# Copyright 2017 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.
# ==============================================================================

"""Hooks helper to return a list of TensorFlow hooks for training by name.

More hooks can be added to this set. To add a new hook, 1) add the new hook to
the registry in HOOKS, 2) add a corresponding function that parses out necessary
parameters.
"""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import tensorflow as tf  # pylint: disable=g-bad-import-order

from official.utils.logs import hooks
from official.utils.logs import logger
from official.utils.logs import metric_hook

_TENSORS_TO_LOG = dict((x, x) for x in ['learning_rate',
                                        'cross_entropy',
                                        'train_accuracy'])


def get_train_hooks(name_list, use_tpu=False, **kwargs):
  """Factory for getting a list of TensorFlow hooks for training by name.

  Args:
    name_list: a list of strings to name desired hook classes. Allowed:
      LoggingTensorHook, ProfilerHook, ExamplesPerSecondHook, which are defined
      as keys in HOOKS
    use_tpu: Boolean of whether computation occurs on a TPU. This will disable
      hooks altogether.
    **kwargs: a dictionary of arguments to the hooks.

  Returns:
    list of instantiated hooks, ready to be used in a classifier.train call.

  Raises:
    ValueError: if an unrecognized name is passed.
  """

  if not name_list:
    return []

  if use_tpu:
    tf.logging.warning("hooks_helper received name_list `{}`, but a TPU is "
                       "specified. No hooks will be used.".format(name_list))
    return []

  train_hooks = []
  for name in name_list:
    hook_name = HOOKS.get(name.strip().lower())
    if hook_name is None:
      raise ValueError('Unrecognized training hook requested: {}'.format(name))
    else:
      train_hooks.append(hook_name(**kwargs))

  return train_hooks


def get_logging_tensor_hook(every_n_iter=100, tensors_to_log=None, **kwargs):  # pylint: disable=unused-argument
  """Function to get LoggingTensorHook.

  Args:
    every_n_iter: `int`, print the values of `tensors` once every N local
      steps taken on the current worker.
    tensors_to_log: List of tensor names or dictionary mapping labels to tensor
      names. If not set, log _TENSORS_TO_LOG by default.
    **kwargs: a dictionary of arguments to LoggingTensorHook.

  Returns:
    Returns a LoggingTensorHook with a standard set of tensors that will be
    printed to stdout.
  """
  if tensors_to_log is None:
    tensors_to_log = _TENSORS_TO_LOG

  return tf.train.LoggingTensorHook(
      tensors=tensors_to_log,
      every_n_iter=every_n_iter)


def get_profiler_hook(model_dir, save_steps=1000, **kwargs):  # pylint: disable=unused-argument
  """Function to get ProfilerHook.

  Args:
    model_dir: The directory to save the profile traces to.
    save_steps: `int`, print profile traces every N steps.
    **kwargs: a dictionary of arguments to ProfilerHook.

  Returns:
    Returns a ProfilerHook that writes out timelines that can be loaded into
    profiling tools like chrome://tracing.
  """
  return tf.train.ProfilerHook(save_steps=save_steps, output_dir=model_dir)


def get_examples_per_second_hook(every_n_steps=100,
                                 batch_size=128,
                                 warm_steps=5,
                                 **kwargs):  # pylint: disable=unused-argument
  """Function to get ExamplesPerSecondHook.

  Args:
    every_n_steps: `int`, print current and average examples per second every
      N steps.
    batch_size: `int`, total batch size used to calculate examples/second from
      global time.
    warm_steps: skip this number of steps before logging and running average.
    **kwargs: a dictionary of arguments to ExamplesPerSecondHook.

  Returns:
    Returns a ProfilerHook that writes out timelines that can be loaded into
    profiling tools like chrome://tracing.
  """
  return hooks.ExamplesPerSecondHook(
      batch_size=batch_size, every_n_steps=every_n_steps,
      warm_steps=warm_steps, metric_logger=logger.get_benchmark_logger())


def get_logging_metric_hook(tensors_to_log=None,
                            every_n_secs=600,
                            **kwargs):  # pylint: disable=unused-argument
  """Function to get LoggingMetricHook.

  Args:
    tensors_to_log: List of tensor names or dictionary mapping labels to tensor
      names. If not set, log _TENSORS_TO_LOG by default.
    every_n_secs: `int`, the frequency for logging the metric. Default to every
      10 mins.

  Returns:
    Returns a LoggingMetricHook that saves tensor values in a JSON format.
  """
  if tensors_to_log is None:
    tensors_to_log = _TENSORS_TO_LOG
  return metric_hook.LoggingMetricHook(
      tensors=tensors_to_log,
      metric_logger=logger.get_benchmark_logger(),
      every_n_secs=every_n_secs)


# A dictionary to map one hook name and its corresponding function
HOOKS = {
    'loggingtensorhook': get_logging_tensor_hook,
    'profilerhook': get_profiler_hook,
    'examplespersecondhook': get_examples_per_second_hook,
    'loggingmetrichook': get_logging_metric_hook,
}
