#    (c) Copyright 2014 Hewlett-Packard Development Company, L.P.
#    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 random

import sqlalchemy as sa
from sqlalchemy import orm
from sqlalchemy.orm import exc
from sqlalchemy.orm import joinedload

from neutron.common import constants as q_const
from neutron.common import utils as n_utils
from neutron.db import agents_db
from neutron.db import l3_agentschedulers_db as l3agent_sch_db
from neutron.db import model_base
from neutron.db import models_v2
from neutron.openstack.common import log as logging
from neutron.plugins.ml2 import db as ml2_db

LOG = logging.getLogger(__name__)


class CentralizedSnatL3AgentBinding(model_base.BASEV2):
    """Represents binding between Neutron Centralized SNAT and L3 agents."""

    __tablename__ = "csnat_l3_agent_bindings"

    router_id = sa.Column(sa.String(36),
                          sa.ForeignKey("routers.id", ondelete='CASCADE'),
                          primary_key=True)
    l3_agent_id = sa.Column(sa.String(36),
                            sa.ForeignKey("agents.id", ondelete='CASCADE'),
                            nullable=False)
    host_id = sa.Column(sa.String(255))
    csnat_gw_port_id = sa.Column(sa.String(36), sa.ForeignKey('ports.id'))

    l3_agent = orm.relationship(agents_db.Agent)
    csnat_gw_port = orm.relationship(models_v2.Port)


class L3_DVRsch_db_mixin(l3agent_sch_db.L3AgentSchedulerDbMixin):
    """Mixin class for L3 DVR scheduler.

    DVR currently supports the following use cases:

     - East/West (E/W) traffic between VMs: this is handled in a
       distributed manner across Compute Nodes without a centralized element.
       This includes E/W traffic between VMs on the same Compute Node.
     - North/South traffic for Floating IPs (FIP N/S): this is supported on the
       distributed routers on Compute Nodes without any centralized element.
     - North/South traffic for SNAT (SNAT N/S): this is supported via a
       centralized element that handles the SNAT traffic.

    To support these use cases,  DVR routers rely on an L3 agent that runs on a
    central node (also known as Network Node or Service Node),  as well as, L3
    agents that run individually on each Compute Node of an OpenStack cloud.

    Each L3 agent creates namespaces to route traffic according to the use
    cases outlined above.  The mechanism adopted for creating and managing
    these namespaces is via (Router,  Agent) binding and Scheduling in general.

    The main difference between distributed routers and centralized ones is
    that in the distributed case,  multiple bindings will exist,  one for each
    of the agents participating in the routed topology for the specific router.

    These bindings are created in the following circumstances:

    - A subnet is added to a router via router-interface-add, and that subnet
      has running VM's deployed in it.  A binding will be created between the
      router and any L3 agent whose Compute Node is hosting the VM(s).
    - An external gateway is set to a router via router-gateway-set.  A binding
      will be created between the router and the L3 agent running centrally
      on the Network Node.

    Therefore,  any time a router operation occurs (create, update or delete),
    scheduling will determine whether the router needs to be associated to an
    L3 agent, just like a regular centralized router, with the difference that,
    in the distributed case,  the bindings required are established based on
    the state of the router and the Compute Nodes.
    """

    def dvr_update_router_addvm(self, context, port):
        ips = port['fixed_ips']
        for ip in ips:
            subnet = ip['subnet_id']
            filter_sub = {'fixed_ips': {'subnet_id': [subnet]},
                          'device_owner':
                          [q_const.DEVICE_OWNER_DVR_INTERFACE]}
            router_id = None
            ports = self._core_plugin.get_ports(context, filters=filter_sub)
            for port in ports:
                router_id = port['device_id']
                router_dict = self.get_router(context, router_id)
                if router_dict.get('distributed', False):
                    payload = {'subnet_id': subnet}
                    self.l3_rpc_notifier.routers_updated(
                        context, [router_id], None, payload)
                    break
            LOG.debug('DVR: dvr_update_router_addvm %s ', router_id)

    def get_dvr_routers_by_portid(self, context, port_id):
        """Gets the dvr routers on vmport subnets."""
        router_ids = set()
        port_dict = self._core_plugin.get_port(context, port_id)
        fixed_ips = port_dict['fixed_ips']
        for fixedip in fixed_ips:
            vm_subnet = fixedip['subnet_id']
            filter_sub = {'fixed_ips': {'subnet_id': [vm_subnet]},
                          'device_owner':
                          [q_const.DEVICE_OWNER_DVR_INTERFACE]}
            subnet_ports = self._core_plugin.get_ports(
                context, filters=filter_sub)
            for subnet_port in subnet_ports:
                router_ids.add(subnet_port['device_id'])
        return router_ids

    def get_subnet_ids_on_router(self, context, router_id):
        """Return subnet IDs for interfaces attached to the given router."""
        subnet_ids = set()
        filter_rtr = {'device_id': [router_id]}
        int_ports = self._core_plugin.get_ports(context, filters=filter_rtr)
        for int_port in int_ports:
            int_ips = int_port['fixed_ips']
            int_subnet = int_ips[0]['subnet_id']
            subnet_ids.add(int_subnet)
        return subnet_ids

    def check_ports_active_on_host_and_subnet(self, context, host,
                                         port_id, subnet_id):
        """Check if there is any dvr serviceable port on the subnet_id."""
        filter_sub = {'fixed_ips': {'subnet_id': [subnet_id]}}
        ports = self._core_plugin.get_ports(context, filters=filter_sub)
        for port in ports:
            if (n_utils.is_dvr_serviced(port['device_owner'])
                and port['status'] == 'ACTIVE'
                and port['binding:host_id'] == host
                and port['id'] != port_id):
                LOG.debug('DVR: Active port exists for subnet %(subnet_id)s '
                          'on host %(host)s', {'subnet_id': subnet_id,
                                       'host': host})
                return True
        return False

    def dvr_deletens_if_no_port(self, context, port_id):
        """Delete the DVR namespace if no dvr serviced port exists."""
        router_ids = self.get_dvr_routers_by_portid(context, port_id)
        port_host = ml2_db.get_port_binding_host(port_id)
        if not router_ids:
            LOG.debug('No namespaces available for this DVR port %(port)s '
                      'on host %(host)s', {'port': port_id,
                                           'host': port_host})
            return []
        removed_router_info = []
        for router_id in router_ids:
            subnet_ids = self.get_subnet_ids_on_router(context, router_id)
            port_exists_on_subnet = False
            for subnet in subnet_ids:
                if self.check_ports_active_on_host_and_subnet(context,
                                                              port_host,
                                                              port_id,
                                                              subnet):
                    port_exists_on_subnet = True
                    break

            if port_exists_on_subnet:
                continue
            filter_rtr = {'device_id': [router_id],
                          'device_owner':
                          [q_const.DEVICE_OWNER_DVR_INTERFACE]}
            int_ports = self._core_plugin.get_ports(
                context, filters=filter_rtr)
            for prt in int_ports:
                dvr_binding = (ml2_db.
                               get_dvr_port_binding_by_host(context.session,
                                                            prt['id'],
                                                            port_host))
                if dvr_binding:
                    # unbind this port from router
                    dvr_binding['router_id'] = None
                    dvr_binding.update(dvr_binding)
            agent = self._get_agent_by_type_and_host(context,
                                                     q_const.AGENT_TYPE_L3,
                                                     port_host)
            info = {'router_id': router_id, 'host': port_host,
                    'agent_id': str(agent.id)}
            removed_router_info.append(info)
            LOG.debug('Router namespace %(router_id)s on host %(host)s '
                      'to be deleted', info)
        return removed_router_info

    def bind_snat_router(self, context, router_id, chosen_agent):
        """Bind the router to the chosen l3 agent."""
        with context.session.begin(subtransactions=True):
            binding = CentralizedSnatL3AgentBinding()
            binding.l3_agent = chosen_agent
            binding.router_id = router_id
            context.session.add(binding)
            LOG.debug('SNAT Router %(router_id)s is scheduled to L3 agent '
                      '%(agent_id)s', {'router_id': router_id,
                                       'agent_id': chosen_agent.id})

    def bind_dvr_router_servicenode(self, context, router_id,
                                    chosen_snat_agent):
        """Bind the IR router to service node if not already hosted."""
        query = (context.session.query(l3agent_sch_db.RouterL3AgentBinding).
                 filter_by(router_id=router_id))
        for bind in query:
            if bind.l3_agent_id == chosen_snat_agent.id:
                LOG.debug('Distributed Router %(router_id)s already hosted '
                          'on snat l3_agent %(snat_id)s',
                          {'router_id': router_id,
                           'snat_id': chosen_snat_agent.id})
                return
        with context.session.begin(subtransactions=True):
            binding = l3agent_sch_db.RouterL3AgentBinding()
            binding.l3_agent = chosen_snat_agent
            binding.router_id = router_id
            context.session.add(binding)
            LOG.debug('Binding the distributed router %(router_id)s to '
                      'the snat agent %(snat_id)s',
                      {'router_id': router_id,
                       'snat_id': chosen_snat_agent.id})

    def bind_snat_servicenode(self, context, router_id, snat_candidates):
        """Bind the snat router to the chosen l3 service agent."""
        chosen_snat_agent = random.choice(snat_candidates)
        self.bind_snat_router(context, router_id, chosen_snat_agent)
        return chosen_snat_agent

    def unbind_snat_servicenode(self, context, router_id):
        """Unbind the snat router to the chosen l3 service agent."""
        vm_ports = []
        with context.session.begin(subtransactions=True):
            query = (context.session.
                     query(CentralizedSnatL3AgentBinding).
                     filter_by(router_id=router_id))
            try:
                binding = query.one()
            except exc.NoResultFound:
                LOG.debug('no snat router binding found for %s', router_id)
                return

            host = binding.l3_agent.host
            subnet_ids = self.get_subnet_ids_on_router(context, router_id)
            for subnet in subnet_ids:
                vm_ports = (
                    self._core_plugin.get_ports_on_host_by_subnet(
                        context, host, subnet))
                if vm_ports:
                    LOG.debug('One or more ports exist on the snat enabled '
                              'l3_agent host %(host)s and router_id %(id)s',
                              {'host': host, 'id': router_id})
                    break
            agent_id = binding.l3_agent_id
            LOG.debug('Delete binding of the SNAT router %(router_id)s '
                      'from agent %(id)s', {'router_id': router_id,
                                            'id': agent_id})
            context.session.delete(binding)

            if not vm_ports:
                query = (context.session.
                         query(l3agent_sch_db.RouterL3AgentBinding).
                         filter_by(router_id=router_id,
                                   l3_agent_id=agent_id).
                         delete(synchronize_session=False))
        self.l3_rpc_notifier.router_removed_from_agent(
            context, router_id, host)
        LOG.debug('Removed binding for router %(router_id)s and '
                  'agent %(id)s', {'router_id': router_id, 'id': agent_id})

    def get_snat_bindings(self, context, router_ids):
        """ Retrieves the dvr snat bindings for a router."""
        if not router_ids:
            return []
        query = context.session.query(CentralizedSnatL3AgentBinding)
        query = query.options(joinedload('l3_agent')).filter(
            CentralizedSnatL3AgentBinding.router_id.in_(router_ids))
        return query.all()

    def schedule_snat_router(self, context, router_id, sync_router):
        """Schedule the snat router on l3 service agent."""
        active_l3_agents = self.get_l3_agents(context, active=True)
        if not active_l3_agents:
            LOG.warn(_('No active L3 agents found for SNAT'))
            return
        snat_candidates = self.get_snat_candidates(sync_router,
                                                   active_l3_agents)
        if snat_candidates:
            chosen_agent = self.bind_snat_servicenode(
                context, router_id, snat_candidates)
            self.bind_dvr_router_servicenode(
                context, router_id, chosen_agent)
