#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright 2013 Google Inc. 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.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License 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.
"""Main module for Google Cloud Storage command line tool."""

from __future__ import absolute_import

import ConfigParser
import datetime
import errno
import getopt
import logging
import os
import re
import signal
import socket
import sys
import textwrap
import traceback

# Load the gsutil version number and append it to boto.UserAgent so the value is
# set before anything instantiates boto. This has to run after THIRD_PARTY_DIR
# is modified (done in gsutil.py) but before any calls are made that would cause
# boto.s3.Connection to be loaded - otherwise the Connection class would end up
# with a static reference to the pre-modified version of the UserAgent field,
# so boto requests would not include gsutil/version# in the UserAgent string.
import boto
import gslib
# TODO: gsutil-beta: Cloud SDK scans for this string and performs
# substitution; ensure this works with both apitools and boto.
boto.UserAgent += ' gsutil/%s (%s)' % (gslib.VERSION, sys.platform)
if os.environ.get('CLOUDSDK_WRAPPER') == '1':
  boto.UserAgent += ' Cloud SDK Command Line Tool'
  if os.environ.get('CLOUDSDK_VERSION'):
    boto.UserAgent += ' %s' % os.environ.get('CLOUDSDK_VERSION')

# pylint: disable=g-bad-import-order
# pylint: disable=g-import-not-at-top
import httplib2
import oauth2client
from gslib import wildcard_iterator
from gslib.cloud_api import AccessDeniedException
from gslib.cloud_api import ArgumentException
from gslib.cloud_api import BadRequestException
from gslib.cloud_api import ProjectIdException
from gslib.cloud_api import ServiceException
from gslib.command_runner import CommandRunner
import gslib.exception
from gslib.exception import CommandException
import apitools.base.py.exceptions as apitools_exceptions
from gslib.util import CreateLock
from gslib.util import GetBotoConfigFileList
from gslib.util import GetCertsFile
from gslib.util import GetCleanupFiles
from gslib.util import GsutilStreamHandler
from gslib.util import ProxyInfoFromEnvironmentVar
from gslib.sig_handling import GetCaughtSignals
from gslib.sig_handling import InitializeSignalHandling
from gslib.sig_handling import RegisterSignalHandler

GSUTIL_CLIENT_ID = '909320924072.apps.googleusercontent.com'
# Google OAuth2 clients always have a secret, even if the client is an installed
# application/utility such as gsutil.  Of course, in such cases the "secret" is
# actually publicly known; security depends entirely on the secrecy of refresh
# tokens, which effectively become bearer tokens.
GSUTIL_CLIENT_NOTSOSECRET = 'p3RlpR10xMFh9ZXBS/ZNLYUu'
if os.environ.get('CLOUDSDK_WRAPPER') == '1':
  # Cloud SDK installs have a separate client ID / secret.
  GSUTIL_CLIENT_ID = '32555940559.apps.googleusercontent.com'
  GSUTIL_CLIENT_NOTSOSECRET = 'ZmssLNjJy2998hD4CTg2ejr2'

CONFIG_KEYS_TO_REDACT = ['proxy', 'proxy_port', 'proxy_user', 'proxy_pass']


# We don't use the oauth2 authentication plugin directly; importing it here
# ensures that it's loaded and available by default when an operation requiring
# authentication is performed.
try:
  # pylint: disable=unused-import,g-import-not-at-top
  import gcs_oauth2_boto_plugin
except ImportError:
  pass

DEBUG_WARNING = """
***************************** WARNING *****************************
*** You are running gsutil with debug output enabled.
*** Be aware that debug output includes authentication credentials.
*** Make sure to remove the value of the Authorization header for
*** each HTTP request printed to the console prior to posting to
*** a public medium such as a forum post or Stack Overflow.
***************************** WARNING *****************************
""".lstrip()

TRACE_WARNING = """
***************************** WARNING *****************************
*** You are running gsutil with trace output enabled.
*** Be aware that trace output includes authentication credentials
*** and may include the contents of any files accessed during the trace.
***************************** WARNING *****************************
""".lstrip()

HTTP_WARNING = """
***************************** WARNING *****************************
*** You are running gsutil with the "https_validate_certificates" config
*** variable set to False. This option should always be set to True in
*** production environments to protect against man-in-the-middle attacks,
*** and leaking of user data.
***************************** WARNING *****************************
""".lstrip()

debug = 0
test_exception_traces = False


# pylint: disable=unused-argument
def _CleanupSignalHandler(signal_num, cur_stack_frame):
  """Cleans up if process is killed with SIGINT, SIGQUIT or SIGTERM."""
  _Cleanup()


def _Cleanup():
  for fname in GetCleanupFiles():
    try:
      os.unlink(fname)
    except:  # pylint: disable=bare-except
      pass


def _OutputAndExit(message):
  """Outputs message and exists with code 1."""
  from gslib.util import UTF8  # pylint: disable=g-import-not-at-top
  if debug >= 2 or test_exception_traces:
    stack_trace = traceback.format_exc()
    err = ('DEBUG: Exception stack trace:\n    %s\n' %
           re.sub('\\n', '\n    ', stack_trace))
  else:
    err = '%s\n' % message
  try:
    sys.stderr.write(err.encode(UTF8))
  except UnicodeDecodeError:
    # Can happen when outputting invalid Unicode filenames.
    sys.stderr.write(err)
  sys.exit(1)


def _OutputUsageAndExit(command_runner):
  command_runner.RunNamedCommand('help')
  sys.exit(1)


class GsutilFormatter(logging.Formatter):
  """A logging.Formatter that supports logging microseconds (%f)."""

  def formatTime(self, record, datefmt=None):
    if datefmt:
      return datetime.datetime.fromtimestamp(record.created).strftime(datefmt)

    # Use default implementation if datefmt is not specified.
    return super(GsutilFormatter, self).formatTime(record, datefmt=datefmt)


def _ConfigureLogging(level=logging.INFO):
  """Similar to logging.basicConfig() except it always adds a handler."""
  log_format = '%(levelname)s %(asctime)s %(filename)s] %(message)s'
  date_format = '%m%d %H:%M:%S.%f'
  formatter = GsutilFormatter(fmt=log_format, datefmt=date_format)
  handler = GsutilStreamHandler()
  handler.setFormatter(formatter)
  root_logger = logging.getLogger()
  root_logger.addHandler(handler)
  root_logger.setLevel(level)


def main():
  InitializeSignalHandling()
  # Any modules used in initializing multiprocessing variables must be
  # imported after importing gslib.__main__.
  # pylint: disable=redefined-outer-name,g-import-not-at-top
  import gslib.boto_translation
  import gslib.command
  import gslib.util
  from gslib.util import BOTO_IS_SECURE
  from gslib.util import CERTIFICATE_VALIDATION_ENABLED
  # pylint: disable=unused-variable
  from gcs_oauth2_boto_plugin import oauth2_client
  from apitools.base.py import credentials_lib
  # pylint: enable=unused-variable
  from gslib.util import CheckMultiprocessingAvailableAndInit
  if CheckMultiprocessingAvailableAndInit().is_available:
    # These setup methods must be called, and, on Windows, they can only be
    # called from within an "if __name__ == '__main__':" block.
    gslib.command.InitializeMultiprocessingVariables()
    gslib.boto_translation.InitializeMultiprocessingVariables()
  else:
    gslib.command.InitializeThreadingVariables()

  # This needs to be done after gslib.util.InitializeMultiprocessingVariables(),
  # since otherwise we can't call gslib.util.CreateLock.
  try:
    # pylint: disable=unused-import,g-import-not-at-top
    import gcs_oauth2_boto_plugin
    gcs_oauth2_boto_plugin.oauth2_helper.SetFallbackClientIdAndSecret(
        GSUTIL_CLIENT_ID, GSUTIL_CLIENT_NOTSOSECRET)
    gcs_oauth2_boto_plugin.oauth2_helper.SetLock(CreateLock())
    credentials_lib.SetCredentialsCacheFileLock(CreateLock())
  except ImportError:
    pass

  global debug
  global test_exception_traces

  if not (2, 6) <= sys.version_info[:3] < (3,):
    raise gslib.exception.CommandException(
        'gsutil requires python 2.6 or 2.7.')

  # In gsutil 4.0 and beyond, we don't use the boto library for the JSON
  # API. However, we still store gsutil configuration data in the .boto
  # config file for compatibility with previous versions and user convenience.
  # Many users have a .boto configuration file from previous versions, and it
  # is useful to have all of the configuration for gsutil stored in one place.
  command_runner = CommandRunner()
  if not BOTO_IS_SECURE:
    raise CommandException('\n'.join(textwrap.wrap(
        'Your boto configuration has is_secure = False. Gsutil cannot be '
        'run this way, for security reasons.')))

  headers = {}
  parallel_operations = False
  quiet = False
  version = False
  debug = 0
  trace_token = None
  test_exception_traces = False

  # If user enters no commands just print the usage info.
  if len(sys.argv) == 1:
    sys.argv.append('help')

  # Change the default of the 'https_validate_certificates' boto option to
  # True (it is currently False in boto).
  if not boto.config.has_option('Boto', 'https_validate_certificates'):
    if not boto.config.has_section('Boto'):
      boto.config.add_section('Boto')
    boto.config.setbool('Boto', 'https_validate_certificates', True)

  gslib.util.certs_file_lock = CreateLock()
  for signal_num in GetCaughtSignals():
    RegisterSignalHandler(signal_num, _CleanupSignalHandler)
  GetCertsFile()

  try:
    try:
      opts, args = getopt.getopt(sys.argv[1:], 'dDvo:h:mq',
                                 ['debug', 'detailedDebug', 'version', 'option',
                                  'help', 'header', 'multithreaded', 'quiet',
                                  'testexceptiontraces', 'trace-token='])
    except getopt.GetoptError as e:
      _HandleCommandException(gslib.exception.CommandException(e.msg))
    for o, a in opts:
      if o in ('-d', '--debug'):
        # Passing debug=2 causes boto to include httplib header output.
        debug = 3
      elif o in ('-D', '--detailedDebug'):
        # We use debug level 3 to ask gsutil code to output more detailed
        # debug output. This is a bit of a hack since it overloads the same
        # flag that was originally implemented for boto use. And we use -DD
        # to ask for really detailed debugging (i.e., including HTTP payload).
        if debug == 3:
          debug = 4
        else:
          debug = 3
      elif o in ('-?', '--help'):
        _OutputUsageAndExit(command_runner)
      elif o in ('-h', '--header'):
        (hdr_name, _, hdr_val) = a.partition(':')
        if not hdr_name:
          _OutputUsageAndExit(command_runner)
        headers[hdr_name.lower()] = hdr_val
      elif o in ('-m', '--multithreaded'):
        parallel_operations = True
      elif o in ('-q', '--quiet'):
        quiet = True
      elif o in ('-v', '--version'):
        version = True
      elif o == '--trace-token':
        trace_token = a
      elif o == '--testexceptiontraces':  # Hidden flag for integration tests.
        test_exception_traces = True
      elif o in ('-o', '--option'):
        (opt_section_name, _, opt_value) = a.partition('=')
        if not opt_section_name:
          _OutputUsageAndExit(command_runner)
        (opt_section, _, opt_name) = opt_section_name.partition(':')
        if not opt_section or not opt_name:
          _OutputUsageAndExit(command_runner)
        if not boto.config.has_section(opt_section):
          boto.config.add_section(opt_section)
        boto.config.set(opt_section, opt_name, opt_value)
    httplib2.debuglevel = debug
    if trace_token:
      sys.stderr.write(TRACE_WARNING)
    if debug > 1:
      sys.stderr.write(DEBUG_WARNING)
    if debug >= 2:
      _ConfigureLogging(level=logging.DEBUG)
      command_runner.RunNamedCommand('ver', ['-l'])
      config_items = []
      try:
        config_items.extend(boto.config.items('Boto'))
        config_items.extend(boto.config.items('GSUtil'))
      except ConfigParser.NoSectionError:
        pass
      for i in xrange(len(config_items)):
        config_item_key = config_items[i][0]
        if config_item_key in CONFIG_KEYS_TO_REDACT:
          config_items[i] = (config_item_key, 'REDACTED')
      sys.stderr.write('Command being run: %s\n' % ' '.join(sys.argv))
      sys.stderr.write('config_file_list: %s\n' % GetBotoConfigFileList())
      sys.stderr.write('config: %s\n' % str(config_items))
    elif quiet:
      _ConfigureLogging(level=logging.WARNING)
    else:
      _ConfigureLogging(level=logging.INFO)
      # oauth2client uses info logging in places that would better
      # correspond to gsutil's debug logging (e.g., when refreshing
      # access tokens).
      oauth2client.client.logger.setLevel(logging.WARNING)

    if not CERTIFICATE_VALIDATION_ENABLED:
      sys.stderr.write(HTTP_WARNING)

    if version:
      command_name = 'version'
    elif not args:
      command_name = 'help'
    else:
      command_name = args[0]

    _CheckAndWarnForProxyDifferences()

    if os.environ.get('_ARGCOMPLETE', '0') == '1':
      return _PerformTabCompletion(command_runner)

    return _RunNamedCommandAndHandleExceptions(
        command_runner, command_name, args=args[1:], headers=headers,
        debug_level=debug, trace_token=trace_token,
        parallel_operations=parallel_operations)
  finally:
    _Cleanup()


def _CheckAndWarnForProxyDifferences():
  # If there are both boto config and environment variable config present for
  # proxies, unset the environment variable and warn if it differs.
  boto_port = boto.config.getint('Boto', 'proxy_port', 0)
  if boto.config.get('Boto', 'proxy', None) or boto_port:
    for proxy_env_var in ['http_proxy', 'https_proxy', 'HTTPS_PROXY']:
      if proxy_env_var in os.environ and os.environ[proxy_env_var]:
        differing_values = []
        proxy_info = ProxyInfoFromEnvironmentVar(proxy_env_var)
        if proxy_info.proxy_host != boto.config.get('Boto', 'proxy', None):
          differing_values.append(
              'Boto proxy host: "%s" differs from %s proxy host: "%s"' %
              (boto.config.get('Boto', 'proxy', None), proxy_env_var,
               proxy_info.proxy_host))
        if (proxy_info.proxy_user !=
            boto.config.get('Boto', 'proxy_user', None)):
          differing_values.append(
              'Boto proxy user: "%s" differs from %s proxy user: "%s"' %
              (boto.config.get('Boto', 'proxy_user', None), proxy_env_var,
               proxy_info.proxy_user))
        if (proxy_info.proxy_pass !=
            boto.config.get('Boto', 'proxy_pass', None)):
          differing_values.append(
              'Boto proxy password differs from %s proxy password' %
              proxy_env_var)
        # Only compare ports if at least one is present, since the
        # boto logic for selecting default ports has not yet executed.
        if ((proxy_info.proxy_port or boto_port) and
            proxy_info.proxy_port != boto_port):
          differing_values.append(
              'Boto proxy port: "%s" differs from %s proxy port: "%s"' %
              (boto_port, proxy_env_var, proxy_info.proxy_port))
        if differing_values:
          sys.stderr.write('\n'.join(textwrap.wrap(
              'WARNING: Proxy configuration is present in both the %s '
              'environment variable and boto configuration, but '
              'configuration differs. boto configuration proxy values will '
              'be used. Differences detected:' % proxy_env_var)))
          sys.stderr.write('\n%s\n' % '\n'.join(differing_values))
        # Regardless of whether the proxy configuration values matched,
        # delete the environment variable so as not to confuse boto.
        del os.environ[proxy_env_var]


def _HandleUnknownFailure(e):
  # Called if we fall through all known/handled exceptions.
  _OutputAndExit('Failure: %s.' % e)


def _HandleCommandException(e):
  if e.informational:
    _OutputAndExit(e.reason)
  else:
    _OutputAndExit('CommandException: %s' % e.reason)


# pylint: disable=unused-argument
def _HandleControlC(signal_num, cur_stack_frame):
  """Called when user hits ^C.

  This function prints a brief message instead of the normal Python stack trace
  (unless -D option is used).

  Args:
    signal_num: Signal that was caught.
    cur_stack_frame: Unused.
  """
  if debug >= 2:
    stack_trace = ''.join(traceback.format_list(traceback.extract_stack()))
    _OutputAndExit(
        'DEBUG: Caught signal %d - Exception stack trace:\n'
        '    %s' % (signal_num, re.sub('\\n', '\n    ', stack_trace)))
  else:
    _OutputAndExit('Caught signal %d - exiting' % signal_num)


def _HandleSigQuit(signal_num, cur_stack_frame):
  """Called when user hits ^\\, so we can force breakpoint a running gsutil."""
  import pdb  # pylint: disable=g-import-not-at-top
  pdb.set_trace()


def _ConstructAccountProblemHelp(reason):
  """Constructs a help string for an access control error.

  Args:
    reason: e.reason string from caught exception.

  Returns:
    Contructed help text.
  """
  default_project_id = boto.config.get_value('GSUtil', 'default_project_id')
  # pylint: disable=line-too-long, g-inconsistent-quotes
  acct_help = (
      "Your request resulted in an AccountProblem (403) error. Usually this "
      "happens if you attempt to create a bucket without first having "
      "enabled billing for the project you are using. Please ensure billing is "
      "enabled for your project by following the instructions at "
      "`Google Developers Console<https://developers.google.com/console/help/billing>`. ")
  if default_project_id:
    acct_help += (
        "In the project overview, ensure that the Project Number listed for "
        "your project matches the project ID (%s) from your boto config file. "
        % default_project_id)
  acct_help += (
      "If the above doesn't resolve your AccountProblem, please send mail to "
      "gs-team@google.com requesting assistance, noting the exact command you "
      "ran, the fact that you received a 403 AccountProblem error, and your "
      "project ID. Please do not post your project ID on StackOverflow. "
      "Note: It's possible to use Google Cloud Storage without enabling "
      "billing if you're only listing or reading objects for which you're "
      "authorized, or if you're uploading objects to a bucket billed to a "
      "project that has billing enabled. But if you're attempting to create "
      "buckets or upload objects to a bucket owned by your own project, you "
      "must first enable billing for that project.")
  return acct_help


def _CheckAndHandleCredentialException(e, args):
  # Provide detail to users who have no boto config file (who might previously
  # have been using gsutil only for accessing publicly readable buckets and
  # objects).
  # pylint: disable=g-import-not-at-top
  from gslib.util import HasConfiguredCredentials
  if (not HasConfiguredCredentials() and
      not boto.config.get_value('Tests', 'bypass_anonymous_access_warning',
                                False)):
    # The check above allows tests to assert that we get a particular,
    # expected failure, rather than always encountering this error message
    # when there are no configured credentials. This allows tests to
    # simulate a second user without permissions, without actually requiring
    # two separate configured users.
    if os.environ.get('CLOUDSDK_WRAPPER') == '1':
      _OutputAndExit('\n'.join(textwrap.wrap(
          'You are attempting to access protected data with no configured '
          'credentials. Please visit '
          'https://cloud.google.com/console#/project and sign up for an '
          'account, and then run the "gcloud auth login" command to '
          'configure gsutil to use these credentials.')))
    else:
      _OutputAndExit('\n'.join(textwrap.wrap(
          'You are attempting to access protected data with no configured '
          'credentials. Please visit '
          'https://cloud.google.com/console#/project and sign up for an '
          'account, and then run the "gsutil config" command to configure '
          'gsutil to use these credentials.')))
  elif (e.reason and
        (e.reason == 'AccountProblem' or e.reason == 'Account disabled.' or
         'account for the specified project has been disabled' in e.reason)
        and ','.join(args).find('gs://') != -1):
    _OutputAndExit('\n'.join(textwrap.wrap(
        _ConstructAccountProblemHelp(e.reason))))


def _RunNamedCommandAndHandleExceptions(command_runner, command_name, args=None,
                                        headers=None, debug_level=0,
                                        trace_token=None,
                                        parallel_operations=False):
  """Runs the command with the given command runner and arguments."""
  # pylint: disable=g-import-not-at-top
  from gslib.util import GetConfigFilePath
  from gslib.util import IS_WINDOWS
  from gslib.util import IsRunningInteractively
  try:
    # Catch ^C so we can print a brief message instead of the normal Python
    # stack trace. Register as a final signal handler because this handler kills
    # the main gsutil process (so it must run last).
    RegisterSignalHandler(signal.SIGINT, _HandleControlC, is_final_handler=True)
    # Catch ^\ so we can force a breakpoint in a running gsutil.
    if not IS_WINDOWS:
      RegisterSignalHandler(signal.SIGQUIT, _HandleSigQuit)
    return command_runner.RunNamedCommand(command_name, args, headers,
                                          debug_level, trace_token,
                                          parallel_operations)
  except AttributeError as e:
    if str(e).find('secret_access_key') != -1:
      _OutputAndExit('Missing credentials for the given URI(s). Does your '
                     'boto config file contain all needed credentials?')
    else:
      _OutputAndExit(str(e))
  except gslib.exception.CommandException as e:
    _HandleCommandException(e)
  except getopt.GetoptError as e:
    _HandleCommandException(gslib.exception.CommandException(e.msg))
  except boto.exception.InvalidUriError as e:
    _OutputAndExit('InvalidUriError: %s.' % e.message)
  except gslib.exception.InvalidUrlError as e:
    _OutputAndExit('InvalidUrlError: %s.' % e.message)
  except boto.auth_handler.NotReadyToAuthenticate:
    _OutputAndExit('NotReadyToAuthenticate')
  except OSError as e:
    _OutputAndExit('OSError: %s.' % e.strerror)
  except IOError as e:
    if (e.errno == errno.EPIPE or (IS_WINDOWS and e.errno == errno.EINVAL)
        and not IsRunningInteractively()):
      # If we get a pipe error, this just means that the pipe to stdout or
      # stderr is broken. This can happen if the user pipes gsutil to a command
      # that doesn't use the entire output stream. Instead of raising an error,
      # just swallow it up and exit cleanly.
      sys.exit(0)
    else:
      raise
  except wildcard_iterator.WildcardException as e:
    _OutputAndExit(e.reason)
  except ProjectIdException as e:
    _OutputAndExit(
        'You are attempting to perform an operation that requires a '
        'project id, with none configured. Please re-run '
        'gsutil config and make sure to follow the instructions for '
        'finding and entering your default project id.')
  except BadRequestException as e:
    if e.reason == 'MissingSecurityHeader':
      _CheckAndHandleCredentialException(e, args)
    _OutputAndExit(e)
  except AccessDeniedException as e:
    _CheckAndHandleCredentialException(e, args)
    _OutputAndExit(e)
  except ArgumentException as e:
    _OutputAndExit(e)
  except ServiceException as e:
    _OutputAndExit(e)
  except apitools_exceptions.HttpError as e:
    # These should usually be retried by the underlying implementation or
    # wrapped by CloudApi ServiceExceptions, but if we do get them,
    # print something useful.
    _OutputAndExit('HttpError: %s, %s' % (getattr(e.response, 'status', ''),
                                          e.content or ''))
  except socket.error as e:
    if e.args[0] == errno.EPIPE:
      # Retrying with a smaller file (per suggestion below) works because
      # the library code send loop (in boto/s3/key.py) can get through the
      # entire file and then request the HTTP response before the socket
      # gets closed and the response lost.
      _OutputAndExit(
          'Got a "Broken pipe" error. This can happen to clients using Python '
          '2.x, when the server sends an error response and then closes the '
          'socket (see http://bugs.python.org/issue5542). If you are trying to '
          'upload a large object you might retry with a small (say 200k) '
          'object, and see if you get a more specific error code.'
      )
    else:
      _HandleUnknownFailure(e)
  except Exception as e:
    # Check for two types of errors related to service accounts. These errors
    # appear to be the same except for their messages, but they are caused by
    # different problems and both have unhelpful error messages. Moreover,
    # the error type belongs to PyOpenSSL, which is not necessarily installed.
    if 'mac verify failure' in str(e):
      _OutputAndExit(
          'Encountered an error while refreshing access token. '
          'If you are using a service account,\nplease verify that the '
          'gs_service_key_file_password field in your config file,'
          '\n%s, is correct.' % GetConfigFilePath())
    elif 'asn1 encoding routines' in str(e):
      _OutputAndExit(
          'Encountered an error while refreshing access token. '
          'If you are using a service account,\nplease verify that the '
          'gs_service_key_file field in your config file,\n%s, is correct.'
          % GetConfigFilePath())
    _HandleUnknownFailure(e)


def _PerformTabCompletion(command_runner):
  """Performs gsutil-specific tab completion for the shell."""
  # argparse and argcomplete are bundled with the Google Cloud SDK.
  # When gsutil is invoked from the Google Cloud SDK, both should be available.
  try:
    import argcomplete
    import argparse
  except ImportError as e:
    _OutputAndExit('A library required for performing tab completion was'
                   ' not found.\nCause: %s' % e)
  parser = argparse.ArgumentParser(add_help=False)
  subparsers = parser.add_subparsers()
  command_runner.ConfigureCommandArgumentParsers(subparsers)
  argcomplete.autocomplete(parser, exit_method=sys.exit)

  return 0

if __name__ == '__main__':
  sys.exit(main())