package unit;

import java.util.*;

/**
 * VaultGroupMembershipAlgorithm — CWE-407 benchmark
 *
 * Models HashiCorp Vault identity_store_util.go sanitizeAndUpsertGroup():
 *   SLOW: strutil.StrListContains(memberGroupIDs, currentMemberGroupID) — O(G) per iteration
 *         called G times → O(G²) total
 *   FAST: pre-build map[string]bool from memberGroupIDs → O(1) per lookup
 *
 * vault-0001
 */
public class VaultGroupMembershipAlgorithm {

    // ------------------------------------------------------------------ nodes

    static class Node {
        String id;
        Node(String id) { this.id = id; }
    }

    // ------------------------------------------------------------------ result

    static class Result {
        int removed;
        Result(int removed) { this.removed = removed; }
    }

    // ------------------------------------------------------------------ slow (defect)

    static class DefectiveGroupUpdate {
        /**
         * For each currentMemberGroupID, scan the full memberGroupIDs list to
         * determine if it was removed.  O(G_current * G_member) = O(G²).
         */
        static Result updateRemovedMembers(List<String> currentMemberGroupIDs,
                                           List<String> memberGroupIDs) {
            int removed = 0;
            for (String currentID : currentMemberGroupIDs) {
                // CWE-407: linear scan of memberGroupIDs on each iteration
                boolean stillMember = memberGroupIDs.contains(currentID);  // O(G)
                if (!stillMember) {
                    removed++;
                    // would call UpsertGroupInTxn here
                }
            }
            return new Result(removed);
        }
    }

    // ------------------------------------------------------------------ fast (fix)

    static class FixedGroupUpdate {
        /**
         * Pre-build a HashSet from memberGroupIDs for O(1) lookup.
         * Total: O(G_current + G_member).
         */
        static Result updateRemovedMembers(List<String> currentMemberGroupIDs,
                                           List<String> memberGroupIDs) {
            // CWE-407 fix: O(1) lookup set
            Set<String> memberIDSet = new HashSet<>(memberGroupIDs);
            int removed = 0;
            for (String currentID : currentMemberGroupIDs) {
                if (!memberIDSet.contains(currentID)) {   // O(1)
                    removed++;
                }
            }
            return new Result(removed);
        }
    }

    // ------------------------------------------------------------------ helpers

    static List<String> buildGroupIDs(int n, String prefix) {
        List<String> ids = new ArrayList<>(n);
        for (int i = 0; i < n; i++) {
            ids.add(prefix + "-group-" + i);
        }
        return ids;
    }

    static long benchSlow(int G, int iters) {
        List<String> current = buildGroupIDs(G, "cur");
        // Half of current groups stay, half are removed
        List<String> newMembers = buildGroupIDs(G / 2, "cur");
        long start = System.nanoTime();
        for (int i = 0; i < iters; i++) {
            DefectiveGroupUpdate.updateRemovedMembers(current, newMembers);
        }
        return System.nanoTime() - start;
    }

    static long benchFast(int G, int iters) {
        List<String> current = buildGroupIDs(G, "cur");
        List<String> newMembers = buildGroupIDs(G / 2, "cur");
        long start = System.nanoTime();
        for (int i = 0; i < iters; i++) {
            FixedGroupUpdate.updateRemovedMembers(current, newMembers);
        }
        return System.nanoTime() - start;
    }

    // ------------------------------------------------------------------ main

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

        // ---- correctness
        List<String> current  = Arrays.asList("g1", "g2", "g3", "g4", "g5");
        List<String> newMems  = Arrays.asList("g1", "g3");  // g2,g4,g5 removed

        Result slowR = DefectiveGroupUpdate.updateRemovedMembers(current, newMems);
        Result fastR = FixedGroupUpdate.updateRemovedMembers(current, newMems);

        assert slowR.removed == 3 : "slow: expected 3 removed, got " + slowR.removed;
        assert fastR.removed == 3 : "fast: expected 3 removed, got " + fastR.removed;
        assert slowR.removed == fastR.removed : "slow/fast mismatch";
        System.out.println("Correctness: PASS (slow.removed == fast.removed == 3)");

        // ---- performance
        int ITERS = 200;
        int[] sizes = {400, 600, 1000};
        System.out.printf("%-8s  %-12s  %-12s  %s%n", "G(groups)", "slow(ns)", "fast(ns)", "ratio");

        for (int G : sizes) {
            // warm-up
            benchSlow(G, 20); benchFast(G, 20);

            long slowNs = benchSlow(G, ITERS);
            long fastNs = benchFast(G, ITERS);
            double ratio = (double) slowNs / fastNs;

            System.out.printf("%-8d  %-12d  %-12d  %.2fx%n", G, slowNs, fastNs, ratio);

            total++;
            double threshold = G <= 400 ? 3.5 : 5.0;  // JVM warmup noise at small N
            if (ratio >= threshold) {
                System.out.printf("  PASS (ratio=%.2f >= %.1f)%n", ratio, threshold);
                passed++;
            } else {
                System.out.printf("  FAIL (ratio=%.2f < %.1f)%n", ratio, threshold);
            }
        }

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