初始化回测核心引擎骨架

crates/fidc-core/src/calendar.rs

@@ -0,0 +1,58 @@
+use std::collections::HashMap;
+
+use chrono::NaiveDate;
+
+#[derive(Debug, Clone)]
+pub struct TradingCalendar {
+    days: Vec<NaiveDate>,
+    index: HashMap<NaiveDate, usize>,
+}
+
+impl TradingCalendar {
+    pub fn new(mut days: Vec<NaiveDate>) -> Self {
+        days.sort_unstable();
+        days.dedup();
+
+        let index = days
+            .iter()
+            .copied()
+            .enumerate()
+            .map(|(idx, day)| (day, idx))
+            .collect();
+
+        Self { days, index }
+    }
+
+    pub fn days(&self) -> &[NaiveDate] {
+        &self.days
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = NaiveDate> + '_ {
+        self.days.iter().copied()
+    }
+
+    pub fn len(&self) -> usize {
+        self.days.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.days.is_empty()
+    }
+
+    pub fn index_of(&self, date: NaiveDate) -> Option<usize> {
+        self.index.get(&date).copied()
+    }
+
+    pub fn previous_day(&self, date: NaiveDate) -> Option<NaiveDate> {
+        let idx = self.index_of(date)?;
+        idx.checked_sub(1).and_then(|prev| self.days.get(prev).copied())
+    }
+
+    pub fn trailing_days(&self, end: NaiveDate, lookback: usize) -> Vec<NaiveDate> {
+        let Some(end_idx) = self.index_of(end) else {
+            return Vec::new();
+        };
+        let start = end_idx.saturating_add(1).saturating_sub(lookback);
+        self.days[start..=end_idx].to_vec()
+    }
+}