# Copyright (c) 2013 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.

import abc

from neutron_lib.api import extensions as api_extensions
from neutron_lib.api import faults
from neutron_lib import constants
from neutron_lib import exceptions
from neutron_lib.exceptions import agent as agent_exc
from neutron_lib.plugins import constants as plugin_constants
from neutron_lib.plugins import directory
from neutron_lib import rpc as n_rpc
from oslo_log import log as logging
import webob.exc

from neutron._i18n import _
from neutron.api import extensions
from neutron.api.v2 import resource
from neutron.api import wsgi
from neutron import policy

LOG = logging.getLogger(__name__)

L3_ROUTER = 'l3-router'
L3_ROUTERS = L3_ROUTER + 's'
L3_AGENT = 'l3-agent'
L3_AGENTS = L3_AGENT + 's'


class RouterSchedulerController(wsgi.Controller):
    def get_plugin(self):
        plugin = directory.get_plugin(plugin_constants.L3)
        if not plugin:
            LOG.error('No plugin for L3 routing registered to handle '
                      'router scheduling')
            msg = _('The resource could not be found.')
            raise webob.exc.HTTPNotFound(msg)
        return plugin

    def index(self, request, **kwargs):
        plugin = self.get_plugin()
        policy.enforce(request.context,
                       "get_%s" % L3_ROUTERS,
                       {})
        return plugin.list_routers_on_l3_agent(
            request.context, kwargs['agent_id'])

    def create(self, request, body, **kwargs):
        plugin = self.get_plugin()
        policy.enforce(request.context,
                       "create_%s" % L3_ROUTER,
                       {})
        agent_id = kwargs['agent_id']
        router_id = body['router_id']
        result = plugin.add_router_to_l3_agent(request.context, agent_id,
                                               router_id)
        notify(request.context, 'l3_agent.router.add', router_id, agent_id)
        return result

    def delete(self, request, id, **kwargs):
        plugin = self.get_plugin()
        policy.enforce(request.context,
                       "delete_%s" % L3_ROUTER,
                       {})
        agent_id = kwargs['agent_id']
        result = plugin.remove_router_from_l3_agent(request.context, agent_id,
                                                    id)
        notify(request.context, 'l3_agent.router.remove', id, agent_id)
        return result


class L3AgentsHostingRouterController(wsgi.Controller):
    def get_plugin(self):
        plugin = directory.get_plugin(plugin_constants.L3)
        if not plugin:
            LOG.error('No plugin for L3 routing registered to handle '
                      'router scheduling')
            msg = _('The resource could not be found.')
            raise webob.exc.HTTPNotFound(msg)
        return plugin

    def index(self, request, **kwargs):
        plugin = self.get_plugin()
        policy.enforce(request.context,
                       "get_%s" % L3_AGENTS,
                       {})
        return plugin.list_l3_agents_hosting_router(
            request.context, kwargs['router_id'])


class L3agentscheduler(api_extensions.ExtensionDescriptor):
    """Extension class supporting l3 agent scheduler.
    """

    @classmethod
    def get_name(cls):
        return "L3 Agent Scheduler"

    @classmethod
    def get_alias(cls):
        return constants.L3_AGENT_SCHEDULER_EXT_ALIAS

    @classmethod
    def get_description(cls):
        return "Schedule routers among l3 agents"

    @classmethod
    def get_updated(cls):
        return "2013-02-07T10:00:00-00:00"

    @classmethod
    def get_resources(cls):
        """Returns Ext Resources."""
        exts = []
        parent = dict(member_name="agent",
                      collection_name="agents")

        controller = resource.Resource(RouterSchedulerController(),
                                       faults.FAULT_MAP)
        exts.append(extensions.ResourceExtension(
            L3_ROUTERS, controller, parent))

        parent = dict(member_name="router",
                      collection_name="routers")

        controller = resource.Resource(L3AgentsHostingRouterController(),
                                       faults.FAULT_MAP)
        exts.append(extensions.ResourceExtension(
            L3_AGENTS, controller, parent))
        return exts

    def get_extended_resources(self, version):
        return {}


class InvalidL3Agent(agent_exc.AgentNotFound):
    message = _("Agent %(id)s is not a L3 Agent or has been disabled")


class RouterHostedByL3Agent(exceptions.Conflict):
    message = _("The router %(router_id)s has been already hosted "
                "by the L3 Agent %(agent_id)s.")


class RouterSchedulingFailed(exceptions.Conflict):
    message = _("Failed scheduling router %(router_id)s to "
                "the L3 Agent %(agent_id)s.")


class RouterReschedulingFailed(exceptions.Conflict):
    message = _("Failed rescheduling router %(router_id)s: "
                "no eligible l3 agent found.")


class RouterL3AgentMismatch(exceptions.Conflict):
    message = _("Cannot host distributed router %(router_id)s "
                "on legacy L3 agent %(agent_id)s.")


class DVRL3CannotAssignToDvrAgent(exceptions.Conflict):
    message = _("Not allowed to manually assign a router to an "
                "agent in 'dvr' mode.")


class DVRL3CannotRemoveFromDvrAgent(exceptions.Conflict):
    message = _("Not allowed to manually remove a router from "
                "an agent in 'dvr' mode.")


class RouterDoesntSupportScheduling(exceptions.Conflict):
    message = _("Router %(router_id)s does not support agent scheduling.")


class L3AgentSchedulerPluginBase(metaclass=abc.ABCMeta):
    """REST API to operate the l3 agent scheduler.

    All of method must be in an admin context.
    """

    @abc.abstractmethod
    def add_router_to_l3_agent(self, context, id, router_id):
        pass

    @abc.abstractmethod
    def remove_router_from_l3_agent(self, context, id, router_id):
        pass

    @abc.abstractmethod
    def list_routers_on_l3_agent(self, context, id):
        pass

    @abc.abstractmethod
    def list_l3_agents_hosting_router(self, context, router_id):
        pass

    def router_supports_scheduling(self, context, router_id):
        """Override this method to conditionally schedule routers."""
        return True


def notify(context, action, router_id, agent_id):
    info = {'id': agent_id, 'router_id': router_id}
    notifier = n_rpc.get_notifier('router')
    notifier.info(context, action, {'agent': info})
