// Contract: LendingPoolAddressesProvider
// Target function: function setUserUseReserveAsCollateral(address _reserve, address _user, bool _useAsCollateral)
from);
        }

        emit BalanceTransfer(
            _from,
            _to,
            _value,
            fromBalanceIncrease,
            toBalanceIncrease,
            fromIndexReset ? 0 : fromIndex,
            toIndex
        );
    }

    /**
    * @dev executes the redirection of the interest from one address to another.
    * immediately after redirection, the destination address will start to accrue interest.
    * @param _from the address from which transfer the aTokens
    * @param _to the destination address
    **/
    function redirectInterestStreamInternal(
        address _from,
        address _to
    ) internal {

        address currentRedirectionAddress = interestRedirectionAddresses[_from];

        require(_to != currentRedirectionAddress, "Interest is already redirected to the user");

        //accumulates the accrued interest to the principal
        (uint256 previousPrincipalBalance,
        uint256 fromBalance,
        uint256 balanceIncrease,
        uint256 fromIndex) = cumulateBalanceInternal(_from);

        require(fromBalance > 0, "Interest stream can only be redirected if there is a valid balance");

        //if the user is already redirecting the interest to someone, before changing
        //the redirection address we substract the redirected balance of the previous
        //recipient
        if(currentRedirectionAddress != address(0)){
            updateRedirectedBalanceOfRedirectionAddressInternal(_from,0, previousPrincipalBalance);
        }

        //if the user is redirecting the interest back to himself,
        //we simply set to 0 the interest redirection address
        if(_to == _from) {
            interestRedirectionAddresses[_from] = address(0);
            emit InterestStreamRedirected(
                _from,
                address(0),
                fromBalance,
                balanceIncrease,
                fromIndex
            );
            return;
        }

        //first set the redirection address to the new recipient
        interestRedirectionAddresses[_from] = _to;

        //adds the user balance to the redirected balance of the destination
        updateRedirectedBalanceOfRedirectionAddressInternal(_from,fromBalance,0);

        emit InterestStreamRedirected(
            _from,
            _to,
            fromBalance,
            balanceIncrease,
            fromIndex
        );
    }

    /**
    * @dev function to reset the interest stream redirection and the user index, if the
    * user has no balance left.
    * @param _user the address of the user
    * @return true if the user index has also been reset, false otherwise. useful to emit the proper user index value
    **/
    function resetDataOnZeroBalanceInternal(address _user) internal returns(bool) {

        //if the user has 0 principal balance, the interest stream redirection gets reset
        interestRedirectionAddresses[_user] = address(0);

        //emits a InterestStreamRedirected event to notify that the redirection has been reset
        emit InterestStreamRedirected(_user, address(0),0,0,0);

        //if the redirected balance is also 0, we clear up the user index
        if(redirectedBalances[_user] == 0){
            userIndexes[_user] = 0;
            return true;
        }
        else{
            return false;
        }
    }
}

/**
* @title IFlashLoanReceiver interface
* @notice Interface for the Aave fee IFlashLoanReceiver.
* @author Aave
* @dev implement this interface to develop a flashloan-compatible flashLoanReceiver contract
**/
interface IFlashLoanReceiver {

    function executeOperation(address _reserve, uint256 _amount, uint256 _fee, bytes calldata _params) external;
}

/**
* @title ILendingRateOracle interface
* @notice Interface for the Aave borrow rate oracle. Provides the average market borrow rate to be used as a base for the stable borrow rate calculations
**/

interface ILendingRateOracle {
    /**
    @dev returns the market borrow rate in ray
    **/
    function getMarketBorrowRate(address _asset) external view returns (uint256);

    /**
    @dev sets the market borrow rate. Rate value must be in ray
    **/
    function setMarketBorrowRate(address _asset, uint256 _rate) external;
}

/**
@title IReserveInterestRateStrategyInterface interface
@notice Interface for the calculation of the interest rates.
*/

interface IReserveInterestRateStrategy {

    /**
    * @dev returns the base variable borrow rate, in rays
    */

    function getBaseVariableBorrowRate() external view returns (uint256);
    /**
    * @dev calculates the liquidity, stable, and variable rates depending on the current utilization rate
    *      and the base parameters
    *
    */
    function calculateInterestRates(
        address _reserve,
        uint256 _utilizationRate,
        uint256 _totalBorrowsStable,
        uint256 _totalBorrowsVariable,
        uint256 _averageStableBorrowRate)
    external
    view
    returns (uint256 liquidityRate, uint256 stableBorrowRate, uint256 variableBorrowRate);
}

library EthAddressLib {

    /**
    * @dev returns the address used within the protocol to identify ETH
    * @return the address assigned to ETH
     */
    function ethAddress() internal pure returns(address) {
        return 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
    }
}

/**
* @title LendingPoolCore contract
* @author Aave
* @notice Holds the state of the lending pool and all the funds deposited
* @dev NOTE: The core does not enforce security checks on the update of the state
* (eg, updateStateOnBorrow() does not enforce that borrowed is enabled on the reserve).
* The check that an action can be performed is a duty of the overlying LendingPool contract.
**/

contract LendingPoolCore is VersionedInitializable {
    using SafeMath for uint256;
    using WadRayMath for uint256;
    using CoreLibrary for CoreLibrary.ReserveData;
    using CoreLibrary for CoreLibrary.UserReserveData;
    using SafeERC20 for ERC20;
    using Address for address payable;

    /**
    * @dev Emitted when the state of a reserve is updated
    * @param reserve the address of the reserve
    * @param liquidityRate the new liquidity rate
    * @param stableBorrowRate the new stable borrow rate
    * @param variableBorrowRate the new variable borrow rate
    * @param liquidityIndex the new liquidity index
    * @param variableBorrowIndex the new variable borrow index
    **/
    event ReserveUpdated(
        address indexed reserve,
        uint256 liquidityRate,
        uint256 stableBorrowRate,
        uint256 variableBorrowRate,
        uint256 liquidityIndex,
        uint256 variableBorrowIndex
    );

    address public lendingPoolAddress;

    LendingPoolAddressesProvider public addressesProvider;

    /**
    * @dev only lending pools can use functions affected by this modifier
    **/
    modifier onlyLendingPool {
        require(lendingPoolAddress == msg.sender, "The caller must be a lending pool contract");
        _;
    }

    /**
    * @dev only lending pools configurator can use functions affected by this modifier
    **/
    modifier onlyLendingPoolConfigurator {
        require(
            addressesProvider.getLendingPoolConfigurator() == msg.sender,
            "The caller must be a lending pool configurator contract"
        );
        _;
    }

    mapping(address => CoreLibrary.ReserveData) internal reserves;
    mapping(address => mapping(address => CoreLibrary.UserReserveData)) internal usersReserveData;

    address[] public reservesList;

    uint256 public constant CORE_REVISION = 0x4;

    /**
    * @dev returns the revision number of the contract
    **/
    function getRevision() internal pure returns (uint256) {
        return CORE_REVISION;
    }

    /**
    * @dev initializes the Core contract, invoked upon registration on the AddressesProvider
    * @param _addressesProvider the addressesProvider contract
    **/

    function initialize(LendingPoolAddressesProvider _addressesProvider) public initializer {
        addressesProvider = _addressesProvider;
        refreshConfigInternal();
    }

    /**
    * @dev updates the state of the core as a result of a deposit action
    * @param _reserve the address of the reserve in which the deposit is happening
    * @param _user the address of the the user depositing
    * @param _amount the amount being deposited
    * @param _isFirstDeposit true if the user is depositing for the first time
    **/

    function updateStateOnDeposit(
        address _reserve,
        address _user,
        uint256 _amount,
        bool _isFirstDeposit
    ) external onlyLendingPool {
        reserves[_reserve].updateCumulativeIndexes();
        updateReserveInterestRatesAndTimestampInternal(_reserve, _amount, 0);

        if (_isFirstDeposit) {
            //if this is the first deposit of the user, we configure the deposit as enabled to be used as collateral
            setUserUseReserveAsCollateral(_reserve, _user, true);
        }
    }

    /**
    * @dev updates the state of the core as a result of a redeem action
    * @param _reserve the address of the reserve in which the redeem is happening
    * @param _user the address of the the user redeeming
    * @param _amountRedeemed the amount being redeemed
    * @param _userRedeemedEverything true if the user is redeeming everything
    **/
    function updateStateOnRedeem(
        address _reserve,
        address _user,
        uint256 _amountRedeemed,
        bool _userRedeemedEverything
    ) external onlyLendingPool {
        //compound liquidity and variable borrow interests
        reserves[_reserve].updateCumulativeIndexes();
        updateReserveInterestRatesAndTimestampInternal(_reserve, 0, _amountRedeemed);

        //if user redeemed everything the useReserveAsCollateral flag is reset
        if (_userRedeemedEverything) {
            setUserUseReserveAsCollateral(_reserve, _user, false);
        }
    }

    /**
    * @dev updates the state of the core as a result of a flashloan action
    * @param _reserve the address of the reserve in which the flashloan is happening
    * @param _income the income of the protocol as a result of the action
    **/
    function updateStateOnFlashLoan(
        address _reserve,
        uint256 _availableLiquidityBefore,
        uint256 _income,
        uint256 _protocolFee
    ) external onlyLendingPool {
        transferFlashLoanProtocolFeeInternal(_reserve, _protocolFee);

        //compounding the cumulated interest
        reserves[_reserve].updateCumulativeIndexes();

        uint256 totalLiquidityBefore = _availableLiquidityBefore.add(
            getReserveTotalBorrows(_reserve)
        );

        //compounding the received fee into the reserve
        reserves[_reserve].cumulateToLiquidityIndex(totalLiquidityBefore, _income);

        //refresh interest rates
        updateReserveInterestRatesAndTimestampInternal(_reserve, _income, 0);
    }

    /**
    * @dev updates the state of the core as a consequence of a borrow action.
    * @param _reserve the address of the reserve on which the user is borrowing
    * @param _user the address of the borrower
    * @param _amountBorrowed the new amount borrowed
    * @param _borrowFee the fee on the amount borrowed
    * @param _rateMode the borrow rate mode (stable, variable)
    * @return the new borrow rate for the user
    **/
    function updateStateOnBorrow(
        address _reserve,
        address _user,
        uint256 _amountBorrowed,
        uint256 _borrowFee,
        CoreLibrary.InterestRateMode _rateMode
    ) external onlyLendingPool returns (uint256, uint256) {
        // getting the previous borrow data of the user
        (uint256 principalBorrowBalance, , uint256 balanceIncrease) = getUserBorrowBalances(
            _reserve,
            _user
        );

        updateReserveStateOnBorrowInternal(
            _reserve,
            _user,
            principalBorrowBalance,
            balanceIncrease,
            _amountBorrowed,
            _rateMode
        );

        updateUserStateOnBorrowInternal(
            _reserve,
            _user,
            _amountBorrowed,
            balanceIncrease,
            _borrowFee,
            _rateMode
        );

        updateReserveInterestRatesAndTimestampInternal(_reserve, 0, _amountBorrowed);

        return (getUserCurrentBorrowRate(_reserve, _user), balanceIncrease);
    }

    /**
    * @dev updates the state of the core as a consequence of a repay action.
    * @param _reserve the address of the reserve on which the user is repaying
    * @param _user the address of the borrower
    * @param _paybackAmountMinusFees the amount being paid back minus fees
    * @param _originationFeeRepaid the fee on the amount that is being repaid
    * @param _balanceIncrease the accrued interest on the borrowed amount
    * @param _repaidWholeLoan true if the user is repaying the whole loan
    **/

    function updateStateOnRepay(
        address _reserve,
        address _user,
        uint256 _paybackAmountMinusFees,
        uint256 _originationFeeRepaid,
        uint256 _balanceIncrease,
        bool _repaidWholeLoan
    ) external onlyLendingPool {
        updateReserveStateOnRepayInternal(
            _reserve,
            _user,
            _paybackAmountMinusFees,
            _balanceIncrease
        );
        updateUserStateOnRepayInternal(
            _reserve,
            _user,
            _paybackAmountMinusFees,
            _originationFeeRepaid,
            _balanceIncrease,
            _repaidWholeLoan
        );

        updateReserveInterestRatesAndTimestampInternal(_reserve, _paybackAmountMinusFees, 0);
    }

    /**
    * @dev updates the state of the core as a consequence of a swap rate action.
    * @param _reserve the address of the reserve on which the user is repaying
    * @param _user the address of the borrower
    * @param _principalBorrowBalance the amount borrowed by the user
    * @param _compoundedBorrowBalance the amount borrowed plus accrued interest
    * @param _balanceIncrease the accrued interest on the borrowed amount
    * @param _currentRateMode the current interest rate mode for the user
    **/
    function updateStateOnSwapRate(
        address _reserve,
        address _user,
        uint256 _principalBorrowBalance,
        uint256 _compoundedBorrowBalance,
        uint256 _balanceIncrease,
        CoreLibrary.InterestRateMode _currentRateMode
    ) external onlyLendingPool returns (CoreLibrary.InterestRateMode, uint256) {
        updateReserveStateOnSwapRateInternal(
            _reserve,
            _user,
            _principalBorrowBalance,
            _compoundedBorrowBalance,
            _currentRateMode
        );

        CoreLibrary.InterestRateMode newRateMode = updateUserStateOnSwapRateInternal(
            _reserve,
            _user,
            _balanceIncrease,
            _currentRateMode
        );

        updateReserveInterestRatesAndTimestampInternal(_reserve, 0, 0);

        return (newRateMode, getUserCurrentBorrowRate(_reserve, _user));
    }

    /**
    * @dev updates the state of the core as a consequence of a liquidation action.
    * @param _principalReserve the address of the principal reserve that is being repaid
    * @param _collateralReserve the address of the collateral reserve that is being liquidated
    * @param _user the address of the borrower
    * @param _amountToLiquidate the amount being repaid by the liquidator
    * @param _collateralToLiquidate the amount of collateral being liquidated
    * @param _feeLiquidated the amount of origination fee being liquidated
    * @param _liquidatedCollateralForFee the amount of collateral equivalent to the origination fee + bonus
    * @param _balanceIncrease the accrued interest on the borrowed amount
    * @param _liquidatorReceivesAToken true if the liquidator will receive aTokens, false otherwise
    **/
    function updateStateOnLiquidation(
        address _principalReserve,
        address _collateralReserve,
        address _user,
        uint256 _amountToLiquidate,
        uint256 _collateralToLiquidate,
        uint256 _feeLiquidated,
        uint256 _liquidatedCollateralForFee,
        uint256 _balanceIncrease,
        bool _liquidatorReceivesAToken
    ) external onlyLendingPool {
        updatePrincipalReserveStateOnLiquidationInternal(
            _principalReserve,
            _user,
            _amountToLiquidate,
            _balanceIncrease
        );

        updateCollateralReserveStateOnLiquidationInternal(
            _collateralReserve
        );

        updateUserStateOnLiquidationInternal(
            _principalReserve,
            _user,
            _amountToLiquidate,
            _feeLiquidated,
            _balanceIncrease
        );

        updateReserveInterestRatesAndTimestampInternal(_principalReserve, _amountToLiquidate, 0);

        if (!_liquidatorReceivesAToken) {
            updateReserveInterestRatesAndTimestampInternal(
                _collateralReserve,
                0,
                _collateralToLiquidate.add(_liquidatedCollateralForFee)
            );
        }

    }

    /**
    * @dev updates the state of the core as a consequence of a stable rate rebalance
    * @param _reserve the address of the principal reserve where the user borrowed
    * @param _user the address of the borrower
    * @param _balanceIncrease the accrued interest on the borrowed amount
    * @return the new stable rate for the user
    **/
    function updateStateOnRebalance(address _reserve, address _user, uint256 _balanceIncrease)
        external
        onlyLendingPool
        returns (uint256)
    {
        updateReserveStateOnRebalanceInternal(_reserve, _user, _balanceIncrease);

        //update user data and rebalance the rate
        updateUserStateOnRebalanceInternal(_reserve, _user, _balanceIncrease);
        updateReserveInterestRatesAndTimestampInternal(_reserve, 0, 0);
        return usersReserveData[_user][_reserve].stableBorrowRate;
    }