#!/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 argparse
import os
import sys
import shutil
import syslog as sl
import re

from vyos.ifconfig import WireGuardIf

from vyos import ConfigError
from vyos.config import Config
from vyos.util import cmd, run

dir = r'/config/auth/wireguard'
psk = dir + '/preshared.key'

def check_kmod():
    """ check if kmod is loaded, if not load it """
    if not os.path.exists('/sys/module/wireguard'):
        sl.syslog(sl.LOG_NOTICE, "loading wirguard kmod")
        if run('sudo modprobe wireguard') != 0:
            sl.syslog(sl.LOG_ERR, "modprobe wireguard failed")
            raise ConfigError("modprobe wireguard failed")

def generate_keypair(pk, pub):
    """ generates a keypair which is stored in /config/auth/wireguard """
    old_umask = os.umask(0o027)
    if run(f'wg genkey | tee {pk} | wg pubkey > {pub}') != 0:
        raise ConfigError("wireguard key-pair generation failed")
    else:
        sl.syslog(
            sl.LOG_NOTICE, "new keypair wireguard key generated in " + dir)
    os.umask(old_umask)


def genkey(location):
    """ helper function to check, regenerate the keypair """
    pk = "{}/private.key".format(location)
    pub = "{}/public.key".format(location)
    old_umask = os.umask(0o027)
    if os.path.exists(pk) and os.path.exists(pub):
        try:
            choice = input(
                "You already have a wireguard key-pair, do you want to re-generate? [y/n] ")
            if choice == 'y' or choice == 'Y':
                generate_keypair(pk, pub)
        except KeyboardInterrupt:
            sys.exit(0)
    else:
        """ if keypair is bing executed from a running iso """
        if not os.path.exists(location):
            run(f'sudo mkdir -p {location}')
            run(f'sudo chgrp vyattacfg {location}')
            run(f'sudo chmod 750 {location}')
        generate_keypair(pk, pub)
    os.umask(old_umask)


def showkey(key):
    """ helper function to show privkey or pubkey """
    if os.path.exists(key):
        print (open(key).read().strip())
    else:
        print ("{} not found".format(key))


def genpsk():
    """
        generates a preshared key and shows it on stdout,
        it's stored only in the cli config
    """

    psk = cmd('wg genpsk')
    print(psk)

def list_key_dirs():
    """ lists all dirs under /config/auth/wireguard """
    if os.path.exists(dir):
        nks = next(os.walk(dir))[1]
        for nk in nks:
            print (nk)

def del_key_dir(kname):
    """ deletes /config/auth/wireguard/<kname> """
    kdir = "{0}/{1}".format(dir,kname)
    if not os.path.isdir(kdir):
        print ("named keypair {} not found".format(kname))
        return 1
    shutil.rmtree(kdir)


if __name__ == '__main__':
    check_kmod()
    parser = argparse.ArgumentParser(description='wireguard key management')
    parser.add_argument(
        '--genkey', action="store_true", help='generate key-pair')
    parser.add_argument(
        '--showpub', action="store_true", help='shows public key')
    parser.add_argument(
        '--showpriv', action="store_true", help='shows private key')
    parser.add_argument(
        '--genpsk', action="store_true", help='generates preshared-key')
    parser.add_argument(
        '--location', action="store", help='key location within {}'.format(dir))
    parser.add_argument(
        '--listkdir', action="store_true", help='lists named keydirectories')
    parser.add_argument(
        '--delkdir', action="store_true", help='removes named keydirectories')
    parser.add_argument(
        '--showinterface', action="store", help='shows interface details')
    args = parser.parse_args()

    try:
        if args.genkey:
            if args.location:
                genkey("{0}/{1}".format(dir, args.location))
            else:
                genkey("{}/default".format(dir))
        if args.showpub:
            if args.location:
                showkey("{0}/{1}/public.key".format(dir, args.location))
            else:
                showkey("{}/default/public.key".format(dir))
        if args.showpriv:
            if args.location:
                showkey("{0}/{1}/private.key".format(dir, args.location))
            else:
                showkey("{}/default/private.key".format(dir))
        if args.genpsk:
            genpsk()
        if args.listkdir:
            list_key_dirs()
        if args.showinterface:
            try:
                intf = WireGuardIf(args.showinterface, create=False, debug=False)
                print(intf.operational.show_interface())
            # the interface does not exists
            except Exception:
                pass
        if args.delkdir:
            if args.location:
                del_key_dir(args.location)
            else:
                del_key_dir("default")

    except ConfigError as e:
        print(e)
        sys.exit(1)