# Source code for rl_coach.filters.observation.observation_normalization_filter

    #
    # 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.
    #
    import os
    import pickle
    from typing import List

    import numpy as np

    from rl_coach.core_types import ObservationType
    from rl_coach.filters.observation.observation_filter import ObservationFilter
    from rl_coach.spaces import ObservationSpace
    from rl_coach.utilities.shared_running_stats import NumpySharedRunningStats, NumpySharedRunningStats

    class ObservationNormalizationFilter(ObservationFilter):
        """
        Normalizes the observation values with a running mean and standard deviation of
        all the observations seen so far. The normalization is performed element-wise. Additionally, when working with
        multiple workers, the statistics used for the normalization operation are accumulated over all the workers.
        """
        def __init__(self, clip_min: float=-5.0, clip_max: float=5.0, name='observation_stats'):
            """
            :param clip_min: The minimum value to allow after normalizing the observation
            :param clip_max: The maximum value to allow after normalizing the observation
            """
            super().__init__()
            self.clip_min = clip_min
            self.clip_max = clip_max
            self.running_observation_stats = None
            self.name = name
            self.supports_batching = True
            self.observation_space = None

        def set_device(self, device, memory_backend_params=None, mode='numpy') -> None:
            """
            An optional function that allows the filter to get the device if it is required to use tensorflow ops
            :param device: the device to use
            :memory_backend_params: if not None, holds params for a memory backend for sharing data (e.g. Redis)
            :param mode: the arithmetic module to use {'tf' | 'numpy'}
            :return: None
            """
            if mode == 'tf':
                from rl_coach.architectures.tensorflow_components.shared_variables import TFSharedRunningStats
                self.running_observation_stats = TFSharedRunningStats(device, name=self.name, create_ops=False,
                                                                pubsub_params=memory_backend_params)
            elif mode == 'numpy':
                self.running_observation_stats = NumpySharedRunningStats(name=self.name,
                                                                         pubsub_params=memory_backend_params)

        def set_session(self, sess) -> None:
            """
            An optional function that allows the filter to get the session if it is required to use tensorflow ops
            :param sess: the session
            :return: None
            """
            self.running_observation_stats.set_session(sess)

        def filter(self, observations: List[ObservationType], update_internal_state: bool=True) -> ObservationType:
            observations = np.array(observations)
            if update_internal_state:
                self.running_observation_stats.push(observations)
                self.last_mean = self.running_observation_stats.mean
                self.last_stdev = self.running_observation_stats.std

            return self.running_observation_stats.normalize(observations)

        def get_filtered_observation_space(self, input_observation_space: ObservationSpace) -> ObservationSpace:
            self.running_observation_stats.set_params(shape=input_observation_space.shape,
                                                      clip_values=(self.clip_min, self.clip_max))
            return input_observation_space

        def save_state_to_checkpoint(self, checkpoint_dir: str, checkpoint_prefix: str):
            self.running_observation_stats.save_state_to_checkpoint(checkpoint_dir, checkpoint_prefix)

        def restore_state_from_checkpoint(self, checkpoint_dir: str, checkpoint_prefix: str):
            self.running_observation_stats.restore_state_from_checkpoint(checkpoint_dir, checkpoint_prefix)