from copy import deepcopy
from pickle import dumps, loads
from datetime import datetime


def state_setter(obj, state):
    print(f"setting state with: {state}")
    obj._state = state["_state"]


class Pickleable:
    def __init__(self):
        self._state = datetime.now()

    def __str__(self):
        return str(self._state)

    def __reduce__(self):
        return (
            object.__new__,
            (type(self),),
            {"_state": self._state},
            None,
            None,
            state_setter,
        )


def deep_copier(arg, memo=None):
    print(f"deepcopying with: arg={arg}, memo={memo}")
    return deepcopy(arg, memo)


class Copyable:
    def __init__(self):
        self._state = datetime.now()

    def __str__(self):
        return str(self._state)

    def __reduce__(self):
        return (
            object.__new__,
            (type(self),),
            {"_state": self._state},
            None,
            None,
            deep_copier,
        )


p1 = Pickleable()
c1 = Copyable()

# these work:
p1_p = loads(dumps(p1))
c1_c = deepcopy(c1)

# these fail:
p1_c = deepcopy(p1)
c1_p = loads(dumps(c1))