aave-protocol-v2/contracts/adapters/interests-strategies/SushiAmmReserveInterestRateStrategy.sol

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

import {SafeMath} from '../../dependencies/openzeppelin/contracts/SafeMath.sol';
import {WadRayMath} from '../../protocol/libraries/math/WadRayMath.sol';
import {PercentageMath} from '../../protocol/libraries/math/PercentageMath.sol';
import {ILendingPoolAddressesProvider} from '../../interfaces/ILendingPoolAddressesProvider.sol';
import {ILendingRateOracle} from '../../interfaces/ILendingRateOracle.sol';
import {IERC20} from '../../dependencies/openzeppelin/contracts/IERC20.sol';
import {ISushiRewardsAwareAToken} from '../interfaces/sushi/ISushiRewardsAwareAToken.sol';
import {IMasterChef} from '../../adapters/interfaces/sushi/IMasterChef.sol';
import {
  DefaultReserveInterestRateStrategy
} from '../../protocol/lendingpool/DefaultReserveInterestRateStrategy.sol';

/**
 * @title DefaultReserveInterestRateStrategy contract
 * @notice Implements the calculation of the interest rates depending on the reserve state
 * @dev The model of interest rate is based on 2 slopes, one before the `OPTIMAL_UTILIZATION_RATE`
 * point of utilization and another from that one to 100%
 * - An instance of this same contract, can't be used across different Aave markets, due to the caching
 *   of the LendingPoolAddressesProvider
 * @author Aave
 **/
contract SushiAmmReserveInterestRateStrategy is DefaultReserveInterestRateStrategy {
  using WadRayMath for uint256;
  using SafeMath for uint256;
  using PercentageMath for uint256;

  constructor(
    ILendingPoolAddressesProvider provider,
    uint256 optimalUtilizationRate,
    uint256 baseVariableBorrowRate,
    uint256 variableRateSlope1,
    uint256 variableRateSlope2,
    uint256 stableRateSlope1,
    uint256 stableRateSlope2
  )
    public
    DefaultReserveInterestRateStrategy(
      provider,
      optimalUtilizationRate,
      baseVariableBorrowRate,
      variableRateSlope1,
      variableRateSlope2,
      stableRateSlope1,
      stableRateSlope2
    )
  {}

  /**
   * @dev Calculates the interest rates depending on the reserve's state and configurations
   * @param reserve The address of the reserve
   * @param liquidityAdded The liquidity added during the operation
   * @param liquidityTaken The liquidity taken during the operation
   * @param totalStableDebt The total borrowed from the reserve a stable rate
   * @param totalVariableDebt The total borrowed from the reserve at a variable rate
   * @param averageStableBorrowRate The weighted average of all the stable rate loans
   * @param reserveFactor The reserve portion of the interest that goes to the treasury of the market
   * @return The liquidity rate, the stable borrow rate and the variable borrow rate
   **/
  function calculateInterestRates(
    address reserve,
    address aToken,
    uint256 liquidityAdded,
    uint256 liquidityTaken,
    uint256 totalStableDebt,
    uint256 totalVariableDebt,
    uint256 averageStableBorrowRate,
    uint256 reserveFactor
  )
    external
    view
    override
    returns (
      uint256,
      uint256,
      uint256
    )
  {
    uint256 poolId = ISushiRewardsAwareAToken(aToken).getMasterChefPoolId();
    (uint256 stakedBalance, ) =
      IMasterChef(ISushiRewardsAwareAToken(aToken).getMasterChef()).userInfo(poolId, aToken);

    //avoid stack too deep
    uint256 availableLiquidity = stakedBalance.add(liquidityAdded).sub(liquidityTaken);

    return
      calculateInterestRates(
        reserve,
        availableLiquidity,
        totalStableDebt,
        totalVariableDebt,
        averageStableBorrowRate,
        reserveFactor
      );
  }

  /**
   * @dev Calculates the interest rates depending on the reserve's state and configurations.
   * NOTE This function is kept for compatibility with the previous DefaultInterestRateStrategy interface.
   * New protocol implementation uses the new calculateInterestRates() interface
   * @param reserve The address of the reserve
   * @param availableLiquidity The liquidity available in the corresponding aToken
   * @param totalStableDebt The total borrowed from the reserve a stable rate
   * @param totalVariableDebt The total borrowed from the reserve at a variable rate
   * @param averageStableBorrowRate The weighted average of all the stable rate loans
   * @param reserveFactor The reserve portion of the interest that goes to the treasury of the market
   * @return The liquidity rate, the stable borrow rate and the variable borrow rate
   **/
  function calculateInterestRates(
    address reserve,
    uint256 availableLiquidity,
    uint256 totalStableDebt,
    uint256 totalVariableDebt,
    uint256 averageStableBorrowRate,
    uint256 reserveFactor
  )
    public
    view
    virtual
    override
    returns (
      uint256,
      uint256,
      uint256
    )
  {
    CalcInterestRatesLocalVars memory vars;

    vars.totalDebt = totalStableDebt.add(totalVariableDebt);
    vars.currentVariableBorrowRate = 0;
    vars.currentStableBorrowRate = 0;
    vars.currentLiquidityRate = 0;

    vars.utilizationRate = vars.totalDebt == 0
      ? 0
      : vars.totalDebt.rayDiv(availableLiquidity.add(vars.totalDebt));

    vars.currentStableBorrowRate = ILendingRateOracle(addressesProvider.getLendingRateOracle())
      .getMarketBorrowRate(reserve);

    if (vars.utilizationRate > OPTIMAL_UTILIZATION_RATE) {
      uint256 excessUtilizationRateRatio =
        vars.utilizationRate.sub(OPTIMAL_UTILIZATION_RATE).rayDiv(EXCESS_UTILIZATION_RATE);

      vars.currentStableBorrowRate = vars.currentStableBorrowRate.add(_stableRateSlope1).add(
        _stableRateSlope2.rayMul(excessUtilizationRateRatio)
      );

      vars.currentVariableBorrowRate = _baseVariableBorrowRate.add(_variableRateSlope1).add(
        _variableRateSlope2.rayMul(excessUtilizationRateRatio)
      );
    } else {
      vars.currentStableBorrowRate = vars.currentStableBorrowRate.add(
        _stableRateSlope1.rayMul(vars.utilizationRate.rayDiv(OPTIMAL_UTILIZATION_RATE))
      );
      vars.currentVariableBorrowRate = _baseVariableBorrowRate.add(
        vars.utilizationRate.rayMul(_variableRateSlope1).rayDiv(OPTIMAL_UTILIZATION_RATE)
      );
    }

    vars.currentLiquidityRate = _getOverallBorrowRate(
      totalStableDebt,
      totalVariableDebt,
      vars
        .currentVariableBorrowRate,
      averageStableBorrowRate
    )
      .rayMul(vars.utilizationRate)
      .percentMul(PercentageMath.PERCENTAGE_FACTOR.sub(reserveFactor));

    return (
      vars.currentLiquidityRate,
      vars.currentStableBorrowRate,
      vars.currentVariableBorrowRate
    );
  }
}