import sqlite3

from sqlalchemy import create_engine, event
from sqlalchemy.engine import Engine
from sqlalchemy.orm import sessionmaker, declarative_base
import os

os.makedirs("data", exist_ok=True)

_DATABASE_URL = os.environ.get("DATABASE_URL", "sqlite:///./data/topology.db")

engine = create_engine(
    _DATABASE_URL,
    connect_args={"check_same_thread": False}
)


@event.listens_for(Engine, "connect")
def _set_sqlite_pragma(dbapi_conn, _record):
    if isinstance(dbapi_conn, sqlite3.Connection):
        cursor = dbapi_conn.cursor()
        cursor.execute("PRAGMA foreign_keys=ON")
        cursor.close()


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


def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()