#!/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 jinja2 import FileSystemLoader, Environment
from sys import exit

from vyos.config import Config
from vyos.defaults import directories as vyos_data_dir
from vyos.validate import is_ipv4, is_addr_assigned
from vyos import ConfigError

config_file = r'/etc/default/tftpd'

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

def get_config():
    tftpd = deepcopy(default_config_data)
    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

    # Prepare Jinja2 template loader from files
    tmpl_path = os.path.join(vyos_data_dir['data'], 'templates', 'tftp-server')
    fs_loader = FileSystemLoader(tmpl_path)
    env = Environment(loader=fs_loader)

    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"]

        tmpl = env.get_template('default.tmpl')
        config_text = tmpl.render(config)
        file = config_file + str(idx)
        with open(file, 'w') as f:
            f.write(config_text)

        idx = idx + 1

    return None

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

    # 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']:
        os.system('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)