#!/usr/bin/env python3
#
# Copyright (C) 2021-2024 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/>.

import os

from sys import exit
from sys import argv

from vyos.config import Config
from vyos.config import config_dict_merge
from vyos.configdict import dict_merge
from vyos.configdict import node_changed
from vyos.configverify import verify_common_route_maps
from vyos.configverify import verify_route_map
from vyos.configverify import verify_interface_exists
from vyos.template import render_to_string
from vyos.ifconfig import Interface
from vyos.utils.dict import dict_search
from vyos.utils.network import get_interface_config
from vyos import ConfigError
from vyos import frr
from vyos import airbag
airbag.enable()

def get_config(config=None):
    if config:
        conf = config
    else:
        conf = Config()

    vrf = None
    if len(argv) > 1:
        vrf = argv[1]

    base_path = ['protocols', 'ospfv3']

    # eqivalent of the C foo ? 'a' : 'b' statement
    base = vrf and ['vrf', 'name', vrf, 'protocols', 'ospfv3'] or base_path
    ospfv3 = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)

    # Assign the name of our VRF context. This MUST be done before the return
    # statement below, else on deletion we will delete the default instance
    # instead of the VRF instance.
    if vrf: ospfv3['vrf'] = vrf

    # FRR has VRF support for different routing daemons. As interfaces belong
    # to VRFs - or the global VRF, we need to check for changed interfaces so
    # that they will be properly rendered for the FRR config. Also this eases
    # removal of interfaces from the running configuration.
    interfaces_removed = node_changed(conf, base + ['interface'])
    if interfaces_removed:
        ospfv3['interface_removed'] = list(interfaces_removed)

    # Bail out early if configuration tree does no longer exist. this must
    # be done after retrieving the list of interfaces to be removed.
    if not conf.exists(base):
        ospfv3.update({'deleted' : ''})
        return ospfv3

    # We have gathered the dict representation of the CLI, but there are default
    # options which we need to update into the dictionary retrived.
    default_values = conf.get_config_defaults(**ospfv3.kwargs,
                                              recursive=True)

    # We have to cleanup the default dict, as default values could enable features
    # which are not explicitly enabled on the CLI. Example: default-information
    # originate comes with a default metric-type of 2, which will enable the
    # entire default-information originate tree, even when not set via CLI so we
    # need to check this first and probably drop that key.
    if dict_search('default_information.originate', ospfv3) is None:
        del default_values['default_information']
    if 'graceful_restart' not in ospfv3:
        del default_values['graceful_restart']

    for protocol in ['babel', 'bgp', 'connected', 'kernel', 'ripng', 'static']:
        if dict_search(f'redistribute.{protocol}', ospfv3) is None:
            del default_values['redistribute'][protocol]
    if not bool(default_values['redistribute']):
        del default_values['redistribute']

    default_values.pop('interface', {})

    # merge in remaining default values
    ospfv3 = config_dict_merge(default_values, ospfv3)

    # We also need some additional information from the config, prefix-lists
    # and route-maps for instance. They will be used in verify().
    #
    # XXX: one MUST always call this without the key_mangling() option! See
    # vyos.configverify.verify_common_route_maps() for more information.
    tmp = conf.get_config_dict(['policy'])
    # Merge policy dict into "regular" config dict
    ospfv3 = dict_merge(tmp, ospfv3)

    return ospfv3

def verify(ospfv3):
    if not ospfv3:
        return None

    verify_common_route_maps(ospfv3)

    # As we can have a default-information route-map, we need to validate it!
    route_map_name = dict_search('default_information.originate.route_map', ospfv3)
    if route_map_name: verify_route_map(route_map_name, ospfv3)

    if 'area' in ospfv3:
        for area, area_config in ospfv3['area'].items():
            if 'area_type' in area_config:
                if len(area_config['area_type']) > 1:
                    raise ConfigError(f'Can only configure one area-type for OSPFv3 area "{area}"!')
            if 'range' in area_config:
                for range, range_config in area_config['range'].items():
                    if {'not_advertise', 'advertise'} <= range_config.keys():
                        raise ConfigError(f'"not-advertise" and "advertise" for "range {range}" cannot be both configured at the same time!')

    if 'interface' in ospfv3:
        for interface, interface_config in ospfv3['interface'].items():
            verify_interface_exists(interface)
            if 'ifmtu' in interface_config:
                mtu = Interface(interface).get_mtu()
                if int(interface_config['ifmtu']) > int(mtu):
                    raise ConfigError(f'OSPFv3 ifmtu can not exceed physical MTU of "{mtu}"')

            # If interface specific options are set, we must ensure that the
            # interface is bound to our requesting VRF. Due to the VyOS
            # priorities the interface is bound to the VRF after creation of
            # the VRF itself, and before any routing protocol is configured.
            if 'vrf' in ospfv3:
                vrf = ospfv3['vrf']
                tmp = get_interface_config(interface)
                if 'master' not in tmp or tmp['master'] != vrf:
                    raise ConfigError(f'Interface "{interface}" is not a member of VRF "{vrf}"!')

    return None

def generate(ospfv3):
    if not ospfv3 or 'deleted' in ospfv3:
        return None

    ospfv3['new_frr_config'] = render_to_string('frr/ospf6d.frr.j2', ospfv3)
    return None

def apply(ospfv3):
    ospf6_daemon = 'ospf6d'

    # Save original configuration prior to starting any commit actions
    frr_cfg = frr.FRRConfig()

    # Generate empty helper string which can be ammended to FRR commands, it
    # will be either empty (default VRF) or contain the "vrf <name" statement
    vrf = ''
    if 'vrf' in ospfv3:
        vrf = ' vrf ' + ospfv3['vrf']

    frr_cfg.load_configuration(ospf6_daemon)
    frr_cfg.modify_section(f'^router ospf6{vrf}', stop_pattern='^exit', remove_stop_mark=True)

    for key in ['interface', 'interface_removed']:
        if key not in ospfv3:
            continue
        for interface in ospfv3[key]:
            frr_cfg.modify_section(f'^interface {interface}', stop_pattern='^exit', remove_stop_mark=True)

    if 'new_frr_config' in ospfv3:
        frr_cfg.add_before(frr.default_add_before, ospfv3['new_frr_config'])

    frr_cfg.commit_configuration(ospf6_daemon)

    return None

if __name__ == '__main__':
    try:
        c = get_config()
        verify(c)
        generate(c)
        apply(c)
    except ConfigError as e:
        print(e)
        exit(1)