#!/usr/bin/env python3
#
# Copyright (C) 2024 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/>.

# T5993: Check if subnet is locally accessible and assign interface to subnet

import sys
from ipaddress import ip_network
from vyos.configtree import ConfigTree

if (len(sys.argv) < 1):
    print("Must specify file name!")
    sys.exit(1)

file_name = sys.argv[1]

with open(file_name, 'r') as f:
    config_file = f.read()

base = ['service', 'dhcpv6-server', 'shared-network-name']
config = ConfigTree(config_file)

if not config.exists(base):
    # Nothing to do
    exit(0)

def find_subnet_interface(subnet):
    subnet_net = ip_network(subnet)

    def check_addr(if_path):
        if config.exists(if_path + ['address']):
            for addr in config.return_values(if_path + ['address']):
                try:
                    if ip_network(addr, strict=False) == subnet_net:
                        return True
                except:
                    pass # interface address was probably "dhcp" or other magic string
        return None

    for iftype in config.list_nodes(['interfaces']):
        for ifname in config.list_nodes(['interfaces', iftype]):
            if_base = ['interfaces', iftype, ifname]

            if check_addr(if_base):
                return ifname

            if config.exists(if_base + ['vif']):
                for vif in config.list_nodes(if_base + ['vif']):
                    if check_addr(if_base + ['vif', vif]):
                        return f'{ifname}.{vif}'

            if config.exists(if_base + ['vif-s']):
                for vifs in config.list_nodes(if_base + ['vif-s']):
                    if check_addr(if_base + ['vif-s', vifs]):
                        return f'{ifname}.{vifs}'

                    if config.exists(if_base + ['vif-s', vifs, 'vif-c']):
                        for vifc in config.list_nodes(if_base + ['vif-s', vifs, 'vif-c']):
                            if check_addr(if_base + ['vif-s', vifs, 'vif-c', vifc]):
                                return f'{ifname}.{vifs}.{vifc}'

    return False

for network in config.list_nodes(base):
    if not config.exists(base + [network, 'subnet']):
        continue

    for subnet in config.list_nodes(base + [network, 'subnet']):
        subnet_interface = find_subnet_interface(subnet)

        if subnet_interface:
            config.set(base + [network, 'subnet', subnet, 'interface'], value=subnet_interface)

try:
    with open(file_name, 'w') as f:
        f.write(config.to_string())
except OSError as e:
    print("Failed to save the modified config: {}".format(e))
    exit(1)