###########################################################################
#
#  Copyright (c) 2019-2020 Diality Inc. - All Rights Reserved.
#
#  THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
#  WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
#
#  @file base.py
#
#  @date 20-July-2020
#  @author P. Lucia
#
#  @brief Contains base classes for Dialin API sub systems and observers
#
#
############################################################################
from abc import ABC, abstractmethod
from datetime import datetime


class AbstractObserver(ABC):
    """
    Publicly accessible parent class for all observers.

    The update method will receive data when data is made available
    """

    @abstractmethod
    def update(self):
        """
        Attach an observer
        """
        pass


# abstract base class requires all abstract methods are overridden by children classes
class _AbstractSubSystem(ABC):

    @abstractmethod
    def __init__(self):
        """
        Initialization function for the sub system

        """
        self._observers = []
        self._datetime_fmt = "%m.%d.%Y_%I.%M.%S.%f"
        pass

    def attach(self, observer: AbstractObserver):
        """
        Attach an observer so it is updated upon published events
        """
        self._observers.append(observer)

    def detach(self, observer: AbstractObserver):
        """
        Detach an observer
        """
        self._observers.remove(observer)


def _publish(keys):
    """
    Decorator that accepts a list of variable names to publish
    To be used in any _AbstractSubSystem

    @param keys: The variable names to publish
    @return: A function that will take a function and return another function
    """

    def _decorator(func):
        """

        @param func: The handler function
        @return: The function to wrap around _publish
        """

        def _wrapper(self, *args, **kwargs):
            func(self, *args, **kwargs)
            result = {}

            if not self._observers:
                return None

            result["datetime"] = datetime.now()

            for key in keys:
                result[key] = getattr(self, key)

            for observer in self._observers:
                observer.update(result)

        return _wrapper

    return _decorator


class _AbstractSystem(ABC):
    """
    Parent class for all system classes
    """

    @abstractmethod
    def __init__(self):
        """
        Initialization function for the system

        """
        pass