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# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
class MessageHandler(object):
"""A message handler providing message handling facilities to
classes derived from BaseHandler and BaseFormatter. This is a
composition class, to ensure handlers and formatters remain separate.
:param inner: A handler-like callable that may receive messages
from a log user.
"""
def __init__(self):
self.message_handlers = {}
self.wrapped = []
def register_message_handlers(self, topic, handlers):
self.message_handlers[topic] = handlers
def handle_message(self, topic, cmd, *args):
"""Handles a message for the given topic by calling a subclass-defined
callback for the command.
:param topic: The topic of the broadcasted message. Handlers opt-in to
receiving messages by identifying a topic when calling
register_message_handlers.
:param command: The command to issue. This is a string that corresponds
to a callback provided by the target.
:param arg: Arguments to pass to the identified message callback, if any.
"""
rv = []
if topic in self.message_handlers and cmd in self.message_handlers[topic]:
rv.append(self.message_handlers[topic][cmd](*args))
if self.wrapped:
for inner in self.wrapped:
rv.extend(inner.handle_message(topic, cmd, *args))
return rv