#!/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