java-topology/defects/pulsar/unit/PulsarJavaInstanceRunnableTest.java

package unit;

import java.util.*;

/**
 * pulsar-0002: JavaInstanceRunnable.setupConfig() — List.contains() in config key validation loop.
 *
 * allFields is a List<String> from BeanPropertiesReader.getBeanProperties().
 * For each config key, .contains() is O(F). With K keys, total is O(K * F).
 * Fix: convert allFields to HashSet<String> before the loop.
 */
public class PulsarJavaInstanceRunnableTest {

    // Slow path: List<String> allFields with .contains() per key
    static Object[] slowValidateConfig(List<String> allFields, Set<String> configKeys) {
        long ops = 0;
        List<String> invalidKeys = new ArrayList<>();
        for (String s : configKeys) {
            // allFields.contains(s): O(F) linear scan
            boolean found = false;
            for (String f : allFields) {
                ops++;
                if (f.equals(s)) { found = true; break; }
            }
            if (!found) {
                invalidKeys.add(s);
            }
        }
        return new Object[]{invalidKeys, ops};
    }

    // Fast path: HashSet<String> for O(1) lookup
    static Object[] fastValidateConfig(List<String> allFields, Set<String> configKeys) {
        Set<String> fieldSet = new HashSet<>(allFields);
        long ops = 0;
        List<String> invalidKeys = new ArrayList<>();
        for (String s : configKeys) {
            ops++; // O(1) HashSet.contains
            if (!fieldSet.contains(s)) {
                invalidKeys.add(s);
            }
        }
        return new Object[]{invalidKeys, ops};
    }

    public static void main(String[] args) {
        int passed = 0;
        int total = 0;

        // Test 1: correctness — no invalid keys
        {
            total++;
            List<String> allFields = Arrays.asList("host", "port", "timeout", "retries", "user");
            Set<String> configKeys = new HashSet<>(Arrays.asList("host", "port", "timeout"));

            @SuppressWarnings("unchecked")
            List<String> slowInvalid = (List<String>) slowValidateConfig(allFields, configKeys)[0];
            @SuppressWarnings("unchecked")
            List<String> fastInvalid = (List<String>) fastValidateConfig(allFields, configKeys)[0];

            assert slowInvalid.isEmpty() : "No invalid keys expected, slow found: " + slowInvalid;
            assert fastInvalid.isEmpty() : "No invalid keys expected, fast found: " + fastInvalid;
            System.out.println("  Test 1 PASS: no invalid keys");
            passed++;
        }

        // Test 2: correctness — some invalid keys
        {
            total++;
            List<String> allFields = Arrays.asList("host", "port", "timeout");
            Set<String> configKeys = new HashSet<>(Arrays.asList("host", "port", "badKey", "anotherBad"));

            @SuppressWarnings("unchecked")
            List<String> slowInvalid = (List<String>) slowValidateConfig(allFields, configKeys)[0];
            @SuppressWarnings("unchecked")
            List<String> fastInvalid = (List<String>) fastValidateConfig(allFields, configKeys)[0];

            Set<String> slowSet = new HashSet<>(slowInvalid);
            Set<String> fastSet = new HashSet<>(fastInvalid);

            assert slowSet.equals(fastSet)
                : "Slow and fast must find same invalid keys. slow=" + slowSet + " fast=" + fastSet;
            assert slowSet.contains("badKey") : "badKey must be invalid";
            assert slowSet.contains("anotherBad") : "anotherBad must be invalid";
            assert !slowSet.contains("host") : "host is valid, must not be invalid";
            System.out.println("  Test 2 PASS: invalid keys=" + slowSet);
            passed++;
        }

        // Test 3: op count — slow O(K*F) vs fast O(K)
        {
            total++;
            int F = 150; // fields in config class
            int K = 100; // config keys

            List<String> allFields = new ArrayList<>();
            for (int i = 0; i < F; i++) allFields.add("field" + i);

            // Config keys: half valid, half invalid
            Set<String> configKeys = new HashSet<>();
            for (int i = 0; i < K / 2; i++) configKeys.add("field" + i);         // valid
            for (int i = 0; i < K / 2; i++) configKeys.add("unknown-key-" + i);  // invalid

            Object[] slowOut = slowValidateConfig(allFields, configKeys);
            Object[] fastOut = fastValidateConfig(allFields, configKeys);

            @SuppressWarnings("unchecked")
            Set<String> slowInvalidSet = new HashSet<>((List<String>) slowOut[0]);
            @SuppressWarnings("unchecked")
            Set<String> fastInvalidSet = new HashSet<>((List<String>) fastOut[0]);

            assert slowInvalidSet.equals(fastInvalidSet)
                : "Slow and fast must agree on invalid keys";

            long slowOps = (Long) slowOut[1];
            long fastOps = (Long) fastOut[1];

            assert slowOps > fastOps
                : "Slow must do more ops: slowOps=" + slowOps + " fastOps=" + fastOps;
            assert fastOps == K
                : "Fast must make exactly K=" + K + " ops, got " + fastOps;

            long speedup = slowOps / fastOps;
            System.out.println("  Test 3 PASS: slowOps=" + slowOps + " fastOps=" + fastOps
                + " speedup=" + speedup + "x (F=" + F + " K=" + K + ")");
            passed++;
        }

        // Test 4: worst-case O(K*F) — all config keys invalid (scan all F every time)
        {
            total++;
            int F = 100;
            int K = 80;
            List<String> allFields = new ArrayList<>();
            for (int i = 0; i < F; i++) allFields.add("field" + i);

            Set<String> configKeys = new HashSet<>();
            for (int i = 0; i < K; i++) configKeys.add("invalid-key-" + i);

            long expectedSlowOps = (long) K * F; // every key scans all F fields
            long actualSlowOps = 0;
            for (String key : configKeys) {
                for (String f : allFields) {
                    actualSlowOps++;
                    if (f.equals(key)) break;
                }
            }

            assert actualSlowOps == expectedSlowOps
                : "Expected " + expectedSlowOps + " ops (K*F), got " + actualSlowOps;

            long fastOps = K;
            long speedup = actualSlowOps / fastOps;

            assert speedup == F : "Speedup should equal F=" + F + ", got " + speedup;
            System.out.println("  Test 4 PASS: O(K*F)=" + actualSlowOps + " vs O(K)=" + fastOps
                + " speedup=" + speedup + "x");
            passed++;
        }

        System.out.println(passed + "/" + total + " PASS");
        if (passed != total) System.exit(1);
    }
}