+sub header_append ($$$) {
+ my ($hdr, $k, $v) = @_;
+ my @v = $hdr->header($k);
+ foreach (@v) {
+ return if $v eq $_;
+ }
+ $hdr->header_set($k, @v, $v);
+}
+
+sub xref ($$$$) {
+ my ($self, $ng, $n, $mid) = @_;
+ my $ret = "$ng->{domain} $ng->{newsgroup}:$n";
+
+ # num_for is pretty cheap and sometimes we'll lookup the existence
+ # of an article without getting even the OVER info. In other words,
+ # I'm not sure if its worth optimizing by scanning To:/Cc: and
+ # PublicInbox::ExtMsg on the PSGI end is just as expensive
+ foreach my $other (@{$self->{nntpd}->{grouplist}}) {
+ next if $ng eq $other;
+ my $num = eval { $other->mm->num_for($mid) } or next;
+ $ret .= " $other->{newsgroup}:$num";
+ }
+ $ret;
+}
+
+sub set_nntp_headers ($$$$$) {
+ my ($self, $hdr, $ng, $n, $mid) = @_;
+
+ # clobber some
+ my $xref = xref($self, $ng, $n, $mid);
+ $hdr->header_set('Xref', $xref);
+ $xref =~ s/:\d+//g;
+ $hdr->header_set('Newsgroups', (split(/ /, $xref, 2))[1]);
+ header_append($hdr, 'List-Post', "<mailto:$ng->{-primary_address}>");
+ if (my $url = $ng->base_url) {
+ $mid = mid_escape($mid);
+ header_append($hdr, 'Archived-At', "<$url$mid/>");
+ header_append($hdr, 'List-Archive', "<$url>");
+ }
+}
+