##
# Copyright (c) 2009 Apple 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.
##

"""
Extensions to twisted.python.log.
"""

from sys import stdout, stderr

from twisted.python.log import addObserver, removeObserver

class StandardIOObserver (object):
    """
    Log observer that writes to standard I/O.
    """
    def emit(self, eventDict):
        text = None

        if eventDict["isError"]:
            output = stderr
            if "failure" in eventDict:
                text = eventDict["failure"].getTraceback()
        else:
            output = stdout

        if not text:
            text = " ".join([str(m) for m in eventDict["message"]]) + "\n"

        output.write(text)
        output.flush()

    def start(self):
        addObserver(self.emit)

    def stop(self):
        removeObserver(self.emit)