bigz/improve-withdraw-borrow-guard (#354)

* bigz/improve-withdraw-borrow-guard

* wip: potential better borrow thres (todo: sdk to match)

* align sdk borrow threshold

* spot_withdraw.rs: check both deposit/borrow constraints for resulting borrow

* update changelog.md

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Features
+- program: improve conditions for withdraw/borrow guard ([#354](https://github.com/drift-labs/protocol-v2/pull/354))
 
 ### Fixes
 

programs/drift/src/controller/spot_balance/tests.rs

@@ -419,6 +419,7 @@ fn test_check_withdraw_limits() {
         deposit_balance: 2 * SPOT_BALANCE_PRECISION,
         borrow_balance: SPOT_BALANCE_PRECISION,
         liquidator_fee: LIQUIDATION_FEE_PRECISION / 1000,
+        deposit_token_twap: 26_000_000_000_u64,
         status: MarketStatus::Active,
 
         ..SpotMarket::default()
@@ -458,7 +459,10 @@ fn test_check_withdraw_limits() {
     assert!(valid_withdraw);
 
     let valid_withdraw =
-        check_withdraw_limits(&sol_spot_market, Some(&user), Some(QUOTE_PRECISION)).unwrap();
+        check_withdraw_limits(&sol_spot_market, Some(&user), Some(10_000_000_000)).unwrap();
+    assert!(!valid_withdraw);
+
+    let valid_withdraw = check_withdraw_limits(&sol_spot_market, None, None).unwrap();
     assert!(!valid_withdraw);
 }
 

programs/drift/src/math/spot_withdraw.rs

@@ -5,7 +5,7 @@ use crate::math::casting::Cast;
 use crate::math::safe_math::SafeMath;
 
 use crate::math::spot_balance::get_token_amount;
-use crate::state::spot_market::{SpotBalanceType, SpotMarket};
+use crate::state::spot_market::{SpotBalance, SpotBalanceType, SpotMarket};
 use crate::state::user::User;
 use crate::validate;
 
@@ -26,7 +26,7 @@ pub fn calculate_max_borrow_token_amount(
 ) -> DriftResult<u128> {
     let max_borrow_token = withdraw_guard_threshold.max(
         (deposit_token_amount / 6)
-            .max(borrow_token_twap.safe_add(borrow_token_twap / 5)?)
+            .max(borrow_token_twap.safe_add(deposit_token_amount / 10)?)
             .min(deposit_token_amount.safe_sub(deposit_token_amount / 5)?),
     ); // between ~15-80% utilization with friction on twap
 
@@ -105,8 +105,18 @@ pub fn check_withdraw_limits(
         spot_market.withdraw_guard_threshold.cast()?,
     )?;
 
-    let valid_global_withdrawal =
-        deposit_token_amount >= min_deposit_token && borrow_token_amount <= max_borrow_token;
+    // for resulting deposit or ZERO, check if deposits above minimum
+    // for resulting borrow, check both deposit and borrow constraints
+    let valid_global_withdrawal = if let Some(user) = user {
+        let spot_position_index = user.get_spot_position_index(spot_market.market_index)?;
+        if user.spot_positions[spot_position_index].balance_type() == &SpotBalanceType::Borrow {
+            borrow_token_amount <= max_borrow_token && deposit_token_amount >= min_deposit_token
+        } else {
+            deposit_token_amount >= min_deposit_token
+        }
+    } else {
+        deposit_token_amount >= min_deposit_token && borrow_token_amount <= max_borrow_token
+    };
 
     let valid_withdrawal = if !valid_global_withdrawal {
         msg!(

sdk/src/math/spotBalance.ts

@@ -331,7 +331,7 @@ export function calculateWithdrawLimit(
 		BN.min(
 			BN.max(
 				marketDepositTokenAmount.div(new BN(6)),
-				borrowTokenTwapLive.add(borrowTokenTwapLive.div(new BN(5)))
+				borrowTokenTwapLive.add(marketDepositTokenAmount.div(new BN(10)))
 			),
 			marketDepositTokenAmount.sub(marketDepositTokenAmount.div(new BN(5)))
 		)