import os
import threading
from contextlib import asynccontextmanager

from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine


class DatabaseConfig:
    _thread_local = threading.local()

    @classmethod
    def get_engine(cls):
        if not hasattr(cls._thread_local, "engine"):
            cls._thread_local.engine = create_async_engine(
                url=os.getenv("SQLALCHEMY_DATABASE_URI"),
                pool_pre_ping=True,
                pool_recycle=3600,
            )
        return cls._thread_local.engine

    @classmethod
    def _get_session_factory(cls):
        if not hasattr(cls._thread_local, "session_factory"):
            cls._thread_local.session_factory = async_sessionmaker(
                bind=cls.get_engine(),
                autoflush=False,
                autocommit=False,
                expire_on_commit=False,
            )
        return cls._thread_local.session_factory

    @classmethod
    @asynccontextmanager
    async def async_session(cls):
        session_factory = cls._get_session_factory()
        async with session_factory() as session:
            yield session