From c9f56c34c5637253668d445dccead2d63fb06da2 Mon Sep 17 00:00:00 2001
From: Rooh Afza <96720500+r0ohafza@users.noreply.github.com>
Date: Tue, 18 Oct 2022 12:40:50 -0700
Subject: [PATCH] fix: scale reserves to 18 decimals (#41)

* fix: scale reserves to 18 decimals

* fix: scale reserves to 18 decimals

* remove unused import
---
 src/uniswap/UniV2LPOracle.sol | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/src/uniswap/UniV2LPOracle.sol b/src/uniswap/UniV2LPOracle.sol
index 431a4e1..5f58eca 100644
--- a/src/uniswap/UniV2LPOracle.sol
+++ b/src/uniswap/UniV2LPOracle.sol
@@ -5,6 +5,7 @@ import {IERC20} from "../utils/IERC20.sol";
 import {IOracle} from "../core/IOracle.sol";
 import {IUniswapV2Pair} from "./IUniswapV2Pair.sol";
 import {FixedPointMathLib} from "solmate/utils/FixedPointMathLib.sol";
+
 /**
     @title Uniswap v2 LP Oracle
     @notice Price oracle for uniswap v2 LP Tokens
@@ -41,23 +42,25 @@ contract UniV2LpOracle is IOracle {
         address token0 = IUniswapV2Pair(pair).token0();
         address token1 = IUniswapV2Pair(pair).token1();
 
-        uint decimalSum = IERC20(token0).decimals() + IERC20(token1).decimals();
+        (uint r0, uint r1,) = IUniswapV2Pair(pair).getReserves();
+
+        uint decimals0 = IERC20(token0).decimals();
+        uint decimals1 = IERC20(token1).decimals();
 
-        uint scale;
-        if (decimalSum > 18) scale =  decimalSum - 18;
+        if (decimals0 <= 18)
+            r0 = r0 * 10 ** (18 - decimals0);
+        else r0 = r0 / 10 ** (decimals0 - 18);
 
-        (uint r0, uint r1,) = IUniswapV2Pair(pair).getReserves();
+        if (decimals1 <= 18)
+            r1 = r1 * 10 ** (18 - decimals1);
+        else r1 = r1 / 10 ** (decimals1 - 18);
 
         // 2 * sqrt(r0 * r1 * p0 * p1) / totalSupply
         return FixedPointMathLib.sqrt(
             r0
-            .mulDivDown(r1, 10 ** scale)
-            .mulDivDown(
-                oracle.getPrice(token0),
-                (scale == 0 ? 10 ** decimalSum : 1e18)
-            )
+            .mulWadDown(r1)
+            .mulWadDown(oracle.getPrice(token0))
             .mulWadDown(oracle.getPrice(token1))
-        )
-        .mulDivDown(2e27, IUniswapV2Pair(pair).totalSupply());
+        ).mulDivDown(2e27, IUniswapV2Pair(pair).totalSupply());
     }
 }
\ No newline at end of file