from collections.abc import AsyncIterator
from typing import Annotated

from fastapi import Depends
from sqlalchemy.ext.asyncio import (
    AsyncEngine,
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)

from app.core.config import get_settings

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


def get_engine() -> AsyncEngine:
    global _engine, _session_factory
    if _engine is None:
        _engine = create_async_engine(str(get_settings().database_url), pool_pre_ping=True)
        _session_factory = async_sessionmaker(_engine, expire_on_commit=False)
    return _engine


async def get_session() -> AsyncIterator[AsyncSession]:
    get_engine()
    assert _session_factory is not None
    async with _session_factory() as session:
        yield session


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


SessionDep = Annotated[AsyncSession, Depends(get_session)]