# Copyright 2023-2024 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/>.

# 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)

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

base = ['service', 'dhcpv6-server', 'shared-network-name']

def migrate(config: ConfigTree) -> None:
    if not config.exists(base):
        # Nothing to do
        return

    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'])