# Copyright 2010 Google Inc. 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.
"""Ordered set implementations."""

import collections
import collections.abc


class _OrderedSetBase(object):

  def __init__(self, iterable=None):
    self._set = collections.OrderedDict()
    if iterable:
      for i in iterable:
        self._set[i] = 1

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

  def __contains__(self, thing):
    return thing in self._set

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


class _MutableSetBase(_OrderedSetBase):
  def add(self, thing):  # pylint:disable=g-bad-name
    self._set[thing] = 1

  def discard(self, thing):  # pylint:disable=g-bad-name
    if thing in self._set:
      del self._set[thing]

  def clear(self):  # pylint:disable=g-bad-name
    self._set.clear()


class FrozenOrderedSet(_OrderedSetBase, collections.abc.Set,
                       collections.abc.Hashable):
  __hash__ = collections.abc.Set._hash


class MutableOrderedSet(_MutableSetBase, collections.abc.MutableSet):
  pass