nntp: make ->ALL Xref generation more fuzzy

For ->ALL users, this mitigates the regression introduced
by commit 811b8d3cbaa790f59b7b107140b86248da16499b
("nntp: xref: use ->ALL extindex if available"), since
it's common to cross post messages to some mailing
lists with per-list trailers for unsubscribe information.

We won't bother dealing with Bcc-ed messages since those
are nearly all spam when it comes to public mailing lists.

Fixes: 811b8d3cbaa790f5 ("nntp: xref: use ->ALL extindex if available")
Link: https://public-inbox.org/meta/20201130194201.GA6687@dcvr/

1 files changed, 36 insertions, 14 deletions

diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 3b16a66a..e0916011 100644
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -17,6 +17,8 @@ use PublicInbox::DS qw(now);
 use Digest::SHA qw(sha1_hex);
 use Time::Local qw(timegm timelocal);
 use PublicInbox::GitAsyncCat;
+use PublicInbox::Address;
+
 use constant {
         LINE_MAX => 512, # RFC 977 section 2.3
         r501 => '501 command syntax error',
@@ -417,27 +419,42 @@ sub header_append ($$$) {
         $hdr->header_set($k, @v, $v);
 }
 
+sub xref_by_tc ($$$) {
+        my ($xref, $pi_cfg, $smsg) = @_;
+        my $by_addr = $pi_cfg->{-by_addr};
+        my $groups = $pi_cfg->{-by_newsgroup};
+        my $mid = $smsg->{mid};
+        for my $f (qw(to cc)) {
+                my @ibxs = map {
+                        $by_addr->{lc($_)} // ()
+                } (PublicInbox::Address::emails($smsg->{$f} // ''));
+                for my $ibx (@ibxs) {
+                        $groups->{my $ngname = $ibx->{newsgroup}} or next;
+                        next if defined $xref->{$ngname};
+                        $xref->{$ngname} = eval { $ibx->mm->num_for($mid) };
+                }
+        }
+}
+
 sub xref ($$$) {
         my ($self, $cur_ibx, $smsg) = @_;
         my $nntpd = $self->{nntpd};
-        my $cur_ngname = $cur_ibx->{newsgroup};
-        my $ret = "$nntpd->{servername} $cur_ngname:$smsg->{num}";
+        my $cur_ng = $cur_ibx->{newsgroup};
+        my $xref;
         if (my $ALL = $nntpd->{pi_config}->ALL) {
-                if (my $ary = $ALL->nntp_xref_for($cur_ibx, $smsg)) {
-                        $ret .= join(' ', '', @$ary) if scalar(@$ary);
-                }
-                # better off wrong than slow if there's thousands of groups,
-                # so no fallback to the slow path below:
+                $xref = $ALL->nntp_xref_for($cur_ibx, $smsg);
+                xref_by_tc($xref, $nntpd->{pi_config}, $smsg);
         } else { # slow path
+                $xref = { $cur_ng => $smsg->{num} };
                 my $mid = $smsg->{mid};
-                my $groups = $nntpd->{pi_config}->{-by_newsgroup};
-                for my $xngname (@{$nntpd->{groupnames}}) {
-                        next if $cur_ngname eq $xngname;
-                        my $xibx = $groups->{$xngname} or next;
-                        my $num = eval { $xibx->mm->num_for($mid) } or next;
-                        $ret .= " $xngname:$num";
+                for my $ibx (values %{$nntpd->{pi_config}->{-by_newsgroup}}) {
+                        next if defined($xref->{$ibx->{newsgroup}});
+                        my $num = eval { $ibx->mm->num_for($mid) } // next;
+                        $xref->{$ibx->{newsgroup}} = $num;
                 }
         }
+        my $ret = "$nntpd->{servername} $cur_ng:".delete($xref->{$cur_ng});
+        $ret .= " $_:$xref->{$_}" for (sort keys %$xref);
         $ret;
 }
 
@@ -930,8 +947,13 @@ sub cmd_over ($;$) {
                 more($self, '224 Overview information follows (multi-line)');
 
                 # Only set article number column if it's the current group
+                # (RFC 3977 8.3.2)
                 my $self_ng = $self->{ng};
-                $smsg->{num} = 0 if (!$self_ng || $self_ng ne $ng);
+                if (!$self_ng || $self_ng ne $ng) {
+                        # set {-orig_num} for nntp_xref_for
+                        $smsg->{-orig_num} = $smsg->{num};
+                        $smsg->{num} = 0;
+                }
                 more($self, over_line($self, $ng, $smsg));
                 '.';
         } else {