__author__ = 'RemiZOffAlex'
__email__ = 'remizoffalex@mail.ru'


class Visitor:
    def __init__(self, methods: dict = {}):
        self.__methods = methods

    def register(self, name, handler):
        self.__methods[name] = handler

    def visit(self, node, *args, **kwargs):
        if 'kind' in node:
            name = node['kind']
        else:
            raise ValueError('Node is empty')
        method = self.__methods.get(name, self.__class__.generic_visit)
        result = method(self, node, *args, **kwargs)
        return result

    def generic_visit(self, node, *args, **kwargs):
        """Called if no explicit visitor function exists for a node."""
        method = node['kind']
        raise NotImplementedError('No visitor method {method} was defined for this expression: {node}'.format(
            method=method,
            node=node
        ))

    def __getattr__(self, name):
        raise AttributeError('Вызван несуществующий метод {name}'.format(name=name))

    def __getitem__(self, key):
        method = self.__methods[key]
        return method

    def __iter__(self):
        return iter(self.__methods)

    def __len__(self):
        return len(self.__methods)

    def __delitem__(self, key):
        del self.__methods[key]

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