java-topology/defects/element-web/unit/ElementWebTest.java

package unit;
import java.util.*;

/**
 * ElementWebTest — CWE-407 benchmark for element-web-0001
 *
 * element-web-0001: apps/web/src/TextForEvent.tsx:503
 *   textForPowerEvent() deduplicates user IDs from power level event using indexOf on an array.
 *   Two forEach loops each calling indexOf (O(n)) to build a dedup list — total O(N²).
 *
 *   Slow: for each userId in contentUsers ∪ prevContentUsers: indexOf on accumulator array
 *   Fast: Set union in O(N)
 *
 * compile: javac -d . ElementWebTest.java && java -ea unit.ElementWebTest
 */
public class ElementWebTest {

    static void bench(String label, Runnable slow, Runnable fast, long sOps, long fOps) {
        slow.run(); fast.run(); // warmup
        long t0 = System.nanoTime(); slow.run(); long sMs = (System.nanoTime() - t0) / 1_000_000;
        long t1 = System.nanoTime(); fast.run(); long fMs = (System.nanoTime() - t1) / 1_000_000;
        double ratio = fOps > 0 ? (double) sOps / fOps : 0;
        System.out.printf("  %-60s  slow:%4dms (%,d ops)  fast:%4dms (%,d ops)  speedup:%.0fx%n",
                label, sMs, sOps, fMs, fOps, ratio);
    }

    // -----------------------------------------------------------------------
    // element-web-0001: users.indexOf dedup in forEach loop
    // -----------------------------------------------------------------------

    /**
     * Slow: Array.indexOf inside forEach — O((A+B)²)
     * Simulates building a dedup list from two sets of user IDs.
     * Returns total comparison operations performed.
     */
    static long slowPowerEventDedup(int contentUsers, int prevContentUsers) {
        List<String> contentKeys = new ArrayList<>();
        for (int i = 0; i < contentUsers; i++) contentKeys.add("user-" + i);

        // prevContent has some overlap + some new users
        List<String> prevKeys = new ArrayList<>();
        for (int i = contentUsers / 2; i < contentUsers / 2 + prevContentUsers; i++)
            prevKeys.add("user-" + i);

        List<String> users = new ArrayList<>();
        long ops = 0;

        // forEach(userId => if (users.indexOf(userId) === -1) users.push(userId))
        for (String userId : contentKeys) {
            ops += users.size(); // cost of indexOf scan (grows as list fills)
            if (!users.contains(userId)) users.add(userId);
        }
        for (String userId : prevKeys) {
            ops += users.size(); // cost of indexOf scan
            if (!users.contains(userId)) users.add(userId);
        }
        return ops;
    }

    /**
     * Fast: Set union — O(A + B)
     * Returns total operations (one per element).
     */
    static long fastPowerEventDedup(int contentUsers, int prevContentUsers) {
        List<String> contentKeys = new ArrayList<>();
        for (int i = 0; i < contentUsers; i++) contentKeys.add("user-" + i);

        List<String> prevKeys = new ArrayList<>();
        for (int i = contentUsers / 2; i < contentUsers / 2 + prevContentUsers; i++)
            prevKeys.add("user-" + i);

        long ops = 0;
        Set<String> userSet = new LinkedHashSet<>();
        for (String u : contentKeys) { userSet.add(u); ops++; }
        for (String u : prevKeys) { userSet.add(u); ops++; }
        // Array.from(userSet) — O(N)
        List<String> users = new ArrayList<>(userSet);
        ops += users.size();
        return ops;
    }

    public static void main(String[] args) {
        System.out.println("ElementWebTest — CWE-407 benchmarks");
        System.out.println();

        int passed = 0;
        int total = 0;

        // Small room (N=200 each side)
        {
            int A = 200, B = 200;
            long[] sOps = {0}, fOps = {0};
            Runnable s = () -> sOps[0] = slowPowerEventDedup(A, B);
            Runnable f = () -> fOps[0] = fastPowerEventDedup(A, B);
            sOps[0] = slowPowerEventDedup(A, B);
            fOps[0] = fastPowerEventDedup(A, B);
            bench("element-web-0001 power event dedup indexOf vs Set (A=" + A + " B=" + B + ")", s, f, sOps[0], fOps[0]);
            total++;
            if (sOps[0] > fOps[0] * 10L) {
                System.out.println("  element-web-0001 small PASS (slow=" + sOps[0] + " > 10x fast=" + fOps[0] + ")");
                passed++;
            } else {
                System.out.println("  element-web-0001 small FAIL (slow=" + sOps[0] + " fast=" + fOps[0] + ")");
            }
            assert sOps[0] > fOps[0] * 10L : "element-web-0001 small: slow ops not 10x fast ops";
        }

        // Large room (N=1000 each side — large server with many power level entries)
        {
            int A = 1000, B = 1000;
            long[] sOps = {0}, fOps = {0};
            Runnable s = () -> sOps[0] = slowPowerEventDedup(A, B);
            Runnable f = () -> fOps[0] = fastPowerEventDedup(A, B);
            sOps[0] = slowPowerEventDedup(A, B);
            fOps[0] = fastPowerEventDedup(A, B);
            bench("element-web-0001 power event dedup indexOf vs Set (A=" + A + " B=" + B + ")", s, f, sOps[0], fOps[0]);
            total++;
            if (sOps[0] > fOps[0] * 50L) {
                System.out.println("  element-web-0001 large PASS (slow=" + sOps[0] + " > 50x fast=" + fOps[0] + ")");
                passed++;
            } else {
                System.out.println("  element-web-0001 large FAIL (slow=" + sOps[0] + " fast=" + fOps[0] + ")");
            }
            assert sOps[0] > fOps[0] * 50L : "element-web-0001 large: slow ops not 50x fast ops";
        }

        System.out.println();
        System.out.println(passed + "/" + total + " PASS");
    }
}