#!/usr/bin/env python3
#
# Copyright (C) 2021 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/>.

# T3741: no-ipv4-unicast is now enabled by default

from sys import argv
from sys import exit

from vyos.configtree import ConfigTree
from vyos.template import is_ipv4

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

file_name = argv[1]

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

base = ['protocols', 'bgp']
config = ConfigTree(config_file)

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

# This is now a default option - simply delete it.
# As it was configured explicitly - we can also bail out early as we need to
# do nothing!
if config.exists(base + ['parameters', 'default', 'no-ipv4-unicast']):
    config.delete(base + ['parameters', 'default', 'no-ipv4-unicast'])

    # Check if the "default" node is now empty, if so - remove it
    if len(config.list_nodes(base + ['parameters', 'default'])) == 0:
        config.delete(base + ['parameters', 'default'])

    # Check if the "default" node is now empty, if so - remove it
    if len(config.list_nodes(base + ['parameters'])) == 0:
        config.delete(base + ['parameters'])

    exit(0)

# As we now install a new default option into BGP we need to migrate all
# existing BGP neighbors and restore the old behavior
if config.exists(base + ['neighbor']):
    for neighbor in config.list_nodes(base + ['neighbor']):
        peer_group = base + ['neighbor', neighbor, 'peer-group']
        if config.exists(peer_group):
            peer_group_name = config.return_value(peer_group)
            # peer group enables old behavior for neighbor - bail out
            if config.exists(base + ['peer-group', peer_group_name, 'address-family', 'ipv4-unicast']):
                continue

        afi_ipv4 = base + ['neighbor', neighbor, 'address-family', 'ipv4-unicast']
        if not config.exists(afi_ipv4):
            config.set(afi_ipv4)

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)