Refactored validation logic of rebalanceStableBorrowRate

contracts/lendingpool/LendingPool.sol

@@ -25,7 +25,6 @@ import {IPriceOracleGetter} from '../interfaces/IPriceOracleGetter.sol';
 import {SafeERC20} from '../dependencies/openzeppelin/contracts/SafeERC20.sol';
 import {ILendingPool} from '../interfaces/ILendingPool.sol';
 import {LendingPoolStorage} from './LendingPoolStorage.sol';
-import {IReserveInterestRateStrategy} from '../interfaces/IReserveInterestRateStrategy.sol';
 
 /**
  * @title LendingPool contract
@@ -39,8 +38,6 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
   using SafeERC20 for IERC20;
 
   //main configuration parameters
-  uint256 public constant REBALANCE_UP_LIQUIDITY_RATE_THRESHOLD = 4000;
-  uint256 public constant REBALANCE_UP_USAGE_RATIO_THRESHOLD = 0.95 * 1e27; //usage ratio of 95%
   uint256 public constant MAX_STABLE_RATE_BORROW_SIZE_PERCENT = 2500;
   uint256 public constant FLASHLOAN_PREMIUM_TOTAL = 9;
   uint256 public constant MAX_NUMBER_RESERVES = 128;
@@ -333,42 +330,22 @@ contract LendingPool is VersionedInitializable, ILendingPool, LendingPoolStorage
     IERC20 variableDebtToken = IERC20(reserve.variableDebtTokenAddress);
     address aTokenAddress = reserve.aTokenAddress;
 
-    uint256 stableBorrowBalance = IERC20(stableDebtToken).balanceOf(user);
+    uint256 stableDebt = IERC20(stableDebtToken).balanceOf(user);
 
-    //if the usage ratio is below 95%, no rebalances are needed
+    ValidationLogic.validateRebalanceStableBorrowRate(
-    uint256 totalBorrows = stableDebtToken
+      reserve,
-      .totalSupply()
+      stableDebtToken,
-      .add(variableDebtToken.totalSupply())
+      variableDebtToken,
-      .wadToRay();
+      aTokenAddress
-    uint256 availableLiquidity = IERC20(asset).balanceOf(aTokenAddress).wadToRay();
-    uint256 usageRatio = totalBorrows == 0
-      ? 0
-      : totalBorrows.rayDiv(availableLiquidity.add(totalBorrows));
-
-    //if the liquidity rate is below REBALANCE_UP_THRESHOLD of the max variable APR at 95% usage,
-    //then we allow rebalancing of the stable rate positions.
-
-    uint256 currentLiquidityRate = reserve.currentLiquidityRate;
-    uint256 maxVariableBorrowRate = IReserveInterestRateStrategy(
-      reserve
-        .interestRateStrategyAddress
-    )
-      .getMaxVariableBorrowRate();
-
-    require(
-      usageRatio >= REBALANCE_UP_USAGE_RATIO_THRESHOLD &&
-        currentLiquidityRate <=
-        maxVariableBorrowRate.percentMul(REBALANCE_UP_LIQUIDITY_RATE_THRESHOLD),
-      Errors.LP_INTEREST_RATE_REBALANCE_CONDITIONS_NOT_MET
     );
 
     reserve.updateState();
 
-    IStableDebtToken(address(stableDebtToken)).burn(user, stableBorrowBalance);
+    IStableDebtToken(address(stableDebtToken)).burn(user, stableDebt);
     IStableDebtToken(address(stableDebtToken)).mint(
       user,
       user,
-      stableBorrowBalance,
+      stableDebt,
       reserve.currentStableBorrowRate
     );
 

contracts/libraries/logic/ValidationLogic.sol

@@ -13,6 +13,7 @@ import {ReserveConfiguration} from '../configuration/ReserveConfiguration.sol';
 import {UserConfiguration} from '../configuration/UserConfiguration.sol';
 import {Errors} from '../helpers/Errors.sol';
 import {Helpers} from '../helpers/Helpers.sol';
+import {IReserveInterestRateStrategy} from '../../interfaces/IReserveInterestRateStrategy.sol';
 
 /**
  * @title ReserveLogic library
@@ -28,6 +29,9 @@ library ValidationLogic {
   using ReserveConfiguration for ReserveConfiguration.Map;
   using UserConfiguration for UserConfiguration.Map;
 
+  uint256 public constant REBALANCE_UP_LIQUIDITY_RATE_THRESHOLD = 4000;
+  uint256 public constant REBALANCE_UP_USAGE_RATIO_THRESHOLD = 0.95 * 1e27; //usage ratio of 95%
+
   /**
    * @dev validates a deposit.
    * @param reserve the reserve state on which the user is depositing
@@ -299,6 +303,42 @@ library ValidationLogic {
     }
   }
 
+  function validateRebalanceStableBorrowRate(
+    ReserveLogic.ReserveData storage reserve,
+    address reserveAddress,
+    IERC20 stableDebtToken,
+    IERC20 variableDebtToken,
+    address aTokenAddress) external {
+
+    //if the usage ratio is below 95%, no rebalances are needed
+    uint256 totalDebt = stableDebtToken
+      .totalSupply()
+      .add(variableDebtToken.totalSupply())
+      .wadToRay();
+    uint256 availableLiquidity = IERC20(reserveAddress).balanceOf(aTokenAddress).wadToRay();
+    uint256 usageRatio = totalDebt == 0
+      ? 0
+      : totalDebt.rayDiv(availableLiquidity.add(totalDebt));
+
+    //if the liquidity rate is below REBALANCE_UP_THRESHOLD of the max variable APR at 95% usage,
+    //then we allow rebalancing of the stable rate positions.
+
+    uint256 currentLiquidityRate = reserve.currentLiquidityRate;
+    uint256 maxVariableBorrowRate = IReserveInterestRateStrategy(
+      reserve
+        .interestRateStrategyAddress
+    )
+      .getMaxVariableBorrowRate();
+
+    require(
+      usageRatio >= REBALANCE_UP_USAGE_RATIO_THRESHOLD &&
+        currentLiquidityRate <=
+        maxVariableBorrowRate.percentMul(REBALANCE_UP_LIQUIDITY_RATE_THRESHOLD),
+      Errors.LP_INTEREST_RATE_REBALANCE_CONDITIONS_NOT_MET
+    );
+
+  }
+
   /**
    * @dev validates the choice of a user of setting (or not) an asset as collateral
    * @param reserve the state of the reserve that the user is enabling or disabling as collateral