// Contract: LendingPoolAddressesProvider
// Target function: function updateStateOnBorrow(
 stored balance, which does not consider the perpetually accruing interest.
    * @param _user the address of the user
    * @return the principal balance of the user
    **/
    function principalBalanceOf(address _user) external view returns(uint256) {
        return super.balanceOf(_user);
    }


    /**
    * @dev calculates the total supply of the specific aToken
    * since the balance of every single user increases over time, the total supply
    * does that too.
    * @return the current total supply
    **/
    function totalSupply() public view returns(uint256) {

        uint256 currentSupplyPrincipal = super.totalSupply();

        if(currentSupplyPrincipal == 0){
            return 0;
        }

        return currentSupplyPrincipal
            .wadToRay()
            .rayMul(core.getReserveNormalizedIncome(underlyingAssetAddress))
            .rayToWad();
    }


    /**
     * @dev Used to validate transfers before actually executing them.
     * @param _user address of the user to check
     * @param _amount the amount to check
     * @return true if the _user can transfer _amount, false otherwise
     **/
    function isTransferAllowed(address _user, uint256 _amount) public view returns (bool) {
        return dataProvider.balanceDecreaseAllowed(underlyingAssetAddress, _user, _amount);
    }

    /**
    * @dev returns the last index of the user, used to calculate the balance of the user
    * @param _user address of the user
    * @return the last user index
    **/
    function getUserIndex(address _user) external view returns(uint256) {
        return userIndexes[_user];
    }


    /**
    * @dev returns the address to which the interest is redirected
    * @param _user address of the user
    * @return 0 if there is no redirection, an address otherwise
    **/
    function getInterestRedirectionAddress(address _user) external view returns(address) {
        return interestRedirectionAddresses[_user];
    }

    /**
    * @dev returns the redirected balance of the user. The redirected balance is the balance
    * redirected by other accounts to the user, that is accrueing interest for him.
    * @param _user address of the user
    * @return the total redirected balance
    **/
    function getRedirectedBalance(address _user) external view returns(uint256) {
        return redirectedBalances[_user];
    }

    /**
    * @dev accumulates the accrued interest of the user to the principal balance
    * @param _user the address of the user for which the interest is being accumulated
    * @return the previous principal balance, the new principal balance, the balance increase
    * and the new user index
    **/
    function cumulateBalanceInternal(address _user)
        internal
        returns(uint256, uint256, uint256, uint256) {

        uint256 previousPrincipalBalance = super.balanceOf(_user);

        //calculate the accrued interest since the last accumulation
        uint256 balanceIncrease = balanceOf(_user).sub(previousPrincipalBalance);
        //mints an amount of tokens equivalent to the amount accumulated
        _mint(_user, balanceIncrease);
        //updates the user index
        uint256 index = userIndexes[_user] = core.getReserveNormalizedIncome(underlyingAssetAddress);
        return (
            previousPrincipalBalance,
            previousPrincipalBalance.add(balanceIncrease),
            balanceIncrease,
            index
        );
    }

    /**
    * @dev updates the redirected balance of the user. If the user is not redirecting his
    * interest, nothing is executed.
    * @param _user the address of the user for which the interest is being accumulated
    * @param _balanceToAdd the amount to add to the redirected balance
    * @param _balanceToRemove the amount to remove from the redirected balance
    **/
    function updateRedirectedBalanceOfRedirectionAddressInternal(
        address _user,
        uint256 _balanceToAdd,
        uint256 _balanceToRemove
    ) internal {

        address redirectionAddress = interestRedirectionAddresses[_user];
        //if there isn't any redirection, nothing to be done
        if(redirectionAddress == address(0)){
            return;
        }

        //compound balances of the redirected address
        (,,uint256 balanceIncrease, uint256 index) = cumulateBalanceInternal(redirectionAddress);

        //updating the redirected balance
        redirectedBalances[redirectionAddress] = redirectedBalances[redirectionAddress]
            .add(_balanceToAdd)
            .sub(_balanceToRemove);

        //if the interest of redirectionAddress is also being redirected, we need to update
        //the redirected balance of the redirection target by adding the balance increase
        address targetOfRedirectionAddress = interestRedirectionAddresses[redirectionAddress];

        if(targetOfRedirectionAddress != address(0)){
            redirectedBalances[targetOfRedirectionAddress] = redirectedBalances[targetOfRedirectionAddress].add(balanceIncrease);
        }

        emit RedirectedBalanceUpdated(
            redirectionAddress,
            balanceIncrease,
            index,
            _balanceToAdd,
            _balanceToRemove
        );
    }

    /**
    * @dev calculate the interest accrued by _user on a specific balance
    * @param _user the address of the user for which the interest is being accumulated
    * @param _balance the balance on which the interest is calculated
    * @return the interest rate accrued
    **/
    function calculateCumulatedBalanceInternal(
        address _user,
        uint256 _balance
    ) internal view returns (uint256) {
        return _balance
            .wadToRay()
            .rayMul(core.getReserveNormalizedIncome(underlyingAssetAddress))
            .rayDiv(userIndexes[_user])
            .rayToWad();
    }

    /**
    * @dev executes the transfer of aTokens, invoked by both _transfer() and
    *      transferOnLiquidation()
    * @param _from the address from which transfer the aTokens
    * @param _to the destination address
    * @param _value the amount to transfer
    **/
    function executeTransferInternal(
        address _from,
        address _to,
        uint256 _value
    ) internal {

        require(_value > 0, "Transferred amount needs to be greater than zero");

        //cumulate the balance of the sender
        (,
        uint256 fromBalance,
        uint256 fromBalanceIncrease,
        uint256 fromIndex
        ) = cumulateBalanceInternal(_from);

        //cumulate the balance of the receiver
        (,
        ,
        uint256 toBalanceIncrease,
        uint256 toIndex
        ) = cumulateBalanceInternal(_to);

        //if the sender is redirecting his interest towards someone else,
        //adds to the redirected balance the accrued interest and removes the amount
        //being transferred
        updateRedirectedBalanceOfRedirectionAddressInternal(_from, fromBalanceIncrease, _value);

        //if the receiver is redirecting his interest towards someone else,
        //adds to the redirected balance the accrued interest and the amount
        //being transferred
        updateRedirectedBalanceOfRedirectionAddressInternal(_to, toBalanceIncrease.add(_value), 0);

        //performs the transfer
        super._transfer(_from, _to, _value);

        bool fromIndexReset = false;
        //reset the user data if the remaining balance is 0
        if(fromBalance.sub(_value) == 0){
            fromIndexReset = resetDataOnZeroBalanceInternal(_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);
    }