docs(irtt-stats): Add documentation comments to public-facing types and fields

Add docstrings to clarify the purpose of statistics collection types and describe the units and behaviors of metric fields.

crates/irtt-stats/src/lib.rs

@@ -1,4 +1,7 @@
 //! Statistics aggregation for `irtt-client` events.
+//!
+//! The crate consumes `irtt-client` events and produces cumulative or rolling
+//! snapshots for reporting and integration code.
 
 #![forbid(unsafe_code)]
 
@@ -20,13 +23,22 @@ use rolling::RollingEvents;
 pub use time_stats::TimeStats;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// Configuration for statistics collection.
 pub struct StatsConfig {
+    /// How timing samples are retained for median-capable metrics.
     pub samples: SampleMode,
+    /// Number of recent normalized events retained for count-based rolling snapshots.
     pub rolling_count: Option<usize>,
+    /// Time span of recent normalized events retained for time-based rolling snapshots.
     pub rolling_time: Option<Duration>,
 }
 
 impl StatsConfig {
+    /// Returns the default configuration for finite runs.
+    ///
+    /// Finite mode retains exact samples where needed for medians and keeps
+    /// unbounded adjacent-sequence IPDV tracking so late adjacent replies can
+    /// still complete IPDV pairs.
     pub fn finite() -> Self {
         Self {
             samples: SampleMode::Exact,
@@ -35,10 +47,11 @@ impl StatsConfig {
         }
     }
 
-    /// Configuration for long-running use.
+    /// Returns a configuration for long-running use.
     ///
-    /// This disables exact sample retention and bounds sequence-adjacent IPDV
-    /// tracking. Exact arbitrary-late IPDV completion is finite-mode behavior.
+    /// Continuous mode uses running statistics, does not retain exact samples
+    /// for medians, and bounds adjacent-sequence IPDV tracking for long-running
+    /// sessions.
     pub fn continuous() -> Self {
         Self {
             samples: SampleMode::RunningOnly,
@@ -55,18 +68,26 @@ impl Default for StatsConfig {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// Controls whether exact timing samples are retained.
 pub enum SampleMode {
+    /// Keep only running statistics; exact medians are not available.
     RunningOnly,
+    /// Retain exact samples for metrics that report exact medians.
     Exact,
 }
 
 #[derive(Debug, Clone, PartialEq)]
+/// Stateful statistics collector for `irtt-client` events.
+///
+/// A collector maintains cumulative statistics and, when configured, rolling
+/// windows. Rolling snapshots are recomputed from retained normalized events.
 pub struct StatsCollector {
     cumulative: CoreStats,
     rolling: RollingEvents,
 }
 
 impl StatsCollector {
+    /// Creates a collector with the supplied configuration.
     pub fn new(config: StatsConfig) -> Self {
         Self {
             cumulative: CoreStats::new(config.samples),
@@ -74,6 +95,11 @@ impl StatsCollector {
         }
     }
 
+    /// Processes one client event and returns the per-event statistics update.
+    ///
+    /// Updates currently report whether the event contributed a unique reply
+    /// timing sample and any adjacent-sequence IPDV pairs completed by this
+    /// event.
     pub fn process(&mut self, event: &ClientEvent) -> EventStatsUpdate {
         let Some(stats_event) = normalize_event(event) else {
             return EventStatsUpdate::default();
@@ -84,92 +110,149 @@ impl StatsCollector {
         update
     }
 
+    /// Returns a snapshot of all events processed by this collector.
     pub fn snapshot(&self) -> Snapshot {
         self.cumulative.snapshot()
     }
 
+    /// Returns the configured count-based rolling snapshot, if enabled.
+    ///
+    /// The snapshot is recomputed from the retained rolling events.
     pub fn rolling_count(&self) -> Option<Snapshot> {
         self.rolling.count_snapshot()
     }
 
+    /// Returns the configured time-based rolling snapshot, if enabled.
+    ///
+    /// The snapshot is recomputed from the retained rolling events.
     pub fn rolling_time(&self) -> Option<Snapshot> {
         self.rolling.time_snapshot()
     }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
+/// Per-event statistics produced by [`StatsCollector::process`].
 pub struct EventStatsUpdate {
+    /// Whether the processed event contributed a unique reply timing sample.
     pub contributed_sample: bool,
+    /// Adjacent-sequence IPDV pairs completed by the processed event.
     pub ipdv_pairs: Vec<IpdvPairUpdate>,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// Adjacent-sequence IPDV pair completed by a processed event.
 pub struct IpdvPairUpdate {
+    /// Sequence number of the earlier reply in the adjacent pair.
     pub previous_seq: u32,
+    /// Sequence number of the later reply in the adjacent pair.
     pub current_seq: u32,
+    /// Absolute round-trip IPDV between the adjacent replies.
     pub rtt_ipdv: Duration,
+    /// Absolute send-side IPDV when send one-way delay is available for both replies.
     pub send_ipdv: Option<Duration>,
+    /// Absolute receive-side IPDV when receive one-way delay is available for both replies.
     pub receive_ipdv: Option<Duration>,
 }
 
 #[derive(Debug, Clone, PartialEq)]
+/// Point-in-time statistics summary.
 pub struct Snapshot {
+    /// Event counters grouped by event class.
     pub events: EventCounts,
+    /// Packet and byte counters.
     pub packets: PacketCounts,
+    /// Packet loss, duplicate, and late-packet percentages.
     pub loss: LossStats,
+    /// Duration of send calls, in nanoseconds.
     pub send_call: TimeStats,
+    /// Sender scheduling error, in nanoseconds.
     pub timer_error: TimeStats,
+    /// Round-trip timing statistics.
     pub rtt: RttStats,
+    /// Inter-packet delay variation statistics.
     pub ipdv: IpdvStats,
+    /// One-way delay statistics.
     pub one_way_delay: OneWayDelayStats,
+    /// Server processing time statistics.
     pub server_processing: ServerProcessingStats,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+/// Counts of normalized client events.
 pub struct EventCounts {
+    /// Probe send events processed.
     pub sent_events: u64,
+    /// On-time unique echo replies processed.
     pub echo_replies: u64,
+    /// Late unique echo replies processed.
     pub late_unique_replies: u64,
+    /// Duplicate echo replies processed.
     pub duplicate_replies: u64,
+    /// Loss events processed.
     pub loss_events: u64,
+    /// Warning events processed.
     pub warning_events: u64,
+    /// Late replies that could not be matched to retained in-flight state.
     pub untracked_late_replies: u64,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+/// Packet, byte, and server-reported receive counters.
 pub struct PacketCounts {
+    /// Probe packets sent by the local client.
     pub packets_sent: u64,
+    /// Reply packets received by the local client, including duplicates and late packets.
     pub packets_received: u64,
+    /// Unique replies received by the local client.
     pub unique_replies: u64,
+    /// Duplicate replies received by the local client.
     pub duplicates: u64,
+    /// Late reply packets received by the local client.
     pub late_packets: u64,
+    /// Probe bytes sent by the local client.
     pub bytes_sent: u64,
+    /// Reply bytes received by the local client.
     pub bytes_received: u64,
+    /// Server-reported packets received, when available.
     pub server_packets_received: Option<u64>,
+    /// Server-reported receive window, when available.
     pub server_received_window: Option<u64>,
 }
 
 #[derive(Debug, Clone, PartialEq)]
+/// Round-trip time statistics.
 pub struct RttStats {
+    /// Effective RTT used for primary RTT reporting and IPDV input.
     pub primary: TimeStats,
+    /// Client-observed raw RTT.
     pub raw: TimeStats,
+    /// RTT adjusted for server processing time when available.
     pub adjusted: TimeStats,
 }
 
 #[derive(Debug, Clone, PartialEq)]
+/// Inter-packet delay variation statistics.
 pub struct IpdvStats {
+    /// Round-trip IPDV.
     pub round_trip: TimeStats,
+    /// Send-side IPDV, when send one-way delay is available.
     pub send: TimeStats,
+    /// Receive-side IPDV, when receive one-way delay is available.
     pub receive: TimeStats,
 }
 
 #[derive(Debug, Clone, PartialEq)]
+/// One-way delay statistics.
 pub struct OneWayDelayStats {
+    /// Client-to-server delay.
     pub send_delay: TimeStats,
+    /// Server-to-client delay.
     pub receive_delay: TimeStats,
 }
 
 #[derive(Debug, Clone, PartialEq)]
+/// Server processing time statistics.
 pub struct ServerProcessingStats {
+    /// Time spent processing a probe at the server.
     pub processing: TimeStats,
 }