#!/usr/bin/env python3
#
# Copyright (C) 2020 VyOS maintainers and contributors
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or later as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import os

from sys import exit
from copy import deepcopy
from subprocess import check_call, CalledProcessError
from vyos.config import Config
from vyos.configdict import list_diff
from vyos import ConfigError

default_config_data = {
    'vrf_add': [],
    'vrf_existing': [],
    'vrf_remove': []
}

def _cmd(command):
    """
    Run any arbitrary command on the system
    """
    try:
        check_call(command.split())
    except CalledProcessError as e:
        pass
        raise ConfigError(f'Error operationg on VRF: {e}')


def interfaces_with_vrf(match):
    matched = []
    config = Config()
    section = config.get_config_dict('interfaces')
    for type in section:
        interfaces = section[type]
        for name in interfaces:
            interface = interfaces[name]
            if 'vrf' in interface:
                v = interface.get('vrf', '')
                if v == match:
                    matched.append(name)
    return matched


def get_config():
    conf = Config()
    vrf_config = deepcopy(default_config_data)

    cfg_base = ['vrf']
    if not conf.exists(cfg_base):
        # get all currently effetive VRFs and mark them for deletion
        vrf_config['vrf_remove'] = conf.list_effective_nodes(cfg_base + ['name'])
        return vrf_config

    # Determine vrf interfaces (currently effective) - to determine which
    # vrf interface is no longer present and needs to be removed
    eff_vrf = conf.list_effective_nodes(cfg_base + ['name'])
    act_vrf = conf.list_nodes(cfg_base + ['name'])
    vrf_config['vrf_remove'] = list_diff(eff_vrf, act_vrf)

    # read in individual VRF definition and build up
    # configuration
    for name in conf.list_nodes(cfg_base + ['name']):
        vrf_inst = {
            'description' : '\0',
            'members': [],
            'name' : name,
            'table' : '',
            'table_mod': False
        }
        conf.set_level(cfg_base + ['name', name])

        if conf.exists(['table']):
            # VRF table can't be changed on demand, thus we need to read in the
            # current and the effective routing table number
            act_table = conf.return_value(['table'])
            eff_table = conf.return_effective_value(['table'])
            vrf_inst['table'] = act_table
            if eff_table and eff_table != act_table:
                vrf_inst['table_mod'] = True

        if conf.exists(['description']):
            vrf_inst['description'] = conf.return_value(['description'])

        # find member interfaces of this particulat VRF
        vrf_inst['members'] = interfaces_with_vrf(name)

        # append individual VRF configuration to global configuration list
        vrf_config['vrf_add'].append(vrf_inst)

    return vrf_config


def verify(vrf_config):
    # ensure VRF is not assigned to any interface
    for vrf in vrf_config['vrf_add']:
        if vrf['table_mod']:
            raise ConfigError('VRF routing table id modification is not possible')

    # add test to see if routing table already exists or not?

    return None


def generate(vrf_config):
    return None

def apply(vrf_config):
    # https://github.com/torvalds/linux/blob/master/Documentation/networking/vrf.txt

    # set the default VRF global behaviour
    #sysctl('net.ipv4.tcp_l3mdev_accept', command['bind']['ipv4'])
    #sysctl('net.ipv4.udp_l3mdev_accept', command['bind']['ipv4'])

    for vrf_name in vrf_config['vrf_remove']:
        if os.path.isdir(f'/sys/class/net/{vrf_name}'):
            _cmd(f'ip link delete dev {vrf_name}')

    for vrf in vrf_config['vrf_add']:
        name = vrf['name']
        table = vrf['table']

        if not os.path.isdir(f'/sys/class/net/{name}'):
            _cmd(f'ip link add {name} type vrf table {table}')
            _cmd(f'ip link set dev {name} up')
            _cmd(f'ip -4 rule add oif {name} lookup {table}')
            _cmd(f'ip -4 rule add iif {name} lookup {table}')
            _cmd(f'ip -6 rule add oif {name} lookup {table}')
            _cmd(f'ip -6 rule add iif {name} lookup {table}')

        # set VRF description for e.g. SNMP monitoring
        with open(f'/sys/class/net/{name}/ifalias', 'w') as f:
            f.write(vrf['description'])

    return None

if __name__ == '__main__':
    try:
        c = get_config()
        verify(c)
        generate(c)
        apply(c)
    except ConfigError as e:
        print(e)
        exit(1)