# Copyright 2012 OpenStack Foundation
# Copyright 2015 Objectif Libre
# 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 copy

from six.moves.urllib import parse

from cloudkittyclient import exc
from cloudkittyclient.i18n import _
from cloudkittyclient.openstack.common.apiclient import base


def getid(obj):
    """Extracts object ID.

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


class Manager(object):
    """Managers interact with a particular type of API.

    It works with samples, meters, alarms, etc. and provide CRUD operations for
    them.
    """
    resource_class = None

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

    @property
    def client(self):
        """Compatible with latest oslo-incubator.apiclient code."""
        return self.api

    def _create(self, url, body):
        body = self.api.post(url, json=body).json()
        if body:
            return self.resource_class(self, body)

    def _list(self, url, response_key=None, obj_class=None, body=None,
              expect_single=False):
        resp = self.api.get(url)
        if not resp.content:
            raise exc.HTTPNotFound
        body = resp.json()

        if obj_class is None:
            obj_class = self.resource_class

        if response_key:
            try:
                data = body[response_key]
            except KeyError:
                return []
        else:
            data = body
        if expect_single:
            data = [data]
        return [obj_class(self, res, loaded=True) for res in data if res]

    def _update(self, url, item, response_key=None):
        if not item.dirty_fields:
            return item
        item = self.api.put(url, json=item.dirty_fields).json()
        # PUT requests may not return a item
        if item:
            return self.resource_class(self, item)

    def _delete(self, url):
        self.api.delete(url)


class CrudManager(base.CrudManager):
    """A CrudManager that automatically gets its base URL."""

    base_url = None

    def build_url(self, base_url=None, **kwargs):
        base_url = base_url or self.base_url
        return super(CrudManager, self).build_url(base_url, **kwargs)

    def get(self, **kwargs):
        kwargs = self._filter_kwargs(kwargs)
        return self._get(
            self.build_url(**kwargs))

    def create(self, **kwargs):
        kwargs = self._filter_kwargs(kwargs)
        return self._post(
            self.build_url(**kwargs), kwargs)

    def update(self, **kwargs):
        kwargs = self._filter_kwargs(kwargs)
        params = kwargs.copy()

        return self._put(
            self.build_url(**kwargs), params)

    def findall(self, base_url=None, **kwargs):
        """Find multiple items with attributes matching ``**kwargs``.

        :param base_url: if provided, the generated URL will be appended to it
        """
        kwargs = self._filter_kwargs(kwargs)

        rl = self._list(
            '%(base_url)s%(query)s' % {
                'base_url': self.build_url(base_url=base_url, **kwargs),
                'query': '?%s' % parse.urlencode(kwargs) if kwargs else '',
            },
            self.collection_key)
        num = len(rl)

        if num == 0:
            msg = _("No %(name)s matching %(args)s.") % {
                'name': self.resource_class.__name__,
                'args': kwargs
            }
            raise exc.HTTPNotFound(msg)
        return rl


class Resource(base.Resource):
    """A resource represents a particular instance of an object.

    Resource might be tenant, user, etc.
    This is pretty much just a bag for attributes.

    :param manager: Manager object
    :param info: dictionary representing resource attributes
    :param loaded: prevent lazy-loading if set to True
    """

    key = None

    def to_dict(self):
        return copy.deepcopy(self._info)

    @property
    def dirty_fields(self):
        out = self.to_dict()
        for k, v in self._info.items():
            if self.__dict__[k] != v:
                out[k] = self.__dict__[k]
        return out

    def update(self):
        try:
            return self.manager.update(**self.dirty_fields)
        except AttributeError:
            raise exc.NotUpdatableError(self)