#!/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.

from ipaddress import ip_interface
from sys import argv, exit
from vyos.ifconfig import Interface
from vyos.configtree import ConfigTree

if len(argv) < 2:
    print("Must specify file name!")
    exit(1)

file_name = 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 + ['listen-on']):
    # Nothing to do
    exit(0)

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)

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