#!/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/>.

# - T3037, BGP address-family ipv6-unicast capability dynamic does not exist in
#   FRR, there is only a base, per neighbor dynamic capability, migrate config

from sys import argv
from sys import exit
from vyos.configtree import ConfigTree
from vyos.template import is_ipv4
from vyos.template import is_ipv6

if len(argv) < 2:
    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)

# Check if BGP is actually configured and obtain the ASN
asn_list = config.list_nodes(base)
if asn_list:
    # There's always just one BGP node, if any
    bgp_base = base + [asn_list[0]]

    for neighbor_type in ['neighbor', 'peer-group']:
        if not config.exists(bgp_base + [neighbor_type]):
            continue
        for neighbor in config.list_nodes(bgp_base + [neighbor_type]):
            # T2844 - add IPv4 AFI disable-send-community support
            send_comm_path = bgp_base + [neighbor_type, neighbor, 'disable-send-community']
            if config.exists(send_comm_path):
                new_base = bgp_base + [neighbor_type, neighbor, 'address-family', 'ipv4-unicast']
                config.set(new_base)
                config.copy(send_comm_path, new_base + ['disable-send-community'])
                config.delete(send_comm_path)

            cap_dynamic = False
            peer_group = None
            for afi in ['ipv4-unicast', 'ipv6-unicast']:
                afi_path = bgp_base + [neighbor_type, neighbor, 'address-family', afi]
                # Exit loop early if AFI does not exist
                if not config.exists(afi_path):
                    continue

                cap_path = afi_path + ['capability', 'dynamic']
                if config.exists(cap_path):
                    cap_dynamic = True
                    config.delete(cap_path)

                    # We have now successfully migrated the address-family
                    # specific dynamic capability to the neighbor/peer-group
                    # level. If this has been the only option under the
                    # address-family nodes, we can clean them up by checking if
                    # no other nodes are left under that tree and if so, delete
                    # the parent.
                    #
                    # We walk from the most inner node to the most outer one.
                    cleanup = -1
                    while len(config.list_nodes(cap_path[:cleanup])) == 0:
                        config.delete(cap_path[:cleanup])
                        cleanup -= 1

                peer_group_path = afi_path + ['peer-group']
                if config.exists(peer_group_path):
                    if ((is_ipv4(neighbor) and afi == 'ipv4-unicast') or
                        (is_ipv6(neighbor) and afi == 'ipv6-unicast')):
                        peer_group = config.return_value(peer_group_path)

                    config.delete(peer_group_path)

                    # We have now successfully migrated the address-family
                    # specific peer-group to the neighbor level. If this has
                    # been the only option under the address-family nodes, we
                    # can clean them up by checking if no other nodes are left
                    # under that tree and if so, delete the parent.
                    #
                    # We walk from the most inner node to the most outer one.
                    cleanup = -1
                    while len(config.list_nodes(peer_group_path[:cleanup])) == 0:
                        config.delete(peer_group_path[:cleanup])
                        cleanup -= 1

            if cap_dynamic:
                config.set(bgp_base + [neighbor_type, neighbor, 'capability', 'dynamic'])
            if peer_group:
                config.set(bgp_base + [neighbor_type, neighbor, 'peer-group'], value=peer_group)

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)