From 47668285559eb6002e22f3cca497ff0f543ed166 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Bombeck?= <mbombeck@gmail.com>
Date: Sat, 8 Aug 2026 23:54:44 +0200
Subject: [PATCH] fix(reminders): keep a maximum-interval rolling reminder's
 next due after satisfy
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A rolling reminder at the engine's ten-year maximum interval lost its next
due date the moment its cadence was satisfied. The rolling branch of
nextOccurrenceAfter bounded its search by the 10-year anti-spin hardCap, and
a satisfied reminder computes its next slot with after === lastSatisfiedAt,
so the single deterministic slot lands exactly after + 3650 days — equal to
the hardCap to the millisecond. The notify-hour slot then spilled a few hours
past the raw boundary and was clipped to nothing, leaving nextDueAt null.

The rolling slot is one deterministic instant, not an open-ended walk, so the
anti-spin cap must never gate it. Bound the rolling search by that slot's own
day instead; endsOn stays enforced inside expandRolling, so a course-window
reminder still self-expires.

This surfaced on a ten-year tetanus booster: logging the next dose silently
dropped the reminder instead of rolling it forward a decade.
---
 .../__tests__/scheduling.test.ts              | 26 +++++++++++++++++++
 src/lib/medications/scheduling/recurrence.ts  | 19 +++++++++++++-
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/lib/measurement-reminders/__tests__/scheduling.test.ts b/src/lib/measurement-reminders/__tests__/scheduling.test.ts
index c775f4520..78c85990f 100644
--- a/src/lib/measurement-reminders/__tests__/scheduling.test.ts
+++ b/src/lib/measurement-reminders/__tests__/scheduling.test.ts
@@ -128,6 +128,32 @@ describe("computeReminderNextDueAt", () => {
     // 19:00 Berlin == 17:00Z (DST).
     expect(evening!.toISOString()).toBe("2026-06-10T17:00:00.000Z");
   });
+
+  // A ten-year booster (tetanus, FSME, …) uses the engine's maximum rolling
+  // interval — 3650 days. When such a reminder is satisfied, the satisfy path
+  // computes the next due with `after === lastSatisfiedAt`, so the single
+  // rolling slot lands exactly `intervalDays` out — right on the engine's
+  // ten-year forward search horizon. The boundary slot must still be found;
+  // a decade booster whose next dose is logged must roll forward, not vanish.
+  it("rolling at the maximum interval (3650 days) still re-anchors on satisfy", () => {
+    // Mirrors `satisfyReminder`: lastSatisfiedAt and `after` are the same
+    // instant (the dose's day-granular occurredAt, at day start).
+    const satisfiedAt = new Date("2026-08-08T00:00:00Z");
+    const reminder = base({
+      intervalDays: 3650,
+      // Anchor from the original 2016 dose + interval — irrelevant once
+      // satisfied, but this is what the mint wrote.
+      anchorDate: new Date("2026-03-13T00:00:00Z"),
+      lastSatisfiedAt: satisfiedAt,
+      notifyHour: 9,
+      createdAt: new Date("2026-08-08T00:00:00Z"),
+    });
+    const due = computeReminderNextDueAt(reminder, TZ, satisfiedAt);
+    expect(due).not.toBeNull();
+    // 3650 days after 2026-08-08 → 2036-08-05, slot at 09:00 Berlin (07:00Z).
+    expect(due!.getUTCFullYear()).toBe(2036);
+    expect(due!.getTime()).toBeGreaterThan(satisfiedAt.getTime());
+  });
 });
 
 describe("byHourTimesOfDay", () => {
diff --git a/src/lib/medications/scheduling/recurrence.ts b/src/lib/medications/scheduling/recurrence.ts
index f8735213d..b83bf0b63 100644
--- a/src/lib/medications/scheduling/recurrence.ts
+++ b/src/lib/medications/scheduling/recurrence.ts
@@ -316,7 +316,24 @@ export function nextOccurrenceAfter(
     const floor = new Date(
       Math.min(dayFloor.getTime(), rollingDoseDayFloor(schedule, ctx)),
     );
-    const slots = expandRolling(schedule, ctx, floor, limit);
+    // The rolling slot is a single deterministic instant — `lastIntakeAt + N`
+    // (or the anchor) — not an open-ended walk, so the 10-year anti-spin
+    // `hardCap` must never gate it. It collides at the fencepost: a reminder at
+    // the maximum ten-year rolling interval, satisfied so that `after ===
+    // lastIntakeAt`, produces a next slot exactly `after + 3650 days` — equal
+    // to `hardCap` to the millisecond, so the notify-hour slot spills a few
+    // hours past the raw boundary and `expandRolling` clips it to nothing
+    // (a ten-year booster silently lost its next due on the very dose that
+    // should re-anchor it). Bound the search by the deterministic slot's own
+    // day instead; `endsOn` stays enforced inside `expandRolling`, so a
+    // course-window reminder still self-expires.
+    const rollingCeil = new Date(
+      Math.max(
+        limit.getTime(),
+        endOfUtcDay(rollingDoseAnchor(schedule, ctx)).getTime(),
+      ),
+    );
+    const slots = expandRolling(schedule, ctx, floor, rollingCeil);
     for (const s of slots) {
       if (s.at.getTime() < floor.getTime()) continue;
       if (cyclic && !isInCyclicOnWeek(s.at, schedule, ctx)) continue;