR);
    }

}
contract InterestRateModel {

    /**
      * @notice Gets the current supply interest rate based on the given asset, total cash and total borrows
      * @dev The return value should be scaled by 1e18, thus a return value of
      *      `(true, 1000000000000)` implies an interest rate of 0.000001 or 0.0001% *per block*.
      * @param asset The asset to get the interest rate of
      * @param cash The total cash of the asset in the market
      * @param borrows The total borrows of the asset in the market
      * @return Success or failure and the supply interest rate per block scaled by 10e18
      */
    function getSupplyRate(address asset, uint cash, uint borrows) public view returns (uint, uint);

    /**
      * @notice Gets the current borrow interest rate based on the given asset, total cash and total borrows
      * @dev The return value should be scaled by 1e18, thus a return value of
      *      `(true, 1000000000000)` implies an interest rate of 0.000001 or 0.0001% *per block*.
      * @param asset The asset to get the interest rate of
      * @param cash The total cash of the asset in the market
      * @param borrows The total borrows of the asset in the market
      * @return Success or failure and the borrow interest rate per block scaled by 10e18
      */
    function getBorrowRate(address asset, uint cash, uint borrows) public view returns (uint, uint);
}
contract CarefulMath is ErrorReporter {

    /**
    * @dev Multiplies two numbers, returns an error on overflow.
    */
    function mul(uint a, uint b) internal pure returns (Error, uint) {
        if (a == 0) {
            return (Error.NO_ERROR, 0);
        }

        uint c = a * b;

        if (c / a != b) {
            return (Error.INTEGER_OVERFLOW, 0);
        } else {
            return (Error.NO_ERROR, c);
        }
    }

    /**
    * @dev Integer division of two numbers, truncating the quotient.
    */
    function div(uint a, uint b) internal pure returns (Error, uint) {
        if (b == 0) {
            return (Error.DIVISION_BY_ZERO, 0);
        }

        return (Error.NO_ERROR, a / b);
    }

    /**
    * @dev Subtracts two numbers, returns an error on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint a, uint b) internal pure returns (Error, uint) {
        if (b <= a) {
            return (Error.NO_ERROR, a - b);
        } else {
            return (Error.INTEGER_UNDERFLOW, 0);
        }
    }

    /**
    * @dev Adds two numbers, returns an error on overflow.
    */
    function add(uint a, uint b) internal pure returns (Error, uint) {
        uint c = a + b;

        if (c >= a) {
            return (Error.NO_ERROR, c);
        } else {
            return (Error.INTEGER_OVERFLOW, 0);
        }
    }

    /**
    * @dev add a and b and then subtract c
    */
    function addThenSub(uint a, uint b, uint c) internal pure returns (Error, uint) {
        (Error err0, uint sum) = add(a, b);

        if (err0 != Error.NO_ERROR) {
            return (err0, 0);
        }

        return sub(sum, c);
    }
}
contract Exponential is ErrorReporter, CarefulMath {

    // TODO: We may wish to put the result of 10**18 here instead of the expression.
    // Per https://solidity.readthedocs.io/en/latest/contracts.html#constant-state-variables
    // the optimizer MAY replace the expression 10**18 with its calculated value.
    uint constant expScale = 10**18;

    // See TODO on expScale
    uint constant halfExpScale = expScale/2;

    struct Exp {
        uint mantissa;
    }

    uint constant mantissaOne = 10**18;
    uint constant mantissaOneTenth = 10**17;

    /**
    * @dev Creates an exponential from numerator and denominator values.
    *      Note: Returns an error if (`num` * 10e18) > MAX_INT,
    *            or if `denom` is zero.
    */
    function getExp(uint num, uint denom) pure internal returns (Error, Exp memory) {
        (Error err0, uint scaledNumerator) = mul(num, expScale);
        if (err0 != Error.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        (Error err1, uint rational) = div(scaledNumerator, denom);
        if (err1 != Error.NO_ERROR) {
            return (err1, Exp({mantissa: 0}));
        }

        return (Error.NO_ERROR, Exp({mantissa: rational}));
    }

    /**
    * @dev Adds two exponentials, returning a new exponential.
    */
    function addExp(Exp memory a, Exp memory b) pure internal returns (Error, Exp memory) {
        (Error error, uint result) = add(a.mantissa, b.mantissa);

        return (error, Exp({mantissa: result}));
    }

    /**
    * @dev Subtracts two exponentials, returning a new exponential.
    */
    function subExp(Exp memory a, Exp memory b) pure internal returns (Error, Exp memory) {
        (Error error, uint result) = sub(a.mantissa, b.mantissa);

        return (error, Exp({mantissa: result}));
    }

    /**
    * @dev Multiply an Exp by a scalar, returning a new Exp.
    */
    function mulScalar(Exp memory a, uint scalar) pure internal returns (Error, Exp memory) {
        (Error err0, uint scaledMantissa) = mul(a.mantissa, scalar);
        if (err0 != Error.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        return (Error.NO_ERROR, Exp({mantissa: scaledMantissa}));
    }

    /**
    * @dev Divide an Exp by a scalar, returning a new Exp.
    */
    function divScalar(Exp memory a, uint scalar) pure internal returns (Error, Exp memory) {
        (Error err0, uint descaledMantissa) = div(a.mantissa, scalar);
        if (err0 != Error.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        return (Error.NO_ERROR, Exp({mantissa: descaledMantissa}));
    }

    /**
    * @dev Divide a scalar by an Exp, returning a new Exp.
    */
    function divScalarByExp(uint scalar, Exp divisor) pure internal returns (Error, Exp memory) {
        /*
            We are doing this as:
            getExp(mul(expScale, scalar), divisor.mantissa)

            How it works:
            Exp = a / b;
            Scalar = s;
            `s / (a / b)` = `b * s / a` and since for an Exp `a = mantissa, b = expScale`
        */
        (Error err0, uint numerator) = mul(expScale, scalar);
        if (err0 != Error.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }
        return getExp(numerator, divisor.mantissa);
    }

    /**
    * @dev Multiplies two exponentials, returning a new exponential.
    */
    function mulExp(Exp memory a, Exp memory b) pure internal returns (Error, Exp memory) {

        (Error err0, uint doubleScaledProduct) = mul(a.mantissa, b.mantissa);
        if (err0 != Error.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        // We add half the scale before dividing so that we get rounding instead of truncation.
        //  See "Listing 6" and text above it at https://accu.org/index.php/journals/1717
        // Without this change, a result like 6.6...e-19 will be truncated to 0 instead of being rounded to 1e-18.
        (Error err1, uint doubleScaledProductWithHalfScale) = add(halfExpScale, doubleScaledProduct);
        if (err1 != Error.NO_ERROR) {
            return (err1, Exp({mantissa: 0}));
        }

        (Error err2, uint product) = div(doubleScaledProductWithHalfScale, expScale);
        // The only error `div` can return is Error.DIVISION_BY_ZERO but we control `expScale` and it is not zero.
        assert(err2 == Error.NO_ERROR);

        return (Error.NO_ERROR, Exp({mantissa: product}));
    }

    /**
      * @dev Divides two exponentials, returning a new exponential.
      *     (a/scale) / (b/scale) = (a/scale) * (scale/b) = a/b,
      *  which we can scale as an Exp by calling getExp(a.mantissa, b.mantissa)
      */
    function divExp(Exp memory a, Exp memory b) pure internal returns (Error, Exp memory) {
        return getExp(a.mantissa, b.mantissa);
    }

    /**
      * @dev Truncates the given exp to a whole number value.
      *      For example, truncate(Exp{mantissa: 15 * (10**18)}) = 15
      */
    function truncate(Exp memory exp) pure internal returns (uint) {
        // Note: We are not using careful math here as we're performing a division that cannot fail
        return exp.mantissa / 10**18;
    }

    /**
      * @dev Checks if first Exp is less than second Exp.
      */
    function lessThanExp(Exp memory left, Exp memory right) pure internal returns (bool) {
        return left.mantissa < right.mantissa; //TODO: Add some simple tests and this in another PR yo.
    }

    /**
      * @dev Checks if left Exp <= right Exp.
      */
    function lessThanOrEqualExp(Exp memory left, Exp memory right) pure internal returns (bool) {
        return left.mantissa <= right.mantissa;
    }

    /**
      * @dev returns true if Exp is exactly zero
      */
    function isZeroExp(Exp memory value) pure internal returns (bool) {
        return value.mantissa == 0;
    }
}

contract StandardInterestRateModel is Exponential {

    uint constant oneMinusSpreadBasisPoints = 9000;
    uint constant blocksPerYear = 2102400;
    uint constant mantissaFivePercent = 5 * 10**16;

    enum IRError {
        NO_ERROR,
        FAILED_TO_ADD_CASH_PLUS_BORROWS,
        FAILED_TO_GET_EXP,
        FAILED_TO_MUL_PRODUCT_TIMES_BORROW_RATE
    }

    /*
     * @dev Calculates the utilization rate (borrows / (cash + borrows)) as an Exp
     */
    function getUtilizationRate(uint cash, uint borrows) pure internal returns (IRError, Exp memory) {
        if (borrows == 0) {
            // Utilization rate is zero when there's no borrows
            return (IRError.NO_ERROR, Exp({mantissa: 0}));
        }

        (Error err0, uint cashPlusBorrows) = add(cash, borrows);
        if (err0 != Error.NO_ERROR) {
            return (IRError.FAILED_TO_ADD_CASH_PLUS_BORROWS, Exp({mantissa: 0}));
        }

        (Error err1, Exp memory utilizationRate) = getExp(borrows, cashPlusBorrows);
        if (err1 != Error.NO_ERROR) {
            return (IRError.FAILED_TO_GET_EXP, Exp({mantissa: 0}));
        }

        return (IRError.NO_ERROR, utilizationRate);
    }

    /*
     * @dev Calculates the utilization and borrow rates for use by get{Supply,Borrow}Rate functions
     */
    function getUtilizationAndAnnualBorrowRate(uint cash, uint borrows) pure internal returns (IRError, Exp memory, Exp memory) {
        (IRError err0, Exp memory utilizationRate) = getUtilizationRate(cash, borrows);
        if (err0 != IRError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}), Exp({mantissa: 0}));
        }

        // Borrow Rate is 5% + UtilizationRate * 45%
        // 45% of utilizationRate, is `rate * 45 / 100`
        (Error err1, Exp memory utilizationRateMuled) = mulScalar(utilizationRate, 45);
        // `mulScalar` only overflows when the product is >= 2^256.
        // utilizationRate is a real number on the interval [0,1], which means that
        // utilizationRate.mantissa is in the interval [0e18,1e18], which means that 45 times
        // that is in the interval [0e18,45e18]. That interval has no intersection with 2^256, and therefore
        // this can never overflow. As such, we assert.
        assert(err1 == Error.NO_ERROR);

        (Error err2, Exp memory utilizationRateScaled) = divScalar(utilizationRateMuled, 100);
        // 100 is a constant, and therefore cannot be zero, which is the only error case of divScalar.
        assert(err2 == Error.NO_ERROR);

        // Add the 5% for (5% + 45% * Ua)
        (Error err3, Exp memory annualBorrowRate) = addExp(utilizationRateScaled, Exp({mantissa: mantissaFivePercent}));
        // `addExp` only fails when the addition of mantissas overflow.
        // As per above, utilizationRateMuled is capped at 45e18,
        // and utilizationRateScaled is capped at 4.5e17. mantissaFivePercent = 0.5e17, and thus the addition
        // is capped at 5e17, which is less than 2^256.
        assert(err3 == Error.NO_ERROR);

        return (IRError.NO_ERROR, utilizationRate, annualBorrowRate);
    }

    /**
      * @notice Gets the current supply interest rate based on the given asset, total cash and total borrows
      * @dev The return value should be scaled by 1e18, thus a return value of
      *      `(true, 1000000000000)` implies an interest rate of 0.000001 or 0.0001% *per block*.
      * @param _asset The asset to get the interest rate of
      * @param cash The total cash of the asset in the market
      * @param borrows The total borrows of the asset in the market
      * @return Success or failure and the supply interest rate per block scaled by 10e18
      */
    function getSupplyRate(address _asset, uint cash, uint borrows) public view returns (uint, uint) {
        _asset; // pragma ignore unused argument

        (IRError err0, Exp memory utilizationRate0, Exp memory annualBorrowRate) = getUtilizationAndAnnualBorrowRate(cash, borrows);
        if (err0 != IRError.NO_ERROR) {
            return (uint(err0), 0);
        }

        // We're going to multiply the utilization rate by the spread's numerator
        (Error err1, Exp memory utilizationRate1) = mulScalar(utilizationRate0, oneMinusSpreadBasisPoints);
        // mulScalar only overflows when product is greater than or equal to 2^256.
        // utilization rate's mantissa is a number between [0e18,1e18]. That means that
        // utilizationRate1 is a value between [0e18,9e21]. This is strictly less than 2^256.
        assert(err1 == Error.NO_ERROR);

        // Next multiply this product times the borrow rate
        (Error err2, Exp memory supplyRate0) = mulExp(utilizationRate1, annualBorrowRate);
        // If the product of the mantissas for mulExp are both less than 2^256,
        // then this operation will never fail. TODO: Verify.
        // We know that borrow rate is in the interval [0, 4e17] from above.
        // We know that utilizationRate1 is in the interval [0, 9e21] from directly above.
        // As such, the multiplication is in the interval of [0, 3.6e39]. This is strictly
        // less than 2^256 (which is about 10e77).
        assert(err2 == Error.NO_ERROR);

        // And then divide down by the spread's denominator (basis points divisor)
        // as well as by blocks per year.
        (Error err3, Exp memory supplyRate1) = divScalar(supplyRate0, 10000 * blocksPerYear); // basis points * blocks per year
        // divScalar only fails when divisor is zero. This is clearly not the case.
        assert(err3 == Error.NO_ERROR);

        // Note: mantissa is the rate scaled 1e18, which matches the expected result
        return (uint(IRError.NO_ERROR), supplyRate1.mantissa);
    }

    /**
      * @notice Gets the current borrow interest rate based on the given asset, total cash and total borrows
      * @dev The return value should be scaled by 1e18, thus a return value of
      *      `(true, 1000000000000)` implies an interest rate of 0.000001 or 0.0001% *per block*.
      * @param _asset The asset to get the interest rate of
      * @param cash The total cash of the asset in the market
      * @param borrows The total borrows of the asset in the market
      * @return Success or failure and the borrow interest rate per block scaled by 10e18
      */
    function getBorrowRate(address _asset, uint cash, uint borrows) public view returns (uint, uint) {
        _asset; // pragma ignore unused argument

        (IRError err0, Exp memory _utilizationRate, Exp memory annualBorrowRate) = getUtilizationAndAnnualBorrowRate(cash, borrows);
        if (err0 != IRError.NO_ERROR) {
            return (uint(err0), 0);
        }

        // And then divide down by blocks per year.
        (Error err1, Exp memory borrowRate) = divScalar(annualBorrowRate, blocksPerYear); // basis points * blocks per year
        // divScalar only fails when divisor is zero. This is clearly not the case.
        assert(err1 == Error.NO_ERROR);

        _utilizationRate; // pragma ignore unused variable

        // Note: mantissa is the rate scaled 1e18, which matches the expected result
        return (uint(IRError.NO_ERROR), borrowRate.mantissa);
    }
}