refactor: 推进后端分层架构治理

app/application/subscription/identity.py

@@ -0,0 +1,98 @@
+"""按媒体身份批量删除订阅的应用用例。"""
+
+from typing import Callable, Protocol
+
+from app.application.subscription.delete import (
+    AsyncUnitOfWork,
+    SubscribeDeletedPublisher,
+    SubscribeDeletionActor,
+    SubscribeDeletionCandidate,
+)
+from app.schemas.types import MediaSource
+
+
+class SubscribeIdentityDeletionRepository(Protocol):
+    """按媒体身份删除订阅所需的数据访问端口。"""
+
+    async def list_candidates_by_identity(
+        self,
+        media_source: MediaSource,
+        media_id: str,
+        season: int | None,
+        music_type: str | None,
+    ) -> list[SubscribeDeletionCandidate]:
+        """读取匹配媒体身份的去重订阅快照。"""
+        ...
+
+    async def delete(self, subscribe_id: int) -> None:
+        """把指定订阅登记为待删除。"""
+        ...
+
+
+SubscribeDeletionEventErrorHandler = Callable[[int, Exception], None]
+
+
+class DeleteSubscriptionsByIdentityCommand:
+    """按媒体身份删除当前用户可访问的全部订阅。"""
+
+    def __init__(
+        self,
+        repository: SubscribeIdentityDeletionRepository,
+        unit_of_work: AsyncUnitOfWork,
+        publish_deleted: SubscribeDeletedPublisher,
+        handle_event_error: SubscribeDeletionEventErrorHandler,
+    ) -> None:
+        """注入数据访问、事务、事件和事件错误处理端口。"""
+        self._repository = repository
+        self._unit_of_work = unit_of_work
+        self._publish_deleted = publish_deleted
+        self._handle_event_error = handle_event_error
+
+    async def execute(
+        self,
+        media_source: MediaSource,
+        media_id: str,
+        season: int | None,
+        music_type: str | None,
+        actor: SubscribeDeletionActor,
+    ) -> int:
+        """删除匹配订阅，并在提交后逐条发送兼容事件。"""
+        candidates = await self._repository.list_candidates_by_identity(
+            media_source,
+            media_id,
+            season,
+            music_type,
+        )
+        deletions = [
+            candidate
+            for candidate in candidates
+            if self._can_delete(candidate, actor)
+        ]
+        for candidate in deletions:
+            await self._repository.stage_delete(candidate.subscribe_id)
+
+        try:
+            await self._unit_of_work.commit()
+        except Exception:
+            await self._unit_of_work.rollback()
+            raise
+
+        for candidate in deletions:
+            try:
+                await self._publish_deleted(
+                    candidate.subscribe_id,
+                    dict(candidate.event_payload),
+                )
+            except Exception as error:
+                self._handle_event_error(candidate.subscribe_id, error)
+        return len(deletions)
+
+    @staticmethod
+    def _can_delete(
+        candidate: SubscribeDeletionCandidate,
+        actor: SubscribeDeletionActor,
+    ) -> bool:
+        """判断用户是否拥有候选订阅的删除权限。"""
+        if actor.is_superuser:
+            return True
+        return bool(candidate.username) and candidate.username == actor.username