From 3df87a8e5d8f289c80612cbe756f66900c2874e9 Mon Sep 17 00:00:00 2001
From: The3D <frangellaemilio@gmail.com>
Date: Thu, 10 Sep 2020 11:25:45 +0200
Subject: [PATCH] Initial commit

---
 contracts/tokenization/StableDebtToken.sol    | 25 ++++++++
 contracts/tokenization/VariableDebtToken.sol  | 62 ++++---------------
 contracts/tokenization/base/DebtTokenBase.sol | 23 -------
 .../interfaces/IVariableDebtToken.sol         | 12 ----
 4 files changed, 38 insertions(+), 84 deletions(-)

diff --git a/contracts/tokenization/StableDebtToken.sol b/contracts/tokenization/StableDebtToken.sol
index 4fdcad09..a30219e3 100644
--- a/contracts/tokenization/StableDebtToken.sol
+++ b/contracts/tokenization/StableDebtToken.sol
@@ -182,4 +182,29 @@ contract StableDebtToken is IStableDebtToken, DebtTokenBase {
 
     emit BurnDebt(user, amount, previousBalance, currentBalance, balanceIncrease);
   }
+
+
+  /**
+   * @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, the balance increase
+   * and the new user index
+   **/
+  function _calculateBalanceIncrease(address user) internal view returns (uint256, uint256, uint256) {
+    uint256 previousPrincipalBalance = principalBalanceOf(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
+    );
+  }
+
 }
diff --git a/contracts/tokenization/VariableDebtToken.sol b/contracts/tokenization/VariableDebtToken.sol
index 580151eb..1fcda07a 100644
--- a/contracts/tokenization/VariableDebtToken.sol
+++ b/contracts/tokenization/VariableDebtToken.sol
@@ -38,27 +38,15 @@ contract VariableDebtToken is DebtTokenBase, IVariableDebtToken {
    * @return the debt balance of the user
    **/
   function balanceOf(address user) public virtual override view returns (uint256) {
-    uint256 userBalance = principalBalanceOf(user);
-    uint256 index = _usersData[user];
-    if (userBalance == 0) {
+    uint256 scaledBalance = principalBalanceOf(user);
+    
+    if (scaledBalance == 0) {
       return 0;
     }
 
     return
-      userBalance
-        .wadToRay()
-        .rayMul(POOL.getReserveNormalizedVariableDebt(UNDERLYING_ASSET))
-        .rayDiv(index)
-        .rayToWad();
-  }
-
-  /**
-   * @dev returns the index of the last user action
-   * @return the user index
-   **/
-
-  function getUserIndex(address user) external virtual override view returns (uint256) {
-    return _usersData[user];
+      scaledBalance
+        .rayMul(POOL.getReserveNormalizedVariableDebt(UNDERLYING_ASSET));
   }
 
   /**
@@ -66,20 +54,12 @@ contract VariableDebtToken is DebtTokenBase, IVariableDebtToken {
    * @param user the user receiving the debt
    * @param amount the amount of debt being minted
    **/
-  function mint(address user, uint256 amount) external override onlyLendingPool {
-    (
-      uint256 previousBalance,
-      uint256 currentBalance,
-      uint256 balanceIncrease
-    ) = _calculateBalanceIncrease(user);
+  function mint(address user, uint256 amount) external override onlyLendingPool { 
+    
+    uint256 index = POOL.getReserveNormalizedVariableDebt(UNDERLYING_ASSET);
 
-    _mint(user, amount.add(balanceIncrease));
-
-    uint256 newUserIndex = POOL.getReserveNormalizedVariableDebt(UNDERLYING_ASSET);
-    require(newUserIndex < (1 << 128), "Debt token: Index overflow");
-    _usersData[user] = newUserIndex;
-
-    emit MintDebt(user, amount, previousBalance, currentBalance, balanceIncrease, newUserIndex);
+    _mint(user, amount.rayDiv(index));
+    emit MintDebt(user, amount, index);
   }
 
   /**
@@ -88,26 +68,10 @@ contract VariableDebtToken is DebtTokenBase, IVariableDebtToken {
    * @param amount the amount of debt being burned
    **/
   function burn(address user, uint256 amount) external override onlyLendingPool {
-    (
-      uint256 previousBalance,
-      uint256 currentBalance,
-      uint256 balanceIncrease
-    ) = _calculateBalanceIncrease(user);
 
-    if (balanceIncrease > amount) {
-      _mint(user, balanceIncrease.sub(amount));
-    } else {
-      _burn(user, amount.sub(balanceIncrease));
-    }
+    uint256 index = POOL.getReserveNormalizedVariableDebt(UNDERLYING_ASSET);
+    _burn(user, amount.rayDiv(index)); 
 
-    uint256 newUserIndex = 0;
-    //if user not repaid everything
-    if (currentBalance != amount) {
-      newUserIndex = POOL.getReserveNormalizedVariableDebt(UNDERLYING_ASSET);
-      require(newUserIndex < (1 << 128), "Debt token: Index overflow");
-    }
-    _usersData[user] = newUserIndex;
-
-    emit BurnDebt(user, amount, previousBalance, currentBalance, balanceIncrease, newUserIndex);
+    emit BurnDebt(user, amount, index);
   }
 }
diff --git a/contracts/tokenization/base/DebtTokenBase.sol b/contracts/tokenization/base/DebtTokenBase.sol
index 04009023..ec021951 100644
--- a/contracts/tokenization/base/DebtTokenBase.sol
+++ b/contracts/tokenization/base/DebtTokenBase.sol
@@ -104,27 +104,4 @@ abstract contract DebtTokenBase is ERC20, VersionedInitializable {
     spender; subtractedValue;
     revert('ALLOWANCE_NOT_SUPPORTED');
   }
-
-  /**
-   * @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, the balance increase
-   * and the new user index
-   **/
-  function _calculateBalanceIncrease(address user) internal view returns (uint256, uint256, uint256) {
-    uint256 previousPrincipalBalance = principalBalanceOf(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
-    );
-  }
 }
diff --git a/contracts/tokenization/interfaces/IVariableDebtToken.sol b/contracts/tokenization/interfaces/IVariableDebtToken.sol
index fdd86a0d..e979b4a5 100644
--- a/contracts/tokenization/interfaces/IVariableDebtToken.sol
+++ b/contracts/tokenization/interfaces/IVariableDebtToken.sol
@@ -12,17 +12,11 @@ interface IVariableDebtToken {
    * @dev emitted when new variable debt is minted
    * @param user the user receiving the debt
    * @param amount the amount of debt being minted
-   * @param previousBalance the previous balance of the user
-   * @param currentBalance the current balance of the user
-   * @param balanceIncrease the debt accumulated since the last action
    * @param index the index of the user
    **/
   event MintDebt(
     address user,
     uint256 amount,
-    uint256 previousBalance,
-    uint256 currentBalance,
-    uint256 balanceIncrease,
     uint256 index
   );
 
@@ -30,17 +24,11 @@ interface IVariableDebtToken {
    * @dev emitted when variable debt is burnt
    * @param user the user which debt has been burned
    * @param amount the amount of debt being burned
-   * @param previousBalance the previous balance of the user
-   * @param currentBalance the current balance of the user
-   * @param balanceIncrease the debt accumulated since the last action
    * @param index the index of the user
    **/
   event BurnDebt(
     address user,
     uint256 amount,
-    uint256 previousBalance,
-    uint256 currentBalance,
-    uint256 balanceIncrease,
     uint256 index
   );