# Copyright 2015 Google Inc. 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.
# ==============================================================================

"""Function for loading TensorFlow plugins."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import hashlib
import imp
import sys
import threading

from six.moves.builtins import bytes  # pylint: disable=redefined-builtin

from tensorflow.core.framework import op_def_pb2
from tensorflow.core.lib.core import error_codes_pb2
from tensorflow.python import pywrap_tensorflow as py_tf
from tensorflow.python.framework import errors
from tensorflow.python.util import compat


# Thread safe dict to memoize the library filename to module mapping
_OP_LIBRARY_MAP = {}
_OP_LIBRARY_MAP_LOCK = threading.Lock()


def load_op_library(library_filename):
  """Loads a TensorFlow plugin, containing custom ops and kernels.

  Pass "library_filename" to a platform-specific mechanism for dynamically
  loading a library. The rules for determining the exact location of the
  library are platform-specific and are not documented here.

  Args:
    library_filename: Path to the plugin.
      Relative or absolute filesystem path to a dynamic library file.

  Returns:
    A python module containing the Python wrappers for Ops defined in
    the plugin.

  Raises:
    RuntimeError: when unable to load the library or get the python wrappers.
  """
  status = py_tf.TF_NewStatus()

  lib_handle = py_tf.TF_LoadLibrary(library_filename, status)
  try:
    error_code = py_tf.TF_GetCode(status)
    if error_code != 0:
      error_msg = compat.as_text(py_tf.TF_Message(status))
      with _OP_LIBRARY_MAP_LOCK:
        if (error_code == error_codes_pb2.ALREADY_EXISTS and
            'has already been loaded' in error_msg and
            library_filename in _OP_LIBRARY_MAP):
          return _OP_LIBRARY_MAP[library_filename]
      # pylint: disable=protected-access
      raise errors._make_specific_exception(None, None, error_msg, error_code)
      # pylint: enable=protected-access
  finally:
    py_tf.TF_DeleteStatus(status)

  op_list_str = py_tf.TF_GetOpList(lib_handle)
  op_list = op_def_pb2.OpList()
  op_list.ParseFromString(compat.as_bytes(op_list_str))
  wrappers = py_tf.GetPythonWrappers(op_list_str)

  # Get a unique name for the module.
  module_name = hashlib.md5(wrappers).hexdigest()
  module = imp.new_module(module_name)
  # pylint: disable=exec-used
  exec(wrappers, module.__dict__)
  # Stash away the library handle for making calls into the dynamic library.
  module.LIB_HANDLE = lib_handle
  # OpDefs of the list of ops defined in the library.
  module.OP_LIST = op_list
  sys.modules[module_name] = module
  # Memoize the filename to module mapping.
  with _OP_LIBRARY_MAP_LOCK:
    _OP_LIBRARY_MAP[library_filename] = module
  return module


_FILE_SYSTEM_LIBRARY_MAP = {}
_FILE_SYSTEM_LIBRARY_MAP_LOCK = threading.Lock()


def load_file_system_library(library_filename):
  """Loads a TensorFlow plugin, containing file system implementation.

  Pass `library_filename` to a platform-specific mechanism for dynamically
  loading a library. The rules for determining the exact location of the
  library are platform-specific and are not documented here.

  Args:
    library_filename: Path to the plugin.
      Relative or absolute filesystem path to a dynamic library file.

  Returns:
    None.

  Raises:
    RuntimeError: when unable to load the library.
  """
  status = py_tf.TF_NewStatus()
  lib_handle = py_tf.TF_LoadLibrary(library_filename, status)
  try:
    error_code = py_tf.TF_GetCode(status)
    if error_code != 0:
      error_msg = compat.as_text(py_tf.TF_Message(status))
      with _FILE_SYSTEM_LIBRARY_MAP_LOCK:
        if (error_code == error_codes_pb2.ALREADY_EXISTS and
            'has already been loaded' in error_msg and
            library_filename in _FILE_SYSTEM_LIBRARY_MAP):
          return
      # pylint: disable=protected-access
      raise errors._make_specific_exception(None, None, error_msg, error_code)
      # pylint: enable=protected-access
  finally:
    py_tf.TF_DeleteStatus(status)

  with _FILE_SYSTEM_LIBRARY_MAP_LOCK:
    _FILE_SYSTEM_LIBRARY_MAP[library_filename] = lib_handle
