Add management fee callbacks

crates/fidc-core/src/portfolio.rs

@@ -311,6 +311,8 @@ pub struct PortfolioState {
     units: f64,
     cash: f64,
     cash_liabilities: f64,
+    management_fee_rate: f64,
+    management_fees: f64,
     positions: IndexMap<String, Position>,
     cash_receivables: Vec<CashReceivable>,
     pending_cash_flows: Vec<PendingCashFlow>,
@@ -341,6 +343,8 @@ impl PortfolioState {
             units: initial_cash,
             cash: initial_cash,
             cash_liabilities: 0.0,
+            management_fee_rate: 0.0,
+            management_fees: 0.0,
             positions: IndexMap::new(),
             cash_receivables: Vec::new(),
             pending_cash_flows: Vec::new(),
@@ -367,6 +371,14 @@ impl PortfolioState {
         self.cash_liabilities
     }
 
+    pub fn management_fee_rate(&self) -> f64 {
+        self.management_fee_rate
+    }
+
+    pub fn management_fees(&self) -> f64 {
+        self.management_fees
+    }
+
     pub fn positions(&self) -> &IndexMap<String, Position> {
         &self.positions
     }
@@ -484,6 +496,27 @@ impl PortfolioState {
         Ok(())
     }
 
+    pub fn set_management_fee_rate(&mut self, rate: f64) -> Result<(), String> {
+        if !rate.is_finite() || rate < 0.0 {
+            return Err("management fee rate must be finite and non-negative".to_string());
+        }
+        self.management_fee_rate = rate;
+        Ok(())
+    }
+
+    pub fn default_management_fee(&self) -> f64 {
+        self.total_equity().max(0.0) * self.management_fee_rate
+    }
+
+    pub fn apply_management_fee(&mut self, fee: f64) -> Result<(), String> {
+        if !fee.is_finite() || fee < 0.0 {
+            return Err("management fee must be finite and non-negative".to_string());
+        }
+        self.cash -= fee;
+        self.management_fees += fee;
+        Ok(())
+    }
+
     pub fn settle_cash_receivables(&mut self, date: NaiveDate) -> Vec<CashReceivable> {
         let mut settled = Vec::new();
         let mut pending = Vec::new();