"""
ldapdns.py - basic functions for dealing dc-style DNs and SRV RRs
(c) by Michael Stroeder <michael@stroeder.com>

This module is distributed under the terms of the
GPL (GNU GENERAL PUBLIC LICENSE) Version 2
(see http://www.gnu.org/copyleft/gpl.html)

$Id: ldapdns.py,v 1.18 2004/11/17 15:59:47 michael Exp $

Requirements:
This module uses module DNS: http://pydns.sourceforge.net

Python compability note:
This module only works with Python 2.0+ since string methods
instead of string module and list comprehensions are used.
"""

__version__ = '0.0.5'

import socket,ldaputil.base

try:
  import DNS
except ImportError:
  dns_module_avail=0
else:
  try:
    DNS.ParseResolvConf()
  except:
    dns_module_avail=0
  else:
    dns_module_avail=1

def dcdn2dnsdomain(dn=''):
  """convert dc-style DN to DNS domain name (see RFC 2247)"""
  dn_components = ldaputil.base.explode_dn(dn.lower())
  dns_components = []
  for i in range(len(dn_components)-1,-1,-1):
    attrtype,value = dn_components[i].split('=',1)
    if attrtype!='dc':
      break
    dns_components.append(value.strip())
  dns_components.reverse()
  return '.'.join(dns_components)


def dnsdomain2dcdn(domain=''):
  """convert DNS domain name to dc-style DN (see RFC 2247)"""
  return ','.join(
    [
      'dc=%s' % d
      for d in domain.split('.')
    ]
  )


def ldapSRV(dns_name,dns_resolver=None):
  """
  Look up SRV RR with name _ldap._tcp.dns_name and return
  list of tuples of results.
  
  dns_name
        Domain name
  dns_resolver
        Address/port tuple of name server to use.
  """
  if not dns_name:
    return []
  if dns_resolver is None:
    srv_req = DNS.Request(qtype='srv')
  else:
    srv_req = DNS.Request(qtype='srv',server=dns_resolver)
  srv_result = srv_req.req('_ldap._tcp.%s' % dns_name)
  srv_result_answers = [
    # priority,weight,port,hostname
    (
      res['data'][0],
      res['data'][1],
      res['data'][2],
      res['data'][3]
    )
    for res in srv_result.answers
    if res['typename']=='SRV'
  ]
  srv_result_answers.sort()
  return srv_result_answers


def dcDNSLookup(dn):
  if dn and dns_module_avail:
    try:
      dns_result = ldapSRV(dcdn2dnsdomain(dn))
    except (DNS.Error,socket.error),e:
      return []
    else:
      return [
        '%s%s' % (host,(':%d' % port)*(port!=389))
        for prio,weight,port,host in dns_result
      ]
  else:
    return []