#!/usr/bin/env python3
#
# Copyright (C) 2023 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/>.

# T3316: Migrate to Kea
# - Kea was meant to have support for key "prefix-highest" under PD which would allow an address range
#   However this seems to have never been implemented. A conversion to prefix length is needed (where possible).
#   Ref: https://lists.isc.org/pipermail/kea-users/2022-November/003686.html
# - Remove prefix temporary value, convert to multi leafNode (https://kea.readthedocs.io/en/kea-2.2.0/arm/dhcp6-srv.html#dhcpv6-server-limitations)

import sys
from vyos.configtree import ConfigTree
from vyos.utils.network import ipv6_prefix_length

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()

base = ['service', 'dhcpv6-server', 'shared-network-name']
config = ConfigTree(config_file)

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

for network in config.list_nodes(base):
    if not config.exists(base + [network, 'subnet']):
        continue

    for subnet in config.list_nodes(base + [network, 'subnet']):
        # Delete temporary value under address-range prefix, convert tagNode to leafNode multi
        if config.exists(base + [network, 'subnet', subnet, 'address-range', 'prefix']):
            prefix_base = base + [network, 'subnet', subnet, 'address-range', 'prefix']
            prefixes = config.list_nodes(prefix_base)
            
            config.delete(prefix_base)

            for prefix in prefixes:
                config.set(prefix_base, value=prefix, replace=False)

        if config.exists(base + [network, 'subnet', subnet, 'prefix-delegation', 'prefix']):
            prefix_base = base + [network, 'subnet', subnet, 'prefix-delegation', 'prefix']

            config.set(prefix_base)
            config.set_tag(prefix_base)

            for start in config.list_nodes(base + [network, 'subnet', subnet, 'prefix-delegation', 'start']):
                path = base + [network, 'subnet', subnet, 'prefix-delegation', 'start', start]

                delegated_length = config.return_value(path + ['prefix-length'])
                stop = config.return_value(path + ['stop'])

                prefix_length = ipv6_prefix_length(start, stop)

                # This range could not be converted into a simple prefix length and must be skipped
                if not prefix_length:
                    continue

                config.set(prefix_base + [start, 'delegated-length'], value=delegated_length)
                config.set(prefix_base + [start, 'prefix-length'], value=prefix_length)

            config.delete(base + [network, 'subnet', subnet, 'prefix-delegation', 'start'])

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))
    exit(1)