import java.util.*;

/**
 * Unit test simulating Forgejo forgejo-0003:
 * models/asymkey/ssh_key.go synchronizePublicKeys() has three O(N*M) scans:
 *
 * 1. Building providedKeys with dedup: O(K^2) where K = LDAP-provided key count
 *    for _, v := range sshPublicKeys {
 *        key = ...
 *        if !util.SliceContainsString(providedKeys, key) {  // O(|providedKeys|) each time
 *
 * 2. Finding new keys: O(P * G) where P = provided, G = DB keys
 *    for _, key := range providedKeys {
 *        if !util.SliceContainsString(giteaKeys, key) {     // O(G) each
 *
 * 3. Finding deleted keys: O(G * P)
 *    for _, giteaKey := range giteaKeys {
 *        if !util.SliceContainsString(providedKeys, giteaKey) {  // O(P) each
 *
 * This runs per user per LDAP sync cycle. With many users or large key sets it accumulates.
 * Fix: build maps for O(1) lookup before each loop.
 */
public class ForgejoSSHKeySyncTest {

    // Defective: O(K^2) dedup + O(P*G) + O(G*P)
    static long countDefectiveOps(int rawKeyCount, int giteaKeyCount) {
        // Phase 1: dedup raw keys into providedKeys
        // Assume half are unique: K/2 unique keys, K/2 duplicates
        // Each insertion checks against growing list
        long ops = 0;
        int provided = 0;
        for (int i = 0; i < rawKeyCount; i++) {
            ops += provided;  // SliceContainsString cost
            if (i % 2 == 0) provided++;  // ~half unique
        }
        // Phase 2: find new keys (provided not in gitea)
        ops += (long) provided * giteaKeyCount;
        // Phase 3: find keys to delete (gitea not in provided)
        ops += (long) giteaKeyCount * provided;
        return ops;
    }

    static long countFixedOps(int rawKeyCount, int giteaKeyCount) {
        // Phase 1: dedup with set — O(K) total
        long ops = rawKeyCount;
        int provided = rawKeyCount / 2;  // ~half unique
        // Build giteaKeysSet: O(G)
        ops += giteaKeyCount;
        // Phase 2: find new keys — O(P)
        ops += provided;
        // Phase 3: find keys to delete — O(G)
        ops += giteaKeyCount;
        return ops;
    }

    // Simulate the sync logic for correctness
    static Map<String, List<String>> syncKeysDefective(
            List<String> rawKeys, List<String> giteaKeys) {
        // Dedup rawKeys
        List<String> provided = new ArrayList<>();
        for (String k : rawKeys) {
            if (!provided.contains(k)) {
                provided.add(k);
            }
        }
        // Find new keys
        List<String> toAdd = new ArrayList<>();
        for (String k : provided) {
            if (!giteaKeys.contains(k)) {
                toAdd.add(k);
            }
        }
        // Find keys to delete
        List<String> toDelete = new ArrayList<>();
        for (String k : giteaKeys) {
            if (!provided.contains(k)) {
                toDelete.add(k);
            }
        }
        Map<String, List<String>> result = new HashMap<>();
        result.put("toAdd", toAdd);
        result.put("toDelete", toDelete);
        return result;
    }

    static Map<String, List<String>> syncKeysFixed(
            List<String> rawKeys, List<String> giteaKeys) {
        // Dedup rawKeys with set
        Set<String> providedSet = new LinkedHashSet<>();
        List<String> provided = new ArrayList<>();
        for (String k : rawKeys) {
            if (providedSet.add(k)) {
                provided.add(k);
            }
        }
        // Build giteaKeys set
        Set<String> giteaSet = new HashSet<>(giteaKeys);
        // Find new keys
        List<String> toAdd = new ArrayList<>();
        for (String k : provided) {
            if (!giteaSet.contains(k)) {
                toAdd.add(k);
            }
        }
        // Find keys to delete
        List<String> toDelete = new ArrayList<>();
        for (String k : giteaKeys) {
            if (!providedSet.contains(k)) {
                toDelete.add(k);
            }
        }
        Map<String, List<String>> result = new HashMap<>();
        result.put("toAdd", toAdd);
        result.put("toDelete", toDelete);
        return result;
    }

    public static void main(String[] args) {
        System.out.println("forgejo-0003: synchronizePublicKeys() O(K^2+P*G) -> O(K+P+G)");
        System.out.println("=".repeat(60));

        // Correctness test
        List<String> rawKeys = Arrays.asList(
            "ssh-rsa AAAA1", "ssh-rsa AAAA2", "ssh-rsa AAAA1",  // dup
            "ssh-rsa AAAA3", "ssh-rsa AAAA2"                     // more dups
        );
        List<String> giteaKeys = Arrays.asList(
            "ssh-rsa AAAA2", "ssh-rsa AAAA4"
        );

        Map<String, List<String>> def = syncKeysDefective(rawKeys, giteaKeys);
        Map<String, List<String>> fix = syncKeysFixed(rawKeys, giteaKeys);

        // Expected: add AAAA1 and AAAA3 (new from LDAP), delete AAAA4 (no longer in LDAP)
        List<String> expectedAdd = Arrays.asList("ssh-rsa AAAA1", "ssh-rsa AAAA3");
        List<String> expectedDelete = Arrays.asList("ssh-rsa AAAA4");

        if (!def.get("toAdd").equals(expectedAdd)) {
            throw new AssertionError("Defective toAdd wrong: " + def.get("toAdd"));
        }
        if (!def.get("toDelete").equals(expectedDelete)) {
            throw new AssertionError("Defective toDelete wrong: " + def.get("toDelete"));
        }
        if (!fix.get("toAdd").equals(expectedAdd)) {
            throw new AssertionError("Fixed toAdd wrong: " + fix.get("toAdd"));
        }
        if (!fix.get("toDelete").equals(expectedDelete)) {
            throw new AssertionError("Fixed toDelete wrong: " + fix.get("toDelete"));
        }
        System.out.println("PASS: correctness verified");

        // Performance comparison
        System.out.printf("%n%-20s %15s %12s %10s%n",
            "scenario", "defective_ops", "fixed_ops", "ratio");
        System.out.println("-".repeat(58));

        int[][] scenarios = {
            {10, 10}, {50, 50}, {100, 100}, {500, 500}, {1000, 1000}
        };
        for (int[] sc : scenarios) {
            int K = sc[0], G = sc[1];
            long dOps = countDefectiveOps(K, G);
            long fOps = countFixedOps(K, G);
            double ratio = (double) dOps / fOps;
            System.out.printf("K=%-4d G=%-4d      %15d %12d %9.1fx%n",
                K, G, dOps, fOps, ratio);
        }

        long dOps = countDefectiveOps(500, 500);
        long fOps = countFixedOps(500, 500);
        double ratio = (double) dOps / fOps;
        if (ratio < 10) {
            throw new AssertionError("Expected >10x ratio at K=500 G=500, got " + ratio);
        }

        System.out.println("\nAll assertions PASS");
        System.out.println("Fix: use providedKeysSet(map) for O(1) dedup; giteaKeysSet for O(1) diff");
    }
}