# Copyright (C) 2010 Google Inc. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#     * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
#     * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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import logging
import time
import urllib2

_log = logging.getLogger(__name__)


class NetworkTimeout(Exception):

    def __str__(self):
        return 'NetworkTimeout'


class NetworkTransaction(object):

    def __init__(self, initial_backoff_seconds=10, grown_factor=1.5, timeout_seconds=(10 * 60), return_none_on_404=False):
        self._initial_backoff_seconds = initial_backoff_seconds
        self._grown_factor = grown_factor
        self._timeout_seconds = timeout_seconds
        self._return_none_on_404 = return_none_on_404
        self._total_sleep = 0
        self._backoff_seconds = 0

    def run(self, request):
        self._total_sleep = 0
        self._backoff_seconds = self._initial_backoff_seconds
        while True:
            try:
                return request()
            except urllib2.HTTPError as error:
                if self._return_none_on_404 and error.code == 404:
                    return None
                self._check_for_timeout()
                _log.warning('Received HTTP status %s loading "%s".  Retrying in %s seconds...',
                             error.code, error.filename, self._backoff_seconds)
                self._sleep()

    def _check_for_timeout(self):
        if self._total_sleep + self._backoff_seconds > self._timeout_seconds:
            raise NetworkTimeout()

    def _sleep(self):
        time.sleep(self._backoff_seconds)
        self._total_sleep += self._backoff_seconds
        self._backoff_seconds *= self._grown_factor