Expose strategy runtime data APIs

crates/fidc-core/src/calendar.rs

@@ -49,6 +49,43 @@ impl TradingCalendar {
             .and_then(|prev| self.days.get(prev).copied())
     }
 
+    pub fn previous_trading_date(&self, date: NaiveDate, n: usize) -> Option<NaiveDate> {
+        if n == 0 {
+            return None;
+        }
+        let before_count = match self.days.binary_search(&date) {
+            Ok(idx) => idx,
+            Err(idx) => idx,
+        };
+        before_count
+            .checked_sub(n)
+            .and_then(|idx| self.days.get(idx).copied())
+    }
+
+    pub fn next_trading_date(&self, date: NaiveDate, n: usize) -> Option<NaiveDate> {
+        if n == 0 {
+            return None;
+        }
+        let first_after = match self.days.binary_search(&date) {
+            Ok(idx) => idx.saturating_add(1),
+            Err(idx) => idx,
+        };
+        first_after
+            .checked_add(n.saturating_sub(1))
+            .and_then(|idx| self.days.get(idx).copied())
+    }
+
+    pub fn trading_dates(&self, start: NaiveDate, end: NaiveDate) -> Vec<NaiveDate> {
+        if start > end {
+            return Vec::new();
+        }
+        self.days
+            .iter()
+            .copied()
+            .filter(|date| *date >= start && *date <= end)
+            .collect()
+    }
+
     pub fn trailing_days(&self, end: NaiveDate, lookback: usize) -> Vec<NaiveDate> {
         let Some(end_idx) = self.index_of(end) else {
             return Vec::new();