from abc import ABCMeta, abstractmethod
import json
from website_generator.utils import Registry


class ActionMetaclass(ABCMeta):

    def __new__(cls, name, *args, **kwargs):
        newclass = ABCMeta.__new__(cls, name, *args, **kwargs)
        if name != 'Action':
            register(newclass)
        return newclass


class Action(metaclass=ActionMetaclass):

    def __init__(self, **params):
        for name, value in params.items():
            setattr(self, name, value)

    @abstractmethod
    def __call__(self):
        pass


class ActionRegistry(Registry):

    def check_key(self, key):
        assert isinstance(key, str), 'Action type must be a string.'

    def check_value(self, value):
        assert callable(value), 'Action must be a callable.'

    def register(self, key, value=None):
        """
        Register a generator action.
        May be used a register(action) if the action has a defined type
        (using the action.type attribute), or as register(type, action)
        or register(action, type) to set a custom type.
        """
        if value:
            try:
                # Try register(type, action)
                return super().register(key, value)
            except (KeyError, ValueError):
                # Try register(action, type)
                try:
                    return super().register(value, key)
                except (KeyError, ValueError):
                    pass
                raise

        if not getattr(key, 'type', None):
            raise KeyError(
                'Action does not have a type. '
                'Set the type attribute or use register(type, action)'
            )

        return super().register(key.type, key)


registry = ActionRegistry()
register = registry.register
unregister = registry.unregister


class DebugAction(Action):
    """
    A simple action that prints its execution context,
    for debugging purposes.
    """
    type = 'debug'

    def __call__(self):
        def _default(obj):
            if hasattr(obj, '__dict__'):
                return vars(obj)
            try:
                return dict(obj)
            except Exception:
                return str(obj)
        print(json.dumps(vars(self), default=_default, indent=4))