fix: recurrence ghost exactness and calendar dedup

backend/mvp.py

@@ -122,18 +122,22 @@ def occurrences(rule: str, starts: datetime, start: datetime, end: datetime, cut
 
 
 def is_occurrence(rule: str, starts: datetime, at: datetime) -> bool:
-    """Return True when `at` is an occurrence this rule actually generates."""
+    """Return True when `at` is the exact timestamp of an occurrence this rule generates."""
     parts = parse_rrule(rule)
     interval = int(parts.get("INTERVAL", 1))
     if starts.tzinfo is None:
         starts = starts.replace(tzinfo=UTC)
+    else:
+        starts = starts.astimezone(UTC)
     if at.tzinfo is None:
         at = at.replace(tzinfo=UTC)
+    else:
+        at = at.astimezone(UTC)
     if at < starts:
         return False
     if "UNTIL" in parts:
         until = datetime.fromisoformat(parts["UNTIL"])
-        until = until.replace(tzinfo=UTC) if until.tzinfo is None else until
+        until = until.replace(tzinfo=UTC) if until.tzinfo is None else until.astimezone(UTC)
         if at > until:
             return False
     if "COUNT" in parts:
@@ -165,19 +169,11 @@ def is_occurrence(rule: str, starts: datetime, at: datetime) -> bool:
             guard += 1
             cursor += timedelta(days=1)
         return False
-    if parts["FREQ"] == "DAILY":
-        return (at.date() - starts.date()).days % interval == 0
-    if parts["FREQ"] == "WEEKLY":
-        days = {_WEEKDAYS[x] for x in parts.get("BYDAY", list(_WEEKDAYS)[starts.weekday()]).split(",")}
-        return at.weekday() in days and ((at.date() - starts.date()).days // 7) % interval == 0
-    if parts["FREQ"] == "MONTHLY":
-        month_delta = (at.year - starts.year) * 12 + at.month - starts.month
-        month_days = {int(x) for x in parts.get("BYMONTHDAY", str(starts.day)).split(",")}
-        return month_delta % interval == 0 and at.day in month_days
-    years = at.year - starts.year
-    months = {int(x) for x in parts.get("BYMONTH", str(starts.month)).split(",")}
-    month_days = {int(x) for x in parts.get("BYMONTHDAY", str(starts.day)).split(",")}
-    return years % interval == 0 and at.month in months and at.day in month_days
+    # Exact-match validation via the same canonical day generator used for
+    # rendering, so time-of-day is preserved and nothing outside the rule is
+    # accepted as a valid occurrence.
+    candidates = occurrences(rule, starts, starts, at, None)
+    return at in candidates
 
 
 def is_occurrence_utc(rule: str, starts: datetime, at: datetime) -> bool:
@@ -202,6 +198,11 @@ def ensure_real_occurrence(template: RecurrenceTemplate, occurrence_at: datetime
     """Reject occurrence_at values that are not valid occurrences of this recurrence rule."""
     if not is_occurrence(template.rrule, template.starts_at, occurrence_at):
         raise HTTPException(422, "occurrence_at 不是该重复规则的有效发生时刻")
+    if template.ends_at:
+        at = occurrence_at.replace(tzinfo=UTC) if occurrence_at.tzinfo is None else occurrence_at.astimezone(UTC)
+        ends = template.ends_at.replace(tzinfo=UTC) if template.ends_at.tzinfo is None else template.ends_at.astimezone(UTC)
+        if at > ends:
+            raise HTTPException(422, "occurrence_at 晚于该重复规则的有效截止时间")
 
 
 @router.post("/recurrences", status_code=201)
@@ -219,26 +220,35 @@ async def create_recurrence(payload: RecurrenceCreate, user: User = Depends(curr
 
 
 @router.get("/calendar")
-async def calendar(start: date, end: date, timezone: str = Query(default="UTC", pattern=r"^[A-Za-z_+-]+(/[A-Za-z_+-]+)*$"), user: User = Depends(current_user), db: AsyncSession = Depends(get_db)):
+async def calendar(start: date, end: date, timezone: str = Query(default="UTC", pattern=r"^[A-Za-z0-9_+\-]+(/[A-Za-z0-9_+\-]+)*$"), timezone_offset: int | None = Query(default=None, ge=-840, le=840), user: User = Depends(current_user), db: AsyncSession = Depends(get_db)):
     if end < start or (end - start).days > 366:
         raise HTTPException(422, "日期范围无效或超过一年")
     try:
         zone = ZoneInfo(timezone)
     except ZoneInfoNotFoundError:
         raise HTTPException(422, "未知时区")
-    start_dt = datetime.combine(start, time.min, tzinfo=zone).astimezone(UTC)
-    end_dt = (datetime.combine(end + timedelta(days=1), time.min, tzinfo=zone)).astimezone(UTC) - timedelta(microseconds=1)
+    if timezone_offset is not None and timezone == "UTC":
+        # Legacy clients pass an offset instead of an IANA name.
+        zone = ZoneInfo("UTC")
+        start_dt = datetime.combine(start, time.min, tzinfo=UTC) - timedelta(minutes=timezone_offset)
+        end_dt = datetime.combine(end + timedelta(days=1), time.min, tzinfo=UTC) - timedelta(minutes=timezone_offset) - timedelta(microseconds=1)
+    else:
+        start_dt = datetime.combine(start, time.min, tzinfo=zone).astimezone(UTC)
+        end_dt = datetime.combine(end + timedelta(days=1), time.min, tzinfo=zone).astimezone(UTC) - timedelta(microseconds=1)
+
+    def as_utc(value: datetime) -> datetime:
+        if value.tzinfo is None:
+            return value.replace(tzinfo=UTC)
+        return value.astimezone(UTC)
+
     recurrence_rows = (await db.execute(select(RecurrenceTemplate, Task).join(Task).where(RecurrenceTemplate.user_id == user.id, Task.deleted_at.is_(None)))).all()
     template_ids = [template.id for template, _ in recurrence_rows]
     exception_rows = [] if not template_ids else list((await db.scalars(select(RecurrenceException).where(RecurrenceException.template_id.in_(template_ids)))).all())
     exceptions_by_template = {}
     for exception in exception_rows:
-        key = exception.occurrence_at.replace(tzinfo=UTC) if exception.occurrence_at.tzinfo is None else exception.occurrence_at
+        key = as_utc(exception.occurrence_at)
         exceptions_by_template.setdefault(exception.template_id, {})[key] = exception
 
-    def as_utc(value: datetime) -> datetime:
-        return value.replace(tzinfo=UTC) if value.tzinfo is None else value
-
     recurring_task_ids = {task.id for _, task in recurrence_rows}
     normal_query = select(Task).where(
         Task.user_id == user.id,
@@ -260,11 +270,17 @@ async def calendar(start: date, end: date, timezone: str = Query(default="UTC",
         "completed": task.completed,
         "version": task.version,
     } for task in normal_tasks]
+    emitted = set()
     for template, task in recurrence_rows:
         exceptions = exceptions_by_template.get(template.id, {})
-        # Render events that this recurrence generates: real occurrences
-        # whose displayed (possibly moved) due_at falls inside the window.
-        for at in occurrences(template.rrule, template.starts_at, template.starts_at, end_dt, template.ends_at):
+        # Canonical series from the template's true start so every exception
+        # whose occurrence is real and inside this series is considered.
+        series_start = template.starts_at
+        if exceptions:
+            first_exception = min(as_utc(at) for at in exceptions)
+            series_start = min(as_utc(series_start), first_exception)
+        generated = occurrences(template.rrule, template.starts_at, as_utc(series_start), end_dt, template.ends_at)
+        for at in generated:
             exception = exceptions.get(as_utc(at))
             if exception and exception.deleted:
                 continue
@@ -272,14 +288,22 @@ async def calendar(start: date, end: date, timezone: str = Query(default="UTC",
             if due_at < start_dt or due_at > end_dt:
                 continue
             output.append({"recurrence_id": template.id, "task_id": task.id, "occurrence_at": at, "title": exception.title if exception and exception.title else task.title, "due_at": due_at, "completed": bool(exception and exception.completed)})
-        # Occurrences moved far enough that their original slot falls before
-        # the start of generation: show them at their moved due_at. Ghost
-        # occurrence_at values are already rejected at write time.
+            emitted.add(as_utc(at))
+        # Fall back for stored exceptions whose original slot is real but which
+        # the canonical generation skipped only because their original date is
+        # outside the requested window (e.g. moved backwards across the month).
         for occurrence_at, exception in exceptions.items():
             if exception.deleted or exception.due_at is None:
                 continue
-            if as_utc(occurrence_at) >= as_utc(template.starts_at) and start_dt <= as_utc(exception.due_at) <= end_dt:
-                output.append({"recurrence_id": template.id, "task_id": task.id, "occurrence_at": occurrence_at, "title": exception.title or task.title, "due_at": as_utc(exception.due_at), "completed": bool(exception.completed)})
+            if occurrence_at in emitted:
+                continue
+            if not is_occurrence(template.rrule, template.starts_at, occurrence_at):
+                continue
+            if template.ends_at and occurrence_at > as_utc(template.ends_at):
+                continue
+            due_at = as_utc(exception.due_at)
+            if start_dt <= due_at <= end_dt:
+                output.append({"recurrence_id": template.id, "task_id": task.id, "occurrence_at": occurrence_at, "title": exception.title or task.title, "due_at": due_at, "completed": bool(exception.completed)})
     return sorted(output, key=lambda item: item["occurrence_at"].replace(tzinfo=UTC) if item["occurrence_at"].tzinfo is None else item["occurrence_at"])