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


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


def get_database_url() -> str:
    """
    DATABASE_URL is configurable via env, default to local SQLite file.
    Example: sqlite:///./data/ops_core.db
    """
    return os.getenv("DATABASE_URL", "sqlite:///./data/ops_core.db")


DATABASE_URL = get_database_url()

# For SQLite, check_same_thread=False is required when used with FastAPI / threads.
engine = create_engine(
    DATABASE_URL,
    connect_args={"check_same_thread": False} if DATABASE_URL.startswith("sqlite") else {},
)

SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)


def get_db():
    """
    FastAPI dependency to provide a DB session.
    """
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()