import 'dart:convert';

import 'package:crypto/crypto.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:kooltap/services/pin_lock_service.dart';

import 'helpers/memory_secure_storage.dart';

String _legacyHash(String pin, String salt) {
  return sha256.convert(utf8.encode('$salt:$pin')).toString();
}

void main() {
  late MemorySecureStorage storage;
  late DateTime now;
  late PinLockService service;

  setUp(() {
    storage = MemorySecureStorage();
    now = DateTime(2026, 10, 7, 12);
    service = PinLockService(storage: storage, clock: () => now);
  });

  Future<void> failTimes(int count) async {
    for (var attempt = 0; attempt < count; attempt++) {
      await service.verifyPin('0000');
    }
  }

  group('PinLockService', () {
    group('hasPin', () {
      test('returns false when no hash stored', () async {
        expect(await service.hasPin(), false);
      });

      test('returns false when hash is empty', () async {
        storage.values['pin_hash'] = '';

        expect(await service.hasPin(), false);
      });

      test('returns true once a pin is set', () async {
        await service.setPin('1234');

        expect(await service.hasPin(), true);
      });
    });

    group('setPin', () {
      test('stores a salted PBKDF2 hash', () async {
        await service.setPin('1234');

        expect(storage.values['pin_salt'], isNotEmpty);
        expect(storage.values['pin_hash'], startsWith(r'pbkdf2-sha256$'));
        expect(storage.values['pin_hash'], isNot(contains('1234')));
      });

      test('generates unique salts for different pins', () async {
        await service.setPin('1234');
        final firstSalt = storage.values['pin_salt'];

        await service.setPin('5678');

        expect(storage.values['pin_salt'], isNot(firstSalt));
      });
    });

    group('verifyPin', () {
      test('returns false when salt is missing', () async {
        storage.values['pin_hash'] = 'somehash';

        expect(await service.verifyPin('1234'), false);
      });

      test('returns false when hash is missing', () async {
        storage.values['pin_salt'] = 'somesalt';

        expect(await service.verifyPin('1234'), false);
      });

      test('returns true for correct pin', () async {
        await service.setPin('1234');

        expect(await service.verifyPin('1234'), true);
      });

      test('returns false for incorrect pin', () async {
        await service.setPin('1234');

        expect(await service.verifyPin('5678'), false);
      });

      test('accepts a legacy hash and upgrades it', () async {
        storage.values['pin_salt'] = 'test_salt';
        storage.values['pin_hash'] = _legacyHash('1234', 'test_salt');

        expect(await service.verifyPin('1234'), true);
        expect(storage.values['pin_hash'], startsWith(r'pbkdf2-sha256$'));
        expect(await service.verifyPin('1234'), true);
      });

      test('rejects a wrong pin against a legacy hash', () async {
        storage.values['pin_salt'] = 'test_salt';
        storage.values['pin_hash'] = _legacyHash('1234', 'test_salt');

        expect(await service.verifyPin('5678'), false);
        expect(storage.values['pin_hash'], _legacyHash('1234', 'test_salt'));
      });
    });

    group('lockout', () {
      test('locks after five wrong attempts', () async {
        await service.setPin('1234');
        await failTimes(5);

        await expectLater(
          service.verifyPin('1234'),
          throwsA(isA<PinLockedOutException>()),
        );
      });

      test('unlocks once the lockout has passed', () async {
        await service.setPin('1234');
        await failTimes(5);

        now = now.add(const Duration(seconds: 31));

        expect(await service.verifyPin('1234'), true);
      });

      test('doubles the lockout for every further failure', () async {
        await service.setPin('1234');
        await failTimes(5);
        now = now.add(const Duration(seconds: 31));
        await failTimes(1);

        now = now.add(const Duration(seconds: 31));
        await expectLater(
          service.verifyPin('1234'),
          throwsA(isA<PinLockedOutException>()),
        );

        now = now.add(const Duration(seconds: 30));
        expect(await service.verifyPin('1234'), true);
      });

      test('a correct pin resets the failure count', () async {
        await service.setPin('1234');
        await failTimes(4);
        await service.verifyPin('1234');
        await failTimes(4);

        expect(await service.verifyPin('1234'), true);
      });
    });

    group('clearPin', () {
      test('deletes the pin and any lockout', () async {
        await service.setPin('1234');
        await failTimes(5);

        await service.clearPin();

        expect(storage.values, isEmpty);
      });
    });
  });
}