From 42eb38deb07140384045e98d11edda716b273987 Mon Sep 17 00:00:00 2001
From: lil perp <chrisheaney30@gmail.com>
Date: Mon, 23 Dec 2024 14:26:50 -0500
Subject: [PATCH] program: fix small precision issues (#1399)

* program: fix small precision issues

* sdk: add numeratorScale/denominatorScale for getWithdrawalLimit

* update CHANGELOG.md

---------

Co-authored-by: 0xbigz <83473873+0xbigz@users.noreply.github.com>
---
 CHANGELOG.md                      |  1 +
 programs/drift/src/math/margin.rs |  9 +++++++--
 programs/drift/src/math/orders.rs |  9 +++++++--
 sdk/src/user.ts                   | 19 +++++++++++++++----
 4 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 232ef2f92..5f9069dbc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - program: fix force delete user for token 2022 ([#1358](https://github.com/drift-labs/protocol-v2/pull/1358))
 - program: fix liquidating dust prediction mkt position ([#1397](https://github.com/drift-labs/protocol-v2/pull/1397))
+- program: spot market decimals under 6 precision fixes ([#1399](https://github.com/drift-labs/protocol-v2/pull/1399))
 
 ### Breaking
 
diff --git a/programs/drift/src/math/margin.rs b/programs/drift/src/math/margin.rs
index b04f22e56..be883b6ed 100644
--- a/programs/drift/src/math/margin.rs
+++ b/programs/drift/src/math/margin.rs
@@ -801,14 +801,19 @@ pub fn calculate_max_withdrawable_amount(
 
     let free_collateral = calculation.get_free_collateral()?;
 
-    let precision_increase = 10u128.pow(spot_market.decimals - 6);
+    let (numerator_scale, denominator_scale) = if spot_market.decimals > 6 {
+        (10_u128.pow(spot_market.decimals - 6), 1)
+    } else {
+        (1, 10_u128.pow(6 - spot_market.decimals))
+    };
 
     free_collateral
         .safe_mul(MARGIN_PRECISION_U128)?
         .safe_div(asset_weight.cast()?)?
         .safe_mul(PRICE_PRECISION)?
         .safe_div(oracle_price.cast()?)?
-        .safe_mul(precision_increase)?
+        .safe_mul(numerator_scale)?
+        .safe_div(denominator_scale)?
         .cast()
 }
 
diff --git a/programs/drift/src/math/orders.rs b/programs/drift/src/math/orders.rs
index 45553ab34..7d55d761d 100644
--- a/programs/drift/src/math/orders.rs
+++ b/programs/drift/src/math/orders.rs
@@ -1130,12 +1130,17 @@ pub fn calculate_max_spot_order_size(
         user_custom_asset_weight,
     )?;
 
-    let precision_increase = 10i128.pow(spot_market.decimals - 6);
+    let (numerator_scale, denominator_scale) = if spot_market.decimals > 6 {
+        (10_i128.pow(spot_market.decimals - 6), 1)
+    } else {
+        (1, 10_i128.pow(6 - spot_market.decimals))
+    };
 
     let calculate_order_size_and_free_collateral_delta = |free_collateral_delta: u32| {
         let new_order_size = free_collateral
             .safe_sub(OPEN_ORDER_MARGIN_REQUIREMENT.cast()?)?
-            .safe_mul(precision_increase)?
+            .safe_mul(numerator_scale)?
+            .safe_div(denominator_scale)?
             .safe_mul(SPOT_WEIGHT_PRECISION.cast()?)?
             .safe_div(free_collateral_delta.cast()?)?
             .safe_mul(PRICE_PRECISION_I128)?
diff --git a/sdk/src/user.ts b/sdk/src/user.ts
index 2ecae8b8d..16e9c82c8 100644
--- a/sdk/src/user.ts
+++ b/sdk/src/user.ts
@@ -36,7 +36,6 @@ import {
 	QUOTE_PRECISION_EXP,
 	QUOTE_SPOT_MARKET_INDEX,
 	SPOT_MARKET_WEIGHT_PRECISION,
-	TEN,
 	TEN_THOUSAND,
 	TWO,
 	ZERO,
@@ -3540,7 +3539,16 @@ export class User {
 		const freeCollateral = this.getFreeCollateral();
 		const initialMarginRequirement = this.getInitialMarginRequirement();
 		const oracleData = this.getOracleDataForSpotMarket(marketIndex);
-		const precisionIncrease = TEN.pow(new BN(spotMarket.decimals - 6));
+		const { numeratorScale, denominatorScale } =
+			spotMarket.decimals > 6
+				? {
+						numeratorScale: new BN(10).pow(new BN(spotMarket.decimals - 6)),
+						denominatorScale: new BN(1),
+				  }
+				: {
+						numeratorScale: new BN(1),
+						denominatorScale: new BN(10).pow(new BN(6 - spotMarket.decimals)),
+				  };
 
 		const { canBypass, depositAmount: userDepositAmount } =
 			this.canBypassWithdrawLimits(marketIndex);
@@ -3566,7 +3574,9 @@ export class User {
 					PRICE_PRECISION
 				),
 				oracleData.price
-			).mul(precisionIncrease);
+			)
+				.mul(numeratorScale)
+				.div(denominatorScale);
 		}
 
 		const maxWithdrawValue = BN.min(
@@ -3592,7 +3602,8 @@ export class User {
 				.div(new BN(spotMarket.initialLiabilityWeight))
 				.mul(PRICE_PRECISION)
 				.div(oracleData.price)
-				.mul(precisionIncrease);
+				.mul(numeratorScale)
+				.div(denominatorScale);
 
 			const maxBorrowValue = BN.min(
 				maxWithdrawValue.add(maxLiabilityAllowed),