mnemo_cards/mnemo_cards_backend/lib/database/daos/test_dao.dart

import 'package:drift/drift.dart';
import 'package:drift_postgres/drift_postgres.dart';
import '../database.dart';
import '../tables/tests.dart';

part 'test_dao.g.dart';

@DriftAccessor(
  tables: [Tests, TestQuestions, TestPackRelations, TestStatistics],
)
class TestDao extends DatabaseAccessor<AppDatabase> with _$TestDaoMixin {
  TestDao(super.db);

  // ==================== Tests ====================

  /// Получить тест по ID (включая soft-deleted для доступа по прямой ссылке)
  /// 
  /// Примечание: soft-deleted тесты не показываются в списке пака (getTestsByPackId),
  /// но доступны по прямой ссылке для завершения начатых тестов.
  Future<Test?> getTestById(String id) {
    return (select(tests)..where((t) => t.id.equals(id))).getSingleOrNull();
  }

  /// Получить все тесты (только активные)
  Future<List<Test>> getAllTests() {
    return (select(tests)..where((t) => t.isDeleted.equals(false))).get();
  }

  /// Получить тесты пака (только активные)
  Future<List<Test>> getTestsByPackId(String packId) async {
    final query = select(tests).join([
      innerJoin(
        testPackRelations,
        testPackRelations.testId.equalsExp(tests.id) &
            testPackRelations.packId.equals(packId),
      ),
    ])..where(tests.isDeleted.equals(false));

    return query.map((row) => row.readTable(tests)).get();
  }

  /// Создать тест
  Future<String> createTest(TestsCompanion test) async {
    final inserted = await into(tests).insertReturning(test);
    return inserted.id;
  }

  /// Обновить тест
  Future<bool> updateTest(Test test) {
    return update(tests).replace(test);
  }

  /// Удалить тест (soft delete)
  Future<void> softDeleteTest(String testId) {
    return (update(tests)..where((t) => t.id.equals(testId))).write(
      TestsCompanion(
        isDeleted: const Value(true),
        deletedAt: Value(PgDateTime(DateTime.now())),
        updatedAt: Value(PgDateTime(DateTime.now())),
      ),
    );
  }

  /// Soft delete tests that have expired (expiresAt <= now)
  /// 
  /// When expiresAt is reached, test becomes soft-deleted (available only by direct link)
  Future<int> softDeleteExpiredTests() async {
    final now = DateTime.now();
    
    final expiredTests = await (select(tests)..where(
          (t) =>
              t.expiresAt.isSmallerOrEqualValue(PgDateTime(now)) &
              t.isDeleted.equals(false),
        ))
        .get();

    var deleted = 0;
    for (final test in expiredTests) {
      await softDeleteTest(test.id);
      deleted++;
    }
    return deleted;
  }

  /// Hard delete old generated tests that were soft-deleted.
  ///
  /// This is important because we use soft delete for regular operations,
  /// but generated tests are ephemeral and otherwise will accumulate in DB
  /// (along with their questions/stats). Hard delete triggers FK cascades.
  /// 
  /// Hard deletes tests that were soft-deleted more than [olderThan] ago.
  Future<int> hardDeleteOldSoftDeletedGeneratedTests({
    required Duration olderThan,
  }) async {
    final threshold = DateTime.now().subtract(olderThan);

    final toDelete =
        await (select(tests)..where(
              (t) =>
                  t.isDeleted.equals(true) &
                  t.version.equals('generated') &
                  t.deletedAt.isSmallerThanValue(PgDateTime(threshold)),
            ))
            .get();

    var deleted = 0;
    for (final test in toDelete) {
      deleted += await (delete(tests)..where((t) => t.id.equals(test.id))).go();
    }
    return deleted;
  }

  /// Hard delete generated tests that are not linked to any pack.
  ///
  /// These tests are unreachable from the product (no pack relation) and
  /// should not accumulate forever. This also cleans up historical leftovers
  /// from the earlier bug where generated tests were created but not linked.
  Future<int> hardDeleteOrphanGeneratedTests({
    required Duration olderThan,
  }) async {
    final threshold = DateTime.now().subtract(olderThan);

    final rows =
        await (select(tests).join([
              leftOuterJoin(
                testPackRelations,
                testPackRelations.testId.equalsExp(tests.id),
              ),
            ])..where(
              tests.version.equals('generated') &
                  tests.createdAt.isSmallerThanValue(PgDateTime(threshold)) &
                  testPackRelations.testId.isNull(),
            ))
            .get();

    final orphanTests = rows.map((r) => r.readTable(tests)).toList();

    var deleted = 0;
    for (final test in orphanTests) {
      deleted += await (delete(tests)..where((t) => t.id.equals(test.id))).go();
    }
    return deleted;
  }

  /// Связать тест с паком
  Future<void> linkTestToPack(String testId, String packId) async {
    await into(testPackRelations).insert(
      TestPackRelationsCompanion.insert(testId: testId, packId: packId),
      mode: InsertMode.insertOrIgnore,
    );
  }

  /// Удалить связь теста с паком
  Future<void> unlinkTestFromPack(String testId, String packId) async {
    await (delete(testPackRelations)..where(
          (tpr) => tpr.testId.equals(testId) & tpr.packId.equals(packId),
        ))
        .go();
  }

  /// Получить packId для теста
  Future<String?> getPackIdForTest(String testId) async {
    final relation =
        await (select(testPackRelations)
              ..where((tpr) => tpr.testId.equals(testId))
              ..limit(1))
            .getSingleOrNull();
    return relation?.packId;
  }

  /// Получить все packId для теста
  Future<List<String>> getPackIdsForTest(String testId) async {
    final relations = await (select(
      testPackRelations,
    )..where((tpr) => tpr.testId.equals(testId))).get();
    return relations.map((r) => r.packId).toList();
  }

  // ==================== TestQuestions ====================

  /// Получить вопросы теста (только активные, отсортированные по orderIndex)
  Future<List<TestQuestion>> getTestQuestions(String testId) {
    return (select(testQuestions)
          ..where((tq) => tq.testId.equals(testId) & tq.isDeleted.equals(false))
          ..orderBy([(tq) => OrderingTerm(expression: tq.orderIndex)]))
        .get();
  }

  /// Создать вопрос теста
  Future<String> createTestQuestion(TestQuestionsCompanion question) async {
    final inserted = await into(testQuestions).insertReturning(question);
    return inserted.id;
  }

  /// Обновить вопрос теста
  Future<bool> updateTestQuestion(TestQuestion question) {
    return update(testQuestions).replace(question);
  }

  /// Удалить вопрос теста (soft delete)
  Future<void> softDeleteTestQuestion(String questionId) {
    return (update(
      testQuestions,
    )..where((tq) => tq.id.equals(questionId))).write(
      TestQuestionsCompanion(
        isDeleted: const Value(true),
        deletedAt: Value(PgDateTime(DateTime.now())),
        updatedAt: Value(PgDateTime(DateTime.now())),
      ),
    );
  }

  // ==================== TestStatistics ====================

  /// Получить статистику теста пользователя
  Future<TestStatistic?> getTestStatistics(String userId, String testId) {
    return (select(testStatistics)
          ..where((ts) => ts.userId.equals(userId) & ts.testId.equals(testId)))
        .getSingleOrNull();
  }

  /// Создать статистику теста
  Future<String> createTestStatistics(
    TestStatisticsCompanion statistics,
  ) async {
    final inserted = await into(testStatistics).insertReturning(statistics);
    return inserted.id;
  }

  /// Обновить статистику теста
  Future<bool> updateTestStatistics(TestStatistic statistics) {
    return update(testStatistics).replace(statistics);
  }
}