refactor(irtt-stats): extract rolling events module

crates/irtt-stats/src/rolling.rs

@@ -0,0 +1,57 @@
+use std::{collections::VecDeque, time::Duration};
+
+use crate::{CoreStats, SampleMode, Snapshot, StatsConfig, StatsEvent};
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct RollingEvents {
+    count_limit: Option<usize>,
+    time_limit: Option<Duration>,
+    count_events: Option<VecDeque<StatsEvent>>,
+    time_events: Option<VecDeque<StatsEvent>>,
+}
+
+impl RollingEvents {
+    pub(crate) fn new(config: StatsConfig) -> Self {
+        Self {
+            count_limit: config.rolling_count,
+            time_limit: config.rolling_time,
+            count_events: config.rolling_count.map(|_| VecDeque::new()),
+            time_events: config.rolling_time.map(|_| VecDeque::new()),
+        }
+    }
+
+    pub(crate) fn push(&mut self, event: StatsEvent) {
+        if let (Some(limit), Some(window)) = (self.count_limit, self.count_events.as_mut()) {
+            window.push_back(event.clone());
+            while window.len() > limit {
+                window.pop_front();
+            }
+        }
+
+        if let (Some(duration), Some(window)) = (self.time_limit, self.time_events.as_mut()) {
+            let cutoff = event.at().checked_sub(duration);
+            window.push_back(event);
+            if let Some(cutoff) = cutoff {
+                while window.front().is_some_and(|event| event.at() < cutoff) {
+                    window.pop_front();
+                }
+            }
+        }
+    }
+
+    pub(crate) fn count_snapshot(&self) -> Option<Snapshot> {
+        self.count_events.as_ref().map(snapshot_window)
+    }
+
+    pub(crate) fn time_snapshot(&self) -> Option<Snapshot> {
+        self.time_events.as_ref().map(snapshot_window)
+    }
+}
+
+fn snapshot_window(events: &VecDeque<StatsEvent>) -> Snapshot {
+    let mut core = CoreStats::new(SampleMode::RunningOnly);
+    for event in events {
+        core.apply(event.clone());
+    }
+    core.snapshot()
+}