# Copyright 2022 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.
# ==============================================================================
"""The implementation of `tf.data.Dataset.filter`."""

from tensorflow.python.data.ops import dataset_ops
from tensorflow.python.data.ops import structured_function
from tensorflow.python.framework import dtypes
from tensorflow.python.framework import tensor_spec
from tensorflow.python.ops import gen_dataset_ops


def _filter(input_dataset, predicate, name=None):  # pylint: disable=redefined-builtin
  return _FilterDataset(input_dataset, predicate, name=name)


class _FilterDataset(dataset_ops.UnaryUnchangedStructureDataset):
  """A `Dataset` that filters its input according to a predicate function."""

  def __init__(self,
               input_dataset,
               predicate,
               use_legacy_function=False,
               name=None):
    """See `Dataset.filter` for details."""
    self._input_dataset = input_dataset
    wrapped_func = structured_function.StructuredFunctionWrapper(
        predicate,
        self._transformation_name(),
        dataset=input_dataset,
        use_legacy_function=use_legacy_function)
    if not wrapped_func.output_structure.is_compatible_with(
        tensor_spec.TensorSpec([], dtypes.bool)):
      raise ValueError(f"Invalid `predicate`. `predicate` must return a "
                       f"`tf.bool` scalar tensor, but its return type is "
                       f"{wrapped_func.output_structure}.")
    self._predicate = wrapped_func
    self._name = name
    variant_tensor = gen_dataset_ops.filter_dataset(
        input_dataset._variant_tensor,  # pylint: disable=protected-access
        other_arguments=self._predicate.function.captured_inputs,
        predicate=self._predicate.function,
        **self._common_args)
    super().__init__(input_dataset, variant_tensor)

  def _functions(self):
    return [self._predicate]

  def _transformation_name(self):
    return "Dataset.filter()"