"""
FastAPI dependency that yields an async SQLAlchemy session per request.

Usage in route handlers:
    from deps.db import get_db
    from sqlalchemy.ext.asyncio import AsyncSession
    from fastapi import Depends

    @router.get("/items")
    async def list_items(session: AsyncSession = Depends(get_db)):
        ...
"""
from typing import AsyncGenerator

from sqlalchemy.ext.asyncio import AsyncSession

from db.session import AsyncSessionLocal


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """Yield a per-request AsyncSession; close it when the request is done."""
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()