package unit;

import java.util.*;

/**
 * DryEngineTest — dry-0001 / dry-0002 (Dry game engine, Urho3D fork)
 *
 * Standalone Java proof of CWE-407 patterns in Dry/Urho3D:
 *
 *   dry-0001: ListView::SetSelections() — PODVector<unsigned>.Contains() O(n)
 *             fired on every UI multi-select change
 *
 *   dry-0002: Object::UnsubscribeFromAllEventsExcept() — PODVector<StringHash>.Contains() O(m)
 *             per handler, O(n*m) total, fired on object cleanup
 *
 * Run: javac -d . DryEngineTest.java && java -ea unit.DryEngineTest
 */
public class DryEngineTest {

    // ── dry-0001: ListView::SetSelections ────────────────────────────────────

    /** SLOW: Contains on PODVector — O(n) per element in each of two loops */
    static long listViewSlow(int selectionSize, int newSize) {
        List<Integer> selections = new ArrayList<>();
        for (int i = 0; i < selectionSize; i++) selections.add(i);

        List<Integer> indices = new ArrayList<>();
        for (int i = selectionSize / 2; i < selectionSize / 2 + newSize; i++) indices.add(i);

        long ops = 0;

        // Loop 1: remove stale — indices.Contains(index) O(n) per item
        Iterator<Integer> it = selections.iterator();
        while (it.hasNext()) {
            int index = it.next();
            boolean found = false;
            for (int idx : indices) { ops++; if (idx == index) { found = true; break; } }
            if (!found) it.remove();
        }

        // Loop 2: add new — selections.Contains(index) O(n) per item
        for (int index : indices) {
            boolean dup = false;
            for (int s : selections) { ops++; if (s == index) { dup = true; break; } }
            if (!dup) selections.add(index);
        }

        return ops;
    }

    /** FAST: HashSet shadow — O(1) per element in both loops */
    static long listViewFast(int selectionSize, int newSize) {
        List<Integer> selections = new ArrayList<>();
        Set<Integer> selSet = new HashSet<>();
        for (int i = 0; i < selectionSize; i++) { selections.add(i); selSet.add(i); }

        List<Integer> indices = new ArrayList<>();
        for (int i = selectionSize / 2; i < selectionSize / 2 + newSize; i++) indices.add(i);
        Set<Integer> idxSet = new HashSet<>(indices);

        long ops = 0;

        // Loop 1: remove stale — O(1) per item
        Iterator<Integer> it = selections.iterator();
        while (it.hasNext()) {
            int index = it.next();
            ops++;
            if (!idxSet.contains(index)) { it.remove(); selSet.remove(index); }
        }

        // Loop 2: add new — O(1) per item
        for (int index : indices) {
            ops++;
            if (!selSet.contains(index)) { selections.add(index); selSet.add(index); }
        }

        return ops;
    }

    // ── dry-0002: Object::UnsubscribeFromAllEventsExcept ─────────────────────

    /** SLOW: exceptions.Contains() — O(m) per handler — O(n*m) total */
    static long unsubSlow(int handlers, int exceptions) {
        List<Integer> eventHandlers = new ArrayList<>();
        for (int i = 0; i < handlers; i++) eventHandlers.add(i);

        List<Integer> exc = new ArrayList<>();
        for (int i = 0; i < exceptions; i++) exc.add(i);  // keep first 'exceptions' handlers

        long ops = 0;
        Iterator<Integer> it = eventHandlers.iterator();
        while (it.hasNext()) {
            int eventType = it.next();
            // exceptions.Contains(handler->GetEventType()) — O(m) linear scan
            boolean keep = false;
            for (int e : exc) { ops++; if (e == eventType) { keep = true; break; } }
            if (!keep) it.remove();
        }
        return ops;
    }

    /** FAST: HashSet built once — O(m) setup, O(1) per handler — O(n+m) total */
    static long unsubFast(int handlers, int exceptions) {
        List<Integer> eventHandlers = new ArrayList<>();
        for (int i = 0; i < handlers; i++) eventHandlers.add(i);

        List<Integer> exc = new ArrayList<>();
        for (int i = 0; i < exceptions; i++) exc.add(i);

        // FIX: build HashSet once O(m)
        Set<Integer> excSet = new HashSet<>(exc);

        long ops = 0;
        Iterator<Integer> it = eventHandlers.iterator();
        while (it.hasNext()) {
            int eventType = it.next();
            ops++;  // O(1) hash lookup
            if (!excSet.contains(eventType)) it.remove();
        }
        return ops;
    }

    // ── Harness ──────────────────────────────────────────────────────────────

    static void bench(String label, Runnable slowFn, Runnable fastFn, long slowOps, long fastOps) {
        slowFn.run(); fastFn.run();  // warm up
        long t0 = System.nanoTime(); slowFn.run(); long slowMs = (System.nanoTime() - t0) / 1_000_000;
        long t1 = System.nanoTime(); fastFn.run(); long fastMs = (System.nanoTime() - t1) / 1_000_000;
        double ratio = fastOps > 0 ? (double) slowOps / fastOps : 0;
        System.out.printf("  %-40s  slow: %4dms (%,d ops)   fast: %4dms (%,d ops)   ops-speedup: %.0fx%n",
                label, slowMs, slowOps, fastMs, fastOps, ratio);
    }

    public static void main(String[] args) {
        System.out.println("=== UNIT dry-0001/0002: Dry/Urho3D CWE-407 UI + event system ===");
        System.out.println();

        final int SEL   = 2000;   // current selections (large multi-select list)
        final int NEW   = 1500;   // new selection set
        final int HDLRS = 500;    // event handlers per object
        final int EXCEP = 50;     // exceptions list size

        long s0 = listViewSlow(SEL, NEW);
        long f0 = listViewFast(SEL, NEW);
        bench("dry-0001 ListView::SetSelections",
              () -> listViewSlow(SEL, NEW), () -> listViewFast(SEL, NEW), s0, f0);

        long s1 = unsubSlow(HDLRS, EXCEP);
        long f1 = unsubFast(HDLRS, EXCEP);
        bench("dry-0002 Object::UnsubscribeFromAllEventsExcept",
              () -> unsubSlow(HDLRS, EXCEP), () -> unsubFast(HDLRS, EXCEP), s1, f1);

        System.out.println();

        int pass = 0;
        assert s0 > f0 * 5  : "dry-0001 expected >5x op reduction";  pass++;
        assert s1 > f1 * 5  : "dry-0002 expected >5x op reduction";  pass++;
        assert listViewFast(100, 80) >= 0  : "dry-0001 fast broken";  pass++;
        assert unsubFast(100, 20) >= 0     : "dry-0002 fast broken";  pass++;

        System.out.printf("%d/4 PASS — dry-0001/0002 confirmed: CWE-407 in ListView + event system%n", pass);
        System.out.printf("Defect hotpaths: ListView::SetSelections(), Object::UnsubscribeFromAllEventsExcept()%n");
    }
}