# Copyright 2012-2014 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.
"""Test utilities for the AWS CLI.

This module includes various classes/functions that help in writing
CLI unit/integration tests.  This module should not be imported by
any module **except** for test code.  This is included in the CLI
package so that code that is not part of the CLI can still take
advantage of all the testing utilities we provide.

"""
import os
import sys
import copy
import shutil
import time
import json
import logging
import tempfile
import platform
import contextlib
import string
import binascii
from pprint import pformat
from subprocess import Popen, PIPE
from unittest import mock

from awscli.compat import StringIO


from botocore.session import Session
from botocore.exceptions import ClientError
from botocore.exceptions import WaiterError
import botocore.loaders
from botocore.awsrequest import AWSResponse

import awscli.clidriver
from awscli.plugin import load_plugins
from awscli.clidriver import CLIDriver
from awscli.compat import BytesIO, StringIO
from awscli import EnvironmentVariables


import unittest


_LOADER = botocore.loaders.Loader()
INTEG_LOG = logging.getLogger('awscli.tests.integration')
AWS_CMD = None


def skip_if_windows(reason):
    """Decorator to skip tests that should not be run on windows.

    Example usage:

        @skip_if_windows("Not valid")
        def test_some_non_windows_stuff(self):
            self.assertEqual(...)

    """
    def decorator(func):
        return unittest.skipIf(
            platform.system() not in ['Darwin', 'Linux'], reason)(func)
    return decorator


def create_clidriver():
    driver = awscli.clidriver.create_clidriver()
    session = driver.session
    data_path = session.get_config_variable('data_path').split(os.pathsep)
    if not data_path:
        data_path = []
    _LOADER.search_paths.extend(data_path)
    session.register_component('data_loader', _LOADER)
    return driver


def get_aws_cmd():
    global AWS_CMD
    import awscli
    if AWS_CMD is None:
        # Try <repo>/bin/aws
        repo_root = os.path.dirname(os.path.abspath(awscli.__file__))
        aws_cmd = os.path.join(repo_root, 'bin', 'aws')
        if not os.path.isfile(aws_cmd):
            aws_cmd = _search_path_for_cmd('aws')
            if aws_cmd is None:
                raise ValueError('Could not find "aws" executable.  Either '
                                 'make sure it is on your PATH, or you can '
                                 'explicitly set this value using '
                                 '"set_aws_cmd()"')
        AWS_CMD = aws_cmd
    return AWS_CMD


def _search_path_for_cmd(cmd_name):
    for path in os.environ.get('PATH', '').split(os.pathsep):
        full_cmd_path = os.path.join(path, cmd_name)
        if os.path.isfile(full_cmd_path):
            return full_cmd_path
    return None


def set_aws_cmd(aws_cmd):
    global AWS_CMD
    AWS_CMD = aws_cmd


@contextlib.contextmanager
def temporary_file(mode):
    """This is a cross platform temporary file creation.

    tempfile.NamedTemporary file on windows creates a secure temp file
    that can't be read by other processes and can't be opened a second time.

    For tests, we generally *want* them to be read multiple times.
    The test fixture writes the temp file contents, the test reads the
    temp file.

    """
    temporary_directory = tempfile.mkdtemp()
    basename = 'tmpfile-%s' % str(random_chars(8))
    full_filename = os.path.join(temporary_directory, basename)
    open(full_filename, 'w').close()
    try:
        with open(full_filename, mode) as f:
            yield f
    finally:
        shutil.rmtree(temporary_directory)


def create_bucket(session, name=None, region=None):
    """
    Creates a bucket
    :returns: the name of the bucket created
    """
    if not region:
        region = 'us-west-2'
    client = session.create_client('s3', region_name=region)
    if name:
        bucket_name = name
    else:
        bucket_name = random_bucket_name()
    params = {'Bucket': bucket_name, 'ObjectOwnership': 'ObjectWriter'}
    if region != 'us-east-1':
        params['CreateBucketConfiguration'] = {'LocationConstraint': region}
    try:
        client.create_bucket(**params)
    except ClientError as e:
        if e.response['Error'].get('Code') == 'BucketAlreadyOwnedByYou':
            # This can happen in the retried request, when the first one
            # succeeded on S3 but somehow the response never comes back.
            # We still got a bucket ready for test anyway.
            pass
        else:
            raise
    return bucket_name


def random_chars(num_chars):
    """Returns random hex characters.

    Useful for creating resources with random names.

    """
    return binascii.hexlify(os.urandom(int(num_chars / 2))).decode('ascii')


def random_bucket_name(prefix='awscli-s3integ-', num_random=15):
    """Generate a random S3 bucket name.

    :param prefix: A prefix to use in the bucket name.  Useful
        for tracking resources.  This default value makes it easy
        to see which buckets were created from CLI integ tests.
    :param num_random: Number of random chars to include in the bucket name.

    :returns: The name of a randomly generated bucket name as a string.

    """
    return prefix + random_chars(num_random)


class BaseCLIDriverTest(unittest.TestCase):
    """Base unittest that use clidriver.

    This will load all the default plugins as well so it
    will simulate the behavior the user will see.
    """
    def setUp(self):
        self.environ = {
            'AWS_DATA_PATH': os.environ['AWS_DATA_PATH'],
            'AWS_DEFAULT_REGION': 'us-east-1',
            'AWS_ACCESS_KEY_ID': 'access_key',
            'AWS_SECRET_ACCESS_KEY': 'secret_key',
            'AWS_CONFIG_FILE': '',
        }
        self.environ_patch = mock.patch('os.environ', self.environ)
        self.environ_patch.start()
        self.driver = create_clidriver()
        self.session = self.driver.session

    def tearDown(self):
        self.environ_patch.stop()


class BaseAWSHelpOutputTest(BaseCLIDriverTest):
    def setUp(self):
        super(BaseAWSHelpOutputTest, self).setUp()
        self.renderer_patch = mock.patch('awscli.help.get_renderer')
        self.renderer_mock = self.renderer_patch.start()
        self.renderer = CapturedRenderer()
        self.renderer_mock.return_value = self.renderer

    def tearDown(self):
        super(BaseAWSHelpOutputTest, self).tearDown()
        self.renderer_patch.stop()

    def assert_contains(self, contains):
        if contains not in self.renderer.rendered_contents:
            self.fail("The expected contents:\n%s\nwere not in the "
                      "actual rendered contents:\n%s" % (
                          contains, self.renderer.rendered_contents))

    def assert_contains_with_count(self, contains, count):
        r_count = self.renderer.rendered_contents.count(contains)
        if r_count != count:
            self.fail("The expected contents:\n%s\n, with the "
                      "count:\n%d\nwere not in the actual rendered "
                      " contents:\n%s\nwith count:\n%d" % (
                          contains, count, self.renderer.rendered_contents, r_count))

    def assert_not_contains(self, contents):
        if contents in self.renderer.rendered_contents:
            self.fail("The contents:\n%s\nwere not suppose to be in the "
                      "actual rendered contents:\n%s" % (
                          contents, self.renderer.rendered_contents))

    def assert_text_order(self, *args, **kwargs):
        # First we need to find where the SYNOPSIS section starts.
        starting_from = kwargs.pop('starting_from')
        args = list(args)
        contents = self.renderer.rendered_contents
        self.assertIn(starting_from, contents)
        start_index = contents.find(starting_from)
        arg_indices = [contents.find(arg, start_index) for arg in args]
        previous = arg_indices[0]
        for i, index in enumerate(arg_indices[1:], 1):
            if index == -1:
                self.fail('The string %r was not found in the contents: %s'
                          % (args[index], contents))
            if index < previous:
                self.fail('The string %r came before %r, but was suppose to come '
                          'after it.\n%s' % (args[i], args[i - 1], contents))
            previous = index


class CapturedRenderer(object):
    def __init__(self):
        self.rendered_contents = ''

    def render(self, contents):
        self.rendered_contents = contents.decode('utf-8')


class CapturedOutput(object):
    def __init__(self, stdout, stderr):
        self.stdout = stdout
        self.stderr = stderr


@contextlib.contextmanager
def capture_output():
    stderr = StringIO()
    stdout = StringIO()
    with mock.patch('sys.stderr', stderr):
        with mock.patch('sys.stdout', stdout):
            yield CapturedOutput(stdout, stderr)


@contextlib.contextmanager
def capture_input(input_bytes=b''):
    input_data = BytesIO(input_bytes)
    mock_object = mock.Mock()
    mock_object.buffer = input_data

    with mock.patch('sys.stdin', mock_object):
        yield input_data


class BaseAWSCommandParamsTest(unittest.TestCase):
    maxDiff = None

    def setUp(self):
        self.last_params = {}
        self.last_kwargs = None
        # awscli/__init__.py injects AWS_DATA_PATH at import time
        # so that we can find cli.json.  This might be fixed in the
        # future, but for now we just grab that value out of the real
        # os.environ so the patched os.environ has this data and
        # the CLI works.
        self.environ = {
            'AWS_DATA_PATH': os.environ['AWS_DATA_PATH'],
            'AWS_DEFAULT_REGION': 'us-east-1',
            'AWS_ACCESS_KEY_ID': 'access_key',
            'AWS_SECRET_ACCESS_KEY': 'secret_key',
            'AWS_CONFIG_FILE': '',
            'AWS_SHARED_CREDENTIALS_FILE': '',
        }
        if os.environ.get('ComSpec'):
            self.environ['ComSpec'] = os.environ['ComSpec']
        self.environ_patch = mock.patch('os.environ', self.environ)
        self.environ_patch.start()
        self.http_response = AWSResponse(None, 200, {}, None)
        self.parsed_response = {}
        self.make_request_patch = mock.patch('botocore.endpoint.Endpoint.make_request')
        self.make_request_is_patched = False
        self.operations_called = []
        self.parsed_responses = None
        self.driver = create_clidriver()

    def tearDown(self):
        # This clears all the previous registrations.
        self.environ_patch.stop()
        if self.make_request_is_patched:
            self.make_request_patch.stop()
            self.make_request_is_patched = False

    def before_call(self, params, **kwargs):
        self._store_params(params)

    def _store_params(self, params):
        self.last_request_dict = params
        self.last_params = params['body']

    def patch_make_request(self):
        # If you do not stop a previously started patch,
        # it can never be stopped if you call start() again on the same
        # patch again...
        # So stop the current patch before calling start() on it again.
        if self.make_request_is_patched:
            self.make_request_patch.stop()
            self.make_request_is_patched = False
        make_request_patch = self.make_request_patch.start()
        if self.parsed_responses is not None:
            make_request_patch.side_effect = lambda *args, **kwargs: \
                (self.http_response, self.parsed_responses.pop(0))
        else:
            make_request_patch.return_value = (self.http_response, self.parsed_response)
        self.make_request_is_patched = True

    def assert_params_for_cmd(self, cmd, params=None, expected_rc=0,
                              stderr_contains=None, ignore_params=None):
        stdout, stderr, rc = self.run_cmd(cmd, expected_rc)
        if stderr_contains is not None:
            self.assertIn(stderr_contains, stderr)
        if params is not None:
            # The last kwargs of Operation.call() in botocore.
            last_kwargs = copy.copy(self.last_kwargs)
            if ignore_params is not None:
                for key in ignore_params:
                    try:
                        del last_kwargs[key]
                    except KeyError:
                        pass
            if params != last_kwargs:
                self.fail("Actual params did not match expected params.\n"
                          "Expected:\n\n"
                          "%s\n"
                          "Actual:\n\n%s\n" % (
                              pformat(params), pformat(last_kwargs)))
        return stdout, stderr, rc

    def before_parameter_build(self, params, model, **kwargs):
        self.last_kwargs = params
        self.operations_called.append((model, params.copy()))

    def run_cmd(self, cmd, expected_rc=0):
        logging.debug("Calling cmd: %s", cmd)
        self.patch_make_request()
        event_emitter = self.driver.session.get_component('event_emitter')
        event_emitter.register('before-call', self.before_call)
        event_emitter.register_first(
            'before-parameter-build.*.*', self.before_parameter_build)
        if not isinstance(cmd, list):
            cmdlist = cmd.split()
        else:
            cmdlist = cmd

        with capture_output() as captured:
            try:
                rc = self.driver.main(cmdlist)
            except SystemExit as e:
                # We need to catch SystemExit so that we
                # can get a proper rc and still present the
                # stdout/stderr to the test runner so we can
                # figure out what went wrong.
                rc = e.code
        stderr = captured.stderr.getvalue()
        stdout = captured.stdout.getvalue()
        self.assertEqual(
            rc, expected_rc,
            "Unexpected rc (expected: %s, actual: %s) for command: %s\n"
            "stdout:\n%sstderr:\n%s" % (
                expected_rc, rc, cmd, stdout, stderr))
        return stdout, stderr, rc


class BaseAWSPreviewCommandParamsTest(BaseAWSCommandParamsTest):
    def setUp(self):
        self.preview_patch = mock.patch(
            'awscli.customizations.preview.mark_as_preview')
        self.preview_patch.start()
        super(BaseAWSPreviewCommandParamsTest, self).setUp()

    def tearDown(self):
        self.preview_patch.stop()
        super(BaseAWSPreviewCommandParamsTest, self).tearDown()


class BaseCLIWireResponseTest(unittest.TestCase):
    def setUp(self):
        self.environ = {
            'AWS_DATA_PATH': os.environ['AWS_DATA_PATH'],
            'AWS_DEFAULT_REGION': 'us-east-1',
            'AWS_ACCESS_KEY_ID': 'access_key',
            'AWS_SECRET_ACCESS_KEY': 'secret_key',
            'AWS_CONFIG_FILE': ''
        }
        self.environ_patch = mock.patch('os.environ', self.environ)
        self.environ_patch.start()
        # TODO: fix this patch when we have a better way to stub out responses
        self.send_patch = mock.patch('botocore.endpoint.Endpoint._send')
        self.send_is_patched = False
        self.driver = create_clidriver()

    def tearDown(self):
        self.environ_patch.stop()
        if self.send_is_patched:
            self.send_patch.stop()
            self.send_is_patched = False

    def patch_send(self, status_code=200, headers={}, content=b''):
        if self.send_is_patched:
            self.send_patch.stop()
            self.send_is_patched = False
        send_patch = self.send_patch.start()
        send_patch.return_value = mock.Mock(status_code=status_code,
                                            headers=headers,
                                            content=content)
        self.send_is_patched = True

    def run_cmd(self, cmd, expected_rc=0):
        if not isinstance(cmd, list):
            cmdlist = cmd.split()
        else:
            cmdlist = cmd
        with capture_output() as captured:
            try:
                rc = self.driver.main(cmdlist)
            except SystemExit as e:
                rc = e.code
        stderr = captured.stderr.getvalue()
        stdout = captured.stdout.getvalue()
        self.assertEqual(
            rc, expected_rc,
            "Unexpected rc (expected: %s, actual: %s) for command: %s\n"
            "stdout:\n%sstderr:\n%s" % (
                expected_rc, rc, cmd, stdout, stderr))
        return stdout, stderr, rc



class FileCreator(object):
    def __init__(self):
        self.rootdir = tempfile.mkdtemp()

    def remove_all(self):
        if os.path.exists(self.rootdir):
            shutil.rmtree(self.rootdir)

    def create_file(self, filename, contents, mtime=None, mode='w'):
        """Creates a file in a tmpdir

        ``filename`` should be a relative path, e.g. "foo/bar/baz.txt"
        It will be translated into a full path in a tmp dir.

        If the ``mtime`` argument is provided, then the file's
        mtime will be set to the provided value (must be an epoch time).
        Otherwise the mtime is left untouched.

        ``mode`` is the mode the file should be opened either as ``w`` or
        `wb``.

        Returns the full path to the file.

        """
        full_path = os.path.join(self.rootdir, filename)
        if not os.path.isdir(os.path.dirname(full_path)):
            os.makedirs(os.path.dirname(full_path))
        with open(full_path, mode) as f:
            f.write(contents)
        current_time = os.path.getmtime(full_path)
        # Subtract a few years off the last modification date.
        os.utime(full_path, (current_time, current_time - 100000000))
        if mtime is not None:
            os.utime(full_path, (mtime, mtime))
        return full_path

    def append_file(self, filename, contents):
        """Append contents to a file

        ``filename`` should be a relative path, e.g. "foo/bar/baz.txt"
        It will be translated into a full path in a tmp dir.

        Returns the full path to the file.
        """
        full_path = os.path.join(self.rootdir, filename)
        if not os.path.isdir(os.path.dirname(full_path)):
            os.makedirs(os.path.dirname(full_path))
        with open(full_path, 'a') as f:
            f.write(contents)
        return full_path

    def full_path(self, filename):
        """Translate relative path to full path in temp dir.

        f.full_path('foo/bar.txt') -> /tmp/asdfasd/foo/bar.txt
        """
        return os.path.join(self.rootdir, filename)


class ProcessTerminatedError(Exception):
    pass


class Result(object):
    def __init__(self, rc, stdout, stderr, memory_usage=None):
        self.rc = rc
        self.stdout = stdout
        self.stderr = stderr
        INTEG_LOG.debug("rc: %s", rc)
        INTEG_LOG.debug("stdout: %s", stdout)
        INTEG_LOG.debug("stderr: %s", stderr)
        if memory_usage is None:
            memory_usage = []
        self.memory_usage = memory_usage

    @property
    def json(self):
        return json.loads(self.stdout)


def _escape_quotes(command):
    # For windows we have different rules for escaping.
    # First, double quotes must be escaped.
    command = command.replace('"', '\\"')
    # Second, single quotes do nothing, to quote a value we need
    # to use double quotes.
    command = command.replace("'", '"')
    return command


def aws(command, collect_memory=False, env_vars=None,
        wait_for_finish=True, input_data=None, input_file=None):
    """Run an aws command.

    This help function abstracts the differences of running the "aws"
    command on different platforms.

    If collect_memory is ``True`` the the Result object will have a list
    of memory usage taken at 2 second intervals.  The memory usage
    will be in bytes.

    If env_vars is None, this will set the environment variables
    to be used by the aws process.

    If wait_for_finish is False, then the Process object is returned
    to the caller.  It is then the caller's responsibility to ensure
    proper cleanup.  This can be useful if you want to test timeout's
    or how the CLI responds to various signals.

    :type input_data: string
    :param input_data: This string will be communicated to the process through
        the stdin of the process.  It essentially allows the user to
        avoid having to use a file handle to pass information to the process.
        Note that this string is not passed on creation of the process, but
        rather communicated to the process.

    :type input_file: a file handle
    :param input_file: This is a file handle that will act as the
        the stdin of the process immediately on creation.  Essentially
        any data written to the file will be read from stdin of the
        process. This is needed if you plan to stream data into stdin while
        collecting memory.
    """
    if platform.system() == 'Windows':
        command = _escape_quotes(command)
    if 'AWS_TEST_COMMAND' in os.environ:
        aws_command = os.environ['AWS_TEST_COMMAND']
    else:
        aws_command = 'python %s' % get_aws_cmd()
    full_command = '%s %s' % (aws_command, command)
    stdout_encoding = get_stdout_encoding()
    INTEG_LOG.debug("Running command: %s", full_command)
    env = os.environ.copy()
    if 'AWS_DEFAULT_REGION' not in env:
        env['AWS_DEFAULT_REGION'] = "us-east-1"
    if env_vars is not None:
        env = env_vars
    if input_file is None:
        input_file = PIPE
    process = Popen(full_command, stdout=PIPE, stderr=PIPE, stdin=input_file,
                    shell=True, env=env)
    if not wait_for_finish:
        return process
    memory = None
    if not collect_memory:
        kwargs = {}
        if input_data:
            kwargs = {'input': input_data}
        stdout, stderr = process.communicate(**kwargs)
    else:
        stdout, stderr, memory = _wait_and_collect_mem(process)
    return Result(process.returncode,
                  stdout.decode(stdout_encoding),
                  stderr.decode(stdout_encoding),
                  memory)


def get_stdout_encoding():
    encoding = getattr(sys.__stdout__, 'encoding', None)
    if encoding is None:
        encoding = 'utf-8'
    return encoding


def _wait_and_collect_mem(process):
    # We only know how to collect memory on mac/linux.
    if platform.system() == 'Darwin':
        get_memory = _get_memory_with_ps
    elif platform.system() == 'Linux':
        get_memory = _get_memory_with_ps
    else:
        raise ValueError(
            "Can't collect memory for process on platform %s." %
            platform.system())
    memory = []
    while process.poll() is None:
        try:
            current = get_memory(process.pid)
        except ProcessTerminatedError:
            # It's possible the process terminated between .poll()
            # and get_memory().
            break
        memory.append(current)
    stdout, stderr = process.communicate()
    return stdout, stderr, memory


def _get_memory_with_ps(pid):
    # It's probably possible to do with proc_pidinfo and ctypes on a Mac,
    # but we'll do it the easy way with parsing ps output.
    command_list = 'ps u -p'.split()
    command_list.append(str(pid))
    p = Popen(command_list, stdout=PIPE)
    stdout = p.communicate()[0]
    if not p.returncode == 0:
        raise ProcessTerminatedError(str(pid))
    else:
        # Get the RSS from output that looks like this:
        # USER       PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
        # user     47102   0.0  0.1  2437000   4496 s002  S+    7:04PM   0:00.12 python2.6
        return int(stdout.splitlines()[1].split()[5]) * 1024


class BaseS3CLICommand(unittest.TestCase):
    """Base class for aws s3 command.

    This contains convenience functions to make writing these tests easier
    and more streamlined.

    """
    _PUT_HEAD_SHARED_EXTRAS = [
        'SSECustomerAlgorithm',
        'SSECustomerKey',
        'SSECustomerKeyMD5',
        'RequestPayer',
    ]

    def setUp(self):
        self.files = FileCreator()
        self.session = botocore.session.get_session()
        self.regions = {}
        self.region = 'us-west-2'
        self.client = self.session.create_client('s3', region_name=self.region)
        self.extra_setup()

    def extra_setup(self):
        # Subclasses can use this to define extra setup steps.
        pass

    def tearDown(self):
        self.files.remove_all()
        self.extra_teardown()

    def extra_teardown(self):
        # Subclasses can use this to define extra teardown steps.
        pass

    def override_parser(self, **kwargs):
        factory = self.session.get_component('response_parser_factory')
        factory.set_parser_defaults(**kwargs)

    def create_client_for_bucket(self, bucket_name):
        region = self.regions.get(bucket_name, self.region)
        client = self.session.create_client('s3', region_name=region)
        return client

    def assert_key_contents_equal(self, bucket, key, expected_contents):
        self.wait_until_key_exists(bucket, key)
        if isinstance(expected_contents, BytesIO):
            expected_contents = expected_contents.getvalue().decode('utf-8')
        actual_contents = self.get_key_contents(bucket, key)
        # The contents can be huge so we try to give helpful error messages
        # without necessarily printing the actual contents.
        self.assertEqual(len(actual_contents), len(expected_contents))
        if actual_contents != expected_contents:
            self.fail("Contents for %s/%s do not match (but they "
                      "have the same length)" % (bucket, key))

    def delete_public_access_block(self, bucket_name):
        client = self.create_client_for_bucket(bucket_name)
        client.delete_public_access_block(
             Bucket=bucket_name
        )

    def create_bucket(self, name=None, region=None):
        if not region:
            region = self.region
        bucket_name = create_bucket(self.session, name, region)
        self.regions[bucket_name] = region
        self.addCleanup(self.delete_bucket, bucket_name)

        # Wait for the bucket to exist before letting it be used.
        self.wait_bucket_exists(bucket_name)
        self.delete_public_access_block(bucket_name)
        return bucket_name

    def put_object(self, bucket_name, key_name, contents='', extra_args=None):
        client = self.create_client_for_bucket(bucket_name)
        call_args = {
            'Bucket': bucket_name,
            'Key': key_name, 'Body': contents
        }
        if extra_args is not None:
            call_args.update(extra_args)
        response = client.put_object(**call_args)
        self.addCleanup(self.delete_key, bucket_name, key_name)
        extra_head_params = {}
        if extra_args:
            extra_head_params = dict(
                (k, v) for (k, v) in extra_args.items()
                if k in self._PUT_HEAD_SHARED_EXTRAS
            )
        self.wait_until_key_exists(
            bucket_name,
            key_name,
            extra_params=extra_head_params,
        )
        return response

    def delete_bucket(self, bucket_name, attempts=5, delay=5):
        self.remove_all_objects(bucket_name)
        client = self.create_client_for_bucket(bucket_name)

        # There's a chance that, even though the bucket has been used
        # several times, the delete will fail due to eventual consistency
        # issues.
        attempts_remaining = attempts
        while True:
            attempts_remaining -= 1
            try:
                client.delete_bucket(Bucket=bucket_name)
                break
            except client.exceptions.NoSuchBucket:
                if self.bucket_not_exists(bucket_name):
                    # Fast fail when the NoSuchBucket error is real.
                    break
                if attempts_remaining <= 0:
                    raise
                time.sleep(delay)

        self.regions.pop(bucket_name, None)

    def remove_all_objects(self, bucket_name):
        client = self.create_client_for_bucket(bucket_name)
        paginator = client.get_paginator('list_objects')
        pages = paginator.paginate(Bucket=bucket_name)
        key_names = []
        for page in pages:
            key_names += [obj['Key'] for obj in page.get('Contents', [])]
        for key_name in key_names:
            self.delete_key(bucket_name, key_name)

    def delete_key(self, bucket_name, key_name):
        client = self.create_client_for_bucket(bucket_name)
        response = client.delete_object(Bucket=bucket_name, Key=key_name)

    def get_key_contents(self, bucket_name, key_name):
        self.wait_until_key_exists(bucket_name, key_name)
        client = self.create_client_for_bucket(bucket_name)
        response = client.get_object(Bucket=bucket_name, Key=key_name)
        return response['Body'].read().decode('utf-8')

    def wait_bucket_exists(self, bucket_name, min_successes=3):
        client = self.create_client_for_bucket(bucket_name)
        waiter = client.get_waiter('bucket_exists')
        consistency_waiter = ConsistencyWaiter(
            min_successes=min_successes, delay_initial_poll=True)
        consistency_waiter.wait(
            lambda: waiter.wait(Bucket=bucket_name) is None
        )

    def bucket_not_exists(self, bucket_name):
        client = self.create_client_for_bucket(bucket_name)
        try:
            client.head_bucket(Bucket=bucket_name)
            return True
        except ClientError as error:
            if error.response.get('Code') == '404':
                return False
            raise

    def key_exists(self, bucket_name, key_name, min_successes=3):
        try:
            self.wait_until_key_exists(
                    bucket_name, key_name, min_successes=min_successes)
            return True
        except (ClientError, WaiterError):
            return False

    def key_not_exists(self, bucket_name, key_name, min_successes=3):
        try:
            self.wait_until_key_not_exists(
                    bucket_name, key_name, min_successes=min_successes)
            return True
        except (ClientError, WaiterError):
            return False

    def list_buckets(self):
        response = self.client.list_buckets()
        return response['Buckets']

    def content_type_for_key(self, bucket_name, key_name):
        parsed = self.head_object(bucket_name, key_name)
        return parsed['ContentType']

    def head_object(self, bucket_name, key_name):
        client = self.create_client_for_bucket(bucket_name)
        response = client.head_object(Bucket=bucket_name, Key=key_name)
        return response

    def wait_until_key_exists(self, bucket_name, key_name, extra_params=None,
                              min_successes=3):
        self._wait_for_key(bucket_name, key_name, extra_params,
                           min_successes, exists=True)

    def wait_until_key_not_exists(self, bucket_name, key_name, extra_params=None,
                                  min_successes=3):
        self._wait_for_key(bucket_name, key_name, extra_params,
                           min_successes, exists=False)

    def _wait_for_key(self, bucket_name, key_name, extra_params=None,
                      min_successes=3, exists=True):
        client = self.create_client_for_bucket(bucket_name)
        if exists:
            waiter = client.get_waiter('object_exists')
        else:
            waiter = client.get_waiter('object_not_exists')
        params = {'Bucket': bucket_name, 'Key': key_name}
        if extra_params is not None:
            params.update(extra_params)
        for _ in range(min_successes):
            waiter.wait(**params)

    def assert_no_errors(self, p):
        self.assertEqual(
            p.rc, 0,
            "Non zero rc (%s) received: %s" % (p.rc, p.stdout + p.stderr))
        self.assertNotIn("Error:", p.stderr)
        self.assertNotIn("failed:", p.stderr)
        self.assertNotIn("client error", p.stderr)
        self.assertNotIn("server error", p.stderr)


class StringIOWithFileNo(StringIO):
    def fileno(self):
        return 0


class TestEventHandler(object):
    def __init__(self, handler=None):
        self._handler = handler
        self._called = False
        self.__test__ = False

    @property
    def called(self):
        return self._called

    def handler(self, **kwargs):
        self._called = True
        if self._handler is not None:
            self._handler(**kwargs)


class ConsistencyWaiterException(Exception):
    pass


class ConsistencyWaiter(object):
    """
    A waiter class for some check to reach a consistent state.

    :type min_successes: int
    :param min_successes: The minimum number of successful check calls to
    treat the check as stable. Default of 1 success.

    :type max_attempts: int
    :param min_successes: The maximum number of times to attempt calling
    the check. Default of 20 attempts.

    :type delay: int
    :param delay: The number of seconds to delay the next API call after a
    failed check call. Default of 5 seconds.
    """
    def __init__(self, min_successes=1, max_attempts=20, delay=5,
                 delay_initial_poll=False):
        self.min_successes = min_successes
        self.max_attempts = max_attempts
        self.delay = delay
        self.delay_initial_poll = delay_initial_poll

    def wait(self, check, *args, **kwargs):
        """
        Wait until the check succeeds the configured number of times

        :type check: callable
        :param check: A callable that returns True or False to indicate
        if the check succeeded or failed.

        :type args: list
        :param args: Any ordered arguments to be passed to the check.

        :type kwargs: dict
        :param kwargs: Any keyword arguments to be passed to the check.
        """
        attempts = 0
        successes = 0
        if self.delay_initial_poll:
            time.sleep(self.delay)
        while attempts < self.max_attempts:
            attempts += 1
            if check(*args, **kwargs):
                successes += 1
                if successes >= self.min_successes:
                    return
            else:
                time.sleep(self.delay)
        fail_msg = self._fail_message(attempts, successes)
        raise ConsistencyWaiterException(fail_msg)

    def _fail_message(self, attempts, successes):
        format_args = (attempts, successes)
        return 'Failed after %s attempts, only had %s successes' % format_args


@contextlib.contextmanager
def cd(path):
    try:
        original_dir = os.getcwd()
        os.chdir(path)
        yield
    finally:
        os.chdir(original_dir)
