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Projekte/jme-common/src/main/java/pp/view/ModelViewSynchronizer.java

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+////////////////////////////////////////
+// Programming project code
+// UniBw M, 2022, 2023, 2024
+// www.unibw.de/inf2
+// (c) Mark Minas (mark.minas@unibw.de)
+////////////////////////////////////////
+
+package pp.view;
+
+import com.jme3.scene.Node;
+import com.jme3.scene.Spatial;
+
+import java.lang.System.Logger;
+import java.lang.System.Logger.Level;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Abstract base class for keeping the scene graph (=view) in sync with the model.
+ */
+public abstract class ModelViewSynchronizer<I> {
+    private static final Logger LOGGER = System.getLogger(ModelViewSynchronizer.class.getName());
+    private final Node itemNode = new Node("items"); //NON-NLS
+    private final Map<I, Spatial> itemMap = new HashMap<>();
+
+    /**
+     * Saves the game state and the node.
+     *
+     * @param root particular node
+     */
+    protected ModelViewSynchronizer(Node root) {
+        root.attachChild(itemNode);
+    }
+
+    /**
+     * Returns the spatial representing the specified item,
+     * or null if the item has no view counterpart.
+     */
+    public Spatial getSpatial(I item) {
+        return itemMap.get(item);
+    }
+
+    /**
+     * removes spatial from map
+     *
+     * @param item spatial that should be removed
+     */
+    public void delete(I item) {
+        final Spatial spatial = itemMap.remove(item);
+        if (spatial != null) {
+            spatial.removeFromParent();
+            LOGGER.log(Level.DEBUG, "removed spatial for {0} in {1}", item, this); //NON-NLS
+        }
+    }
+
+    /**
+     * add spatial to map
+     *
+     * @param item spatial that schuld be added
+     */
+    public void add(I item) {
+        if (itemMap.containsKey(item)) {
+            LOGGER.log(Level.WARNING, "Item {0} already managed by {1}", item, this); //NON-NLS
+            return;
+        }
+        final Spatial spatial = translate(item);
+        itemMap.put(item, spatial);
+        LOGGER.log(Level.DEBUG, "added spatial for {0} in {1}", item, this); //NON-NLS
+        if (spatial != null)
+            itemNode.attachChild(spatial);
+    }
+
+    /**
+     * Removed every item
+     */
+    public void clear() {
+        LOGGER.log(Level.DEBUG, "clear"); //NON-NLS
+        itemMap.clear();
+        itemNode.detachAllChildren();
+    }
+
+    /**
+     * Creates the spatial for the specified item. Implementations may decide to return null. This
+     * means that the item shall not be represented in the scene graph.
+     *
+     * @param item the item whose representing spatial is asked for
+     * @return the spatial of the item, or null if the item shall not be represented by a spatial.
+     */
+    protected abstract Spatial translate(I item);
+}