From 14af006a2f3e4de58bcef574e40a408315c49984 Mon Sep 17 00:00:00 2001
From: Rooh Afza <96720500+r0ohafza@users.noreply.github.com>
Date: Tue, 12 Jul 2022 12:22:10 -0700
Subject: [PATCH] SEN-139 | feat: use one fixed point math lib (#214)

* feat: use one fixed point math lib

* fix: remove prb-math

* fix: add constant

* fix: use mulWadDown

* fix: rename constant
---
 .gitmodules                   |  3 ---
 lib/prb-math                  |  1 -
 src/core/DefaultRateModel.sol | 18 ++++++++++--------
 src/core/RiskEngine.sol       |  8 ++++----
 4 files changed, 14 insertions(+), 16 deletions(-)
 delete mode 160000 lib/prb-math

diff --git a/.gitmodules b/.gitmodules
index 1c412bd..c8c732a 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,6 +1,3 @@
-[submodule "lib/prb-math"]
-	path = lib/prb-math
-	url = https://github.com/paulrberg/prb-math
 [submodule "lib/oracle"]
 	path = lib/oracle
 	url = https://github.com/sentimentxyz/oracle
diff --git a/lib/prb-math b/lib/prb-math
deleted file mode 160000
index e33a042..0000000
--- a/lib/prb-math
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit e33a042e4d1673fe9b333830b75c4765ccf3f5f2
diff --git a/src/core/DefaultRateModel.sol b/src/core/DefaultRateModel.sol
index fcb31ba..35e4ff7 100644
--- a/src/core/DefaultRateModel.sol
+++ b/src/core/DefaultRateModel.sol
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.15;
 
-import {PRBMathUD60x18} from "prb-math/PRBMathUD60x18.sol";
+import {FixedPointMathLib} from "solmate/utils/FixedPointMathLib.sol";
 import {IRateModel} from "../interface/core/IRateModel.sol";
 import {Errors} from "../utils/Errors.sol";
 
@@ -11,7 +11,7 @@ import {Errors} from "../utils/Errors.sol";
     per block
 */
 contract DefaultRateModel is IRateModel {
-    using PRBMathUD60x18 for uint;
+    using FixedPointMathLib for uint;
 
     /// @notice Constant coefficients with 18 decimals
     uint immutable c1;
@@ -21,6 +21,8 @@ contract DefaultRateModel is IRateModel {
     /// @notice Number of seconds per year
     uint immutable secsPerYear;
 
+    uint constant SCALE = 1e18;
+
     /**
         @notice Contract constructor
         @param _c1 constant coefficient, default value = 1 * 1e17
@@ -55,13 +57,13 @@ contract DefaultRateModel is IRateModel {
         returns (uint)
     {
         uint util = _utilization(liquidity, borrows);
-        return c3.mul(
+        return c3.mulWadDown(
             (
-                util.mul(c1)
-                + util.powu(32).mul(c1)
-                + util.powu(64).mul(c2)
+                util.mulWadDown(c1)
+                + util.rpow(32, SCALE).mulWadDown(c1)
+                + util.rpow(64, SCALE).mulWadDown(c2)
             )
-            .div(secsPerYear)
+            .divWadDown(secsPerYear)
         );
     }
 
@@ -71,6 +73,6 @@ contract DefaultRateModel is IRateModel {
         returns (uint)
     {
         uint totalAssets = liquidity + borrows;
-        return (totalAssets == 0) ? 0 : borrows.div(totalAssets);
+        return (totalAssets == 0) ? 0 : borrows.divWadDown(totalAssets);
     }
 }
\ No newline at end of file
diff --git a/src/core/RiskEngine.sol b/src/core/RiskEngine.sol
index bfbc804..463d94b 100644
--- a/src/core/RiskEngine.sol
+++ b/src/core/RiskEngine.sol
@@ -8,9 +8,9 @@ import {IERC20} from "../interface/tokens/IERC20.sol";
 import {ILToken} from "../interface/tokens/ILToken.sol";
 import {IAccount} from "../interface/core/IAccount.sol";
 import {IRegistry} from "../interface/core/IRegistry.sol";
-import {PRBMathUD60x18} from "prb-math/PRBMathUD60x18.sol";
 import {IRiskEngine} from "../interface/core/IRiskEngine.sol";
 import {IAccountManager} from "../interface/core/IAccountManager.sol";
+import {FixedPointMathLib} from "solmate/utils/FixedPointMathLib.sol";
 
 /**
     @title Risk Engine
@@ -18,7 +18,7 @@ import {IAccountManager} from "../interface/core/IAccountManager.sol";
     analyze the health factor of a given account.
 */
 contract RiskEngine is Ownable, IRiskEngine {
-    using PRBMathUD60x18 for uint;
+    using FixedPointMathLib for uint;
 
     /* -------------------------------------------------------------------------- */
     /*                               STATE VARIABLES                              */
@@ -180,7 +180,7 @@ contract RiskEngine is Ownable, IRiskEngine {
         view
         returns (uint)
     {
-        return oracle.getPrice(token).mul(amt);
+        return oracle.getPrice(token).mulWadDown(amt);
     }
 
     function _isAccountHealthy(uint accountBalance, uint accountBorrows)
@@ -189,6 +189,6 @@ contract RiskEngine is Ownable, IRiskEngine {
         returns (bool)
     {
         return (accountBorrows == 0) ? true :
-            (accountBalance.div(accountBorrows) > balanceToBorrowThreshold);
+            (accountBalance.divWadDown(accountBorrows) > balanceToBorrowThreshold);
     }
 }
\ No newline at end of file