program: withdraw fee use last active slot(#756)

* bigz/withdraw-fee-use-last-active-slot

* add test, set limit to 50 slots

* update CHANGELOG.md

---------

Co-authored-by: lil perp <[email protected]>

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Features
 
+- program: only consider recent last_active_slot in qualifies_for_withdraw_feen([#756](https://github.com/drift-labs/protocol-v2/pull/756))
 - program: amm can use reference price offset from oracle price based on clamped inventory and persist market premiums ([#681](https://github.com/drift-labs/protocol-v2/pull/681))
 
 ### Fixes

programs/drift/src/instructions/user.rs

@@ -489,7 +489,7 @@ pub fn handle_withdraw(
         let spot_market = &mut spot_market_map.get_ref_mut(&market_index)?;
         let oracle_price_data = oracle_map.get_price_data(&spot_market.oracle)?;
 
-        if user.qualifies_for_withdraw_fee(&user_stats) {
+        if user.qualifies_for_withdraw_fee(&user_stats, slot) {
             let fee =
                 charge_withdraw_fee(spot_market, oracle_price_data.price, user, &mut user_stats)?;
             amount = amount.safe_sub(fee.cast()?)?;

programs/drift/src/state/user.rs

@@ -369,7 +369,12 @@ impl User {
         }
     }
 
-    pub fn qualifies_for_withdraw_fee(&self, user_stats: &UserStats) -> bool {
+    pub fn qualifies_for_withdraw_fee(&self, user_stats: &UserStats, slot: u64) -> bool {
+        // only qualifies for user with recent last_active_slot (~25 seconds)
+        if slot.saturating_sub(self.last_active_slot) >= 50 {
+            return false;
+        }
+
         let min_total_withdraws = 10_000_000 * QUOTE_PRECISION_U64; // $10M
 
         // if total withdraws are greater than $10M and user has paid more than %.01 of it in fees

programs/drift/src/state/user/tests.rs

@@ -1672,7 +1672,7 @@ mod qualifies_for_withdraw_fee {
         let user = User::default();
         let user_stats = UserStats::default();
 
-        let qualifies = user.qualifies_for_withdraw_fee(&user_stats);
+        let qualifies = user.qualifies_for_withdraw_fee(&user_stats, 0);
 
         assert!(!qualifies);
 
@@ -1681,7 +1681,7 @@ mod qualifies_for_withdraw_fee {
             ..User::default()
         };
 
-        let qualifies = user.qualifies_for_withdraw_fee(&user_stats);
+        let qualifies = user.qualifies_for_withdraw_fee(&user_stats, 0);
 
         assert!(!qualifies);
 
@@ -1698,12 +1698,13 @@ mod qualifies_for_withdraw_fee {
             ..UserStats::default()
         };
 
-        let qualifies = user.qualifies_for_withdraw_fee(&user_stats);
+        let qualifies = user.qualifies_for_withdraw_fee(&user_stats, 0);
 
         assert!(!qualifies);
 
         let user = User {
             total_withdraws: 10_000_000 * QUOTE_PRECISION_U64,
+
             ..User::default()
         };
 
@@ -1715,9 +1716,32 @@ mod qualifies_for_withdraw_fee {
             ..UserStats::default()
         };
 
-        let qualifies = user.qualifies_for_withdraw_fee(&user_stats);
+        let qualifies = user.qualifies_for_withdraw_fee(&user_stats, 0);
+
+        assert!(qualifies);
+
+        // fee
+        let user = User {
+            total_withdraws: 13_000_000 * QUOTE_PRECISION_U64,
+            last_active_slot: 8900877,
+            ..User::default()
+        };
+
+        let user_stats = UserStats {
+            fees: UserFees {
+                total_fee_paid: 1 * QUOTE_PRECISION_U64,
+                ..UserFees::default()
+            },
+            ..UserStats::default()
+        };
+
+        let qualifies = user.qualifies_for_withdraw_fee(&user_stats, user.last_active_slot + 1);
 
         assert!(qualifies);
+
+        let qualifies = user.qualifies_for_withdraw_fee(&user_stats, user.last_active_slot + 50);
+
+        assert!(!qualifies);
     }
 }