# backend/app/db.py
"""SQLAlchemy engine, session factory i Base declarativa."""
from contextlib import contextmanager
from sqlalchemy import create_engine
from sqlalchemy.orm import DeclarativeBase, sessionmaker, Session
from typing import Generator


class Base(DeclarativeBase):
    pass


_engine = None
_SessionLocal = None


def init_db(database_url: str) -> None:
    global _engine, _SessionLocal
    connect_args = {"check_same_thread": False} if database_url.startswith("sqlite") else {}
    _engine = create_engine(database_url, connect_args=connect_args, echo=False)
    _SessionLocal = sessionmaker(bind=_engine, autocommit=False, autoflush=False)
    # Import models so that all ORM classes register with Base.metadata before create_all
    from .models import db_models as _  # noqa: F401
    Base.metadata.create_all(_engine)


@contextmanager
def get_session() -> Generator[Session, None, None]:
    """Context manager de sessió SQLAlchemy."""
    if _SessionLocal is None:
        raise RuntimeError("Database not initialized. Call init_db() first.")
    db = _SessionLocal()
    try:
        yield db
    except Exception:
        db.rollback()
        raise
    finally:
        db.close()