#!/usr/bin/env python3
#
# Copyright (C) 2019-2020 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

from sys import exit
from copy import deepcopy
from netifaces import interfaces

from vyos.config import Config
from vyos.configdict import get_interface_dict
from vyos.configverify import verify_authentication
from vyos.configverify import verify_source_interface
from vyos.configverify import verify_vrf
from vyos.configverify import verify_mtu_ipv6
from vyos.template import render
from vyos.util import call
from vyos import ConfigError
from vyos import airbag
airbag.enable()

def get_config(config=None):
    """
    Retrive CLI config as dictionary. Dictionary can never be empty, as at least the
    interface name will be added or a deleted flag
    """
    if config:
        conf = config
    else:
        conf = Config()
    base = ['interfaces', 'pppoe']
    pppoe = get_interface_dict(conf, base)

    if 'deleted' not in pppoe:
        # We always set the MRU value to the MTU size. This code path only re-creates
        # the old behavior if MRU is not set on the CLI.
        if 'mru' not in pppoe:
            pppoe['mru'] = pppoe['mtu']

    return pppoe

def verify(pppoe):
    if 'deleted' in pppoe:
        # bail out early
        return None

    verify_source_interface(pppoe)
    verify_authentication(pppoe)
    verify_vrf(pppoe)
    verify_mtu_ipv6(pppoe)

    if {'connect_on_demand', 'vrf'} <= set(pppoe):
        raise ConfigError('On-demand dialing and VRF can not be used at the same time')

    # both MTU and MRU have default values, thus we do not need to check
    # if the key exists
    if int(pppoe['mru']) > int(pppoe['mtu']):
        raise ConfigError('PPPoE MRU needs to be lower then MTU!')

    return None

def generate(pppoe):
    # set up configuration file path variables where our templates will be
    # rendered into
    ifname = pppoe['ifname']
    config_pppoe = f'/etc/ppp/peers/{ifname}'
    script_pppoe_pre_up = f'/etc/ppp/ip-pre-up.d/1000-vyos-pppoe-{ifname}'
    script_pppoe_ip_up = f'/etc/ppp/ip-up.d/1000-vyos-pppoe-{ifname}'
    script_pppoe_ip_down = f'/etc/ppp/ip-down.d/1000-vyos-pppoe-{ifname}'
    script_pppoe_ipv6_up = f'/etc/ppp/ipv6-up.d/1000-vyos-pppoe-{ifname}'
    config_wide_dhcp6c = f'/run/dhcp6c/dhcp6c.{ifname}.conf'

    config_files = [config_pppoe, script_pppoe_pre_up, script_pppoe_ip_up,
                    script_pppoe_ip_down, script_pppoe_ipv6_up, config_wide_dhcp6c]

    if 'deleted' in pppoe or 'disable' in pppoe:
        # stop DHCPv6-PD client
        call(f'systemctl stop dhcp6c@{ifname}.service')
        # Hang-up PPPoE connection
        call(f'systemctl stop ppp@{ifname}.service')

        # Delete PPP configuration files
        for file in config_files:
            if os.path.exists(file):
                os.unlink(file)

        return None

    # Create PPP configuration files
    render(config_pppoe, 'pppoe/peer.tmpl', pppoe, permission=0o755)

    # Create script for ip-pre-up.d
    render(script_pppoe_pre_up, 'pppoe/ip-pre-up.script.tmpl', pppoe,
           permission=0o755)
    # Create script for ip-up.d
    render(script_pppoe_ip_up, 'pppoe/ip-up.script.tmpl', pppoe,
           permission=0o755)
    # Create script for ip-down.d
    render(script_pppoe_ip_down, 'pppoe/ip-down.script.tmpl', pppoe,
           permission=0o755)
    # Create script for ipv6-up.d
    render(script_pppoe_ipv6_up, 'pppoe/ipv6-up.script.tmpl', pppoe,
           permission=0o755)

    if 'dhcpv6_options' in pppoe and 'pd' in pppoe['dhcpv6_options']:
        # ipv6.tmpl relies on ifname - this should be made consitent in the
        # future better then double key-ing the same value
        render(config_wide_dhcp6c, 'dhcp-client/ipv6.tmpl', pppoe)

    return None

def apply(pppoe):
    if 'deleted' in pppoe or 'disable' in pppoe:
        call('systemctl stop ppp@{ifname}.service'.format(**pppoe))
        return None

    call('systemctl restart ppp@{ifname}.service'.format(**pppoe))

    return None

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