"""SQLAlchemy engine, session factory, and a FastAPI dependency."""
from __future__ import annotations

from typing import Iterator

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

from app.config import get_settings

_settings = get_settings()

# check_same_thread is only meaningful for SQLite; harmless otherwise.
_connect_args = {"check_same_thread": False} if _settings.database_url.startswith("sqlite") else {}

engine = create_engine(_settings.database_url, connect_args=_connect_args, future=True)
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)
Base = declarative_base()


def init_db() -> None:
    """Create tables if they don't exist. Idempotent."""
    from app import models  # noqa: F401  (register models on Base)

    Base.metadata.create_all(bind=engine)


def get_db() -> Iterator[Session]:
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()