gen_server: TimerHandle arm_after/cancel + Sys::Timer dispatch (RFC 015 §4.3, §5)

tests/gen_server.rs

@@ -443,3 +443,95 @@ fn unused_ctx_closes_control_arm_silently() {
     });
     assert_eq!(*got.lock().unwrap(), 42);
 }
+
+// ---------------------------------------------------------------------------
+// RFC 015 — gen_server timers. A server that arms one-shot timers from a cast
+// and records each fire's payload, plus the cancel race signal.
+// ---------------------------------------------------------------------------
+use smarm::gen_server::{ServerCtx, TimerHandle};
+use smarm::TimerId;
+
+enum TkCast {
+    Arm(Duration),
+    CancelLast,
+}
+
+struct Timed {
+    timer: Option<TimerHandle<Self>>,
+    fired: Arc<Mutex<Vec<u32>>>,
+    cancel_won: Arc<Mutex<Option<bool>>>,
+    last: Option<TimerId>,
+}
+
+impl GenServer for Timed {
+    type Call = ();
+    type Reply = usize; // count of fires so far (a sync read point)
+    type Cast = TkCast;
+    type Info = ();
+    type Timer = u32;
+
+    fn init(&mut self, ctx: &ServerCtx<Self>) {
+        self.timer = Some(ctx.timer());
+    }
+
+    fn handle_call(&mut self, _: ()) -> usize {
+        self.fired.lock().unwrap().len()
+    }
+
+    fn handle_cast(&mut self, c: TkCast) {
+        let t = self.timer.as_ref().expect("init ran first");
+        match c {
+            TkCast::Arm(d) => self.last = Some(t.arm_after(d, 7)),
+            TkCast::CancelLast => {
+                let id = self.last.take().expect("a timer was armed");
+                *self.cancel_won.lock().unwrap() = Some(t.cancel(id));
+            }
+        }
+    }
+
+    fn handle_timer(&mut self, msg: u32) {
+        self.fired.lock().unwrap().push(msg);
+    }
+}
+
+fn timed(fired: Arc<Mutex<Vec<u32>>>, cancel_won: Arc<Mutex<Option<bool>>>) -> Timed {
+    Timed { timer: None, fired, cancel_won, last: None }
+}
+
+// A one-shot armed from a handler fires into handle_timer with its payload.
+#[test]
+fn arm_after_fires_into_handle_timer() {
+    let fired = Arc::new(Mutex::new(Vec::new()));
+    let f2 = fired.clone();
+    run(move || {
+        let cw = Arc::new(Mutex::new(None));
+        let server = start(timed(f2, cw));
+        server.cast(TkCast::Arm(Duration::from_millis(10))).unwrap();
+        let _ = server.call(()).unwrap(); // sync: arm done
+        smarm::sleep(Duration::from_millis(40)); // let the timer fire
+        let count = server.call(()).unwrap(); // timer arm outranks this inbox call
+        assert_eq!(count, 1, "the one-shot should have fired exactly once");
+    });
+    assert_eq!(*fired.lock().unwrap(), vec![7]);
+}
+
+// cancel before the deadline wins the race (returns true) and suppresses the
+// fire entirely.
+#[test]
+fn cancel_before_fire_suppresses_it() {
+    let fired = Arc::new(Mutex::new(Vec::new()));
+    let cancel_won = Arc::new(Mutex::new(None));
+    let f2 = fired.clone();
+    let c2 = cancel_won.clone();
+    run(move || {
+        let server = start(timed(f2, c2));
+        server.cast(TkCast::Arm(Duration::from_millis(50))).unwrap();
+        server.cast(TkCast::CancelLast).unwrap();
+        let _ = server.call(()).unwrap(); // sync: arm + cancel both handled
+        smarm::sleep(Duration::from_millis(80)); // past the original deadline
+        let count = server.call(()).unwrap();
+        assert_eq!(count, 0, "cancelled timer must not fire");
+    });
+    assert_eq!(*cancel_won.lock().unwrap(), Some(true), "cancel beat the fire");
+    assert!(fired.lock().unwrap().is_empty());
+}