lei_store: keyword extraction from mbox and Maildir

Dovecot, mutt, and likely much other software support mbox
Status/X-Status headers.  Ensure we have a way to extract these
headers as JMAP-compatible keywords before removing them for git
storage.

->add_eml now accepts setting keywords at import time,
and will probably be called like this:

	$lst->add_eml($eml, $lst->mbox_keywords($eml));
	$lst->add_eml($eml, $lst->maildir_keywords($fn));

1 files changed, 22 insertions, 1 deletions

diff --git a/lib/PublicInbox/LeiStore.pm b/lib/PublicInbox/LeiStore.pm
index c95df785..553adbc8 100644
--- a/lib/PublicInbox/LeiStore.pm
+++ b/lib/PublicInbox/LeiStore.pm
@@ -162,8 +162,27 @@ sub remove_eml_keywords {
         \@docids;
 }
 
+# cf: https://doc.dovecot.org/configuration_manual/mail_location/mbox/
+my %status2kw = (F => 'flagged', A => 'answered', R => 'seen', T => 'draft');
+# O (old/non-recent), and D (deleted) aren't in JMAP,
+# so probably won't be supported by us.
+sub mbox_keywords {
+        my $eml = $_[-1];
+        my $s = "@{[$eml->header_raw('X-Status'),$eml->header_raw('Status')]}";
+        my %kw;
+        $s =~ s/([FART])/$kw{$status2kw{$1}} = 1/sge;
+        sort(keys %kw);
+}
+
+# cf: https://cr.yp.to/proto/maildir.html
+my %c2kw = ('D' => 'draft', F => 'flagged', R => 'answered', S => 'seen');
+sub maildir_keywords {
+        $_[-1] =~ /:2,([A-Z]+)\z/i ?
+                sort(map { $c2kw{$_} // () } split(//, $1)) : ();
+}
+
 sub add_eml {
-        my ($self, $eml) = @_;
+        my ($self, $eml, @kw) = @_;
         my $eidx = eidx_init($self);
         my $oidx = $eidx->{oidx};
         my $smsg = bless { -oidx => $oidx }, 'PublicInbox::Smsg';
@@ -178,6 +197,7 @@ sub add_eml {
                         my $idx = $eidx->idx_shard($docid);
                         $oidx->add_xref3($docid, -1, $smsg->{blob}, '.');
                         $idx->shard_add_eidx_info($docid, '.', $eml); # List-Id
+                        $idx->shard_add_keywords($docid, @kw) if @kw;
                 }
         } else {
                 $smsg->{num} = $oidx->adj_counter('eidx_docid', '+');
@@ -185,6 +205,7 @@ sub add_eml {
                 $oidx->add_xref3($smsg->{num}, -1, $smsg->{blob}, '.');
                 my $idx = $eidx->idx_shard($smsg->{num});
                 $idx->index_raw($msgref, $eml, $smsg);
+                $idx->shard_add_keywords($smsg->{num}, @kw) if @kw;
         }
         $smsg->{blob}
 }