added validation and runtime detection of addition to a second group

DDNS.pm

@@ -4,6 +4,9 @@ use strict;
 use warnings;
 use Net::DNS;
 use File::Temp qw/tempfile/;
+use Memoize;
+
+memoize('_gethosts');
 
 our $VERSION = '0.2';
 
@@ -21,7 +24,7 @@ sub _validateTypeOrDie {
     my ($t) = @_;
 
     die "Invalid type"
-	unless ($t =~ /^_(vhosts|hostedservers|pureslave|custom)$/);
+	unless ($t =~ /^_(vhosts|pureslave|custom)$/);
 }
 
 sub _fqdn {
@@ -121,11 +124,34 @@ sub _gethosts {
     return @vh;
 }
 
+# Find the type of domin that $dom is. If we don't find it, return
+# undef.  (The domain $dom ends in a dot; the DNS info we find won't;
+# hence the concat of the extra "." after the lc.)
+sub type {
+    my ($this, $dom) = @_;
+
+    _validateOrDie($dom);
+
+    my @vh = $this->get();
+    foreach my $i (@vh) {
+	if (lc($i->{zone})."." eq lc($dom)) {
+	    return $i->{type};
+	}
+    }
+
+    # Didn't find it.
+    return undef;
+}
+
 sub add {
     my ($this, $dom, $master, $type) = @_;
     _validateOrDie($dom);
     my $fqdn = _fqdn($dom, $type);
 
+    if (my $type = $this->type($dom)) {
+	die "Domain $dom already exists [of type $type]";
+    }
+    
     $this->__docmd("update add $fqdn 60 TXT $master");
     $this->cleanup();
 }