#!/usr/bin/python3

from hippotat import *

import sys
import os

import twisted.internet
import twisted.internet.endpoints
from twisted.web.server import NOT_DONE_YET

#import twisted.web.server import Site
#from twisted.web.resource import Resource

import syslog

clients = { }

defcfg = '''
[DEFAULT]
max_batch_down = 65536
max_queue_time = 10
max_request_time = 54
target_requests_outstanding = 3

[virtual]
mtu = 1500
# network
# [host]
# [relay]

[server]
ipif = userv root ipif %(host)s,%(relay)s,%(mtu)s,slip %(network)s
addrs = 127.0.0.1 ::1
port = 8099

[limits]
max_batch_down = 262144
max_queue_time = 121
max_request_time = 121
target_requests_outstanding = 10
'''

#---------- "router" ----------

def route(packet, saddr, daddr):
  print('TRACE ', saddr, daddr, packet)
  try: client = clients[daddr]
  except KeyError: dclient = None
  if dclient is not None:
    dclient.queue_outbound(packet)
  elif saddr.is_link_local or daddr.is_link_local:
    log_discard(packet, saddr, daddr, 'link-local')
  elif daddr == c.host or daddr not in c.network:
    print('TRACE INBOUND ', saddr, daddr, packet)
    queue_inbound(packet)
  elif daddr == relay:
    log_discard(packet, saddr, daddr, 'relay')
  else:
    log_discard(packet, saddr, daddr, 'no client')

def log_discard(packet, saddr, daddr, why):
  print('DROP ', saddr, daddr, why)
#  syslog.syslog(syslog.LOG_DEBUG,
#                'discarded packet %s -> %s (%s)' % (saddr, daddr, why))

#---------- client ----------

class Client():
  def __init__(self, ip, cs):
    # instance data members
    self._ip = ip
    self._cs = cs
    self.pw = cfg.get(cs, 'password')
    self._rq = collections.deque() # requests
    # self._pq = PacketQueue(...)
    # plus from config:
    #  .max_batch_down
    #  .max_queue_time
    #  .max_request_time
    #  .target_requests_outstanding
    for k in ('max_batch_down','max_queue_time','max_request_time',
              'target_requests_outstanding'):
      req = cfg.getint(cs, k)
      limit = cfg.getint('limits',k)
      self.__dict__[k] = min(req, limit)
    self._pq = PacketQueue(self.max_queue_time)

    def process_arriving_data(self, d):
      for packet in slip.decode(d):
        (saddr, daddr) = packet_addrs(packet)
        if saddr != self._ip:
          raise ValueError('wrong source address %s' % saddr)
        route(packet, saddr, daddr)

    def _req_cancel(self, request):
      request.finish()

    def _req_error(self, err, request):
      self._req_cancel(request)

    def queue_outbound(self, packet):
      self._pq.append(packet)

    def http_request(self, request):
      request.setHeader('Content-Type','application/octet-stream')
      reactor.callLater(self.max_request_time, self._req_cancel, request)
      request.notifyFinish().addErrback(self._req_error, request)
      self._rq.append(request)
      self._check_outbound()

    def _check_outbound(self):
      while True:
        try: request = self._rq[0]
        except IndexError: request = None
        if request and request.finished:
          self._rq.popleft()
          continue

        if not self._pq.nonempty():
          # no packets, oh well
          continue

        if request is None:
          # no request
          break

        # request, and also some non-expired packets
        while True:
          packet = self.pq.popleft()
          if packet is None: break

          encoded = slip.encode(packet)
          
          if request.sentLength > 0:
            if (request.sentLength + len(slip.delimiter)
                + len(encoded) > self.max_batch_down):
              break
            request.write(slip.delimiter)

          request.write(encoded)
          self._pq.popLeft()

        assert(request.sentLength)
        self._rq.popLeft()
        request.finish()
        # round again, looking for more to do

      while len(self._rq) > self.target_requests_outstanding:
        request = self._rq.popleft()
        request.finish()

class IphttpResource(twisted.web.resource.Resource):
  isLeaf = True
  def render_POST(self, request):
    # find client, update config, etc.
    ci = ipaddr(request.args['i'])
    c = clients[ci]
    pw = request.args['pw']
    if pw != c.pw: raise ValueError('bad password')

    # update config
    for r, w in (('mbd', 'max_batch_down'),
                 ('mqt', 'max_queue_time'),
                 ('mrt', 'max_request_time'),
                 ('tro', 'target_requests_outstanding')):
      try: v = request.args[r]
      except KeyError: continue
      v = int(v)
      c.__dict__[w] = v

    try: d = request.args['d']
    except KeyError: d = ''

    c.process_arriving_data(d)
    c.new_request(request)

  def render_GET(self, request):
    return b'<html><body>hippotat</body></html>'

def start_http():
  resource = IphttpResource()
  site = twisted.web.server.Site(resource)
  for addrspec in cfg.get('server','addrs').split():
    try:
      addr = ipaddress.IPv4Address(addrspec)
      endpointfactory = twisted.internet.endpoints.TCP4ServerEndpoint
    except AddressValueError:
      addr = ipaddress.IPv6Address(addrspec)
      endpointfactory = twisted.internet.endpoints.TCP6ServerEndpoint
    ep = endpointfactory(reactor, cfg.getint('server','port'), addr)
    crash_on_defer(ep.listen(site))

#---------- config and setup ----------
        
def process_cfg():
  process_cfg_common_always()

  c.network = ipnetwork(cfg.get('virtual','network'))
  if c.network.num_addresses < 3 + 2:
    raise ValueError('network needs at least 2^3 addresses')

  try:
    c.host = cfg.get('virtual','host')
  except NoOptionError:
    c.host = next(c.network.hosts())

  try:
    c.relay = cfg.get('virtual','relay')
  except NoOptionError:
    for search in c.network.hosts():
      if search == c.host: continue
      c.relay = search
      break

  for cs in cfg.sections():
    if not (':' in cs or '.' in cs): continue
    ci = ipaddr(cs)
    if ci not in c.network:
      raise ValueError('client %s not in network' % ci)
    if ci in clients:
      raise ValueError('multiple client cfg sections for %s' % ci)
    clients[ci] = Client(ci, cs)

  print(repr(c))

  c.ipif_command = cfg.get('server','ipif', vars=c.__dict__)

common_startup(defcfg)
process_cfg()
start_ipif(c.ipif_command, route)
start_http()
common_run()