# Copyright 2015 Amazon.com, Inc. or its affiliates. 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. A copy of
# the License is located at
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file 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.
from tests import unittest, IntegerRefresher
import threading
import math
import time


class TestCredentialRefreshRaces(unittest.TestCase):
    def assert_consistent_credentials_seen(self, creds, func):
        collected = []
        threads = []
        for _ in range(20):
            threads.append(threading.Thread(target=func, args=(collected,)))
        start = time.time()
        for thread in threads:
            thread.start()
        for thread in threads:
            thread.join()
        for creds in collected:
            # During testing, the refresher uses it's current
            # refresh count as the values for the access, secret, and
            # token value.  This means that at any given point in time,
            # the credentials should be something like:
            #
            # ReadOnlyCredentials('1', '1', '1')
            # ReadOnlyCredentials('2', '2', '2')
            # ...
            # ReadOnlyCredentials('30', '30', '30')
            #
            # This makes it really easy to verify we see a consistent
            # set of credentials from the same time period.  We just
            # check if all the credential values are the same.  If
            # we ever see something like:
            #
            # ReadOnlyCredentials('1', '2', '1')
            #
            # We fail.  This is because we're using the access_key
            # from the first refresh ('1'), the secret key from
            # the second refresh ('2'), and the token from the
            # first refresh ('1').
            self.assertTrue(creds[0] == creds[1] == creds[2], creds)

    def test_has_no_race_conditions(self):
        creds = IntegerRefresher(
            creds_last_for=2,
            advisory_refresh=1,
            mandatory_refresh=0
        )
        def _run_in_thread(collected):
            for _ in range(4000):
                frozen = creds.get_frozen_credentials()
                collected.append((frozen.access_key,
                                  frozen.secret_key,
                                  frozen.token))
        start = time.time()
        self.assert_consistent_credentials_seen(creds, _run_in_thread)
        end = time.time()
        # creds_last_for = 2 seconds (from above)
        # So, for example, if execution time took 6.1 seconds, then
        # we should see a maximum number of refreshes being (6 / 2.0) + 1 = 4
        max_calls_allowed = math.ceil((end - start) / 2.0) + 1
        self.assertTrue(creds.refresh_counter <= max_calls_allowed,
                        "Too many cred refreshes, max: %s, actual: %s, "
                        "time_delta: %.4f" % (max_calls_allowed,
                                              creds.refresh_counter,
                                              (end - start)))

    def test_no_race_for_immediate_advisory_expiration(self):
        creds = IntegerRefresher(
            creds_last_for=1,
            advisory_refresh=1,
            mandatory_refresh=0
        )
        def _run_in_thread(collected):
            for _ in range(100):
                frozen = creds.get_frozen_credentials()
                collected.append((frozen.access_key,
                                  frozen.secret_key,
                                  frozen.token))
        self.assert_consistent_credentials_seen(creds, _run_in_thread)