huskies: merge 998

server/src/pipeline_state/events.rs

@@ -1,9 +1,40 @@
 //! Event bus for pipeline state transitions.
 
-#![allow(unused_imports, dead_code)]
 use chrono::{DateTime, Utc};
+use std::sync::OnceLock;
+use tokio::sync::broadcast;
 
-use super::{BranchName, PipelineEvent, Stage, StoryId};
+use super::{PipelineEvent, Stage, StoryId};
+
+// ── Static transition broadcast channel ─────────────────────────────────────
+
+static TRANSITION_TX: OnceLock<broadcast::Sender<TransitionFired>> = OnceLock::new();
+
+fn get_or_init_tx() -> &'static broadcast::Sender<TransitionFired> {
+    TRANSITION_TX.get_or_init(|| {
+        let (tx, _) = broadcast::channel(256);
+        tx
+    })
+}
+
+/// Subscribe to all pipeline stage transitions.
+///
+/// Every call to [`apply_transition`][super::apply_transition] broadcasts the
+/// resulting [`TransitionFired`] on this channel.  Returns a new receiver that
+/// replays events from the moment of subscription.  Lagged receivers silently
+/// skip missed events — callers should handle
+/// [`broadcast::error::RecvError::Lagged`].
+pub fn subscribe_transitions() -> broadcast::Receiver<TransitionFired> {
+    get_or_init_tx().subscribe()
+}
+
+/// Broadcast `fired` to all active transition subscribers.
+///
+/// Called from [`apply_transition`][super::apply] after writing the new stage
+/// to the CRDT.  No-ops safely when there are no subscribers.
+pub(super) fn try_broadcast(fired: &TransitionFired) {
+    let _ = get_or_init_tx().send(fired.clone());
+}
 
 /// Fired when a pipeline stage transition completes.
 #[derive(Debug, Clone)]
@@ -55,9 +86,9 @@ impl Default for EventBus {
 
 #[cfg(test)]
 mod tests {
+    use super::super::BranchName;
     use super::*;
     use std::num::NonZeroU32;
-    use std::sync::{Arc, Mutex};
 
     fn nz(n: u32) -> NonZeroU32 {
         NonZeroU32::new(n).unwrap()