# Copyright 2015 The TensorFlow 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.
# ==============================================================================
"""Contains the Activation layer."""


from keras import activations
from keras.engine.base_layer import Layer

# isort: off
from tensorflow.python.util.tf_export import keras_export


@keras_export("keras.layers.Activation")
class Activation(Layer):
    """Applies an activation function to an output.

    Args:
      activation: Activation function, such as `tf.nn.relu`, or string name of
        built-in activation function, such as "relu".

    Usage:

    >>> layer = tf.keras.layers.Activation('relu')
    >>> output = layer([-3.0, -1.0, 0.0, 2.0])
    >>> list(output.numpy())
    [0.0, 0.0, 0.0, 2.0]
    >>> layer = tf.keras.layers.Activation(tf.nn.relu)
    >>> output = layer([-3.0, -1.0, 0.0, 2.0])
    >>> list(output.numpy())
    [0.0, 0.0, 0.0, 2.0]

    Input shape:
      Arbitrary. Use the keyword argument `input_shape`
      (tuple of integers, does not include the batch axis)
      when using this layer as the first layer in a model.

    Output shape:
      Same shape as input.
    """

    def __init__(self, activation, **kwargs):
        super().__init__(**kwargs)
        self.supports_masking = True
        self.activation = activations.get(activation)

    def call(self, inputs):
        return self.activation(inputs)

    def compute_output_shape(self, input_shape):
        return input_shape

    def get_config(self):
        config = {"activation": activations.serialize(self.activation)}
        base_config = super().get_config()
        return dict(list(base_config.items()) + list(config.items()))
