# 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 os

import netaddr
from oslo_concurrency import processutils
from oslo_utils import excutils
import pyroute2

from kuryr.common import config
from kuryr.common import exceptions


CONTAINER_VETH_POSTFIX = '_c'
BINDING_SUBCOMMAND = 'bind'
DOWN = 'DOWN'
FALLBACK_VIF_TYPE = 'unbound'
FIXED_IP_KEY = 'fixed_ips'
IFF_UP = 0x1  # The last bit represents if the interface is up
IP_ADDRESS_KEY = 'ip_address'
KIND_VETH = 'veth'
MAC_ADDRESS_KEY = 'mac_address'
SUBNET_ID_KEY = 'subnet_id'
UNBINDING_SUBCOMMAND = 'unbind'
VETH_POSTFIX = '-veth'
VIF_TYPE_KEY = 'binding:vif_type'


def _is_up(interface):
    flags = interface['flags']
    if not flags:
        return False
    return (flags & IFF_UP) == 1


def cleanup_veth(ifname):
    """Cleans the veth passed as an argument up.

    :param ifname: the name of the veth endpoint
    :returns: the index of the interface which name is the given ifname if it
              exists, otherwise None
    :raises: pyroute2.netlink.NetlinkError
    """
    ipr = pyroute2.IPRoute()
    veths = ipr.link_lookup(ifname=ifname)
    if veths:
        host_veth_index = veths[0]
        ipr.link_remove(host_veth_index)
        return host_veth_index
    else:
        return None


def port_bind(endpoint_id, neutron_port, neutron_subnets):
    """Binds the Neutron port to the network interface on the host.

    :param endpoint_id:     the ID of the endpoint as string
    :param neutron_port:    a port dictionary returned from
                            python-neutronclient
    :param neutron_subnets: a list of all subnets under network to which this
                            endpoint is trying to join
    :returns: the tuple of the names of the veth pair and the tuple of stdout
              and stderr returned by processutils.execute invoked with the
              executable script for binding
    :raises: kuryr.common.exceptions.VethCreationFailure,
             processutils.ProcessExecutionError
    """
    # NOTE(tfukushima): pyroute2.ipdb requires Linux to be imported. So I don't
    # import it in the module scope but here.
    import pyroute2.ipdb

    ifname = endpoint_id[:8] + VETH_POSTFIX
    peer_name = ifname + CONTAINER_VETH_POSTFIX
    subnets_dict = {subnet['id']: subnet for subnet in neutron_subnets}

    ip = pyroute2.IPDB()
    try:
        with ip.create(ifname=ifname, kind=KIND_VETH,
                       reuse=True, peer=peer_name) as host_veth:
            if not _is_up(host_veth):
                host_veth.up()
        with ip.interfaces[peer_name] as peer_veth:
            fixed_ips = neutron_port.get(FIXED_IP_KEY, [])
            if not fixed_ips and (IP_ADDRESS_KEY in neutron_port):
                peer_veth.add_ip(neutron_port[IP_ADDRESS_KEY])
            for fixed_ip in fixed_ips:
                if IP_ADDRESS_KEY in fixed_ip and (SUBNET_ID_KEY in fixed_ip):
                    subnet_id = fixed_ip[SUBNET_ID_KEY]
                    subnet = subnets_dict[subnet_id]
                    cidr = netaddr.IPNetwork(subnet['cidr'])
                    peer_veth.add_ip(fixed_ip[IP_ADDRESS_KEY], cidr.prefixlen)
            peer_veth.address = neutron_port[MAC_ADDRESS_KEY].lower()
            if not _is_up(peer_veth):
                peer_veth.up()
    except pyroute2.ipdb.common.CreateException:
        raise exceptions.VethCreationFailure(
            'Creating the veth pair was failed.')
    except pyroute2.ipdb.common.CommitException:
        raise exceptions.VethCreationFailure(
            'Could not configure the veth endpoint for the container.')
    finally:
        ip.release()

    vif_type = neutron_port.get(VIF_TYPE_KEY, FALLBACK_VIF_TYPE)
    binding_exec_path = os.path.join(config.CONF.bindir, vif_type)
    port_id = neutron_port['id']
    try:
        stdout, stderr = processutils.execute(
            binding_exec_path, BINDING_SUBCOMMAND, port_id, ifname,
            endpoint_id, run_as_root=True)
    except processutils.ProcessExecutionError:
        with excutils.save_and_reraise_exception():
            cleanup_veth(ifname)

    return (ifname, peer_name, (stdout, stderr))


def port_unbind(endpoint_id, neutron_port):
    """Unbinds the Neutron port from the network interface on the host.

    :param endpoint_id: the ID of the Docker container as string
    :param neutron_port: a port dictionary returned from python-neutronclient
    :returns: the tuple of stdout and stderr returned by processutils.execute
              invoked with the executable script for unbinding
    :raises: processutils.ProcessExecutionError, pyroute2.netlink.NetlinkError
    """
    # NOTE(tfukushima): pyroute2.netlink requires Linux to be imported. So I
    # don't import it in the module scope but here.
    import pyroute2.netlink

    vif_type = neutron_port.get(VIF_TYPE_KEY, FALLBACK_VIF_TYPE)
    unbinding_exec_path = os.path.join(config.CONF.bindir, vif_type)
    port_id = neutron_port['id']
    stdout, stderr = processutils.execute(
        unbinding_exec_path, UNBINDING_SUBCOMMAND, port_id, run_as_root=True)
    ifname = endpoint_id[:8] + VETH_POSTFIX
    try:
        cleanup_veth(ifname)
    except pyroute2.netlink.NetlinkError:
        raise exceptions.VethDeleteionFailure(
            'Deleting the veth pair was failed.')
    return (stdout, stderr)