# Copyright 2019-2024 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/>.

# Between 1.2.3 and 1.2.4, FRR added per-neighbor enforce-first-as option.
# Unfortunately they also removed the global enforce-first-as option,
# which broke all old configs that used to have it.
#
# To emulate the effect of the original option, we insert it in every neighbor
# if the config used to have the original global option

from vyos.configtree import ConfigTree


def migrate(config: ConfigTree) -> None:
    if not config.exists(['protocols', 'bgp']):
        # Nothing to do
        return

    # Check if BGP is actually configured and obtain the ASN
    asn_list = config.list_nodes(['protocols', 'bgp'])
    if asn_list:
        # There's always just one BGP node, if any
        asn = asn_list[0]
    else:
        # There's actually no BGP, just its empty shell
        return

    # Check if BGP enforce-first-as option is set
    enforce_first_as_path = ['protocols', 'bgp', asn, 'parameters', 'enforce-first-as']
    if config.exists(enforce_first_as_path):
        # Delete the obsolete option
        config.delete(enforce_first_as_path)

        # Now insert it in every peer
        peers = config.list_nodes(['protocols', 'bgp', asn, 'neighbor'])
        for p in peers:
            config.set(['protocols', 'bgp', asn, 'neighbor', p, 'enforce-first-as'])
    else:
        # Do nothing
        return