#!/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/>.

# Since connection tracking zones are int16, VRFs tables maximum value must
# be limited to 65535
# Also, interface names in nftables cannot start from numbers,
# so VRF name should not start from a number

from sys import argv
from sys import exit
from random import randrange
from random import choice
from string import ascii_lowercase
from vyos.configtree import ConfigTree
import re


# Helper function to find all config items with a VRF name
def _search_vrfs(config_commands, vrf_name):
    vrf_values = []
    # Regex to find path of config command with old VRF
    regex_filter = re.compile(rf'^set (?P<cmd_path>[^\']+vrf) \'{vrf_name}\'$')
    # Check each command for VRF value
    for config_command in config_commands:
        search_result = regex_filter.search(config_command)
        if search_result:
            # Append VRF command to a list
            vrf_values.append(search_result.group('cmd_path').split())
    if vrf_values:
        return vrf_values
    else:
        return None


# Helper function to find all config items with a table number
def _search_tables(config_commands, table_num):
    table_items = {'table_tags': [], 'table_values': []}
    # Regex to find values and nodes with a table number
    regex_tags = re.compile(rf'^set (?P<cmd_path>[^\']+table {table_num}) ?.*$')
    regex_values = re.compile(
        rf'^set (?P<cmd_path>[^\']+table) \'{table_num}\'$')
    for config_command in config_commands:
        # Search for tag nodes
        search_result = regex_tags.search(config_command)
        if search_result:
            # Append table node path to a tag nodes list
            cmd_path = search_result.group('cmd_path').split()
            if cmd_path not in table_items['table_tags']:
                table_items['table_tags'].append(cmd_path)
        # Search for value nodes
        search_result = regex_values.search(config_command)
        if search_result:
            # Append table node path to a value nodes list
            table_items['table_values'].append(
                search_result.group('cmd_path').split())
    return table_items


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 = ['vrf', 'name']
config = ConfigTree(config_file)

if not config.exists(base):
    # Nothing to do
    exit(0)

# Get a list of all currently used VRFs and tables
vrfs_current = {}
for vrf in config.list_nodes(base):
    vrfs_current[vrf] = int(config.return_value(base + [vrf, 'table']))

# Check VRF names and table numbers
name_regex = re.compile(r'^\d.*$')
for vrf_name, vrf_table in vrfs_current.items():
    # Check table number
    if vrf_table > 65535:
        # Find new unused table number
        vrfs_current[vrf_name] = None
        while not vrfs_current[vrf_name]:
            table_random = randrange(100, 65535)
            if table_random not in vrfs_current.values():
                vrfs_current[vrf_name] = table_random
        # Update number to a new one
        config.set(['vrf', 'name', vrf_name, 'table'],
                   vrfs_current[vrf_name],
                   replace=True)
        # Check config items with old table number and replace to new one
        config_commands = config.to_commands().split('\n')
        table_config_lines = _search_tables(config_commands, vrf_table)
        # Rename table nodes
        if table_config_lines.get('table_tags'):
            for table_config_path in table_config_lines.get('table_tags'):
                config.rename(table_config_path, f'{vrfs_current[vrf_name]}')
        # Replace table values
        if table_config_lines.get('table_values'):
            for table_config_path in table_config_lines.get('table_values'):
                config.set(table_config_path,
                           f'{vrfs_current[vrf_name]}',
                           replace=True)

    # Check VRF name
    if name_regex.match(vrf_name):
        vrf_name_new = None
        while not vrf_name_new:
            vrf_name_rand = f'{choice(ascii_lowercase)}{vrf_name}'[:15]
            if vrf_name_rand not in vrfs_current:
                vrf_name_new = vrf_name_rand
        # Update VRF name to a new one
        config.rename(['vrf', 'name', vrf_name], vrf_name_new)
        # Check config items with old VRF name and replace to new one
        config_commands = config.to_commands().split('\n')
        vrf_config_lines = _search_vrfs(config_commands, vrf_name)
        # Rename VRF to a new name
        if vrf_config_lines:
            for vrf_value_path in vrf_config_lines:
                config.set(vrf_value_path, vrf_name_new, replace=True)

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)