refactor(database): use a new 'On-Demand' design (#86)

Technical Details: https://blog.mxgame.top/2025/11/22/An-On-Demand-Design-Within-SQLModel/

app/database/playlists.py

@@ -1,11 +1,11 @@
 from datetime import datetime
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any, NotRequired, TypedDict
 
-from app.models.model import UTCBaseModel
 from app.models.mods import APIMod
 from app.models.playlist import PlaylistItem
 
-from .beatmap import Beatmap, BeatmapResp
+from ._base import DatabaseModel, ondemand
+from .beatmap import Beatmap, BeatmapDict, BeatmapModel
 
 from sqlmodel import (
     JSON,
@@ -15,7 +15,6 @@ from sqlmodel import (
     Field,
     ForeignKey,
     Relationship,
-    SQLModel,
     func,
     select,
 )
@@ -23,18 +22,34 @@ from sqlmodel.ext.asyncio.session import AsyncSession
 
 if TYPE_CHECKING:
     from .room import Room
+    from .score import ScoreDict
 
 
-class PlaylistBase(SQLModel, UTCBaseModel):
-    id: int = Field(index=True)
-    owner_id: int = Field(sa_column=Column(BigInteger, ForeignKey("lazer_users.id")))
+class PlaylistDict(TypedDict):
+    id: int
+    room_id: int
+    beatmap_id: int
+    created_at: datetime | None
     ruleset_id: int
-    expired: bool = Field(default=False)
-    playlist_order: int = Field(default=0)
-    played_at: datetime | None = Field(
-        sa_column=Column(DateTime(timezone=True)),
-        default=None,
+    allowed_mods: list[APIMod]
+    required_mods: list[APIMod]
+    freestyle: bool
+    expired: bool
+    owner_id: int
+    playlist_order: int
+    played_at: datetime | None
+    beatmap: NotRequired["BeatmapDict"]
+    scores: NotRequired[list[dict[str, Any]]]
+
+
+class PlaylistModel(DatabaseModel[PlaylistDict]):
+    id: int = Field(index=True)
+    room_id: int = Field(foreign_key="rooms.id")
+    beatmap_id: int = Field(
+        foreign_key="beatmaps.id",
     )
+    created_at: datetime | None = Field(default=None, sa_column_kwargs={"server_default": func.now()})
+    ruleset_id: int
     allowed_mods: list[APIMod] = Field(
         default_factory=list,
         sa_column=Column(JSON),
@@ -43,16 +58,46 @@ class PlaylistBase(SQLModel, UTCBaseModel):
         default_factory=list,
         sa_column=Column(JSON),
     )
-    beatmap_id: int = Field(
-        foreign_key="beatmaps.id",
-    )
     freestyle: bool = Field(default=False)
+    expired: bool = Field(default=False)
+    owner_id: int = Field(sa_column=Column(BigInteger, ForeignKey("lazer_users.id")))
+    playlist_order: int = Field(default=0)
+    played_at: datetime | None = Field(
+        sa_column=Column(DateTime(timezone=True)),
+        default=None,
+    )
+
+    @ondemand
+    @staticmethod
+    async def beatmap(_session: AsyncSession, playlist: "Playlist", includes: list[str] | None = None) -> BeatmapDict:
+        return await BeatmapModel.transform(playlist.beatmap, includes=includes)
+
+    @ondemand
+    @staticmethod
+    async def scores(session: AsyncSession, playlist: "Playlist") -> list["ScoreDict"]:
+        from .score import Score, ScoreModel
+
+        scores = (
+            await session.exec(
+                select(Score).where(
+                    Score.playlist_item_id == playlist.id,
+                    Score.room_id == playlist.room_id,
+                )
+            )
+        ).all()
+        result: list[ScoreDict] = []
+        for score in scores:
+            result.append(
+                await ScoreModel.transform(
+                    score,
+                )
+            )
+        return result
 
 
-class Playlist(PlaylistBase, table=True):
+class Playlist(PlaylistModel, table=True):
     __tablename__: str = "room_playlists"
     db_id: int = Field(default=None, primary_key=True, index=True, exclude=True)
-    room_id: int = Field(foreign_key="rooms.id", exclude=True)
 
     beatmap: Beatmap = Relationship(
         sa_relationship_kwargs={
@@ -60,7 +105,6 @@ class Playlist(PlaylistBase, table=True):
         }
     )
     room: "Room" = Relationship()
-    created_at: datetime | None = Field(default=None, sa_column_kwargs={"server_default": func.now()})
     updated_at: datetime | None = Field(
         default=None, sa_column_kwargs={"server_default": func.now(), "onupdate": func.now()}
     )
@@ -121,15 +165,3 @@ class Playlist(PlaylistBase, table=True):
             raise ValueError("Playlist item not found")
         await session.delete(db_playlist)
         await session.commit()
-
-
-class PlaylistResp(PlaylistBase):
-    beatmap: BeatmapResp | None = None
-
-    @classmethod
-    async def from_db(cls, playlist: Playlist, include: list[str] = []) -> "PlaylistResp":
-        data = playlist.model_dump()
-        if "beatmap" in include:
-            data["beatmap"] = await BeatmapResp.from_db(playlist.beatmap)
-        resp = cls.model_validate(data)
-        return resp