# coding=utf-8
# Copyright 2020 The Gin-Config Authors.
#
# 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.

"""Init file for PyTorch-specific Gin-Config package."""

# pylint: disable=g-import-not-at-top

# Ensure PyTorch is importable and its version is sufficiently recent. This
# needs to happen before anything else, since the imports below will try to
# import torch, too.
import sys as _sys


def _ensure_torch_install():  # pylint: disable=g-statement-before-imports
  """Attempt to import PyTorch, and ensure its version is sufficient.

  Raises:
    ImportError: If either PyTorch is not importable or its version is
      inadequate.
  """
  try:
    import torch
  except ImportError:
    # Print more informative error message, then reraise.
    print("\n\nFailed to import PyTorch. Please note that PyTorch is not "
          "installed by default when you install Gin-Config. This is so that "
          "users can decide whether to install TensorFlow, GPU-enabled "
          "Tensorflow or Pytorch. To use Gin-Config with PyTorch, please "
          "install the most recent version of PyTorch, by following "
          "instructions at https://pytorch.org/get-started.\n\n")
    raise

  # Update this whenever we need to depend on a newer PyTorch release.
  required_torch_version = "1.3.0"

  import distutils.version

  if (distutils.version.LooseVersion(torch.__version__) <
      distutils.version.LooseVersion(required_torch_version)):
    raise ImportError(
        "This version of Gin-Config requires PyTorch "
        "version >= {required}; Detected an installation of version {present}. "
        "Please upgrade PyTorch to proceed.".format(
            required=required_torch_version, present=torch.__version__))


_ensure_torch_install()

# Cleanup symbols to avoid polluting namespace.
# pylint: enable=g-import-not-at-top
for symbol in ["_ensure_torch_install", "_sys"]:
  delattr(_sys.modules[__name__], symbol)