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


class Engine:
    def __init__(self):
        self.__methods = {}
        self.debug = False
        self.stack = []
        self.scopes = {'root': {}}
        self.scope = 'root'

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

    def visit(self, node):
        method = node['kind']
        visitor = self.__methods.get(method, self.__class__.generic_visit)
        result = visitor(self, node)
        return result

    def generic_visit(self, node):
        """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 variable_addition(self, name, value = None):
        current = self.scopes[self.scope]
        if name in current:
            raise Exception('Double declaration of the variable %s' % name)
        current[name] = value


    def variable_delete(self, name, value):
        current = self.scopes[self.scope]
        if name in current:
            del current[name]
        raise Exception('Переменная {} не найдена'.format(name))


    def variable_exist(self, name):
        current = self.scopes[self.scope]
        return name in current


    def variable_get(self, name):
        scope = self.scopes[self.scope]
        if name in scope:
            result = scope[name]
            return result
        stack = []
        if self.scope != 'root':
            stack.append(self.scope)
        while len(stack) > 0:
            scope_name = stack.pop()
            closures = list(
                filter(
                    closure_include(scope_name),
                    self.closures
                )
            )
            for closure in closures:
                stack.append(closure['parent'])
            scope = self.scopes[scope_name]
            if name in scope:
                result = scope[name]
                return result

        raise Exception('Переменная {} не найдена'.format(name))


    def variable_set(self, name, value):
        current = self.scopes[self.scope]
        if name in current:
            current[name] = value
            return
        raise Exception('Переменная {} не найдена'.format(name))

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

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

    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)