# Copyright 2021-2024 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/>.

# T3741: no-ipv4-unicast is now enabled by default
# T5937: Migrate IPv6 BGP Neighbor Peer Groups

from vyos.configtree import ConfigTree

base = ['protocols', 'bgp']

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

    # 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'])
    else:
        # 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)

    # Migrate IPv6 AFI peer-group
    if config.exists(base + ['neighbor']):
        for neighbor in config.list_nodes(base + ['neighbor']):
            tmp_path = base + ['neighbor', neighbor, 'address-family', 'ipv6-unicast', 'peer-group']
            if config.exists(tmp_path):
                peer_group = config.return_value(tmp_path)
                config.set(base + ['neighbor', neighbor, 'peer-group'], value=peer_group)
                config.delete(tmp_path)