package unit;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

/**
 * Gstreamer0003TracerDeduplicateTest — CWE-407 gstreamer-0003
 *
 * Models gst_tracing_get_active_tracers() in gst/gsttracerutils.c:
 *   slow() = O(H × T²) via list-indexOf dedup (current defect)
 *   fast() = O(H × T) via HashSet dedup (patch)
 *
 * Parameters: H hook types, T tracers registered per hook (with overlap).
 * Assert: slowOps > fastOps * Nx at H=54 hooks, T=5 tracers each covering 10 hooks.
 */
public class Gstreamer0003TracerDeduplicateTest {

    static long slowOps;
    static long fastOps;

    /**
     * Simulates the tracer seen-list: a List<Integer> (tracer ids).
     * g_list_index equivalent = list.indexOf() = O(n).
     */
    static int listIndexOf(List<Integer> list, int val) {
        for (int i = 0; i < list.size(); i++) {
            slowOps++;
            if (list.get(i) == val) return i;
        }
        return -1;
    }

    /**
     * slow: O(H × T²) — models original gst_tracing_get_active_tracers.
     * For each hook bucket, for each tracer-hook entry, calls listIndexOf.
     */
    static List<Integer> getActiveTracersSlow(int[][] hookBuckets) {
        List<Integer> tracers = new ArrayList<>();
        for (int[] bucket : hookBuckets) {
            for (int tracerId : bucket) {
                if (listIndexOf(tracers, tracerId) < 0) {
                    tracers.add(tracerId);
                }
            }
        }
        return tracers;
    }

    /**
     * fast: O(H × T) — models HashSet fix.
     * Uses O(1) set membership test.
     */
    static List<Integer> getActiveTracersFast(int[][] hookBuckets) {
        List<Integer> tracers = new ArrayList<>();
        Set<Integer> seen = new HashSet<>();
        for (int[] bucket : hookBuckets) {
            for (int tracerId : bucket) {
                fastOps++;
                if (!seen.contains(tracerId)) {
                    seen.add(tracerId);
                    tracers.add(tracerId);
                }
            }
        }
        return tracers;
    }

    public static void main(String[] args) {
        final int NX = 5;

        // H=54 hook types; T=5 tracers, each registered under ~10 of 54 hooks
        final int H = 54;
        final int T = 5;   // distinct tracers
        final int HOOKS_PER_TRACER = 10;

        // Build hookBuckets: H buckets, each containing tracers registered for that hook
        int[][] hookBuckets = new int[H][];
        int[] hookCounts = new int[H];
        // Assign each tracer to HOOKS_PER_TRACER hooks
        int[][] tracerHooks = new int[T][];
        for (int t = 0; t < T; t++) {
            tracerHooks[t] = new int[HOOKS_PER_TRACER];
            for (int h = 0; h < HOOKS_PER_TRACER; h++) {
                tracerHooks[t][h] = (t * HOOKS_PER_TRACER + h) % H;
            }
        }
        // Count tracer registrations per hook
        int[] buckSize = new int[H];
        for (int t = 0; t < T; t++) {
            for (int h : tracerHooks[t]) buckSize[h]++;
        }
        hookBuckets = new int[H][];
        for (int h = 0; h < H; h++) hookBuckets[h] = new int[buckSize[h]];
        int[] buckIdx = new int[H];
        for (int t = 0; t < T; t++) {
            for (int h : tracerHooks[t]) {
                hookBuckets[h][buckIdx[h]++] = t;
            }
        }

        // Warm up
        slowOps = 0; fastOps = 0;
        getActiveTracersSlow(hookBuckets);
        getActiveTracersFast(hookBuckets);

        // Measure
        slowOps = 0; fastOps = 0;
        final int CALLS = 1000;
        List<Integer> slowResult = null, fastResult = null;
        for (int c = 0; c < CALLS; c++) {
            slowResult = getActiveTracersSlow(hookBuckets);
            fastResult = getActiveTracersFast(hookBuckets);
        }

        // Correctness: both should find T unique tracers
        boolean correctnessOk = (slowResult != null && fastResult != null &&
                                  slowResult.size() == T && fastResult.size() == T);
        boolean speedupOk = slowOps > fastOps * NX;

        System.out.printf("H=%d hooks, T=%d tracers, %d hooks/tracer, CALLS=%d%n",
                          H, T, HOOKS_PER_TRACER, CALLS);
        System.out.printf("slow (list-indexOf) ops: %d%n", slowOps);
        System.out.printf("fast (HashSet)      ops: %d%n", fastOps);
        System.out.printf("speedup ratio: %.1fx (required >%dx)%n",
            (double) slowOps / fastOps, NX);
        System.out.printf("tracers found: slow=%d fast=%d (expected %d)%n",
            slowResult == null ? -1 : slowResult.size(),
            fastResult == null ? -1 : fastResult.size(), T);

        int passed = 0, total = 2;
        if (correctnessOk) {
            System.out.printf("1/2 PASS correctness: both found %d tracers%n", T);
            passed++;
        } else {
            System.out.printf("1/2 FAIL correctness: slow=%d fast=%d expected=%d%n",
                slowResult == null ? -1 : slowResult.size(),
                fastResult == null ? -1 : fastResult.size(), T);
        }
        if (speedupOk) {
            System.out.printf("2/2 PASS speedup: %d > %d * %d%n", slowOps, fastOps, NX);
            passed++;
        } else {
            System.out.printf("2/2 FAIL speedup: %d not > %d * %d%n", slowOps, fastOps, NX);
        }

        System.out.printf("%d/%d PASS%n", passed, total);
        if (passed < total) System.exit(1);
    }
}