add FQDN type to use instead of str to keep host and domain separate

nsupdate/main/_tests/test_dnstools.py

@@ -10,13 +10,22 @@ pytestmark = pytest.mark.django_db
 
 from dns.resolver import NXDOMAIN, NoAnswer
 
-from ..dnstools import add, delete, update, query_ns, rev_lookup, parse_name, update_ns, SameIpError, DnsUpdateError
+from ..dnstools import (add, delete, update, query_ns, rev_lookup, parse_name, update_ns,
+                        SameIpError, DnsUpdateError, FQDN)
 
 # see also conftest.py
 BASEDOMAIN = 'nsupdate.info'
 INVALID_HOST = 'test999.' + BASEDOMAIN  # this can't get updated
 
 
+class TestFQDN(object):
+    def test_create(self):
+        fqdn = FQDN('test', 'example.org')
+        assert fqdn.host == 'test'
+        assert fqdn.domain == 'example.org'
+        assert str(fqdn) == 'test.example.org'
+
+
 def remove_records(host, records=('A', 'AAAA', )):
     # make sure the records are not there
     for record in records:

nsupdate/main/dnstools.py

@@ -18,6 +18,7 @@ UNAVAILABLE_RETRY = 300.0
 
 import time
 from datetime import timedelta
+from collections import namedtuple
 
 import logging
 logger = logging.getLogger(__name__)
@@ -35,6 +36,29 @@ import dns.tsigkeyring
 from django.utils.timezone import now
 
 
+class FQDN(namedtuple('FQDN', ['host', 'domain'])):
+    """
+    named tuple to represent a fully qualified domain name:
+
+    * a host in a zone/domain
+    * just a zone/domain (give host=None when creating)
+
+    use this instead of str so that the information is not lost
+    what the host part is vs. what the domain part is.
+
+    e.g. foo.bar.example.org could be a host foo in domain bar.example.org
+    or a host foo.bar in domain example.org.
+    """
+    def __str__(self):
+        """
+        when transforming this into a str, just give the fqdn
+        """
+        if self.host:
+            return self.host + '.' + self.domain
+        else:
+            return self.domain
+
+
 Timeout = dns.resolver.Timeout
 NoNameservers = dns.resolver.NoNameservers