vetoable events

core/src/main/groovy/com/muwire/core/Event.groovy

@@ -7,6 +7,7 @@ class Event {
     private static final AtomicLong SEQ_NO = new AtomicLong();
     final long seqNo
     final long timestamp
+    boolean vetoed
 
     Event() {
         seqNo = SEQ_NO.getAndIncrement()

core/src/main/groovy/com/muwire/core/EventBus.groovy

@@ -31,9 +31,11 @@ class EventBus {
         synchronized(this) {
             currentHandlers = handlers.getOrDefault(clazz, [])
         }
-        currentHandlers.each {
+        for(def handler : currentHandlers) {
+            if (e.vetoed)
+                break
             try {
-                it."on${clazz.getSimpleName()}"(e)
+                handler."on${clazz.getSimpleName()}"(e)
             } catch (Exception bad) {
                 log.log(Level.SEVERE, "exception dispatching event",bad)
             }