java-topology/defects/prometheus/unit/PrometheusTest.java

package unit;

import java.util.*;

/**
 * Standalone unit test for prometheus-0001: CWE-407.
 *
 * prometheus-0001: Builder.Labels() del-slice membership — O(n²)
 *   slow() uses a List<String> for the "deleted" set; contains() is O(D).
 *         For each of L base labels: O(D) del-check + O(A) add-check → O(L×(D+A)).
 *   fast() uses a HashSet<String> for both del and add; contains() is O(1).
 *         For each of L base labels: O(1) del-check + O(1) add-check → O(L).
 *   Assert: slowOps > fastOps * 10x for L=500 labels with D=250 deleted.
 */
public class PrometheusTest {

    /**
     * Slow path — Builder.Labels() with []string del-set: O(L * D) membership tests.
     */
    static long slowBuilderLabels(List<String> base, List<String> del, List<String> add) {
        long ops = 0;
        List<String> result = new ArrayList<>(base.size());
        for (String label : base) {
            // slices.Contains(del, label) — O(D) linear scan
            boolean inDel = false;
            for (String d : del) {
                ops++;
                if (d.equals(label)) { inDel = true; break; }
            }
            if (inDel) continue;

            // contains(add, label) — O(A) linear scan
            boolean inAdd = false;
            for (String a : add) {
                ops++;
                if (a.equals(label)) { inAdd = true; break; }
            }
            if (inAdd) continue;

            result.add(label);
        }
        return ops;
    }

    /**
     * Fast path — Builder.Labels() with map-based del/add sets: O(L) total.
     */
    static long fastBuilderLabels(List<String> base, List<String> del, List<String> add) {
        long ops = 0;
        // Build O(1) sets — cost O(D + A)
        Set<String> delSet = new HashSet<>(del);
        for (String ignored : del) ops++;
        Set<String> addSet = new HashSet<>(add);
        for (String ignored : add) ops++;

        List<String> result = new ArrayList<>(base.size());
        for (String label : base) {
            ops++; // single O(1) hash lookup
            if (delSet.contains(label)) continue;
            ops++;
            if (addSet.contains(label)) continue;
            result.add(label);
        }
        return ops;
    }

    static void testBuilderLabels() {
        int L = 500;   // base label count
        int D = 250;   // deleted label count (worst case: half of base)
        int A = 50;    // added label count

        List<String> base = new ArrayList<>(L);
        for (int i = 0; i < L; i++) base.add("label_" + i);

        List<String> del = new ArrayList<>(D);
        for (int i = 0; i < D; i++) del.add("label_" + i);  // delete first D

        List<String> add = new ArrayList<>(A);
        for (int i = 0; i < A; i++) add.add("new_label_" + i);

        long sOps = slowBuilderLabels(base, del, add);
        long fOps = fastBuilderLabels(base, del, add);

        int Nx = 10;
        boolean pass = sOps > fOps * Nx;
        System.out.printf("prometheus-0001 [L=%d D=%d A=%d]: slow=%d fast=%d ratio=%.1fx — %s%n",
                L, D, A, sOps, fOps, (double) sOps / fOps, pass ? "PASS" : "FAIL");
        if (!pass) throw new AssertionError("prometheus-0001 FAIL: slow=" + sOps + " fast=" + fOps);
    }

    public static void main(String[] args) {
        testBuilderLabels();
        System.out.println("1/1 PASS");
    }
}