imap: omit $UID_END from mailbox name, use index

Having two large numbers separated by a dash can make visual
comparisons difficult when numbers are in the 3,000,000 range
for LKML.  So avoid the $UID_END value, since it can be
calculated from $UID_MIN.  And we can avoid large values of
$UID_MIN, too, by instead storing the block index and just
multiplying it by 50000 (and adding 1) on the server side.

Of course, LKML still goes up to 72, at the moment.

1 files changed, 6 insertions, 9 deletions

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 6f64dff9..5865822f 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -197,14 +197,10 @@ sub ensure_ranges_exist ($$$) {
         my $mailboxes = $imapd->{mailboxes};
         my $mb_top = $ibx->{newsgroup};
         my @created;
-        my $uid_min = UID_BLOCK * int($max/UID_BLOCK) + 1;
-        my $uid_end = $uid_min + UID_BLOCK - 1;
-        while ($uid_min > 0) {
-                my $sub_mailbox = "$mb_top.$uid_min-$uid_end";
+        for (my $i = int($max/UID_BLOCK); $i >= 0; --$i) {
+                my $sub_mailbox = "$mb_top.$i";
                 last if exists $mailboxes->{$sub_mailbox};
                 $mailboxes->{$sub_mailbox} = $ibx;
-                $uid_end -= UID_BLOCK;
-                $uid_min -= UID_BLOCK;
                 push @created, $sub_mailbox;
         }
         return unless @created;
@@ -216,9 +212,9 @@ sub cmd_examine ($$$) {
         my ($self, $tag, $mailbox) = @_;
         my ($ibx, $mm, $max);
 
-        if ($mailbox =~ /\A(.+)\.([0-9]+)-([0-9]+)\z/) {
-                # old mail: inbox.comp.foo.$uid_min-$uid_end
-                my ($mb_top, $uid_min, $uid_end) = ($1, $2 + 0, $3 + 0);
+        if ($mailbox =~ /\A(.+)\.([0-9]+)\z/) {
+                # old mail: inbox.comp.foo.$uid_block_idx
+                my ($mb_top, $uid_min) = ($1, $2 * UID_BLOCK + 1);
 
                 $ibx = $self->{imapd}->{mailboxes}->{lc $mailbox} or
                         return "$tag NO Mailbox doesn't exist: $mailbox\r\n";
@@ -227,6 +223,7 @@ sub cmd_examine ($$$) {
                 $max = $mm->max // 0;
                 $self->{uid_min} = $uid_min;
                 ensure_ranges_exist($self->{imapd}, $ibx, $max);
+                my $uid_end = $uid_min + UID_BLOCK - 1;
                 $max = $uid_end if $max > $uid_end;
         } else { # check for dummy inboxes
                 $ibx = $self->{imapd}->{mailboxes}->{lc $mailbox} or