feat: HideSomeChanges

Author: pmbittner

src/main/java/org/variantsync/diffdetective/variation/diff/transform/HideSomeChanges.java

@@ -0,0 +1,52 @@
+package org.variantsync.diffdetective.variation.diff.transform;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Predicate;
+
+import org.variantsync.diffdetective.util.Assert;
+import org.variantsync.diffdetective.variation.Label;
+import org.variantsync.diffdetective.variation.diff.DiffNode;
+import org.variantsync.diffdetective.variation.diff.VariationDiff;
+
+/**
+ * This transformer prunes some changes in a variation diffs.
+ * The transformation requires a predicate on {@link DiffNode nodes} to identify the changes which should be undone.
+ * An inserted node will be removed, so that the insertion does not happen.
+ * A removed node will be made unchanged so that it will not be deleted.
+ * When a node is made unchanged, also its parent node will be made unchanged if necessary to retain diff consistency.
+ * @see DiffNode#makeUnchanged()
+ * @author Paul Bittner
+ */
+public class HideSomeChanges<L extends Label> implements Transformer<VariationDiff<L>> {
+    private Predicate<DiffNode<L>> isInteresting;
+
+    public HideSomeChanges(final Predicate<DiffNode<L>> isInteresting) {
+        Assert.assertNotNull(isInteresting);
+        this.isInteresting = isInteresting;
+    }
+
+    @Override
+    public void transform(VariationDiff<L> d) {
+        final List<DiffNode<L>> nodesToEliminate = new ArrayList<>();
+        final List<DiffNode<L>> toUnchanged = new ArrayList<>();
+        d.forAll((DiffNode<L> node) -> {
+                if (isInteresting.test(node)) {
+                    if (node.isAdd()) {
+                        nodesToEliminate.add(node);
+                    } else if (node.isRem()) {
+                        toUnchanged.add(node);
+                    }
+                }
+            });
+
+        for (DiffNode<L> zombie : nodesToEliminate) {
+            // We also drop all children.
+            zombie.drop();
+        }
+
+        for (DiffNode<L> n : toUnchanged) {
+            n.makeUnchanged();
+        }
+    }
+}