[verified] feat: support monthly completion recurrence

backend/recurrence_service.py

@@ -2,6 +2,7 @@ from datetime import UTC, datetime, time, timedelta
 from uuid import UUID
 from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
+from dateutil.relativedelta import relativedelta
 from fastapi import HTTPException
 from sqlalchemy import select, update
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -25,10 +26,15 @@ def _user_zone(user: User) -> ZoneInfo:
         raise HTTPException(422, "用户时区无效") from exc
 
 
-def _after_completion_due(task: Task, completed_at: datetime, days: int, user: User) -> datetime:
+def _after_completion_due(
+    task: Task, completed_at: datetime, value: int, unit: str | None, user: User
+) -> datetime:
     zone = _user_zone(user)
     completed_local = completed_at.astimezone(zone)
-    target_date = completed_local.date() + timedelta(days=days)
+    if unit == "months":
+        target_date = completed_local.date() + relativedelta(months=value)
+    else:
+        target_date = completed_local.date() + timedelta(days=value)
     if task.due_has_time:
         due_local = task.due_at.astimezone(zone)
         wall_time = due_local.timetz().replace(tzinfo=None)
@@ -67,7 +73,11 @@ async def apply_task_changes(
         if recurrence.trigger_mode == "after_completion":
             completed_at = utcnow()
             next_due = _after_completion_due(
-                task, completed_at, recurrence.after_completion_days, user
+                task,
+                completed_at,
+                recurrence.after_completion_days,
+                recurrence.after_completion_unit,
+                user,
             )
             changes["completed"] = False
             changes["due_at"] = next_due