refactor(todo): 移除 due_at 字段，改用 order 字段管理象限内顺序

backend/src/v1/todo/service.py

@@ -13,7 +13,13 @@ from core.logging import get_logger
 from models.todos import Todo, TodoStatus
 from v1.schedule_items.repository import SQLAlchemyScheduleItemRepository
 from v1.todo.repository import TodoRepository
-from v1.todo.schemas import ScheduleItemBasic, TodoCreate, TodoResponse, TodoUpdate
+from v1.todo.schemas import (
+    ScheduleItemBasic,
+    TodoCreate,
+    TodoReorderRequest,
+    TodoResponse,
+    TodoUpdate,
+)
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncSession
@@ -52,12 +58,20 @@ class TodoService(BaseService):
         user_id = self.require_user_id()
 
         try:
+            order_value = request.order
+            if order_value is None:
+                todos_in_priority = await self._repository.list_by_owner(
+                    owner_id=user_id,
+                    priority=request.priority,
+                )
+                order_value = len(todos_in_priority)
+
             todo = await self._repository.create(
                 owner_id=user_id,
                 title=request.title,
                 description=request.description,
-                due_at=request.due_at,
                 priority=request.priority,
+                order=order_value,
                 created_by=user_id,
             )
 
@@ -144,8 +158,8 @@ class TodoService(BaseService):
                 todo,
                 title=request.title,
                 description=request.description,
-                due_at=request.due_at,
                 priority=request.priority,
+                order=request.order,
                 status=status_enum,
                 completed_at=completed_at,
             )
@@ -253,6 +267,53 @@ class TodoService(BaseService):
             },
         )
 
+    async def reorder(self, request: TodoReorderRequest) -> None:
+        user_id = self.require_user_id()
+
+        seen_ids: set[UUID] = set()
+        original_priorities: set[int] = set()
+        target_priorities: set[int] = set()
+
+        try:
+            for item in request.items:
+                if item.id in seen_ids:
+                    raise HTTPException(status_code=400, detail="Duplicate todo id")
+                seen_ids.add(item.id)
+
+                todo = await self._repository.get_by_id(item.id)
+                if todo is None:
+                    raise HTTPException(status_code=404, detail="Todo not found")
+                if todo.owner_id != user_id:
+                    raise HTTPException(
+                        status_code=403, detail="Not authorized to reorder this todo"
+                    )
+
+                original_priorities.add(todo.priority)
+                target_priorities.add(item.priority)
+
+                await self._repository.update(
+                    todo,
+                    priority=item.priority,
+                    order=item.order,
+                )
+
+            affected_priorities = original_priorities.union(target_priorities)
+            for priority in affected_priorities:
+                todos = await self._repository.list_by_owner(
+                    owner_id=user_id,
+                    status=TodoStatus.PENDING,
+                    priority=priority,
+                )
+                todos.sort(key=lambda current: (current.order, current.created_at))
+                for index, todo in enumerate(todos):
+                    if todo.order != index:
+                        await self._repository.update(todo, order=index)
+
+            await self._session.commit()
+        except SQLAlchemyError:
+            await self._session.rollback()
+            raise HTTPException(status_code=503, detail="Todo service unavailable")
+
     async def list_todos(
         self,
         status: str | None = None,
@@ -287,7 +348,7 @@ class TodoService(BaseService):
         )
 
         schedule_item_ids = await self._repository.get_schedule_items(todo.id)
-        schedule_items = []
+        schedule_items: list[ScheduleItemBasic] = []
         for item_id in schedule_item_ids:
             item = await self._schedule_item_repository.get_by_id(item_id)
             if item:
@@ -305,8 +366,8 @@ class TodoService(BaseService):
             owner_id=todo.owner_id,
             title=todo.title,
             description=todo.description,
-            due_at=todo.due_at,
             priority=todo.priority,
+            order=todo.order,
             status=status_value,
             completed_at=todo.completed_at,
             created_at=todo.created_at,