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

DATA_DIR = Path(__file__).resolve().parent.parent.parent / "data"
DATA_DIR.mkdir(exist_ok=True)
DB_PATH = DATA_DIR / "planner.db"

engine = create_engine(f"sqlite:///{DB_PATH}", echo=False)
SessionLocal = sessionmaker(bind=engine, class_=Session, expire_on_commit=False)


class Base(DeclarativeBase):
    pass


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


def switch_database(db_path: Path):
    """Hot-swap the active database engine and session factory."""
    global engine, SessionLocal, DB_PATH
    DB_PATH = db_path
    engine.dispose()
    engine = create_engine(f"sqlite:///{db_path}", echo=False)
    SessionLocal = sessionmaker(bind=engine, class_=Session, expire_on_commit=False)
    Base.metadata.create_all(bind=engine)
    return engine