www: support POST /$INBOX/$MSGID/?x=m&q=

This allows filtering the contents of any existing thread using
a search query.  It uses the existing THREADID column in Xapian
so we can internally add a Xapian OP_FILTER to the results.

This new functionality is orthogonal to the existing `t=1'
parameter which gives mairix-style thread expansion.  It doesn't
make sense to use `t=1' with this functionality, but it's not
disallowed, either.

The indentation change in Over->next_by_mid is to ensure
DBI->prepare_cached can share across both ->next_by_mid
and ->mid2tid.

I also noticed the existing regex for `POST /$INBOX/?x=m&q=' was
allowing extra characters.  With an added \z, it's now as strict
was originally intended and AFAIK nothing was generating invalid
URLs for it

Reported-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Link: https://public-inbox.org/meta/aaniyhk7wfm4e6m5mbukcrhevzoc6ftctyrfwvmz4fkykwwtlj@mverfng6ytas/T/

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/PublicInbox/Search.pm b/lib/PublicInbox/Search.pm
index 5133a3b7..6c3d9f93 100644
--- a/lib/PublicInbox/Search.pm
+++ b/lib/PublicInbox/Search.pm
@@ -386,6 +386,12 @@ sub mset {
                                         sortable_serialise($uid_range->[1]));
                 $query = $X{Query}->new(OP_FILTER(), $query, $range);
         }
+        if (defined(my $tid = $opt->{threadid})) {
+                $tid = sortable_serialise($tid);
+                $query = $X{Query}->new(OP_FILTER(), $query,
+                                $X{Query}->new(OP_VALUE_RANGE(), THREADID, $tid, $tid));
+        }
+
         my $xdb = xdb($self);
         my $enq = $X{Enquire}->new($xdb);
         $enq->set_query($query);