# 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.

import itertools
import os

from positional import positional

try:
    from oslo_config import cfg
except ImportError:
    cfg = None


__all__ = ('Opt',)


class Opt(object):
    """An option required by an authentication plugin.

    Opts provide a means for authentication plugins that are going to be
    dynamically loaded to specify the parameters that are to be passed to the
    plugin on initialization.

    The Opt specifies information about the way the plugin parameter is to be
    represented in different loading mechanisms.

    When defining an Opt with a - the - should be present in the name
    parameter. This will automatically be converted to an _ when passing to the
    plugin initialization. For example, you should specify::

        Opt('user-domain-id')

    which will pass the value as `user_domain_id` to the plugin's
    initialization.

    :param str name: The name of the option.
    :param callable type: The type of the option. This is a callable which is
        passed the raw option that was loaded (often a string) and is required
        to return the parameter in the type expected by __init__.
    :param str help: The help text that is shown along with the option.
    :param bool secret: If the parameter is secret it should not be printed or
        logged in debug output.
    :param str dest: the name of the argument that will be passed to __init__.
        This allows you to have a different name in loading than is used by the
        __init__ function. Defaults to the the value of name.
    :param opt: A list of other options that are deprecated in favour of this
        one. This ensures the old options are still registered.
    :type opt: list(Opt)
    :param default: A default value that can be used if one is not provided.
    :param str metavar: The <metavar> that should be printed in CLI help text.
    :param bool required: If the option is required to load the plugin. If a
        required option is not present loading should fail.
    """

    @positional()
    def __init__(self,
                 name,
                 type=str,
                 help=None,
                 secret=False,
                 dest=None,
                 deprecated=None,
                 default=None,
                 metavar=None,
                 required=False):
        if not callable(type):
            raise TypeError('type must be callable')

        if dest is None:
            dest = name.replace('-', '_')

        self.name = name
        self.type = type
        self.help = help
        self.secret = secret
        self.required = required
        self.dest = dest
        self.deprecated = [] if deprecated is None else deprecated
        self.default = default
        self.metavar = metavar
        # These are for oslo.config compat
        self.deprecated_opts = self.deprecated
        self.deprecated_for_removal = []
        self.sample_default = None
        self.group = None

    def __repr__(self):
        return '<Opt: %s>' % self.name

    def _to_oslo_opt(self):
        if not cfg:
            raise ImportError("oslo.config is not an automatic dependency of "
                              "keystoneauth. If you wish to use oslo.config "
                              "you need to import it into your application's "
                              "requirements file. ")

        deprecated_opts = [cfg.DeprecatedOpt(o.name) for o in self.deprecated]

        return cfg.Opt(name=self.name,
                       type=self.type,
                       help=self.help,
                       secret=self.secret,
                       required=self.required,
                       dest=self.dest,
                       deprecated_opts=deprecated_opts,
                       metavar=self.metavar)

    def __eq__(self, other):
        return (type(self) == type(other) and
                self.name == other.name and
                self.type == other.type and
                self.help == other.help and
                self.secret == other.secret and
                self.required == other.required and
                self.dest == other.dest and
                self.deprecated == other.deprecated and
                self.default == other.default and
                self.metavar == other.metavar)

    @property
    def _all_opts(self):
        return itertools.chain([self], self.deprecated)

    @property
    def argparse_args(self):
        return ['--os-%s' % o.name for o in self._all_opts]

    @property
    def argparse_default(self):
        # select the first ENV that is not false-y or return None
        for o in self._all_opts:
            v = os.environ.get('OS_%s' % o.name.replace('-', '_').upper())
            if v:
                return v

        return self.default
