package unit;

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

/**
 * CWE-407 unit test: opensearch-005
 * IndexGraveyard.containsIndex — List<Tombstone> linear scan called per-index
 * inside DanglingIndicesState loop → O(I × T).
 *
 * Mirrors elasticsearch-004 — OpenSearch is a fork with the identical defect.
 *
 * Slow path: for (Tombstone t : tombstones) { if t.equals(index) ... } — O(T) per call.
 * Fast path: HashSet<Index>.contains() — O(1) per call.
 *
 * Compile: javac -d . IndexGraveyardDanglingContains.java
 * Run:     java -ea unit.IndexGraveyardDanglingContains
 */
public class IndexGraveyardDanglingContains {

    static final class Index {
        final String name;
        final String uuid;

        Index(String name, String uuid) {
            this.name = name;
            this.uuid = uuid;
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof Index)) return false;
            Index other = (Index) o;
            return name.equals(other.name) && uuid.equals(other.uuid);
        }

        @Override
        public int hashCode() {
            return Objects.hash(name, uuid);
        }
    }

    static final class Tombstone {
        final Index index;
        Tombstone(Index index) { this.index = index; }
        Index getIndex() { return index; }
    }

    // ---- Slow: O(T) per call ----

    static boolean slowContainsIndex(List<Tombstone> tombstones, Index index) {
        for (Tombstone tombstone : tombstones) {
            if (tombstone.getIndex().equals(index)) return true;
        }
        return false;
    }

    static List<Index> slowFindDangling(List<Index> diskIndices, List<Tombstone> tombstones) {
        List<Index> dangling = new ArrayList<>();
        for (Index index : diskIndices) {
            if (!slowContainsIndex(tombstones, index)) dangling.add(index);
        }
        return dangling;
    }

    // ---- Fast: O(1) per call after O(T) setup ----

    static List<Index> fastFindDangling(List<Index> diskIndices, List<Tombstone> tombstones) {
        Set<Index> graveyardSet = new HashSet<>(tombstones.size() * 2);
        for (Tombstone t : tombstones) graveyardSet.add(t.getIndex());
        List<Index> dangling = new ArrayList<>();
        for (Index index : diskIndices) {
            if (!graveyardSet.contains(index)) dangling.add(index);
        }
        return dangling;
    }

    static long countSlowOps(List<Index> diskIndices, List<Tombstone> tombstones) {
        long ops = 0;
        for (Index index : diskIndices) {
            for (Tombstone t : tombstones) {
                ops++;
                if (t.getIndex().equals(index)) break;
            }
        }
        return ops;
    }

    static long countFastOps(List<Index> diskIndices, List<Tombstone> tombstones) {
        long ops = 0;
        for (Tombstone t : tombstones) ops++;         // build set: O(T)
        for (Index ignored : diskIndices) ops++;       // lookup: O(1) each
        return ops;
    }

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

        // Test 1: correctness
        {
            List<Tombstone> tombstones = new ArrayList<>();
            List<Index> diskIndices = new ArrayList<>();
            for (int i = 0; i < 15; i++) {
                tombstones.add(new Tombstone(new Index("idx-" + i, "u" + i)));
            }
            for (int i = 0; i < 25; i++) {
                diskIndices.add(new Index("idx-" + i, "u" + i));
            }
            List<Index> slow = slowFindDangling(diskIndices, tombstones);
            List<Index> fast = fastFindDangling(diskIndices, tombstones);
            assert slow.size() == fast.size()
                : "FAIL: mismatch slow=" + slow.size() + " fast=" + fast.size();
            System.out.println("PASS test1: correctness — " + fast.size() + " dangling");
            passed++;
        }

        // Test 2: all tombstoned
        {
            List<Tombstone> tombstones = new ArrayList<>();
            List<Index> diskIndices = new ArrayList<>();
            for (int i = 0; i < 30; i++) {
                tombstones.add(new Tombstone(new Index("idx-" + i, "u" + i)));
                diskIndices.add(new Index("idx-" + i, "u" + i));
            }
            assert slowFindDangling(diskIndices, tombstones).size() == 0 : "FAIL slow";
            assert fastFindDangling(diskIndices, tombstones).size() == 0 : "FAIL fast";
            System.out.println("PASS test2: all tombstoned");
            passed++;
        }

        // Test 3: operation count ratio >= 10x
        {
            int I = 500, T = 500;
            List<Tombstone> tombstones = new ArrayList<>();
            List<Index> diskIndices = new ArrayList<>();
            for (int i = 0; i < T; i++) tombstones.add(new Tombstone(new Index("t" + i, "ut" + i)));
            for (int i = 0; i < I; i++) diskIndices.add(new Index("d" + i, "ud" + i));

            long slowOps = countSlowOps(diskIndices, tombstones);
            long fastOps = countFastOps(diskIndices, tombstones);
            double ratio = (double) slowOps / fastOps;
            System.out.printf("PASS test3: I=%d T=%d  slow=%d  fast=%d  ratio=%.1fx%n",
                I, T, slowOps, fastOps, ratio);
            assert ratio >= 10.0 : "FAIL: ratio " + ratio + " < 10x";
            passed++;
        }

        // Test 4: timing benchmark
        {
            int I = 2000, T = 500;
            List<Tombstone> tombstones = new ArrayList<>();
            List<Index> diskIndices = new ArrayList<>();
            for (int i = 0; i < T; i++) tombstones.add(new Tombstone(new Index("t" + i, "ut" + i)));
            for (int i = 0; i < I; i++) diskIndices.add(new Index("d" + i, "ud" + i));

            int reps = 200;
            long t0 = System.nanoTime();
            for (int r = 0; r < reps; r++) slowFindDangling(diskIndices, tombstones);
            long slowNs = System.nanoTime() - t0;

            long t1 = System.nanoTime();
            for (int r = 0; r < reps; r++) fastFindDangling(diskIndices, tombstones);
            long fastNs = System.nanoTime() - t1;

            double ratio = (double) slowNs / fastNs;
            System.out.printf("PASS test4: timing I=%d T=%d  slow=%.1fms fast=%.1fms ratio=%.1fx%n",
                I, T, slowNs / 1e6 / reps, fastNs / 1e6 / reps, ratio);
            assert ratio >= 10.0 : "FAIL: timing ratio " + ratio + " < 10x";
            passed++;
        }

        System.out.println(passed + "/" + passed + " PASS");
    }
}