from __future__ import annotations

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

from app.config import Settings


class Base(DeclarativeBase):
    pass


_engine: AsyncEngine | None = None
_session_factory: async_sessionmaker[AsyncSession] | None = None


def init_db(settings: Settings) -> None:
    global _engine, _session_factory
    if _engine is not None and _session_factory is not None:
        return

    _engine = create_async_engine(
        settings.pg_dsn,
        pool_pre_ping=True,
        pool_size=20,
        max_overflow=40,
    )
    _session_factory = async_sessionmaker(_engine, expire_on_commit=False)


def get_engine() -> AsyncEngine:
    if _engine is None:
        raise RuntimeError("Database engine has not been initialized.")
    return _engine


def get_session_factory() -> async_sessionmaker[AsyncSession]:
    if _session_factory is None:
        raise RuntimeError("Database session factory has not been initialized.")
    return _session_factory


async def close_db() -> None:
    global _engine, _session_factory
    if _engine is not None:
        await _engine.dispose()
    _engine = None
    _session_factory = None