pragma solidity ^0.5.16;


/**
  * @title Bird's BController Interface
  */
contract BControllerInterface {
    /// @notice Indicator that this is a BController contract (for inspection)
    bool public constant isBController = true;

    /*** Assets You Are In ***/

    function enterMarkets(address[] calldata bTokens) external returns (uint[] memory);
    function exitMarket(address bToken) external returns (uint);

    /*** Policy Hooks ***/

    function mintAllowed(address bToken, address minter, uint mintAmount) external returns (uint);
    function mintVerify(address bToken, address minter, uint mintAmount, uint mintTokens) external;

    function redeemAllowed(address bToken, address redeemer, uint redeemTokens) external returns (uint);
    function redeemVerify(address bToken, address redeemer, uint redeemAmount, uint redeemTokens) external;

    function borrowAllowed(address bToken, address borrower, uint borrowAmount) external returns (uint);
    function borrowVerify(address bToken, address borrower, uint borrowAmount) external;

    function repayBorrowAllowed(address bToken, address payer, address borrower, uint repayAmount) external returns (uint);
    function repayBorrowVerify(address bToken, address payer, address borrower, uint repayAmount, uint borrowerIndex) external;

    function liquidateBorrowAllowed(address bTokenBorrowed, address bTokenCollateral, address liquidator, address borrower, uint repayAmount) external returns (uint);
    function liquidateBorrowVerify(address bTokenBorrowed, address bTokenCollateral, address liquidator, address borrower, uint repayAmount, uint seizeTokens) external;

    function seizeAllowed(address bTokenCollateral, address bTokenBorrowed, address liquidator, address borrower, uint seizeTokens) external returns (uint);
    function seizeVerify(address bTokenCollateral, address bTokenBorrowed, address liquidator, address borrower, uint seizeTokens) external;

    function transferAllowed(address bToken, address src, address dst, uint transferTokens) external returns (uint);
    function transferVerify(address bToken, address src, address dst, uint transferTokens) external;

    /*** Liquidity/Liquidation Calculations ***/

    function liquidateCalculateSeizeTokens(address bTokenBorrowed, address bTokenCollateral, uint repayAmount) external view returns (uint, uint);
}

/**
  * @title Bird's InterestRateModel Interface
  */
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 block
      * @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 block (as a percentage, and scaled by 1e18)
      */
    function getBorrowRate(uint cash, uint borrows, uint reserves) external view returns (uint);

    /**
      * @notice Calculates the current supply interest rate per block
      * @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 block (as a percentage, and scaled by 1e18)
      */
    function getSupplyRate(uint cash, uint borrows, uint reserves, uint reserveFactorMantissa) external view returns (uint);

}

/**
  * @title Bird's BToken Storage
  */
contract BTokenStorage {
    /**
     * @dev Guard variable for re-entrancy checks
     */
    bool internal _notEntered;

    /**
     * @notice EIP-20 token name for this token
     */
    string public name;

    /**
     * @notice EIP-20 token symbol for this token
     */
    string public symbol;

    /**
     * @notice EIP-20 token decimals for this token
     */
    uint8 public decimals;

    /**
     * @notice Maximum borrow rate that can ever be applied (.0005% / block)
     */

    uint internal constant borrowRateMaxMantissa = 0.0005e16;

    /**
     * @notice Maximum fraction of interest that can be set aside for reserves
     */
    uint internal constant reserveFactorMaxMantissa = 1e18;

    /**
     * @notice Administrator for this contract
     */
    address payable public admin;

    /**
     * @notice Pending administrator for this contract
     */
    address payable public pendingAdmin;

    /**
     * @notice Contract which oversees inter-bToken operations
     */
    BControllerInterface public bController;

    /**
     * @notice Model which tells what the current interest rate should be
     */
    InterestRateModel public interestRateModel;

    /**
     * @notice Initial exchange rate used when minting the first BTokens (used when totalSupply = 0)
     */
    uint internal initialExchangeRateMantissa;

    /**
     * @notice Fraction of interest currently set aside for reserves
     */
    uint public reserveFactorMantissa;

    /**
     * @notice Block number that interest was last accrued at
     */
    uint public accrualBlockNumber;

    /**
     * @notice Accumulator of the total earned interest rate since the opening of the market
     */
    uint public borrowIndex;

    /**
     * @notice Total amount of outstanding borrows of the underlying in this market
     */
    uint public totalBorrows;

    /**
     * @notice Total amount of reserves of the underlying held in this market
     */
    uint public totalReserves;

    /**
     * @notice Total number of tokens in circulation
     */
    uint public totalSupply;

    /**
     * @notice Official record of token balances for each account
     */
    mapping (address => uint) internal accountTokens;

    /**
     * @notice Approved token transfer amounts on behalf of others
     */
    mapping (address => mapping (address => uint)) internal transferAllowances;

    /**
     * @notice Container for borrow balance information
     * @member principal Total balance (with accrued interest), after applying the most recent balance-changing action
     * @member interestIndex Global borrowIndex as of the most recent balance-changing action
     */
    struct BorrowSnapshot {
        uint principal;
        uint interestIndex;
    }

    /**
     * @notice Mapping of account addresses to outstanding borrow balances
     */
    mapping(address => BorrowSnapshot) internal accountBorrows;
}

/**
  * @title Bird's BToken Interface
  */
contract BTokenInterface is BTokenStorage {
    /**
     * @notice Indicator that this is a BToken contract (for inspection)
     */
    bool public constant isBToken = true;


    /*** Market Events ***/

    /**
     * @notice Event emitted when interest is accrued
     */
    event AccrueInterestToken(uint cashPrior, uint interestAccumulated, uint borrowIndex, uint totalBorrows);

    /**
     * @notice Event emitted when tokens are minted
     */
    event MintToken(address minter, uint mintAmount, uint mintTokens);

    /**
     * @notice Event emitted when tokens are redeemed
     */
    event RedeemToken(address redeemer, uint redeemAmount, uint redeemTokens);

    /**
     * @notice Event emitted when underlying is borrowed
     */
    event BorrowToken(address borrower, uint borrowAmount, uint accountBorrows, uint totalBorrows);

    /**
     * @notice Event emitted when a borrow is repaid
     */
    event RepayBorrowToken(address payer, address borrower, uint repayAmount, uint accountBorrows, uint totalBorrows);

    /**
     * @notice Event emitted when a borrow is liquidated
     */
    event LiquidateBorrowToken(address liquidator, address borrower, uint repayAmount, address bTokenCollateral, uint seizeTokens);


    /*** Admin Events ***/

    /**
     * @notice Event emitted when pendingAdmin is changed
     */
    event NewPendingAdmin(address oldPendingAdmin, address newPendingAdmin);

    /**
     * @notice Event emitted when pendingAdmin is accepted, which means admin is updated
     */
    event NewAdmin(address oldAdmin, address newAdmin);

    /**
     * @notice Event emitted when bController is changed
     */
    event NewBController(BControllerInterface oldBController, BControllerInterface newBController);

    /**
     * @notice Event emitted when interestRateModel is changed
     */
    event NewMarketTokenInterestRateModel(InterestRateModel oldInterestRateModel, InterestRateModel newInterestRateModel);

    /**
     * @notice Event emitted when the reserve factor is changed
     */
    event NewTokenReserveFactor(uint oldReserveFactorMantissa, uint newReserveFactorMantissa);

    /**
     * @notice Event emitted when the reserves are added
     */
    event ReservesAdded(address benefactor, uint addAmount, uint newTotalReserves);

    /**
     * @notice Event emitted when the reserves are reduced
     */
    event ReservesReduced(address admin, uint reduceAmount, uint newTotalReserves);

    /**
     * @notice EIP20 Transfer event
     */
    event Transfer(address indexed from, address indexed to, uint amount);

    /**
     * @notice EIP20 Approval event
     */
    event Approval(address indexed owner, address indexed spender, uint amount);

    /**
     * @notice Failure event
     */
    event Failure(uint error, uint info, uint detail);


    /*** User Interface ***/

    function transfer(address dst, uint amount) external returns (bool);
    function transferFrom(address src, address dst, uint amount) external returns (bool);
    function approve(address spender, uint amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function balanceOfUnderlying(address owner) external returns (uint);
    function getAccountSnapshot(address account) external view returns (uint, uint, uint, uint);
    function borrowRatePerBlock() external view returns (uint);
    function supplyRatePerBlock() external view returns (uint);
    function totalBorrowsCurrent() external returns (uint);
    function borrowBalanceCurrent(address account) external returns (uint);
    function borrowBalanceStored(address account) public view returns (uint);
    function exchangeRateCurrent() public returns (uint);
    function exchangeRateStored() public view returns (uint);
    function getCash() external view returns (uint);
    function accrueInterest() public returns (uint);
    function seize(address liquidator, address borrower, uint seizeTokens) external returns (uint);

    /*** Admin Functions ***/

    function _setPendingAdmin(address payable newPendingAdmin) external returns (uint);
    function _acceptAdmin() external returns (uint);
    function _setBController(BControllerInterface newBController) public returns (uint);
    function _setReserveFactor(uint newReserveFactorMantissa) external returns (uint);
    function _reduceReserves(uint reduceAmount) external returns (uint);
    function _setInterestRateModel(InterestRateModel newInterestRateModel) public returns (uint);
}

/**
  * @title Bird's BErc20 Storage
  */
contract BErc20Storage {
    /**
     * @notice Underlying asset for this BToken
     */
    address public underlying;
}

/**
  * @title Bird's BErc20 Interface
  */
contract BErc20Interface is BErc20Storage {

    /*** User Interface ***/

    function mint(uint mintAmount) external returns (uint);
    function redeem(uint redeemTokens) external returns (uint);
    function redeemUnderlying(uint redeemAmount) external returns (uint);
    function borrow(uint borrowAmount) external returns (uint);
    function repayBorrow(uint repayAmount) external returns (uint);
    function repayBorrowBehalf(address borrower, uint repayAmount) external returns (uint);
    function liquidateBorrow(address borrower, uint repayAmount, BTokenInterface bTokenCollateral) external returns (uint);


    /*** Admin Functions ***/

    function _addReserves(uint addAmount) external returns (uint);
}

/**
  * @title Bird's BDelegation Storage
  */
contract BDelegationStorage {
    /**
     * @notice Implementation address for this contract
     */
    address public implementation;
}

/**
  * @title Bird's BDelegator Interface
  */
contract BDelegatorInterface is BDelegationStorage {
    /**
     * @notice Emitted when implementation is changed
     */
    event NewImplementation(address oldImplementation, address newImplementation);

    /**
     * @notice Called by the admin to update the implementation of the delegator
     * @param implementation_ The address of the new implementation for delegation
     * @param allowResign Flag to indicate whether to call _resignImplementation on the old implementation
     * @param becomeImplementationData The encoded bytes data to be passed to _becomeImplementation
     */
    function _setImplementation(address implementation_, bool allowResign, bytes memory becomeImplementationData) public;
}

/**
  * @title Bird's BDelegate Interface
  */
contract BDelegateInterface is BDelegationStorage {
    /**
     * @notice Called by the delegator on a delegate to initialize it for duty
     * @dev Should revert if any issues arise which make it unfit for delegation
     * @param data The encoded bytes data for any initialization
     */
    function _becomeImplementation(bytes memory data) public;

    /**
     * @notice Called by the delegator on a delegate to forfeit its responsibility
     */
    function _resignImplementation() public;
}

contract BControllerErrorReporter {
    enum Error {
        NO_ERROR,
        UNAUTHORIZED,
        BCONTROLLER_MISMATCH,
        INSUFFICIENT_SHORTFALL,
        INSUFFICIENT_LIQUIDITY,
        INVALID_CLOSE_FACTOR,
        INVALID_COLLATERAL_FACTOR,
        INVALID_LIQUIDATION_INCENTIVE,
        MARKET_NOT_ENTERED, // no longer possible
        MARKET_NOT_LISTED,
        MARKET_ALREADY_LISTED,
        MATH_ERROR,
        NONZERO_BORROW_BALANCE,
        PRICE_ERROR,
        REJECTION,
        SNAPSHOT_ERROR,
        TOO_MANY_ASSETS,
        TOO_MUCH_REPAY
    }

    enum FailureInfo {
        ACCEPT_ADMIN_PENDING_ADMIN_CHECK,
        ACCEPT_PENDING_IMPLEMENTATION_ADDRESS_CHECK,
        EXIT_MARKET_BALANCE_OWED,
        EXIT_MARKET_REJECTION,
        SET_CLOSE_FACTOR_OWNER_CHECK,
        SET_CLOSE_FACTOR_VALIDATION,
        SET_COLLATERAL_FACTOR_OWNER_CHECK,
        SET_COLLATERAL_FACTOR_NO_EXISTS,
        SET_COLLATERAL_FACTOR_VALIDATION,
        SET_COLLATERAL_FACTOR_WITHOUT_PRICE,
        SET_IMPLEMENTATION_OWNER_CHECK,
        SET_LIQUIDATION_INCENTIVE_OWNER_CHECK,
        SET_LIQUIDATION_INCENTIVE_VALIDATION,
        SET_MAX_ASSETS_OWNER_CHECK,
        SET_PENDING_ADMIN_OWNER_CHECK,
        SET_PENDING_IMPLEMENTATION_OWNER_CHECK,
        SET_PRICE_ORACLE_OWNER_CHECK,
        SUPPORT_MARKET_EXISTS,
        SUPPORT_MARKET_OWNER_CHECK,
        SET_PAUSE_GUARDIAN_OWNER_CHECK
    }

    /**
      * @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);

    /**
      * @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(Error err, FailureInfo info, uint opaqueError) internal returns (uint) {
        emit Failure(uint(err), uint(info), opaqueError);

        return uint(err);
    }
}

contract TokenErrorReporter {
    enum Error {
        NO_ERROR,
        UNAUTHORIZED,
        BAD_INPUT,
        BCONTROLLER_REJECTION,
        BCONTROLLER_CALCULATION_ERROR,
        INTEREST_RATE_MODEL_ERROR,
        INVALID_ACCOUNT_PAIR,
        INVALID_CLOSE_AMOUNT_REQUESTED,
        INVALID_COLLATERAL_FACTOR,
        MATH_ERROR,
        MARKET_NOT_FRESH,
        MARKET_NOT_LISTED,
        TOKEN_INSUFFICIENT_ALLOWANCE,
        TOKEN_INSUFFICIENT_BALANCE,
        TOKEN_INSUFFICIENT_CASH,
        TOKEN_TRANSFER_IN_FAILED,
        TOKEN_TRANSFER_OUT_FAILED
    }

    /*
     * 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,
        ACCRUE_INTEREST_ACCUMULATED_INTEREST_CALCULATION_FAILED,
        ACCRUE_INTEREST_BORROW_RATE_CALCULATION_FAILED,
        ACCRUE_INTEREST_NEW_BORROW_INDEX_CALCULATION_FAILED,
        ACCRUE_INTEREST_NEW_TOTAL_BORROWS_CALCULATION_FAILED,
        ACCRUE_INTEREST_NEW_TOTAL_RESERVES_CALCULATION_FAILED,
        ACCRUE_INTEREST_SIMPLE_INTEREST_FACTOR_CALCULATION_FAILED,
        BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED,
        BORROW_ACCRUE_INTEREST_FAILED,
        BORROW_CASH_NOT_AVAILABLE,
        BORROW_FRESHNESS_CHECK,
        BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED,
        BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED,
        BORROW_MARKET_NOT_LISTED,
        BORROW_BCONTROLLER_REJECTION,
        LIQUIDATE_ACCRUE_BORROW_INTEREST_FAILED,
        LIQUIDATE_ACCRUE_COLLATERAL_INTEREST_FAILED,
        LIQUIDATE_COLLATERAL_FRESHNESS_CHECK,
        LIQUIDATE_BCONTROLLER_REJECTION,
        LIQUIDATE_BCONTROLLER_CALCULATE_AMOUNT_SEIZE_FAILED,
        LIQUIDATE_CLOSE_AMOUNT_IS_UINT_MAX,
        LIQUIDATE_CLOSE_AMOUNT_IS_ZERO,
        LIQUIDATE_FRESHNESS_CHECK,
        LIQUIDATE_LIQUIDATOR_IS_BORROWER,
        LIQUIDATE_REPAY_BORROW_FRESH_FAILED,
        LIQUIDATE_SEIZE_BALANCE_INCREMENT_FAILED,
        LIQUIDATE_SEIZE_BALANCE_DECREMENT_FAILED,
        LIQUIDATE_SEIZE_BCONTROLLER_REJECTION,
        LIQUIDATE_SEIZE_LIQUIDATOR_IS_BORROWER,
        LIQUIDATE_SEIZE_TOO_MUCH,
        MINT_ACCRUE_INTEREST_FAILED,
        MINT_BCONTROLLER_REJECTION,
        MINT_EXCHANGE_CALCULATION_FAILED,
        MINT_EXCHANGE_RATE_READ_FAILED,
        MINT_FRESHNESS_CHECK,
        MINT_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED,
        MINT_NEW_TOTAL_SUPPLY_CALCULATION_FAILED,
        MINT_TRANSFER_IN_FAILED,
        MINT_TRANSFER_IN_NOT_POSSIBLE,
        REDEEM_ACCRUE_INTEREST_FAILED,
        REDEEM_BCONTROLLER_REJECTION,
        REDEEM_EXCHANGE_TOKENS_CALCULATION_FAILED,
        REDEEM_EXCHANGE_AMOUNT_CALCULATION_FAILED,
        REDEEM_EXCHANGE_RATE_READ_FAILED,
        REDEEM_FRESHNESS_CHECK,
        REDEEM_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED,
        REDEEM_NEW_TOTAL_SUPPLY_CALCULATION_FAILED,
        REDEEM_TRANSFER_OUT_NOT_POSSIBLE,
        REDUCE_RESERVES_ACCRUE_INTEREST_FAILED,
        REDUCE_RESERVES_ADMIN_CHECK,
        REDUCE_RESERVES_CASH_NOT_AVAILABLE,
        REDUCE_RESERVES_FRESH_CHECK,
        REDUCE_RESERVES_VALIDATION,
        REPAY_BEHALF_ACCRUE_INTEREST_FAILED,
        REPAY_BORROW_ACCRUE_INTEREST_FAILED,
        REPAY_BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED,
        REPAY_BORROW_BCONTROLLER_REJECTION,
        REPAY_BORROW_FRESHNESS_CHECK,
        REPAY_BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED,
        REPAY_BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED,
        REPAY_BORROW_TRANSFER_IN_NOT_POSSIBLE,
        SET_COLLATERAL_FACTOR_OWNER_CHECK,
        SET_COLLATERAL_FACTOR_VALIDATION,
        SET_BCONTROLLER_OWNER_CHECK,
        SET_INTEREST_RATE_MODEL_ACCRUE_INTEREST_FAILED,
        SET_INTEREST_RATE_MODEL_FRESH_CHECK,
        SET_INTEREST_RATE_MODEL_OWNER_CHECK,
        SET_MAX_ASSETS_OWNER_CHECK,
        SET_ORACLE_MARKET_NOT_LISTED,
        SET_PENDING_ADMIN_OWNER_CHECK,
        SET_RESERVE_FACTOR_ACCRUE_INTEREST_FAILED,
        SET_RESERVE_FACTOR_ADMIN_CHECK,
        SET_RESERVE_FACTOR_FRESH_CHECK,
        SET_RESERVE_FACTOR_BOUNDS_CHECK,
        TRANSFER_BCONTROLLER_REJECTION,
        TRANSFER_NOT_ALLOWED,
        TRANSFER_NOT_ENOUGH,
        TRANSFER_TOO_MUCH,
        ADD_RESERVES_ACCRUE_INTEREST_FAILED,
        ADD_RESERVES_FRESH_CHECK,
        ADD_RESERVES_TRANSFER_IN_NOT_POSSIBLE
    }

    /**
      * @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);

    /**
      * @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(Error err, FailureInfo info, uint opaqueError) internal returns (uint) {
        emit Failure(uint(err), uint(info), opaqueError);

        return uint(err);
    }
}

/**
  * @title Careful Math
  * @notice Derived from OpenZeppelin's SafeMath library
  *         https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/math/SafeMath.sol
  */
contract CarefulMath {

    /**
     * @dev Possible error codes that we can return
     */
    enum MathError {
        NO_ERROR,
        DIVISION_BY_ZERO,
        INTEGER_OVERFLOW,
        INTEGER_UNDERFLOW
    }

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

        uint c = a * b;

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

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

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

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

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

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

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

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

        return subUInt(sum, c);
    }
}

/**
 * @title Exponential module for storing fixed-precision decimals
 * @notice Exp is a struct which stores decimals with a fixed precision of 18 decimal places.
 *         Thus, if we wanted to store the 5.1, mantissa would store 5.1e18. That is:
 *         `Exp({mantissa: 5100000000000000000})`.
 */
contract Exponential is CarefulMath {
    uint constant expScale = 1e18;
    uint constant doubleScale = 1e36;
    uint constant halfExpScale = expScale/2;
    uint constant mantissaOne = expScale;

    struct Exp {
        uint mantissa;
    }

    struct Double {
        uint mantissa;
    }

    /**
     * @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 (MathError, Exp memory) {
        (MathError err0, uint scaledNumerator) = mulUInt(num, expScale);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

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

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

    /**
     * @dev Adds two exponentials, returning a new exponential.
     */
    function addExp(Exp memory a, Exp memory b) pure internal returns (MathError, Exp memory) {
        (MathError error, uint result) = addUInt(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 (MathError, Exp memory) {
        (MathError error, uint result) = subUInt(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 (MathError, Exp memory) {
        (MathError err0, uint scaledMantissa) = mulUInt(a.mantissa, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

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

    /**
     * @dev Multiply an Exp by a scalar, then truncate to return an unsigned integer.
     */
    function mulScalarTruncate(Exp memory a, uint scalar) pure internal returns (MathError, uint) {
        (MathError err, Exp memory product) = mulScalar(a, scalar);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return (MathError.NO_ERROR, truncate(product));
    }

    /**
     * @dev Multiply an Exp by a scalar, truncate, then add an to an unsigned integer, returning an unsigned integer.
     */
    function mulScalarTruncateAddUInt(Exp memory a, uint scalar, uint addend) pure internal returns (MathError, uint) {
        (MathError err, Exp memory product) = mulScalar(a, scalar);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return addUInt(truncate(product), addend);
    }

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

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

    /**
     * @dev Divide a scalar by an Exp, returning a new Exp.
     */
    function divScalarByExp(uint scalar, Exp memory divisor) pure internal returns (MathError, Exp memory) {
        /*
          We are doing this as:
          getExp(mulUInt(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`
        */
        (MathError err0, uint numerator) = mulUInt(expScale, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }
        return getExp(numerator, divisor.mantissa);
    }

    /**
     * @dev Divide a scalar by an Exp, then truncate to return an unsigned integer.
     */
    function divScalarByExpTruncate(uint scalar, Exp memory divisor) pure internal returns (MathError, uint) {
        (MathError err, Exp memory fraction) = divScalarByExp(scalar, divisor);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return (MathError.NO_ERROR, truncate(fraction));
    }

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

        (MathError err0, uint doubleScaledProduct) = mulUInt(a.mantissa, b.mantissa);
        if (err0 != MathError.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.
        (MathError err1, uint doubleScaledProductWithHalfScale) = addUInt(halfExpScale, doubleScaledProduct);
        if (err1 != MathError.NO_ERROR) {
            return (err1, Exp({mantissa: 0}));
        }

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

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

    /**
     * @dev Multiplies two exponentials given their mantissas, returning a new exponential.
     */
    function mulExp(uint a, uint b) pure internal returns (MathError, Exp memory) {
        return mulExp(Exp({mantissa: a}), Exp({mantissa: b}));
    }

    /**
     * @dev Multiplies three exponentials, returning a new exponential.
     */
    function mulExp3(Exp memory a, Exp memory b, Exp memory c) pure internal returns (MathError, Exp memory) {
        (MathError err, Exp memory ab) = mulExp(a, b);
        if (err != MathError.NO_ERROR) {
            return (err, ab);
        }
        return mulExp(ab, c);
    }

    /**
     * @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 (MathError, Exp memory) {
        return getExp(a.mantissa, b.mantissa);
    }

    /**
     * @dev Truncates the given exp to a whole number value.
     *      For example, truncate(Exp{mantissa: 15 * expScale}) = 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 / expScale;
    }

    /**
     * @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;
    }

    /**
     * @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 Checks if left Exp > right Exp.
     */
    function greaterThanExp(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;
    }

    function safe224(uint n, string memory errorMessage) pure internal returns (uint224) {
        require(n < 2**224, errorMessage);
        return uint224(n);
    }

    function safe32(uint n, string memory errorMessage) pure internal returns (uint32) {
        require(n < 2**32, errorMessage);
        return uint32(n);
    }

    function add_(Exp memory a, Exp memory b) pure internal returns (Exp memory) {
        return Exp({mantissa: add_(a.mantissa, b.mantissa)});
    }

    function add_(Double memory a, Double memory b) pure internal returns (Double memory) {
        return Double({mantissa: add_(a.mantissa, b.mantissa)});
    }

    function add_(uint a, uint b) pure internal returns (uint) {
        return add_(a, b, "addition overflow");
    }

    function add_(uint a, uint b, string memory errorMessage) pure internal returns (uint) {
        uint c = a + b;
        require(c >= a, errorMessage);
        return c;
    }

    function sub_(Exp memory a, Exp memory b) pure internal returns (Exp memory) {
        return Exp({mantissa: sub_(a.mantissa, b.mantissa)});
    }

    function sub_(Double memory a, Double memory b) pure internal returns (Double memory) {
        return Double({mantissa: sub_(a.mantissa, b.mantissa)});
    }

    function sub_(uint a, uint b) pure internal returns (uint) {
        return sub_(a, b, "subtraction underflow");
    }

    function sub_(uint a, uint b, string memory errorMessage) pure internal returns (uint) {
        require(b <= a, errorMessage);
        return a - b;
    }

    function mul_(Exp memory a, Exp memory b) pure internal returns (Exp memory) {
        return Exp({mantissa: mul_(a.mantissa, b.mantissa) / expScale});
    }

    function mul_(Exp memory a, uint b) pure internal returns (Exp memory) {
        return Exp({mantissa: mul_(a.mantissa, b)});
    }

    function mul_(uint a, Exp memory b) pure internal returns (uint) {
        return mul_(a, b.mantissa) / expScale;
    }

    function mul_(Double memory a, Double memory b) pure internal returns (Double memory) {
        return Double({mantissa: mul_(a.mantissa, b.mantissa) / doubleScale});
    }

    function mul_(Double memory a, uint b) pure internal returns (Double memory) {
        return Double({mantissa: mul_(a.mantissa, b)});
    }

    function mul_(uint a, Double memory b) pure internal returns (uint) {
        return mul_(a, b.mantissa) / doubleScale;
    }

    function mul_(uint a, uint b) pure internal returns (uint) {
        return mul_(a, b, "multiplication overflow");
    }

    function mul_(uint a, uint b, string memory errorMessage) pure internal returns (uint) {
        if (a == 0 || b == 0) {
            return 0;
        }
        uint c = a * b;
        require(c / a == b, errorMessage);
        return c;
    }

    function div_(Exp memory a, Exp memory b) pure internal returns (Exp memory) {
        return Exp({mantissa: div_(mul_(a.mantissa, expScale), b.mantissa)});
    }

    function div_(Exp memory a, uint b) pure internal returns (Exp memory) {
        return Exp({mantissa: div_(a.mantissa, b)});
    }

    function div_(uint a, Exp memory b) pure internal returns (uint) {
        return div_(mul_(a, expScale), b.mantissa);
    }

    function div_(Double memory a, Double memory b) pure internal returns (Double memory) {
        return Double({mantissa: div_(mul_(a.mantissa, doubleScale), b.mantissa)});
    }

    function div_(Double memory a, uint b) pure internal returns (Double memory) {
        return Double({mantissa: div_(a.mantissa, b)});
    }

    function div_(uint a, Double memory b) pure internal returns (uint) {
        return div_(mul_(a, doubleScale), b.mantissa);
    }

    function div_(uint a, uint b) pure internal returns (uint) {
        return div_(a, b, "divide by zero");
    }

    function div_(uint a, uint b, string memory errorMessage) pure internal returns (uint) {
        require(b > 0, errorMessage);
        return a / b;
    }

    function fraction(uint a, uint b) pure internal returns (Double memory) {
        return Double({mantissa: div_(mul_(a, doubleScale), b)});
    }
}

/**
 * @title ERC 20 Token Standard Interface
 *  https://eips.ethereum.org/EIPS/eip-20
 */
interface EIP20Interface {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);

    /**
      * @notice Get the total number of tokens in circulation
      * @return The supply of tokens
      */
    function totalSupply() external view returns (uint256);

    /**
     * @notice Gets the balance of the specified address
     * @param owner The address from which the balance will be retrieved
     * @return The balance
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
      * @notice Transfer `amount` tokens from `msg.sender` to `dst`
      * @param dst The address of the destination account
      * @param amount The number of tokens to transfer
      * @return Whether or not the transfer succeeded
      */
    function transfer(address dst, uint256 amount) external returns (bool success);

    /**
      * @notice Transfer `amount` tokens from `src` to `dst`
      * @param src The address of the source account
      * @param dst The address of the destination account
      * @param amount The number of tokens to transfer
      * @return Whether or not the transfer succeeded
      */
    function transferFrom(address src, address dst, uint256 amount) external returns (bool success);

    /**
      * @notice Approve `spender` to transfer up to `amount` from `src`
      * @dev This will overwrite the approval amount for `spender`
      *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
      * @param spender The address of the account which may transfer tokens
      * @param amount The number of tokens that are approved (-1 means infinite)
      * @return Whether or not the approval succeeded
      */
    function approve(address spender, uint256 amount) external returns (bool success);

    /**
      * @notice Get the current allowance from `owner` for `spender`
      * @param owner The address of the account which owns the tokens to be spent
      * @param spender The address of the account which may transfer tokens
      * @return The number of tokens allowed to be spent (-1 means infinite)
      */
    function allowance(address owner, address spender) external view returns (uint256 remaining);

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(address indexed owner, address indexed spender, uint256 amount);
}

/**
 * @title EIP20NonStandardInterface
 * @dev Version of ERC20 with no return values for `transfer` and `transferFrom`
 *  See https://medium.com/coinmonks/missing-return-value-bug-at-least-130-tokens-affected-d67bf08521ca
 */
interface EIP20NonStandardInterface {

    /**
     * @notice Get the total number of tokens in circulation
     * @return The supply of tokens
     */
    function totalSupply() external view returns (uint256);

    /**
     * @notice Gets the balance of the specified address
     * @param owner The address from which the balance will be retrieved
     * @return The balance
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    ///
    /// !!!!!!!!!!!!!!
    /// !!! NOTICE !!! `transfer` does not return a value, in violation of the ERC-20 specification
    /// !!!!!!!!!!!!!!
    ///

    /**
      * @notice Transfer `amount` tokens from `msg.sender` to `dst`
      * @param dst The address of the destination account
      * @param amount The number of tokens to transfer
      */
    function transfer(address dst, uint256 amount) external;

    ///
    /// !!!!!!!!!!!!!!
    /// !!! NOTICE !!! `transferFrom` does not return a value, in violation of the ERC-20 specification
    /// !!!!!!!!!!!!!!
    ///

    /**
      * @notice Transfer `amount` tokens from `src` to `dst`
      * @param src The address of the source account
      * @param dst The address of the destination account
      * @param amount The number of tokens to transfer
      */
    function transferFrom(address src, address dst, uint256 amount) external;

    /**
      * @notice Approve `spender` to transfer up to `amount` from `src`
      * @dev This will overwrite the approval amount for `spender`
      *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
      * @param spender The address of the account which may transfer tokens
      * @param amount The number of tokens that are approved
      * @return Whether or not the approval succeeded
      */
    function approve(address spender, uint256 amount) external returns (bool success);

    /**
      * @notice Get the current allowance from `owner` for `spender`
      * @param owner The address of the account which owns the tokens to be spent
      * @param spender The address of the account which may transfer tokens
      * @return The number of tokens allowed to be spent
      */
    function allowance(address owner, address spender) external view returns (uint256 remaining);

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(address indexed owner, address indexed spender, uint256 amount);
}

/**
 * @title Bird's BToken Contract
 * @notice Abstract base for BTokens
 */
contract BToken is BTokenInterface, Exponential, TokenErrorReporter {

    /**
     * @notice Initialize the money market
     * @param bController_ The address of the BController
     * @param interestRateModel_ The address of the interest rate model
     * @param initialExchangeRateMantissa_ The initial exchange rate, scaled by 1e18
     * @param name_ EIP-20 name of this token
     * @param symbol_ EIP-20 symbol of this token
     * @param decimals_ EIP-20 decimal precision of this token
     */
    function initialize(BControllerInterface bController_,
                        InterestRateModel interestRateModel_,
                        uint initialExchangeRateMantissa_,
                        string memory name_,
                        string memory symbol_,
                        uint8 decimals_) public {
        require(msg.sender == admin, "only admin may initialize the market");
        require(accrualBlockNumber == 0 && borrowIndex == 0, "market may only be initialized once");

        // Set initial exchange rate
        initialExchangeRateMantissa = initialExchangeRateMantissa_;
        require(initialExchangeRateMantissa > 0, "initial exchange rate must be greater than zero.");

        // Set the bController
        uint err = _setBController(bController_);
        require(err == uint(Error.NO_ERROR), "setting bController failed");

        // Initialize block number and borrow index (block number mocks depend on bController being set)
        accrualBlockNumber = getBlockNumber();
        borrowIndex = mantissaOne;

        // Set the interest rate model (depends on block number / borrow index)
        err = _setInterestRateModelFresh(interestRateModel_);
        require(err == uint(Error.NO_ERROR), "setting interest rate model failed");

        name = name_;
        symbol = symbol_;
        decimals = decimals_;

        // The counter starts true to prevent changing it from zero to non-zero (i.e. smaller cost/refund)
        _notEntered = true;
    }

    /**
     * @notice Transfer `tokens` tokens from `src` to `dst` by `spender`
     * @dev Called by both `transfer` and `transferFrom` internally
     * @param spender The address of the account performing the transfer
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param tokens The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transferTokens(address spender, address src, address dst, uint tokens) internal returns (uint) {
        /* Fail if transfer not allowed */
        uint allowed = bController.transferAllowed(address(this), src, dst, tokens);
        if (allowed != 0) {
            return failOpaque(Error.BCONTROLLER_REJECTION, FailureInfo.TRANSFER_BCONTROLLER_REJECTION, allowed);
        }

        /* Do not allow self-transfers */
        if (src == dst) {
            return fail(Error.BAD_INPUT, FailureInfo.TRANSFER_NOT_ALLOWED);
        }

        /* Get the allowance, infinite for the account owner */
        uint startingAllowance = 0;
        if (spender == src) {
            startingAllowance = uint(-1);
        } else {
            startingAllowance = transferAllowances[src][spender];
        }

        /* Do the calculations, checking for {under,over}flow */
        MathError mathErr;
        uint allowanceNew;
        uint scrTokensNew;
        uint dstTokensNew;

        (mathErr, allowanceNew) = subUInt(startingAllowance, tokens);
        if (mathErr != MathError.NO_ERROR) {
            return fail(Error.MATH_ERROR, FailureInfo.TRANSFER_NOT_ALLOWED);
        }

        (mathErr, scrTokensNew) = subUInt(accountTokens[src], tokens);
        if (mathErr != MathError.NO_ERROR) {
            return fail(Error.MATH_ERROR, FailureInfo.TRANSFER_NOT_ENOUGH);
        }

        (mathErr, dstTokensNew) = addUInt(accountTokens[dst], tokens);
        if (mathErr != MathError.NO_ERROR) {
            return fail(Error.MATH_ERROR, FailureInfo.TRANSFER_TOO_MUCH);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        accountTokens[src] = scrTokensNew;
        accountTokens[dst] = dstTokensNew;

        /* Eat some of the allowance (if necessary) */
        if (startingAllowance != uint(-1)) {
            transferAllowances[src][spender] = allowanceNew;
        }

        /* We emit a Transfer event */
        emit Transfer(src, dst, tokens);

        bController.transferVerify(address(this), src, dst, tokens);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Transfer `amount` tokens from `msg.sender` to `dst`
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transfer(address dst, uint256 amount) external nonReentrant returns (bool) {
        return transferTokens(msg.sender, msg.sender, dst, amount) == uint(Error.NO_ERROR);
    }

    /**
     * @notice Transfer `amount` tokens from `src` to `dst`
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transferFrom(address src, address dst, uint256 amount) external nonReentrant returns (bool) {
        return transferTokens(msg.sender, src, dst, amount) == uint(Error.NO_ERROR);
    }

    /**
     * @notice Approve `spender` to transfer up to `amount` from `src`
     * @dev This will overwrite the approval amount for `spender`
     *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
     * @param spender The address of the account which may transfer tokens
     * @param amount The number of tokens that are approved (-1 means infinite)
     * @return Whether or not the approval succeeded
     */
    function approve(address spender, uint256 amount) external returns (bool) {
        address src = msg.sender;
        transferAllowances[src][spender] = amount;
        emit Approval(src, spender, amount);
        return true;
    }

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param owner The address of the account which owns the tokens to be spent
     * @param spender The address of the account which may transfer tokens
     * @return The number of tokens allowed to be spent (-1 means infinite)
     */
    function allowance(address owner, address spender) external view returns (uint256) {
        return transferAllowances[owner][spender];
    }

    /**
     * @notice Get the token balance of the `owner`
     * @param owner The address of the account to query
     * @return The number of tokens owned by `owner`
     */
    function balanceOf(address owner) external view returns (uint256) {
        return accountTokens[owner];
    }

    /**
     * @notice Get the underlying balance of the `owner`
     * @dev This also accrues interest in a transaction
     * @param owner The address of the account to query
     * @return The amount of underlying owned by `owner`
     */
    function balanceOfUnderlying(address owner) external returns (uint) {
        Exp memory exchangeRate = Exp({mantissa: exchangeRateCurrent()});
        (MathError mErr, uint balance) = mulScalarTruncate(exchangeRate, accountTokens[owner]);
        require(mErr == MathError.NO_ERROR, "balance could not be calculated");
        return balance;
    }

    /**
     * @notice Get a snapshot of the account's balances, and the cached exchange rate
     * @dev This is used by bController to more efficiently perform liquidity checks.
     * @param account Address of the account to snapshot
     * @return (possible error, token balance, borrow balance, exchange rate mantissa)
     */
    function getAccountSnapshot(address account) external view returns (uint, uint, uint, uint) {
        uint bTokenBalance = accountTokens[account];
        uint borrowBalance;
        uint exchangeRateMantissa;

        MathError mErr;

        (mErr, borrowBalance) = borrowBalanceStoredInternal(account);
        if (mErr != MathError.NO_ERROR) {
            return (uint(Error.MATH_ERROR), 0, 0, 0);
        }

        (mErr, exchangeRateMantissa) = exchangeRateStoredInternal();
        if (mErr != MathError.NO_ERROR) {
            return (uint(Error.MATH_ERROR), 0, 0, 0);
        }

        return (uint(Error.NO_ERROR), bTokenBalance, borrowBalance, exchangeRateMantissa);
    }

    /**
     * @dev Function to simply retrieve block number
     *  This exists mainly for inheriting test contracts to stub this result.
     */
    function getBlockNumber() internal view returns (uint) {
        return block.number;
    }

    /**
     * @notice Returns the current per-block borrow interest rate for this bToken
     * @return The borrow interest rate per block, scaled by 1e18
     */
    function borrowRatePerBlock() external view returns (uint) {
        return interestRateModel.getBorrowRate(getCashPrior(), totalBorrows, totalReserves);
    }

    /**
     * @notice Returns the current per-block supply interest rate for this bToken
     * @return The supply interest rate per block, scaled by 1e18
     */
    function supplyRatePerBlock() external view returns (uint) {
        return interestRateModel.getSupplyRate(getCashPrior(), totalBorrows, totalReserves, reserveFactorMantissa);
    }

    /**
     * @notice Returns the current total borrows plus accrued interest
     * @return The total borrows with interest
     */
    function totalBorrowsCurrent() external nonReentrant returns (uint) {
        require(accrueInterest() == uint(Error.NO_ERROR), "accrue interest failed");
        return totalBorrows;
    }

    /**
     * @notice Accrue interest to updated borrowIndex and then calculate account's borrow balance using the updated borrowIndex
     * @param account The address whose balance should be calculated after updating borrowIndex
     * @return The calculated balance
     */
    function borrowBalanceCurrent(address account) external nonReentrant returns (uint) {
        require(accrueInterest() == uint(Error.NO_ERROR), "accrue interest failed");
        return borrowBalanceStored(account);
    }

    /**
     * @notice Return the borrow balance of account based on stored data
     * @param account The address whose balance should be calculated
     * @return The calculated balance
     */
    function borrowBalanceStored(address account) public view returns (uint) {
        (MathError err, uint result) = borrowBalanceStoredInternal(account);
        require(err == MathError.NO_ERROR, "borrowBalanceStored: borrowBalanceStoredInternal failed");
        return result;
    }

    /**
     * @notice Return the borrow balance of account based on stored data
     * @param account The address whose balance should be calculated
     * @return (error code, the calculated balance or 0 if error code is non-zero)
     */
    function borrowBalanceStoredInternal(address account) internal view returns (MathError, uint) {
        /* Note: we do not assert that the market is up to date */
        MathError mathErr;
        uint principalTimesIndex;
        uint result;

        /* Get borrowBalance and borrowIndex */
        BorrowSnapshot storage borrowSnapshot = accountBorrows[account];

        /* If borrowBalance = 0 then borrowIndex is likely also 0.
         * Rather than failing the calculation with a division by 0, we immediately return 0 in this case.
         */
        if (borrowSnapshot.principal == 0) {
            return (MathError.NO_ERROR, 0);
        }

        /* Calculate new borrow balance using the interest index:
         *  recentBorrowBalance = borrower.borrowBalance * market.borrowIndex / borrower.borrowIndex
         */
        (mathErr, principalTimesIndex) = mulUInt(borrowSnapshot.principal, borrowIndex);
        if (mathErr != MathError.NO_ERROR) {
            return (mathErr, 0);
        }

        (mathErr, result) = divUInt(principalTimesIndex, borrowSnapshot.interestIndex);
        if (mathErr != MathError.NO_ERROR) {
            return (mathErr, 0);
        }

        return (MathError.NO_ERROR, result);
    }

    /**
     * @notice Accrue interest then return the up-to-date exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateCurrent() public nonReentrant returns (uint) {
        require(accrueInterest() == uint(Error.NO_ERROR), "accrue interest failed");
        return exchangeRateStored();
    }

    /**
     * @notice Calculates the exchange rate from the underlying to the BToken
     * @dev This function does not accrue interest before calculating the exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateStored() public view returns (uint) {
        (MathError err, uint result) = exchangeRateStoredInternal();
        require(err == MathError.NO_ERROR, "exchangeRateStored: exchangeRateStoredInternal failed");
        return result;
    }

    /**
     * @notice Calculates the exchange rate from the underlying to the BToken
     * @dev This function does not accrue interest before calculating the exchange rate
     * @return (error code, calculated exchange rate scaled by 1e18)
     */
    function exchangeRateStoredInternal() internal view returns (MathError, uint) {
        uint _totalSupply = totalSupply;
        if (_totalSupply == 0) {
            /*
             * If there are no tokens minted:
             *  exchangeRate = initialExchangeRate
             */
            return (MathError.NO_ERROR, initialExchangeRateMantissa);
        } else {
            /*
             * Otherwise:
             *  exchangeRate = (totalCash + totalBorrows - totalReserves) / totalSupply
             */
            uint totalCash = getCashPrior();
            uint cashPlusBorrowsMinusReserves;
            Exp memory exchangeRate;
            MathError mathErr;

            (mathErr, cashPlusBorrowsMinusReserves) = addThenSubUInt(totalCash, totalBorrows, totalReserves);
            if (mathErr != MathError.NO_ERROR) {
                return (mathErr, 0);
            }

            (mathErr, exchangeRate) = getExp(cashPlusBorrowsMinusReserves, _totalSupply);
            if (mathErr != MathError.NO_ERROR) {
                return (mathErr, 0);
            }

            return (MathError.NO_ERROR, exchangeRate.mantissa);
        }
    }

    /**
     * @notice Get cash balance of this bToken in the underlying asset
     * @return The quantity of underlying asset owned by this contract
     */
    function getCash() external view returns (uint) {
        return getCashPrior();
    }

    /**
     * @notice Applies accrued interest to total borrows and reserves
     * @dev This calculates interest accrued from the last checkpointed block
     *   up to the current block and writes new checkpoint to storage.
     */
    function accrueInterest() public returns (uint) {
        /* Remember the initial block number */
        uint currentBlockNumber = getBlockNumber();
        uint accrualBlockNumberPrior = accrualBlockNumber;

        /* Short-circuit accumulating 0 interest */
        if (accrualBlockNumberPrior == currentBlockNumber) {
            return uint(Error.NO_ERROR);
        }

        /* Read the previous values out of storage */
        uint cashPrior = getCashPrior();
        uint borrowsPrior = totalBorrows;
        uint reservesPrior = totalReserves;
        uint borrowIndexPrior = borrowIndex;

        /* Calculate the current borrow interest rate */
        uint borrowRateMantissa = interestRateModel.getBorrowRate(cashPrior, borrowsPrior, reservesPrior);
        require(borrowRateMantissa <= borrowRateMaxMantissa, "borrow rate is absurdly high");

        /* Calculate the number of blocks elapsed since the last accrual */
        (MathError mathErr, uint blockDelta) = subUInt(currentBlockNumber, accrualBlockNumberPrior);
        require(mathErr == MathError.NO_ERROR, "could not calculate block delta");

        /*
         * Calculate the interest accumulated into borrows and reserves and the new index:
         *  simpleInterestFactor = borrowRate * blockDelta
         *  interestAccumulated = simpleInterestFactor * totalBorrows
         *  totalBorrowsNew = interestAccumulated + totalBorrows
         *  totalReservesNew = interestAccumulated * reserveFactor + totalReserves
         *  borrowIndexNew = simpleInterestFactor * borrowIndex + borrowIndex
         */

        Exp memory simpleInterestFactor;
        uint interestAccumulated;
        uint totalBorrowsNew;
        uint totalReservesNew;
        uint borrowIndexNew;

        (mathErr, simpleInterestFactor) = mulScalar(Exp({mantissa: borrowRateMantissa}), blockDelta);
        if (mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.ACCRUE_INTEREST_SIMPLE_INTEREST_FACTOR_CALCULATION_FAILED, uint(mathErr));
        }

        (mathErr, interestAccumulated) = mulScalarTruncate(simpleInterestFactor, borrowsPrior);
        if (mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.ACCRUE_INTEREST_ACCUMULATED_INTEREST_CALCULATION_FAILED, uint(mathErr));
        }

        (mathErr, totalBorrowsNew) = addUInt(interestAccumulated, borrowsPrior);
        if (mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.ACCRUE_INTEREST_NEW_TOTAL_BORROWS_CALCULATION_FAILED, uint(mathErr));
        }

        (mathErr, totalReservesNew) = mulScalarTruncateAddUInt(Exp({mantissa: reserveFactorMantissa}), interestAccumulated, reservesPrior);
        if (mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.ACCRUE_INTEREST_NEW_TOTAL_RESERVES_CALCULATION_FAILED, uint(mathErr));
        }

        (mathErr, borrowIndexNew) = mulScalarTruncateAddUInt(simpleInterestFactor, borrowIndexPrior, borrowIndexPrior);
        if (mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.ACCRUE_INTEREST_NEW_BORROW_INDEX_CALCULATION_FAILED, uint(mathErr));
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /* We write the previously calculated values into storage */
        accrualBlockNumber = currentBlockNumber;
        borrowIndex = borrowIndexNew;
        totalBorrows = totalBorrowsNew;
        totalReserves = totalReservesNew;

        /* We emit an AccrueInterest event */
        emit AccrueInterestToken(cashPrior, interestAccumulated, borrowIndexNew, totalBorrowsNew);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Sender supplies assets into the market and receives bTokens in exchange
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param mintAmount The amount of the underlying asset to supply
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual mint amount.
     */
    function mintInternal(uint mintAmount) internal nonReentrant returns (uint, uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted borrow failed
            return (fail(Error(error), FailureInfo.MINT_ACCRUE_INTEREST_FAILED), 0);
        }
        // mintFresh emits the actual Mint event if successful and logs on errors, so we don't need to
        return mintFresh(msg.sender, mintAmount);
    }

    struct MintLocalVars {
        Error err;
        MathError mathErr;
        uint exchangeRateMantissa;
        uint mintTokens;
        uint totalSupplyNew;
        uint accountTokensNew;
        uint actualMintAmount;
    }

    /**
     * @notice User supplies assets into the market and receives bTokens in exchange
     * @dev Assumes interest has already been accrued up to the current block
     * @param minter The address of the account which is supplying the assets
     * @param mintAmount The amount of the underlying asset to supply
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual mint amount.
     */
    function mintFresh(address minter, uint mintAmount) internal returns (uint, uint) {
        /* Fail if mint not allowed */
        uint allowed = bController.mintAllowed(address(this), minter, mintAmount);

        if (allowed != 0) {
            return (failOpaque(Error.BCONTROLLER_REJECTION, FailureInfo.MINT_BCONTROLLER_REJECTION, allowed), 0);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            return (fail(Error.MARKET_NOT_FRESH, FailureInfo.MINT_FRESHNESS_CHECK), 0);
        }

        MintLocalVars memory vars;

        (vars.mathErr, vars.exchangeRateMantissa) = exchangeRateStoredInternal();
        if (vars.mathErr != MathError.NO_ERROR) {
            return (failOpaque(Error.MATH_ERROR, FailureInfo.MINT_EXCHANGE_RATE_READ_FAILED, uint(vars.mathErr)), 0);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         *  We call `doTransferIn` for the minter and the mintAmount.
         *  Note: The bToken must handle variations between ERC-20 and ETH underlying.
         *  `doTransferIn` reverts if anything goes wrong, since we can't be sure if
         *  side-effects occurred. The function returns the amount actually transferred,
         *  in case of a fee. On success, the bToken holds an additional `actualMintAmount`
         *  of cash.
         */
        vars.actualMintAmount = doTransferIn(minter, mintAmount);

        /*
         * We get the current exchange rate and calculate the number of bTokens to be minted:
         *  mintTokens = actualMintAmount / exchangeRate
         */

        (vars.mathErr, vars.mintTokens) = divScalarByExpTruncate(vars.actualMintAmount, Exp({mantissa: vars.exchangeRateMantissa}));
        require(vars.mathErr == MathError.NO_ERROR, "MINT_EXCHANGE_CALCULATION_FAILED");

        /*
         * We calculate the new total supply of bTokens and minter token balance, checking for overflow:
         *  totalSupplyNew = totalSupply + mintTokens
         *  accountTokensNew = accountTokens[minter] + mintTokens
         */
        (vars.mathErr, vars.totalSupplyNew) = addUInt(totalSupply, vars.mintTokens);
        require(vars.mathErr == MathError.NO_ERROR, "MINT_NEW_TOTAL_SUPPLY_CALCULATION_FAILED");

        (vars.mathErr, vars.accountTokensNew) = addUInt(accountTokens[minter], vars.mintTokens);
        require(vars.mathErr == MathError.NO_ERROR, "MINT_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED");

        /* We write previously calculated values into storage */
        totalSupply = vars.totalSupplyNew;
        accountTokens[minter] = vars.accountTokensNew;

        /* We emit a Mint event, and a Transfer event */
        emit MintToken(minter, vars.actualMintAmount, vars.mintTokens);
        emit Transfer(address(this), minter, vars.mintTokens);

        /* We call the defense hook */
        bController.mintVerify(address(this), minter, vars.actualMintAmount, vars.mintTokens);

        return (uint(Error.NO_ERROR), vars.actualMintAmount);
    }

    /**
     * @notice Sender redeems bTokens in exchange for the underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param redeemTokens The number of bTokens to redeem into underlying
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemInternal(uint redeemTokens) internal nonReentrant returns (uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted redeem failed
            return fail(Error(error), FailureInfo.REDEEM_ACCRUE_INTEREST_FAILED);
        }
        // redeemFresh emits redeem-specific logs on errors, so we don't need to
        return redeemFresh(msg.sender, redeemTokens, 0);
    }

    /**
     * @notice Sender redeems bTokens in exchange for a specified amount of underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param redeemAmount The amount of underlying to receive from redeeming bTokens
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemUnderlyingInternal(uint redeemAmount) internal nonReentrant returns (uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted redeem failed
            return fail(Error(error), FailureInfo.REDEEM_ACCRUE_INTEREST_FAILED);
        }
        // redeemFresh emits redeem-specific logs on errors, so we don't need to
        return redeemFresh(msg.sender, 0, redeemAmount);
    }

    struct RedeemLocalVars {
        Error err;
        MathError mathErr;
        uint exchangeRateMantissa;
        uint redeemTokens;
        uint redeemAmount;
        uint totalSupplyNew;
        uint accountTokensNew;
    }

    /**
     * @notice User redeems bTokens in exchange for the underlying asset
     * @dev Assumes interest has already been accrued up to the current block
     * @param redeemer The address of the account which is redeeming the tokens
     * @param redeemTokensIn The number of bTokens to redeem into underlying (only one of redeemTokensIn or redeemAmountIn may be non-zero)
     * @param redeemAmountIn The number of underlying tokens to receive from redeeming bTokens (only one of redeemTokensIn or redeemAmountIn may be non-zero)
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function redeemFresh(address payable redeemer, uint redeemTokensIn, uint redeemAmountIn) internal returns (uint) {
        require(redeemTokensIn == 0 || redeemAmountIn == 0, "one of redeemTokensIn or redeemAmountIn must be zero");

        RedeemLocalVars memory vars;

        /* exchangeRate = invoke Exchange Rate Stored() */
        (vars.mathErr, vars.exchangeRateMantissa) = exchangeRateStoredInternal();
        if (vars.mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.REDEEM_EXCHANGE_RATE_READ_FAILED, uint(vars.mathErr));
        }

        /* If redeemTokensIn > 0: */
        if (redeemTokensIn > 0) {
            /*
             * We calculate the exchange rate and the amount of underlying to be redeemed:
             *  redeemTokens = redeemTokensIn
             *  redeemAmount = redeemTokensIn x exchangeRateCurrent
             */
            vars.redeemTokens = redeemTokensIn;

            (vars.mathErr, vars.redeemAmount) = mulScalarTruncate(Exp({mantissa: vars.exchangeRateMantissa}), redeemTokensIn);
            if (vars.mathErr != MathError.NO_ERROR) {
                return failOpaque(Error.MATH_ERROR, FailureInfo.REDEEM_EXCHANGE_TOKENS_CALCULATION_FAILED, uint(vars.mathErr));
            }
        } else {
            /*
             * We get the current exchange rate and calculate the amount to be redeemed:
             *  redeemTokens = redeemAmountIn / exchangeRate
             *  redeemAmount = redeemAmountIn
             */

            (vars.mathErr, vars.redeemTokens) = divScalarByExpTruncate(redeemAmountIn, Exp({mantissa: vars.exchangeRateMantissa}));
            if (vars.mathErr != MathError.NO_ERROR) {
                return failOpaque(Error.MATH_ERROR, FailureInfo.REDEEM_EXCHANGE_AMOUNT_CALCULATION_FAILED, uint(vars.mathErr));
            }

            vars.redeemAmount = redeemAmountIn;
        }

        /* Fail if redeem not allowed */
        uint allowed = bController.redeemAllowed(address(this), redeemer, vars.redeemTokens);

        if (allowed != 0) {
            return failOpaque(Error.BCONTROLLER_REJECTION, FailureInfo.REDEEM_BCONTROLLER_REJECTION, allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.REDEEM_FRESHNESS_CHECK);
        }

        /*
         * We calculate the new total supply and redeemer balance, checking for underflow:
         *  totalSupplyNew = totalSupply - redeemTokens
         *  accountTokensNew = accountTokens[redeemer] - redeemTokens
         */
        (vars.mathErr, vars.totalSupplyNew) = subUInt(totalSupply, vars.redeemTokens);
        if (vars.mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.REDEEM_NEW_TOTAL_SUPPLY_CALCULATION_FAILED, uint(vars.mathErr));
        }

        (vars.mathErr, vars.accountTokensNew) = subUInt(accountTokens[redeemer], vars.redeemTokens);
        if (vars.mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.REDEEM_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED, uint(vars.mathErr));
        }

        /* Fail gracefully if protocol has insufficient cash */
        if (getCashPrior() < vars.redeemAmount) {
            return fail(Error.TOKEN_INSUFFICIENT_CASH, FailureInfo.REDEEM_TRANSFER_OUT_NOT_POSSIBLE);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         * We invoke doTransferOut for the redeemer and the redeemAmount.
         *  Note: The bToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the bToken has redeemAmount less of cash.
         *  doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
         */
        doTransferOut(redeemer, vars.redeemAmount);

        /* We write previously calculated values into storage */
        totalSupply = vars.totalSupplyNew;
        accountTokens[redeemer] = vars.accountTokensNew;

        /* We emit a Transfer event, and a Redeem event */
        emit Transfer(redeemer, address(this), vars.redeemTokens);
        emit RedeemToken(redeemer, vars.redeemAmount, vars.redeemTokens);

        /* We call the defense hook */
        bController.redeemVerify(address(this), redeemer, vars.redeemAmount, vars.redeemTokens);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Sender borrows assets from the protocol to their own address
      * @param borrowAmount The amount of the underlying asset to borrow
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function borrowInternal(uint borrowAmount) internal nonReentrant returns (uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted borrow failed
            return fail(Error(error), FailureInfo.BORROW_ACCRUE_INTEREST_FAILED);
        }
        // borrowFresh emits borrow-specific logs on errors, so we don't need to
        return borrowFresh(msg.sender, borrowAmount);
    }

    struct BorrowLocalVars {
        MathError mathErr;
        uint accountBorrows;
        uint accountBorrowsNew;
        uint totalBorrowsNew;
    }

    /**
      * @notice Users borrow assets from the protocol to their own address
      * @param borrowAmount The amount of the underlying asset to borrow
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function borrowFresh(address payable borrower, uint borrowAmount) internal returns (uint) {
        /* Fail if borrow not allowed */
        uint allowed = bController.borrowAllowed(address(this), borrower, borrowAmount);
        if (allowed != 0) {
            return failOpaque(Error.BCONTROLLER_REJECTION, FailureInfo.BORROW_BCONTROLLER_REJECTION, allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.BORROW_FRESHNESS_CHECK);
        }

        /* Fail gracefully if protocol has insufficient underlying cash */
        if (getCashPrior() < borrowAmount) {
            return fail(Error.TOKEN_INSUFFICIENT_CASH, FailureInfo.BORROW_CASH_NOT_AVAILABLE);
        }

        BorrowLocalVars memory vars;

        /*
         * We calculate the new borrower and total borrow balances, failing on overflow:
         *  accountBorrowsNew = accountBorrows + borrowAmount
         *  totalBorrowsNew = totalBorrows + borrowAmount
         */
        (vars.mathErr, vars.accountBorrows) = borrowBalanceStoredInternal(borrower);
        if (vars.mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED, uint(vars.mathErr));
        }

        (vars.mathErr, vars.accountBorrowsNew) = addUInt(vars.accountBorrows, borrowAmount);
        if (vars.mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED, uint(vars.mathErr));
        }

        (vars.mathErr, vars.totalBorrowsNew) = addUInt(totalBorrows, borrowAmount);
        if (vars.mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED, uint(vars.mathErr));
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         * We invoke doTransferOut for the borrower and the borrowAmount.
         *  Note: The bToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the bToken borrowAmount less of cash.
         *  doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
         */
        doTransferOut(borrower, borrowAmount);

        /* We write the previously calculated values into storage */
        accountBorrows[borrower].principal = vars.accountBorrowsNew;
        accountBorrows[borrower].interestIndex = borrowIndex;
        totalBorrows = vars.totalBorrowsNew;

        /* We emit a Borrow event */
        emit BorrowToken(borrower, borrowAmount, vars.accountBorrowsNew, vars.totalBorrowsNew);

        /* We call the defense hook */
        bController.borrowVerify(address(this), borrower, borrowAmount);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Sender repays their own borrow
     * @param repayAmount The amount to repay
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function repayBorrowInternal(uint repayAmount) internal nonReentrant returns (uint, uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted borrow failed
            return (fail(Error(error), FailureInfo.REPAY_BORROW_ACCRUE_INTEREST_FAILED), 0);
        }
        // repayBorrowFresh emits repay-borrow-specific logs on errors, so we don't need to
        return repayBorrowFresh(msg.sender, msg.sender, repayAmount);
    }

    /**
     * @notice Sender repays a borrow belonging to borrower
     * @param borrower the account with the debt being payed off
     * @param repayAmount The amount to repay
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function repayBorrowBehalfInternal(address borrower, uint repayAmount) internal nonReentrant returns (uint, uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted borrow failed
            return (fail(Error(error), FailureInfo.REPAY_BEHALF_ACCRUE_INTEREST_FAILED), 0);
        }
        // repayBorrowFresh emits repay-borrow-specific logs on errors, so we don't need to
        return repayBorrowFresh(msg.sender, borrower, repayAmount);
    }

    struct RepayBorrowLocalVars {
        Error err;
        MathError mathErr;
        uint repayAmount;
        uint borrowerIndex;
        uint accountBorrows;
        uint accountBorrowsNew;
        uint totalBorrowsNew;
        uint actualRepayAmount;
    }

    /**
     * @notice Borrows are repaid by another user (possibly the borrower).
     * @param payer the account paying off the borrow
     * @param borrower the account with the debt being payed off
     * @param repayAmount the amount of undelrying tokens being returned
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function repayBorrowFresh(address payer, address borrower, uint repayAmount) internal returns (uint, uint) {
        /* Fail if repayBorrow not allowed */
        uint allowed = bController.repayBorrowAllowed(address(this), payer, borrower, repayAmount);
        if (allowed != 0) {
            return (failOpaque(Error.BCONTROLLER_REJECTION, FailureInfo.REPAY_BORROW_BCONTROLLER_REJECTION, allowed), 0);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            return (fail(Error.MARKET_NOT_FRESH, FailureInfo.REPAY_BORROW_FRESHNESS_CHECK), 0);
        }

        RepayBorrowLocalVars memory vars;

        /* We remember the original borrowerIndex for verification purposes */
        vars.borrowerIndex = accountBorrows[borrower].interestIndex;

        /* We fetch the amount the borrower owes, with accumulated interest */
        (vars.mathErr, vars.accountBorrows) = borrowBalanceStoredInternal(borrower);
        if (vars.mathErr != MathError.NO_ERROR) {
            return (failOpaque(Error.MATH_ERROR, FailureInfo.REPAY_BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED, uint(vars.mathErr)), 0);
        }

        /* If repayAmount == -1, repayAmount = accountBorrows */
        if (repayAmount == uint(-1)) {
            vars.repayAmount = vars.accountBorrows;
        } else {
            vars.repayAmount = repayAmount;
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         * We call doTransferIn for the payer and the repayAmount
         *  Note: The bToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the bToken holds an additional repayAmount of cash.
         *  doTransferIn reverts if anything goes wrong, since we can't be sure if side effects occurred.
         *   it returns the amount actually transferred, in case of a fee.
         */
        vars.actualRepayAmount = doTransferIn(payer, vars.repayAmount);

        /*
         * We calculate the new borrower and total borrow balances, failing on underflow:
         *  accountBorrowsNew = accountBorrows - actualRepayAmount
         *  totalBorrowsNew = totalBorrows - actualRepayAmount
         */
        (vars.mathErr, vars.accountBorrowsNew) = subUInt(vars.accountBorrows, vars.actualRepayAmount);
        require(vars.mathErr == MathError.NO_ERROR, "REPAY_BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED");

        (vars.mathErr, vars.totalBorrowsNew) = subUInt(totalBorrows, vars.actualRepayAmount);
        require(vars.mathErr == MathError.NO_ERROR, "REPAY_BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED");

        /* We write the previously calculated values into storage */
        accountBorrows[borrower].principal = vars.accountBorrowsNew;
        accountBorrows[borrower].interestIndex = borrowIndex;
        totalBorrows = vars.totalBorrowsNew;

        /* We emit a RepayBorrowToken event */
        emit RepayBorrowToken(payer, borrower, vars.actualRepayAmount, vars.accountBorrowsNew, vars.totalBorrowsNew);

        /* We call the defense hook */
        bController.repayBorrowVerify(address(this), payer, borrower, vars.actualRepayAmount, vars.borrowerIndex);

        return (uint(Error.NO_ERROR), vars.actualRepayAmount);
    }

    /**
     * @notice The sender liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @param borrower The borrower of this bToken to be liquidated
     * @param bTokenCollateral The market in which to seize collateral from the borrower
     * @param repayAmount The amount of the underlying borrowed asset to repay
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function liquidateBorrowInternal(address borrower, uint repayAmount, BTokenInterface bTokenCollateral) internal nonReentrant returns (uint, uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted liquidation failed
            return (fail(Error(error), FailureInfo.LIQUIDATE_ACCRUE_BORROW_INTEREST_FAILED), 0);
        }

        error = bTokenCollateral.accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted liquidation failed
            return (fail(Error(error), FailureInfo.LIQUIDATE_ACCRUE_COLLATERAL_INTEREST_FAILED), 0);
        }

        // liquidateBorrowFresh emits borrow-specific logs on errors, so we don't need to
        return liquidateBorrowFresh(msg.sender, borrower, repayAmount, bTokenCollateral);
    }

    /**
     * @notice The liquidator liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @param borrower The borrower of this bToken to be liquidated
     * @param liquidator The address repaying the borrow and seizing collateral
     * @param bTokenCollateral The market in which to seize collateral from the borrower
     * @param repayAmount The amount of the underlying borrowed asset to repay
     * @return (uint, uint) An error code (0=success, otherwise a failure, see ErrorReporter.sol), and the actual repayment amount.
     */
    function liquidateBorrowFresh(address liquidator, address borrower, uint repayAmount, BTokenInterface bTokenCollateral) internal returns (uint, uint) {
        /* Fail if liquidate not allowed */
        uint allowed = bController.liquidateBorrowAllowed(address(this), address(bTokenCollateral), liquidator, borrower, repayAmount);
        if (allowed != 0) {
            return (failOpaque(Error.BCONTROLLER_REJECTION, FailureInfo.LIQUIDATE_BCONTROLLER_REJECTION, allowed), 0);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            return (fail(Error.MARKET_NOT_FRESH, FailureInfo.LIQUIDATE_FRESHNESS_CHECK), 0);
        }

        /* Verify bTokenCollateral market's block number equals current block number */
        if (bTokenCollateral.accrualBlockNumber() != getBlockNumber()) {
            return (fail(Error.MARKET_NOT_FRESH, FailureInfo.LIQUIDATE_COLLATERAL_FRESHNESS_CHECK), 0);
        }

        /* Fail if borrower = liquidator */
        if (borrower == liquidator) {
            return (fail(Error.INVALID_ACCOUNT_PAIR, FailureInfo.LIQUIDATE_LIQUIDATOR_IS_BORROWER), 0);
        }

        /* Fail if repayAmount = 0 */
        if (repayAmount == 0) {
            return (fail(Error.INVALID_CLOSE_AMOUNT_REQUESTED, FailureInfo.LIQUIDATE_CLOSE_AMOUNT_IS_ZERO), 0);
        }

        /* Fail if repayAmount = -1 */
        if (repayAmount == uint(-1)) {
            return (fail(Error.INVALID_CLOSE_AMOUNT_REQUESTED, FailureInfo.LIQUIDATE_CLOSE_AMOUNT_IS_UINT_MAX), 0);
        }


        /* Fail if repayBorrow fails */
        (uint repayBorrowError, uint actualRepayAmount) = repayBorrowFresh(liquidator, borrower, repayAmount);
        if (repayBorrowError != uint(Error.NO_ERROR)) {
            return (fail(Error(repayBorrowError), FailureInfo.LIQUIDATE_REPAY_BORROW_FRESH_FAILED), 0);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /* We calculate the number of collateral tokens that will be seized */
        (uint amountSeizeError, uint seizeTokens) = bController.liquidateCalculateSeizeTokens(address(this), address(bTokenCollateral), actualRepayAmount);
        require(amountSeizeError == uint(Error.NO_ERROR), "LIQUIDATE_BCONTROLLER_CALCULATE_AMOUNT_SEIZE_FAILED");

        /* Revert if borrower collateral token balance < seizeTokens */
        require(bTokenCollateral.balanceOf(borrower) >= seizeTokens, "LIQUIDATE_SEIZE_TOO_MUCH");

        // If this is also the collateral, run seizeInternal to avoid re-entrancy, otherwise make an external call
        uint seizeError;
        if (address(bTokenCollateral) == address(this)) {
            seizeError = seizeInternal(address(this), liquidator, borrower, seizeTokens);
        } else {
            seizeError = bTokenCollateral.seize(liquidator, borrower, seizeTokens);
        }

        /* Revert if seize tokens fails (since we cannot be sure of side effects) */
        require(seizeError == uint(Error.NO_ERROR), "token seizure failed");

        /* We emit a LiquidateBorrowToken event */
        emit LiquidateBorrowToken(liquidator, borrower, actualRepayAmount, address(bTokenCollateral), seizeTokens);

        /* We call the defense hook */
        bController.liquidateBorrowVerify(address(this), address(bTokenCollateral), liquidator, borrower, actualRepayAmount, seizeTokens);

        return (uint(Error.NO_ERROR), actualRepayAmount);
    }

    /**
     * @notice Transfers collateral tokens (this market) to the liquidator.
     * @dev Will fail unless called by another bToken during the process of liquidation.
     *  Its absolutely critical to use msg.sender as the borrowed bToken and not a parameter.
     * @param liquidator The account receiving seized collateral
     * @param borrower The account having collateral seized
     * @param seizeTokens The number of bTokens to seize
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function seize(address liquidator, address borrower, uint seizeTokens) external nonReentrant returns (uint) {
        return seizeInternal(msg.sender, liquidator, borrower, seizeTokens);
    }

    /**
     * @notice Transfers collateral tokens (this market) to the liquidator.
     * @dev Called only during an in-kind liquidation, or by liquidateBorrow during the liquidation of another BToken.
     *  Its absolutely critical to use msg.sender as the seizer bToken and not a parameter.
     * @param seizerToken The contract seizing the collateral (i.e. borrowed bToken)
     * @param liquidator The account receiving seized collateral
     * @param borrower The account having collateral seized
     * @param seizeTokens The number of bTokens to seize
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function seizeInternal(address seizerToken, address liquidator, address borrower, uint seizeTokens) internal returns (uint) {
        /* Fail if seize not allowed */
        uint allowed = bController.seizeAllowed(address(this), seizerToken, liquidator, borrower, seizeTokens);
        if (allowed != 0) {
            return failOpaque(Error.BCONTROLLER_REJECTION, FailureInfo.LIQUIDATE_SEIZE_BCONTROLLER_REJECTION, allowed);
        }

        /* Fail if borrower = liquidator */
        if (borrower == liquidator) {
            return fail(Error.INVALID_ACCOUNT_PAIR, FailureInfo.LIQUIDATE_SEIZE_LIQUIDATOR_IS_BORROWER);
        }

        MathError mathErr;
        uint borrowerTokensNew;
        uint liquidatorTokensNew;

        /*
         * We calculate the new borrower and liquidator token balances, failing on underflow/overflow:
         *  borrowerTokensNew = accountTokens[borrower] - seizeTokens
         *  liquidatorTokensNew = accountTokens[liquidator] + seizeTokens
         */
        (mathErr, borrowerTokensNew) = subUInt(accountTokens[borrower], seizeTokens);
        if (mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.LIQUIDATE_SEIZE_BALANCE_DECREMENT_FAILED, uint(mathErr));
        }

        (mathErr, liquidatorTokensNew) = addUInt(accountTokens[liquidator], seizeTokens);
        if (mathErr != MathError.NO_ERROR) {
            return failOpaque(Error.MATH_ERROR, FailureInfo.LIQUIDATE_SEIZE_BALANCE_INCREMENT_FAILED, uint(mathErr));
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /* We write the previously calculated values into storage */
        accountTokens[borrower] = borrowerTokensNew;
        accountTokens[liquidator] = liquidatorTokensNew;

        /* Emit a Transfer event */
        emit Transfer(borrower, liquidator, seizeTokens);

        /* We call the defense hook */
        bController.seizeVerify(address(this), seizerToken, liquidator, borrower, seizeTokens);

        return uint(Error.NO_ERROR);
    }


    /*** Admin Functions ***/

    /**
      * @notice Begins transfer of admin rights. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
      * @dev Admin function to begin change of admin. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
      * @param newPendingAdmin New pending admin.
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setPendingAdmin(address payable newPendingAdmin) external returns (uint) {
        // Check caller = admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_PENDING_ADMIN_OWNER_CHECK);
        }

        // Save current value, if any, for inclusion in log
        address oldPendingAdmin = pendingAdmin;

        // Store pendingAdmin with value newPendingAdmin
        pendingAdmin = newPendingAdmin;

        // Emit NewPendingAdmin(oldPendingAdmin, newPendingAdmin)
        emit NewPendingAdmin(oldPendingAdmin, newPendingAdmin);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Accepts transfer of admin rights. msg.sender must be pendingAdmin
      * @dev Admin function for pending admin to accept role and update admin
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _acceptAdmin() external returns (uint) {
        // Check caller is pendingAdmin and pendingAdmin ≠ address(0)
        if (msg.sender != pendingAdmin || msg.sender == address(0)) {
            return fail(Error.UNAUTHORIZED, FailureInfo.ACCEPT_ADMIN_PENDING_ADMIN_CHECK);
        }

        // Save current values for inclusion in log
        address oldAdmin = admin;
        address oldPendingAdmin = pendingAdmin;

        // Store admin with value pendingAdmin
        admin = pendingAdmin;

        // Clear the pending value
        pendingAdmin = address(0);

        emit NewAdmin(oldAdmin, admin);
        emit NewPendingAdmin(oldPendingAdmin, pendingAdmin);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Sets a new bController for the market
      * @dev Admin function to set a new bController
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setBController(BControllerInterface newBController) public returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_BCONTROLLER_OWNER_CHECK);
        }

        BControllerInterface oldBController = bController;
        // Ensure invoke bController.isBController() returns true
        require(newBController.isBController(), "marker method returned false");

        // Set market's bController to newBController
        bController = newBController;

        // Emit NewBController(oldBController, newBController)
        emit NewBController(oldBController, newBController);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice accrues interest and sets a new reserve factor for the protocol using _setReserveFactorFresh
      * @dev Admin function to accrue interest and set a new reserve factor
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setReserveFactor(uint newReserveFactorMantissa) external nonReentrant returns (uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but on top of that we want to log the fact that an attempted reserve factor change failed.
            return fail(Error(error), FailureInfo.SET_RESERVE_FACTOR_ACCRUE_INTEREST_FAILED);
        }
        // _setReserveFactorFresh emits reserve-factor-specific logs on errors, so we don't need to.
        return _setReserveFactorFresh(newReserveFactorMantissa);
    }

    /**
      * @notice Sets a new reserve factor for the protocol (*requires fresh interest accrual)
      * @dev Admin function to set a new reserve factor
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setReserveFactorFresh(uint newReserveFactorMantissa) internal returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_RESERVE_FACTOR_ADMIN_CHECK);
        }

        // Verify market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.SET_RESERVE_FACTOR_FRESH_CHECK);
        }

        // Check newReserveFactor ≤ maxReserveFactor
        if (newReserveFactorMantissa > reserveFactorMaxMantissa) {
            return fail(Error.BAD_INPUT, FailureInfo.SET_RESERVE_FACTOR_BOUNDS_CHECK);
        }

        uint oldReserveFactorMantissa = reserveFactorMantissa;
        reserveFactorMantissa = newReserveFactorMantissa;

        emit NewTokenReserveFactor(oldReserveFactorMantissa, newReserveFactorMantissa);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Accrues interest and reduces reserves by transferring from msg.sender
     * @param addAmount Amount of addition to reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _addReservesInternal(uint addAmount) internal nonReentrant returns (uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but on top of that we want to log the fact that an attempted reduce reserves failed.
            return fail(Error(error), FailureInfo.ADD_RESERVES_ACCRUE_INTEREST_FAILED);
        }

        // _addReservesFresh emits reserve-addition-specific logs on errors, so we don't need to.
        (error, ) = _addReservesFresh(addAmount);
        return error;
    }

    /**
     * @notice Add reserves by transferring from caller
     * @dev Requires fresh interest accrual
     * @param addAmount Amount of addition to reserves
     * @return (uint, uint) An error code (0=success, otherwise a failure (see ErrorReporter.sol for details)) and the actual amount added, net token fees
     */
    function _addReservesFresh(uint addAmount) internal returns (uint, uint) {
        // totalReserves + actualAddAmount
        uint totalReservesNew;
        uint actualAddAmount;

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return (fail(Error.MARKET_NOT_FRESH, FailureInfo.ADD_RESERVES_FRESH_CHECK), actualAddAmount);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        /*
         * We call doTransferIn for the caller and the addAmount
         *  Note: The bToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the bToken holds an additional addAmount of cash.
         *  doTransferIn reverts if anything goes wrong, since we can't be sure if side effects occurred.
         *  it returns the amount actually transferred, in case of a fee.
         */

        actualAddAmount = doTransferIn(msg.sender, addAmount);

        totalReservesNew = totalReserves + actualAddAmount;

        /* Revert on overflow */
        require(totalReservesNew >= totalReserves, "add reserves unexpected overflow");

        // Store reserves[n+1] = reserves[n] + actualAddAmount
        totalReserves = totalReservesNew;

        /* Emit NewReserves(admin, actualAddAmount, reserves[n+1]) */
        emit ReservesAdded(msg.sender, actualAddAmount, totalReservesNew);

        /* Return (NO_ERROR, actualAddAmount) */
        return (uint(Error.NO_ERROR), actualAddAmount);
    }


    /**
     * @notice Accrues interest and reduces reserves by transferring to admin
     * @param reduceAmount Amount of reduction to reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _reduceReserves(uint reduceAmount) external nonReentrant returns (uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but on top of that we want to log the fact that an attempted reduce reserves failed.
            return fail(Error(error), FailureInfo.REDUCE_RESERVES_ACCRUE_INTEREST_FAILED);
        }
        // _reduceReservesFresh emits reserve-reduction-specific logs on errors, so we don't need to.
        return _reduceReservesFresh(reduceAmount);
    }

    /**
     * @notice Reduces reserves by transferring to admin
     * @dev Requires fresh interest accrual
     * @param reduceAmount Amount of reduction to reserves
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _reduceReservesFresh(uint reduceAmount) internal returns (uint) {
        // totalReserves - reduceAmount
        uint totalReservesNew;

        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.REDUCE_RESERVES_ADMIN_CHECK);
        }

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.REDUCE_RESERVES_FRESH_CHECK);
        }

        // Fail gracefully if protocol has insufficient underlying cash
        if (getCashPrior() < reduceAmount) {
            return fail(Error.TOKEN_INSUFFICIENT_CASH, FailureInfo.REDUCE_RESERVES_CASH_NOT_AVAILABLE);
        }

        // Check reduceAmount ≤ reserves[n] (totalReserves)
        if (reduceAmount > totalReserves) {
            return fail(Error.BAD_INPUT, FailureInfo.REDUCE_RESERVES_VALIDATION);
        }

        /////////////////////////
        // EFFECTS & INTERACTIONS
        // (No safe failures beyond this point)

        totalReservesNew = totalReserves - reduceAmount;
        // We checked reduceAmount <= totalReserves above, so this should never revert.
        require(totalReservesNew <= totalReserves, "reduce reserves unexpected underflow");

        // Store reserves[n+1] = reserves[n] - reduceAmount
        totalReserves = totalReservesNew;

        // doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
        doTransferOut(admin, reduceAmount);

        emit ReservesReduced(admin, reduceAmount, totalReservesNew);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice accrues interest and updates the interest rate model using _setInterestRateModelFresh
     * @dev Admin function to accrue interest and update the interest rate model
     * @param newInterestRateModel the new interest rate model to use
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setInterestRateModel(InterestRateModel newInterestRateModel) public returns (uint) {
        uint error = accrueInterest();
        if (error != uint(Error.NO_ERROR)) {
            // accrueInterest emits logs on errors, but on top of that we want to log the fact that an attempted change of interest rate model failed
            return fail(Error(error), FailureInfo.SET_INTEREST_RATE_MODEL_ACCRUE_INTEREST_FAILED);
        }
        // _setInterestRateModelFresh emits interest-rate-model-update-specific logs on errors, so we don't need to.
        return _setInterestRateModelFresh(newInterestRateModel);
    }

    /**
     * @notice updates the interest rate model (*requires fresh interest accrual)
     * @dev Admin function to update the interest rate model
     * @param newInterestRateModel the new interest rate model to use
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setInterestRateModelFresh(InterestRateModel newInterestRateModel) internal returns (uint) {

        // Used to store old model for use in the event that is emitted on success
        InterestRateModel oldInterestRateModel;

        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_INTEREST_RATE_MODEL_OWNER_CHECK);
        }

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            return fail(Error.MARKET_NOT_FRESH, FailureInfo.SET_INTEREST_RATE_MODEL_FRESH_CHECK);
        }

        // Track the market's current interest rate model
        oldInterestRateModel = interestRateModel;

        // Ensure invoke newInterestRateModel.isInterestRateModel() returns true
        require(newInterestRateModel.isInterestRateModel(), "marker method returned false");

        // Set the interest rate model to newInterestRateModel
        interestRateModel = newInterestRateModel;

        // Emit NewMarketTokenInterestRateModel(oldInterestRateModel, newInterestRateModel)
        emit NewMarketTokenInterestRateModel(oldInterestRateModel, newInterestRateModel);

        return uint(Error.NO_ERROR);
    }

    /*** Safe Token ***/

    /**
     * @notice Gets balance of this contract in terms of the underlying
     * @dev This excludes the value of the current message, if any
     * @return The quantity of underlying owned by this contract
     */
    function getCashPrior() internal view returns (uint);

    /**
     * @dev Performs a transfer in, reverting upon failure. Returns the amount actually transferred to the protocol, in case of a fee.
     *  This may revert due to insufficient balance or insufficient allowance.
     */
    function doTransferIn(address from, uint amount) internal returns (uint);

    /**
     * @dev Performs a transfer out, ideally returning an explanatory error code upon failure tather than reverting.
     *  If caller has not called checked protocol's balance, may revert due to insufficient cash held in the contract.
     *  If caller has checked protocol's balance, and verified it is >= amount, this should not revert in normal conditions.
     */
    function doTransferOut(address payable to, uint amount) internal;


    /*** Reentrancy Guard ***/

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     */
    modifier nonReentrant() {
        require(_notEntered, "re-entered");
        _notEntered = false;
        _;
        _notEntered = true; // get a gas-refund post-Istanbul
    }
}

contract PriceOracle {
    /// @notice Indicator that this is a PriceOracle contract (for inspection)
    bool public constant isPriceOracle = true;

    /**
      * @notice Get the underlying price of a bToken asset
      * @param bToken The bToken to get the underlying price of
      * @return The underlying asset price mantissa (scaled by 1e18).
      *  Zero means the price is unavailable.
      */
    function getUnderlyingPrice(BToken bToken) external view returns (uint);
}

contract BirdOracleInterface {

  function newChainRequest (
    string memory _url,
    string memory _key
  ) public;

  /**
   * Off-Chain oracle to update its consensus answer
   */
  function updatedChainRequest (
    uint _id,
    uint _valueResponse
  ) public;

  /**
   * access to saved ratings after Oracle consensus
   */
  function getRatingByAddress(address _addr) public view returns (uint);

  function getRatingByAddressString(string memory _str) public view returns (uint);

  function getRating() public view returns (uint);
}

contract BirdAdminStorage {
    /**
    * @notice Administrator for this contract
    */
    address public admin;

    /**
    * @notice Pending administrator for this contract
    */
    address public pendingAdmin;

    /**
    * @notice Active brains of Bird
    */
    address public implementation;

    /**
    * @notice Pending brains of Bird
    */
    address public pendingImplementation;
}

contract BControllerV1Storage is BirdAdminStorage {

    /**
     * @notice Oracle which gives the price of any given asset
     */
    PriceOracle public oracle;

    /**
     * @notice Multiplier used to calculate the maximum repayAmount when liquidating a borrow
     */
    uint public closeFactorMantissa;

    /**
     * @notice Multiplier representing the discount on collateral that a liquidator receives
     */
    uint public liquidationIncentiveMantissa;

    /**
     * @notice Max number of assets a single account can participate in (borrow or use as collateral)
     */
    uint public maxAssets;

    /**
     * @notice Per-account mapping of "assets you are in", capped by maxAssets
     */
    mapping(address => BToken[]) public accountAssets;

}

contract BControllerV2Storage is BControllerV1Storage {
    struct Market {
        /// @notice Whether or not this market is listed
        bool isListed;

        /**
         * @notice Multiplier representing the most one can borrow against their collateral in this market.
         *  For instance, 0.9 to allow borrowing 90% of collateral value.
         *  Must be between 0 and 1, and stored as a mantissa.
         */
        uint collateralFactorMantissa;

        /// @notice Per-market mapping of "accounts in this asset"
        mapping(address => bool) accountMembership;

        /// @notice Whether or not this market receives BRID+
        bool isBird;
    }

    /**
     * @notice Official mapping of bTokens -> Market metadata
     * @dev Used e.g. to determine if a market is supported
     */
    mapping(address => Market) public markets;


    /**
     * @notice The Pause Guardian can pause certain actions as a safety mechanism.
     *  Actions which allow users to remove their own assets cannot be paused.
     *  Liquidation / seizing / transfer can only be paused globally, not by market.
     */
    address public pauseGuardian;
    bool public _mintGuardianPaused;
    bool public _borrowGuardianPaused;
    bool public transferGuardianPaused;
    bool public seizeGuardianPaused;
    mapping(address => bool) public mintGuardianPaused;
    mapping(address => bool) public borrowGuardianPaused;
}

contract BControllerV3Storage is BControllerV2Storage {
    struct BirdMarketState {
        /// @notice The market's last updated birdBorrowIndex or birdSupplyIndex
        uint224 index;

        /// @notice The block number the index was last updated at
        uint32 block;
    }

    address birdAddress;

    uint maxRatingValue = 100 * 10**uint256(18);

    BirdOracleInterface birdOracle;

    /// @notice A list of all markets
    BToken[] public allMarkets;

    /// @notice The rate at which the flywheel distributes COMP, per block
    uint public birdRate;

    /// @notice The portion of birdRate that each market currently receives
    mapping(address => uint) public birdSpeeds;

    /// @notice The COMP market supply state for each market
    mapping(address => BirdMarketState) public birdSupplyState;

    /// @notice The COMP market borrow state for each market
    mapping(address => BirdMarketState) public birdBorrowState;

    /// @notice The COMP borrow index for each market for each supplier as of the last time they accrued COMP
    mapping(address => mapping(address => uint)) public birdSupplierIndex;

    /// @notice The COMP borrow index for each market for each borrower as of the last time they accrued COMP
    mapping(address => mapping(address => uint)) public birdBorrowerIndex;

    /// @notice The COMP accrued but not yet transferred to each user
    mapping(address => uint) public birdAccrued;
}

/**
 * @title BirdCore
 * @dev Storage for the bController is at this address, while execution is delegated to the `implementation`.
 * BTokens should reference this contract as their bController.
 */
contract BirdCore is BirdAdminStorage, BControllerErrorReporter {

    /**
      * @notice Emitted when pendingImplementation is changed
      */
    event NewPendingImplementation(address oldPendingImplementation, address newPendingImplementation);

    /**
      * @notice Emitted when pendingImplementation is accepted, which means bController implementation is updated
      */
    event NewImplementation(address oldImplementation, address newImplementation);

    /**
      * @notice Emitted when pendingAdmin is changed
      */
    event NewPendingAdmin(address oldPendingAdmin, address newPendingAdmin);

    /**
      * @notice Emitted when pendingAdmin is accepted, which means admin is updated
      */
    event NewAdmin(address oldAdmin, address newAdmin);

    constructor() public {
        // Set admin to caller
        admin = msg.sender;
    }

    /*** Admin Functions ***/
    function _setPendingImplementation(address newPendingImplementation) public returns (uint) {

        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_PENDING_IMPLEMENTATION_OWNER_CHECK);
        }

        address oldPendingImplementation = pendingImplementation;

        pendingImplementation = newPendingImplementation;

        emit NewPendingImplementation(oldPendingImplementation, pendingImplementation);

        return uint(Error.NO_ERROR);
    }

    /**
    * @notice Accepts new implementation of bController. msg.sender must be pendingImplementation
    * @dev Admin function for new implementation to accept it's role as implementation
    * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
    */
    function _acceptImplementation() public returns (uint) {
        // Check caller is pendingImplementation and pendingImplementation ≠ address(0)
        if (msg.sender != pendingImplementation || pendingImplementation == address(0)) {
            return fail(Error.UNAUTHORIZED, FailureInfo.ACCEPT_PENDING_IMPLEMENTATION_ADDRESS_CHECK);
        }

        // Save current values for inclusion in log
        address oldImplementation = implementation;
        address oldPendingImplementation = pendingImplementation;

        implementation = pendingImplementation;

        pendingImplementation = address(0);

        emit NewImplementation(oldImplementation, implementation);
        emit NewPendingImplementation(oldPendingImplementation, pendingImplementation);

        return uint(Error.NO_ERROR);
    }


    /**
      * @notice Begins transfer of admin rights. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
      * @dev Admin function to begin change of admin. The newPendingAdmin must call `_acceptAdmin` to finalize the transfer.
      * @param newPendingAdmin New pending admin.
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setPendingAdmin(address newPendingAdmin) public returns (uint) {
        // Check caller = admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_PENDING_ADMIN_OWNER_CHECK);
        }

        // Save current value, if any, for inclusion in log
        address oldPendingAdmin = pendingAdmin;

        // Store pendingAdmin with value newPendingAdmin
        pendingAdmin = newPendingAdmin;

        // Emit NewPendingAdmin(oldPendingAdmin, newPendingAdmin)
        emit NewPendingAdmin(oldPendingAdmin, newPendingAdmin);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Accepts transfer of admin rights. msg.sender must be pendingAdmin
      * @dev Admin function for pending admin to accept role and update admin
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _acceptAdmin() public returns (uint) {
        // Check caller is pendingAdmin and pendingAdmin ≠ address(0)
        if (msg.sender != pendingAdmin || msg.sender == address(0)) {
            return fail(Error.UNAUTHORIZED, FailureInfo.ACCEPT_ADMIN_PENDING_ADMIN_CHECK);
        }

        // Save current values for inclusion in log
        address oldAdmin = admin;
        address oldPendingAdmin = pendingAdmin;

        // Store admin with value pendingAdmin
        admin = pendingAdmin;

        // Clear the pending value
        pendingAdmin = address(0);

        emit NewAdmin(oldAdmin, admin);
        emit NewPendingAdmin(oldPendingAdmin, pendingAdmin);

        return uint(Error.NO_ERROR);
    }

    /**
     * @dev Delegates execution to an implementation contract.
     * It returns to the external caller whatever the implementation returns
     * or forwards reverts.
     */
    function () payable external {
        // delegate all other functions to current implementation
        (bool success, ) = implementation.delegatecall(msg.data);

        assembly {
              let free_mem_ptr := mload(0x40)
              returndatacopy(free_mem_ptr, 0, returndatasize)

              switch success
              case 0 { revert(free_mem_ptr, returndatasize) }
              default { return(free_mem_ptr, returndatasize) }
        }
    }
}

interface BirdPlus {
    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);

    /**
      * @notice Get the total number of tokens in circulation
      * @return The supply of tokens
      */
    function totalSupply() external view returns (uint256);

    /**
     * @notice Gets the balance of the specified address
     * @param owner The address from which the balance will be retrieved
     * @return The balance
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
      * @notice Transfer `amount` tokens from `msg.sender` to `dst`
      * @param dst The address of the destination account
      * @param amount The number of tokens to transfer
      * @return Whether or not the transfer succeeded
      */
    function transfer(address dst, uint256 amount) external returns (bool success);

    /**
      * @notice Transfer `amount` tokens from `src` to `dst`
      * @param src The address of the source account
      * @param dst The address of the destination account
      * @param amount The number of tokens to transfer
      * @return Whether or not the transfer succeeded
      */
    function transferFrom(address src, address dst, uint256 amount) external returns (bool success);

    /**
      * @notice Approve `spender` to transfer up to `amount` from `src`
      * @dev This will overwrite the approval amount for `spender`
      *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
      * @param spender The address of the account which may transfer tokens
      * @param amount The number of tokens that are approved (-1 means infinite)
      * @return Whether or not the approval succeeded
      */
    function approve(address spender, uint256 amount) external returns (bool success);

    /**
      * @notice Get the current allowance from `owner` for `spender`
      * @param owner The address of the account which owns the tokens to be spent
      * @param spender The address of the account which may transfer tokens
      * @return The number of tokens allowed to be spent (-1 means infinite)
      */
    function allowance(address owner, address spender) external view returns (uint256 remaining);

    event Transfer(address indexed from, address indexed to, uint256 amount);
    event Approval(address indexed owner, address indexed spender, uint256 amount);
}

/**
 * @title Bird's BController Contract
 */
contract BController is BControllerV3Storage, BControllerInterface, BControllerErrorReporter, Exponential {
    /// @notice Emitted when an admin supports a market
    event MarketListed(BToken bToken);

    /// @notice Emitted when an account enters a market
    event MarketEntered(BToken bToken, address account);

    /// @notice Emitted when an account exits a market
    event MarketExited(BToken bToken, address account);

    /// @notice Emitted when close factor is changed by admin
    event NewCloseFactor(uint oldCloseFactorMantissa, uint newCloseFactorMantissa);

    /// @notice Emitted when a collateral factor is changed by admin
    event NewCollateralFactor(BToken bToken, uint oldCollateralFactorMantissa, uint newCollateralFactorMantissa);

    /// @notice Emitted when liquidation incentive is changed by admin
    event NewLiquidationIncentive(uint oldLiquidationIncentiveMantissa, uint newLiquidationIncentiveMantissa);

    /// @notice Emitted when maxAssets is changed by admin
    event NewMaxAssets(uint oldMaxAssets, uint newMaxAssets);

    /// @notice Emitted when price oracle is changed
    event NewPriceOracle(PriceOracle oldPriceOracle, PriceOracle newPriceOracle);

    /// @notice Emitted when bird oracle is changed
    event NewBirdOracle(BirdOracleInterface oldBirdOracle, BirdOracleInterface newBirdOracle);

    /// @notice Emitted when pause guardian is changed
    event NewPauseGuardian(address oldPauseGuardian, address newPauseGuardian);

    /// @notice Emitted when an action is paused globally
    event ActionPaused(string action, bool pauseState);

    /// @notice Emitted when an action is paused on a market
    event ActionPaused(BToken bToken, string action, bool pauseState);

    /// @notice Emitted when market bird status is changed
    event MarketBird(BToken bToken, bool isBird);

     /// @notice Emitted when BRID+ address is changed
    event NewBirdPlusAddress(address oldBirdAddress, address newBirdAddress);

    /// @notice Emitted when BRID+ rate is changed
    event NewBirdPlusRate(uint oldBirdRate, uint newBirdRate);

    /// @notice Emitted when a new BRID+ speed is calculated for a market
    event BirdPlusSpeedUpdated(BToken indexed bToken, uint newSpeed);

    /// @notice Emitted when BRID+ is distributed to a supplier
    event DistributedSupplierBirdPlus(BToken indexed bToken, address indexed supplier, uint birdDelta, uint birdSupplyIndex);

    /// @notice Emitted when BRID+ is distributed to a borrower
    event DistributedBorrowerBirdPlus(BToken indexed bToken, address indexed borrower, uint birdDelta, uint birdBorrowIndex);

    /// @notice Emitted when borrow cap for a bToken is changed
    event NewBorrowCap(BToken indexed bToken, uint newBorrowCap);

    /// @notice Emitted when borrow cap guardian is changed
    event NewBorrowCapGuardian(address oldBorrowCapGuardian, address newBorrowCapGuardian);

    /// @notice The threshold above which the flywheel transfers BRID+, in wei
    uint public constant birdPlusClaimThreshold = 0.001e18;

    /// @notice The initial BRID+ index for a market
    uint224 public constant birdPlusInitialIndex = 1e36;

    // closeFactorMantissa must be strictly greater than this value
    uint internal constant closeFactorMinMantissa = 0.05e18; // 0.05

    // closeFactorMantissa must not exceed this value
    uint internal constant closeFactorMaxMantissa = 0.9e18; // 0.9

    // No collateralFactorMantissa may exceed this value
    uint internal constant collateralFactorMaxMantissa = 0.9e18; // 0.9

    // liquidationIncentiveMantissa must be no less than this value
    uint internal constant liquidationIncentiveMinMantissa = 1.0e18; // 1.0

    // liquidationIncentiveMantissa must be no greater than this value
    uint internal constant liquidationIncentiveMaxMantissa = 1.5e18; // 1.5

    constructor() public {
        admin = msg.sender;
    }

    /*** Assets You Are In ***/

    /**
     * @notice Returns the assets an account has entered
     * @param account The address of the account to pull assets for
     * @return A dynamic list with the assets the account has entered
     */
    function getAssetsIn(address account) external view returns (BToken[] memory) {
        BToken[] memory assetsIn = accountAssets[account];

        return assetsIn;
    }

    /**
     * @notice Returns whether the given account is entered in the given asset
     * @param account The address of the account to check
     * @param bToken The bToken to check
     * @return True if the account is in the asset, otherwise false.
     */
    function checkMembership(address account, BToken bToken) external view returns (bool) {
        return markets[address(bToken)].accountMembership[account];
    }

    /**
     * @notice Add assets to be included in account liquidity calculation
     * @param bTokens The list of addresses of the bToken markets to be enabled
     * @return Success indicator for whether each corresponding market was entered
     */
    function enterMarkets(address[] memory bTokens) public returns (uint[] memory) {
        uint len = bTokens.length;

        uint[] memory results = new uint[](len);
        for (uint i = 0; i < len; i++) {
            BToken bToken = BToken(bTokens[i]);

            results[i] = uint(addToMarketInternal(bToken, msg.sender));
        }

        return results;
    }

    /**
     * @notice Add the market to the borrower's "assets in" for liquidity calculations
     * @param bToken The market to enter
     * @param borrower The address of the account to modify
     * @return Success indicator for whether the market was entered
     */
    function addToMarketInternal(BToken bToken, address borrower) internal returns (Error) {
        Market storage marketToJoin = markets[address(bToken)];

        if (!marketToJoin.isListed) {
            // market is not listed, cannot join
            return Error.MARKET_NOT_LISTED;
        }

        if (marketToJoin.accountMembership[borrower] == true) {
            // already joined
            return Error.NO_ERROR;
        }

        if (accountAssets[borrower].length >= maxAssets)  {
            // no space, cannot join
            return Error.TOO_MANY_ASSETS;
        }

        // survived the gauntlet, add to list
        // NOTE: we store these somewhat redundantly as a significant optimization
        //  this avoids having to iterate through the list for the most common use cases
        //  that is, only when we need to perform liquidity checks
        //  and not whenever we want to check if an account is in a particular market
        marketToJoin.accountMembership[borrower] = true;
        accountAssets[borrower].push(bToken);

        emit MarketEntered(bToken, borrower);

        return Error.NO_ERROR;
    }

    /**
     * @notice Removes asset from sender's account liquidity calculation
     * @dev Sender must not have an outstanding borrow balance in the asset,
     *  or be providing necessary collateral for an outstanding borrow.
     * @param bTokenAddress The address of the asset to be removed
     * @return Whether or not the account successfully exited the market
     */
    function exitMarket(address bTokenAddress) external returns (uint) {
        BToken bToken = BToken(bTokenAddress);
        /* Get sender tokensHeld and amountOwed underlying from the bToken */
        (uint oErr, uint tokensHeld, uint amountOwed, ) = bToken.getAccountSnapshot(msg.sender);
        require(oErr == 0, "exitMarket: getAccountSnapshot failed"); // semi-opaque error code

        /* Fail if the sender has a borrow balance */
        if (amountOwed != 0) {
            return fail(Error.NONZERO_BORROW_BALANCE, FailureInfo.EXIT_MARKET_BALANCE_OWED);
        }

        /* Fail if the sender is not permitted to redeem all of their tokens */
        uint allowed = redeemAllowedInternal(bTokenAddress, msg.sender, tokensHeld);
        if (allowed != 0) {
            return failOpaque(Error.REJECTION, FailureInfo.EXIT_MARKET_REJECTION, allowed);
        }

        Market storage marketToExit = markets[address(bToken)];

        /* Return true if the sender is not already ‘in’ the market */
        if (!marketToExit.accountMembership[msg.sender]) {
            return uint(Error.NO_ERROR);
        }

        /* Set bToken account membership to false */
        delete marketToExit.accountMembership[msg.sender];

        /* Delete bToken from the account’s list of assets */
        // load into memory for faster iteration
        BToken[] memory userAssetList = accountAssets[msg.sender];
        uint len = userAssetList.length;
        uint assetIndex = len;
        for (uint i = 0; i < len; i++) {
            if (userAssetList[i] == bToken) {
                assetIndex = i;
                break;
            }
        }

        // We *must* have found the asset in the list or our redundant data structure is broken
        assert(assetIndex < len);

        // copy last item in list to location of item to be removed, reduce length by 1
        BToken[] storage storedList = accountAssets[msg.sender];
        storedList[assetIndex] = storedList[storedList.length - 1];
        storedList.length--;

        emit MarketExited(bToken, msg.sender);

        return uint(Error.NO_ERROR);
    }

    /*** Policy Hooks ***/

    /**
     * @notice Checks if the account should be allowed to mint tokens in the given market
     * @param bToken The market to verify the mint against
     * @param minter The account which would get the minted tokens
     * @param mintAmount The amount of underlying being supplied to the market in exchange for tokens
     * @return 0 if the mint is allowed, otherwise a semi-opaque error code (See ErrorReporter.sol)
     */
    function mintAllowed(address bToken, address minter, uint mintAmount) external returns (uint) {
        // Pausing is a very serious situation - we revert to sound the alarms
        require(!mintGuardianPaused[bToken], "mint is paused");

        // Shh - currently unused
        minter;
        mintAmount;

        if (!markets[bToken].isListed) {
            return uint(Error.MARKET_NOT_LISTED);
        }

        // Keep the flywheel moving
        updateBirdPlusSupplyIndex(bToken);
        distributeSupplierBirdPlus(bToken, minter, false);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Validates mint and reverts on rejection. May emit logs.
     * @param bToken Asset being minted
     * @param minter The address minting the tokens
     * @param actualMintAmount The amount of the underlying asset being minted
     * @param mintTokens The number of tokens being minted
     */
    function mintVerify(address bToken, address minter, uint actualMintAmount, uint mintTokens) external {
        // Shh - currently unused
        bToken;
        minter;
        actualMintAmount;
        mintTokens;

        // Shh - we don't ever want this hook to be marked pure
        if (false) {
            maxAssets = maxAssets;
        }
    }

    /**
     * @notice Checks if the account should be allowed to redeem tokens in the given market
     * @param bToken The market to verify the redeem against
     * @param redeemer The account which would redeem the tokens
     * @param redeemTokens The number of bTokens to exchange for the underlying asset in the market
     * @return 0 if the redeem is allowed, otherwise a semi-opaque error code (See ErrorReporter.sol)
     */
    function redeemAllowed(address bToken, address redeemer, uint redeemTokens) external returns (uint) {
        uint allowed = redeemAllowedInternal(bToken, redeemer, redeemTokens);
        if (allowed != uint(Error.NO_ERROR)) {
            return allowed;
        }

        // Keep the flywheel moving
        updateBirdPlusSupplyIndex(bToken);
        distributeSupplierBirdPlus(bToken, redeemer, false);

        return uint(Error.NO_ERROR);
    }

    function redeemAllowedInternal(address bToken, address redeemer, uint redeemTokens) internal view returns (uint) {
        if (!markets[bToken].isListed) {
            return uint(Error.MARKET_NOT_LISTED);
        }

        /* If the redeemer is not 'in' the market, then we can bypass the liquidity check */
        if (!markets[bToken].accountMembership[redeemer]) {
            return uint(Error.NO_ERROR);
        }

        /* Otherwise, perform a hypothetical liquidity check to guard against shortfall */
        (Error err, , uint shortfall) = getHypotheticalAccountLiquidityInternal(redeemer, BToken(bToken), redeemTokens, 0);
        if (err != Error.NO_ERROR) {
            return uint(err);
        }
        if (shortfall > 0) {
            return uint(Error.INSUFFICIENT_LIQUIDITY);
        }

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Validates redeem and reverts on rejection. May emit logs.
     * @param bToken Asset being redeemed
     * @param redeemer The address redeeming the tokens
     * @param redeemAmount The amount of the underlying asset being redeemed
     * @param redeemTokens The number of tokens being redeemed
     */
    function redeemVerify(address bToken, address redeemer, uint redeemAmount, uint redeemTokens) external {
        // Shh - currently unused
        bToken;
        redeemer;

        // Require tokens is zero or amount is also zero
        if (redeemTokens == 0 && redeemAmount > 0) {
            revert("redeemTokens zero");
        }
    }

    /**
     * @notice Checks if the account should be allowed to borrow the underlying asset of the given market
     * @param bToken The market to verify the borrow against
     * @param borrower The account which would borrow the asset
     * @param borrowAmount The amount of underlying the account would borrow
     * @return 0 if the borrow is allowed, otherwise a semi-opaque error code (See ErrorReporter.sol)
     */
    function borrowAllowed(address bToken, address borrower, uint borrowAmount) external returns (uint) {
        // Pausing is a very serious situation - we revert to sound the alarms
        require(!borrowGuardianPaused[bToken], "borrow is paused");

        if (!markets[bToken].isListed) {
            return uint(Error.MARKET_NOT_LISTED);
        }

        if (!markets[bToken].accountMembership[borrower]) {
            // only bTokens may call borrowAllowed if borrower not in market
            require(msg.sender == bToken, "sender must be bToken");

            // attempt to add borrower to the market
            Error err = addToMarketInternal(BToken(msg.sender), borrower);
            if (err != Error.NO_ERROR) {
                return uint(err);
            }

            // it should be impossible to break the important invariant
            assert(markets[bToken].accountMembership[borrower]);
        }

        if (oracle.getUnderlyingPrice(BToken(bToken)) == 0) {
            return uint(Error.PRICE_ERROR);
        }

        (Error err, , uint shortfall) = getHypotheticalAccountLiquidityInternal(borrower, BToken(bToken), 0, borrowAmount);
        if (err != Error.NO_ERROR) {
            return uint(err);
        }
        if (shortfall > 0) {
            return uint(Error.INSUFFICIENT_LIQUIDITY);
        }

        // Keep the flywheel moving
        Exp memory borrowIndex = Exp({mantissa: BToken(bToken).borrowIndex()});
        updateBirdBorrowIndex(bToken, borrowIndex);
        distributeBorrowerBirdPlus(bToken, borrower, borrowIndex, false);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Validates borrow and reverts on rejection. May emit logs.
     * @param bToken Asset whose underlying is being borrowed
     * @param borrower The address borrowing the underlying
     * @param borrowAmount The amount of the underlying asset requested to borrow
     */
    function borrowVerify(address bToken, address borrower, uint borrowAmount) external {
        // Shh - currently unused
        bToken;
        borrower;
        borrowAmount;

        // Shh - we don't ever want this hook to be marked pure
        if (false) {
            maxAssets = maxAssets;
        }
    }

    /**
     * @notice Checks if the account should be allowed to repay a borrow in the given market
     * @param bToken The market to verify the repay against
     * @param payer The account which would repay the asset
     * @param borrower The account which would borrowed the asset
     * @param repayAmount The amount of the underlying asset the account would repay
     * @return 0 if the repay is allowed, otherwise a semi-opaque error code (See ErrorReporter.sol)
     */
    function repayBorrowAllowed(
        address bToken,
        address payer,
        address borrower,
        uint repayAmount) external returns (uint) {
        // Shh - currently unused
        payer;
        borrower;
        repayAmount;

        if (!markets[bToken].isListed) {
            return uint(Error.MARKET_NOT_LISTED);
        }

        // Keep the flywheel moving
        Exp memory borrowIndex = Exp({mantissa: BToken(bToken).borrowIndex()});
        updateBirdBorrowIndex(bToken, borrowIndex);
        distributeBorrowerBirdPlus(bToken, borrower, borrowIndex, false);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Validates repayBorrow and reverts on rejection. May emit logs.
     * @param bToken Asset being repaid
     * @param payer The address repaying the borrow
     * @param borrower The address of the borrower
     * @param actualRepayAmount The amount of underlying being repaid
     */
    function repayBorrowVerify(
        address bToken,
        address payer,
        address borrower,
        uint actualRepayAmount,
        uint borrowerIndex) external {
        // Shh - currently unused
        bToken;
        payer;
        borrower;
        actualRepayAmount;
        borrowerIndex;

        // Shh - we don't ever want this hook to be marked pure
        if (false) {
            maxAssets = maxAssets;
        }
    }

    /**
     * @notice Checks if the liquidation should be allowed to occur
     * @param bTokenBorrowed Asset which was borrowed by the borrower
     * @param bTokenCollateral Asset which was used as collateral and will be seized
     * @param liquidator The address repaying the borrow and seizing the collateral
     * @param borrower The address of the borrower
     * @param repayAmount The amount of underlying being repaid
     */
    function liquidateBorrowAllowed(
        address bTokenBorrowed,
        address bTokenCollateral,
        address liquidator,
        address borrower,
        uint repayAmount) external returns (uint) {
        // Shh - currently unused
        liquidator;

        if (!markets[bTokenBorrowed].isListed || !markets[bTokenCollateral].isListed) {
            return uint(Error.MARKET_NOT_LISTED);
        }

        /* The borrower must have shortfall in order to be liquidatable */
        (Error err, , uint shortfall) = getAccountLiquidityInternal(borrower);
        if (err != Error.NO_ERROR) {
            return uint(err);
        }
        if (shortfall == 0) {
            return uint(Error.INSUFFICIENT_SHORTFALL);
        }

        /* The liquidator may not repay more than what is allowed by the closeFactor */
        uint borrowBalance = BToken(bTokenBorrowed).borrowBalanceStored(borrower);
        (MathError mathErr, uint maxClose) = mulScalarTruncate(Exp({mantissa: closeFactorMantissa}), borrowBalance);
        if (mathErr != MathError.NO_ERROR) {
            return uint(Error.MATH_ERROR);
        }
        if (repayAmount > maxClose) {
            return uint(Error.TOO_MUCH_REPAY);
        }

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Validates liquidateBorrow and reverts on rejection. May emit logs.
     * @param bTokenBorrowed Asset which was borrowed by the borrower
     * @param bTokenCollateral Asset which was used as collateral and will be seized
     * @param liquidator The address repaying the borrow and seizing the collateral
     * @param borrower The address of the borrower
     * @param actualRepayAmount The amount of underlying being repaid
     */
    function liquidateBorrowVerify(
        address bTokenBorrowed,
        address bTokenCollateral,
        address liquidator,
        address borrower,
        uint actualRepayAmount,
        uint seizeTokens) external {
        // Shh - currently unused
        bTokenBorrowed;
        bTokenCollateral;
        liquidator;
        borrower;
        actualRepayAmount;
        seizeTokens;

        // Shh - we don't ever want this hook to be marked pure
        if (false) {
            maxAssets = maxAssets;
        }
    }

    /**
     * @notice Checks if the seizing of assets should be allowed to occur
     * @param bTokenCollateral Asset which was used as collateral and will be seized
     * @param bTokenBorrowed Asset which was borrowed by the borrower
     * @param liquidator The address repaying the borrow and seizing the collateral
     * @param borrower The address of the borrower
     * @param seizeTokens The number of collateral tokens to seize
     */
    function seizeAllowed(
        address bTokenCollateral,
        address bTokenBorrowed,
        address liquidator,
        address borrower,
        uint seizeTokens) external returns (uint) {
        // Pausing is a very serious situation - we revert to sound the alarms
        require(!seizeGuardianPaused, "seize is paused");

        // Shh - currently unused
        seizeTokens;

        if (!markets[bTokenCollateral].isListed || !markets[bTokenBorrowed].isListed) {
            return uint(Error.MARKET_NOT_LISTED);
        }

        if (BToken(bTokenCollateral).bController() != BToken(bTokenBorrowed).bController()) {
            return uint(Error.BCONTROLLER_MISMATCH);
        }

        // Keep the flywheel moving
        updateBirdPlusSupplyIndex(bTokenCollateral);
        distributeSupplierBirdPlus(bTokenCollateral, borrower, false);
        distributeSupplierBirdPlus(bTokenCollateral, liquidator, false);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Validates seize and reverts on rejection. May emit logs.
     * @param bTokenCollateral Asset which was used as collateral and will be seized
     * @param bTokenBorrowed Asset which was borrowed by the borrower
     * @param liquidator The address repaying the borrow and seizing the collateral
     * @param borrower The address of the borrower
     * @param seizeTokens The number of collateral tokens to seize
     */
    function seizeVerify(
        address bTokenCollateral,
        address bTokenBorrowed,
        address liquidator,
        address borrower,
        uint seizeTokens) external {
        // Shh - currently unused
        bTokenCollateral;
        bTokenBorrowed;
        liquidator;
        borrower;
        seizeTokens;

        // Shh - we don't ever want this hook to be marked pure
        if (false) {
            maxAssets = maxAssets;
        }
    }

    /**
     * @notice Checks if the account should be allowed to transfer tokens in the given market
     * @param bToken The market to verify the transfer against
     * @param src The account which sources the tokens
     * @param dst The account which receives the tokens
     * @param transferTokens The number of bTokens to transfer
     * @return 0 if the transfer is allowed, otherwise a semi-opaque error code (See ErrorReporter.sol)
     */
    function transferAllowed(address bToken, address src, address dst, uint transferTokens) external returns (uint) {
        // Pausing is a very serious situation - we revert to sound the alarms
        require(!transferGuardianPaused, "transfer is paused");

        // Currently the only consideration is whether or not
        //  the src is allowed to redeem this many tokens
        uint allowed = redeemAllowedInternal(bToken, src, transferTokens);
        if (allowed != uint(Error.NO_ERROR)) {
            return allowed;
        }

        // Keep the flywheel moving
        updateBirdPlusSupplyIndex(bToken);
        distributeSupplierBirdPlus(bToken, src, false);
        distributeSupplierBirdPlus(bToken, dst, false);

        return uint(Error.NO_ERROR);
    }

    /**
     * @notice Validates transfer and reverts on rejection. May emit logs.
     * @param bToken Asset being transferred
     * @param src The account which sources the tokens
     * @param dst The account which receives the tokens
     * @param transferTokens The number of bTokens to transfer
     */
    function transferVerify(address bToken, address src, address dst, uint transferTokens) external {
        // Shh - currently unused
        bToken;
        src;
        dst;
        transferTokens;

        // Shh - we don't ever want this hook to be marked pure
        if (false) {
            maxAssets = maxAssets;
        }
    }

    /*** Liquidity/Liquidation Calculations ***/

    /**
     * @dev Local vars for avoiding stack-depth limits in calculating account liquidity.
     *  Note that `bTokenBalance` is the number of bTokens the account owns in the market,
     *  whereas `borrowBalance` is the amount of underlying that the account has borrowed.
     */
    struct AccountLiquidityLocalVars {
        uint sumCollateral;
        uint sumBorrowPlusEffects;
        uint bTokenBalance;
        uint borrowBalance;
        uint exchangeRateMantissa;
        uint oraclePriceMantissa;
        Exp collateralFactor;
        Exp exchangeRate;
        Exp oraclePrice;
        Exp tokensToDenom;
    }

    /**
     * @notice Determine the current account liquidity wrt collateral requirements
     * @return (possible error code (semi-opaque),
                account liquidity in excess of collateral requirements,
     *          account shortfall below collateral requirements)
     */
    function getAccountLiquidity(address account) public view returns (uint, uint, uint) {
        (Error err, uint liquidity, uint shortfall) = getHypotheticalAccountLiquidityInternal(account, BToken(0), 0, 0);

        return (uint(err), liquidity, shortfall);
    }

    /**
     * @notice Determine the current account liquidity wrt collateral requirements
     * @return (possible error code,
                account liquidity in excess of collateral requirements,
     *          account shortfall below collateral requirements)
     */
    function getAccountLiquidityInternal(address account) internal view returns (Error, uint, uint) {
        return getHypotheticalAccountLiquidityInternal(account, BToken(0), 0, 0);
    }

    /**
     * @notice Determine what the account liquidity would be if the given amounts were redeemed/borrowed
     * @param bTokenModify The market to hypothetically redeem/borrow in
     * @param account The account to determine liquidity for
     * @param redeemTokens The number of tokens to hypothetically redeem
     * @param borrowAmount The amount of underlying to hypothetically borrow
     * @return (possible error code (semi-opaque),
                hypothetical account liquidity in excess of collateral requirements,
     *          hypothetical account shortfall below collateral requirements)
     */
    function getHypotheticalAccountLiquidity(
        address account,
        address bTokenModify,
        uint redeemTokens,
        uint borrowAmount) public view returns (uint, uint, uint) {
        (Error err, uint liquidity, uint shortfall) = getHypotheticalAccountLiquidityInternal(account, BToken(bTokenModify), redeemTokens, borrowAmount);
        return (uint(err), liquidity, shortfall);
    }

    /**
     * @notice Determine what the account liquidity would be if the given amounts were redeemed/borrowed
     * @param bTokenModify The market to hypothetically redeem/borrow in
     * @param account The account to determine liquidity for
     * @param redeemTokens The number of tokens to hypothetically redeem
     * @param borrowAmount The amount of underlying to hypothetically borrow
     * @dev Note that we calculate the exchangeRateStored for each collateral bToken using stored data,
     *  without calculating accumulated interest.
     * @return (possible error code,
                hypothetical account liquidity in excess of collateral requirements,
     *          hypothetical account shortfall below collateral requirements)
     */
    function getHypotheticalAccountLiquidityInternal(
        address account,
        BToken bTokenModify,
        uint redeemTokens,
        uint borrowAmount) internal view returns (Error, uint, uint) {

        AccountLiquidityLocalVars memory vars; // Holds all our calculation results
        uint oErr;
        MathError mErr;

        uint ratingValue = getUserRating(account);

        // For each asset the account is in
        BToken[] memory assets = accountAssets[account];
        for (uint i = 0; i < assets.length; i++) {
            BToken asset = assets[i];

            // Read the balances and exchange rate from the bToken
            (oErr, vars.bTokenBalance, vars.borrowBalance, vars.exchangeRateMantissa) = asset.getAccountSnapshot(account);
            if (oErr != 0) { // semi-opaque error code, we assume NO_ERROR == 0 is invariant between upgrades
                return (Error.SNAPSHOT_ERROR, 0, 0);
            }

            // Add the rating value along with existing collateral value
            uint newCollateralFactorMantissa = add(markets[address(asset)].collateralFactorMantissa, ratingValue);
            vars.collateralFactor = Exp({mantissa: newCollateralFactorMantissa});
            
            //vars.collateralFactor = Exp({mantissa: markets[address(asset)].collateralFactorMantissa});
            vars.exchangeRate = Exp({mantissa: vars.exchangeRateMantissa});

            // Get the normalized price of the asset
            vars.oraclePriceMantissa = oracle.getUnderlyingPrice(asset);
            if (vars.oraclePriceMantissa == 0) {
                return (Error.PRICE_ERROR, 0, 0);
            }
            vars.oraclePrice = Exp({mantissa: vars.oraclePriceMantissa});
            // Pre-birdute a conversion factor from tokens -> ether (normalized price value)
            (mErr, vars.tokensToDenom) = mulExp3(vars.collateralFactor, vars.exchangeRate, vars.oraclePrice);
            if (mErr != MathError.NO_ERROR) {
                return (Error.MATH_ERROR, 0, 0);
            }

            // sumCollateral += tokensToDenom * bTokenBalance
            (mErr, vars.sumCollateral) = mulScalarTruncateAddUInt(vars.tokensToDenom, vars.bTokenBalance, vars.sumCollateral);
            if (mErr != MathError.NO_ERROR) {
                return (Error.MATH_ERROR, 0, 0);
            }

            // sumBorrowPlusEffects += oraclePrice * borrowBalance
            (mErr, vars.sumBorrowPlusEffects) = mulScalarTruncateAddUInt(vars.oraclePrice, vars.borrowBalance, vars.sumBorrowPlusEffects);
            if (mErr != MathError.NO_ERROR) {
                return (Error.MATH_ERROR, 0, 0);
            }

            // Calculate effects of interacting with bTokenModify
            if (asset == bTokenModify) {
                // redeem effect
                // sumBorrowPlusEffects += tokensToDenom * redeemTokens
                (mErr, vars.sumBorrowPlusEffects) = mulScalarTruncateAddUInt(vars.tokensToDenom, redeemTokens, vars.sumBorrowPlusEffects);
                if (mErr != MathError.NO_ERROR) {
                    return (Error.MATH_ERROR, 0, 0);
                }

                // borrow effect
                // sumBorrowPlusEffects += oraclePrice * borrowAmount
                (mErr, vars.sumBorrowPlusEffects) = mulScalarTruncateAddUInt(vars.oraclePrice, borrowAmount, vars.sumBorrowPlusEffects);
                if (mErr != MathError.NO_ERROR) {
                    return (Error.MATH_ERROR, 0, 0);
                }
            }
        }

        // These are safe, as the underflow condition is checked first
        if (vars.sumCollateral > vars.sumBorrowPlusEffects) {
            return (Error.NO_ERROR, vars.sumCollateral - vars.sumBorrowPlusEffects, 0);
        } else {
            return (Error.NO_ERROR, 0, vars.sumBorrowPlusEffects - vars.sumCollateral);
        }
    }

    function getUserRating(address account) internal view returns (uint) {

        // Get the rating value from the BirdOracle for the account
        uint userRatingValue = birdOracle.getRatingByAddress(account);

        if (userRatingValue > maxRatingValue) {
            userRatingValue = maxRatingValue;
        }

        return userRatingValue / 10;
    }

    function add(uint a, uint b) internal pure returns (uint) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @notice Calculate number of tokens of collateral asset to seize given an underlying amount
     * @dev Used in liquidation (called in bToken.liquidateBorrowFresh)
     * @param bTokenBorrowed The address of the borrowed bToken
     * @param bTokenCollateral The address of the collateral bToken
     * @param actualRepayAmount The amount of bTokenBorrowed underlying to convert into bTokenCollateral tokens
     * @return (errorCode, number of bTokenCollateral tokens to be seized in a liquidation)
     */
    function liquidateCalculateSeizeTokens(address bTokenBorrowed, address bTokenCollateral, uint actualRepayAmount) external view returns (uint, uint) {
        /* Read oracle prices for borrowed and collateral markets */
        uint priceBorrowedMantissa = oracle.getUnderlyingPrice(BToken(bTokenBorrowed));
        uint priceCollateralMantissa = oracle.getUnderlyingPrice(BToken(bTokenCollateral));
        if (priceBorrowedMantissa == 0 || priceCollateralMantissa == 0) {
            return (uint(Error.PRICE_ERROR), 0);
        }

        /*
         * Get the exchange rate and calculate the number of collateral tokens to seize:
         *  seizeAmount = actualRepayAmount * liquidationIncentive * priceBorrowed / priceCollateral
         *  seizeTokens = seizeAmount / exchangeRate
         *   = actualRepayAmount * (liquidationIncentive * priceBorrowed) / (priceCollateral * exchangeRate)
         */
        uint exchangeRateMantissa = BToken(bTokenCollateral).exchangeRateStored(); // Note: reverts on error
        uint seizeTokens;
        Exp memory numerator;
        Exp memory denominator;
        Exp memory ratio;
        MathError mathErr;

        (mathErr, numerator) = mulExp(liquidationIncentiveMantissa, priceBorrowedMantissa);
        if (mathErr != MathError.NO_ERROR) {
            return (uint(Error.MATH_ERROR), 0);
        }

        (mathErr, denominator) = mulExp(priceCollateralMantissa, exchangeRateMantissa);
        if (mathErr != MathError.NO_ERROR) {
            return (uint(Error.MATH_ERROR), 0);
        }

        (mathErr, ratio) = divExp(numerator, denominator);
        if (mathErr != MathError.NO_ERROR) {
            return (uint(Error.MATH_ERROR), 0);
        }

        (mathErr, seizeTokens) = mulScalarTruncate(ratio, actualRepayAmount);
        if (mathErr != MathError.NO_ERROR) {
            return (uint(Error.MATH_ERROR), 0);
        }

        return (uint(Error.NO_ERROR), seizeTokens);
    }

    /*** Admin Functions ***/

    /**
      * @notice Sets a new price oracle for the bController
      * @dev Admin function to set a new price oracle
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setPriceOracle(PriceOracle newOracle) public returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_PRICE_ORACLE_OWNER_CHECK);
        }

        // Track the old oracle for the bController
        PriceOracle oldOracle = oracle;

        // Set bController's oracle to newOracle
        oracle = newOracle;

        // Emit NewPriceOracle(oldOracle, newOracle)
        emit NewPriceOracle(oldOracle, newOracle);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Sets a new bird oracle for the bController
      * @dev Admin function to set a new bird oracle
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _setBirdOracle(BirdOracleInterface newBirdOracle) public returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_PRICE_ORACLE_OWNER_CHECK);
        }
        // Set bController's birdOracle to newBirdOracle
        birdOracle = newBirdOracle;
    }

    /**
      * @notice Sets the closeFactor used when liquidating borrows
      * @dev Admin function to set closeFactor
      * @param newCloseFactorMantissa New close factor, scaled by 1e18
      * @return uint 0=success, otherwise a failure. (See ErrorReporter for details)
      */
    function _setCloseFactor(uint newCloseFactorMantissa) external returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_CLOSE_FACTOR_OWNER_CHECK);
        }

        Exp memory newCloseFactorExp = Exp({mantissa: newCloseFactorMantissa});
        Exp memory lowLimit = Exp({mantissa: closeFactorMinMantissa});
        if (lessThanOrEqualExp(newCloseFactorExp, lowLimit)) {
            return fail(Error.INVALID_CLOSE_FACTOR, FailureInfo.SET_CLOSE_FACTOR_VALIDATION);
        }

        Exp memory highLimit = Exp({mantissa: closeFactorMaxMantissa});
        if (lessThanExp(highLimit, newCloseFactorExp)) {
            return fail(Error.INVALID_CLOSE_FACTOR, FailureInfo.SET_CLOSE_FACTOR_VALIDATION);
        }

        uint oldCloseFactorMantissa = closeFactorMantissa;
        closeFactorMantissa = newCloseFactorMantissa;
        emit NewCloseFactor(oldCloseFactorMantissa, closeFactorMantissa);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Sets the collateralFactor for a market
      * @dev Admin function to set per-market collateralFactor
      * @param bToken The market to set the factor on
      * @param newCollateralFactorMantissa The new collateral factor, scaled by 1e18
      * @return uint 0=success, otherwise a failure. (See ErrorReporter for details)
      */
    function _setCollateralFactor(BToken bToken, uint newCollateralFactorMantissa) external returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_COLLATERAL_FACTOR_OWNER_CHECK);
        }

        // Verify market is listed
        Market storage market = markets[address(bToken)];
        if (!market.isListed) {
            return fail(Error.MARKET_NOT_LISTED, FailureInfo.SET_COLLATERAL_FACTOR_NO_EXISTS);
        }

        Exp memory newCollateralFactorExp = Exp({mantissa: newCollateralFactorMantissa});

        // Check collateral factor <= 0.9
        Exp memory highLimit = Exp({mantissa: collateralFactorMaxMantissa});
        if (lessThanExp(highLimit, newCollateralFactorExp)) {
            return fail(Error.INVALID_COLLATERAL_FACTOR, FailureInfo.SET_COLLATERAL_FACTOR_VALIDATION);
        }

        // If collateral factor != 0, fail if price == 0
        if (newCollateralFactorMantissa != 0 && oracle.getUnderlyingPrice(bToken) == 0) {
            return fail(Error.PRICE_ERROR, FailureInfo.SET_COLLATERAL_FACTOR_WITHOUT_PRICE);
        }

        // Set market's collateral factor to new collateral factor, remember old value
        uint oldCollateralFactorMantissa = market.collateralFactorMantissa;
        market.collateralFactorMantissa = newCollateralFactorMantissa;

        // Emit event with asset, old collateral factor, and new collateral factor
        emit NewCollateralFactor(bToken, oldCollateralFactorMantissa, newCollateralFactorMantissa);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Sets maxAssets which controls how many markets can be entered
      * @dev Admin function to set maxAssets
      * @param newMaxAssets New max assets
      * @return uint 0=success, otherwise a failure. (See ErrorReporter for details)
      */
    function _setMaxAssets(uint newMaxAssets) external returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_MAX_ASSETS_OWNER_CHECK);
        }

        uint oldMaxAssets = maxAssets;
        maxAssets = newMaxAssets;
        emit NewMaxAssets(oldMaxAssets, newMaxAssets);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Sets liquidationIncentive
      * @dev Admin function to set liquidationIncentive
      * @param newLiquidationIncentiveMantissa New liquidationIncentive scaled by 1e18
      * @return uint 0=success, otherwise a failure. (See ErrorReporter for details)
      */
    function _setLiquidationIncentive(uint newLiquidationIncentiveMantissa) external returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_LIQUIDATION_INCENTIVE_OWNER_CHECK);
        }

        // Check de-scaled min <= newLiquidationIncentive <= max
        Exp memory newLiquidationIncentive = Exp({mantissa: newLiquidationIncentiveMantissa});
        Exp memory minLiquidationIncentive = Exp({mantissa: liquidationIncentiveMinMantissa});
        if (lessThanExp(newLiquidationIncentive, minLiquidationIncentive)) {
            return fail(Error.INVALID_LIQUIDATION_INCENTIVE, FailureInfo.SET_LIQUIDATION_INCENTIVE_VALIDATION);
        }

        Exp memory maxLiquidationIncentive = Exp({mantissa: liquidationIncentiveMaxMantissa});
        if (lessThanExp(maxLiquidationIncentive, newLiquidationIncentive)) {
            return fail(Error.INVALID_LIQUIDATION_INCENTIVE, FailureInfo.SET_LIQUIDATION_INCENTIVE_VALIDATION);
        }

        // Save current value for use in log
        uint oldLiquidationIncentiveMantissa = liquidationIncentiveMantissa;

        // Set liquidation incentive to new incentive
        liquidationIncentiveMantissa = newLiquidationIncentiveMantissa;

        // Emit event with old incentive, new incentive
        emit NewLiquidationIncentive(oldLiquidationIncentiveMantissa, newLiquidationIncentiveMantissa);

        return uint(Error.NO_ERROR);
    }

    /**
      * @notice Add the market to the markets mapping and set it as listed
      * @dev Admin function to set isListed and add support for the market
      * @param bToken The address of the market (token) to list
      * @return uint 0=success, otherwise a failure. (See enum Error for details)
      */
    function _supportMarket(BToken bToken) external returns (uint) {
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SUPPORT_MARKET_OWNER_CHECK);
        }

        if (markets[address(bToken)].isListed) {
            return fail(Error.MARKET_ALREADY_LISTED, FailureInfo.SUPPORT_MARKET_EXISTS);
        }

        bToken.isBToken(); // Sanity check to make sure its really a BToken

        markets[address(bToken)] = Market({isListed: true, isBird: false, collateralFactorMantissa: 0});

        _addMarketInternal(address(bToken));

        emit MarketListed(bToken);

        return uint(Error.NO_ERROR);
    }

    function _addMarketInternal(address bToken) internal {
        for (uint i = 0; i < allMarkets.length; i ++) {
            require(allMarkets[i] != BToken(bToken), "market already added");
        }
        allMarkets.push(BToken(bToken));
    }

    /**
     * @notice Admin function to change the Pause Guardian
     * @param newPauseGuardian The address of the new Pause Guardian
     * @return uint 0=success, otherwise a failure. (See enum Error for details)
     */
    function _setPauseGuardian(address newPauseGuardian) public returns (uint) {
        if (msg.sender != admin) {
            return fail(Error.UNAUTHORIZED, FailureInfo.SET_PAUSE_GUARDIAN_OWNER_CHECK);
        }

        // Save current value for inclusion in log
        address oldPauseGuardian = pauseGuardian;

        // Store pauseGuardian with value newPauseGuardian
        pauseGuardian = newPauseGuardian;

        // Emit NewPauseGuardian(OldPauseGuardian, NewPauseGuardian)
        emit NewPauseGuardian(oldPauseGuardian, pauseGuardian);

        return uint(Error.NO_ERROR);
    }

    function _setMintPaused(BToken bToken, bool state) public returns (bool) {
        require(markets[address(bToken)].isListed, "cannot pause a market that is not listed");
        require(msg.sender == pauseGuardian || msg.sender == admin, "only pause guardian and admin can pause");
        require(msg.sender == admin || state == true, "only admin can unpause");

        mintGuardianPaused[address(bToken)] = state;
        emit ActionPaused(bToken, "Mint", state);
        return state;
    }

    function _setBorrowPaused(BToken bToken, bool state) public returns (bool) {
        require(markets[address(bToken)].isListed, "cannot pause a market that is not listed");
        require(msg.sender == pauseGuardian || msg.sender == admin, "only pause guardian and admin can pause");
        require(msg.sender == admin || state == true, "only admin can unpause");

        borrowGuardianPaused[address(bToken)] = state;
        emit ActionPaused(bToken, "Borrow", state);
        return state;
    }

    function _setTransferPaused(bool state) public returns (bool) {
        require(msg.sender == pauseGuardian || msg.sender == admin, "only pause guardian and admin can pause");
        require(msg.sender == admin || state == true, "only admin can unpause");

        transferGuardianPaused = state;
        emit ActionPaused("Transfer", state);
        return state;
    }

    function _setSeizePaused(bool state) public returns (bool) {
        require(msg.sender == pauseGuardian || msg.sender == admin, "only pause guardian and admin can pause");
        require(msg.sender == admin || state == true, "only admin can unpause");

        seizeGuardianPaused = state;
        emit ActionPaused("Seize", state);
        return state;
    }

    function _become(BirdCore birdCore) public {
        require(msg.sender == birdCore.admin(), "only birdCore admin can change brains");
        require(birdCore._acceptImplementation() == 0, "change not authorized");
    }

    /**
     * @notice Checks caller is admin, or this contract is becoming the new implementation
     */
    function adminOrInitializing() internal view returns (bool) {
        return msg.sender == admin || msg.sender == implementation;
    }

    /*** Bird+ Distribution ***/

    /**
     * @notice Recalculate and update BRID+ speeds for all BRID+ markets
     */
    function refreshBirdSpeeds() public {
        require(msg.sender == tx.origin, "only externally owned accounts may refresh speeds");
        refreshBirdPlusSpeedsInternal();
    }

    function refreshBirdPlusSpeedsInternal() internal {
        BToken[] memory allMarkets_ = allMarkets;

        for (uint i = 0; i < allMarkets_.length; i++) {
            BToken bToken = allMarkets_[i];
            Exp memory borrowIndex = Exp({mantissa: bToken.borrowIndex()});
            updateBirdPlusSupplyIndex(address(bToken));
            updateBirdBorrowIndex(address(bToken), borrowIndex);
        }

        Exp memory totalUtility = Exp({mantissa: 0});
        Exp[] memory utilities = new Exp[](allMarkets_.length);
        for (uint i = 0; i < allMarkets_.length; i++) {
            BToken bToken = allMarkets_[i];
            if (markets[address(bToken)].isBird) {
                Exp memory assetPrice = Exp({mantissa: oracle.getUnderlyingPrice(bToken)});
                Exp memory utility = mul_(assetPrice, bToken.totalBorrows());
                utilities[i] = utility;
                totalUtility = add_(totalUtility, utility);
            }
        }

        for (uint i = 0; i < allMarkets_.length; i++) {
            BToken bToken = allMarkets[i];
            uint newSpeed = totalUtility.mantissa > 0 ? mul_(birdRate, div_(utilities[i], totalUtility)) : 0;
            birdSpeeds[address(bToken)] = newSpeed;
            emit BirdPlusSpeedUpdated(bToken, newSpeed);
        }
    }

    /**
     * @notice Accrue BRID+ to the market by updating the supply index
     * @param bToken The market whose supply index to update
     */
    function updateBirdPlusSupplyIndex(address bToken) internal {
        BirdMarketState storage supplyState = birdSupplyState[bToken];
        uint supplySpeed = birdSpeeds[bToken];
        uint blockNumber = getBlockNumber();
        uint deltaBlocks = sub_(blockNumber, uint(supplyState.block));
        if (deltaBlocks > 0 && supplySpeed > 0) {
            uint supplyTokens = BToken(bToken).totalSupply();
            uint birdAccrued = mul_(deltaBlocks, supplySpeed);
            Double memory ratio = supplyTokens > 0 ? fraction(birdAccrued, supplyTokens) : Double({mantissa: 0});
            Double memory index = add_(Double({mantissa: supplyState.index}), ratio);
            birdSupplyState[bToken] = BirdMarketState({
                index: safe224(index.mantissa, "new index exceeds 224 bits"),
                block: safe32(blockNumber, "block number exceeds 32 bits")
            });
        } else if (deltaBlocks > 0) {
            supplyState.block = safe32(blockNumber, "block number exceeds 32 bits");
        }
    }

    /**
     * @notice Accrue BRID+ to the market by updating the borrow index
     * @param bToken The market whose borrow index to update
     */
    function updateBirdBorrowIndex(address bToken, Exp memory marketBorrowIndex) internal {
        BirdMarketState storage borrowState = birdBorrowState[bToken];
        uint borrowSpeed = birdSpeeds[bToken];
        uint blockNumber = getBlockNumber();
        uint deltaBlocks = sub_(blockNumber, uint(borrowState.block));
        if (deltaBlocks > 0 && borrowSpeed > 0) {
            uint borrowAmount = div_(BToken(bToken).totalBorrows(), marketBorrowIndex);
            uint birdAccrued = mul_(deltaBlocks, borrowSpeed);
            Double memory ratio = borrowAmount > 0 ? fraction(birdAccrued, borrowAmount) : Double({mantissa: 0});
            Double memory index = add_(Double({mantissa: borrowState.index}), ratio);
            birdBorrowState[bToken] = BirdMarketState({
                index: safe224(index.mantissa, "new index exceeds 224 bits"),
                block: safe32(blockNumber, "block number exceeds 32 bits")
            });
        } else if (deltaBlocks > 0) {
            borrowState.block = safe32(blockNumber, "block number exceeds 32 bits");
        }
    }

    /**
     * @notice Calculate BRID+ accrued by a supplier and possibly transfer it to them
     * @param bToken The market in which the supplier is interacting
     * @param supplier The address of the supplier to distribute BRID+ to
     */
    function distributeSupplierBirdPlus(address bToken, address supplier, bool distributeAll) internal {
        BirdMarketState storage supplyState = birdSupplyState[bToken];
        Double memory supplyIndex = Double({mantissa: supplyState.index});
        Double memory supplierIndex = Double({mantissa: birdSupplierIndex[bToken][supplier]});
        birdSupplierIndex[bToken][supplier] = supplyIndex.mantissa;

        if (supplierIndex.mantissa == 0 && supplyIndex.mantissa > 0) {
            supplierIndex.mantissa = birdPlusInitialIndex;
        }

        Double memory deltaIndex = sub_(supplyIndex, supplierIndex);
        uint supplierTokens = BToken(bToken).balanceOf(supplier);
        uint supplierDelta = mul_(supplierTokens, deltaIndex);
        uint supplierAccrued = add_(birdAccrued[supplier], supplierDelta);
        birdAccrued[supplier] = transferBirdPlus(supplier, supplierAccrued, distributeAll ? 0 : birdPlusClaimThreshold);
        emit DistributedSupplierBirdPlus(BToken(bToken), supplier, supplierDelta, supplyIndex.mantissa);
    }

    /**
     * @notice Calculate BRID+ accrued by a borrower and possibly transfer it to them
     * @dev Borrowers will not begin to accrue until after the first interaction with the protocol.
     * @param bToken The market in which the borrower is interacting
     * @param borrower The address of the borrower to distribute BRID+ to
     */
    function distributeBorrowerBirdPlus(address bToken, address borrower, Exp memory marketBorrowIndex, bool distributeAll) internal {
        BirdMarketState storage borrowState = birdBorrowState[bToken];
        Double memory borrowIndex = Double({mantissa: borrowState.index});
        Double memory borrowerIndex = Double({mantissa: birdBorrowerIndex[bToken][borrower]});
        birdBorrowerIndex[bToken][borrower] = borrowIndex.mantissa;

        if (borrowerIndex.mantissa > 0) {
            Double memory deltaIndex = sub_(borrowIndex, borrowerIndex);
            uint borrowerAmount = div_(BToken(bToken).borrowBalanceStored(borrower), marketBorrowIndex);
            uint borrowerDelta = mul_(borrowerAmount, deltaIndex);
            uint borrowerAccrued = add_(birdAccrued[borrower], borrowerDelta);
            birdAccrued[borrower] = transferBirdPlus(borrower, borrowerAccrued, distributeAll ? 0 : birdPlusClaimThreshold);
            emit DistributedBorrowerBirdPlus(BToken(bToken), borrower, borrowerDelta, borrowIndex.mantissa);
        }
    }

    /**
     * @notice Transfer BRID+ to the user, if they are above the threshold
     * @dev Note: If there is not enough BRID+, we do not perform the transfer all.
     * @param user The address of the user to transfer BRID+ to
     * @param userAccrued The amount of BRID+ to (possibly) transfer
     * @return The amount of BRID+ which was NOT transferred to the user
     */
    function transferBirdPlus(address user, uint userAccrued, uint threshold) internal returns (uint) {
        if (userAccrued >= threshold && userAccrued > 0) {
            BirdPlus birdPlus = BirdPlus(getBirdPlusAddress());
            require(birdPlus != BirdPlus(0x0));
            uint birdRemaining = birdPlus.balanceOf(address(this));
            if (userAccrued <= birdRemaining) {
                birdPlus.transfer(user, userAccrued);
                return 0;
            }
        }
        return userAccrued;
    }

    /**
     * @notice Claim all the bird+ accrued by holder in all markets
     * @param holder The address to claim BRID+ for
     */
    function claimBirdPlus(address holder) public {
        return claimBirdPlus(holder, allMarkets);
    }

    /**
     * @notice Claim all the bird+ accrued by holder in the specified markets
     * @param holder The address to claim BRID+ for
     * @param bTokens The list of markets to claim BRID+ in
     */
    function claimBirdPlus(address holder, BToken[] memory bTokens) public {
        address[] memory holders = new address[](1);
        holders[0] = holder;
        claimBirdPlus(holders, bTokens, true, true);
    }

    /**
     * @notice Claim all bird+ accrued by the holders
     * @param holders The addresses to claim BRID+ for
     * @param bTokens The list of markets to claim BRID+ in
     * @param borrowers Whether or not to claim BRID+ earned by borrowing
     * @param suppliers Whether or not to claim BRID+ earned by supplying
     */
    function claimBirdPlus(address[] memory holders, BToken[] memory bTokens, bool borrowers, bool suppliers) public {
        for (uint i = 0; i < bTokens.length; i++) {
            BToken bToken = bTokens[i];
            require(markets[address(bToken)].isListed, "market must be listed");
            if (borrowers == true) {
                Exp memory borrowIndex = Exp({mantissa: bToken.borrowIndex()});
                updateBirdBorrowIndex(address(bToken), borrowIndex);
                for (uint j = 0; j < holders.length; j++) {
                    distributeBorrowerBirdPlus(address(bToken), holders[j], borrowIndex, true);
                }
            }
            if (suppliers == true) {
                updateBirdPlusSupplyIndex(address(bToken));
                for (uint j = 0; j < holders.length; j++) {
                    distributeSupplierBirdPlus(address(bToken), holders[j], true);
                }
            }
        }
    }

    /*** Bird+ Distribution Admin ***/

    function _setBirdPlusAddress(address birdAddress_) public {
        require(adminOrInitializing(), "only admin can set bird address");

        address oldAddress = birdAddress;
        birdAddress = birdAddress_;

        emit NewBirdPlusAddress(oldAddress, birdAddress_);
    }

    /**
     * @notice Set the amount of BRID+ distributed per block
     * @param birdRate_ The amount of BRID+ wei per block to distribute
     */
    function _setBirdPlusRate(uint birdRate_) public {
        require(adminOrInitializing(), "only admin can change bird rate");

        uint oldRate = birdRate;
        birdRate = birdRate_;
        emit NewBirdPlusRate(oldRate, birdRate_);

        refreshBirdPlusSpeedsInternal();
    }

    /**
     * @notice Add markets to birdMarkets, allowing them to earn BRID+ in the flywheel
     * @param bTokens The addresses of the markets to add
     */
    function _addBirdMarkets(address[] memory bTokens) public {
        require(adminOrInitializing(), "only admin can add bird market");

        for (uint i = 0; i < bTokens.length; i++) {
            _addBirdMarketInternal(bTokens[i]);
        }

        refreshBirdPlusSpeedsInternal();
    }

    function _addBirdMarketInternal(address bToken) internal {
        Market storage market = markets[bToken];
        require(market.isListed == true, "bird market is not listed");
        require(market.isBird == false, "bird market already added");

        market.isBird = true;
        emit MarketBird(BToken(bToken), true);

        if (birdSupplyState[bToken].index == 0 && birdSupplyState[bToken].block == 0) {
            birdSupplyState[bToken] = BirdMarketState({
                index: birdPlusInitialIndex,
                block: safe32(getBlockNumber(), "block number exceeds 32 bits")
            });
        }

        if (birdBorrowState[bToken].index == 0 && birdBorrowState[bToken].block == 0) {
            birdBorrowState[bToken] = BirdMarketState({
                index: birdPlusInitialIndex,
                block: safe32(getBlockNumber(), "block number exceeds 32 bits")
            });
        }
    }

    /**
     * @notice Remove a market from birdMarkets, preventing it from earning BRID+ in the flywheel
     * @param bToken The address of the market to drop
     */
    function _dropBirdMarket(address bToken) public {
        require(msg.sender == admin, "only admin can drop bird market");

        Market storage market = markets[bToken];
        require(market.isBird == true, "market is not a bird market");

        market.isBird = false;
        emit MarketBird(BToken(bToken), false);

        refreshBirdPlusSpeedsInternal();
    }

    /**
     * @notice Return all of the markets
     * @dev The automatic getter may be used to access an individual market.
     * @return The list of market addresses
     */
    function getAllMarkets() public view returns (BToken[] memory) {
        return allMarkets;
    }

    function getBlockNumber() public view returns (uint) {
        return block.number;
    }

    /**
     * @notice Return the address of the BRID+ token
     * @return The address of BRID+
     */
    function getBirdPlusAddress() public view returns (address) {
        return birdAddress;
    }
}