#!/usr/bin/env python3
#
# Copyright (C) 2021-2022 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
import uuid
import netifaces
from ipaddress import IPv4Network
from ipaddress import IPv6Network

from vyos.config import Config
from vyos.utils.process import call
from vyos.template import render
from vyos.template import is_ipv4
from vyos.template import is_ipv6
from vyos import ConfigError
from vyos import airbag
airbag.enable()

config_file = r'/run/upnp/miniupnp.conf'

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

    base = ['service', 'upnp']
    upnpd = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)

    if not upnpd:
        return None

    upnpd = conf.merge_defaults(upnpd, recursive=True)

    uuidgen = uuid.uuid1()
    upnpd.update({'uuid': uuidgen})

    return upnpd

def get_all_interface_addr(prefix, filter_dev, filter_family):
    list_addr = []
    interfaces = netifaces.interfaces()

    for interface in interfaces:
        if filter_dev and interface in filter_dev:
            continue
        addrs = netifaces.ifaddresses(interface)
        if netifaces.AF_INET in addrs.keys():
            if netifaces.AF_INET in filter_family:
                for addr in addrs[netifaces.AF_INET]:
                    if prefix:
                        # we need to manually assemble a list of IPv4 address/prefix
                        prefix = '/' + \
                            str(IPv4Network('0.0.0.0/' + addr['netmask']).prefixlen)
                        list_addr.append(addr['addr'] + prefix)
                    else:
                        list_addr.append(addr['addr'])
        if netifaces.AF_INET6 in addrs.keys():
            if netifaces.AF_INET6 in filter_family:
                for addr in addrs[netifaces.AF_INET6]:
                    if prefix:
                        # we need to manually assemble a list of IPv4 address/prefix
                        bits = bin(int(addr['netmask'].replace(':', '').split('/')[0], 16)).count('1')
                        prefix = '/' + str(bits)
                        list_addr.append(addr['addr'] + prefix)
                    else:
                        list_addr.append(addr['addr'])

    return list_addr

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

    if 'wan_interface' not in upnpd:
        raise ConfigError('To enable UPNP, you must have the "wan-interface" option!')

    if 'rule' in upnpd:
        for rule, rule_config in upnpd['rule'].items():
            for option in ['external_port_range', 'internal_port_range', 'ip', 'action']:
                if option not in rule_config:
                    tmp = option.replace('_', '-')
                    raise ConfigError(f'Every UPNP rule requires "{tmp}" to be set!')

    if 'stun' in upnpd:
        for option in ['host', 'port']:
            if option not in upnpd['stun']:
                raise ConfigError(f'A UPNP stun support must have an "{option}" option!')

    # Check the validity of the IP address
    listen_dev = []
    system_addrs_cidr = get_all_interface_addr(True, [], [netifaces.AF_INET, netifaces.AF_INET6])
    system_addrs = get_all_interface_addr(False, [], [netifaces.AF_INET, netifaces.AF_INET6])
    if 'listen' not in upnpd:
        raise ConfigError(f'Listen address or interface is required!')
    for listen_if_or_addr in upnpd['listen']:
        if listen_if_or_addr not in netifaces.interfaces():
            listen_dev.append(listen_if_or_addr)
        if (listen_if_or_addr not in system_addrs) and (listen_if_or_addr not in system_addrs_cidr) and \
                (listen_if_or_addr not in netifaces.interfaces()):
            if is_ipv4(listen_if_or_addr) and IPv4Network(listen_if_or_addr).is_multicast:
                raise ConfigError(f'The address "{listen_if_or_addr}" is an address that is not allowed'
                                  f'to listen on. It is not an interface address nor a multicast address!')
            if is_ipv6(listen_if_or_addr) and IPv6Network(listen_if_or_addr).is_multicast:
                raise ConfigError(f'The address "{listen_if_or_addr}" is an address that is not allowed'
                                  f'to listen on. It is not an interface address nor a multicast address!')

    system_listening_dev_addrs_cidr = get_all_interface_addr(True, listen_dev, [netifaces.AF_INET6])
    system_listening_dev_addrs = get_all_interface_addr(False, listen_dev, [netifaces.AF_INET6])
    for listen_if_or_addr in upnpd['listen']:
        if listen_if_or_addr not in netifaces.interfaces() and \
                (listen_if_or_addr not in system_listening_dev_addrs_cidr) and \
                (listen_if_or_addr not in system_listening_dev_addrs) and \
                is_ipv6(listen_if_or_addr) and \
                (not IPv6Network(listen_if_or_addr).is_multicast):
            raise ConfigError(f'{listen_if_or_addr} must listen on the interface of the network card')

def generate(upnpd):
    if not upnpd:
        return None

    if os.path.isfile(config_file):
        os.unlink(config_file)

    render(config_file, 'firewall/upnpd.conf.j2', upnpd)

def apply(upnpd):
    systemd_service_name = 'miniupnpd.service'
    if not upnpd:
        # Stop the UPNP service
        call(f'systemctl stop {systemd_service_name}')
    else:
        # Start the UPNP service
        call(f'systemctl restart {systemd_service_name}')

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