start implementing expression balancer

src/test/java/parser/ast/ExpressionBalancerTest.java

@@ -0,0 +1,106 @@
+package parser.ast;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ExpressionBalancerTest {
+
+    //EXPR
+    //├── EXPR: SUB
+    //|   └── INTEGER_LIT: 2
+    //└── INTEGER_LIT: 1
+    private static AST tree1() {
+        AST tree = new AST(new Node("EXPR"));
+
+        Node right = new Node("INTEGER_LIT");
+        right.setValue("1");
+
+        Node left = new Node("EXPR");
+        left.setValue("SUB");
+
+        Node lleft = new Node("INTEGER_LIT");
+        lleft.setValue("2");
+        left.setChildren(lleft);
+
+        tree.getRoot().setChildren(left, right);
+
+        return tree;
+    }
+
+    private static AST tree2() {
+        AST tree = new AST(new Node("EXPR"));
+
+        Node right = new Node("INTEGER_LIT");
+        right.setValue("1");
+
+        Node left = new Node("EXPR");
+        left.setValue("SUB");
+
+        Node lleft = new Node("EXPR");
+        lleft.setValue("SUB");
+
+        Node lright = new Node("INTEGER_LIT");
+        lright.setValue("2");
+
+        Node llleft = new Node("INTEGER_LIT");
+        llleft.setValue("3");
+
+        lleft.setChildren(llleft);
+        left.setChildren(lleft, lright);
+
+        tree.getRoot().setChildren(left, right);
+
+        return tree;
+    }
+
+    @Test
+    void testTree1Flip() {
+        AST tree = tree1();
+        System.out.println("Before:\n" + tree);
+
+        ExpressionBalancer.flip(tree);
+        System.out.println("After:\n" + tree);
+
+        assertThat(tree.getRoot().getChildren().get(0).getName()).isEqualTo("INTEGER_LIT");
+        assertThat(tree.getRoot().getChildren().get(1).getName()).isEqualTo("EXPR");
+    }
+
+    @Test
+    void testTree2Flip() {
+        AST tree = tree2();
+        System.out.println("Before:\n" + tree);
+
+        ExpressionBalancer.flip(tree);
+        System.out.println("After:\n" + tree);
+
+        assertThat(tree.getRoot().getChildren().get(0).getName()).isEqualTo("INTEGER_LIT");
+        assertThat(tree.getRoot().getChildren().get(1).getName()).isEqualTo("EXPR");
+        assertThat(tree.getRoot().getChildren().get(1).getChildren().get(0).getName()).isEqualTo("INTEGER_LIT");
+        assertThat(tree.getRoot().getChildren().get(1).getChildren().get(1).getName()).isEqualTo("EXPR");
+    }
+
+    @Test
+    void testTree1Rotate() {
+        AST tree = tree1();
+        ExpressionBalancer.flip(tree);
+        System.out.println("Before:\n" + tree);
+
+        ExpressionBalancer.leftPrecedence(tree);
+        System.out.println("After:\n" + tree);
+
+        assertThat(tree.size()).isEqualTo(3);
+    }
+
+    @Test
+    void testTree2Rotate() {
+        AST tree = tree2();
+        ExpressionBalancer.flip(tree);
+        System.out.println("Before:\n" + tree);
+
+        ExpressionBalancer.leftPrecedence(tree);
+        System.out.println("After:\n" + tree);
+
+        assertThat(tree.size()).isEqualTo(5);
+    }
+}