imap: implement MoveMessages handling

Implement MoveMessages in the imap backend. go-imap includes the MOVE
Imap extension by default, and if a server does not support it the
command fallsback to a copy-and-delete operation. Servers with the MOVE
extension will see a slight performance increase when moving messages
due to fewer round trips. The IMAP implementation uses a MessagesMoved
worker message to avoid polling the destination mailbox.

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

worker/imap/movecopy.go

@@ -46,3 +46,20 @@ func (imapw *IMAPWorker) handleAppendMessage(msg *types.AppendMessage) {
 		imapw.worker.PostMessage(&types.Done{Message: types.RespondTo(msg)}, nil)
 	}
 }
+
+func (imapw *IMAPWorker) handleMoveMessages(msg *types.MoveMessages) {
+	uids := toSeqSet(msg.Uids)
+	if err := imapw.client.UidMove(uids, msg.Destination); err != nil {
+		imapw.worker.PostMessage(&types.Error{
+			Message: types.RespondTo(msg),
+			Error:   err,
+		}, nil)
+	} else {
+		imapw.worker.PostMessage(&types.MessagesMoved{
+			Message:     types.RespondTo(msg),
+			Destination: msg.Destination,
+			Uids:        msg.Uids,
+		}, nil)
+		imapw.worker.PostMessage(&types.Done{Message: types.RespondTo(msg)}, nil)
+	}
+}

worker/imap/worker.go

@@ -205,6 +205,8 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 		w.handleAnsweredMessages(msg)
 	case *types.CopyMessages:
 		w.handleCopyMessages(msg)
+	case *types.MoveMessages:
+		w.handleMoveMessages(msg)
 	case *types.AppendMessage:
 		w.handleAppendMessage(msg)
 	case *types.SearchDirectory: