# Copyright (c) 2014 Mirantis Inc.
#
# 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 math

import netaddr
from netaddr.strategy import ipv4
from oslo_config import cfg
from oslo_log import log as logging
from oslo_utils import uuidutils

from murano.common.i18n import _LI
from murano.dsl import dsl
from murano.dsl import helpers

CONF = cfg.CONF
LOG = logging.getLogger(__name__)


@dsl.name('io.murano.system.NetworkExplorer')
class NetworkExplorer(object):
    def __init__(self):
        environment = helpers.get_environment()
        self._clients = environment.clients
        self._tenant_id = environment.tenant_id
        self._settings = CONF.networking
        self._available_cidrs = self._generate_possible_cidrs()

    def get_default_router(self):
        client = self._clients.get_neutron_client()
        router_name = self._settings.router_name

        routers = client.list_routers(
            tenant_id=self._tenant_id, name=router_name).get('routers')
        if len(routers) == 0:
            LOG.debug('Router {name} not found'.format(name=router_name))
            if self._settings.create_router:
                LOG.debug('Attempting to create Router {router}'.
                          format(router=router_name))
                external_network = self._settings.external_network
                kwargs = {'id': external_network} \
                    if uuidutils.is_uuid_like(external_network) \
                    else {'name': external_network}
                networks = client.list_networks(**kwargs).get('networks')
                ext_nets = filter(lambda n: n['router:external'], networks)
                if len(ext_nets) == 0:
                    raise KeyError('Router %s could not be created, '
                                   'no external network found' % router_name)
                nid = ext_nets[0]['id']

                body_data = {
                    'router': {
                        'name': router_name,
                        'external_gateway_info': {
                            'network_id': nid
                        },
                        'admin_state_up': True,
                    }
                }
                router = client.create_router(body=body_data).get('router')
                LOG.info(_LI('Created router: {id}').format(id=router['id']))
                return router['id']
            else:
                raise KeyError('Router %s was not found' % router_name)
        else:
            if routers[0]['external_gateway_info'] is None:
                raise Exception('Please set external gateway '
                                'for the router %s ' % router_name)
            router_id = routers[0]['id']
        return router_id

    def get_available_cidr(self, router_id, net_id):
        """Uses hash of network IDs to minimize the collisions:
        different nets will attempt to pick different cidrs out of available
        range.
        If the cidr is taken will pick another one
        """
        taken_cidrs = self._get_cidrs_taken_by_router(router_id)
        id_hash = hash(net_id)
        num_fails = 0
        while num_fails < len(self._available_cidrs):
            cidr = self._available_cidrs[
                (id_hash + num_fails) % len(self._available_cidrs)]
            if any(self._cidrs_overlap(cidr, taken_cidr) for taken_cidr in
                   taken_cidrs):
                num_fails += 1
            else:
                return str(cidr)
        return None

    def get_default_dns(self):
        return self._settings.default_dns

    def get_external_network_id_for_router(self, router_id):
        client = self._clients.get_neutron_client()
        router = client.show_router(router_id).get('router')
        if not router or 'external_gateway_info' not in router:
            return None
        return router['external_gateway_info'].get('network_id')

    def get_external_network_id_for_network(self, network_id):
        client = self._clients.get_neutron_client()
        network = client.show_network(network_id).get('network')
        if network.get('router:external', False):
            return network_id

        # Get router interfaces of the network
        router_ports = client.list_ports(
            **{'device_owner': 'network:router_interface',
               'network_id': network_id}).get('ports')

        # For each router this network is connected to
        # check if the router has external_gateway set
        for router_port in router_ports:
            ext_net_id = self.getExternalNetworkIdForRouter(
                router_port.get('device_id'))
            if ext_net_id:
                return ext_net_id
        return None

    def _get_cidrs_taken_by_router(self, router_id):
        if not router_id:
            return []
        client = self._clients.get_neutron_client()
        ports = client.list_ports(device_id=router_id)['ports']
        subnet_ids = []
        for port in ports:
            for fixed_ip in port['fixed_ips']:
                subnet_ids.append(fixed_ip['subnet_id'])

        all_subnets = client.list_subnets()['subnets']
        filtered_cidrs = [netaddr.IPNetwork(subnet['cidr']) for subnet in
                          all_subnets if subnet['id'] in subnet_ids]

        return filtered_cidrs

    @staticmethod
    def _cidrs_overlap(cidr1, cidr2):
        return (cidr1 in cidr2) or (cidr2 in cidr1)

    def _generate_possible_cidrs(self):
        bits_for_envs = int(
            math.ceil(math.log(self._settings.max_environments, 2)))
        bits_for_hosts = int(math.ceil(math.log(self._settings.max_hosts, 2)))
        width = ipv4.width
        mask_width = width - bits_for_hosts - bits_for_envs
        net = netaddr.IPNetwork(
            '{0}/{1}'.format(self._settings.env_ip_template, mask_width))
        return list(net.subnet(width - bits_for_hosts))

    def list_networks(self):
        client = self._clients.get_neutron_client()
        return client.list_networks()['networks']

    def list_subnetworks(self):
        client = self._clients.get_neutron_client()
        return client.list_subnets()['subnets']
