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

from app.core.config import settings


class Base(DeclarativeBase):
    pass


_engine = None
_session_factory = None


def get_engine():
    global _engine
    if _engine is None:
        _engine = create_async_engine(
            settings.DATABASE_URL,
            echo=settings.ENVIRONMENT == "development",
        )
    return _engine


async def get_db() -> AsyncSession:
    global _session_factory
    if _session_factory is None:
        _session_factory = async_sessionmaker(get_engine(), expire_on_commit=False)
    async with _session_factory() as session:
        yield session