#!/usr/bin/env python3

import argparse
import configparser
import ipaddress
import logging
import logging.handlers
import os
import socket
import sys
##
import requests
import requests.auth
from pyroute2 import IPRoute
try:
    # https://www.freedesktop.org/software/systemd/python-systemd/journal.html#journalhandler-class
    from systemd import journal
    _has_journald = True
except ImportError:
    _has_journald = False


# 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


logfile = '/var/log/tunnelbroker_manager.log'
# Prep the log file.
logfile = os.path.abspath(os.path.expanduser(logfile))
os.makedirs(os.path.dirname(logfile), exist_ok = True, mode = 0o0700)
if not os.path.isfile(logfile):
    with open(logfile, 'w') as fh:
        fh.write('')
os.chmod(logfile, 0o0600)

# And set up logging.
_cfg_args = {'handlers': [],
             'level': logging.DEBUG}
if _has_journald:
    # There were some weird changes somewhere along the line.
    try:
        # But it's *probably* this one.
        h = journal.JournalHandler()
    except AttributeError:
        h = journal.JournaldLogHandler()
    # Systemd includes times, so we don't need to.
    h.setFormatter(logging.Formatter(style = '{',
                                     fmt = ('{name}:{levelname}:{name}:{filename}:'
                                            '{funcName}:{lineno}: {message}')))
    _cfg_args['handlers'].append(h)
h = logging.handlers.RotatingFileHandler(logfile,
                                         encoding = 'utf8',
                                         # Disable rotating for now.
                                         # maxBytes = 50000000000,
                                         # backupCount = 30
                                         )
h.setFormatter(logging.Formatter(style = '{',
                                 fmt = ('{asctime}:'
                                        '{levelname}:{name}:{filename}:'
                                        '{funcName}:{lineno}: {message}')))
_cfg_args['handlers'].append(h)
logging.basicConfig(**_cfg_args)
logger = logging.getLogger('HE Tunnelbroker Manager')
logger.info('Logging initialized.')


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))
        logger.debug('Using config path: {0}'.format(self.conf_file))
        self._conf = configparser.ConfigParser(allow_no_value = True,
                                               interpolation = configparser.ExtendedInterpolation())
        try:
            self._conf.read(self.conf_file)
            logger.debug('Read in configuration successfully.')
        except Exception as e:
            logger.error('Failed reading configuration: {0}'.format(e))
            raise e
        if len(self._conf.sections()) < 1:
            logger.error('Config file has no sections/tunnels defined.')
            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():
            logger.error(('The tun_id {0} is not a valid tunnel ID. '
                          'Valid tunnels are: {1}').format(self.tun_id, ', '.join(self._conf.sections())))
            raise ValueError('tun_id not a valid tunnel ID')
        elif not self.tun_id:
            self.tun_id = self._conf.sections()[0]
            logger.debug('Automatically set tun_id to {0}'.format(self.tun_id))
        self.cfg = self._conf[self.tun_id]
        self.server = ipaddress.ip_address(self.cfg['server'])
        logger.debug('Set server IP to {0}.'.format(str(self.server)))
        self.addrs = [ipaddress.ip_network(ip.strip()) for ip in self.cfg['allocations'].split(',')]
        logger.debug('Using address allocations: {0}'.format(', '.join([str(ip) for ip in self.addrs])))
        for k in ('user', 'update_key'):
            setattr(self, k, self.cfg[k])
            # Don't log creds, even in debug.
            # logger.debug('Set {0} to {1}'.format(k, getattr(self, k)))
        self.iface_name = 'he-{0}'.format(self.tun_id)

    def _get_my_ip(self):
        if self.wan:
            logger.debug('WAN IP tunneling enabled; fetching WAN IP.')
            req = requests.get(self.ipget_url, params = self.ipget_params)
            if not req.ok:
                logger.error('Could not fetch self IP. Request returned {0}.'.format(req.status_code))
                raise RuntimeError('Could not fetch self IP')
            self.my_ip = ipaddress.ip_address(req.json()['ip'])
            logger.debug('Set my_ip to {0}.'.format(str(self.my_ip)))
        else:
            logger.debug('WAN IP tunneling disabled; fetching LAN IP.')
            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.
                logger.error('Could not determine default route. Does this machine have a single default route?')
                raise RuntimeError('Could not determine default IPv4 route')
            self.my_ip = ipaddress.ip_address(_defrt[0]['attrs']['RTA_PREFSRC'])
            logger.debug('Set my_ip to {0}.'.format(str(self.my_ip)))
        return(None)

    def start(self):
        if self.force_update:
            logger.debug('IP update forced; updating.')
            self._get_my_ip()
            self.update()
        if not self.ipr:
            self.ipr = IPRoute()
        try:
            self.ipr.link('add',
                          ifname = self.iface_name,
                          kind = 'sit',
                          sit_local = str(self.my_ip),
                          sit_remote = str(self.server),
                          sit_ttl = 255)
            logger.debug('Added link {0} successfully.'.format(self.iface_name))
        except Exception as e:
            logger.error('Could not create link for link {0} '
                         '(maybe it already exists?): {1}'.format(self.iface_name, e))
            raise e
        try:
            self.iface_idx = self.ipr.link_lookup(ifname = self.iface_name)[0]
            logger.debug('Found link {0} at index {1}.'.format(self.iface_name, self.iface_idx))
        except Exception as e:
            logger.error('Could not set iface_idx for iface name {0}: {1}'.format(self.iface_name, e))
            raise e
        try:
            self.ipr.link('set', index = self.iface_idx, state = 'up', mtu = 1480)
            logger.debug('Set link {0} status to UP.'.format(self.iface_name))
        except Exception as e:
            logger.error(('Could not bring up link for iface name {0} at index {1}: '
                          '{2}').format(self.iface_name, self.iface_idx, e))
            raise e
        for a in self.addrs:
            try:
                self.ipr.addr('add',
                              index = self.iface_idx,
                              address = str(a.network_address),
                              mask = a.prefixlen,
                              family = socket.AF_INET6)
                logger.debug('Added address {0} to link {1}.'.format(str(a), self.iface_name))
            except Exception as e:
                logger.error(('Could not add address {0} on link {1}: '
                              '{2}').format(str(a), self.iface_name, e))
                raise e
        try:
            self.ipr.route('add', dst = 'default', oif = self.iface_idx, family = socket.AF_INET6)
            logger.debug('Added default route for link {0}.'.format(self.iface_name))
        except Exception as e:
            logger.error(('Could not add default IPv6 route on link {0}: {1}').format(self.iface_name, e))
            raise e
        self.ipr.close()
        return(None)

    def stop(self):
        if not self.ipr:
            self.ipr = IPRoute()
        try:
            self.iface_idx = self.ipr.link_lookup(ifname = self.iface_name)[0]
            logger.debug('Found link {0} at index {1}.'.format(self.iface_name, self.iface_idx))
        except Exception as e:
            logger.error('Could not set iface_idx for link {0}: {1}'.format(self.iface_name, e))
            raise e
        try:
            self.ipr.link('set', index = self.iface_idx, state = 'down')
        except Exception as e:
            logger.error('Could not bring down link {0}: {1} (continuing anyways)'.format(self.iface_name, e))
        try:
            self.ipr.route('del', dst = 'default', oif = self.iface_idx, family = socket.AF_INET6)
        except Exception as e:
            logger.error(('Could not remove default IPv6 route on link {0}: '
                          '{1} (continuing anyways)').format(self.iface_name, e))
        try:
            self.ipr.link('del', index = self.iface_idx)
            logger.debug('Deleted link {0}.'.format(self.iface_name))
        except Exception as e:
            logger.error('Could not delete link {0}: {1}'.format(self.iface_name, e))
            raise e
        self.ipr.close()
        return(None)

    def update(self, oneshot = False):
        self._get_my_ip()
        auth_handler = requests.auth.HTTPBasicAuth(self.user, self.update_key)
        logger.debug('Set auth handler.')
        logger.debug('Requesting IP update at provider.')
        req = requests.get(self.api_base,
                           params = {'hostname': self.tun_id,
                                     'myip': self.my_ip},
                           auth = auth_handler)
        if not req.ok:
            logger.error('Could not update IP at provider. Request returned {0}.'.format(req.status_code))
            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'):
            logger.error('Returned following failure message: {0}'.format(req.content.decode('utf-8')))
            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 ("start", "stop", or "update"). "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()
    logger.debug('Invoked with args: {0}'.format(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()