#!/usr/bin/env python3
#
# Copyright (C) 2017-2020 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
import fnmatch

from sys import exit
from copy import deepcopy

from vyos.config import Config
from vyos import ConfigError
from vyos.util import call
from vyos.template import render

from vyos import airbag
airbag.enable()

config_file = r'/etc/default/udp-broadcast-relay'

default_config_data = {
    'disabled': False,
    'instances': []
}

def get_config():
    relay = deepcopy(default_config_data)
    conf = Config()
    base = ['service', 'broadcast-relay']

    if not conf.exists(base):
        return None
    else:
        conf.set_level(base)

    # Service can be disabled by user
    if conf.exists('disable'):
        relay['disabled'] = True
        return relay

    # Parse configuration of each individual instance
    if conf.exists('id'):
        for id in conf.list_nodes('id'):
            conf.set_level(base + ['id', id])
            config = {
                'id': id,
                'disabled': False,
                'address': '',
                'description': '',
                'interfaces': [],
                'port': ''
            }

            # Check if individual broadcast relay service is disabled
            if conf.exists(['disable']):
                config['disabled'] = True

            # Source IP of forwarded packets, if empty original senders address is used
            if conf.exists(['address']):
                config['address'] = conf.return_value(['address'])

            # A description for each individual broadcast relay service
            if conf.exists(['description']):
                config['description'] = conf.return_value(['description'])

            # UDP port to listen on for broadcast frames
            if conf.exists(['port']):
                config['port'] = conf.return_value(['port'])

            # Network interfaces to listen on for broadcast frames to be relayed
            if conf.exists(['interface']):
                config['interfaces'] = conf.return_values(['interface'])

            relay['instances'].append(config)

    return relay

def verify(relay):
    if relay is None:
        return None

    if relay['disabled']:
        return None

    for r in relay['instances']:
        # we don't have to check this instance when it's disabled
        if r['disabled']:
            continue

        # we certainly require a UDP port to listen to
        if not r['port']:
            raise ConfigError('UDP broadcast relay "{0}" requires a port number'.format(r['id']))

        # Relaying data without two interface is kinda senseless ...
        if len(r['interfaces']) < 2:
            raise ConfigError('UDP broadcast relay "id {0}" requires at least 2 interfaces'.format(r['id']))

    return None


def generate(relay):
    if relay is None:
        return None

    config_dir = os.path.dirname(config_file)
    config_filename = os.path.basename(config_file)
    active_configs = []

    for config in fnmatch.filter(os.listdir(config_dir), config_filename + '*'):
        # determine prefix length to identify service instance
        prefix_len = len(config_filename)
        active_configs.append(config[prefix_len:])

    # sort our list
    active_configs.sort()

    # delete old configuration files
    for id in active_configs[:]:
        if os.path.exists(config_file + id):
            os.unlink(config_file + id)

    # If the service is disabled, we can bail out here
    if relay['disabled']:
        print('Warning: UDP broadcast relay service will be deactivated because it is disabled')
        return None

    for r in relay['instances']:
        # Skip writing instance config when it's disabled
        if r['disabled']:
            continue

        # configuration filename contains instance id
        file = config_file + str(r['id'])
        render(file, 'bcast-relay/udp-broadcast-relay.tmpl', r)

    return None

def apply(relay):
    # first stop all running services
    call('systemctl stop udp-broadcast-relay@{1..99}.service')

    if (relay is None) or relay['disabled']:
        return None

    # start only required service instances
    for r in relay['instances']:
        # Don't start individual instance when it's disabled
        if r['disabled']:
            continue
        call('systemctl start udp-broadcast-relay@{0}.service'.format(r['id']))

    return None

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