"""
Copyright 2020 The OneFlow Authors. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""
from contextlib import contextmanager


class ScopeStack(object):
    def __init__(self, init=[]):
        if not isinstance(init, list):
            init = [init]
        assert isinstance(init, list)
        self.stack_ = init

    def Current(self):
        assert len(self.stack_) > 0
        return self.stack_[0]

    @contextmanager
    def NewScope(self, scope):
        self.stack_.insert(0, scope)
        yield
        self.stack_.pop(0)
