app/core/database/session_manager.py

import contextlib
from collections.abc import AsyncIterator

from sqlalchemy.ext.asyncio import (
    AsyncConnection,
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)
from sqlalchemy.orm import declarative_base

from app.core.config import settings

Base = declarative_base()

# Inspiration https://praciano.com.br/fastapi-and-async-sqlalchemy-20-with-pytest-done-right.html


class DatabaseSessionManager:
    def __init__(self):
        self._engine = create_async_engine(settings.SQLALCHEMY_DATABASE_URI)
        self._sessionmaker = async_sessionmaker(autocommit=False, bind=self._engine)

    async def close(self):
        if self._engine is None:
            raise Exception("DatabaseSessionManager is not initialized")
        await self._engine.dispose()

        self._engine = None
        self._sessionmaker = None

    @contextlib.asynccontextmanager
    async def connect(self) -> AsyncIterator[AsyncConnection]:
        if self._engine is None:
            raise Exception("DatabaseSessionManager is not initialized")

        async with self._engine.begin() as connection:
            try:
                yield connection
            except Exception:
                await connection.rollback()
                raise

    @contextlib.asynccontextmanager
    async def session(self) -> AsyncIterator[AsyncSession]:
        if self._sessionmaker is None:
            raise Exception("DatabaseSessionManager is not initialized")

        session = self._sessionmaker()
        try:
            yield session
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


sessionmanager = DatabaseSessionManager()


async def get_db_session():
    async with sessionmanager.session() as session:
        yield session