# Copyright 2019-2024 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.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this library.  If not, see <http://www.gnu.org/licenses/>.

# This migration script will remove the deprecated 'listen-on' statement
# from the dns forwarding service and will add the corresponding
# listen-address nodes instead. This is required as PowerDNS can only listen
# on interface addresses and not on interface names.

from ipaddress import ip_interface
from vyos.ifconfig import Interface
from vyos.configtree import ConfigTree

base = ['service', 'dns', 'forwarding']

def migrate(config: ConfigTree) -> None:
    if not config.exists(base + ['listen-on']):
        # Nothing to do
        return

    listen_intf = config.return_values(base + ['listen-on'])
    # Delete node with abandoned command
    config.delete(base + ['listen-on'])

    # retrieve interface addresses for every configured listen-on interface
    listen_addr = []
    for intf in listen_intf:
        # we need to evaluate the interface section before manipulating the 'intf' variable
        section = Interface.section(intf)
        if not section:
            raise ValueError(f'Invalid interface name {intf}')

        # we need to treat vif and vif-s interfaces differently,
        # both "real interfaces" use dots for vlan identifiers - those
        # need to be exchanged with vif and vif-s identifiers
        if intf.count('.') == 1:
            # this is a regular VLAN interface
            intf = intf.split('.')[0] + ' vif ' + intf.split('.')[1]
        elif intf.count('.') == 2:
            # this is a QinQ VLAN interface
            intf = intf.split('.')[0] + ' vif-s ' + intf.split('.')[1] + ' vif-c ' +  intf.split('.')[2]

        # retrieve corresponding interface addresses in CIDR format
        # those need to be converted in pure IP addresses without network information
        path = ['interfaces', section, intf, 'address']
        try:
            for addr in config.return_values(path):
                listen_addr.append( ip_interface(addr).ip )
        except:
            # Some interface types do not use "address" option (e.g. OpenVPN)
            # and may not even have a fixed address
            print("Could not retrieve the address of the interface {} from the config".format(intf))
            print("You will need to update your DNS forwarding configuration manually")

    for addr in listen_addr:
        config.set(base + ['listen-address'], value=addr, replace=False)