# Copyright (c) 2010 Google Inc. All rights reserved.
#
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# modification, are permitted provided that the following conditions are
# met:
#
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# notice, this list of conditions and the following disclaimer.
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# in the documentation and/or other materials provided with the
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class MessagePumpDelegate(object):
    def schedule(self, interval, callback):
        raise NotImplementedError('subclasses must implement')

    def message_available(self, message):
        raise NotImplementedError('subclasses must implement')

    def final_message_delivered(self):
        raise NotImplementedError('subclasses must implement')


class MessagePump(object):
    interval = 10  # seconds.

    def __init__(self, delegate, message_queue):
        self._delegate = delegate
        self._message_queue = message_queue
        self._schedule()

    def _schedule(self):
        self._delegate.schedule(self.interval, self._callback)

    def _callback(self):
        (messages, is_running) = self._message_queue.take_all()
        for message in messages:
            self._delegate.message_available(message)
        if not is_running:
            self._delegate.final_message_delivered()
            return
        self._schedule()