# 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.
# ==============================================================================
"""Layer that computes the minimum (element-wise) of several inputs."""
# pylint: disable=g-direct-tensorflow-import

from keras.layers.merging.base_merge import _Merge
import tensorflow.compat.v2 as tf

from tensorflow.python.util.tf_export import keras_export


@keras_export('keras.layers.Minimum')
class Minimum(_Merge):
  """Layer that computes the minimum (element-wise) a list of inputs.

  It takes as input a list of tensors, all of the same shape, and returns
  a single tensor (also of the same shape).

  >>> tf.keras.layers.Minimum()([np.arange(5).reshape(5, 1),
  ...                            np.arange(5, 10).reshape(5, 1)])
  <tf.Tensor: shape=(5, 1), dtype=int64, numpy=
  array([[0],
       [1],
       [2],
       [3],
       [4]])>

  >>> x1 = tf.keras.layers.Dense(8)(np.arange(10).reshape(5, 2))
  >>> x2 = tf.keras.layers.Dense(8)(np.arange(10, 20).reshape(5, 2))
  >>> minned = tf.keras.layers.Minimum()([x1, x2])
  >>> minned.shape
  TensorShape([5, 8])
  """

  def _merge_function(self, inputs):
    output = inputs[0]
    for i in range(1, len(inputs)):
      output = tf.minimum(output, inputs[i])
    return output


@keras_export('keras.layers.minimum')
def minimum(inputs, **kwargs):
  """Functional interface to the `Minimum` layer.

  Args:
      inputs: A list of input tensors (at least 2).
      **kwargs: Standard layer keyword arguments.

  Returns:
      A tensor, the element-wise minimum of the inputs.
  """
  return Minimum(**kwargs)(inputs)
