1 files changed, 55 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/api/ViatraQueryModelUpdateListener.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/api/ViatraQueryModelUpdateListener.java
new file mode 100644
index 00000000..da8bf87e
--- /dev/null
+++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/api/ViatraQueryModelUpdateListener.java
@@ -0,0 +1,55 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2013, Abel Hegedus, Istvan Rath and Daniel Varro
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.api;
+
+
+
+/**
+ * Listener interface for model changes affecting different levels of the VIATRA Query architecture.
+ * 
+ * @author Abel Hegedus
+ *
+ */
+public interface ViatraQueryModelUpdateListener {
+
+    /** 
+     * Possible notification levels for changes
+     * 
+     * @author Abel Hegedus
+     *
+     */
+    enum ChangeLevel {
+        NO_CHANGE, MODEL, INDEX, MATCHSET;
+        
+        public ChangeLevel changeOccured(ChangeLevel occuredLevel) {
+            if(this.compareTo(occuredLevel) < 0) {
+                return occuredLevel;
+            } else {
+                return this;
+            }
+        }
+    }
+    /**
+     * Called after each change with also sending the level of change.
+     * Only called if the change level is at least at the level returned by getLevel().
+     * 
+     * @param changeLevel
+     */
+    void notifyChanged(ChangeLevel changeLevel);
+    
+    /**
+     * This may be queried only ONCE (!!!) at the registration of the listener.
+     * 
+     * NOTE: this allows us to only create engine level change providers if there is someone who needs it.
+     * 
+     * @return the change level where you want notifications
+     */
+    ChangeLevel getLevel();
+    
+}