# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2011 OpenStack, LLC
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""Base class for all storage backends"""

import logging

from glance.common import exception

logger = logging.getLogger('glance.store.base')


class Store(object):

    CHUNKSIZE = (16 * 1024 * 1024)  # 16M

    def __init__(self, options=None):
        """
        Initialize the Store

        :param options: Optional dictionary of configuration options
        """
        self.options = options or {}
        try:
            self.configure()
        except exception.BadStoreConfiguration:
            msg = _("Failed to configure store correctly. "
                    "Disabling add method.")
            logger.error(msg)
            self.add = self.add_disabled

    def configure(self):
        """
        Configure the Store to use the stored configuration options
        Any store that needs special configuration should implement
        this method. If the store was not able to successfully configure
        itself, it should raise `exception.BadStoreConfiguration`
        """
        pass

    def get(self, location):
        """
        Takes a `glance.store.location.Location` object that indicates
        where to find the image file, and returns a generator for reading
        the image file

        :param location `glance.store.location.Location` object, supplied
                        from glance.store.location.get_location_from_uri()
        :raises `glance.exception.NotFound` if image does not exist
        """
        raise NotImplementedError

    def add_disabled(self, *args, **kwargs):
        """
        Add method that raises an exception because the Store was
        not able to be configured properly and therefore the add()
        method would error out.
        """
        raise exception.StoreAddDisabled

    def add(self, image_id, image_file, image_size):
        """
        Stores an image file with supplied identifier to the backend
        storage system and returns an `glance.store.ImageAddResult` object
        containing information about the stored image.

        :param image_id: The opaque image identifier
        :param image_file: The image data to write, as a file-like object
        :param image_size: The size of the image data to write, in bytes

        :retval `glance.store.ImageAddResult` object
        :raises `glance.common.exception.Duplicate` if the image already
                existed
        """
        raise NotImplementedError

    def delete(self, location):
        """
        Takes a `glance.store.location.Location` object that indicates
        where to find the image file to delete

        :location `glance.store.location.Location` object, supplied
                  from glance.store.location.get_location_from_uri()
        :raises `glance.exception.NotFound` if image does not exist
        """
        raise NotImplementedError
