feat(nest): @-addressing, addressed-crow-must-respond, deliver back to requester (#11)

nestlog.go

@@ -102,6 +102,20 @@ func (s *MessageStore) After(nestID string, lastID int) []Message {
 // All returns every message in a nest, oldest first.
 func (s *MessageStore) All(nestID string) []Message { return s.After(nestID, 0) }
 
+// ByMsgID finds one stored message by its "<nest_id>-<n>" id.
+func (s *MessageStore) ByMsgID(msgID string) (Message, bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for _, msgs := range s.log {
+		for _, m := range msgs {
+			if m.MsgID() == msgID {
+				return m, true
+			}
+		}
+	}
+	return Message{}, false
+}
+
 func (s *MessageStore) save(nestID string) error {
 	if err := os.MkdirAll(s.dir, 0o755); err != nil {
 		return err