// File: contracts/protocol/tokenization/StableDebtToken.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

import {DebtTokenBase} from './base/DebtTokenBase.sol';
import {MathUtils} from '../libraries/math/MathUtils.sol';
import {WadRayMath} from '../libraries/math/WadRayMath.sol';
import {IStableDebtToken} from '../../interfaces/IStableDebtToken.sol';
import {Errors} from '../libraries/helpers/Errors.sol';

/**
 * @title StableDebtToken
 * @notice Implements a stable debt token to track the borrowing positions of users
 * at stable rate mode
 * @author Aave
 **/
contract StableDebtToken is IStableDebtToken, DebtTokenBase {
  using WadRayMath for uint256;

  uint256 public constant DEBT_TOKEN_REVISION = 0x1;

  uint256 internal _avgStableRate;
  mapping(address => uint40) internal _timestamps;
  mapping(address => uint256) internal _usersStableRate;
  uint40 internal _totalSupplyTimestamp;

  constructor(
    address pool,
    address underlyingAsset,
    string memory name,
    string memory symbol,
    address incentivesController
  ) public DebtTokenBase(pool, underlyingAsset, name, symbol, incentivesController) {}

  /**
   * @dev Gets the revision of the stable debt token implementation
   * @return The debt token implementation revision
   **/
  function getRevision() internal pure virtual override returns (uint256) {
    return DEBT_TOKEN_REVISION;
  }

  /**
   * @dev Returns the average stable rate across all the stable rate debt
   * @return the average stable rate
   **/
  function getAverageStableRate() external view virtual override returns (uint256) {
    return _avgStableRate;
  }

  /**
   * @dev Returns the timestamp of the last user action
   * @return The last update timestamp
   **/
  function getUserLastUpdated(address user) external view virtual override returns (uint40) {
    return _timestamps[user];
  }

  /**
   * @dev Returns the stable rate of the user
   * @param user The address of the user
   * @return The stable rate of user
   **/
  function getUserStableRate(address user) external view virtual override returns (uint256) {
    return _usersStableRate[user];
  }

  /**
   * @dev Calculates the current user debt balance
   * @return The accumulated debt of the user
   **/
  function balanceOf(address account) public view virtual override returns (uint256) {
    uint256 accountBalance = super.balanceOf(account);
    uint256 stableRate = _usersStableRate[account];
    if (accountBalance == 0) {
      return 0;
    }
    uint256 cumulatedInterest =
      MathUtils.calculateCompoundedInterest(stableRate, _timestamps[account]);
    return accountBalance.rayMul(cumulatedInterest);
  }

  struct MintLocalVars {
    uint256 previousSupply;
    uint256 nextSupply;
    uint256 amountInRay;
    uint256 newStableRate;
    uint256 currentAvgStableRate;
  }

  /**
   * @dev Mints debt token to the `onBehalfOf` address.
   * -  Only callable by the LendingPool
   * - The resulting rate is the weighted average between the rate of the new debt
   * and the rate of the previous debt
   * @param user The address receiving the borrowed underlying, being the delegatee in case
   * of credit delegate, or same as `onBehalfOf` otherwise
   * @param onBehalfOf The address receiving the debt tokens
   * @param amount The amount of debt tokens to mint
   * @param rate The rate of the debt being minted
   **/
  function mint(
    address user,
    address onBehalfOf,
    uint256 amount,
    uint256 rate
  ) external override onlyLendingPool returns (bool) {
    MintLocalVars memory vars;

    if (user != onBehalfOf) {
      _decreaseBorrowAllowance(onBehalfOf, user, amount);
    }

    (, uint256 currentBalance, uint256 balanceIncrease) = _calculateBalanceIncrease(onBehalfOf);

    vars.previousSupply = totalSupply();
    vars.currentAvgStableRate = _avgStableRate;
    vars.nextSupply = _totalSupply = vars.previousSupply.add(amount);

    vars.amountInRay = amount.wadToRay();

    vars.newStableRate = _usersStableRate[onBehalfOf]
      .rayMul(currentBalance.wadToRay())
      .add(vars.amountInRay.rayMul(rate))
      .rayDiv(currentBalance.add(amount).wadToRay());

    require(vars.newStableRate <= type(uint128).max, Errors.SDT_STABLE_DEBT_OVERFLOW);
    _usersStableRate[onBehalfOf] = vars.newStableRate;

    //solium-disable-next-line
    _totalSupplyTimestamp = _timestamps[onBehalfOf] = uint40(block.timestamp);

    // Calculates the updated average stable rate
    vars.currentAvgStableRate = _avgStableRate = vars
      .currentAvgStableRate
      .rayMul(vars.previousSupply.wadToRay())
      .add(rate.rayMul(vars.amountInRay))
      .rayDiv(vars.nextSupply.wadToRay());

    _mint(onBehalfOf, amount.add(balanceIncrease), vars.previousSupply);

    emit Transfer(address(0), onBehalfOf, amount);

    emit Mint(
      user,
      onBehalfOf,
      amount,
      currentBalance,
      balanceIncrease,
      vars.newStableRate,
      vars.currentAvgStableRate,
      vars.nextSupply
    );

    return currentBalance == 0;
  }

  /**
   * @dev Burns debt of `user`
   * @param user The address of the user getting his debt burned
   * @param amount The amount of debt tokens getting burned
   **/
  function burn(address user, uint256 amount) external override onlyLendingPool {
    (, uint256 currentBalance, uint256 balanceIncrease) = _calculateBalanceIncrease(user);

    uint256 previousSupply = totalSupply();
    uint256 newAvgStableRate = 0;
    uint256 nextSupply = 0;
    uint256 userStableRate = _usersStableRate[user];

    // Since the total supply and each single user debt accrue separately,
    // there might be accumulation errors so that the last borrower repaying
    // mght actually try to repay more than the available debt supply.
    // In this case we simply set the total supply and the avg stable rate to 0
    if (previousSupply <= amount) {
      _avgStableRate = 0;
      _totalSupply = 0;
    } else {
      nextSupply = _totalSupply = previousSupply.sub(amount);
      uint256 firstTerm = _avgStableRate.rayMul(previousSupply.wadToRay());
      uint256 secondTerm = userStableRate.rayMul(amount.wadToRay());

      // For the same reason described above, when the last user is repaying it might
      // happen that user rate * user balance > avg rate * total supply. In that case,
      // we simply set the avg rate to 0
      if (secondTerm >= firstTerm) {
        newAvgStableRate = _avgStableRate = _totalSupply = 0;
      } else {
        newAvgStableRate = _avgStableRate = firstTerm.sub(secondTerm).rayDiv(nextSupply.wadToRay());
      }
    }

    if (amount == currentBalance) {
      _usersStableRate[user] = 0;
      _timestamps[user] = 0;
    } else {
      //solium-disable-next-line
      _timestamps[user] = uint40(block.timestamp);
    }
    //solium-disable-next-line
    _totalSupplyTimestamp = uint40(block.timestamp);

    if (balanceIncrease > amount) {
      uint256 amountToMint = balanceIncrease.sub(amount);
      _mint(user, amountToMint, previousSupply);
      emit Mint(
        user,
        user,
        amountToMint,
        currentBalance,
        balanceIncrease,
        userStableRate,
        newAvgStableRate,
        nextSupply
      );
    } else {
      uint256 amountToBurn = amount.sub(balanceIncrease);
      _burn(user, amountToBurn, previousSupply);
      emit Burn(user, amountToBurn, currentBalance, balanceIncrease, newAvgStableRate, nextSupply);
    }

    emit Transfer(user, address(0), amount);
  }

  /**
   * @dev Calculates the increase in balance since the last user interaction
   * @param user The address of the user for which the interest is being accumulated
   * @return The previous principal balance, the new principal balance and the balance increase
   **/
  function _calculateBalanceIncrease(address user)
    internal
    view
    returns (
      uint256,
      uint256,
      uint256
    )
  {
    uint256 previousPrincipalBalance = super.balanceOf(user);

    if (previousPrincipalBalance == 0) {
      return (0, 0, 0);
    }

    // Calculation of the accrued interest since the last accumulation
    uint256 balanceIncrease = balanceOf(user).sub(previousPrincipalBalance);

    return (
      previousPrincipalBalance,
      previousPrincipalBalance.add(balanceIncrease),
      balanceIncrease
    );
  }

  /**
   * @dev Returns the principal and total supply, the average borrow rate and the last supply update timestamp
   **/
  function getSupplyData()
    public
    view
    override
    returns (
      uint256,
      uint256,
      uint256,
      uint40
    )
  {
    uint256 avgRate = _avgStableRate;
    return (super.totalSupply(), _calcTotalSupply(avgRate), avgRate, _totalSupplyTimestamp);
  }

  /**
   * @dev Returns the the total supply and the average stable rate
   **/
  function getTotalSupplyAndAvgRate() public view override returns (uint256, uint256) {
    uint256 avgRate = _avgStableRate;
    return (_calcTotalSupply(avgRate), avgRate);
  }

  /**
   * @dev Returns the total supply
   **/
  function totalSupply() public view override returns (uint256) {
    return _calcTotalSupply(_avgStableRate);
  }

  /**
   * @dev Returns the timestamp at which the total supply was updated
   **/
  function getTotalSupplyLastUpdated() public view override returns (uint40) {
    return _totalSupplyTimestamp;
  }

  /**
   * @dev Returns the principal debt balance of the user from
   * @param user The user's address
   * @return The debt balance of the user since the last burn/mint action
   **/
  function principalBalanceOf(address user) external view virtual override returns (uint256) {
    return super.balanceOf(user);
  }

  /**
   * @dev Calculates the total supply
   * @param avgRate The average rate at which the total supply increases
   * @return The debt balance of the user since the last burn/mint action
   **/
  function _calcTotalSupply(uint256 avgRate) internal view virtual returns (uint256) {
    uint256 principalSupply = super.totalSupply();

    if (principalSupply == 0) {
      return 0;
    }

    uint256 cumulatedInterest =
      MathUtils.calculateCompoundedInterest(avgRate, _totalSupplyTimestamp);

    return principalSupply.rayMul(cumulatedInterest);
  }

  /**
   * @dev Mints stable debt tokens to an user
   * @param account The account receiving the debt tokens
   * @param amount The amount being minted
   * @param oldTotalSupply the total supply before the minting event
   **/
  function _mint(
    address account,
    uint256 amount,
    uint256 oldTotalSupply
  ) internal {
    uint256 oldAccountBalance = _balances[account];
    _balances[account] = oldAccountBalance.add(amount);

    if (address(_incentivesController) != address(0)) {
      _incentivesController.handleAction(account, oldTotalSupply, oldAccountBalance);
    }
  }

  /**
   * @dev Burns stable debt tokens of an user
   * @param account The user getting his debt burned
   * @param amount The amount being burned
   * @param oldTotalSupply The total supply before the burning event
   **/
  function _burn(
    address account,
    uint256 amount,
    uint256 oldTotalSupply
  ) internal {
    uint256 oldAccountBalance = _balances[account];
    _balances[account] = oldAccountBalance.sub(amount, Errors.SDT_BURN_EXCEEDS_BALANCE);

    if (address(_incentivesController) != address(0)) {
      _incentivesController.handleAction(account, oldTotalSupply, oldAccountBalance);
    }
  }
}

// File: contracts/protocol/tokenization/base/DebtTokenBase.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

import {ILendingPool} from '../../../interfaces/ILendingPool.sol';
import {ICreditDelegationToken} from '../../../interfaces/ICreditDelegationToken.sol';
import {
  VersionedInitializable
} from '../../libraries/aave-upgradeability/VersionedInitializable.sol';
import {IncentivizedERC20} from '../IncentivizedERC20.sol';
import {Errors} from '../../libraries/helpers/Errors.sol';

/**
 * @title DebtTokenBase
 * @notice Base contract for different types of debt tokens, like StableDebtToken or VariableDebtToken
 * @author Aave
 */

abstract contract DebtTokenBase is
  IncentivizedERC20,
  VersionedInitializable,
  ICreditDelegationToken
{
  address public immutable UNDERLYING_ASSET_ADDRESS;
  ILendingPool public immutable POOL;

  mapping(address => mapping(address => uint256)) internal _borrowAllowances;

  /**
   * @dev Only lending pool can call functions marked by this modifier
   **/
  modifier onlyLendingPool {
    require(_msgSender() == address(POOL), Errors.CT_CALLER_MUST_BE_LENDING_POOL);
    _;
  }

  /**
   * @dev The metadata of the token will be set on the proxy, that the reason of
   * passing "NULL" and 0 as metadata
   */
  constructor(
    address pool,
    address underlyingAssetAddress,
    string memory name,
    string memory symbol,
    address incentivesController
  ) public IncentivizedERC20(name, symbol, 18, incentivesController) {
    POOL = ILendingPool(pool);
    UNDERLYING_ASSET_ADDRESS = underlyingAssetAddress;
  }

  /**
   * @dev Initializes the debt token.
   * @param name The name of the token
   * @param symbol The symbol of the token
   * @param decimals The decimals of the token
   */
  function initialize(
    uint8 decimals,
    string memory name,
    string memory symbol
  ) public initializer {
    _setName(name);
    _setSymbol(symbol);
    _setDecimals(decimals);
  }

  /**
   * @dev delegates borrowing power to a user on the specific debt token
   * @param delegatee the address receiving the delegated borrowing power
   * @param amount the maximum amount being delegated. Delegation will still
   * respect the liquidation constraints (even if delegated, a delegatee cannot
   * force a delegator HF to go below 1)
   **/
  function approveDelegation(address delegatee, uint256 amount) external override {
    _borrowAllowances[_msgSender()][delegatee] = amount;
    emit BorrowAllowanceDelegated(_msgSender(), delegatee, UNDERLYING_ASSET_ADDRESS, amount);
  }

  /**
   * @dev returns the borrow allowance of the user
   * @param fromUser The user to giving allowance
   * @param toUser The user to give allowance to
   * @return the current allowance of toUser
   **/
  function borrowAllowance(address fromUser, address toUser)
    external
    view
    override
    returns (uint256)
  {
    return _borrowAllowances[fromUser][toUser];
  }

  /**
   * @dev Being non transferrable, the debt token does not implement any of the
   * standard ERC20 functions for transfer and allowance.
   **/
  function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
    recipient;
    amount;
    revert('TRANSFER_NOT_SUPPORTED');
  }

  function allowance(address owner, address spender)
    public
    view
    virtual
    override
    returns (uint256)
  {
    owner;
    spender;
    revert('ALLOWANCE_NOT_SUPPORTED');
  }

  function approve(address spender, uint256 amount) public virtual override returns (bool) {
    spender;
    amount;
    revert('APPROVAL_NOT_SUPPORTED');
  }

  function transferFrom(
    address sender,
    address recipient,
    uint256 amount
  ) public virtual override returns (bool) {
    sender;
    recipient;
    amount;
    revert('TRANSFER_NOT_SUPPORTED');
  }

  function increaseAllowance(address spender, uint256 addedValue)
    public
    virtual
    override
    returns (bool)
  {
    spender;
    addedValue;
    revert('ALLOWANCE_NOT_SUPPORTED');
  }

  function decreaseAllowance(address spender, uint256 subtractedValue)
    public
    virtual
    override
    returns (bool)
  {
    spender;
    subtractedValue;
    revert('ALLOWANCE_NOT_SUPPORTED');
  }

  function _decreaseBorrowAllowance(
    address delegator,
    address delegatee,
    uint256 amount
  ) internal {
    uint256 newAllowance =
      _borrowAllowances[delegator][delegatee].sub(amount, Errors.BORROW_ALLOWANCE_NOT_ENOUGH);

    _borrowAllowances[delegator][delegatee] = newAllowance;

    emit BorrowAllowanceDelegated(delegator, delegatee, UNDERLYING_ASSET_ADDRESS, newAllowance);
  }
}

// File: contracts/interfaces/ILendingPool.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

import {ILendingPoolAddressesProvider} from './ILendingPoolAddressesProvider.sol';
import {DataTypes} from '../protocol/libraries/types/DataTypes.sol';

interface ILendingPool {
  /**
   * @dev Emitted on deposit()
   * @param reserve The address of the underlying asset of the reserve
   * @param user The address initiating the deposit
   * @param onBehalfOf The beneficiary of the deposit, receiving the aTokens
   * @param amount The amount deposited
   * @param referral The referral code used
   **/
  event Deposit(
    address indexed reserve,
    address user,
    address indexed onBehalfOf,
    uint256 amount,
    uint16 indexed referral
  );

  /**
   * @dev Emitted on withdraw()
   * @param reserve The address of the underlyng asset being withdrawn
   * @param user The address initiating the withdrawal, owner of aTokens
   * @param to Address that will receive the underlying
   * @param amount The amount to be withdrawn
   **/
  event Withdraw(address indexed reserve, address indexed user, address indexed to, uint256 amount);

  /**
   * @dev Emitted on borrow() and flashLoan() when debt needs to be opened
   * @param reserve The address of the underlying asset being borrowed
   * @param user The address of the user initiating the borrow(), receiving the funds on borrow() or just
   * initiator of the transaction on flashLoan()
   * @param onBehalfOf The address that will be getting the debt
   * @param amount The amount borrowed out
   * @param borrowRateMode The rate mode: 1 for Stable, 2 for Variable
   * @param borrowRate The numeric rate at which the user has borrowed
   * @param referral The referral code used
   **/
  event Borrow(
    address indexed reserve,
    address user,
    address indexed onBehalfOf,
    uint256 amount,
    uint256 borrowRateMode,
    uint256 borrowRate,
    uint16 indexed referral
  );

  /**
   * @dev Emitted on repay()
   * @param reserve The address of the underlying asset of the reserve
   * @param user The beneficiary of the repayment, getting his debt reduced
   * @param repayer The address of the user initiating the repay(), providing the funds
   * @param amount The amount repaid
   **/
  event Repay(
    address indexed reserve,
    address indexed user,
    address indexed repayer,
    uint256 amount
  );

  /**
   * @dev Emitted on swapBorrowRateMode()
   * @param reserve The address of the underlying asset of the reserve
   * @param user The address of the user swapping his rate mode
   * @param rateMode The rate mode that the user wants to swap to
   **/
  event Swap(address indexed reserve, address indexed user, uint256 rateMode);

  /**
   * @dev Emitted on setUserUseReserveAsCollateral()
   * @param reserve The address of the underlying asset of the reserve
   * @param user The address of the user enabling the usage as collateral
   **/
  event ReserveUsedAsCollateralEnabled(address indexed reserve, address indexed user);

  /**
   * @dev Emitted on setUserUseReserveAsCollateral()
   * @param reserve The address of the underlying asset of the reserve
   * @param user The address of the user enabling the usage as collateral
   **/
  event ReserveUsedAsCollateralDisabled(address indexed reserve, address indexed user);

  /**
   * @dev Emitted on rebalanceStableBorrowRate()
   * @param reserve The address of the underlying asset of the reserve
   * @param user The address of the user for which the rebalance has been executed
   **/
  event RebalanceStableBorrowRate(address indexed reserve, address indexed user);

  /**
   * @dev Emitted on flashLoan()
   * @param target The address of the flash loan receiver contract
   * @param initiator The address initiating the flash loan
   * @param asset The address of the asset being flash borrowed
   * @param amount The amount flash borrowed
   * @param premium The fee flash borrowed
   * @param referralCode The referral code used
   **/
  event FlashLoan(
    address indexed target,
    address indexed initiator,
    address indexed asset,
    uint256 amount,
    uint256 premium,
    uint16 referralCode
  );

  /**
   * @dev Emitted when the pause is triggered.
   */
  event Paused();

  /**
   * @dev Emitted when the pause is lifted.
   */
  event Unpaused();

  /**
   * @dev Emitted when a borrower is liquidated. This event is emitted by the LendingPool via
   * LendingPoolCollateral manager using a DELEGATECALL
   * This allows to have the events in the generated ABI for LendingPool.
   * @param collateralAsset The address of the underlying asset used as collateral, to receive as result of the liquidation
   * @param debtAsset The address of the underlying borrowed asset to be repaid with the liquidation
   * @param user The address of the borrower getting liquidated
   * @param debtToCover The debt amount of borrowed `asset` the liquidator wants to cover
   * @param liquidatedCollateralAmount The amount of collateral received by the liiquidator
   * @param liquidator The address of the liquidator
   * @param receiveAToken `true` if the liquidators wants to receive the collateral aTokens, `false` if he wants
   * to receive the underlying collateral asset directly
   **/
  event LiquidationCall(
    address indexed collateralAsset,
    address indexed debtAsset,
    address indexed user,
    uint256 debtToCover,
    uint256 liquidatedCollateralAmount,
    address liquidator,
    bool receiveAToken
  );

  /**
   * @dev Emitted when the state of a reserve is updated. NOTE: This event is actually declared
   * in the ReserveLogic library and emitted in the updateInterestRates() function. Since the function is internal,
   * the event will actually be fired by the LendingPool contract. The event is therefore replicated here so it
   * gets added to the LendingPool ABI
   * @param reserve The address of the underlying asset 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 ReserveDataUpdated(
    address indexed reserve,
    uint256 liquidityRate,
    uint256 stableBorrowRate,
    uint256 variableBorrowRate,
    uint256 liquidityIndex,
    uint256 variableBorrowIndex
  );

  /**
   * @dev Deposits an `amount` of underlying asset into the reserve, receiving in return overlying aTokens.
   * - E.g. User deposits 100 USDC and gets in return 100 aUSDC
   * @param asset The address of the underlying asset to deposit
   * @param amount The amount to be deposited
   * @param onBehalfOf The address that will receive the aTokens, same as msg.sender if the user
   *   wants to receive them on his own wallet, or a different address if the beneficiary of aTokens
   *   is a different wallet
   * @param referralCode Code used to register the integrator originating the operation, for potential rewards.
   *   0 if the action is executed directly by the user, without any middle-man
   **/
  function deposit(
    address asset,
    uint256 amount,
    address onBehalfOf,
    uint16 referralCode
  ) external;

  /**
   * @dev Withdraws an `amount` of underlying asset from the reserve, burning the equivalent aTokens owned
   * E.g. User has 100 aUSDC, calls withdraw() and receives 100 USDC, burning the 100 aUSDC
   * @param asset The address of the underlying asset to withdraw
   * @param amount The underlying amount to be withdrawn
   *   - Send the value type(uint256).max in order to withdraw the whole aToken balance
   * @param to Address that will receive the underlying, same as msg.sender if the user
   *   wants to receive it on his own wallet, or a different address if the beneficiary is a
   *   different wallet
   * @return The final amount withdrawn
   **/
  function withdraw(
    address asset,
    uint256 amount,
    address to
  ) external returns (uint256);

  /**
   * @dev Allows users to borrow a specific `amount` of the reserve underlying asset, provided that the borrower
   * already deposited enough collateral, or he was given enough allowance by a credit delegator on the
   * corresponding debt token (StableDebtToken or VariableDebtToken)
   * - E.g. User borrows 100 USDC passing as `onBehalfOf` his own address, receiving the 100 USDC in his wallet
   *   and 100 stable/variable debt tokens, depending on the `interestRateMode`
   * @param asset The address of the underlying asset to borrow
   * @param amount The amount to be borrowed
   * @param interestRateMode The interest rate mode at which the user wants to borrow: 1 for Stable, 2 for Variable
   * @param referralCode Code used to register the integrator originating the operation, for potential rewards.
   *   0 if the action is executed directly by the user, without any middle-man
   * @param onBehalfOf Address of the user who will receive the debt. Should be the address of the borrower itself
   * calling the function if he wants to borrow against his own collateral, or the address of the credit delegator
   * if he has been given credit delegation allowance
   **/
  function borrow(
    address asset,
    uint256 amount,
    uint256 interestRateMode,
    uint16 referralCode,
    address onBehalfOf
  ) external;

  /**
   * @notice Repays a borrowed `amount` on a specific reserve, burning the equivalent debt tokens owned
   * - E.g. User repays 100 USDC, burning 100 variable/stable debt tokens of the `onBehalfOf` address
   * @param asset The address of the borrowed underlying asset previously borrowed
   * @param amount The amount to repay
   * - Send the value type(uint256).max in order to repay the whole debt for `asset` on the specific `debtMode`
   * @param rateMode The interest rate mode at of the debt the user wants to repay: 1 for Stable, 2 for Variable
   * @param onBehalfOf Address of the user who will get his debt reduced/removed. Should be the address of the
   * user calling the function if he wants to reduce/remove his own debt, or the address of any other
   * other borrower whose debt should be removed
   * @return The final amount repaid
   **/
  function repay(
    address asset,
    uint256 amount,
    uint256 rateMode,
    address onBehalfOf
  ) external returns (uint256);

  /**
   * @dev Allows a borrower to swap his debt between stable and variable mode, or viceversa
   * @param asset The address of the underlying asset borrowed
   * @param rateMode The rate mode that the user wants to swap to
   **/
  function swapBorrowRateMode(address asset, uint256 rateMode) external;

  /**
   * @dev Rebalances the stable interest rate of a user to the current stable rate defined on the reserve.
   * - Users can be rebalanced if the following conditions are satisfied:
   *     1. Usage ratio is above 95%
   *     2. the current deposit APY is below REBALANCE_UP_THRESHOLD * maxVariableBorrowRate, which means that too much has been
   *        borrowed at a stable rate and depositors are not earning enough
   * @param asset The address of the underlying asset borrowed
   * @param user The address of the user to be rebalanced
   **/
  function rebalanceStableBorrowRate(address asset, address user) external;

  /**
   * @dev Allows depositors to enable/disable a specific deposited asset as collateral
   * @param asset The address of the underlying asset deposited
   * @param useAsCollateral `true` if the user wants to use the deposit as collateral, `false` otherwise
   **/
  function setUserUseReserveAsCollateral(address asset, bool useAsCollateral) external;

  /**
   * @dev Function to liquidate a non-healthy position collateral-wise, with Health Factor below 1
   * - The caller (liquidator) covers `debtToCover` amount of debt of the user getting liquidated, and receives
   *   a proportionally amount of the `collateralAsset` plus a bonus to cover market risk
   * @param collateralAsset The address of the underlying asset used as collateral, to receive as result of the liquidation
   * @param debtAsset The address of the underlying borrowed asset to be repaid with the liquidation
   * @param user The address of the borrower getting liquidated
   * @param debtToCover The debt amount of borrowed `asset` the liquidator wants to cover
   * @param receiveAToken `true` if the liquidators wants to receive the collateral aTokens, `false` if he wants
   * to receive the underlying collateral asset directly
   **/
  function liquidationCall(
    address collateralAsset,
    address debtAsset,
    address user,
    uint256 debtToCover,
    bool receiveAToken
  ) external;

  /**
   * @dev Allows smartcontracts to access the liquidity of the pool within one transaction,
   * as long as the amount taken plus a fee is returned.
   * IMPORTANT There are security concerns for developers of flashloan receiver contracts that must be kept into consideration.
   * For further details please visit https://developers.aave.com
   * @param receiverAddress The address of the contract receiving the funds, implementing the IFlashLoanReceiver interface
   * @param assets The addresses of the assets being flash-borrowed
   * @param amounts The amounts amounts being flash-borrowed
   * @param modes Types of the debt to open if the flash loan is not returned:
   *   0 -> Don't open any debt, just revert if funds can't be transferred from the receiver
   *   1 -> Open debt at stable rate for the value of the amount flash-borrowed to the `onBehalfOf` address
   *   2 -> Open debt at variable rate for the value of the amount flash-borrowed to the `onBehalfOf` address
   * @param onBehalfOf The address  that will receive the debt in the case of using on `modes` 1 or 2
   * @param params Variadic packed params to pass to the receiver as extra information
   * @param referralCode Code used to register the integrator originating the operation, for potential rewards.
   *   0 if the action is executed directly by the user, without any middle-man
   **/
  function flashLoan(
    address receiverAddress,
    address[] calldata assets,
    uint256[] calldata amounts,
    uint256[] calldata modes,
    address onBehalfOf,
    bytes calldata params,
    uint16 referralCode
  ) external;

  /**
   * @dev Returns the user account data across all the reserves
   * @param user The address of the user
   * @return totalCollateralETH the total collateral in ETH of the user
   * @return totalDebtETH the total debt in ETH of the user
   * @return availableBorrowsETH the borrowing power left of the user
   * @return currentLiquidationThreshold the liquidation threshold of the user
   * @return ltv the loan to value of the user
   * @return healthFactor the current health factor of the user
   **/
  function getUserAccountData(address user)
    external
    view
    returns (
      uint256 totalCollateralETH,
      uint256 totalDebtETH,
      uint256 availableBorrowsETH,
      uint256 currentLiquidationThreshold,
      uint256 ltv,
      uint256 healthFactor
    );

  function initReserve(
    address reserve,
    address aTokenAddress,
    address stableDebtAddress,
    address variableDebtAddress,
    address interestRateStrategyAddress
  ) external;

  function setReserveInterestRateStrategyAddress(address reserve, address rateStrategyAddress)
    external;

  function setConfiguration(address reserve, uint256 configuration) external;

  /**
   * @dev Returns the configuration of the reserve
   * @param asset The address of the underlying asset of the reserve
   * @return The configuration of the reserve
   **/
  function getConfiguration(address asset)
    external
    view
    returns (DataTypes.ReserveConfigurationMap memory);

  /**
   * @dev Returns the configuration of the user across all the reserves
   * @param user The user address
   * @return The configuration of the user
   **/
  function getUserConfiguration(address user)
    external
    view
    returns (DataTypes.UserConfigurationMap memory);

  /**
   * @dev Returns the normalized income normalized income of the reserve
   * @param asset The address of the underlying asset of the reserve
   * @return The reserve's normalized income
   */
  function getReserveNormalizedIncome(address asset) external view returns (uint256);

  /**
   * @dev Returns the normalized variable debt per unit of asset
   * @param asset The address of the underlying asset of the reserve
   * @return The reserve normalized variable debt
   */
  function getReserveNormalizedVariableDebt(address asset) external view returns (uint256);

  /**
   * @dev Returns the state and configuration of the reserve
   * @param asset The address of the underlying asset of the reserve
   * @return The state of the reserve
   **/
  function getReserveData(address asset) external view returns (DataTypes.ReserveData memory);

  function finalizeTransfer(
    address asset,
    address from,
    address to,
    uint256 amount,
    uint256 balanceFromAfter,
    uint256 balanceToBefore
  ) external;

  function getReservesList() external view returns (address[] memory);

  function getAddressesProvider() external view returns (ILendingPoolAddressesProvider);

  function setPause(bool val) external;

  function paused() external view returns (bool);
}

// File: contracts/interfaces/ILendingPoolAddressesProvider.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

/**
 * @title LendingPoolAddressesProvider contract
 * @dev Main registry of addresses part of or connected to the protocol, including permissioned roles
 * - Acting also as factory of proxies and admin of those, so with right to change its implementations
 * - Owned by the Aave Governance
 * @author Aave
 **/
interface ILendingPoolAddressesProvider {
  event MarketIdSet(string newMarketId);
  event LendingPoolUpdated(address indexed newAddress);
  event ConfigurationAdminUpdated(address indexed newAddress);
  event EmergencyAdminUpdated(address indexed newAddress);
  event LendingPoolConfiguratorUpdated(address indexed newAddress);
  event LendingPoolCollateralManagerUpdated(address indexed newAddress);
  event PriceOracleUpdated(address indexed newAddress);
  event LendingRateOracleUpdated(address indexed newAddress);
  event ProxyCreated(bytes32 id, address indexed newAddress);
  event AddressSet(bytes32 id, address indexed newAddress, bool hasProxy);

  function getMarketId() external view returns (string memory);

  function setMarketId(string calldata marketId) external;

  function setAddress(bytes32 id, address newAddress) external;

  function setAddressAsProxy(bytes32 id, address impl) external;

  function getAddress(bytes32 id) external view returns (address);

  function getLendingPool() external view returns (address);

  function setLendingPoolImpl(address pool) external;

  function getLendingPoolConfigurator() external view returns (address);

  function setLendingPoolConfiguratorImpl(address configurator) external;

  function getLendingPoolCollateralManager() external view returns (address);

  function setLendingPoolCollateralManager(address manager) external;

  function getPoolAdmin() external view returns (address);

  function setPoolAdmin(address admin) external;

  function getEmergencyAdmin() external view returns (address);

  function setEmergencyAdmin(address admin) external;

  function getPriceOracle() external view returns (address);

  function setPriceOracle(address priceOracle) external;

  function getLendingRateOracle() external view returns (address);

  function setLendingRateOracle(address lendingRateOracle) external;
}

// File: contracts/protocol/libraries/types/DataTypes.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

library DataTypes {
  // refer to the whitepaper, section 1.1 basic concepts for a formal description of these properties.
  struct ReserveData {
    //stores the reserve configuration
    ReserveConfigurationMap configuration;
    //the liquidity index. Expressed in ray
    uint128 liquidityIndex;
    //variable borrow index. Expressed in ray
    uint128 variableBorrowIndex;
    //the current supply rate. Expressed in ray
    uint128 currentLiquidityRate;
    //the current variable borrow rate. Expressed in ray
    uint128 currentVariableBorrowRate;
    //the current stable borrow rate. Expressed in ray
    uint128 currentStableBorrowRate;
    uint40 lastUpdateTimestamp;
    //tokens addresses
    address aTokenAddress;
    address stableDebtTokenAddress;
    address variableDebtTokenAddress;
    //address of the interest rate strategy
    address interestRateStrategyAddress;
    //the id of the reserve. Represents the position in the list of the active reserves
    uint8 id;
  }

  struct ReserveConfigurationMap {
    //bit 0-15: LTV
    //bit 16-31: Liq. threshold
    //bit 32-47: Liq. bonus
    //bit 48-55: Decimals
    //bit 56: Reserve is active
    //bit 57: reserve is frozen
    //bit 58: borrowing is enabled
    //bit 59: stable rate borrowing enabled
    //bit 60-63: reserved
    //bit 64-79: reserve factor
    uint256 data;
  }

  struct UserConfigurationMap {
    uint256 data;
  }

  enum InterestRateMode {NONE, STABLE, VARIABLE}
}

// File: contracts/interfaces/ICreditDelegationToken.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

interface ICreditDelegationToken {
  event BorrowAllowanceDelegated(
    address indexed fromUser,
    address indexed toUser,
    address asset,
    uint256 amount
  );

  /**
   * @dev delegates borrowing power to a user on the specific debt token
   * @param delegatee the address receiving the delegated borrowing power
   * @param amount the maximum amount being delegated. Delegation will still
   * respect the liquidation constraints (even if delegated, a delegatee cannot
   * force a delegator HF to go below 1)
   **/
  function approveDelegation(address delegatee, uint256 amount) external;

  /**
   * @dev returns the borrow allowance of the user
   * @param fromUser The user to giving allowance
   * @param toUser The user to give allowance to
   * @return the current allowance of toUser
   **/
  function borrowAllowance(address fromUser, address toUser) external view returns (uint256);
}

// File: contracts/protocol/libraries/aave-upgradeability/VersionedInitializable.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

/**
 * @title VersionedInitializable
 *
 * @dev Helper contract to implement initializer functions. To use it, replace
 * the constructor with a function that has the `initializer` modifier.
 * WARNING: Unlike constructors, initializer functions must be manually
 * invoked. This applies both to deploying an Initializable contract, as well
 * as extending an Initializable contract via inheritance.
 * WARNING: When used with inheritance, manual care must be taken to not invoke
 * a parent initializer twice, or ensure that all initializers are idempotent,
 * because this is not dealt with automatically as with constructors.
 *
 * @author Aave, inspired by the OpenZeppelin Initializable contract
 */
abstract contract VersionedInitializable {
  /**
   * @dev Indicates that the contract has been initialized.
   */
  uint256 private lastInitializedRevision = 0;

  /**
   * @dev Indicates that the contract is in the process of being initialized.
   */
  bool private initializing;

  /**
   * @dev Modifier to use in the initializer function of a contract.
   */
  modifier initializer() {
    uint256 revision = getRevision();
    require(
      initializing || isConstructor() || revision > lastInitializedRevision,
      'Contract instance has already been initialized'
    );

    bool isTopLevelCall = !initializing;
    if (isTopLevelCall) {
      initializing = true;
      lastInitializedRevision = revision;
    }

    _;

    if (isTopLevelCall) {
      initializing = false;
    }
  }

  /**
   * @dev returns the revision number of the contract
   * Needs to be defined in the inherited class as a constant.
   **/
  function getRevision() internal pure virtual returns (uint256);

  /**
   * @dev Returns true if and only if the function is running in the constructor
   **/
  function isConstructor() private view returns (bool) {
    // extcodesize checks the size of the code stored in an address, and
    // address returns the current address. Since the code is still not
    // deployed when running a constructor, any checks on its code size will
    // yield zero, making it an effective way to detect if a contract is
    // under construction or not.
    uint256 cs;
    //solium-disable-next-line
    assembly {
      cs := extcodesize(address())
    }
    return cs == 0;
  }

  // Reserved storage space to allow for layout changes in the future.
  uint256[50] private ______gap;
}

// File: contracts/protocol/tokenization/IncentivizedERC20.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

import {Context} from '../../dependencies/openzeppelin/contracts/Context.sol';
import {IERC20} from '../../dependencies/openzeppelin/contracts/IERC20.sol';
import {IERC20Detailed} from '../../dependencies/openzeppelin/contracts/IERC20Detailed.sol';
import {SafeMath} from '../../dependencies/openzeppelin/contracts/SafeMath.sol';
import {IAaveIncentivesController} from '../../interfaces/IAaveIncentivesController.sol';

/**
 * @title ERC20
 * @notice Basic ERC20 implementation
 * @author Aave, inspired by the Openzeppelin ERC20 implementation
 **/
contract IncentivizedERC20 is Context, IERC20, IERC20Detailed {
  using SafeMath for uint256;

  IAaveIncentivesController internal immutable _incentivesController;

  mapping(address => uint256) internal _balances;

  mapping(address => mapping(address => uint256)) private _allowances;
  uint256 internal _totalSupply;
  string private _name;
  string private _symbol;
  uint8 private _decimals;

  constructor(
    string memory name,
    string memory symbol,
    uint8 decimals,
    address incentivesController
  ) public {
    _name = name;
    _symbol = symbol;
    _decimals = decimals;
    _incentivesController = IAaveIncentivesController(incentivesController);
  }

  /**
   * @return The name of the token
   **/
  function name() public view override returns (string memory) {
    return _name;
  }

  /**
   * @return The symbol of the token
   **/
  function symbol() public view override returns (string memory) {
    return _symbol;
  }

  /**
   * @return The decimals of the token
   **/
  function decimals() public view override returns (uint8) {
    return _decimals;
  }

  /**
   * @return The total supply of the token
   **/
  function totalSupply() public view virtual override returns (uint256) {
    return _totalSupply;
  }

  /**
   * @return The balance of the token
   **/
  function balanceOf(address account) public view virtual override returns (uint256) {
    return _balances[account];
  }

  /**
   * @dev Executes a transfer of tokens from _msgSender() to recipient
   * @param recipient The recipient of the tokens
   * @param amount The amount of tokens being transferred
   * @return `true` if the transfer succeeds, `false` otherwise
   **/
  function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
    _transfer(_msgSender(), recipient, amount);
    emit Transfer(_msgSender(), recipient, amount);
    return true;
  }

  /**
   * @dev Returns the allowance of spender on the tokens owned by owner
   * @param owner The owner of the tokens
   * @param spender The user allowed to spend the owner's tokens
   * @return The amount of owner's tokens spender is allowed to spend
   **/
  function allowance(address owner, address spender)
    public
    view
    virtual
    override
    returns (uint256)
  {
    return _allowances[owner][spender];
  }

  /**
   * @dev Allows `spender` to spend the tokens owned by _msgSender()
   * @param spender The user allowed to spend _msgSender() tokens
   * @return `true`
   **/
  function approve(address spender, uint256 amount) public virtual override returns (bool) {
    _approve(_msgSender(), spender, amount);
    return true;
  }

  /**
   * @dev Executes a transfer of token from sender to recipient, if _msgSender() is allowed to do so
   * @param sender The owner of the tokens
   * @param recipient The recipient of the tokens
   * @param amount The amount of tokens being transferred
   * @return `true` if the transfer succeeds, `false` otherwise
   **/
  function transferFrom(
    address sender,
    address recipient,
    uint256 amount
  ) public virtual override returns (bool) {
    _transfer(sender, recipient, amount);
    _approve(
      sender,
      _msgSender(),
      _allowances[sender][_msgSender()].sub(amount, 'ERC20: transfer amount exceeds allowance')
    );
    emit Transfer(sender, recipient, amount);
    return true;
  }

  /**
   * @dev Increases the allowance of spender to spend _msgSender() tokens
   * @param spender The user allowed to spend on behalf of _msgSender()
   * @param addedValue The amount being added to the allowance
   * @return `true`
   **/
  function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
    _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
    return true;
  }

  /**
   * @dev Decreases the allowance of spender to spend _msgSender() tokens
   * @param spender The user allowed to spend on behalf of _msgSender()
   * @param subtractedValue The amount being subtracted to the allowance
   * @return `true`
   **/
  function decreaseAllowance(address spender, uint256 subtractedValue)
    public
    virtual
    returns (bool)
  {
    _approve(
      _msgSender(),
      spender,
      _allowances[_msgSender()][spender].sub(
        subtractedValue,
        'ERC20: decreased allowance below zero'
      )
    );
    return true;
  }

  function _transfer(
    address sender,
    address recipient,
    uint256 amount
  ) internal virtual {
    require(sender != address(0), 'ERC20: transfer from the zero address');
    require(recipient != address(0), 'ERC20: transfer to the zero address');

    _beforeTokenTransfer(sender, recipient, amount);

    uint256 oldSenderBalance = _balances[sender];
    _balances[sender] = oldSenderBalance.sub(amount, 'ERC20: transfer amount exceeds balance');
    uint256 oldRecipientBalance = _balances[recipient];
    _balances[recipient] = _balances[recipient].add(amount);

    if (address(_incentivesController) != address(0)) {
      uint256 currentTotalSupply = _totalSupply;
      _incentivesController.handleAction(sender, currentTotalSupply, oldSenderBalance);
      if (sender != recipient) {
        _incentivesController.handleAction(recipient, currentTotalSupply, oldRecipientBalance);
      }
    }
  }

  function _mint(address account, uint256 amount) internal virtual {
    require(account != address(0), 'ERC20: mint to the zero address');

    _beforeTokenTransfer(address(0), account, amount);

    uint256 oldTotalSupply = _totalSupply;
    _totalSupply = oldTotalSupply.add(amount);

    uint256 oldAccountBalance = _balances[account];
    _balances[account] = oldAccountBalance.add(amount);

    if (address(_incentivesController) != address(0)) {
      _incentivesController.handleAction(account, oldTotalSupply, oldAccountBalance);
    }
  }

  function _burn(address account, uint256 amount) internal virtual {
    require(account != address(0), 'ERC20: burn from the zero address');

    _beforeTokenTransfer(account, address(0), amount);

    uint256 oldTotalSupply = _totalSupply;
    _totalSupply = oldTotalSupply.sub(amount);

    uint256 oldAccountBalance = _balances[account];
    _balances[account] = oldAccountBalance.sub(amount, 'ERC20: burn amount exceeds balance');

    if (address(_incentivesController) != address(0)) {
      _incentivesController.handleAction(account, oldTotalSupply, oldAccountBalance);
    }
  }

  function _approve(
    address owner,
    address spender,
    uint256 amount
  ) internal virtual {
    require(owner != address(0), 'ERC20: approve from the zero address');
    require(spender != address(0), 'ERC20: approve to the zero address');

    _allowances[owner][spender] = amount;
    emit Approval(owner, spender, amount);
  }

  function _setName(string memory newName) internal {
    _name = newName;
  }

  function _setSymbol(string memory newSymbol) internal {
    _symbol = newSymbol;
  }

  function _setDecimals(uint8 newDecimals) internal {
    _decimals = newDecimals;
  }

  function _beforeTokenTransfer(
    address from,
    address to,
    uint256 amount
  ) internal virtual {}
}

// File: contracts/dependencies/openzeppelin/contracts/Context.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
  function _msgSender() internal view virtual returns (address payable) {
    return msg.sender;
  }

  function _msgData() internal view virtual returns (bytes memory) {
    this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
    return msg.data;
  }
}

// File: contracts/dependencies/openzeppelin/contracts/IERC20.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
  /**
   * @dev Returns the amount of tokens in existence.
   */
  function totalSupply() external view returns (uint256);

  /**
   * @dev Returns the amount of tokens owned by `account`.
   */
  function balanceOf(address account) external view returns (uint256);

  /**
   * @dev Moves `amount` tokens from the caller's account to `recipient`.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transfer(address recipient, uint256 amount) external returns (bool);

  /**
   * @dev Returns the remaining number of tokens that `spender` will be
   * allowed to spend on behalf of `owner` through {transferFrom}. This is
   * zero by default.
   *
   * This value changes when {approve} or {transferFrom} are called.
   */
  function allowance(address owner, address spender) external view returns (uint256);

  /**
   * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * IMPORTANT: Beware that changing an allowance with this method brings the risk
   * that someone may use both the old and the new allowance by unfortunate
   * transaction ordering. One possible solution to mitigate this race
   * condition is to first reduce the spender's allowance to 0 and set the
   * desired value afterwards:
   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   *
   * Emits an {Approval} event.
   */
  function approve(address spender, uint256 amount) external returns (bool);

  /**
   * @dev Moves `amount` tokens from `sender` to `recipient` using the
   * allowance mechanism. `amount` is then deducted from the caller's
   * allowance.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transferFrom(
    address sender,
    address recipient,
    uint256 amount
  ) external returns (bool);

  /**
   * @dev Emitted when `value` tokens are moved from one account (`from`) to
   * another (`to`).
   *
   * Note that `value` may be zero.
   */
  event Transfer(address indexed from, address indexed to, uint256 value);

  /**
   * @dev Emitted when the allowance of a `spender` for an `owner` is set by
   * a call to {approve}. `value` is the new allowance.
   */
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: contracts/dependencies/openzeppelin/contracts/IERC20Detailed.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

import {IERC20} from './IERC20.sol';

interface IERC20Detailed is IERC20 {
  function name() external view returns (string memory);

  function symbol() external view returns (string memory);

  function decimals() external view returns (uint8);
}

// File: contracts/dependencies/openzeppelin/contracts/SafeMath.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
  /**
   * @dev Returns the addition of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `+` operator.
   *
   * Requirements:
   * - Addition cannot overflow.
   */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, 'SafeMath: addition overflow');

    return c;
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   * - Subtraction cannot overflow.
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    return sub(a, b, 'SafeMath: subtraction overflow');
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   * - Subtraction cannot overflow.
   */
  function sub(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    require(b <= a, errorMessage);
    uint256 c = a - b;

    return c;
  }

  /**
   * @dev Returns the multiplication of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `*` operator.
   *
   * Requirements:
   * - Multiplication cannot overflow.
   */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b, 'SafeMath: multiplication overflow');

    return c;
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    return div(a, b, 'SafeMath: division by zero');
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function div(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    // Solidity only automatically asserts when dividing by 0
    require(b > 0, errorMessage);
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold

    return c;
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * Reverts when dividing by zero.
   *
   * Counterpart to Solidity's `%` operator. This function uses a `revert`
   * opcode (which leaves remaining gas untouched) while Solidity uses an
   * invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    return mod(a, b, 'SafeMath: modulo by zero');
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * Reverts with custom message when dividing by zero.
   *
   * Counterpart to Solidity's `%` operator. This function uses a `revert`
   * opcode (which leaves remaining gas untouched) while Solidity uses an
   * invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   * - The divisor cannot be zero.
   */
  function mod(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    require(b != 0, errorMessage);
    return a % b;
  }
}

// File: contracts/interfaces/IAaveIncentivesController.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

interface IAaveIncentivesController {
  function handleAction(
    address user,
    uint256 userBalance,
    uint256 totalSupply
  ) external;
}

// File: contracts/protocol/libraries/helpers/Errors.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

/**
 * @title Errors library
 * @author Aave
 * @notice Defines the error messages emitted by the different contracts of the Aave protocol
 * @dev Error messages prefix glossary:
 *  - VL = ValidationLogic
 *  - MATH = Math libraries
 *  - CT = Common errors between tokens (AToken, VariableDebtToken and StableDebtToken)
 *  - AT = AToken
 *  - SDT = StableDebtToken
 *  - VDT = VariableDebtToken
 *  - LP = LendingPool
 *  - LPAPR = LendingPoolAddressesProviderRegistry
 *  - LPC = LendingPoolConfiguration
 *  - RL = ReserveLogic
 *  - LPCM = LendingPoolCollateralManager
 *  - P = Pausable
 */
library Errors {
  //common errors
  string public constant CALLER_NOT_POOL_ADMIN = '33'; // 'The caller must be the pool admin'
  string public constant BORROW_ALLOWANCE_NOT_ENOUGH = '59'; // User borrows on behalf, but allowance are too small

  //contract specific errors
  string public constant VL_INVALID_AMOUNT = '1'; // 'Amount must be greater than 0'
  string public constant VL_NO_ACTIVE_RESERVE = '2'; // 'Action requires an active reserve'
  string public constant VL_RESERVE_FROZEN = '3'; // 'Action cannot be performed because the reserve is frozen'
  string public constant VL_CURRENT_AVAILABLE_LIQUIDITY_NOT_ENOUGH = '4'; // 'The current liquidity is not enough'
  string public constant VL_NOT_ENOUGH_AVAILABLE_USER_BALANCE = '5'; // 'User cannot withdraw more than the available balance'
  string public constant VL_TRANSFER_NOT_ALLOWED = '6'; // 'Transfer cannot be allowed.'
  string public constant VL_BORROWING_NOT_ENABLED = '7'; // 'Borrowing is not enabled'
  string public constant VL_INVALID_INTEREST_RATE_MODE_SELECTED = '8'; // 'Invalid interest rate mode selected'
  string public constant VL_COLLATERAL_BALANCE_IS_0 = '9'; // 'The collateral balance is 0'
  string public constant VL_HEALTH_FACTOR_LOWER_THAN_LIQUIDATION_THRESHOLD = '10'; // 'Health factor is lesser than the liquidation threshold'
  string public constant VL_COLLATERAL_CANNOT_COVER_NEW_BORROW = '11'; // 'There is not enough collateral to cover a new borrow'
  string public constant VL_STABLE_BORROWING_NOT_ENABLED = '12'; // stable borrowing not enabled
  string public constant VL_COLLATERAL_SAME_AS_BORROWING_CURRENCY = '13'; // collateral is (mostly) the same currency that is being borrowed
  string public constant VL_AMOUNT_BIGGER_THAN_MAX_LOAN_SIZE_STABLE = '14'; // 'The requested amount is greater than the max loan size in stable rate mode
  string public constant VL_NO_DEBT_OF_SELECTED_TYPE = '15'; // 'for repayment of stable debt, the user needs to have stable debt, otherwise, he needs to have variable debt'
  string public constant VL_NO_EXPLICIT_AMOUNT_TO_REPAY_ON_BEHALF = '16'; // 'To repay on behalf of an user an explicit amount to repay is needed'
  string public constant VL_NO_STABLE_RATE_LOAN_IN_RESERVE = '17'; // 'User does not have a stable rate loan in progress on this reserve'
  string public constant VL_NO_VARIABLE_RATE_LOAN_IN_RESERVE = '18'; // 'User does not have a variable rate loan in progress on this reserve'
  string public constant VL_UNDERLYING_BALANCE_NOT_GREATER_THAN_0 = '19'; // 'The underlying balance needs to be greater than 0'
  string public constant VL_DEPOSIT_ALREADY_IN_USE = '20'; // 'User deposit is already being used as collateral'
  string public constant LP_NOT_ENOUGH_STABLE_BORROW_BALANCE = '21'; // 'User does not have any stable rate loan for this reserve'
  string public constant LP_INTEREST_RATE_REBALANCE_CONDITIONS_NOT_MET = '22'; // 'Interest rate rebalance conditions were not met'
  string public constant LP_LIQUIDATION_CALL_FAILED = '23'; // 'Liquidation call failed'
  string public constant LP_NOT_ENOUGH_LIQUIDITY_TO_BORROW = '24'; // 'There is not enough liquidity available to borrow'
  string public constant LP_REQUESTED_AMOUNT_TOO_SMALL = '25'; // 'The requested amount is too small for a FlashLoan.'
  string public constant LP_INCONSISTENT_PROTOCOL_ACTUAL_BALANCE = '26'; // 'The actual balance of the protocol is inconsistent'
  string public constant LP_CALLER_NOT_LENDING_POOL_CONFIGURATOR = '27'; // 'The caller of the function is not the lending pool configurator'
  string public constant LP_INCONSISTENT_FLASHLOAN_PARAMS = '28';
  string public constant CT_CALLER_MUST_BE_LENDING_POOL = '29'; // 'The caller of this function must be a lending pool'
  string public constant CT_CANNOT_GIVE_ALLOWANCE_TO_HIMSELF = '30'; // 'User cannot give allowance to himself'
  string public constant CT_TRANSFER_AMOUNT_NOT_GT_0 = '31'; // 'Transferred amount needs to be greater than zero'
  string public constant RL_RESERVE_ALREADY_INITIALIZED = '32'; // 'Reserve has already been initialized'
  string public constant LPC_RESERVE_LIQUIDITY_NOT_0 = '34'; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_ATOKEN_POOL_ADDRESS = '35'; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_STABLE_DEBT_TOKEN_POOL_ADDRESS = '36'; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_VARIABLE_DEBT_TOKEN_POOL_ADDRESS = '37'; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_STABLE_DEBT_TOKEN_UNDERLYING_ADDRESS = '38'; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_VARIABLE_DEBT_TOKEN_UNDERLYING_ADDRESS = '39'; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_ADDRESSES_PROVIDER_ID = '40'; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_CONFIGURATION = '75'; // 'Invalid risk parameters for the reserve'
  string public constant LPC_CALLER_NOT_EMERGENCY_ADMIN = '76'; // 'The caller must be the emergency admin'
  string public constant LPAPR_PROVIDER_NOT_REGISTERED = '41'; // 'Provider is not registered'
  string public constant LPCM_HEALTH_FACTOR_NOT_BELOW_THRESHOLD = '42'; // 'Health factor is not below the threshold'
  string public constant LPCM_COLLATERAL_CANNOT_BE_LIQUIDATED = '43'; // 'The collateral chosen cannot be liquidated'
  string public constant LPCM_SPECIFIED_CURRENCY_NOT_BORROWED_BY_USER = '44'; // 'User did not borrow the specified currency'
  string public constant LPCM_NOT_ENOUGH_LIQUIDITY_TO_LIQUIDATE = '45'; // "There isn't enough liquidity available to liquidate"
  string public constant LPCM_NO_ERRORS = '46'; // 'No errors'
  string public constant LP_INVALID_FLASHLOAN_MODE = '47'; //Invalid flashloan mode selected
  string public constant MATH_MULTIPLICATION_OVERFLOW = '48';
  string public constant MATH_ADDITION_OVERFLOW = '49';
  string public constant MATH_DIVISION_BY_ZERO = '50';
  string public constant RL_LIQUIDITY_INDEX_OVERFLOW = '51'; //  Liquidity index overflows uint128
  string public constant RL_VARIABLE_BORROW_INDEX_OVERFLOW = '52'; //  Variable borrow index overflows uint128
  string public constant RL_LIQUIDITY_RATE_OVERFLOW = '53'; //  Liquidity rate overflows uint128
  string public constant RL_VARIABLE_BORROW_RATE_OVERFLOW = '54'; //  Variable borrow rate overflows uint128
  string public constant RL_STABLE_BORROW_RATE_OVERFLOW = '55'; //  Stable borrow rate overflows uint128
  string public constant CT_INVALID_MINT_AMOUNT = '56'; //invalid amount to mint
  string public constant LP_FAILED_REPAY_WITH_COLLATERAL = '57';
  string public constant CT_INVALID_BURN_AMOUNT = '58'; //invalid amount to burn
  string public constant LP_FAILED_COLLATERAL_SWAP = '60';
  string public constant LP_INVALID_EQUAL_ASSETS_TO_SWAP = '61';
  string public constant LP_REENTRANCY_NOT_ALLOWED = '62';
  string public constant LP_CALLER_MUST_BE_AN_ATOKEN = '63';
  string public constant LP_IS_PAUSED = '64'; // 'Pool is paused'
  string public constant LP_NO_MORE_RESERVES_ALLOWED = '65';
  string public constant LP_INVALID_FLASH_LOAN_EXECUTOR_RETURN = '66';
  string public constant RC_INVALID_LTV = '67';
  string public constant RC_INVALID_LIQ_THRESHOLD = '68';
  string public constant RC_INVALID_LIQ_BONUS = '69';
  string public constant RC_INVALID_DECIMALS = '70';
  string public constant RC_INVALID_RESERVE_FACTOR = '71';
  string public constant LPAPR_INVALID_ADDRESSES_PROVIDER_ID = '72';
  string public constant VL_INCONSISTENT_FLASHLOAN_PARAMS = '73';
  string public constant LP_INCONSISTENT_PARAMS_LENGTH = '74';
  string public constant UL_INVALID_INDEX = '77';
  string public constant LP_NOT_CONTRACT = '78';
  string public constant SDT_STABLE_DEBT_OVERFLOW = '79';
  string public constant SDT_BURN_EXCEEDS_BALANCE = '80';

  enum CollateralManagerErrors {
    NO_ERROR,
    NO_COLLATERAL_AVAILABLE,
    COLLATERAL_CANNOT_BE_LIQUIDATED,
    CURRRENCY_NOT_BORROWED,
    HEALTH_FACTOR_ABOVE_THRESHOLD,
    NOT_ENOUGH_LIQUIDITY,
    NO_ACTIVE_RESERVE,
    HEALTH_FACTOR_LOWER_THAN_LIQUIDATION_THRESHOLD,
    INVALID_EQUAL_ASSETS_TO_SWAP,
    FROZEN_RESERVE
  }
}

// File: contracts/protocol/libraries/math/MathUtils.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

import {SafeMath} from '../../../dependencies/openzeppelin/contracts/SafeMath.sol';
import {WadRayMath} from './WadRayMath.sol';

library MathUtils {
  using SafeMath for uint256;
  using WadRayMath for uint256;

  /// @dev Ignoring leap years
  uint256 internal constant SECONDS_PER_YEAR = 365 days;

  /**
   * @dev Function to calculate the interest accumulated using a linear interest rate formula
   * @param rate The interest rate, in ray
   * @param lastUpdateTimestamp The timestamp of the last update of the interest
   * @return The interest rate linearly accumulated during the timeDelta, in ray
   **/

  function calculateLinearInterest(uint256 rate, uint40 lastUpdateTimestamp)
    internal
    view
    returns (uint256)
  {
    //solium-disable-next-line
    uint256 timeDifference = block.timestamp.sub(uint256(lastUpdateTimestamp));

    return (rate.mul(timeDifference) / SECONDS_PER_YEAR).add(WadRayMath.ray());
  }

  /**
   * @dev Function to calculate the interest using a compounded interest rate formula
   * To avoid expensive exponentiation, the calculation is performed using a binomial approximation:
   *
   *  (1+x)^n = 1+n*x+[n/2*(n-1)]*x^2+[n/6*(n-1)*(n-2)*x^3...
   *
   * The approximation slightly underpays liquidity providers and undercharges borrowers, with the advantage of great gas cost reductions
   * The whitepaper contains reference to the approximation and a table showing the margin of error per different time periods
   *
   * @param rate The interest rate, in ray
   * @param lastUpdateTimestamp The timestamp of the last update of the interest
   * @return The interest rate compounded during the timeDelta, in ray
   **/
  function calculateCompoundedInterest(
    uint256 rate,
    uint40 lastUpdateTimestamp,
    uint256 currentTimestamp
  ) internal pure returns (uint256) {
    //solium-disable-next-line
    uint256 exp = currentTimestamp.sub(uint256(lastUpdateTimestamp));

    if (exp == 0) {
      return WadRayMath.ray();
    }

    uint256 expMinusOne = exp - 1;

    uint256 expMinusTwo = exp > 2 ? exp - 2 : 0;

    uint256 ratePerSecond = rate / SECONDS_PER_YEAR;

    uint256 basePowerTwo = ratePerSecond.rayMul(ratePerSecond);
    uint256 basePowerThree = basePowerTwo.rayMul(ratePerSecond);

    uint256 secondTerm = exp.mul(expMinusOne).mul(basePowerTwo) / 2;
    uint256 thirdTerm = exp.mul(expMinusOne).mul(expMinusTwo).mul(basePowerThree) / 6;

    return WadRayMath.ray().add(ratePerSecond.mul(exp)).add(secondTerm).add(thirdTerm);
  }

  /**
   * @dev Calculates the compounded interest between the timestamp of the last update and the current block timestamp
   * @param rate The interest rate (in ray)
   * @param lastUpdateTimestamp The timestamp from which the interest accumulation needs to be calculated
   **/
  function calculateCompoundedInterest(uint256 rate, uint40 lastUpdateTimestamp)
    internal
    view
    returns (uint256)
  {
    return calculateCompoundedInterest(rate, lastUpdateTimestamp, block.timestamp);
  }
}

// File: contracts/protocol/libraries/math/WadRayMath.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

import {Errors} from '../helpers/Errors.sol';

/**
 * @title WadRayMath library
 * @author Aave
 * @dev Provides mul and div function for wads (decimal numbers with 18 digits precision) and rays (decimals with 27 digits)
 **/

library WadRayMath {
  uint256 internal constant WAD = 1e18;
  uint256 internal constant halfWAD = WAD / 2;

  uint256 internal constant RAY = 1e27;
  uint256 internal constant halfRAY = RAY / 2;

  uint256 internal constant WAD_RAY_RATIO = 1e9;

  /**
   * @return One ray, 1e27
   **/
  function ray() internal pure returns (uint256) {
    return RAY;
  }

  /**
   * @return One wad, 1e18
   **/

  function wad() internal pure returns (uint256) {
    return WAD;
  }

  /**
   * @return Half ray, 1e27/2
   **/
  function halfRay() internal pure returns (uint256) {
    return halfRAY;
  }

  /**
   * @return Half ray, 1e18/2
   **/
  function halfWad() internal pure returns (uint256) {
    return halfWAD;
  }

  /**
   * @dev Multiplies two wad, rounding half up to the nearest wad
   * @param a Wad
   * @param b Wad
   * @return The result of a*b, in wad
   **/
  function wadMul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0 || b == 0) {
      return 0;
    }

    require(a <= (type(uint256).max - halfWAD) / b, Errors.MATH_MULTIPLICATION_OVERFLOW);

    return (a * b + halfWAD) / WAD;
  }

  /**
   * @dev Divides two wad, rounding half up to the nearest wad
   * @param a Wad
   * @param b Wad
   * @return The result of a/b, in wad
   **/
  function wadDiv(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0, Errors.MATH_DIVISION_BY_ZERO);
    uint256 halfB = b / 2;

    require(a <= (type(uint256).max - halfB) / WAD, Errors.MATH_MULTIPLICATION_OVERFLOW);

    return (a * WAD + halfB) / b;
  }

  /**
   * @dev Multiplies two ray, rounding half up to the nearest ray
   * @param a Ray
   * @param b Ray
   * @return The result of a*b, in ray
   **/
  function rayMul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0 || b == 0) {
      return 0;
    }

    require(a <= (type(uint256).max - halfRAY) / b, Errors.MATH_MULTIPLICATION_OVERFLOW);

    return (a * b + halfRAY) / RAY;
  }

  /**
   * @dev Divides two ray, rounding half up to the nearest ray
   * @param a Ray
   * @param b Ray
   * @return The result of a/b, in ray
   **/
  function rayDiv(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0, Errors.MATH_DIVISION_BY_ZERO);
    uint256 halfB = b / 2;

    require(a <= (type(uint256).max - halfB) / RAY, Errors.MATH_MULTIPLICATION_OVERFLOW);

    return (a * RAY + halfB) / b;
  }

  /**
   * @dev Casts ray down to wad
   * @param a Ray
   * @return a casted to wad, rounded half up to the nearest wad
   **/
  function rayToWad(uint256 a) internal pure returns (uint256) {
    uint256 halfRatio = WAD_RAY_RATIO / 2;
    uint256 result = halfRatio + a;
    require(result >= halfRatio, Errors.MATH_ADDITION_OVERFLOW);

    return result / WAD_RAY_RATIO;
  }

  /**
   * @dev Converts wad up to ray
   * @param a Wad
   * @return a converted in ray
   **/
  function wadToRay(uint256 a) internal pure returns (uint256) {
    uint256 result = a * WAD_RAY_RATIO;
    require(result / WAD_RAY_RATIO == a, Errors.MATH_MULTIPLICATION_OVERFLOW);
    return result;
  }
}

// File: contracts/interfaces/IStableDebtToken.sol



// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.6.12;

/**
 * @title IStableDebtToken
 * @notice Defines the interface for the stable debt token
 * @dev It does not inherit from IERC20 to save in code size
 * @author Aave
 **/

interface IStableDebtToken {
  /**
   * @dev Emitted when new stable debt is minted
   * @param user The address of the user who triggered the minting
   * @param onBehalfOf The recipient of stable debt tokens
   * @param amount The amount minted
   * @param currentBalance The current balance of the user
   * @param balanceIncrease The increase in balance since the last action of the user
   * @param newRate The rate of the debt after the minting
   * @param avgStableRate The new average stable rate after the minting
   * @param newTotalSupply The new total supply of the stable debt token after the action
   **/
  event Mint(
    address indexed user,
    address indexed onBehalfOf,
    uint256 amount,
    uint256 currentBalance,
    uint256 balanceIncrease,
    uint256 newRate,
    uint256 avgStableRate,
    uint256 newTotalSupply
  );

  /**
   * @dev Emitted when new stable debt is burned
   * @param user The address of the user
   * @param amount The amount being burned
   * @param currentBalance The current balance of the user
   * @param balanceIncrease The the increase in balance since the last action of the user
   * @param avgStableRate The new average stable rate after the burning
   * @param newTotalSupply The new total supply of the stable debt token after the action
   **/
  event Burn(
    address indexed user,
    uint256 amount,
    uint256 currentBalance,
    uint256 balanceIncrease,
    uint256 avgStableRate,
    uint256 newTotalSupply
  );

  /**
   * @dev Mints debt token to the `onBehalfOf` address.
   * - The resulting rate is the weighted average between the rate of the new debt
   * and the rate of the previous debt
   * @param user The address receiving the borrowed underlying, being the delegatee in case
   * of credit delegate, or same as `onBehalfOf` otherwise
   * @param onBehalfOf The address receiving the debt tokens
   * @param amount The amount of debt tokens to mint
   * @param rate The rate of the debt being minted
   **/
  function mint(
    address user,
    address onBehalfOf,
    uint256 amount,
    uint256 rate
  ) external returns (bool);

  /**
   * @dev Burns debt of `user`
   * - The resulting rate is the weighted average between the rate of the new debt
   * and the rate of the previous debt
   * @param user The address of the user getting his debt burned
   * @param amount The amount of debt tokens getting burned
   **/
  function burn(address user, uint256 amount) external;

  /**
   * @dev Returns the average rate of all the stable rate loans.
   * @return The average stable rate
   **/
  function getAverageStableRate() external view returns (uint256);

  /**
   * @dev Returns the stable rate of the user debt
   * @return The stable rate of the user
   **/
  function getUserStableRate(address user) external view returns (uint256);

  /**
   * @dev Returns the timestamp of the last update of the user
   * @return The timestamp
   **/
  function getUserLastUpdated(address user) external view returns (uint40);

  /**
   * @dev Returns the principal, the total supply and the average stable rate
   **/
  function getSupplyData()
    external
    view
    returns (
      uint256,
      uint256,
      uint256,
      uint40
    );

  /**
   * @dev Returns the timestamp of the last update of the total supply
   * @return The timestamp
   **/
  function getTotalSupplyLastUpdated() external view returns (uint40);

  /**
   * @dev Returns the total supply and the average stable rate
   **/
  function getTotalSupplyAndAvgRate() external view returns (uint256, uint256);

  /**
   * @dev Returns the principal debt balance of the user
   * @return The debt balance of the user since the last burn/mint action
   **/
  function principalBalanceOf(address user) external view returns (uint256);
}