# -*- coding: utf-8 -*-
"""
Author: J.A. de Jong

Description: MonkeyPatch required to let the Multiprocessing library work properly.
Should be applied prior to running any other multiprocessing code. Comes from
Stackoverflow and is mainly used for managing a list of queues that can be
shared between processes.

For more information, see:
https://stackoverflow.com/questions/46779860/multiprocessing-managers-and-custom-classes
"""
from multiprocessing import managers
import logging
from functools import wraps
from inspect import signature

orig_AutoProxy = managers.AutoProxy

__all__ = ['apply_patch']


@wraps(managers.AutoProxy)
def AutoProxy(*args, incref=True, manager_owned=False, **kwargs):
    # Create the autoproxy without the manager_owned flag, then
    # update the flag on the generated instance. If the manager_owned flag
    # is set, `incref` is disabled, so set it to False here for the same
    # result.
    autoproxy_incref = False if manager_owned else incref
    proxy = orig_AutoProxy(*args, incref=autoproxy_incref, **kwargs)
    proxy._owned_by_manager = manager_owned
    return proxy


def apply_patch():
    if "manager_owned" in signature(managers.AutoProxy).parameters:
        return

    logging.debug("Patching multiprocessing.managers.AutoProxy to add manager_owned")
    managers.AutoProxy = AutoProxy

    # re-register any types already registered to SyncManager without a custom
    # proxy type, as otherwise these would all be using the old unpatched AutoProxy
    SyncManager = managers.SyncManager
    registry = managers.SyncManager._registry
    for typeid, (callable, exposed, method_to_typeid, proxytype) in registry.items():
        if proxytype is not orig_AutoProxy:
            continue
        create_method = hasattr(managers.SyncManager, typeid)
        SyncManager.register(
            typeid,
            callable=callable,
            exposed=exposed,
            method_to_typeid=method_to_typeid,
            create_method=create_method,
        )