Added and tested the main 'build()' method for difference tree builder

src/main/java/org/cqfn/astranaut/core/algorithms/DifferenceTreeBuilder.java

@@ -27,6 +27,8 @@
 import java.util.Map;
 import org.cqfn.astranaut.core.DifferenceNode;
 import org.cqfn.astranaut.core.Node;
+import org.cqfn.astranaut.core.algorithms.mapping.Mapper;
+import org.cqfn.astranaut.core.algorithms.mapping.Mapping;
 
 /**
  * Builder of difference syntax tree, that is, one that stores changes between two trees.
@@ -48,13 +50,28 @@ public final class DifferenceTreeBuilder {
 
     /**
      * Constructor.
-     * @param prototype Root node of an 'ordinary', non-difference original tree before the changes
+     * @param before Root node of an 'ordinary', non-difference original tree before the changes
      */
-    public DifferenceTreeBuilder(final Node prototype) {
-        this.root = new DifferenceNode(prototype);
+    public DifferenceTreeBuilder(final Node before) {
+        this.root = new DifferenceNode(before);
         this.parents = DifferenceTreeBuilder.buildParentsMap(this.root);
     }
 
+    /**
+     * Builds a difference tree based on the original tree and the tree after changes.
+     * @param after Root node of tree before the changes
+     * @param mapper A mapper used for node mappings
+     * @return Result of operation, {@code true} if difference tree was built
+     */
+    public boolean build(final Node after, final Mapper mapper) {
+        final Mapping mapping = mapper.map(this.root.getPrototype(), after);
+        boolean result = true;
+        for (final Node deleted : mapping.getDeleted()) {
+            result = result & this.deleteNode(deleted);
+        }
+        return result;
+    }
+
     /**
      * Returns root of resulting difference tree.
      * @return Root node of difference tree

src/test/java/org/cqfn/astranaut/core/algorithms/DifferenceTreeBuilderTest.java

@@ -0,0 +1,55 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2024 Ivan Kniazkov
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cqfn.astranaut.core.algorithms;
+
+import org.cqfn.astranaut.core.DifferenceNode;
+import org.cqfn.astranaut.core.Node;
+import org.cqfn.astranaut.core.algorithms.mapping.BottomUpMapper;
+import org.cqfn.astranaut.core.example.LittleTrees;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Testing {@link DifferenceTreeBuilder} class.
+ *
+ * @since 1.1.0
+ */
+class DifferenceTreeBuilderTest {
+    /**
+     * Testing the construction of a difference tree with a deleted node.
+     */
+    @Test
+    void testTreeWithDeletedNode() {
+        final Node before = LittleTrees.createStatementListWithThreeChildren();
+        final Node after = LittleTrees.createStatementListWithTwoChildren();
+        final DifferenceTreeBuilder builder = new DifferenceTreeBuilder(before);
+        final boolean result = builder.build(after, new BottomUpMapper());
+        Assertions.assertTrue(result);
+        final DifferenceNode diff = builder.getRoot();
+        final Node expected = LittleTrees.createTreeWithDeleteAction();
+        Assertions.assertTrue(expected.deepCompare(diff));
+        Assertions.assertTrue(before.deepCompare(diff.getBefore()));
+        Assertions.assertTrue(after.deepCompare(diff.getAfter()));
+    }
+}