feat(claim): arbitration per mode (#5) — first claim wins except conspiracy (#23)

nestapi.go

@@ -132,6 +132,17 @@ func (s *Server) postNestMessage(w http.ResponseWriter, r *http.Request) {
 	// Mode (Epic C, same rule shape as kind): Jev first, header escape, "" when unsure.
 	mode, modeBy := s.tagMode(kind, body.Mode, body.Text)
 
+	// Claim arbitration (#5, Epic C): first claim wins unless the referent is a
+	// conspiracy, which expects multiple claims.
+	if kind == "claim" && body.RefersTo != "" {
+		if origin, found := s.msgs.ByMsgID(body.RefersTo); found && origin.Mode != "conspiracy" {
+			if owner, claimed := s.msgs.FirstClaim(origin.NestID, origin.MsgID()); claimed {
+				httpError(w, http.StatusConflict, origin.MsgID()+" is claimed by "+owner+"; review it instead of redoing it.")
+				return
+			}
+		}
+	}
+
 	msg := Message{
 		NestID:     nestID,
 		Kind:       kind,

nestlog.go

@@ -119,6 +119,19 @@ func (s *MessageStore) ByMsgID(msgID string) (Message, bool) {
 	return Message{}, false
 }
 
+// FirstClaim returns the author of the first claim against a message, and
+// whether any claim exists.
+func (s *MessageStore) FirstClaim(nestID, referentID string) (string, bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for _, m := range s.log[nestID] {
+		if m.Kind == "claim" && m.RefersTo == referentID {
+			return m.Author, true
+		}
+	}
+	return "", false
+}
+
 func (s *MessageStore) save(nestID string) error {
 	if err := os.MkdirAll(s.dir, 0o755); err != nil {
 		return err