backend/app/db.py

"""SQLAlchemy engine and session setup for the local SQLite database."""
from __future__ import annotations

from collections.abc import Iterator

from sqlalchemy import create_engine
from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker

from .config import settings

# check_same_thread=False lets the SQLite connection be used across the
# threadpool that FastAPI/uvicorn uses for sync endpoints.
engine = create_engine(
    settings.DATABASE_URL,
    connect_args={"check_same_thread": False},
    future=True,
)
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)


class Base(DeclarativeBase):
    """Declarative base for all ORM models."""


def init_db() -> None:
    """Create tables if they do not already exist."""
    from . import models  # noqa: F401  -- ensure models are imported/registered

    Base.metadata.create_all(bind=engine)


def get_db() -> Iterator[Session]:
    """FastAPI dependency: yield a DB session and always close it."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()