1# Copyright (c) 2010 Google Inc. All rights reserved.
2#
3# Redistribution and use in source and binary forms, with or without
4# modification, are permitted provided that the following conditions are
5# met:
6#
7#     * Redistributions of source code must retain the above copyright
8# notice, this list of conditions and the following disclaimer.
9#     * Redistributions in binary form must reproduce the above
10# copyright notice, this list of conditions and the following disclaimer
11# in the documentation and/or other materials provided with the
12# distribution.
13#     * Neither the name of Google Inc. nor the names of its
14# contributors may be used to endorse or promote products derived from
15# this software without specific prior written permission.
16#
17# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
20# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
21# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28
29
30class MessagePumpDelegate(object):
31    def schedule(self, interval, callback):
32        raise NotImplementedError, "subclasses must implement"
33
34    def message_available(self, message):
35        raise NotImplementedError, "subclasses must implement"
36
37    def final_message_delivered(self):
38        raise NotImplementedError, "subclasses must implement"
39
40
41class MessagePump(object):
42    interval = 10 # seconds
43
44    def __init__(self, delegate, message_queue):
45        self._delegate = delegate
46        self._message_queue = message_queue
47        self._schedule()
48
49    def _schedule(self):
50        self._delegate.schedule(self.interval, self._callback)
51
52    def _callback(self):
53        (messages, is_running) = self._message_queue.take_all()
54        for message in messages:
55            self._delegate.message_available(message)
56        if not is_running:
57            self._delegate.final_message_delivered()
58            return
59        self._schedule()
60