#!/usr/bin/env python3

import argparse
import configparser
import ipaddress
import os
import socket
##
import requests
import requests.auth
from pyroute2 import IPDB
from pyroute2 import IPRoute


# TODO: add checking to see if we're already configured.


# https://wiki.archlinux.org/index.php/IPv6_tunnel_broker_setup
# https://forums.he.net/index.php?topic=3153.0
# https://gist.github.com/pklaus/960672


class TunnelBroker(object):
    ipget_url = 'https://ipv4.clientinfo.square-r00t.net/'
    ipget_params = {'raw': '1'}
    api_base = 'https://ipv4.tunnelbroker.net/nic/update'

    def __init__(self, conf, tun_id = None, wan_ip = True, update = True, *args, **kwargs):
        self.my_ip = None
        self.user = None
        self.update_key = None
        self.ipr = None
        self.iface_idx = None
        self.wan = wan_ip
        self.force_update = update
        self.conf_file = os.path.abspath(os.path.expanduser(conf))
        self._conf = configparser.ConfigParser(allow_no_value = True,
                                               interpolation = configparser.ExtendedInterpolation())
        self._conf.read(self.conf_file)
        if len(self._conf.sections()) < 1:
            raise RuntimeError('Config file has no sections/tunnels defined')
        self.tun_id = tun_id
        if self.tun_id and self.tun_id not in self._conf.sections():
            raise ValueError('tun_id not a valid tunnel ID')
        elif not self.tun_id:
            self.tun_id = self._conf.sections()[0]
        self.cfg = self._conf[self.tun_id]
        self.server = ipaddress.ip_address(self.cfg['server'])
        self.addrs = [ipaddress.ip_network(ip.strip()) for ip in self.cfg['allocations'].split(',')]
        for k in ('user', 'update_key'):
            setattr(self, k, self.cfg[k])

    def _get_my_ip(self):
        if self.wan:
            req = requests.get(self.ipget_url, params = self.ipget_params)
            if not req.ok:
                raise RuntimeError('Could not fetch self IP')
            self.my_ip = ipaddress.ip_address(req.json()['ip'])
        else:
            if not self.ipr:
                self.ipr = IPRoute()
            _defrt = self.ipr.get_default_routes(family = socket.AF_INET)
            if len(_defrt) != 1:  # This (probably) WILL fail on multipath systems.
                raise RuntimeError('Could not determine default IPv4 route')
            self.my_ip = ipaddress.ip_address(_defrt[0]['attrs']['RTA_PREFSRC'])
        return(None)

    def start(self):
        if self.force_update:
            self._get_my_ip()
            self.update()
        if not self.ipr:
            self.ipr = IPRoute()
        self.ipr.link('add',
                      ifname = 'sit-he-{0}'.format(self.tun_id),
                      kind = 'sit',
                      ipip_local = self.my_ip,
                      ipip_remote = self.server,
                      ipip_ttl = 255)
        self.iface_idx = self.ipr.link_lookup(ifname = 'sit-he-{0}'.format(self.tun_id))[0]
        self.ipr.link('set', index = self.iface_idx, state = 'up', mtu = 1480)
        for a in self.addrs:
            self.ipr.addr('add',
                          index = self.iface_idx,
                          address = str(a),
                          mask = a.prefixlen,
                          family = socket.AF_INET6)
        self.ipr.route('add', dst = '::', mask = 0, oif = self.iface_idx, family = socket.AF_INET6)
        self.ipr.close()
        return(None)

    def stop(self):
        if not self.ipr:
            self.ipr = IPRoute()
        self.iface_idx = self.ipr.link_lookup(ifname = 'sit-he-{0}'.format(self.tun_id))[0]
        self.ipr.link('set', index = self.iface_idx, state = 'down')
        self.ipr.route('del', dst = '::', mask = 0, oif = self.iface_idx, family = socket.AF_INET6)
        self.ipr.link('set', index = self.iface_idx, state = 'down')
        self.ipr.link('del', index = self.iface_idx)
        self.ipr.close()
        return(None)

    def update(self, oneshot = False):
        self._get_my_ip()
        auth_handler = requests.auth.HTTPBasicAuth(self.user, self.update_key)
        req = requests.get(self.api_base,
                           params = {'hostname': self.tun_id,
                                     'myip': self.my_ip},
                           auth = auth_handler)
        if not req.ok:
            raise RuntimeError('Could not update client IP in tunnel')
        status = req.content.decode('utf-8').split()[0].strip()
        if status.lower() not in ('good', 'nochg'):
            raise RuntimeError('Client IP update returned failure')
        if self.ipr and oneshot:
            self.ipr.close()
            self.ipr = None
        return(None)


def parseArgs():
    args = argparse.ArgumentParser(description = ('Dynamically update and enable/disable '
                                                  'Hurricane Electric Tunnelbroker'))
    args.add_argument('-i', '--no-wan-ip',
                      dest = 'wan_ip',
                      action = 'store_false',
                      help = ('If specified, use the RFC1918 IP address assigned to this machine instead of the WAN '
                              'IP (necessary if this machine is behind NAT)'))
    args.add_argument('-c', '--config',
                      dest = 'conf',
                      default = '~/.config/he_tunnelbroker.ini',
                      help = ('The path to the config. '
                              'Default: ~/.config/he_tunnelbroker.ini'))
    args.add_argument('-t', '--tunnel-id',
                      dest = 'tun_id',
                      help = ('The tunnel profile ID/name to use in -c/--config. '
                              'Default is to use the first one found.'))
    args.add_argument('-u', '--no-update',
                      dest = 'update',
                      action = 'store_false',
                      help = ('If specified, do not perform the automatic update for start operations. Has no effect '
                              'for other operations'))
    args.add_argument('oper',
                      metavar = 'OPERATION',
                      choices = ('update', 'start', 'stop'),
                      help = ('The operation to perform. "update" is performed automatically by "start", '
                              'but otherwise will just update the IPv4 address on record at tunnelbroker'))
    return(args)


def main():
    args = parseArgs().parse_args()
    import pprint
    pprint.pprint(vars(args))
    tb = TunnelBroker(**vars(args))
    if args.oper == 'start':
        tb.start()
    elif args.oper == 'stop':
        tb.stop()
    elif args.oper == 'update':
        tb.update(oneshot = True)
    return(None)


if __name__ == '__main__':
    main()