From 603588cc4fff3a07b2c998921042b64fb74cd584 Mon Sep 17 00:00:00 2001
From: altair823 <kimth0734@gmail.com>
Date: Sun, 26 Apr 2026 02:13:47 +0900
Subject: [PATCH] =?UTF-8?q?chore(backup):=20polish=20=E2=80=94=20boundary?=
 =?UTF-8?q?=20test,=20roundtrip=20lock-in,=20precompute=20today?=
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Code reviewer minor nitpicks:
- Add test for inkling-2026-02-30.sqlite (locks roundtrip-validation contract)
- Add test for weekly window inclusive at oldest boundary
- Precompute today=startOfDayUtc(now) once outside the loop, pass to helpers

No behavior change; tests added cover existing semantics.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 src/main/services/backupRotation.ts | 20 +++++++++-----------
 tests/unit/backupRotation.test.ts   | 14 ++++++++++++++
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/main/services/backupRotation.ts b/src/main/services/backupRotation.ts
index 49d485d..e6631b0 100644
--- a/src/main/services/backupRotation.ts
+++ b/src/main/services/backupRotation.ts
@@ -24,17 +24,15 @@ function startOfDayUtc(d: Date): Date {
   return x;
 }
 
-function isWithinDailyWindow(fileDate: Date, now: Date): boolean {
-  const today = startOfDayUtc(now);
+function isWithinDailyWindow(fileDate: Date, today: Date): boolean {
   const oldest = new Date(today.getTime() - (DAILY_WINDOW_DAYS - 1) * ONE_DAY_MS);
   return fileDate >= oldest && fileDate <= today;
 }
 
-function isWithinWeeklyWindow(fileDate: Date, now: Date): boolean {
+function isWithinWeeklyWindow(fileDate: Date, today: Date): boolean {
   // UTC-based Monday detection. UTCDay: 0=Sun, 1=Mon..6=Sat
   if (fileDate.getUTCDay() !== 1) return false;
-  const today = startOfDayUtc(now);
-  // Weekly window: anchor on the most recent Monday on/before `now`, then reach back
+  // Weekly window: anchor on the most recent Monday on/before `today`, then reach back
   // WEEKLY_WINDOW_PRIOR_MONDAYS * 7 days from that anchor. Effective semantic:
   // up to 5 distinct Mondays kept (the anchor Monday + 4 prior). The plan's commit
   // header says "4 weekly Mondays" but the plan's test case at
@@ -47,9 +45,8 @@ function isWithinWeeklyWindow(fileDate: Date, now: Date): boolean {
   return fileDate >= oldest && fileDate <= today;
 }
 
-function isWithinMonthlyWindow(fileDate: Date, now: Date): boolean {
+function isWithinMonthlyWindow(fileDate: Date, today: Date): boolean {
   if (fileDate.getUTCDate() !== 1) return false;
-  const today = startOfDayUtc(now);
   // months ago: difference in calendar months
   const monthsAgo =
     (today.getUTCFullYear() - fileDate.getUTCFullYear()) * 12 +
@@ -60,18 +57,19 @@ function isWithinMonthlyWindow(fileDate: Date, now: Date): boolean {
 export function applyGfsRetention(filenames: string[], now: Date): RetentionResult {
   const keep: string[] = [];
   const remove: string[] = [];
+  const today = startOfDayUtc(now);
   for (const name of filenames) {
     const iso = parseBackupFilename(name);
     if (iso === null) continue; // unrecognized — ignore (no-op)
     const fileDate = new Date(iso + 'T00:00:00Z');
-    if (fileDate > startOfDayUtc(now)) {
+    if (fileDate > today) {
       keep.push(name); // future-dated — clock skew safety
       continue;
     }
     const survives =
-      isWithinDailyWindow(fileDate, now) ||
-      isWithinWeeklyWindow(fileDate, now) ||
-      isWithinMonthlyWindow(fileDate, now);
+      isWithinDailyWindow(fileDate, today) ||
+      isWithinWeeklyWindow(fileDate, today) ||
+      isWithinMonthlyWindow(fileDate, today);
     if (survives) keep.push(name);
     else remove.push(name);
   }
diff --git a/tests/unit/backupRotation.test.ts b/tests/unit/backupRotation.test.ts
index d2fd98f..d981b6d 100644
--- a/tests/unit/backupRotation.test.ts
+++ b/tests/unit/backupRotation.test.ts
@@ -11,6 +11,12 @@ describe('parseBackupFilename', () => {
     expect(parseBackupFilename('inkling-2026-13-99.sqlite')).toBeNull();
     expect(parseBackupFilename('.last-snapshot')).toBeNull();
   });
+
+  it('returns null for date that JS would silently coerce (roundtrip lock-in)', () => {
+    // Without the toISOString roundtrip check, JS coerces 2026-02-30 to 2026-03-02.
+    // This test locks in the roundtrip-validation contract.
+    expect(parseBackupFilename('inkling-2026-02-30.sqlite')).toBeNull();
+  });
 });
 
 describe('applyGfsRetention', () => {
@@ -52,6 +58,14 @@ describe('applyGfsRetention', () => {
     expect(r.remove).toContain('inkling-2026-03-09.sqlite');
   });
 
+  it('weekly window is inclusive at oldest boundary', () => {
+    // 2026-03-23 is exactly 4*7 days before anchor Monday 2026-04-20.
+    // Locks in the boundary semantic explicitly.
+    const r = applyGfsRetention(names('2026-03-23', '2026-03-16'), NOW);
+    expect(r.keep).toContain('inkling-2026-03-23.sqlite');
+    expect(r.remove).toContain('inkling-2026-03-16.sqlite');
+  });
+
   it('keeps month-firsts within last 6 months', () => {
     // Last 6 month-firsts from 2026-04-26: 2026-04-01, 2026-03-01, 2026-02-01,
     // 2026-01-01, 2025-12-01, 2025-11-01