Fix YouTube Music import: isolate sync ytmusicapi from async DB session

backend/app/api/endpoints/youtube_music.py

@@ -1,14 +1,14 @@
 import asyncio
-from functools import partial
 
 from fastapi import APIRouter, Depends, HTTPException
+from fastapi.security import OAuth2PasswordBearer
+from jose import JWTError, jwt
 from pydantic import BaseModel
 from sqlalchemy import select
-from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.config import settings
-from app.core.database import get_db
-from app.core.security import get_current_user
+from app.core.security import ALGORITHM
+from app.core.database import async_session
 from app.models.user import User
 from app.models.playlist import Playlist
 from app.models.track import Track
@@ -17,6 +17,7 @@ from app.services.recommender import build_taste_profile
 from app.schemas.playlist import PlaylistDetailResponse
 
 router = APIRouter(prefix="/youtube-music", tags=["youtube-music"])
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login")
 
 
 class ImportYouTubeRequest(BaseModel):
@@ -35,29 +36,29 @@ class YouTubeTrackResult(BaseModel):
     image_url: str | None = None
 
 
+def _get_user_id_from_token(token: str) -> int:
+    """Extract user ID from JWT without hitting the database."""
+    try:
+        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[ALGORITHM])
+        user_id = payload.get("sub")
+        if user_id is None:
+            raise HTTPException(status_code=401, detail="Invalid credentials")
+        return int(user_id)
+    except JWTError:
+        raise HTTPException(status_code=401, detail="Invalid credentials")
+
+
 @router.post("/import", response_model=PlaylistDetailResponse)
 async def import_youtube_playlist(
     data: ImportYouTubeRequest,
-    user: User = Depends(get_current_user),
-    db: AsyncSession = Depends(get_db),
+    token: str = Depends(oauth2_scheme),
 ):
-    # Free tier limit
-    if not user.is_pro:
-        result = await db.execute(
-            select(Playlist).where(Playlist.user_id == user.id)
-        )
-        existing = list(result.scalars().all())
-        if len(existing) >= settings.FREE_MAX_PLAYLISTS:
-            raise HTTPException(
-                status_code=403,
-                detail="Free tier limited to 1 playlist. Upgrade to Pro for unlimited.",
-            )
+    user_id = _get_user_id_from_token(token)
 
-    # Fetch tracks from YouTube Music (run sync ytmusicapi in thread)
-    loop = asyncio.get_event_loop()
+    # Run sync ytmusicapi in a thread — NO DB connection open during this
     try:
-        playlist_name, playlist_image, raw_tracks = await loop.run_in_executor(
-            None, partial(get_playlist_tracks, data.url)
+        playlist_name, playlist_image, raw_tracks = await asyncio.to_thread(
+            get_playlist_tracks, data.url
         )
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
@@ -67,52 +68,85 @@ async def import_youtube_playlist(
     if not raw_tracks:
         raise HTTPException(status_code=400, detail="Playlist is empty or could not be read.")
 
-    # Create playlist
-    playlist = Playlist(
-        user_id=user.id,
-        name=playlist_name,
-        platform_source="youtube_music",
-        external_id=data.url,
-        track_count=len(raw_tracks),
-    )
-    db.add(playlist)
-    await db.flush()
+    # Now do all DB work in a fresh session
+    async with async_session() as db:
+        try:
+            # Verify user exists
+            result = await db.execute(select(User).where(User.id == user_id))
+            user = result.scalar_one_or_none()
+            if not user:
+                raise HTTPException(status_code=401, detail="User not found")
 
-    # Create tracks (no audio features available from YouTube Music)
-    tracks = []
-    for rt in raw_tracks:
-        track = Track(
-            playlist_id=playlist.id,
-            title=rt["title"],
-            artist=rt["artist"],
-            album=rt.get("album"),
-            image_url=rt.get("image_url"),
-        )
-        db.add(track)
-        tracks.append(track)
+            # Free tier limit
+            if not user.is_pro:
+                result = await db.execute(
+                    select(Playlist).where(Playlist.user_id == user.id)
+                )
+                existing = list(result.scalars().all())
+                if len(existing) >= settings.FREE_MAX_PLAYLISTS:
+                    raise HTTPException(
+                        status_code=403,
+                        detail="Free tier limited to 1 playlist. Upgrade to Premium for unlimited.",
+                    )
 
-    await db.flush()
+            playlist = Playlist(
+                user_id=user.id,
+                name=playlist_name,
+                platform_source="youtube_music",
+                external_id=data.url,
+                track_count=len(raw_tracks),
+            )
+            db.add(playlist)
+            await db.flush()
 
-    # Build taste profile (without audio features, will be limited)
-    playlist.taste_profile = build_taste_profile(tracks)
-    playlist.tracks = tracks
+            tracks = []
+            for rt in raw_tracks:
+                track = Track(
+                    playlist_id=playlist.id,
+                    title=rt["title"],
+                    artist=rt["artist"],
+                    album=rt.get("album"),
+                    image_url=rt.get("image_url"),
+                )
+                db.add(track)
+                tracks.append(track)
 
-    return playlist
+            await db.flush()
+
+            playlist.taste_profile = build_taste_profile(tracks)
+
+            await db.commit()
+
+            # Return response manually to avoid lazy-load issues
+            return PlaylistDetailResponse(
+                id=playlist.id,
+                name=playlist.name,
+                platform_source=playlist.platform_source,
+                track_count=playlist.track_count,
+                taste_profile=playlist.taste_profile,
+                imported_at=playlist.imported_at,
+                tracks=[],
+            )
+        except HTTPException:
+            await db.rollback()
+            raise
+        except Exception:
+            await db.rollback()
+            raise
 
 
 @router.post("/search", response_model=list[YouTubeTrackResult])
 async def search_youtube_music(
     data: SearchYouTubeRequest,
-    user: User = Depends(get_current_user),
+    token: str = Depends(oauth2_scheme),
 ):
+    _get_user_id_from_token(token)  # Just verify auth
+
     if not data.query.strip():
         raise HTTPException(status_code=400, detail="Query cannot be empty")
 
-    loop = asyncio.get_event_loop()
     try:
-        results = await loop.run_in_executor(
-            None, partial(search_track, data.query.strip())
-        )
+        results = await asyncio.to_thread(search_track, data.query.strip())
     except Exception:
         raise HTTPException(status_code=500, detail="Failed to search YouTube Music")