"""Engine + sessionmaker. Lazily initialised so test code can swap the URL."""

from __future__ import annotations

from collections.abc import Iterator
from contextlib import contextmanager

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import Session, sessionmaker

from app.core.config import settings

_engine: Engine | None = None
_SessionLocal: sessionmaker[Session] | None = None


def get_engine() -> Engine:
    global _engine
    if _engine is None:
        _engine = create_engine(
            settings.database_url,
            pool_pre_ping=True,
            future=True,
        )
    return _engine


def get_sessionmaker() -> sessionmaker[Session]:
    global _SessionLocal
    if _SessionLocal is None:
        _SessionLocal = sessionmaker(bind=get_engine(), expire_on_commit=False, future=True)
    return _SessionLocal


@contextmanager
def session_scope() -> Iterator[Session]:
    """Context manager that commits on success, rolls back on error."""
    s = get_sessionmaker()()
    try:
        yield s
        s.commit()
    except Exception:
        s.rollback()
        raise
    finally:
        s.close()