import java.util.*;

/**
 * Unit test for thunderbird-0003: nsAutoSyncManager IndexOf() in loops O(N^2)
 *
 * Simulates the IMAP auto-sync folder queue management where IndexOf() is
 * called per folder to find queue positions during sync scheduling.
 *
 * Defective: O(N^2) - IndexOf per folder in update loop
 * Fixed: O(N) - HashMap for O(1) index lookups
 */
public class ThunderbirdAutoSyncManagerTest {

    // --- Defective: O(N^2) index lookup per folder ---
    static int autoUpdateFoldersDefective(List<String> folders, List<String> updateQ) {
        int updates = 0;
        for (String folder : folders) {
            int idx = updateQ.indexOf(folder); // O(N) linear scan
            if (idx >= 0) {
                updates++;
                // Simulate state check using index position
            }
        }
        return updates;
    }

    // --- Fixed: O(N) with pre-built index map ---
    static int autoUpdateFoldersFixed(List<String> folders, Map<String, Integer> updateQIndex) {
        int updates = 0;
        for (String folder : folders) {
            Integer idx = updateQIndex.get(folder); // O(1) hash lookup
            if (idx != null) {
                updates++;
            }
        }
        return updates;
    }

    // --- Defective: O(N^2) sibling chaining ---
    static List<String> chainFoldersDefective(List<String> queue, List<String> priorityQ) {
        List<String> chained = new ArrayList<>();
        chained.add(priorityQ.get(0));
        for (int pqIdx = 1; pqIdx < priorityQ.size(); pqIdx++) {
            String candidate = priorityQ.get(pqIdx);
            for (int idx = 0; idx < chained.size(); idx++) {
                // Simulate IsSibling check (same server prefix)
                if (candidate.startsWith(chained.get(idx).split("/")[0])) {
                    chained.add(candidate);
                    break;
                }
            }
        }
        return chained;
    }

    // --- Fixed: O(N) sibling chaining with server set ---
    static List<String> chainFoldersFixed(List<String> queue, List<String> priorityQ) {
        List<String> chained = new ArrayList<>();
        Set<String> serverSet = new HashSet<>();
        chained.add(priorityQ.get(0));
        serverSet.add(priorityQ.get(0).split("/")[0]);
        for (int pqIdx = 1; pqIdx < priorityQ.size(); pqIdx++) {
            String candidate = priorityQ.get(pqIdx);
            String server = candidate.split("/")[0];
            if (serverSet.contains(server)) {
                chained.add(candidate);
            }
        }
        return chained;
    }

    public static void main(String[] args) {
        System.out.println("=== thunderbird-0003: nsAutoSyncManager IndexOf O(N^2) ===\n");

        // Correctness for autoUpdateFolders
        List<String> folders = Arrays.asList("f1", "f2", "f3", "f4");
        List<String> updateQ = Arrays.asList("f2", "f4", "f6");
        Map<String, Integer> updateQIndex = new HashMap<>();
        for (int i = 0; i < updateQ.size(); i++) updateQIndex.put(updateQ.get(i), i);

        int defCount = autoUpdateFoldersDefective(folders, updateQ);
        int fixCount = autoUpdateFoldersFixed(folders, updateQIndex);
        assert defCount == fixCount : "Counts must match";
        assert defCount == 2;
        System.out.println("PASS correctness: autoUpdate matches = " + defCount);

        // Benchmark autoUpdateFolders
        int[] sizes = {100, 500, 1000, 5000};
        for (int N : sizes) {
            List<String> allFolders = new ArrayList<>();
            List<String> uQ = new ArrayList<>();
            Map<String, Integer> uQIndex = new HashMap<>();
            for (int i = 0; i < N; i++) {
                allFolders.add("folder" + i);
                if (i % 3 == 0) { // ~33% in update queue
                    uQ.add("folder" + i);
                    uQIndex.put("folder" + i, uQ.size() - 1);
                }
            }

            // Warmup
            for (int w = 0; w < 3; w++) {
                autoUpdateFoldersDefective(allFolders, uQ);
                autoUpdateFoldersFixed(allFolders, uQIndex);
            }

            int iters = Math.max(1, 50000 / N);
            long t0 = System.nanoTime();
            for (int r = 0; r < iters; r++) autoUpdateFoldersDefective(allFolders, uQ);
            long defTime = System.nanoTime() - t0;

            t0 = System.nanoTime();
            for (int r = 0; r < iters; r++) autoUpdateFoldersFixed(allFolders, uQIndex);
            long fixTime = System.nanoTime() - t0;

            double ratio = (double) defTime / Math.max(1, fixTime);
            String status = ratio >= 2.0 ? "PASS" : "FAIL";
            System.out.printf("%s N=%5d  defective=%8dns  fixed=%8dns  ratio=%.1fx%n",
                    status, N, defTime / iters, fixTime / iters, ratio);
        }

        System.out.println("\nAll tests passed.");
    }
}