#
#    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.

from heat.common import exception
from heat.common.i18n import _
from heat.engine import attributes
from heat.engine import constraints
from heat.engine import properties
from heat.engine import resource
from heat.engine import support


class KeyPair(resource.Resource):
    """
    A resource for creating Nova key pairs.

    **Note** that if a new key is generated setting `save_private_key` to
    `True` results in the system saving the private key which can then be
    retrieved via the `private_key` attribute of this resource.

    Setting the `public_key` property means that the `private_key` attribute
    of this resource will always return an empty string regardless of the
    `save_private_key` setting since there will be no private key data to
    save.
    """

    support_status = support.SupportStatus(version='2014.1')

    PROPERTIES = (
        NAME, SAVE_PRIVATE_KEY, PUBLIC_KEY,
    ) = (
        'name', 'save_private_key', 'public_key',
    )

    ATTRIBUTES = (
        PUBLIC_KEY_ATTR, PRIVATE_KEY,
    ) = (
        'public_key', 'private_key',
    )

    properties_schema = {
        NAME: properties.Schema(
            properties.Schema.STRING,
            _('The name of the key pair.'),
            required=True,
            constraints=[
                constraints.Length(min=1, max=255)
            ]
        ),
        SAVE_PRIVATE_KEY: properties.Schema(
            properties.Schema.BOOLEAN,
            _('True if the system should remember a generated private key; '
              'False otherwise.'),
            default=False
        ),
        PUBLIC_KEY: properties.Schema(
            properties.Schema.STRING,
            _('The optional public key. This allows users to supply the '
              'public key from a pre-existing key pair. If not supplied, a '
              'new key pair will be generated.')
        ),
    }

    attributes_schema = {
        PUBLIC_KEY: attributes.Schema(
            _('The public key.')
        ),
        PRIVATE_KEY: attributes.Schema(
            _('The private key if it has been saved.'),
            cache_mode=attributes.Schema.CACHE_NONE
        ),
    }

    default_client_name = 'nova'

    def __init__(self, name, json_snippet, stack):
        super(KeyPair, self).__init__(name, json_snippet, stack)
        self._public_key = None

    @property
    def private_key(self):
        """Return the private SSH key for the resource."""
        if self.properties[self.SAVE_PRIVATE_KEY]:
            return self.data().get('private_key', '')
        else:
            return ''

    @property
    def public_key(self):
        """Return the public SSH key for the resource."""
        if not self._public_key:
            if self.properties[self.PUBLIC_KEY]:
                self._public_key = self.properties[self.PUBLIC_KEY]
            elif self.resource_id:
                nova_key = self.client_plugin().get_keypair(self.resource_id)
                self._public_key = nova_key.public_key
        return self._public_key

    def handle_create(self):
        pub_key = self.properties[self.PUBLIC_KEY] or None
        new_keypair = self.nova().keypairs.create(self.properties[self.NAME],
                                                  public_key=pub_key)
        if (self.properties[self.SAVE_PRIVATE_KEY] and
                hasattr(new_keypair, 'private_key')):
            self.data_set('private_key',
                          new_keypair.private_key,
                          True)
        self.resource_id_set(new_keypair.id)

    def handle_delete(self):
        if self.resource_id:
            try:
                self.nova().keypairs.delete(self.resource_id)
            except Exception as e:
                self.client_plugin().ignore_not_found(e)

    def _resolve_attribute(self, key):
        attr_fn = {'private_key': self.private_key,
                   'public_key': self.public_key}
        return unicode(attr_fn[key])

    def FnGetRefId(self):
        return self.resource_id


class KeypairConstraint(constraints.BaseCustomConstraint):

    expected_exceptions = (exception.UserKeyPairMissing,)

    def validate_with_client(self, client, value):
        if not value:
            # Don't validate empty key, which can happen when you use a KeyPair
            # resource
            return True
        client.client_plugin('nova').get_keypair(value)


def resource_mapping():
    return {'OS::Nova::KeyPair': KeyPair}
