# 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.
# ==============================================================================
"""Global max pooling 2D layer."""


from keras import backend
from keras.layers.pooling.base_global_pooling2d import GlobalPooling2D

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


@keras_export("keras.layers.GlobalMaxPool2D", "keras.layers.GlobalMaxPooling2D")
class GlobalMaxPooling2D(GlobalPooling2D):
    """Global max pooling operation for spatial data.

    Examples:

    >>> input_shape = (2, 4, 5, 3)
    >>> x = tf.random.normal(input_shape)
    >>> y = tf.keras.layers.GlobalMaxPool2D()(x)
    >>> print(y.shape)
    (2, 3)

    Args:
      data_format: A string,
        one of `channels_last` (default) or `channels_first`.
        The ordering of the dimensions in the inputs.
        `channels_last` corresponds to inputs with shape
        `(batch, height, width, channels)` while `channels_first`
        corresponds to inputs with shape
        `(batch, channels, height, width)`.
        It defaults to the `image_data_format` value found in your
        Keras config file at `~/.keras/keras.json`.
        If you never set it, then it will be "channels_last".
      keepdims: A boolean, whether to keep the spatial dimensions or not.
        If `keepdims` is `False` (default), the rank of the tensor is reduced
        for spatial dimensions.
        If `keepdims` is `True`, the spatial dimensions are retained with
        length 1.
        The behavior is the same as for `tf.reduce_max` or `np.max`.

    Input shape:
      - If `data_format='channels_last'`:
        4D tensor with shape `(batch_size, rows, cols, channels)`.
      - If `data_format='channels_first'`:
        4D tensor with shape `(batch_size, channels, rows, cols)`.

    Output shape:
      - If `keepdims`=False:
        2D tensor with shape `(batch_size, channels)`.
      - If `keepdims`=True:
        - If `data_format='channels_last'`:
          4D tensor with shape `(batch_size, 1, 1, channels)`
        - If `data_format='channels_first'`:
          4D tensor with shape `(batch_size, channels, 1, 1)`
    """

    def call(self, inputs):
        if self.data_format == "channels_last":
            return backend.max(inputs, axis=[1, 2], keepdims=self.keepdims)
        else:
            return backend.max(inputs, axis=[2, 3], keepdims=self.keepdims)


# Alias

GlobalMaxPool2D = GlobalMaxPooling2D