"""Certbot command line argument & config processing."""
# pylint: disable=too-many-lines
from __future__ import print_function
import argparse
import copy
import glob
import logging
import logging.handlers
import os
import sys

import configargparse
import six
import zope.component

from zope.interface import interfaces as zope_interfaces

from acme import challenges

import certbot

from certbot import constants
from certbot import crypto_util
from certbot import errors
from certbot import hooks
from certbot import interfaces
from certbot import util

from certbot.display import util as display_util
from certbot.plugins import disco as plugins_disco
import certbot.plugins.selection as plugin_selection

logger = logging.getLogger(__name__)

# Global, to save us from a lot of argument passing within the scope of this module
helpful_parser = None

# For help strings, figure out how the user ran us.
# When invoked from letsencrypt-auto, sys.argv[0] is something like:
# "/home/user/.local/share/certbot/bin/certbot"
# Note that this won't work if the user set VENV_PATH or XDG_DATA_HOME before
# running letsencrypt-auto (and sudo stops us from seeing if they did), so it
# should only be used for purposes where inability to detect letsencrypt-auto
# fails safely

LEAUTO = "letsencrypt-auto"
if "CERTBOT_AUTO" in os.environ:
    # if we're here, this is probably going to be certbot-auto, unless the
    # user saved the script under a different name
    LEAUTO = os.path.basename(os.environ["CERTBOT_AUTO"])

old_path_fragment = os.path.join(".local", "share", "letsencrypt")
new_path_prefix = os.path.abspath(os.path.join(os.sep, "opt",
                                               "eff.org", "certbot", "venv"))
if old_path_fragment in sys.argv[0] or sys.argv[0].startswith(new_path_prefix):
    cli_command = LEAUTO
else:
    cli_command = "certbot"

# Argparse's help formatting has a lot of unhelpful peculiarities, so we want
# to replace as much of it as we can...

# This is the stub to include in help generated by argparse
SHORT_USAGE = """
  {0} [SUBCOMMAND] [options] [-d DOMAIN] [-d DOMAIN] ...

Certbot can obtain and install HTTPS/TLS/SSL certificates.  By default,
it will attempt to use a webserver both for obtaining and installing the
certificate. """.format(cli_command)

# This section is used for --help and --help all ; it needs information
# about installed plugins to be fully formatted
COMMAND_OVERVIEW = """The most common SUBCOMMANDS and flags are:

obtain, install, and renew certificates:
    (default) run   Obtain & install a certificate in your current webserver
    certonly        Obtain or renew a certificate, but do not install it
    renew           Renew all previously obtained certificates that are near expiry
    enhance         Add security enhancements to your existing configuration
   -d DOMAINS       Comma-separated list of domains to obtain a certificate for

  %s
  --standalone      Run a standalone webserver for authentication
  %s
  --webroot         Place files in a server's webroot folder for authentication
  --manual          Obtain certificates interactively, or using shell script hooks

   -n               Run non-interactively
  --test-cert       Obtain a test certificate from a staging server
  --dry-run         Test "renew" or "certonly" without saving any certificates to disk

manage certificates:
    certificates    Display information about certificates you have from Certbot
    revoke          Revoke a certificate (supply --cert-path)
    delete          Delete a certificate

manage your account with Let's Encrypt:
    register        Create a Let's Encrypt ACME account
  --agree-tos       Agree to the ACME server's Subscriber Agreement
   -m EMAIL         Email address for important account notifications
"""

# This is the short help for certbot --help, where we disable argparse
# altogether
HELP_USAGE = """
More detailed help:

  -h, --help [TOPIC]    print this message, or detailed help on a topic;
                        the available TOPICS are:

   all, automation, commands, paths, security, testing, or any of the
   subcommands or plugins (certonly, renew, install, register, nginx,
   apache, standalone, webroot, etc.)
"""


# These argparse parameters should be removed when detecting defaults.
ARGPARSE_PARAMS_TO_REMOVE = ("const", "nargs", "type",)


# These sets are used when to help detect options set by the user.
EXIT_ACTIONS = set(("help", "version",))


ZERO_ARG_ACTIONS = set(("store_const", "store_true",
                        "store_false", "append_const", "count",))


# Maps a config option to a set of config options that may have modified it.
# This dictionary is used recursively, so if A modifies B and B modifies C,
# it is determined that C was modified by the user if A was modified.
VAR_MODIFIERS = {"account": set(("server",)),
                 "renew_hook": set(("deploy_hook",)),
                 "server": set(("dry_run", "staging",)),
                 "webroot_map": set(("webroot_path",))}


def report_config_interaction(modified, modifiers):
    """Registers config option interaction to be checked by set_by_cli.

    This function can be called by during the __init__ or
    add_parser_arguments methods of plugins to register interactions
    between config options.

    :param modified: config options that can be modified by modifiers
    :type modified: iterable or str (string_types)
    :param modifiers: config options that modify modified
    :type modifiers: iterable or str (string_types)

    """
    if isinstance(modified, six.string_types):
        modified = (modified,)
    if isinstance(modifiers, six.string_types):
        modifiers = (modifiers,)

    for var in modified:
        VAR_MODIFIERS.setdefault(var, set()).update(modifiers)


def possible_deprecation_warning(config):
    "A deprecation warning for users with the old, not-self-upgrading letsencrypt-auto."
    if cli_command != LEAUTO:
        return
    if config.no_self_upgrade:
        # users setting --no-self-upgrade might be hanging on a client version like 0.3.0
        # or 0.5.0 which is the new script, but doesn't set CERTBOT_AUTO; they don't
        # need warnings
        return
    if "CERTBOT_AUTO" not in os.environ:
        logger.warning("You are running with an old copy of letsencrypt-auto that does "
            "not receive updates, and is less reliable than more recent versions. "
            "We recommend upgrading to the latest certbot-auto script, or using native "
            "OS packages.")
        logger.debug("Deprecation warning circumstances: %s / %s", sys.argv[0], os.environ)


class _Default(object):
    """A class to use as a default to detect if a value is set by a user"""

    def __bool__(self):
        return False

    def __eq__(self, other):
        return isinstance(other, _Default)

    def __hash__(self):
        return id(_Default)

    def __nonzero__(self):
        return self.__bool__()


def set_by_cli(var):
    """
    Return True if a particular config variable has been set by the user
    (CLI or config file) including if the user explicitly set it to the
    default.  Returns False if the variable was assigned a default value.
    """
    detector = set_by_cli.detector
    if detector is None:
        # Setup on first run: `detector` is a weird version of config in which
        # the default value of every attribute is wrangled to be boolean-false
        plugins = plugins_disco.PluginsRegistry.find_all()
        # reconstructed_args == sys.argv[1:], or whatever was passed to main()
        reconstructed_args = helpful_parser.args + [helpful_parser.verb]
        detector = set_by_cli.detector = prepare_and_parse_args(
            plugins, reconstructed_args, detect_defaults=True)
        # propagate plugin requests: eg --standalone modifies config.authenticator
        detector.authenticator, detector.installer = (
            plugin_selection.cli_plugin_requests(detector))

    if not isinstance(getattr(detector, var), _Default):
        logger.debug("Var %s=%s (set by user).", var, getattr(detector, var))
        return True

    for modifier in VAR_MODIFIERS.get(var, []):
        if set_by_cli(modifier):
            logger.debug("Var %s=%s (set by user).",
                var, VAR_MODIFIERS.get(var, []))
            return True

    return False
# static housekeeping var
set_by_cli.detector = None  # type: ignore


def has_default_value(option, value):
    """Does option have the default value?

    If the default value of option is not known, False is returned.

    :param str option: configuration variable being considered
    :param value: value of the configuration variable named option

    :returns: True if option has the default value, otherwise, False
    :rtype: bool

    """
    return (option in helpful_parser.defaults and
            helpful_parser.defaults[option] == value)


def option_was_set(option, value):
    """Was option set by the user or does it differ from the default?

    :param str option: configuration variable being considered
    :param value: value of the configuration variable named option

    :returns: True if the option was set, otherwise, False
    :rtype: bool

    """
    return set_by_cli(option) or not has_default_value(option, value)


def argparse_type(variable):
    "Return our argparse type function for a config variable (default: str)"
    # pylint: disable=protected-access
    for action in helpful_parser.parser._actions:
        if action.type is not None and action.dest == variable:
            return action.type
    return str

def read_file(filename, mode="rb"):
    """Returns the given file's contents.

    :param str filename: path to file
    :param str mode: open mode (see `open`)

    :returns: absolute path of filename and its contents
    :rtype: tuple

    :raises argparse.ArgumentTypeError: File does not exist or is not readable.

    """
    try:
        filename = os.path.abspath(filename)
        return filename, open(filename, mode).read()
    except IOError as exc:
        raise argparse.ArgumentTypeError(exc.strerror)


def flag_default(name):
    """Default value for CLI flag."""
    # XXX: this is an internal housekeeping notion of defaults before
    # argparse has been set up; it is not accurate for all flags.  Call it
    # with caution.  Plugin defaults are missing, and some things are using
    # defaults defined in this file, not in constants.py :(
    return copy.deepcopy(constants.CLI_DEFAULTS[name])


def config_help(name, hidden=False):
    """Extract the help message for an `.IConfig` attribute."""
    if hidden:
        return argparse.SUPPRESS
    else:
        return interfaces.IConfig[name].__doc__


class HelpfulArgumentGroup(object):
    """Emulates an argparse group for use with HelpfulArgumentParser.

    This class is used in the add_group method of HelpfulArgumentParser.
    Command line arguments can be added to the group, but help
    suppression and default detection is applied by
    HelpfulArgumentParser when necessary.

    """
    def __init__(self, helpful_arg_parser, topic):
        self._parser = helpful_arg_parser
        self._topic = topic

    def add_argument(self, *args, **kwargs):
        """Add a new command line argument to the argument group."""
        self._parser.add(self._topic, *args, **kwargs)

class CustomHelpFormatter(argparse.HelpFormatter):
    """This is a clone of ArgumentDefaultsHelpFormatter, with bugfixes.

    In particular we fix https://bugs.python.org/issue28742
    """

    def _get_help_string(self, action):
        helpstr = action.help
        if '%(default)' not in action.help and '(default:' not in action.help:
            if action.default != argparse.SUPPRESS:
                defaulting_nargs = [argparse.OPTIONAL, argparse.ZERO_OR_MORE]
                if action.option_strings or action.nargs in defaulting_nargs:
                    helpstr += ' (default: %(default)s)'
        return helpstr

# The attributes here are:
# short: a string that will be displayed by "certbot -h commands"
# opts:  a string that heads the section of flags with which this command is documented,
#        both for "certbot -h SUBCOMMAND" and "certbot -h all"
# usage: an optional string that overrides the header of "certbot -h SUBCOMMAND"
VERB_HELP = [
    ("run (default)", {
        "short": "Obtain/renew a certificate, and install it",
        "opts": "Options for obtaining & installing certificates",
        "usage": SHORT_USAGE.replace("[SUBCOMMAND]", ""),
        "realname": "run"
    }),
    ("certonly", {
        "short": "Obtain or renew a certificate, but do not install it",
        "opts": "Options for modifying how a certificate is obtained",
        "usage": ("\n\n  certbot certonly [options] [-d DOMAIN] [-d DOMAIN] ...\n\n"
                  "This command obtains a TLS/SSL certificate without installing it anywhere.")
    }),
    ("renew", {
        "short": "Renew all certificates (or one specified with --cert-name)",
        "opts": ("The 'renew' subcommand will attempt to renew all"
                 " certificates (or more precisely, certificate lineages) you have"
                 " previously obtained if they are close to expiry, and print a"
                 " summary of the results. By default, 'renew' will reuse the options"
                 " used to create obtain or most recently successfully renew each"
                 " certificate lineage. You can try it with `--dry-run` first. For"
                 " more fine-grained control, you can renew individual lineages with"
                 " the `certonly` subcommand. Hooks are available to run commands"
                 " before and after renewal; see"
                 " https://certbot.eff.org/docs/using.html#renewal for more"
                 " information on these."),
        "usage": "\n\n  certbot renew [--cert-name CERTNAME] [options]\n\n"
    }),
    ("certificates", {
        "short": "List certificates managed by Certbot",
        "opts": "List certificates managed by Certbot",
        "usage": ("\n\n  certbot certificates [options] ...\n\n"
                  "Print information about the status of certificates managed by Certbot.")
    }),
    ("delete", {
        "short": "Clean up all files related to a certificate",
        "opts": "Options for deleting a certificate",
        "usage": "\n\n  certbot delete --cert-name CERTNAME\n\n"
    }),
    ("revoke", {
        "short": "Revoke a certificate specified with --cert-path",
        "opts": "Options for revocation of certificates",
        "usage": "\n\n  certbot revoke --cert-path /path/to/fullchain.pem [options]\n\n"
    }),
    ("register", {
        "short": "Register for account with Let's Encrypt / other ACME server",
        "opts": "Options for account registration & modification",
        "usage": "\n\n  certbot register --email user@example.com [options]\n\n"
    }),
    ("unregister", {
        "short": "Irrevocably deactivate your account",
        "opts": "Options for account deactivation.",
        "usage": "\n\n  certbot unregister [options]\n\n"
    }),
    ("install", {
        "short": "Install an arbitrary certificate in a server",
        "opts": "Options for modifying how a certificate is deployed",
        "usage": "\n\n  certbot install --cert-path /path/to/fullchain.pem "
        " --key-path /path/to/private-key [options]\n\n"
    }),
    ("config_changes", {
        "short": "Show changes that Certbot has made to server configurations",
        "opts": "Options for controlling which changes are displayed",
        "usage": "\n\n  certbot config_changes --num NUM [options]\n\n"
    }),
    ("rollback", {
        "short": "Roll back server conf changes made during certificate installation",
        "opts": "Options for rolling back server configuration changes",
        "usage": "\n\n  certbot rollback --checkpoints 3 [options]\n\n"
    }),
    ("plugins", {
        "short": "List plugins that are installed and available on your system",
        "opts": 'Options for for the "plugins" subcommand',
        "usage": "\n\n  certbot plugins [options]\n\n"
    }),
    ("update_symlinks", {
        "short": "Recreate symlinks in your /etc/letsencrypt/live/ directory",
        "opts": ("Recreates certificate and key symlinks in {0}, if you changed them by hand "
                 "or edited a renewal configuration file".format(
                  os.path.join(flag_default("config_dir"), "live"))),
        "usage": "\n\n  certbot update_symlinks [options]\n\n"
    }),
    ("enhance", {
        "short": "Add security enhancements to your existing configuration",
        "opts": ("Helps to harden the TLS configration by adding security enhancements "
                 "to already existing configuration."),
        "usage": "\n\n  certbot enhance [options]\n\n"
    }),

]
# VERB_HELP is a list in order to preserve order, but a dict is sometimes useful
VERB_HELP_MAP = dict(VERB_HELP)


class HelpfulArgumentParser(object):
    """Argparse Wrapper.

    This class wraps argparse, adding the ability to make --help less
    verbose, and request help on specific subcategories at a time, eg
    'certbot --help security' for security options.

    """


    def __init__(self, args, plugins, detect_defaults=False):
        from certbot import main
        self.VERBS = {
            "auth": main.certonly,
            "certonly": main.certonly,
            "config_changes": main.config_changes,
            "run": main.run,
            "install": main.install,
            "plugins": main.plugins_cmd,
            "register": main.register,
            "unregister": main.unregister,
            "renew": main.renew,
            "revoke": main.revoke,
            "rollback": main.rollback,
            "everything": main.run,
            "update_symlinks": main.update_symlinks,
            "certificates": main.certificates,
            "delete": main.delete,
            "enhance": main.enhance,
        }

        # Get notification function for printing
        try:
            self.notify = zope.component.getUtility(
                interfaces.IDisplay).notification
        except zope_interfaces.ComponentLookupError:
            self.notify = display_util.NoninteractiveDisplay(
                sys.stdout).notification


        # List of topics for which additional help can be provided
        HELP_TOPICS = ["all", "security", "paths", "automation", "testing"]
        HELP_TOPICS += list(self.VERBS) + self.COMMANDS_TOPICS + ["manage"]

        plugin_names = list(plugins)
        self.help_topics = HELP_TOPICS + plugin_names + [None]

        self.detect_defaults = detect_defaults
        self.args = args

        if self.args and self.args[0] == 'help':
            self.args[0] = '--help'

        self.determine_verb()
        help1 = self.prescan_for_flag("-h", self.help_topics)
        help2 = self.prescan_for_flag("--help", self.help_topics)
        if isinstance(help1, bool) and isinstance(help2, bool):
            self.help_arg = help1 or help2
        else:
            self.help_arg = help1 if isinstance(help1, six.string_types) else help2

        short_usage = self._usage_string(plugins, self.help_arg)

        self.visible_topics = self.determine_help_topics(self.help_arg)
        self.groups = {}       # elements are added by .add_group()
        self.defaults = {}     # elements are added by .parse_args()

        self.parser = configargparse.ArgParser(
            prog="certbot",
            usage=short_usage,
            formatter_class=CustomHelpFormatter,
            args_for_setting_config_path=["-c", "--config"],
            default_config_files=flag_default("config_files"),
            config_arg_help_message="path to config file (default: {0})".format(
                " and ".join(flag_default("config_files"))))

        # This is the only way to turn off overly verbose config flag documentation
        self.parser._add_config_file_help = False  # pylint: disable=protected-access

    # Help that are synonyms for --help subcommands
    COMMANDS_TOPICS = ["command", "commands", "subcommand", "subcommands", "verbs"]
    def _list_subcommands(self):
        longest = max(len(v) for v in VERB_HELP_MAP.keys())

        text = "The full list of available SUBCOMMANDS is:\n\n"
        for verb, props in sorted(VERB_HELP):
            doc = props.get("short", "")
            text += '{0:<{length}}     {1}\n'.format(verb, doc, length=longest)

        text += "\nYou can get more help on a specific subcommand with --help SUBCOMMAND\n"
        return text

    def _usage_string(self, plugins, help_arg):
        """Make usage strings late so that plugins can be initialised late

        :param plugins: all discovered plugins
        :param help_arg: False for none; True for --help; "TOPIC" for --help TOPIC
        :rtype: str
        :returns: a short usage string for the top of --help TOPIC)
        """
        if "nginx" in plugins:
            nginx_doc = "--nginx           Use the Nginx plugin for authentication & installation"
        else:
            nginx_doc = "(the certbot nginx plugin is not installed)"
        if "apache" in plugins:
            apache_doc = "--apache          Use the Apache plugin for authentication & installation"
        else:
            apache_doc = "(the certbot apache plugin is not installed)"

        usage = SHORT_USAGE
        if help_arg == True:
            self.notify(usage + COMMAND_OVERVIEW % (apache_doc, nginx_doc) + HELP_USAGE)
            sys.exit(0)
        elif help_arg in self.COMMANDS_TOPICS:
            self.notify(usage + self._list_subcommands())
            sys.exit(0)
        elif help_arg == "all":
            # if we're doing --help all, the OVERVIEW is part of the SHORT_USAGE at
            # the top; if we're doing --help someothertopic, it's OT so it's not
            usage += COMMAND_OVERVIEW % (apache_doc, nginx_doc)
        else:
            custom = VERB_HELP_MAP.get(help_arg, {}).get("usage", None)
            usage = custom if custom else usage

        return usage

    def remove_config_file_domains_for_renewal(self, parsed_args):
        """Make "certbot renew" safe if domains are set in cli.ini."""
        # Works around https://github.com/certbot/certbot/issues/4096
        if self.verb == "renew":
            for source, flags in self.parser._source_to_settings.items(): # pylint: disable=protected-access
                if source.startswith("config_file") and "domains" in flags:
                    parsed_args.domains = _Default() if self.detect_defaults else []

    def parse_args(self):
        """Parses command line arguments and returns the result.

        :returns: parsed command line arguments
        :rtype: argparse.Namespace

        """
        parsed_args = self.parser.parse_args(self.args)
        parsed_args.func = self.VERBS[self.verb]
        parsed_args.verb = self.verb

        self.remove_config_file_domains_for_renewal(parsed_args)

        if self.detect_defaults:
            return parsed_args

        self.defaults = dict((key, copy.deepcopy(self.parser.get_default(key)))
                             for key in vars(parsed_args))

        # Do any post-parsing homework here

        if self.verb == "renew":
            if parsed_args.force_interactive:
                raise errors.Error(
                    "{0} cannot be used with renew".format(
                        constants.FORCE_INTERACTIVE_FLAG))
            parsed_args.noninteractive_mode = True

        if parsed_args.force_interactive and parsed_args.noninteractive_mode:
            raise errors.Error(
                "Flag for non-interactive mode and {0} conflict".format(
                    constants.FORCE_INTERACTIVE_FLAG))

        if parsed_args.staging or parsed_args.dry_run:
            self.set_test_server(parsed_args)

        if parsed_args.csr:
            self.handle_csr(parsed_args)

        if parsed_args.must_staple:
            parsed_args.staple = True

        if parsed_args.validate_hooks:
            hooks.validate_hooks(parsed_args)

        if parsed_args.allow_subset_of_names:
            if any(util.is_wildcard_domain(d) for d in parsed_args.domains):
                raise errors.Error("Using --allow-subset-of-names with a"
                                   " wildcard domain is not supported.")

        possible_deprecation_warning(parsed_args)

        return parsed_args

    def set_test_server(self, parsed_args):
        """We have --staging/--dry-run; perform sanity check and set config.server"""

        if parsed_args.server not in (flag_default("server"), constants.STAGING_URI):
            conflicts = ["--staging"] if parsed_args.staging else []
            conflicts += ["--dry-run"] if parsed_args.dry_run else []
            raise errors.Error("--server value conflicts with {0}".format(
                " and ".join(conflicts)))

        parsed_args.server = constants.STAGING_URI

        if parsed_args.dry_run:
            if self.verb not in ["certonly", "renew"]:
                raise errors.Error("--dry-run currently only works with the "
                                   "'certonly' or 'renew' subcommands (%r)" % self.verb)
            parsed_args.break_my_certs = parsed_args.staging = True
            if glob.glob(os.path.join(parsed_args.config_dir, constants.ACCOUNTS_DIR, "*")):
                # The user has a prod account, but might not have a staging
                # one; we don't want to start trying to perform interactive registration
                parsed_args.tos = True
                parsed_args.register_unsafely_without_email = True

    def handle_csr(self, parsed_args):
        """Process a --csr flag."""
        if parsed_args.verb != "certonly":
            raise errors.Error("Currently, a CSR file may only be specified "
                               "when obtaining a new or replacement "
                               "via the certonly command. Please try the "
                               "certonly command instead.")
        if parsed_args.allow_subset_of_names:
            raise errors.Error("--allow-subset-of-names cannot be used with --csr")

        csrfile, contents = parsed_args.csr[0:2]
        typ, csr, domains = crypto_util.import_csr_file(csrfile, contents)

        # This is not necessary for webroot to work, however,
        # obtain_certificate_from_csr requires parsed_args.domains to be set
        for domain in domains:
            add_domains(parsed_args, domain)

        if not domains:
            # TODO: add CN to domains instead:
            raise errors.Error(
                "Unfortunately, your CSR %s needs to have a SubjectAltName for every domain"
                % parsed_args.csr[0])

        parsed_args.actual_csr = (csr, typ)

        csr_domains = set([d.lower() for d in domains])
        config_domains = set(parsed_args.domains)
        if csr_domains != config_domains:
            raise errors.ConfigurationError(
                "Inconsistent domain requests:\nFrom the CSR: {0}\nFrom command line/config: {1}"
                .format(", ".join(csr_domains), ", ".join(config_domains)))


    def determine_verb(self):
        """Determines the verb/subcommand provided by the user.

        This function works around some of the limitations of argparse.

        """
        if "-h" in self.args or "--help" in self.args:
            # all verbs double as help arguments; don't get them confused
            self.verb = "help"
            return

        for i, token in enumerate(self.args):
            if token in self.VERBS:
                verb = token
                if verb == "auth":
                    verb = "certonly"
                if verb == "everything":
                    verb = "run"
                self.verb = verb
                self.args.pop(i)
                return

        self.verb = "run"

    def prescan_for_flag(self, flag, possible_arguments):
        """Checks cli input for flags.

        Check for a flag, which accepts a fixed set of possible arguments, in
        the command line; we will use this information to configure argparse's
        help correctly.  Return the flag's argument, if it has one that matches
        the sequence @possible_arguments; otherwise return whether the flag is
        present.

        """
        if flag not in self.args:
            return False
        pos = self.args.index(flag)
        try:
            nxt = self.args[pos + 1]
            if nxt in possible_arguments:
                return nxt
        except IndexError:
            pass
        return True

    def add(self, topics, *args, **kwargs):
        """Add a new command line argument.

        :param topics: str or [str] help topic(s) this should be listed under,
                       or None for "always documented". The first entry
                       determines where the flag lives in the "--help all"
                       output (None -> "optional arguments").
        :param list *args: the names of this argument flag
        :param dict **kwargs: various argparse settings for this argument

        """

        if isinstance(topics, list):
            # if this flag can be listed in multiple sections, try to pick the one
            # that the user has asked for help about
            topic = self.help_arg if self.help_arg in topics else topics[0]
        else:
            topic = topics  # there's only one

        if self.detect_defaults:
            kwargs = self.modify_kwargs_for_default_detection(**kwargs)

        if self.visible_topics[topic]:
            if topic in self.groups:
                group = self.groups[topic]
                group.add_argument(*args, **kwargs)
            else:
                self.parser.add_argument(*args, **kwargs)
        else:
            kwargs["help"] = argparse.SUPPRESS
            self.parser.add_argument(*args, **kwargs)

    def modify_kwargs_for_default_detection(self, **kwargs):
        """Modify an arg so we can check if it was set by the user.

        Changes the parameters given to argparse when adding an argument
        so we can properly detect if the value was set by the user.

        :param dict kwargs: various argparse settings for this argument

        :returns: a modified versions of kwargs
        :rtype: dict

        """
        action = kwargs.get("action", None)
        if action not in EXIT_ACTIONS:
            kwargs["action"] = ("store_true" if action in ZERO_ARG_ACTIONS else
                                "store")
            kwargs["default"] = _Default()
            for param in ARGPARSE_PARAMS_TO_REMOVE:
                kwargs.pop(param, None)

        return kwargs

    def add_deprecated_argument(self, argument_name, num_args):
        """Adds a deprecated argument with the name argument_name.

        Deprecated arguments are not shown in the help. If they are used
        on the command line, a warning is shown stating that the
        argument is deprecated and no other action is taken.

        :param str argument_name: Name of deprecated argument.
        :param int nargs: Number of arguments the option takes.

        """
        util.add_deprecated_argument(
            self.parser.add_argument, argument_name, num_args)

    def add_group(self, topic, verbs=(), **kwargs):
        """Create a new argument group.

        This method must be called once for every topic, however, calls
        to this function are left next to the argument definitions for
        clarity.

        :param str topic: Name of the new argument group.
        :param str verbs: List of subcommands that should be documented as part of
                          this help group / topic

        :returns: The new argument group.
        :rtype: `HelpfulArgumentGroup`

        """
        if self.visible_topics[topic]:
            self.groups[topic] = self.parser.add_argument_group(topic, **kwargs)
            if self.help_arg:
                for v in verbs:
                    self.groups[topic].add_argument(v, help=VERB_HELP_MAP[v]["short"])

        return HelpfulArgumentGroup(self, topic)

    def add_plugin_args(self, plugins):
        """

        Let each of the plugins add its own command line arguments, which
        may or may not be displayed as help topics.

        """
        for name, plugin_ep in six.iteritems(plugins):
            parser_or_group = self.add_group(name,
                                             description=plugin_ep.long_description)
            plugin_ep.plugin_cls.inject_parser_options(parser_or_group, name)

    def determine_help_topics(self, chosen_topic):
        """

        The user may have requested help on a topic, return a dict of which
        topics to display. @chosen_topic has prescan_for_flag's return type

        :returns: dict

        """
        # topics maps each topic to whether it should be documented by
        # argparse on the command line
        if chosen_topic == "auth":
            chosen_topic = "certonly"
        if chosen_topic == "everything":
            chosen_topic = "run"
        if chosen_topic == "all":
            return dict([(t, True) for t in self.help_topics])
        elif not chosen_topic:
            return dict([(t, False) for t in self.help_topics])
        else:
            return dict([(t, t == chosen_topic) for t in self.help_topics])

def _add_all_groups(helpful):
    helpful.add_group("automation", description="Flags for automating execution & other tweaks")
    helpful.add_group("security", description="Security parameters & server settings")
    helpful.add_group("testing",
        description="The following flags are meant for testing and integration purposes only.")
    helpful.add_group("paths", description="Flags for changing execution paths & servers")
    helpful.add_group("manage",
        description="Various subcommands and flags are available for managing your certificates:",
        verbs=["certificates", "delete", "renew", "revoke", "update_symlinks"])

    # VERBS
    for verb, docs in VERB_HELP:
        name = docs.get("realname", verb)
        helpful.add_group(name, description=docs["opts"])


def prepare_and_parse_args(plugins, args, detect_defaults=False):  # pylint: disable=too-many-statements
    """Returns parsed command line arguments.

    :param .PluginsRegistry plugins: available plugins
    :param list args: command line arguments with the program name removed

    :returns: parsed command line arguments
    :rtype: argparse.Namespace

    """

    # pylint: disable=too-many-statements

    helpful = HelpfulArgumentParser(args, plugins, detect_defaults)
    _add_all_groups(helpful)

    # --help is automatically provided by argparse
    helpful.add(
        None, "-v", "--verbose", dest="verbose_count", action="count",
        default=flag_default("verbose_count"), help="This flag can be used "
        "multiple times to incrementally increase the verbosity of output, "
        "e.g. -vvv.")
    helpful.add(
        None, "-t", "--text", dest="text_mode", action="store_true",
        default=flag_default("text_mode"), help=argparse.SUPPRESS)
    helpful.add(
        None, "--max-log-backups", type=nonnegative_int,
        default=flag_default("max_log_backups"),
        help="Specifies the maximum number of backup logs that should "
             "be kept by Certbot's built in log rotation. Setting this "
             "flag to 0 disables log rotation entirely, causing "
             "Certbot to always append to the same log file.")
    helpful.add(
        [None, "automation", "run", "certonly", "enhance"],
        "-n", "--non-interactive", "--noninteractive",
        dest="noninteractive_mode", action="store_true",
        default=flag_default("noninteractive_mode"),
        help="Run without ever asking for user input. This may require "
              "additional command line flags; the client will try to explain "
              "which ones are required if it finds one missing")
    helpful.add(
        [None, "register", "run", "certonly", "enhance"],
        constants.FORCE_INTERACTIVE_FLAG, action="store_true",
        default=flag_default("force_interactive"),
        help="Force Certbot to be interactive even if it detects it's not "
             "being run in a terminal. This flag cannot be used with the "
             "renew subcommand.")
    helpful.add(
        [None, "run", "certonly", "certificates", "enhance"],
        "-d", "--domains", "--domain", dest="domains",
        metavar="DOMAIN", action=_DomainsAction,
        default=flag_default("domains"),
        help="Domain names to apply. For multiple domains you can use "
             "multiple -d flags or enter a comma separated list of domains "
             "as a parameter. The first domain provided will be the "
             "subject CN of the certificate, and all domains will be "
             "Subject Alternative Names on the certificate. "
             "The first domain will also be used in "
             "some software user interfaces and as the file paths for the "
             "certificate and related material unless otherwise "
             "specified or you already have a certificate with the same "
             "name. In the case of a name collision it will append a number "
             "like 0001 to the file path name. (default: Ask)")
    helpful.add(
        [None, "run", "certonly", "manage", "delete", "certificates",
         "renew", "enhance"], "--cert-name", dest="certname",
        metavar="CERTNAME", default=flag_default("certname"),
        help="Certificate name to apply. This name is used by Certbot for housekeeping "
             "and in file paths; it doesn't affect the content of the certificate itself. "
             "To see certificate names, run 'certbot certificates'. "
             "When creating a new certificate, specifies the new certificate's name. "
             "(default: the first provided domain or the name of an existing "
             "certificate on your system for the same domains)")
    helpful.add(
        [None, "testing", "renew", "certonly"],
        "--dry-run", action="store_true", dest="dry_run",
        default=flag_default("dry_run"),
        help="Perform a test run of the client, obtaining test (invalid) certificates"
             " but not saving them to disk. This can currently only be used"
             " with the 'certonly' and 'renew' subcommands. \nNote: Although --dry-run"
             " tries to avoid making any persistent changes on a system, it "
             " is not completely side-effect free: if used with webserver authenticator plugins"
             " like apache and nginx, it makes and then reverts temporary config changes"
             " in order to obtain test certificates, and reloads webservers to deploy and then"
             " roll back those changes.  It also calls --pre-hook and --post-hook commands"
             " if they are defined because they may be necessary to accurately simulate"
             " renewal. --deploy-hook commands are not called.")
    helpful.add(
        ["register", "automation"], "--register-unsafely-without-email", action="store_true",
        default=flag_default("register_unsafely_without_email"),
        help="Specifying this flag enables registering an account with no "
             "email address. This is strongly discouraged, because in the "
             "event of key loss or account compromise you will irrevocably "
             "lose access to your account. You will also be unable to receive "
             "notice about impending expiration or revocation of your "
             "certificates. Updates to the Subscriber Agreement will still "
             "affect you, and will be effective 14 days after posting an "
             "update to the web site.")
    helpful.add(
        "register", "--update-registration", action="store_true",
        default=flag_default("update_registration"),
        help="With the register verb, indicates that details associated "
             "with an existing registration, such as the e-mail address, "
             "should be updated, rather than registering a new account.")
    helpful.add(
        ["register", "unregister", "automation"], "-m", "--email",
        default=flag_default("email"),
        help=config_help("email"))
    helpful.add(["register", "automation"], "--eff-email", action="store_true",
                default=flag_default("eff_email"), dest="eff_email",
                help="Share your e-mail address with EFF")
    helpful.add(["register", "automation"], "--no-eff-email", action="store_false",
                default=flag_default("eff_email"), dest="eff_email",
                help="Don't share your e-mail address with EFF")
    helpful.add(
        ["automation", "certonly", "run"],
        "--keep-until-expiring", "--keep", "--reinstall",
        dest="reinstall", action="store_true", default=flag_default("reinstall"),
        help="If the requested certificate matches an existing certificate, always keep the "
             "existing one until it is due for renewal (for the "
             "'run' subcommand this means reinstall the existing certificate). (default: Ask)")
    helpful.add(
        "automation", "--expand", action="store_true", default=flag_default("expand"),
        help="If an existing certificate is a strict subset of the requested names, "
             "always expand and replace it with the additional names. (default: Ask)")
    helpful.add(
        "automation", "--version", action="version",
        version="%(prog)s {0}".format(certbot.__version__),
        help="show program's version number and exit")
    helpful.add(
        ["automation", "renew"],
        "--force-renewal", "--renew-by-default", dest="renew_by_default",
        action="store_true", default=flag_default("renew_by_default"),
        help="If a certificate "
             "already exists for the requested domains, renew it now, "
             "regardless of whether it is near expiry. (Often "
             "--keep-until-expiring is more appropriate). Also implies "
             "--expand.")
    helpful.add(
        "automation", "--renew-with-new-domains", dest="renew_with_new_domains",
        action="store_true", default=flag_default("renew_with_new_domains"),
        help="If a "
             "certificate already exists for the requested certificate name "
             "but does not match the requested domains, renew it now, "
             "regardless of whether it is near expiry.")
    helpful.add(
        ["automation", "renew", "certonly"],
        "--allow-subset-of-names", action="store_true",
        default=flag_default("allow_subset_of_names"),
        help="When performing domain validation, do not consider it a failure "
             "if authorizations can not be obtained for a strict subset of "
             "the requested domains. This may be useful for allowing renewals for "
             "multiple domains to succeed even if some domains no longer point "
             "at this system. This option cannot be used with --csr.")
    helpful.add(
        "automation", "--agree-tos", dest="tos", action="store_true",
        default=flag_default("tos"),
        help="Agree to the ACME Subscriber Agreement (default: Ask)")
    helpful.add(
        ["unregister", "automation"], "--account", metavar="ACCOUNT_ID",
        default=flag_default("account"),
        help="Account ID to use")
    helpful.add(
        "automation", "--duplicate", dest="duplicate", action="store_true",
        default=flag_default("duplicate"),
        help="Allow making a certificate lineage that duplicates an existing one "
             "(both can be renewed in parallel)")
    helpful.add(
        "automation", "--os-packages-only", action="store_true",
        default=flag_default("os_packages_only"),
        help="(certbot-auto only) install OS package dependencies and then stop")
    helpful.add(
        "automation", "--no-self-upgrade", action="store_true",
        default=flag_default("no_self_upgrade"),
        help="(certbot-auto only) prevent the certbot-auto script from"
             " upgrading itself to newer released versions (default: Upgrade"
             " automatically)")
    helpful.add(
        "automation", "--no-bootstrap", action="store_true",
        default=flag_default("no_bootstrap"),
        help="(certbot-auto only) prevent the certbot-auto script from"
             " installing OS-level dependencies (default: Prompt to install "
             " OS-wide dependencies, but exit if the user says 'No')")
    helpful.add(
        ["automation", "renew", "certonly", "run"],
        "-q", "--quiet", dest="quiet", action="store_true",
        default=flag_default("quiet"),
        help="Silence all output except errors. Useful for automation via cron."
             " Implies --non-interactive.")
    # overwrites server, handled in HelpfulArgumentParser.parse_args()
    helpful.add(["testing", "revoke", "run"], "--test-cert", "--staging",
        dest="staging", action="store_true", default=flag_default("staging"),
        help="Use the staging server to obtain or revoke test (invalid) certificates; equivalent"
             " to --server " + constants.STAGING_URI)
    helpful.add(
        "testing", "--debug", action="store_true", default=flag_default("debug"),
        help="Show tracebacks in case of errors, and allow certbot-auto "
             "execution on experimental platforms")
    helpful.add(
        [None, "certonly", "renew", "run"], "--debug-challenges", action="store_true",
        default=flag_default("debug_challenges"),
        help="After setting up challenges, wait for user input before "
             "submitting to CA")
    helpful.add(
        "testing", "--no-verify-ssl", action="store_true",
        help=config_help("no_verify_ssl"),
        default=flag_default("no_verify_ssl"))
    helpful.add(
        ["testing", "standalone", "apache", "nginx"], "--tls-sni-01-port", type=int,
        default=flag_default("tls_sni_01_port"),
        help=config_help("tls_sni_01_port"))
    helpful.add(
        ["testing", "standalone"], "--tls-sni-01-address",
        default=flag_default("tls_sni_01_address"),
        help=config_help("tls_sni_01_address"))
    helpful.add(
        ["testing", "standalone", "manual"], "--http-01-port", type=int,
        dest="http01_port",
        default=flag_default("http01_port"), help=config_help("http01_port"))
    helpful.add(
        ["testing", "standalone"], "--http-01-address",
        dest="http01_address",
        default=flag_default("http01_address"), help=config_help("http01_address"))
    helpful.add(
        "testing", "--break-my-certs", action="store_true",
        default=flag_default("break_my_certs"),
        help="Be willing to replace or renew valid certificates with invalid "
             "(testing/staging) certificates")
    helpful.add(
        "security", "--rsa-key-size", type=int, metavar="N",
        default=flag_default("rsa_key_size"), help=config_help("rsa_key_size"))
    helpful.add(
        "security", "--must-staple", action="store_true",
        dest="must_staple", default=flag_default("must_staple"),
        help=config_help("must_staple"))
    helpful.add(
        ["security", "enhance"],
        "--redirect", action="store_true", dest="redirect",
        default=flag_default("redirect"),
        help="Automatically redirect all HTTP traffic to HTTPS for the newly "
             "authenticated vhost. (default: Ask)")
    helpful.add(
        "security", "--no-redirect", action="store_false", dest="redirect",
        default=flag_default("redirect"),
        help="Do not automatically redirect all HTTP traffic to HTTPS for the newly "
             "authenticated vhost. (default: Ask)")
    helpful.add(
        ["security", "enhance"],
        "--hsts", action="store_true", dest="hsts", default=flag_default("hsts"),
        help="Add the Strict-Transport-Security header to every HTTP response."
             " Forcing browser to always use SSL for the domain."
             " Defends against SSL Stripping.")
    helpful.add(
        "security", "--no-hsts", action="store_false", dest="hsts",
        default=flag_default("hsts"), help=argparse.SUPPRESS)
    helpful.add(
        ["security", "enhance"],
        "--uir", action="store_true", dest="uir", default=flag_default("uir"),
        help='Add the "Content-Security-Policy: upgrade-insecure-requests"'
             ' header to every HTTP response. Forcing the browser to use'
             ' https:// for every http:// resource.')
    helpful.add(
        "security", "--no-uir", action="store_false", dest="uir", default=flag_default("uir"),
        help=argparse.SUPPRESS)
    helpful.add(
        "security", "--staple-ocsp", action="store_true", dest="staple",
        default=flag_default("staple"),
        help="Enables OCSP Stapling. A valid OCSP response is stapled to"
        " the certificate that the server offers during TLS.")
    helpful.add(
        "security", "--no-staple-ocsp", action="store_false", dest="staple",
        default=flag_default("staple"), help=argparse.SUPPRESS)
    helpful.add(
        "security", "--strict-permissions", action="store_true",
        default=flag_default("strict_permissions"),
        help="Require that all configuration files are owned by the current "
             "user; only needed if your config is somewhere unsafe like /tmp/")
    helpful.add(
        ["manual", "standalone", "certonly", "renew"],
        "--preferred-challenges", dest="pref_challs",
        action=_PrefChallAction, default=flag_default("pref_challs"),
        help='A sorted, comma delimited list of the preferred challenge to '
             'use during authorization with the most preferred challenge '
             'listed first (Eg, "dns" or "tls-sni-01,http,dns"). '
             'Not all plugins support all challenges. See '
             'https://certbot.eff.org/docs/using.html#plugins for details. '
             'ACME Challenges are versioned, but if you pick "http" rather '
             'than "http-01", Certbot will select the latest version '
             'automatically.')
    helpful.add(
        "renew", "--pre-hook",
        help="Command to be run in a shell before obtaining any certificates."
        " Intended primarily for renewal, where it can be used to temporarily"
        " shut down a webserver that might conflict with the standalone"
        " plugin. This will only be called if a certificate is actually to be"
        " obtained/renewed. When renewing several certificates that have"
        " identical pre-hooks, only the first will be executed.")
    helpful.add(
        "renew", "--post-hook",
        help="Command to be run in a shell after attempting to obtain/renew"
        " certificates. Can be used to deploy renewed certificates, or to"
        " restart any servers that were stopped by --pre-hook. This is only"
        " run if an attempt was made to obtain/renew a certificate. If"
        " multiple renewed certificates have identical post-hooks, only"
        " one will be run.")
    helpful.add("renew", "--renew-hook",
                action=_RenewHookAction, help=argparse.SUPPRESS)
    helpful.add(
        "renew", "--deploy-hook", action=_DeployHookAction,
        help='Command to be run in a shell once for each successfully'
        ' issued certificate. For this command, the shell variable'
        ' $RENEWED_LINEAGE will point to the config live subdirectory'
        ' (for example, "/etc/letsencrypt/live/example.com") containing'
        ' the new certificates and keys; the shell variable'
        ' $RENEWED_DOMAINS will contain a space-delimited list of'
        ' renewed certificate domains (for example, "example.com'
        ' www.example.com"')
    helpful.add(
        "renew", "--disable-hook-validation",
        action="store_false", dest="validate_hooks",
        default=flag_default("validate_hooks"),
        help="Ordinarily the commands specified for"
        " --pre-hook/--post-hook/--deploy-hook will be checked for"
        " validity, to see if the programs being run are in the $PATH,"
        " so that mistakes can be caught early, even when the hooks"
        " aren't being run just yet. The validation is rather"
        " simplistic and fails if you use more advanced shell"
        " constructs, so you can use this switch to disable it."
        " (default: False)")
    helpful.add(
        "renew", "--no-directory-hooks", action="store_false",
        default=flag_default("directory_hooks"), dest="directory_hooks",
        help="Disable running executables found in Certbot's hook directories"
        " during renewal. (default: False)")

    helpful.add_deprecated_argument("--agree-dev-preview", 0)
    helpful.add_deprecated_argument("--dialog", 0)

    _create_subparsers(helpful)
    _paths_parser(helpful)
    # _plugins_parsing should be the last thing to act upon the main
    # parser (--help should display plugin-specific options last)
    _plugins_parsing(helpful, plugins)

    if not detect_defaults:
        global helpful_parser # pylint: disable=global-statement
        helpful_parser = helpful
    return helpful.parse_args()


def _create_subparsers(helpful):
    helpful.add("config_changes", "--num", type=int, default=flag_default("num"),
                help="How many past revisions you want to be displayed")

    from certbot.client import sample_user_agent # avoid import loops
    helpful.add(
        None, "--user-agent", default=flag_default("user_agent"),
        help='Set a custom user agent string for the client. User agent strings allow '
             'the CA to collect high level statistics about success rates by OS, '
             'plugin and use case, and to know when to deprecate support for past Python '
             "versions and flags. If you wish to hide this information from the Let's "
             'Encrypt server, set this to "". '
             '(default: {0}). The flags encoded in the user agent are: '
             '--duplicate, --force-renew, --allow-subset-of-names, -n, and '
             'whether any hooks are set.'.format(sample_user_agent()))
    helpful.add(
        None, "--user-agent-comment", default=flag_default("user_agent_comment"),
        type=_user_agent_comment_type,
        help="Add a comment to the default user agent string. May be used when repackaging Certbot "
             "or calling it from another tool to allow additional statistical data to be collected."
             " Ignored if --user-agent is set. (Example: Foo-Wrapper/1.0)")
    helpful.add("certonly",
                "--csr", default=flag_default("csr"), type=read_file,
                help="Path to a Certificate Signing Request (CSR) in DER or PEM format."
                " Currently --csr only works with the 'certonly' subcommand.")
    helpful.add("revoke",
                "--reason", dest="reason",
                choices=CaseInsensitiveList(sorted(constants.REVOCATION_REASONS,
                                                   key=constants.REVOCATION_REASONS.get)),
                action=_EncodeReasonAction, default=flag_default("reason"),
                help="Specify reason for revoking certificate. (default: unspecified)")
    helpful.add("revoke",
                "--delete-after-revoke", action="store_true",
                default=flag_default("delete_after_revoke"),
                help="Delete certificates after revoking them.")
    helpful.add("revoke",
                "--no-delete-after-revoke", action="store_false",
                dest="delete_after_revoke",
                default=flag_default("delete_after_revoke"),
                help="Do not delete certificates after revoking them. This "
                     "option should be used with caution because the 'renew' "
                     "subcommand will attempt to renew undeleted revoked "
                     "certificates.")
    helpful.add("rollback",
                "--checkpoints", type=int, metavar="N",
                default=flag_default("rollback_checkpoints"),
                help="Revert configuration N number of checkpoints.")
    helpful.add("plugins",
                "--init", action="store_true", default=flag_default("init"),
                help="Initialize plugins.")
    helpful.add("plugins",
                "--prepare", action="store_true", default=flag_default("prepare"),
                help="Initialize and prepare plugins.")
    helpful.add("plugins",
                "--authenticators", action="append_const", dest="ifaces",
                default=flag_default("ifaces"),
                const=interfaces.IAuthenticator, help="Limit to authenticator plugins only.")
    helpful.add("plugins",
                "--installers", action="append_const", dest="ifaces",
                default=flag_default("ifaces"),
                const=interfaces.IInstaller, help="Limit to installer plugins only.")


class CaseInsensitiveList(list):
    """A list that will ignore case when searching.

    This class is passed to the `choices` argument of `argparse.add_arguments`
    through the `helpful` wrapper. It is necessary due to special handling of
    command line arguments by `set_by_cli` in which the `type_func` is not applied."""
    def __contains__(self, element):
        return super(CaseInsensitiveList, self).__contains__(element.lower())


def _paths_parser(helpful):
    add = helpful.add
    verb = helpful.verb
    if verb == "help":
        verb = helpful.help_arg

    cph = "Path to where certificate is saved (with auth --csr), installed from, or revoked."
    section = ["paths", "install", "revoke", "certonly", "manage"]
    if verb == "certonly":
        add(section, "--cert-path", type=os.path.abspath,
            default=flag_default("auth_cert_path"), help=cph)
    elif verb == "revoke":
        add(section, "--cert-path", type=read_file, required=True, help=cph)
    else:
        add(section, "--cert-path", type=os.path.abspath, help=cph)

    section = "paths"
    if verb in ("install", "revoke"):
        section = verb
    # revoke --key-path reads a file, install --key-path takes a string
    add(section, "--key-path",
        type=((verb == "revoke" and read_file) or os.path.abspath),
        help="Path to private key for certificate installation "
             "or revocation (if account key is missing)")

    default_cp = None
    if verb == "certonly":
        default_cp = flag_default("auth_chain_path")
    add(["paths", "install"], "--fullchain-path", default=default_cp, type=os.path.abspath,
        help="Accompanying path to a full certificate chain (certificate plus chain).")
    add("paths", "--chain-path", default=default_cp, type=os.path.abspath,
        help="Accompanying path to a certificate chain.")
    add("paths", "--config-dir", default=flag_default("config_dir"),
        help=config_help("config_dir"))
    add("paths", "--work-dir", default=flag_default("work_dir"),
        help=config_help("work_dir"))
    add("paths", "--logs-dir", default=flag_default("logs_dir"),
        help="Logs directory.")
    add("paths", "--server", default=flag_default("server"),
        help=config_help("server"))


def _plugins_parsing(helpful, plugins):
    # It's nuts, but there are two "plugins" topics.  Somehow this works
    helpful.add_group(
        "plugins", description="Plugin Selection: Certbot client supports an "
        "extensible plugins architecture. See '%(prog)s plugins' for a "
        "list of all installed plugins and their names. You can force "
        "a particular plugin by setting options provided below. Running "
        "--help <plugin_name> will list flags specific to that plugin.")

    helpful.add("plugins", "--configurator", default=flag_default("configurator"),
                help="Name of the plugin that is both an authenticator and an installer."
                " Should not be used together with --authenticator or --installer. "
                "(default: Ask)")
    helpful.add("plugins", "-a", "--authenticator", default=flag_default("authenticator"),
                help="Authenticator plugin name.")
    helpful.add("plugins", "-i", "--installer", default=flag_default("installer"),
                help="Installer plugin name (also used to find domains).")
    helpful.add(["plugins", "certonly", "run", "install", "config_changes"],
                "--apache", action="store_true", default=flag_default("apache"),
                help="Obtain and install certificates using Apache")
    helpful.add(["plugins", "certonly", "run", "install", "config_changes"],
                "--nginx", action="store_true", default=flag_default("nginx"),
                help="Obtain and install certificates using Nginx")
    helpful.add(["plugins", "certonly"], "--standalone", action="store_true",
                default=flag_default("standalone"),
                help='Obtain certificates using a "standalone" webserver.')
    helpful.add(["plugins", "certonly"], "--manual", action="store_true",
                default=flag_default("manual"),
                help="Provide laborious manual instructions for obtaining a certificate")
    helpful.add(["plugins", "certonly"], "--webroot", action="store_true",
                default=flag_default("webroot"),
                help="Obtain certificates by placing files in a webroot directory.")
    helpful.add(["plugins", "certonly"], "--dns-cloudflare", action="store_true",
                default=flag_default("dns_cloudflare"),
                help=("Obtain certificates using a DNS TXT record (if you are "
                      "using Cloudflare for DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-cloudxns", action="store_true",
                default=flag_default("dns_cloudxns"),
                help=("Obtain certificates using a DNS TXT record (if you are "
                     "using CloudXNS for DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-digitalocean", action="store_true",
                default=flag_default("dns_digitalocean"),
                help=("Obtain certificates using a DNS TXT record (if you are "
                      "using DigitalOcean for DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-dnsimple", action="store_true",
                default=flag_default("dns_dnsimple"),
                help=("Obtain certificates using a DNS TXT record (if you are "
                      "using DNSimple for DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-dnsmadeeasy", action="store_true",
                default=flag_default("dns_dnsmadeeasy"),
                help=("Obtain certificates using a DNS TXT record (if you are"
                      "using DNS Made Easy for DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-google", action="store_true",
                default=flag_default("dns_google"),
                help=("Obtain certificates using a DNS TXT record (if you are "
                      "using Google Cloud DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-luadns", action="store_true",
                default=flag_default("dns_luadns"),
                help=("Obtain certificates using a DNS TXT record (if you are "
                      "using LuaDNS for DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-nsone", action="store_true",
                default=flag_default("dns_nsone"),
                help=("Obtain certificates using a DNS TXT record (if you are "
                      "using NS1 for DNS)."))
    helpful.add(["plugins", "certonly"], "--dns-rfc2136", action="store_true",
                default=flag_default("dns_rfc2136"),
                help="Obtain certificates using a DNS TXT record (if you are using BIND for DNS).")
    helpful.add(["plugins", "certonly"], "--dns-route53", action="store_true",
                default=flag_default("dns_route53"),
                help=("Obtain certificates using a DNS TXT record (if you are using Route53 for "
                      "DNS)."))

    # things should not be reorder past/pre this comment:
    # plugins_group should be displayed in --help before plugin
    # specific groups (so that plugins_group.description makes sense)

    helpful.add_plugin_args(plugins)


class _EncodeReasonAction(argparse.Action):
    """Action class for parsing revocation reason."""

    def __call__(self, parser, namespace, reason, option_string=None):
        """Encodes the reason for certificate revocation."""
        code = constants.REVOCATION_REASONS[reason.lower()]
        setattr(namespace, self.dest, code)


class _DomainsAction(argparse.Action):
    """Action class for parsing domains."""

    def __call__(self, parser, namespace, domain, option_string=None):
        """Just wrap add_domains in argparseese."""
        add_domains(namespace, domain)

def add_domains(args_or_config, domains):
    """Registers new domains to be used during the current client run.

    Domains are not added to the list of requested domains if they have
    already been registered.

    :param args_or_config: parsed command line arguments
    :type args_or_config: argparse.Namespace or
        configuration.NamespaceConfig
    :param str domain: one or more comma separated domains

    :returns: domains after they have been normalized and validated
    :rtype: `list` of `str`

    """
    validated_domains = []
    for domain in domains.split(","):
        domain = util.enforce_domain_sanity(domain.strip())
        validated_domains.append(domain)
        if domain not in args_or_config.domains:
            args_or_config.domains.append(domain)

    return validated_domains

class _PrefChallAction(argparse.Action):
    """Action class for parsing preferred challenges."""

    def __call__(self, parser, namespace, pref_challs, option_string=None):
        try:
            challs = parse_preferred_challenges(pref_challs.split(","))
        except errors.Error as error:
            raise argparse.ArgumentError(self, str(error))
        namespace.pref_challs.extend(challs)


def parse_preferred_challenges(pref_challs):
    """Translate and validate preferred challenges.

    :param pref_challs: list of preferred challenge types
    :type pref_challs: `list` of `str`

    :returns: validated list of preferred challenge types
    :rtype: `list` of `str`

    :raises errors.Error: if pref_challs is invalid

    """
    aliases = {"dns": "dns-01", "http": "http-01", "tls-sni": "tls-sni-01"}
    challs = [c.strip() for c in pref_challs]
    challs = [aliases.get(c, c) for c in challs]
    unrecognized = ", ".join(name for name in challs
                             if name not in challenges.Challenge.TYPES)
    if unrecognized:
        raise errors.Error(
            "Unrecognized challenges: {0}".format(unrecognized))
    return challs

def _user_agent_comment_type(value):
    if "(" in value or ")" in value:
        raise argparse.ArgumentTypeError("may not contain parentheses")
    return value

class _DeployHookAction(argparse.Action):
    """Action class for parsing deploy hooks."""

    def __call__(self, parser, namespace, values, option_string=None):
        renew_hook_set = namespace.deploy_hook != namespace.renew_hook
        if renew_hook_set and namespace.renew_hook != values:
            raise argparse.ArgumentError(
                self, "conflicts with --renew-hook value")
        namespace.deploy_hook = namespace.renew_hook = values


class _RenewHookAction(argparse.Action):
    """Action class for parsing renew hooks."""

    def __call__(self, parser, namespace, values, option_string=None):
        deploy_hook_set = namespace.deploy_hook is not None
        if deploy_hook_set and namespace.deploy_hook != values:
            raise argparse.ArgumentError(
                self, "conflicts with --deploy-hook value")
        namespace.renew_hook = values


def nonnegative_int(value):
    """Converts value to an int and checks that it is not negative.

    This function should used as the type parameter for argparse
    arguments.

    :param str value: value provided on the command line

    :returns: integer representation of value
    :rtype: int

    :raises argparse.ArgumentTypeError: if value isn't a non-negative integer

    """
    try:
        int_value = int(value)
    except ValueError:
        raise argparse.ArgumentTypeError("value must be an integer")

    if int_value < 0:
        raise argparse.ArgumentTypeError("value must be non-negative")
    return int_value
