#!/usr/bin/env python3
#
# Copyright (C) 2018-2020 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 vyos.config import Config
from vyos.configdict import dict_merge
from vyos.configdict import get_interface_dict
from vyos.configdict import node_changed
from vyos.configdict import leaf_node_changed
from vyos.configverify import verify_vrf
from vyos.configverify import verify_address
from vyos.configverify import verify_bridge_delete
from vyos.configverify import verify_mtu_ipv6
from vyos.ifconfig import WireGuardIf
from vyos.util import check_kmod
from vyos.util import check_port_availability
from vyos import ConfigError
from vyos import airbag
airbag.enable()

def get_config(config=None):
    """
    Retrive CLI config as dictionary. Dictionary can never be empty, as at least the
    interface name will be added or a deleted flag
    """
    if config:
        conf = config
    else:
        conf = Config()
    base = ['interfaces', 'wireguard']
    wireguard = get_interface_dict(conf, base)

    # Determine which Wireguard peer has been removed.
    # Peers can only be removed with their public key!
    dict = {}
    tmp = node_changed(conf, ['peer'], key_mangling=('-', '_'))
    for peer in (tmp or []):
        public_key = leaf_node_changed(conf, ['peer', peer, 'public_key'])
        if public_key:
            dict = dict_merge({'peer_remove' : {peer : {'public_key' : public_key[0]}}}, dict)
            wireguard.update(dict)

    return wireguard

def verify(wireguard):
    if 'deleted' in wireguard:
        verify_bridge_delete(wireguard)
        return None

    verify_mtu_ipv6(wireguard)
    verify_address(wireguard)
    verify_vrf(wireguard)

    if 'private_key' not in wireguard:
        raise ConfigError('Wireguard private-key not defined')

    if 'peer' not in wireguard:
        raise ConfigError('At least one Wireguard peer is required!')

    if 'port' in wireguard:
        listen_port = int(wireguard['port'])
        if check_port_availability('0.0.0.0', listen_port, 'udp') is not True:
            raise ConfigError(
                f'The UDP port {listen_port} is busy or unavailable and cannot be used for the interface'
            )

    # run checks on individual configured WireGuard peer
    for tmp in wireguard['peer']:
        peer = wireguard['peer'][tmp]

        if 'allowed_ips' not in peer:
            raise ConfigError(f'Wireguard allowed-ips required for peer "{tmp}"!')

        if 'public_key' not in peer:
            raise ConfigError(f'Wireguard public-key required for peer "{tmp}"!')

        if ('address' in peer and 'port' not in peer) or ('port' in peer and 'address' not in peer):
            raise ConfigError('Both Wireguard port and address must be defined '
                              f'for peer "{tmp}" if either one of them is set!')

def apply(wireguard):
    tmp = WireGuardIf(wireguard['ifname'])
    if 'deleted' in wireguard:
        tmp.remove()
        return None

    tmp.update(wireguard)
    return None

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