boromir674/so-magic

from abc import ABC

__all__ = ['ObjectRegistry', 'ObjectRegistryError']


class ObjectRegistry(ABC):
    """Simple dict-like retrieval/inserting "store" facility."""

    def __new__(cls, *args, **kwargs):
        object_registry = super().__new__(cls)
        if args:
            object_registry.objects = args[0]
        else:
            object_registry.objects = {}
        return object_registry

    def add(self, key, value):
        if self.objects.get(key, None):
            raise ObjectRegistryError(f"Requested to insert value '{value}' in already existing key '{key}'. "
                                      f"All keys are [{', '.join(_ for _ in self.objects)}]")
        self.objects[key] = value

    def remove(self, key):
        if key not in self.objects:
            raise ObjectRegistryError(f"Requested to remove item with key {key}, which does not exist.")
        self.objects.pop(key)

    def pop(self, key):
        if key not in self.objects:
            raise ObjectRegistryError(f"Requested to pop item with key {key}, which does not exist.")
        return self.objects.pop(key)

    def get(self, key):
        if key not in self.objects:
            raise ObjectRegistryError(f"Requested to get item with key {key}, which does not exist.")
        return self.objects[key]

    def __iter__(self):
        return iter(self.objects.items())

    def __contains__(self, item):
        return item in self.objects

    def __eq__(self, other):
        return dict(self.objects) == dict(other)

    def __repr__(self):
        return repr(self.objects)


class ObjectRegistryError(Exception): pass