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package com.oracle.truffle.api.test.nodes;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import org.junit.Test;

import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.nodes.Node;
import com.oracle.truffle.api.nodes.RootNode;

Tests optional method for ensuring that a node replacement is type safe. Ordinary node
replacement is performed by unsafe assignment of a parent node's child field.
/**
 * Tests optional method for ensuring that a node replacement is type safe. Ordinary node
 * replacement is performed by unsafe assignment of a parent node's child field.
 */
public class SafeReplaceTest {

    @Test
    public void testCorrectReplacement() {
        TestRootNode root = new TestRootNode();
        final TestNode oldChild = new TestNode();
        final TestNode newChild = new TestNode();
        root.child = oldChild;
        assertFalse(oldChild.isSafelyReplaceableBy(newChild));  // No parent node
        root.adoptChildren();
        assertTrue(oldChild.isSafelyReplaceableBy(newChild));   // Now adopted by parent
        // new node
        oldChild.replace(newChild);
        root.execute(null);
        assertEquals(root.executed, 1);
        assertEquals(oldChild.executed, 0);
        assertEquals(newChild.executed, 1);
    }

    @Test
    public void testIncorrectReplacement() {
        TestRootNode root = new TestRootNode();
        final TestNode oldChild = new TestNode();
        root.child = oldChild;
        root.adoptChildren();
        final TestNode newChild = new TestNode();
        final TestNode strayChild = new TestNode();
        assertFalse(strayChild.isSafelyReplaceableBy(newChild)); // Stray not a child of parent
        final WrongTestNode wrongTypeNewChild = new WrongTestNode();
        assertFalse(oldChild.isSafelyReplaceableBy(wrongTypeNewChild));
    }

    private static class TestNode extends Node {

        private int executed;

        public Object execute() {
            executed++;
            return null;
        }
    }

    private static class TestRootNode extends RootNode {

        @Child TestNode child;

        private int executed;

        TestRootNode() {
            super(null);
        }

        @Override
        public Object execute(VirtualFrame frame) {
            executed++;
            child.execute();
            return null;
        }
    }

    private static class WrongTestNode extends Node {
    }

}