CToken.sol

// SPDX-License-Identifier: BSD-3-Clause
pragma solidity 0.8.20;

import "./ComptrollerInterface.sol";
import "./CTokenInterfaces.sol";
import "./ErrorReporter.sol";
import "./EIP20Interface.sol";
import "./InterestRateModel.sol";
import "./ExponentialNoError.sol";
import "forge-std/console2.sol";
/**
 * @title Compound's CToken Contract
 * @notice Abstract base for CTokens
 * @author Compound
 */
abstract contract CToken is
    CTokenInterface,
    ExponentialNoError,
    TokenErrorReporter
{
    /**
     * @notice Initialize the money market
     * @param comptroller_ The address of the Comptroller
     * @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(
        ComptrollerInterface comptroller_,
        InterestRateModel interestRateModel_,
        uint initialExchangeRateMantissa_,
        string memory name_,
        string memory symbol_,
        uint8 decimals_,
        uint fullUtilizationRate_
    ) 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 comptroller
        uint err = _setComptroller(comptroller_);
        require(err == NO_ERROR, "setting comptroller failed");

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

        fullUtilizationRate = fullUtilizationRate_;
        // Set the interest rate model (depends on block number / borrow index)
        err = _setInterestRateModelFresh(interestRateModel_);
        require(err == 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 0 if the transfer succeeded, else revert
     */
    function transferTokens(
        address spender,
        address src,
        address dst,
        uint tokens
    ) internal returns (uint) {
        /* Fail if transfer not allowed */
        uint allowed = comptroller.transferAllowed(
            address(this),
            src,
            dst,
            tokens
        );
        if (allowed != 0) {
            revert TransferComptrollerRejection(allowed);
        }

        /* Do not allow self-transfers */
        if (src == dst) {
            revert TransferNotAllowed();
        }

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

        /* Do the calculations, checking for {under,over}flow */                 
        uint allowanceNew = startingAllowance - tokens;
        uint srcTokensNew = accountTokens[src] - tokens;
        uint dstTokensNew = accountTokens[dst] + tokens;

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

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

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

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

        // unused function
        // comptroller.transferVerify(address(this), src, dst, tokens);

        return 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 override nonReentrant returns (bool) {
        return transferTokens(msg.sender, msg.sender, dst, amount) == 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 override nonReentrant returns (bool) {
        return transferTokens(msg.sender, src, dst, amount) == 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 (uint256.max means infinite)
     * @return Whether or not the approval succeeded
     */
    function approve(
        address spender,
        uint256 amount
    ) external override 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 override 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 override 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 override returns (uint) {
        Exp memory exchangeRate = Exp({mantissa: exchangeRateCurrent()});
        return mul_ScalarTruncate(exchangeRate, accountTokens[owner]);
    }

    /**
     * @notice Get a snapshot of the account's balances, and the cached exchange rate
     * @dev This is used by comptroller 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 override returns (uint, uint, uint, uint) {
        return (
            NO_ERROR,
            accountTokens[account],
            borrowBalanceStoredInternal(account),
            exchangeRateStoredInternal()
        );
    }

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

    /**
     * @notice Returns the current per-block borrow interest rate for this cToken
     * @return The borrow interest rate per block, scaled by 1e18
     */
    function borrowRatePerBlock()
        external
        view
        virtual
        override
        returns (uint)
    {
        uint currentTimestamp = block.timestamp;
        uint timestampPrior = accrualBlockTimestamp;
        uint deltaTime = currentTimestamp - timestampPrior;
        (uint borrowRateMantissa, ) = interestRateModel.getBorrowRate(
            getCashPrior(),
            totalBorrows,
            totalReserves,
            deltaTime,
            fullUtilizationRate
        );
        return borrowRateMantissa;
    }

    /**
     * @notice Returns the current per-block supply interest rate for this cToken
     * @return The supply interest rate per block, scaled by 1e18
     */
    function supplyRatePerBlock()
        external
        view
        virtual
        override
        returns (uint)
    {
        uint currentTimestamp = block.timestamp;
        uint timestampPrior = accrualBlockTimestamp;
        uint deltaTime = currentTimestamp - timestampPrior;
        return
            interestRateModel.getSupplyRate(
                getCashPrior(),
                totalBorrows,
                totalReserves,
                reserveFactorMantissa,
                deltaTime,
                fullUtilizationRate
            );
    }

    /**
     * @notice Returns the current total borrows plus accrued interest
     * @return The total borrows with interest
     */
    function totalBorrowsCurrent()
        external
        override
        nonReentrant
        returns (uint)
    {
        accrueInterest();
        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 override nonReentrant returns (uint) {
        accrueInterest();
        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 override returns (uint) {
        return borrowBalanceStoredInternal(account);
    }

    /**
     * @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 (uint) {
        /* 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 0;
        }

        /* Calculate new borrow balance using the interest index:
         *  recentBorrowBalance = borrower.borrowBalance * market.borrowIndex / borrower.borrowIndex
         */
        uint principalTimesIndex = borrowSnapshot.principal * borrowIndex;
        return principalTimesIndex / borrowSnapshot.interestIndex;
    }

    /**
     * @notice Accrue interest then return the up-to-date exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateCurrent() public override nonReentrant returns (uint) {
        accrueInterest();
        return exchangeRateStored();
    }

    /**
     * @notice Calculates the exchange rate from the underlying to the CToken
     * @dev This function does not accrue interest before calculating the exchange rate
     * @return Calculated exchange rate scaled by 1e18
     */
    function exchangeRateStored() public view override returns (uint) {
        return exchangeRateStoredInternal();
    }

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

            return exchangeRate;
        }
    }

    /**
     * @notice Get cash balance of this cToken in the underlying asset
     * @return The quantity of underlying asset owned by this contract
     */
    function getCash() external view override 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 virtual override returns (uint) {
        /* Remember the initial block number */
        uint currentBlockNumber = getBlockNumber();
        uint accrualBlockNumberPrior = accrualBlockNumber;
        /* Short-circuit accumulating 0 interest */
        if (accrualBlockNumberPrior == currentBlockNumber) {
            return 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,
            uint newfullUtilizationRate
        ) = interestRateModel.getBorrowRate(
                cashPrior,
                borrowsPrior,
                reservesPrior,
                block.timestamp - accrualBlockTimestamp,
                fullUtilizationRate
            );
        require(
            borrowRateMantissa <= borrowRateMaxMantissa,
            "borrow rate is absurdly high"
        );

        /* Calculate the number of blocks elapsed since the last accrual */
        uint blockDelta = currentBlockNumber - accrualBlockNumberPrior;

        /*
         * 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 = mul_(
            Exp({mantissa: borrowRateMantissa}),
            blockDelta
        );
        uint interestAccumulated = mul_ScalarTruncate(
            simpleInterestFactor,
            borrowsPrior
        );
        uint totalBorrowsNew = interestAccumulated + borrowsPrior;
        uint totalReservesNew = mul_ScalarTruncateAddUInt(
            Exp({mantissa: reserveFactorMantissa}),
            interestAccumulated,
            reservesPrior
        );
        uint borrowIndexNew = mul_ScalarTruncateAddUInt(
            simpleInterestFactor,
            borrowIndexPrior,
            borrowIndexPrior
        );

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

        /* We write the previously calculated values into storage */
        accrualBlockNumber = currentBlockNumber;
        accrualBlockTimestamp = block.timestamp;
        borrowIndex = borrowIndexNew;
        totalBorrows = totalBorrowsNew;
        totalReserves = totalReservesNew;
        if (fullUtilizationRate != newfullUtilizationRate) {
            emit UpdateRate(fullUtilizationRate, newfullUtilizationRate);
            fullUtilizationRate = newfullUtilizationRate;
        }

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

        return NO_ERROR;
    }

    /**
     * @notice Sender supplies assets into the market and receives cTokens in exchange
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param mintAmount The amount of the underlying asset to supply
     */
    function mintInternal(uint mintAmount) internal nonReentrant {
        accrueInterest();
        // mintFresh emits the actual Mint event if successful and logs on errors, so we don't need to
        mintFresh(msg.sender, mintAmount);
    }

    /**
     * @notice User supplies assets into the market and receives cTokens 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
     */
    function mintFresh(address minter, uint mintAmount) internal {
        /* Fail if mint not allowed */
        uint allowed = comptroller.mintAllowed(
            address(this),
            minter,
            mintAmount
        );
        if (allowed != 0) {
            revert MintComptrollerRejection(allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            revert MintFreshnessCheck();
        }

        Exp memory exchangeRate = Exp({mantissa: exchangeRateStoredInternal()});

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

        /*
         *  We call `doTransferIn` for the minter and the mintAmount.
         *  Note: The cToken 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 cToken holds an additional `actualMintAmount`
         *  of cash.
         */
        uint actualMintAmount = doTransferIn(minter, mintAmount);

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

        uint mintTokens = div_(actualMintAmount, exchangeRate);

        /*
         * We calculate the new total supply of cTokens and minter token balance, checking for overflow:
         *  totalSupplyNew = totalSupply + mintTokens
         *  accountTokensNew = accountTokens[minter] + mintTokens
         * And write them into storage
         */
        totalSupply = totalSupply + mintTokens;
        accountTokens[minter] = accountTokens[minter] + mintTokens;

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

        /* We call the defense hook */
        // unused function
        // comptroller.mintVerify(address(this), minter, actualMintAmount, mintTokens);
    }

    /**
     * @notice Sender redeems cTokens in exchange for the underlying asset
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param redeemTokens The number of cTokens to redeem into underlying
     */
    function redeemInternal(uint redeemTokens) internal nonReentrant {
        accrueInterest();
        // redeemFresh emits redeem-specific logs on errors, so we don't need to
        redeemFresh(payable(msg.sender), redeemTokens, 0);
    }

    /**
     * @notice Sender redeems cTokens 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 cTokens
     */
    function redeemUnderlyingInternal(uint redeemAmount) internal nonReentrant {
        accrueInterest();
        // redeemFresh emits redeem-specific logs on errors, so we don't need to
        redeemFresh(payable(msg.sender), 0, redeemAmount);
    }

    /**
     * @notice User redeems cTokens 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 cTokens 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 cTokens (only one of redeemTokensIn or redeemAmountIn may be non-zero)
     */
    function redeemFresh(
        address payable redeemer,
        uint redeemTokensIn,
        uint redeemAmountIn
    ) internal virtual {
        require(
            redeemTokensIn == 0 || redeemAmountIn == 0,
            "one of redeemTokensIn or redeemAmountIn must be zero"
        );

        /* exchangeRate = invoke Exchange Rate Stored() */
        Exp memory exchangeRate = Exp({mantissa: exchangeRateStoredInternal()});

        uint redeemTokens;
        uint redeemAmount;

        /* 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
             */
            redeemTokens = redeemTokensIn;
            redeemAmount = mul_ScalarTruncate(exchangeRate, redeemTokensIn);
        } else {
            /*
             * We get the current exchange rate and calculate the amount to be redeemed:
             *  redeemTokens = redeemAmountIn / exchangeRate
             *  redeemAmount = redeemAmountIn
             */
            redeemTokens = div_(redeemAmountIn, exchangeRate);
            redeemAmount = redeemAmountIn;
        }

        /* Fail if redeem not allowed */
        uint allowed = comptroller.redeemAllowed(
            address(this),
            redeemer,
            redeemTokens
        );
        console2.log("redeem?",allowed);
        if (allowed != 0) {
            revert RedeemComptrollerRejection(allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            revert RedeemFreshnessCheck();
        }

        /* Fail gracefully if protocol has insufficient cash */
        if (getCashPrior() < redeemAmount) {
            revert RedeemTransferOutNotPossible();
        }

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

        /*
         * We write the previously calculated values into storage.
         *  Note: Avoid token reentrancy attacks by writing reduced supply before external transfer.
         */
        totalSupply = totalSupply - redeemTokens;
        accountTokens[redeemer] = accountTokens[redeemer] - redeemTokens;

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

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

    /**
     * @notice Sender borrows assets from the protocol to their own address
     * @param borrowAmount The amount of the underlying asset to borrow
     */
    function borrowInternal(uint borrowAmount) internal nonReentrant {
        accrueInterest();
        // borrowFresh emits borrow-specific logs on errors, so we don't need to
        borrowFresh(payable(msg.sender), borrowAmount);
    }

    /**
     * @notice Users borrow assets from the protocol to their own address
     * @param borrowAmount The amount of the underlying asset to borrow
     */
    function borrowFresh(
        address payable borrower,
        uint borrowAmount
    ) internal virtual {
        borrowFreshNoTransfer(borrower, borrowAmount);

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

    // function borrowFreshOnBehalf(address payable borrower,address payable receiver, uint borrowAmount) virtual internal
    // {
    //     borrowFreshNoTransfer(borrower, borrowAmount);

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

    /**
     * @notice Users borrow assets from the protocol to their own address
     * @param borrowAmount The amount of the underlying asset to borrow
     */
    function borrowFreshNoTransfer(
        address payable borrower,
        uint borrowAmount
    ) internal virtual {
        /* Fail if borrow not allowed */
        uint allowed = comptroller.borrowAllowed(
            address(this),
            borrower,
            borrowAmount
        );
        if (allowed != 0) {
            revert BorrowComptrollerRejection(allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            revert BorrowFreshnessCheck();
        }

        /* Fail gracefully if protocol has insufficient underlying cash */
        if (getCashPrior() < borrowAmount) {
            revert BorrowCashNotAvailable();
        }

        /*
         * We calculate the new borrower and total borrow balances, failing on overflow:
         *  accountBorrowNew = accountBorrow + borrowAmount
         *  totalBorrowsNew = totalBorrows + borrowAmount
         */
        uint accountBorrowsPrev = borrowBalanceStoredInternal(borrower);
        uint accountBorrowsNew = accountBorrowsPrev + borrowAmount;
        uint totalBorrowsNew = totalBorrows + borrowAmount;

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

        /*
         * We write the previously calculated values into storage.
         *  Note: Avoid token reentrancy attacks by writing increased borrow before external transfer.
        `*/
        accountBorrows[borrower].principal = accountBorrowsNew;
        accountBorrows[borrower].interestIndex = borrowIndex;
        totalBorrows = totalBorrowsNew;

        /* We emit a Borrow event */
        emit Borrow(borrower, borrowAmount, accountBorrowsNew, totalBorrowsNew);
    }

    /**
     * @notice Sender repays their own borrow
     * @param repayAmount The amount to repay, or -1 for the full outstanding amount
     */
    function repayBorrowInternal(uint repayAmount) internal nonReentrant {
        accrueInterest();
        // repayBorrowFresh emits repay-borrow-specific logs on errors, so we don't need to
        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, or -1 for the full outstanding amount
     */
    function repayBorrowBehalfInternal(
        address borrower,
        uint repayAmount
    ) internal nonReentrant {
        accrueInterest();
        // repayBorrowFresh emits repay-borrow-specific logs on errors, so we don't need to
        repayBorrowFresh(msg.sender, borrower, repayAmount);
    }

    /**
     * @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 underlying tokens being returned, or -1 for the full outstanding amount
     * @return (uint) the actual repayment amount.
     */
    function repayBorrowFresh(
        address payer,
        address borrower,
        uint repayAmount
    ) internal virtual returns (uint) {
        /* Fail if repayBorrow not allowed */
        uint allowed = comptroller.repayBorrowAllowed(
            address(this),
            payer,
            borrower,
            repayAmount
        );
        if (allowed != 0) {
            revert RepayBorrowComptrollerRejection(allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            revert RepayBorrowFreshnessCheck();
        }

        /* We fetch the amount the borrower owes, with accumulated interest */
        uint accountBorrowsPrev = borrowBalanceStoredInternal(borrower);

        /* If repayAmount == -1, repayAmount = accountBorrows */
        uint repayAmountFinal = repayAmount == type(uint).max
            ? accountBorrowsPrev
            : repayAmount;

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

        /*
         * We call doTransferIn for the payer and the repayAmount
         *  Note: The cToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the cToken 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.
         */
        // Numa modif, we can use this function to repay leverage and payer is CToken (amount comes from flashloan)
        // so we need to handle that case
        uint actualRepayAmount = repayAmount;
        if (payer != address(this)) {
            // transfer needed
            actualRepayAmount = doTransferIn(payer, repayAmountFinal);
        }

        /*
         * We calculate the new borrower and total borrow balances, failing on underflow:
         *  accountBorrowsNew = accountBorrows - actualRepayAmount
         *  totalBorrowsNew = totalBorrows - actualRepayAmount
         */
        uint accountBorrowsNew = accountBorrowsPrev - actualRepayAmount;
        uint totalBorrowsNew = totalBorrows - actualRepayAmount;

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

        /* We emit a RepayBorrow event */
        emit RepayBorrow(
            payer,
            borrower,
            actualRepayAmount,
            accountBorrowsNew,
            totalBorrowsNew
        );

        return actualRepayAmount;
    }

    /**
     * @notice The sender liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @param borrower The borrower of this cToken to be liquidated
     * @param cTokenCollateral The market in which to seize collateral from the borrower
     * @param repayAmount The amount of the underlying borrowed asset to repay
     */
    function liquidateBorrowInternal(
        address borrower,
        uint repayAmount,
        CTokenInterface cTokenCollateral
    ) internal nonReentrant {
        accrueInterest();

        uint error = cTokenCollateral.accrueInterest();
        if (error != NO_ERROR) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted liquidation failed
            revert LiquidateAccrueCollateralInterestFailed(error);
        }

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

    function liquidateBadDebtInternal(
        address borrower,
        uint repayAmount,
        uint percentageToTake,
        CTokenInterface cTokenCollateral
    ) internal nonReentrant {
        accrueInterest();

        uint error = cTokenCollateral.accrueInterest();
        if (error != NO_ERROR) {
            // accrueInterest emits logs on errors, but we still want to log the fact that an attempted liquidation failed
            revert LiquidateAccrueCollateralInterestFailed(error);
        }

        liquidateBadDebtFresh(
            msg.sender,
            borrower,
            repayAmount,
            percentageToTake,
            cTokenCollateral
        );
    }

    /**
     * @notice The liquidator liquidates the borrowers collateral.
     *  The collateral seized is transferred to the liquidator.
     * @param borrower The borrower of this cToken to be liquidated
     * @param liquidator The address repaying the borrow and seizing collateral
     * @param cTokenCollateral The market in which to seize collateral from the borrower
     * @param repayAmount The amount of the underlying borrowed asset to repay
     */
    function liquidateBorrowFresh(
        address liquidator,
        address borrower,
        uint repayAmount,
        CTokenInterface cTokenCollateral
    ) internal {
        /* Fail if liquidate not allowed */
        uint allowed = comptroller.liquidateBorrowAllowed(
            address(this),
            address(cTokenCollateral),
            liquidator,
            borrower,
            repayAmount
        );
        if (allowed != 0) {
            revert LiquidateComptrollerRejection(allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            revert LiquidateFreshnessCheck();
        }

        /* Verify cTokenCollateral market's block number equals current block number */
        if (cTokenCollateral.accrualBlockNumber() != getBlockNumber()) {
            revert LiquidateCollateralFreshnessCheck();
        }

        /* Fail if borrower = liquidator */
        if (borrower == liquidator) {
            revert LiquidateLiquidatorIsBorrower();
        }

        /* Fail if repayAmount = 0 */
        if (repayAmount == 0) {
            revert LiquidateCloseAmountIsZero();
        }

        /* Fail if repayAmount = -1 */
        if (repayAmount == type(uint).max) {
            revert LiquidateCloseAmountIsUintMax();
        }

        /* Fail if repayBorrow fails */
        uint actualRepayAmount = repayBorrowFresh(
            liquidator,
            borrower,
            repayAmount
        );

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

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

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

        // If this is also the collateral, run seizeInternal to avoid re-entrancy, otherwise make an external call
        if (address(cTokenCollateral) == address(this)) {
            seizeInternal(address(this), liquidator, borrower, seizeTokens);
        } else {
            require(
                cTokenCollateral.seize(liquidator, borrower, seizeTokens) ==
                    NO_ERROR,
                "token seizure failed"
            );
        }

        /* We emit a LiquidateBorrow event */
        emit LiquidateBorrow(
            liquidator,
            borrower,
            actualRepayAmount,
            address(cTokenCollateral),
            seizeTokens
        );
    }

    function liquidateBadDebtFresh(
        address liquidator,
        address borrower,
        uint repayAmount,
        uint percentageToTake,
        CTokenInterface cTokenCollateral
    ) internal {
        /* Fail if liquidate not allowed */
        uint allowed = comptroller.liquidateBadDebtAllowed(
            address(this),
            address(cTokenCollateral),
            liquidator,
            borrower,
            repayAmount
        );
        if (allowed != 0) {
            revert LiquidateComptrollerRejection(allowed);
        }

        /* Verify market's block number equals current block number */
        if (accrualBlockNumber != getBlockNumber()) {
            revert LiquidateFreshnessCheck();
        }

        /* Verify cTokenCollateral market's block number equals current block number */
        if (cTokenCollateral.accrualBlockNumber() != getBlockNumber()) {
            revert LiquidateCollateralFreshnessCheck();
        }

        /* Fail if borrower = liquidator */
        if (borrower == liquidator) {
            revert LiquidateLiquidatorIsBorrower();
        }

        /* Fail if repayAmount = 0 */
        if (repayAmount == 0) {
            revert LiquidateCloseAmountIsZero();
        }

        // /* Fail if repayAmount = -1 */
        // if (repayAmount == type(uint).max) {
        //     revert LiquidateCloseAmountIsUintMax();
        // }

        // This is moved after evaluating seize tokens as we need to use borrow balance
        /* Fail if repayBorrow fails */

        uint actualRepayAmount;
        if (repayAmount > 0)
            actualRepayAmount = repayBorrowFresh(
                liquidator,
                borrower,
                repayAmount
            );

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

        /* We calculate the number of collateral tokens that will be seized */
        (uint amountSeizeError, uint seizeTokens) = comptroller
            .liquidateBadDebtCalculateSeizeTokensAfterRepay(
                address(cTokenCollateral),
                borrower,
                percentageToTake
            );
        require(
            amountSeizeError == NO_ERROR,
            "LIQUIDATE_COMPTROLLER_CALCULATE_AMOUNT_SEIZE_FAILED"
        );

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

        //If this is also the collateral, run seizeInternal to avoid re-entrancy, otherwise make an external call
        if (address(cTokenCollateral) == address(this)) {
            seizeBadDebtInternal(
                address(this),
                liquidator,
                borrower,
                seizeTokens
            );
        } else {
            require(
                cTokenCollateral.seizeBadDebt(
                    liquidator,
                    borrower,
                    seizeTokens
                ) == NO_ERROR,
                "token seizure failed"
            );
        }

        /* We emit a LiquidateBorrow event */
        emit LiquidateBadDebt(
            liquidator,
            borrower,
            actualRepayAmount,
            address(cTokenCollateral),
            seizeTokens
        );
    }

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

        return NO_ERROR;
    }

    function seizeBadDebt(
        address liquidator,
        address borrower,
        uint seizeTokens
    ) external override nonReentrant returns (uint) {
        seizeBadDebtInternal(msg.sender, liquidator, borrower, seizeTokens);

        return NO_ERROR;
    }

    /**
     * @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 CToken.
     *  Its absolutely critical to use msg.sender as the seizer cToken and not a parameter.
     * @param seizerToken The contract seizing the collateral (i.e. borrowed cToken)
     * @param liquidator The account receiving seized collateral
     * @param borrower The account having collateral seized
     * @param seizeTokens The number of cTokens to seize
     */
    function seizeInternal(
        address seizerToken,
        address liquidator,
        address borrower,
        uint seizeTokens
    ) internal {
        /* Fail if seize not allowed */
        uint allowed = comptroller.seizeAllowed(
            address(this),
            seizerToken,
            liquidator,
            borrower,
            seizeTokens
        );
        if (allowed != 0) {
            revert LiquidateSeizeComptrollerRejection(allowed);
        }

        /* Fail if borrower = liquidator */
        if (borrower == liquidator) {
            revert LiquidateSeizeLiquidatorIsBorrower();
        }

        /*
         * We calculate the new borrower and liquidator token balances, failing on underflow/overflow:
         *  borrowerTokensNew = accountTokens[borrower] - seizeTokens
         *  liquidatorTokensNew = accountTokens[liquidator] + seizeTokens
         */
        uint protocolSeizeTokens = mul_(
            seizeTokens,
            Exp({mantissa: protocolSeizeShareMantissa})
        );
        uint liquidatorSeizeTokens = seizeTokens - protocolSeizeTokens;
        Exp memory exchangeRate = Exp({mantissa: exchangeRateStoredInternal()});
        uint protocolSeizeAmount = mul_ScalarTruncate(
            exchangeRate,
            protocolSeizeTokens
        );
        uint totalReservesNew = totalReserves + protocolSeizeAmount;

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

        /* We write the calculated values into storage */

        totalReserves = totalReservesNew;
        totalSupply = totalSupply - protocolSeizeTokens;
        accountTokens[borrower] = accountTokens[borrower] - seizeTokens;
        accountTokens[liquidator] =
            accountTokens[liquidator] +
            liquidatorSeizeTokens;

        /* Emit a Transfer event */
        emit Transfer(borrower, liquidator, liquidatorSeizeTokens);
        emit Transfer(borrower, address(this), protocolSeizeTokens);
        emit ReservesAdded(
            address(this),
            protocolSeizeAmount,
            totalReservesNew
        );
    }

    function seizeBadDebtInternal(
        address seizerToken,
        address liquidator,
        address borrower,
        uint seizeTokens
    ) internal {
        /* Fail if seize not allowed */
        uint allowed = comptroller.seizeAllowed(
            address(this),
            seizerToken,
            liquidator,
            borrower,
            seizeTokens
        );
        if (allowed != 0) {
            revert LiquidateSeizeComptrollerRejection(allowed);
        }

        /* Fail if borrower = liquidator */
        if (borrower == liquidator) {
            revert LiquidateSeizeLiquidatorIsBorrower();
        }

        /*
         * We calculate the new borrower and liquidator token balances, failing on underflow/overflow:
         *  borrowerTokensNew = accountTokens[borrower] - seizeTokens
         *  liquidatorTokensNew = accountTokens[liquidator] + seizeTokens
         */
        // everything goes to liquidator
        uint liquidatorSeizeTokens = seizeTokens;

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

        /* We write the calculated values into storage */
        accountTokens[borrower] = accountTokens[borrower] - seizeTokens;
        accountTokens[liquidator] =
            accountTokens[liquidator] +
            liquidatorSeizeTokens;

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

    /*** 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 override returns (uint) {
        // Check caller = admin
        if (msg.sender != admin) {
            revert SetPendingAdminOwnerCheck();
        }

        // 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 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 override returns (uint) {
        // Check caller is pendingAdmin and pendingAdmin ≠ address(0)
        if (msg.sender != pendingAdmin || msg.sender == address(0)) {
            revert AcceptAdminPendingAdminCheck();
        }

        // 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 = payable(address(0));

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

        return NO_ERROR;
    }

    /**
     * @notice Sets a new comptroller for the market
     * @dev Admin function to set a new comptroller
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function _setComptroller(
        ComptrollerInterface newComptroller
    ) public override returns (uint) {
        // Check caller is admin
        if (msg.sender != admin) {
            revert SetComptrollerOwnerCheck();
        }

        ComptrollerInterface oldComptroller = comptroller;
        // Ensure invoke comptroller.isComptroller() returns true
        require(newComptroller.isComptroller(), "marker method returned false");

        // Set market's comptroller to newComptroller
        comptroller = newComptroller;

        // Emit NewComptroller(oldComptroller, newComptroller)
        emit NewComptroller(oldComptroller, newComptroller);

        return 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 override nonReentrant returns (uint) {
        accrueInterest();
        // _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) {
            revert SetReserveFactorAdminCheck();
        }

        // Verify market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            revert SetReserveFactorFreshCheck();
        }

        // Check newReserveFactor ≤ maxReserveFactor
        if (newReserveFactorMantissa > reserveFactorMaxMantissa) {
            revert SetReserveFactorBoundsCheck();
        }

        uint oldReserveFactorMantissa = reserveFactorMantissa;
        reserveFactorMantissa = newReserveFactorMantissa;

        emit NewReserveFactor(
            oldReserveFactorMantissa,
            newReserveFactorMantissa
        );

        return 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) {
        accrueInterest();

        // _addReservesFresh emits reserve-addition-specific logs on errors, so we don't need to.
        _addReservesFresh(addAmount);
        return NO_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()) {
            revert AddReservesFactorFreshCheck(actualAddAmount);
        }

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

        /*
         * We call doTransferIn for the caller and the addAmount
         *  Note: The cToken must handle variations between ERC-20 and ETH underlying.
         *  On success, the cToken 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;

        // 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 (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 override nonReentrant returns (uint) {
        accrueInterest();
        // _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) {
            revert ReduceReservesAdminCheck();
        }

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            revert ReduceReservesFreshCheck();
        }

        // Fail gracefully if protocol has insufficient underlying cash
        if (getCashPrior() < reduceAmount) {
            revert ReduceReservesCashNotAvailable();
        }

        // Check reduceAmount ≤ reserves[n] (totalReserves)
        if (reduceAmount > totalReserves) {
            revert ReduceReservesCashValidation();
        }

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

        totalReservesNew = totalReserves - reduceAmount;

        // 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 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 override returns (uint) {
        accrueInterest();
        // _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) {
            revert SetInterestRateModelOwnerCheck();
        }

        // We fail gracefully unless market's block number equals current block number
        if (accrualBlockNumber != getBlockNumber()) {
            revert SetInterestRateModelFreshCheck();
        }

        // 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 NewMarketInterestRateModel(oldInterestRateModel, newInterestRateModel)
        emit NewMarketInterestRateModel(
            oldInterestRateModel,
            newInterestRateModel
        );

        return 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 virtual 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 virtual returns (uint);

    /**
     * @dev Performs a transfer out, ideally returning an explanatory error code upon failure rather 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 virtual;

    /*** 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
    }
}