#!/usr/bin/env python3
#
# Copyright (C) 2019 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/>.
#

# 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.

import sys

from ipaddress import ip_interface
from vyos.ifconfig import Interface
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()

config = ConfigTree(config_file)

base = ['service', 'dns', 'forwarding']
if not config.exists(base):
    # Nothing to do
    sys.exit(0)

else:
    # XXX: we can remove the else and un-indent this whole block

    if config.exists(base + ['listen-on']):
        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 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]

            section = Interface.section(intf)
            if not section:
                raise ValueError(f'Invalid interface name {intf}')
            path = ['interfaces', section, intf, 'address']

            # retrieve corresponding interface addresses in CIDR format
            # those need to be converted in pure IP addresses without network information
            for addr in config.return_values(path):
                listen_addr.append( ip_interface(addr).ip )

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

    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))
        sys.exit(1)