# Copyright 2010 Jacob Kaplan-Moss

# Copyright (c) 2011 OpenStack Foundation
# 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 utilities to build API operation managers and objects on top of.
"""
import abc
import contextlib
import hashlib
import os

import six

from cinderclient import exceptions
from cinderclient.openstack.common.apiclient import base as common_base
from cinderclient import utils


Resource = common_base.Resource


def getid(obj):
    """
    Abstracts the common pattern of allowing both an object or an object's ID
    as a parameter when dealing with relationships.
    """
    try:
        return obj.id
    except AttributeError:
        return obj


class Manager(utils.HookableMixin):
    """
    Managers interact with a particular type of API (servers, flavors, images,
    etc.) and provide CRUD operations for them.
    """
    resource_class = None

    def __init__(self, api):
        self.api = api

    def _list(self, url, response_key, obj_class=None, body=None,
              limit=None, items=None):
        resp = None
        if items is None:
            items = []
        if body:
            resp, body = self.api.client.post(url, body=body)
        else:
            resp, body = self.api.client.get(url)

        if obj_class is None:
            obj_class = self.resource_class

        data = body[response_key]
        # NOTE(ja): keystone returns values as list as {'values': [ ... ]}
        #           unlike other services which just return the list...
        if isinstance(data, dict):
            try:
                data = data['values']
            except KeyError:
                pass

        with self.completion_cache('human_id', obj_class, mode="w"):
            with self.completion_cache('uuid', obj_class, mode="w"):
                items_new = [obj_class(self, res, loaded=True)
                             for res in data if res]
        if limit:
            limit = int(limit)
            margin = limit - len(items)
            if margin <= len(items_new):
                # If the limit is reached, return the items.
                items = items + items_new[:margin]
                return items
            else:
                items = items + items_new
        else:
            items = items + items_new

        # It is possible that the length of the list we request is longer
        # than osapi_max_limit, so we have to retrieve multiple times to
        # get the complete list.
        next = None
        if 'volumes_links' in body:
            volumes_links = body['volumes_links']
            if volumes_links:
                for volumes_link in volumes_links:
                    if 'rel' in volumes_link and 'next' == volumes_link['rel']:
                        next = volumes_link['href']
                        break
            if next:
                # As long as the 'next' link is not empty, keep requesting it
                # till there is no more items.
                items = self._list(next, response_key, obj_class, None,
                                   limit, items)
        return items

    @contextlib.contextmanager
    def completion_cache(self, cache_type, obj_class, mode):
        """
        The completion cache store items that can be used for bash
        autocompletion, like UUIDs or human-friendly IDs.

        A resource listing will clear and repopulate the cache.

        A resource create will append to the cache.

        Delete is not handled because listings are assumed to be performed
        often enough to keep the cache reasonably up-to-date.
        """
        base_dir = utils.env('CINDERCLIENT_UUID_CACHE_DIR',
                             default="~/.cinderclient")

        # NOTE(sirp): Keep separate UUID caches for each username + endpoint
        # pair
        username = utils.env('OS_USERNAME', 'CINDER_USERNAME')
        url = utils.env('OS_URL', 'CINDER_URL')
        uniqifier = hashlib.md5(username.encode('utf-8') +
                                url.encode('utf-8')).hexdigest()

        cache_dir = os.path.expanduser(os.path.join(base_dir, uniqifier))

        try:
            os.makedirs(cache_dir, 0o755)
        except OSError:
            # NOTE(kiall): This is typically either permission denied while
            #              attempting to create the directory, or the directory
            #              already exists. Either way, don't fail.
            pass

        resource = obj_class.__name__.lower()
        filename = "%s-%s-cache" % (resource, cache_type.replace('_', '-'))
        path = os.path.join(cache_dir, filename)

        cache_attr = "_%s_cache" % cache_type

        try:
            setattr(self, cache_attr, open(path, mode))
        except IOError:
            # NOTE(kiall): This is typically a permission denied while
            #              attempting to write the cache file.
            pass

        try:
            yield
        finally:
            cache = getattr(self, cache_attr, None)
            if cache:
                cache.close()
                delattr(self, cache_attr)

    def write_to_completion_cache(self, cache_type, val):
        cache = getattr(self, "_%s_cache" % cache_type, None)
        if cache:
            cache.write("%s\n" % val)

    def _get(self, url, response_key=None):
        resp, body = self.api.client.get(url)
        if response_key:
            return self.resource_class(self, body[response_key], loaded=True)
        else:
            return self.resource_class(self, body, loaded=True)

    def _create(self, url, body, response_key, return_raw=False, **kwargs):
        self.run_hooks('modify_body_for_create', body, **kwargs)
        resp, body = self.api.client.post(url, body=body)
        if return_raw:
            return body[response_key]

        with self.completion_cache('human_id', self.resource_class, mode="a"):
            with self.completion_cache('uuid', self.resource_class, mode="a"):
                return self.resource_class(self, body[response_key])

    def _delete(self, url):
        resp, body = self.api.client.delete(url)

    def _update(self, url, body, response_key=None, **kwargs):
        self.run_hooks('modify_body_for_update', body, **kwargs)
        resp, body = self.api.client.put(url, body=body)
        if response_key:
            return self.resource_class(self, body[response_key], loaded=True)
        return body


class ManagerWithFind(six.with_metaclass(abc.ABCMeta, Manager)):
    """
    Like a `Manager`, but with additional `find()`/`findall()` methods.
    """

    @abc.abstractmethod
    def list(self):
        pass

    def find(self, **kwargs):
        """
        Find a single item with attributes matching ``**kwargs``.

        This isn't very efficient for search options which require the
        Python side filtering(e.g. 'human_id')
        """
        matches = self.findall(**kwargs)
        num_matches = len(matches)
        if num_matches == 0:
            msg = "No %s matching %s." % (self.resource_class.__name__, kwargs)
            raise exceptions.NotFound(404, msg)
        elif num_matches > 1:
            raise exceptions.NoUniqueMatch
        else:
            return matches[0]

    def findall(self, **kwargs):
        """
        Find all items with attributes matching ``**kwargs``.

        This isn't very efficient for search options which require the
        Python side filtering(e.g. 'human_id')
        """

        # Want to search for all tenants here so that when attempting to delete
        # that a user like admin doesn't get a failure when trying to delete
        # another tenant's volume by name.
        search_opts = {'all_tenants': 1}

        # Pass 'name' or 'display_name' search_opts to server filtering to
        # increase search performance.
        if 'name' in kwargs:
            search_opts['name'] = kwargs['name']
        elif 'display_name' in kwargs:
            search_opts['display_name'] = kwargs['display_name']

        found = []
        searches = kwargs.items()

        # Not all resources attributes support filters on server side
        # (e.g. 'human_id' doesn't), so when doing findall some client
        # side filtering is still needed.
        for obj in self.list(search_opts=search_opts):
            try:
                if all(getattr(obj, attr) == value
                       for (attr, value) in searches):
                    found.append(obj)
            except AttributeError:
                continue

        return found
