"""
MongoDB Atlas connection using Motor (async driver).
"""
from motor.motor_asyncio import AsyncIOMotorClient
from config import settings

client: AsyncIOMotorClient | None = None


def get_client() -> AsyncIOMotorClient:
    global client
    if client is None:
        if not settings.MONGODB_URI:
            raise RuntimeError(
                "MONGODB_URI is not set. Add your MongoDB Atlas connection "
                "string as an environment variable / HF Space secret."
            )
        client = AsyncIOMotorClient(settings.MONGODB_URI)
    return client


def get_db():
    return get_client()[settings.MONGODB_DB_NAME]


def users_collection():
    return get_db()["users"]


def conversations_collection():
    return get_db()["conversations"]


def documents_collection():
    return get_db()["documents"]