Close position protocol_fee accounting (#22)

* account for protocol_fee

* nit

* also modify liquidate ix

* nit

* handle fees when maxpayoff is reached

* close_position/liquidate: only pay protocol_fee if possible

* close_position/liquidate: only pay protocol_fee if possible

Author: the-orex

programs/perpetuals/src/instructions/close_position.rs

@@ -233,8 +233,15 @@ pub fn close_position(ctx: Context<ClosePosition>, params: &ClosePositionParams)
     )?;
 
     let protocol_fee = Pool::get_fee_amount(custody.fees.protocol_share, fee_amount)?;
-    collateral_custody.assets.protocol_fees =
-        math::checked_add(collateral_custody.assets.protocol_fees, protocol_fee)?;
+
+    // Pay protocol_fee from custody if possible, otherwise no protocol_fee
+    if pool.check_available_amount(protocol_fee, collateral_custody)? {
+        collateral_custody.assets.protocol_fees =
+            math::checked_add(collateral_custody.assets.protocol_fees, protocol_fee)?;
+
+        collateral_custody.assets.owned =
+            math::checked_sub(collateral_custody.assets.owned, protocol_fee)?;
+    }
 
     // if custody and collateral_custody accounts are the same, ensure that data is in sync
     if position.side == Side::Long && !custody.is_virtual {

programs/perpetuals/src/instructions/liquidate.rs

@@ -254,8 +254,15 @@ pub fn liquidate(ctx: Context<Liquidate>, _params: &LiquidateParams) -> Result<(
     )?;
 
     let protocol_fee = Pool::get_fee_amount(custody.fees.protocol_share, fee_amount)?;
-    collateral_custody.assets.protocol_fees =
-        math::checked_add(collateral_custody.assets.protocol_fees, protocol_fee)?;
+
+    // Pay protocol_fee from custody if possible, otherwise no protocol_fee
+    if pool.check_available_amount(protocol_fee, collateral_custody)? {
+        collateral_custody.assets.protocol_fees =
+            math::checked_add(collateral_custody.assets.protocol_fees, protocol_fee)?;
+
+        collateral_custody.assets.owned =
+            math::checked_sub(collateral_custody.assets.owned, protocol_fee)?;
+    }
 
     // if custody and collateral_custody accounts are the same, ensure that data is in sync
     if position.side == Side::Long && !custody.is_virtual {

programs/perpetuals/src/state/pool.rs

@@ -243,7 +243,10 @@ impl Pool {
         };
         let close_amount = max_collateral_price
             .get_token_amount(available_amount_usd, collateral_custody.decimals)?;
-        let max_amount = math::checked_add(position.locked_amount, position.collateral_amount)?;
+        let max_amount = math::checked_add(
+            position.locked_amount.saturating_sub(fee_amount),
+            position.collateral_amount,
+        )?;
 
         Ok((
             std::cmp::min(max_amount, close_amount),