# 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.
# ==============================================================================
"""A cache for FileWriters."""

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

import threading

from tensorflow.python.framework import ops
from tensorflow.python.summary.writer.writer import FileWriter


class FileWriterCache(object):
  """Cache for file writers.

  This class caches file writers, one per directory.
  """
  # Cache, keyed by directory.
  _cache = {}

  # Lock protecting _FILE_WRITERS.
  _lock = threading.RLock()

  @staticmethod
  def clear():
    """Clear cached summary writers. Currently only used for unit tests."""
    with FileWriterCache._lock:
      # Make sure all the writers are closed now (otherwise open file handles
      # may hang around, blocking deletions on Windows).
      for item in FileWriterCache._cache.values():
        item.close()
      FileWriterCache._cache = {}

  @staticmethod
  def get(logdir):
    """Returns the FileWriter for the specified directory.

    Args:
      logdir: str, name of the directory.

    Returns:
      A `FileWriter`.
    """
    with FileWriterCache._lock:
      if logdir not in FileWriterCache._cache:
        FileWriterCache._cache[logdir] = FileWriter(
            logdir, graph=ops.get_default_graph())
      return FileWriterCache._cache[logdir]
