handle receiving same file more than once

`scan-dir`, because of `IO.watch`, can emit the same path multiple
times; we don't want messing up the index (especially the bayesian
one!) because of that

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/MaildirIndexer/Index/ByRef.rakumod b/lib/MaildirIndexer/Index/ByRef.rakumod
index d044272..f9fc4f9 100644
--- a/lib/MaildirIndexer/Index/ByRef.rakumod
+++ b/lib/MaildirIndexer/Index/ByRef.rakumod
@@ -14,6 +14,10 @@ method dump() {
 
 method add-mail(MaildirIndexer::Email:D $email, Str:D $mailbox --> Nil) {
     MaildirIndexer::LogTimelineSchema::Index::Add.log: :class('ByRef'),:$mailbox, -> {
+        # ignore adding the same file twice, files in maildirs are
+        # immutable
+        return if %!id-for-file{ $email.path }:exists;
+
         my $id = $email.message-id or return;
         %!id-for-file{ $email.path } = $id;
         %!mailboxes-for-id{ $id }.push($mailbox);
@@ -23,12 +27,12 @@ method add-mail(MaildirIndexer::Email:D $email, Str:D $mailbox --> Nil) {
 
 method del-path(IO:D $file, Str:D $mailbox --> Nil) {
     MaildirIndexer::LogTimelineSchema::Index::Rm.log: :class('ByRef'),:$mailbox, -> {
-        my $id = %!id-for-file{ $file.path }:delete;
+        my $id = %!id-for-file{ $file.path }:delete or return;
         with %!mailboxes-for-id{ $id } {
             with .grep($mailbox):k -> $pos {
                 .splice($pos,1);
             }
-         }
+        }
         return;
     }
 }