# Source code for rl_coach.memories.non_episodic.transition_collection

    #
    # Copyright (c) 2017 Intel Corporation
    #
    # 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 rl_coach.core_types import Transition

    class TransitionCollection(object):
        """
        Simple python implementation of transitions collection non-episodic memories
        are constructed on top of.
        """
        def __init__(self):
            super(TransitionCollection, self).__init__()

        def append(self, transition):
            pass

        def extend(self, transitions):
            for transition in transitions:
                self.append(transition)

        def __len__(self):
            pass

        def __del__(self, range: slice):
            # NOTE: the only slice used is the form: slice(None, n)
            # NOTE: if it is easier, what we really want here is the ability to
            # constrain the size of the collection. as new transitions are added,
            # old transitions can be removed to maintain a maximum collection size.
            pass

        def __getitem__(self, key: int):
            # NOTE: we can switch to a method which fetches multiple items at a time
            # if that would significantly improve performance
            pass

        def __iter__(self):
            # this is not high priority
            pass