# Copyright 2012 OpenStack Foundation
#
# 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.

"""Token provider interface."""

import abc

import six

from keystone.common import cache
from keystone.common import dependency
from keystone.common import manager
from keystone import config

from keystone import exception
from keystone.openstack.common.gettextutils import _
from keystone.openstack.common import log
from keystone.openstack.common import timeutils


CONF = config.CONF
LOG = log.getLogger(__name__)
SHOULD_CACHE = cache.should_cache_fn('token')

# NOTE(blk-u): The config options are not available at import time.
EXPIRATION_TIME = lambda: CONF.token.cache_time

# supported token versions
V2 = 'v2.0'
V3 = 'v3.0'
VERSIONS = frozenset([V2, V3])

# default token providers
PKI_PROVIDER = 'keystone.token.providers.pki.Provider'
UUID_PROVIDER = 'keystone.token.providers.uuid.Provider'


class UnsupportedTokenVersionException(Exception):
    """Token version is unrecognizable or unsupported."""
    pass


@dependency.requires('token_api')
@dependency.optional('revoke_api')
@dependency.provider('token_provider_api')
class Manager(manager.Manager):
    """Default pivot point for the token provider backend.

    See :mod:`keystone.common.manager.Manager` for more details on how this
    dynamically calls the backend.

    """

    @classmethod
    def get_token_provider(cls):
        """Return package path to the configured token provider.

        The value should come from ``keystone.conf`` ``[token] provider``,
        however this method ensures backwards compatibility for
        ``keystone.conf`` ``[signing] token_format`` until Havana + 2.

        Return the provider based on ``token_format`` if ``provider`` is not
        set. Otherwise, ignore ``token_format`` and return the configured
        ``provider`` instead.

        """
        if CONF.token.provider is not None:
            # NOTE(gyee): we are deprecating CONF.signing.token_format. This
            # code is to ensure the token provider configuration agrees with
            # CONF.signing.token_format.
            if (CONF.signing.token_format and
                    ((CONF.token.provider == PKI_PROVIDER and
                        CONF.signing.token_format != 'PKI') or
                        (CONF.token.provider == UUID_PROVIDER and
                            CONF.signing.token_format != 'UUID'))):
                raise exception.UnexpectedError(
                    _('keystone.conf [signing] token_format (deprecated) '
                      'conflicts with keystone.conf [token] provider'))
            return CONF.token.provider
        else:
            if not CONF.signing.token_format:
                # No token provider and no format, so use default (PKI)
                return PKI_PROVIDER

            msg = _('keystone.conf [signing] token_format is deprecated in '
                    'favor of keystone.conf [token] provider')
            if CONF.signing.token_format == 'PKI':
                LOG.warning(msg)
                return PKI_PROVIDER
            elif CONF.signing.token_format == 'UUID':
                LOG.warning(msg)
                return UUID_PROVIDER
            else:
                raise exception.UnexpectedError(
                    _('Unrecognized keystone.conf [signing] token_format: '
                      'expected either \'UUID\' or \'PKI\''))

    def __init__(self):
        super(Manager, self).__init__(self.get_token_provider())

    def validate_token(self, token_id, belongs_to=None):
        unique_id = self.token_api.unique_id(token_id)
        # NOTE(morganfainberg): Ensure we never use the long-form token_id
        # (PKI) as part of the cache_key.
        token = self._validate_token(unique_id)
        self._token_belongs_to(token, belongs_to)
        self._is_valid_token(token)
        return token

    def check_revocation_v2(self, token):
        try:
            token_data = token['access']
        except KeyError:
            raise exception.TokenNotFound(_('Failed to validate token'))

        if self.revoke_api is not None:
            token_values = self.revoke_api.model.build_token_values_v2(
                token_data, CONF.identity.default_domain_id)
            self.revoke_api.check_token(token_values)

    def validate_v2_token(self, token_id, belongs_to=None):
        unique_id = self.token_api.unique_id(token_id)
        # NOTE(morganfainberg): Ensure we never use the long-form token_id
        # (PKI) as part of the cache_key.
        token = self._validate_v2_token(unique_id)
        self.check_revocation_v2(token)
        self._token_belongs_to(token, belongs_to)
        self._is_valid_token(token)
        return token

    def check_revocation_v3(self, token):
        try:
            token_data = token['token']
        except KeyError:
            raise exception.TokenNotFound(_('Failed to validate token'))
        if self.revoke_api is not None:
            token_values = self.revoke_api.model.build_token_values(token_data)
            self.revoke_api.check_token(token_values)

    def check_revocation(self, token):
        version = self.driver.get_token_version(token)
        if version == V2:
            return self.check_revocation_v2(token)
        else:
            return self.check_revocation_v3(token)

    def validate_v3_token(self, token_id):
        unique_id = self.token_api.unique_id(token_id)
        # NOTE(morganfainberg): Ensure we never use the long-form token_id
        # (PKI) as part of the cache_key.
        token = self._validate_v3_token(unique_id)
        self._is_valid_token(token)
        return token

    def check_v2_token(self, token_id, belongs_to=None):
        """Check the validity of the given V2 token.

        :param token_id: identity of the token
        :param belongs_to: optional identity of the scoped project
        :returns: None
        :raises: keystone.exception.Unauthorized
        """
        # NOTE(morganfainberg): Ensure we never use the long-form token_id
        # (PKI) as part of the cache_key.
        unique_id = self.token_api.unique_id(token_id)
        self.validate_v2_token(unique_id, belongs_to=belongs_to)

    def check_v3_token(self, token_id):
        """Check the validity of the given V3 token.

        :param token_id: identity of the token
        :returns: None
        :raises: keystone.exception.Unauthorized
        """
        # NOTE(morganfainberg): Ensure we never use the long-form token_id
        # (PKI) as part of the cache_key.
        unique_id = self.token_api.unique_id(token_id)
        self.validate_v3_token(unique_id)

    @cache.on_arguments(should_cache_fn=SHOULD_CACHE,
                        expiration_time=EXPIRATION_TIME)
    def _validate_token(self, token_id):
        return self.driver.validate_token(token_id)

    @cache.on_arguments(should_cache_fn=SHOULD_CACHE,
                        expiration_time=EXPIRATION_TIME)
    def _validate_v2_token(self, token_id):
        return self.driver.validate_v2_token(token_id)

    @cache.on_arguments(should_cache_fn=SHOULD_CACHE,
                        expiration_time=EXPIRATION_TIME)
    def _validate_v3_token(self, token_id):
        return self.driver.validate_v3_token(token_id)

    def _is_valid_token(self, token):
        """Verify the token is valid format and has not expired."""

        current_time = timeutils.normalize_time(timeutils.utcnow())

        try:
            # Get the data we need from the correct location (V2 and V3 tokens
            # differ in structure, Try V3 first, fall back to V2 second)
            token_data = token.get('token', token.get('access'))
            expires_at = token_data.get('expires_at',
                                        token_data.get('expires'))
            if not expires_at:
                expires_at = token_data['token']['expires']
            expiry = timeutils.normalize_time(
                timeutils.parse_isotime(expires_at))
        except Exception:
            LOG.exception(_('Unexpected error or malformed token determining '
                            'token expiry: %s'), token)
            raise exception.TokenNotFound(_('Failed to validate token'))

        if current_time < expiry:
            self.check_revocation(token)
            # Token has not expired and has not been revoked.
            return None
        else:
            raise exception.TokenNotFound(_('Failed to validate token'))

    def _token_belongs_to(self, token, belongs_to):
        """Check if the token belongs to the right tenant.

        This is only used on v2 tokens.  The structural validity of the token
        will have already been checked before this method is called.

        """
        if belongs_to:
            token_data = token['access']['token']
            if ('tenant' not in token_data or
                    token_data['tenant']['id'] != belongs_to):
                raise exception.Unauthorized()

    def invalidate_individual_token_cache(self, token_id):
        # NOTE(morganfainberg): invalidate takes the exact same arguments as
        # the normal method, this means we need to pass "self" in (which gets
        # stripped off).

        # FIXME(morganfainberg): Does this cache actually need to be
        # invalidated? We maintain a cached revocation list, which should be
        # consulted before accepting a token as valid.  For now we will
        # do the explicit individual token invalidation.

        self._validate_token.invalidate(self, token_id)
        self._validate_v2_token.invalidate(self, token_id)
        self._validate_v3_token.invalidate(self, token_id)


@six.add_metaclass(abc.ABCMeta)
class Provider(object):
    """Interface description for a Token provider."""

    @abc.abstractmethod
    def get_token_version(self, token_data):
        """Return the version of the given token data.

        If the given token data is unrecognizable,
        UnsupportedTokenVersionException is raised.

        :param token_data: token_data
        :type token_data: dict
        :returns: token version string
        :raises: keystone.token.provider.UnsupportedTokenVersionException
        """
        raise exception.NotImplemented()

    @abc.abstractmethod
    def issue_v2_token(self, token_ref, roles_ref=None, catalog_ref=None):
        """Issue a V2 token.

        :param token_ref: token data to generate token from
        :type token_ref: dict
        :param roles_ref: optional roles list
        :type roles_ref: dict
        :param catalog_ref: optional catalog information
        :type catalog_ref: dict
        :returns: (token_id, token_data)
        """
        raise exception.NotImplemented()

    @abc.abstractmethod
    def issue_v3_token(self, user_id, method_names, expires_at=None,
                       project_id=None, domain_id=None, auth_context=None,
                       metadata_ref=None, include_catalog=True):
        """Issue a V3 Token.

        :param user_id: identity of the user
        :type user_id: string
        :param method_names: names of authentication methods
        :type method_names: list
        :param expires_at: optional time the token will expire
        :type expires_at: string
        :param project_id: optional project identity
        :type project_id: string
        :param domain_id: optional domain identity
        :type domain_id: string
        :param auth_context: optional context from the authorization plugins
        :type auth_context: dict
        :param metadata_ref: optional metadata reference
        :type metadata_ref: dict
        :param include_catalog: optional, include the catalog in token data
        :type include_catalog: boolean
        :returns: (token_id, token_data)
        """
        raise exception.NotImplemented()

    @abc.abstractmethod
    def revoke_token(self, token_id):
        """Revoke a given token.

        :param token_id: identity of the token
        :type token_id: string
        :returns: None.
        """
        raise exception.NotImplemented()

    @abc.abstractmethod
    def validate_token(self, token_id):
        """Detect token version and validate token and return the token data.

        Must raise Unauthorized exception if unable to validate token.

        :param token_id: identity of the token
        :type token_id: string
        :returns: token_data
        :raises: keystone.exception.TokenNotFound
        """
        raise exception.NotImplemented()

    @abc.abstractmethod
    def validate_v2_token(self, token_id):
        """Validate the given V2 token and return the token data.

        Must raise Unauthorized exception if unable to validate token.

        :param token_id: identity of the token
        :type token_id: string
        :returns: token data
        :raises: keystone.exception.TokenNotFound

        """
        raise exception.NotImplemented()

    @abc.abstractmethod
    def validate_v3_token(self, token_id):
        """Validate the given V3 token and return the token_data.

        :param token_id: identity of the token
        :type token_id: string
        :returns: token data
        :raises: keystone.exception.TokenNotFound
        """
        raise exception.NotImplemented()

    @abc.abstractmethod
    def _get_token_id(self, token_data):
        """Generate the token_id based upon the data in token_data.

        :param token_data: token information
        :type token_data: dict
        returns: token identifier
        """
        raise exception.NotImplemented()
