package unit;

import java.util.*;

/**
 * OvsTest — CWE-407 benchmark for ovs-0001
 *
 * Models dpif_offload_port_add() O(T×P) nested scan for provider name lookup
 * vs. O(1) HashMap-based provider registry.
 *
 * Real code (lib/dpif-offload.c:580-595):
 *   for (char *name = strtok_r(tokens, ",", &saveptr); ...)   // O(T) tokens
 *       LIST_FOR_EACH (offload, dpif_list_node, &collection->list)   // O(P)
 *           if (!strcmp(name, offload->class->type)) ...
 *
 * Also: provider_collection_add() O(P) duplicate scan (dpif-offload.c:229-234).
 *
 * Fix: HashMap<String, Provider> registry — O(1) name lookup.
 */
public class OvsTest {

    static void bench(String label, Runnable slow, Runnable fast, long sOps, long fOps) {
        slow.run(); fast.run();
        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 speedup = fMs > 0 ? (double) sMs / fMs : 0;
        System.out.printf("  %-54s  slow:%4dms (%,d ops)  fast:%4dms (%,d ops)  speedup:%.0fx%n",
                label, sMs, sOps, fMs, fOps, speedup);
    }

    // ---------- slow: nested linked list scan (the defect) ----------

    static long slowPortAdd(int T, int P, int ports) {
        String[] providers = new String[P];
        for (int p = 0; p < P; p++) providers[p] = "provider-" + p;

        // worst-case: all tokens match the LAST provider — full list scan each time
        String[] tokens = new String[T];
        for (int t = 0; t < T; t++) tokens[t] = providers[P - 1];

        long ops = 0;
        for (int port = 0; port < ports; port++) {
            for (String token : tokens) {          // O(T) per port
                for (String prov : providers) {    // O(P) per token — scans all P
                    ops++;
                    if (prov.equals(token)) break;
                }
            }
        }
        return ops;
    }

    // ---------- fast: HashMap lookup (the fix) ----------

    static long fastPortAdd(int T, int P, int ports) {
        Map<String, Integer> provMap = new HashMap<>(P * 2);
        for (int p = 0; p < P; p++) provMap.put("provider-" + p, p);

        String[] tokens = new String[T];
        for (int t = 0; t < T; t++) tokens[t] = "provider-" + (P - 1); // same worst-case target

        long ops = 0;
        for (int port = 0; port < ports; port++) {
            for (String token : tokens) {          // O(T) per port
                ops++;                             // O(1) map lookup
                provMap.get(token);
            }
        }
        return ops;
    }

    public static void main(String[] args) {
        System.out.println("OvsTest — ovs-0001: dpif_offload_port_add() provider linked-list scan → HashMap");
        System.out.println();

        System.out.println("  [dpif_offload_port_add — priority token × provider list nested scan]");
        int[][] cases = {{4, 8, 50000}, {8, 16, 20000}, {4, 32, 10000}};
        for (int[] c : cases) {
            int T = c[0], P = c[1], ports = c[2];
            bench(
                String.format("T=%d tokens, P=%d providers, %,d ports", T, P, ports),
                () -> slowPortAdd(T, P, ports),
                () -> fastPortAdd(T, P, ports),
                (long) T * P * ports,
                (long) T * ports
            );
        }

        System.out.println();
        System.out.println("Defect : lib/dpif-offload.c:580-595 — LIST_FOR_EACH provider strcmp O(P) per token");
        System.out.println("         lib/dpif-offload.c:229-234 — provider_collection_add() O(P) dup scan");
        System.out.println("Fix    : HashMap<name,provider> registry — O(1) lookup, O(1) dup detection");
        System.out.println("Ticket : ovs-0001-dpif-offload-port-add-linear-provider-scan.md");

        System.out.println();
        int pass = 0;
        long s0 = slowPortAdd(4, 32, 1000), f0 = fastPortAdd(4, 32, 1000);
        assert s0 > f0 * 5 : "ovs-0001 expected >5x; slow=" + s0 + " fast=" + f0; pass++;
        System.out.printf("%d/1 PASS — ovs-0001: CWE-407 in Open vSwitch offload provider dispatch%n", pass);
        System.out.printf("Hotpath: dpif_offload_port_add() called on every port-add in SR-IOV deployments%n");
    }
}