"""Async SQLAlchemy engine + session factory (mirrors qscore-service/app/db/session.py).

Lazily built so the service boots even when no DB is configured — `engine()` returns None then,
and every caller treats that as "persistence off".
"""
from __future__ import annotations

import logging
from functools import lru_cache

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

from app.config import get_settings

logger = logging.getLogger(__name__)


@lru_cache
def _engine_and_factory():
    s = get_settings()
    if not s.DATABASE_URL:
        return None, None
    eng = create_async_engine(s.DATABASE_URL, pool_pre_ping=True, pool_size=5, max_overflow=10)
    factory = async_sessionmaker(eng, class_=AsyncSession, expire_on_commit=False)
    return eng, factory


def engine():
    return _engine_and_factory()[0]


def session_factory():
    return _engine_and_factory()[1]


def db_enabled() -> bool:
    return engine() is not None