refactor(beatmap,beatmapset): use to ensure beatmap exists

app/database/beatmapset.py

@@ -13,6 +13,8 @@ from sqlmodel import Field, Relationship, SQLModel, col, func, select
 from sqlmodel.ext.asyncio.session import AsyncSession
 
 if TYPE_CHECKING:
+    from app.fetcher import Fetcher
+
     from .beatmap import Beatmap, BeatmapResp
     from .favourite_beatmapset import FavouriteBeatmapset
 
@@ -185,6 +187,16 @@ class Beatmapset(AsyncAttrs, BeatmapsetBase, table=True):
         await Beatmap.from_resp_batch(session, resp.beatmaps, from_=from_)
         return beatmapset
 
+    @classmethod
+    async def get_or_fetch(
+        cls, session: AsyncSession, fetcher: "Fetcher", sid: int
+    ) -> "Beatmapset":
+        beatmapset = await session.get(Beatmapset, sid)
+        if not beatmapset:
+            resp = await fetcher.get_beatmapset(sid)
+            beatmapset = await cls.from_resp(session, resp)
+        return beatmapset
+
 
 class BeatmapsetResp(BeatmapsetBase):
     id: int