#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# 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.
#

"""Logging utilities for use by applications.

Classes defined here:
  AppLogsHandler: StreamHandler subclass
"""





import logging
import sys
import types


NEWLINE_REPLACEMENT = "\0"


class AppLogsHandler(logging.StreamHandler):
  """Logging handler that will direct output to a persistent store of
  application logs.

  This handler will output log statements to stderr. This handler is
  automatically initialized and attached to the Python common logging library.
  """




  def __init__(self, stream=None):
    """Constructor.

    Args:
      # stream is optional. it defaults to sys.stderr.
      stream: destination for output
    """
    logging.StreamHandler.__init__(self, stream)

  def close(self):
    """Closes the stream.

    This implementation based on the implementation of FileHandler.close()."""
    self.flush()
    self.stream.close()
    logging.StreamHandler.close(self)

  def emit(self, record):
    """Emit a record.

    This implementation is based on the implementation of
    StreamHandler.emit()."""
    try:
      message = self._AppLogsMessage(record)
      if isinstance(message, unicode):
        message = message.encode("UTF-8")
      self.stream.write(message)
      self.flush()
    except (KeyboardInterrupt, SystemExit):
      raise
    except:
      self.handleError(record)

  def _AppLogsMessage(self, record):
    """Converts the log record into a log line."""

    message = self.format(record).replace("\n", NEWLINE_REPLACEMENT)
    return "LOG %d %d %s\n" % (self._AppLogsLevel(record.levelno),
                               long(record.created * 1000 * 1000),
                               message)

  def _AppLogsLevel(self, level):
    """Converts the logging level used in Python to the API logging level"""
    if level >= logging.CRITICAL:
      return 4
    elif level >= logging.ERROR:
      return 3
    elif level >= logging.WARNING:
      return 2
    elif level >= logging.INFO:
      return 1
    else:
      return 0
