#!/usr/bin/env python3
#
# Copyright (C) 2018-2020 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 stat
import pwd

from copy import deepcopy
from glob import glob
from sys import exit

from vyos.config import Config
from vyos.validate import is_ipv4, is_addr_assigned
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/tftpd'

default_config_data = {
    'directory': '',
    'allow_upload': False,
    'port': '69',
    'listen': []
}

def get_config(config=None):
    tftpd = deepcopy(default_config_data)
    if config:
        conf = config
    else:
        conf = Config()
    base = ['service', 'tftp-server']
    if not conf.exists(base):
        return None
    else:
        conf.set_level(base)

    if conf.exists(['directory']):
        tftpd['directory'] = conf.return_value(['directory'])

    if conf.exists(['allow-upload']):
        tftpd['allow_upload'] = True

    if conf.exists(['port']):
        tftpd['port'] = conf.return_value(['port'])

    if conf.exists(['listen-address']):
        tftpd['listen'] = conf.return_values(['listen-address'])

    return tftpd

def verify(tftpd):
    # bail out early - looks like removal from running config
    if tftpd is None:
        return None

    # Configuring allowed clients without a server makes no sense
    if not tftpd['directory']:
        raise ConfigError('TFTP root directory must be configured!')

    if not tftpd['listen']:
        raise ConfigError('TFTP server listen address must be configured!')

    for addr in tftpd['listen']:
        if not is_addr_assigned(addr):
            print('WARNING: TFTP server listen address {0} not assigned to any interface!'.format(addr))

    return None

def generate(tftpd):
    # cleanup any available configuration file
    # files will be recreated on demand
    for i in glob(config_file + '*'):
        os.unlink(i)

    # bail out early - looks like removal from running config
    if tftpd is None:
        return None

    idx = 0
    for listen in tftpd['listen']:
        config = deepcopy(tftpd)
        if is_ipv4(listen):
            config['listen'] = [listen + ":" + tftpd['port'] + " -4"]
        else:
            config['listen'] = ["[" + listen + "]:" + tftpd['port'] + " -6"]

        file = config_file + str(idx)
        render(file, 'tftp-server/default.tmpl', config)

        idx = idx + 1

    return None

def apply(tftpd):
    # stop all services first - then we will decide
    call('systemctl stop tftpd@{0..20}.service')

    # bail out early - e.g. service deletion
    if tftpd is None:
        return None

    tftp_root = tftpd['directory']
    if not os.path.exists(tftp_root):
        os.makedirs(tftp_root)
        os.chmod(tftp_root, stat.S_IRUSR|stat.S_IWUSR|stat.S_IXUSR|stat.S_IRGRP|stat.S_IXGRP|stat.S_IROTH|stat.S_IXOTH)

    # get UNIX uid for user 'tftp'
    tftp_uid = pwd.getpwnam('tftp').pw_uid
    tftp_gid = pwd.getpwnam('tftp').pw_gid

    # get UNIX uid for tftproot directory
    dir_uid = os.stat(tftp_root).st_uid
    dir_gid = os.stat(tftp_root).st_gid

    # adjust uid/gid of tftproot directory if files don't belong to user tftp
    if (tftp_uid != dir_uid) or (tftp_gid != dir_gid):
        os.chown(tftp_root, tftp_uid, tftp_gid)

    idx = 0
    for listen in tftpd['listen']:
        call('systemctl restart tftpd@{0}.service'.format(idx))
        idx = idx + 1

    return None

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