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/

4 files changed, 37 insertions, 2 deletions

diff --git a/lib/PublicInbox/Mbox.pm b/lib/PublicInbox/Mbox.pm
index 18db9d38..e1abf7ec 100644
--- a/lib/PublicInbox/Mbox.pm
+++ b/lib/PublicInbox/Mbox.pm
@@ -229,6 +229,11 @@ sub mbox_all {
                 return PublicInbox::WWW::need($ctx, 'Overview');
 
         my $qopts = $ctx->{qopts} = { relevance => -2 }; # ORDER BY docid DESC
+
+        # {threadid} limits results to a given thread
+        # {threads} collapses results from messages in the same thread,
+        # allowing us to use ->expand_thread w/o duplicates in our own code
+        $qopts->{threadid} = $over->mid2tid($ctx->{mid}) if defined($ctx->{mid});
         $qopts->{threads} = 1 if $q->{t};
         $srch->query_approxidate($ctx->{ibx}->git, $q_string);
         my $mset = $srch->mset($q_string, $qopts);
diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index d6409b2a..82034b30 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -282,13 +282,35 @@ SELECT eidx_key FROM inboxes WHERE ibx_id = ?
         $rows;
 }
 
+sub mid2tid {
+        my ($self, $mid) = @_;
+        my $dbh = dbh($self);
+
+        my $sth = $dbh->prepare_cached(<<'', undef, 1);
+SELECT id FROM msgid WHERE mid = ? LIMIT 1
+
+        $sth->execute($mid);
+        my $id = $sth->fetchrow_array or return;
+        $sth = $dbh->prepare_cached(<<'', undef, 1);
+SELECT num FROM id2num WHERE id = ? AND num > ?
+ORDER BY num ASC LIMIT 1
+
+        $sth->execute($id, 0);
+        my $num = $sth->fetchrow_array or return;
+        $sth = $dbh->prepare(<<'');
+SELECT tid FROM over WHERE num = ? LIMIT 1
+
+        $sth->execute($num);
+        $sth->fetchrow_array;
+}
+
 sub next_by_mid {
         my ($self, $mid, $id, $prev) = @_;
         my $dbh = dbh($self);
 
         unless (defined $$id) {
                 my $sth = $dbh->prepare_cached(<<'', undef, 1);
-        SELECT id FROM msgid WHERE mid = ? LIMIT 1
+SELECT id FROM msgid WHERE mid = ? LIMIT 1
 
                 $sth->execute($mid);
                 $$id = $sth->fetchrow_array;
diff --git a/lib/PublicInbox/Search.pm b/lib/PublicInbox/Search.pm
index 5133a3b7..6c3d9f93 100644
--- a/lib/PublicInbox/Search.pm
+++ b/lib/PublicInbox/Search.pm
@@ -386,6 +386,12 @@ sub mset {
                                         sortable_serialise($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);
diff --git a/lib/PublicInbox/WWW.pm b/lib/PublicInbox/WWW.pm
index 9ffcb879..a8f1ad17 100644
--- a/lib/PublicInbox/WWW.pm
+++ b/lib/PublicInbox/WWW.pm
@@ -68,7 +68,9 @@ sub call {
                         my ($idx, $fn) = ($3, $4);
                         return invalid_inbox_mid($ctx, $1, $2) ||
                                 get_attach($ctx, $idx, $fn);
-                } elsif ($path_info =~ m!$INBOX_RE/!o) {
+                } elsif ($path_info =~ m!$INBOX_RE/$MID_RE/\z!o) {
+                        return invalid_inbox_mid($ctx, $1, $2) || mbox_results($ctx);
+                } elsif ($path_info =~ m!$INBOX_RE/\z!o) {
                         return invalid_inbox($ctx, $1) || mbox_results($ctx);
                 }
         }