#!/usr/bin/python3
# -*- mode: python -*-
#
# This file is part of Plinth.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

"""
Configuration helper for BIND server.
"""

import argparse

from plinth import action_utils


CONFIG_FILE = '/etc/bind/named.conf.options'

DEFAULT_CONFIG = '''
acl goodclients {
    localnets;
};
options {
directory "/var/cache/bind";

recursion yes;
allow-query { goodclients; };

forwarders {
8.8.8.8; 8.8.4.4;
};
forward first;

dnssec-enable yes;
dnssec-validation auto;

auth-nxdomain no;    # conform to RFC1035
listen-on-v6 { any; };
};
'''


def parse_arguments():
    """Return parsed command line arguments as dictionary"""
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')
    subparsers.add_parser('setup', help='Setup for BIND')

    configure = subparsers.add_parser('configure', help='Configure BIND')
    configure.add_argument('--set-forwarding', choices=['true', 'false'],
                           help='Set forwarding true/false')
    configure.add_argument('--enable-dnssec', choices=['true', 'false'],
                           help='Set DNSSEC true/false')

    dns = subparsers.add_parser('dns', help='Set DNS forwarders')
    dns.add_argument('--set', help='List of IP addresses, separated by space')

    subparsers.required = True
    return parser.parse_args()


def subcommand_setup(_):
    """Setup BIND configuration."""
    conf_file = open(CONFIG_FILE, "w")
    conf_file.write(DEFAULT_CONFIG)
    conf_file.close()
    action_utils.service_restart('bind9')


def subcommand_dns(arguments):
    """Setting DNS servers"""
    if arguments.set:
        set_forwarders(arguments.set)

    action_utils.service_restart('bind9')


def subcommand_configure(arguments):
    """Configure BIND."""
    if arguments.set_forwarding:
        set_forwarding(arguments.set_forwarding)

    if arguments.enable_dnssec:
        enable_dnssec(arguments.enable_dnssec)

    action_utils.service_restart('bind9')


def set_forwarding(choice):
    """Enable or disable DNS forwarding."""
    data = [line.strip() for line in open(CONFIG_FILE, 'r')]
    flag = 0
    if choice == "false":
        if 'forwarders {' in data and not '// forwarders {' in data:
            conf_file = open(CONFIG_FILE, 'w')
            for line in data:
                if 'forwarders {' in line and not '// forwarders {' in line:
                    flag = 1
                if flag == 1:
                    line = '	// ' + line
                if 'forward first' in line:
                    flag = 0
                if "0.0.0.0" not in line:
                    conf_file.write(line + '\n')
            conf_file.close()

    else:
        if '// forwarders {' in data:
            conf_file = open(CONFIG_FILE, 'w')
            for line in data:
                if '// forwarders {' in line:
                    flag = 1
                if flag == 1:
                    line = line[2:]
                if 'forward first' in line:
                    flag = 0
                if "0.0.0.0" not in line:
                    conf_file.write(line + '\n')
            conf_file.close()


def enable_dnssec(choice):
    """Enable or disable DNSSEC."""
    data = [line.strip() for line in open(CONFIG_FILE, 'r')]
    if choice == "false":
        if '//dnssec-enable yes;' not in data:
            conf_file = open(CONFIG_FILE, 'w')
            for line in data:
                if 'dnssec-enable yes;' in line:
                    line = '//' + line
                conf_file.write(line+'\n')
            conf_file.close()

    else:
        if '//dnssec-enable yes;' in data:
            conf_file = open(CONFIG_FILE, 'w')
            for line in data:
                if '//dnssec-enable yes;' in line:
                    line = line[2:]
                conf_file.write(line + '\n')
            conf_file.close()


def set_forwarders(forwarders):
    """Set DNS forwarders."""
    flag = 0
    data = [line.strip() for line in open(CONFIG_FILE, 'r')]
    conf_file = open(CONFIG_FILE, 'w')
    for line in data:
        if 'forwarders {' in line:
            conf_file.write(line + '\n')
            for dns in forwarders.split():
                conf_file.write(dns + '; ')
            conf_file.write('\n')
            flag = 1
        elif '};' in line and flag == 1:
            conf_file.write(line + '\n')
            flag = 0
        elif flag == 0:
            conf_file.write(line + '\n')
    conf_file.close()


def main():
    """Parse arguments and perform all duties"""
    arguments = parse_arguments()

    subcommand = arguments.subcommand.replace('-', '_')
    subcommand_method = globals()['subcommand_' + subcommand]
    subcommand_method(arguments)


if __name__ == '__main__':
    main()