From 3cdd67c7403155b73960e662c2ff01ef681c1b87 Mon Sep 17 00:00:00 2001
From: lil perp <chrisheaney30@gmail.com>
Date: Mon, 23 Jan 2023 19:18:15 -0500
Subject: [PATCH] program: enforce min order size when trading against amm
 (#334)

* program: enforce min order size when trading against amm

* CHANGELOG
---
 CHANGELOG.md                            | 2 ++
 programs/drift/src/controller/orders.rs | 8 ++++++--
 programs/drift/src/state/perp_market.rs | 2 +-
 sdk/src/math/orders.ts                  | 4 ++--
 4 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bc7012fa7..a4b7ed081 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Features
 
+- program: enforce min order size when trading against amm ([#334](https://github.com/drift-labs/protocol-v2/pull/334))
+
 ### Fixes
 
 ### Breaking
diff --git a/programs/drift/src/controller/orders.rs b/programs/drift/src/controller/orders.rs
index 9a62ba88b..8b1664427 100644
--- a/programs/drift/src/controller/orders.rs
+++ b/programs/drift/src/controller/orders.rs
@@ -1513,10 +1513,14 @@ pub fn fulfill_perp_order_with_amm(
         }
     };
 
-    if base_asset_amount == 0 {
+    if base_asset_amount < market.amm.min_order_size {
         // if is an actual swap (and not amm jit order) then msg!
         if override_base_asset_amount.is_none() {
-            msg!("Amm cant fulfill order");
+            msg!(
+                "Amm cant fulfill order. base asset amount {} market.amm.min_order_size {}",
+                base_asset_amount,
+                market.amm.min_order_size
+            );
         }
         return Ok((0, 0));
     }
diff --git a/programs/drift/src/state/perp_market.rs b/programs/drift/src/state/perp_market.rs
index 9a91f03e8..14df5ae90 100644
--- a/programs/drift/src/state/perp_market.rs
+++ b/programs/drift/src/state/perp_market.rs
@@ -477,7 +477,7 @@ impl Default for AMM {
             funding_period: 0,
             order_step_size: 0,
             order_tick_size: 0,
-            min_order_size: 0,
+            min_order_size: 1,
             max_position_size: 0,
             volume_24h: 0,
             long_intensity_volume: 0,
diff --git a/sdk/src/math/orders.ts b/sdk/src/math/orders.ts
index ad8a4d330..a081f13d1 100644
--- a/sdk/src/math/orders.ts
+++ b/sdk/src/math/orders.ts
@@ -165,12 +165,12 @@ export function isFillableByVAMM(
 ): boolean {
 	return (
 		(isAuctionComplete(order, slot) &&
-			!calculateBaseAssetAmountForAmmToFulfill(
+			calculateBaseAssetAmountForAmmToFulfill(
 				order,
 				market,
 				oraclePriceData,
 				slot
-			).eq(ZERO)) ||
+			).gte(market.amm.minOrderSize)) ||
 		isOrderExpired(order, ts)
 	);
 }