import inspect

class Registry(object):
    def __init__(self, name):
        self._name = name
        self._module_dict = dict()
    def __repr__(self):
        format_str = self.__class__.__name__ + '(name={}, items={})'.format(self._name, list(self._module_dict.keys()))
        return format_str

    @property
    def name(self):
        return self._name
    @property
    def module_dict(self):
        return self._module_dict

    def get(self, key):
        return self._module_dict.get(key, None)

    def _register_module(self, module_class):
        if not inspect.isclass(module_class):
            raise TypeError('module must be a class, but receive {}.'.format(type(module_class)))
        module_name = module_class.__name__
        if module_name in self._module_dict:
            raise KeyError('{} is already registered in {}.'.format(module_name, self.name))
        self._module_dict[module_name] = module_class

    def register_module(self, cls):
        self._register_module(cls)
        return cls