# Copyright 2024 VyOS maintainers and contributors <maintainers@vyos.io>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
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# Lesser General Public License for more details.
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# T5993: Check if subnet is locally accessible and assign interface to subnet

from ipaddress import ip_network
from vyos.configtree import ConfigTree

base = ['service', 'dhcpv6-server', 'shared-network-name']

def migrate(config: ConfigTree) -> None:
    if not config.exists(base):
        # Nothing to do
        return

    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)