import 'package:flutter_test/flutter_test.dart';
import 'package:kouyu_english/core/app_state.dart';
import 'package:kouyu_english/core/a0_core.dart';
import 'package:kouyu_english/core/assessment_bank.dart';
import 'package:kouyu_english/core/generated_content.dart';
import 'package:kouyu_english/core/models.dart';
import 'package:kouyu_english/core/seed_courses.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() {
  ReviewItem dueItem([String id = 'A0-P12']) => ReviewItem(
    id: id,
    target: "I'm from [place].",
    prompt: 'Hi! Where are you from?',
    hint: "I'm from Hong Kong.",
    dueAt: DateTime.now(),
    skill: '口语表达',
  );

  test('an overdue review is always the primary task', () {
    final state = AppState();
    state.reviewQueue.add(dueItem());

    expect(state.reviewIsPrimary, isTrue);
    expect(state.dueReviewCount, 1);
  });

  test('review backlog follows time budget or a seven-day overdue item', () {
    final overdue = AppState();
    overdue.reviewQueue.add(
      dueItem().copyWith(
        dueAt: DateTime.now().subtract(const Duration(days: 8)),
      ),
    );
    expect(overdue.reviewBacklog, isTrue);

    final crowded = AppState();
    for (var index = 0; index < 11; index++) {
      crowded.reviewQueue.add(dueItem('A0-T$index'));
    }
    expect(crowded.dueReviewEstimatedSeconds, 11 * 60);
    expect(crowded.reviewBacklog, isTrue);
  });

  test(
    'A0 reinforcement schedules a stable target with a new prompt variant',
    () {
      final state = AppState();
      state.scheduleA0Reinforcement();

      expect(state.dueReviewCount, 1);
      final item = state.dueReviews.single;
      expect(a0CoreItems, contains(item.id));
      expect(item.variantIndex, 1);
      expect(item.prompt, contains('情境'));
    },
  );

  test('an approved AI variant remains tied to its original review item', () {
    final state = AppState();
    state.reviewQueue.add(dueItem());
    state.applyGeneratedReviewVariant(
      const GeneratedReviewVariant(
        variantId: 'ai-1',
        targetItemId: 'A0-P12',
        prompt: '换一个地点，用英语说你来自哪里。',
        expectedAnswer: "I'm from [place].",
      ),
    );

    expect(state.reviewQueue.single.id, 'A0-P12');
    expect(state.reviewQueue.single.isAiGenerated, isTrue);
  });

  test(
    'reporting an AI review variant isolates it and invalidates its success',
    () {
      final state = AppState();
      state.reviewQueue.add(dueItem());
      state.applyGeneratedReviewVariant(
        const GeneratedReviewVariant(
          variantId: 'ai-report-1',
          targetItemId: 'A0-P12',
          prompt: '不合适的题面。',
          expectedAnswer: "I'm from [place].",
        ),
      );
      final generated = state.reviewQueue.single;
      state.completeReview(
        generated,
        assisted: false,
        rawAnswer: "I'm from Hong Kong.",
      );

      state.reportGeneratedReviewVariant(state.reviewQueue.single);

      expect(state.reviewQueue.single.isAiGenerated, isFalse);
      expect(state.reportedAiVariantKeys, contains('A0-P12:1'));
      expect(state.mastery['A0-P12']!.checkpoint, 0);
      expect(
        state.attemptEvidence.any((entry) => entry.variantIndex == 1),
        isFalse,
      );
    },
  );

  test('a completed review is scheduled again instead of being discarded', () {
    final state = AppState();
    state.reviewQueue.add(dueItem());
    final item = state.dueReviews.first;

    state.completeReview(item, assisted: false);

    expect(state.reviewQueue, hasLength(1));
    final updated = state.reviewQueue.firstWhere(
      (candidate) => candidate.id == item.id,
    );
    expect(updated.successfulReviews, 1);
    expect(updated.dueAt.isAfter(DateTime.now()), isTrue);
  });

  test('four independent review checkpoints lead to mastered status', () {
    final state = AppState();
    state.reviewQueue.add(dueItem());
    final item = state.reviewQueue.first;
    state.attemptEvidence.add(
      AttemptEvidence(
        id: 'recognized',
        itemId: item.id,
        taskId: 'lesson-a0-06-a-listening-check',
        skill: '听辨识别',
        inputMode: 'choice',
        outcome: EvidenceKind.independentSuccess,
        createdAt: DateTime.now().subtract(const Duration(days: 20)),
      ),
    );

    for (var index = 0; index < 4; index++) {
      final current = state.reviewQueue.firstWhere(
        (candidate) => candidate.id == item.id,
      );
      final queueIndex = state.reviewQueue.indexOf(current);
      state.reviewQueue[queueIndex] = current.copyWith(
        dueAt: DateTime.now(),
        lastProgressedAt: DateTime.now().subtract(const Duration(days: 1)),
      );
      state.completeReview(
        state.reviewQueue.firstWhere((candidate) => candidate.id == item.id),
        assisted: false,
      );
    }

    expect(state.mastery[item.id]!.checkpoint, 4);
    expect(state.mastery[item.id]!.status, MasteryStatus.master);
    // Later checks rotate to other reviewed situations.
    expect(
      state.reviewQueue
          .firstWhere((candidate) => candidate.id == item.id)
          .variantIndex,
      4,
    );
    expect(
      state.reviewQueue
          .firstWhere((candidate) => candidate.id == item.id)
          .dueAt
          .isAfter(DateTime.now().add(const Duration(days: 29))),
      isTrue,
    );
  });

  test('mastery can be rebuilt from spaced review evidence', () {
    final state = AppState();
    final base = DateTime.utc(2026, 9, 1);
    state.attemptEvidence.add(
      AttemptEvidence(
        id: 'recognized',
        itemId: 'A0-P12',
        taskId: 'lesson-a0-06-a-listening-check',
        skill: '听辨识别',
        inputMode: 'choice',
        outcome: EvidenceKind.independentSuccess,
        createdAt: base,
      ),
    );
    for (var index = 0; index < 4; index++) {
      state.attemptEvidence.add(
        AttemptEvidence(
          id: 'rebuilt-$index',
          itemId: 'A0-P12',
          taskId: 'review-A0-P12',
          skill: '口语表达',
          inputMode: 'text',
          outcome: EvidenceKind.independentSuccess,
          createdAt: base.add(Duration(days: index + 1)),
          variantIndex: index,
        ),
      );
    }

    state.rebuildMasteryFromEvidence();

    expect(state.mastery['A0-P12']!.checkpoint, 4);
    expect(state.mastery['A0-P12']!.status, MasteryStatus.master);
  });

  test('four checkpoints without every kind of evidence are not mastery', () {
    final state = AppState();
    final base = DateTime.utc(2026, 9, 1);
    for (var index = 0; index < 4; index++) {
      state.attemptEvidence.add(
        AttemptEvidence(
          id: 'same-context-$index',
          itemId: 'A0-P12',
          taskId: 'review-A0-P12',
          skill: '口语表达',
          inputMode: 'text',
          outcome: EvidenceKind.independentSuccess,
          createdAt: base.add(Duration(days: index + 1)),
        ),
      );
    }

    state.rebuildMasteryFromEvidence();

    // No recognition success and never used outside the original situation.
    expect(state.mastery['A0-P12']!.checkpoint, 4);
    expect(state.mastery['A0-P12']!.status, MasteryStatus.recall);
  });

  test('a review success never lowers an existing status', () {
    final state = AppState();
    state.mastery['A0-P12'] = const MasteryItem(
      id: 'A0-P12',
      label: "I'm from [place].",
      status: MasteryStatus.use,
      evidence: [],
      checkpoint: 1,
    );
    state.reviewQueue.add(dueItem());

    state.completeReview(state.reviewQueue.single, assisted: false);

    expect(state.mastery['A0-P12']!.status, MasteryStatus.use);
  });

  test('review checkpoints follow days 1, 3, 7 and 14', () {
    final state = AppState();
    state.reviewQueue.add(dueItem());
    final gaps = <int>[];
    for (var index = 0; index < 3; index++) {
      final current = state.reviewQueue.single;
      state.reviewQueue[0] = current.copyWith(
        dueAt: DateTime.now(),
        lastProgressedAt: DateTime.now().subtract(const Duration(days: 1)),
      );
      state.completeReview(state.reviewQueue.single, assisted: false);
      gaps.add(
        state.reviewQueue.single.dueAt.difference(DateTime.now()).inHours ~/
                24 +
            1,
      );
    }
    expect(gaps, [2, 4, 7]);
  });

  test(
    'rebuild keeps first failure as review and second failure lowers checkpoint',
    () {
      final state = AppState();
      final base = DateTime.utc(2026, 9, 1);
      for (var index = 0; index < 3; index++) {
        state.attemptEvidence.add(
          AttemptEvidence(
            id: 'success-$index',
            itemId: 'A0-P12',
            taskId: 'review-A0-P12',
            skill: '口语表达',
            inputMode: 'text',
            outcome: EvidenceKind.independentSuccess,
            createdAt: base.add(Duration(days: index + 1)),
          ),
        );
      }
      for (var index = 0; index < 2; index++) {
        state.attemptEvidence.add(
          AttemptEvidence(
            id: 'failure-$index',
            itemId: 'A0-P12',
            taskId: 'review-A0-P12',
            skill: '口语表达',
            inputMode: 'text',
            outcome: EvidenceKind.languageError,
            createdAt: base.add(Duration(days: index + 10)),
          ),
        );
      }

      state.rebuildMasteryFromEvidence();

      expect(state.mastery['A0-P12']!.checkpoint, 2);
      expect(state.mastery['A0-P12']!.needsReview, isTrue);
    },
  );

  test('a same-day second success does not advance a review checkpoint', () {
    final state = AppState();
    state.reviewQueue.add(dueItem());
    state.completeReview(state.reviewQueue.first, assisted: false);
    state.completeReview(state.reviewQueue.first, assisted: false);

    final updated = state.reviewQueue.single;
    expect(updated.successfulReviews, 1);
    expect(state.mastery[updated.id]!.checkpoint, 1);
  });

  test(
    'a duplicate review submission creates no extra evidence or attempt',
    () {
      final state = AppState();
      state.reviewQueue.add(dueItem());
      final submitted = state.reviewQueue.single;

      state.completeReview(submitted, assisted: false);
      state.completeReview(submitted, assisted: false);

      expect(state.reviewQueue.single.attempts, 1);
      expect(state.attemptEvidence, hasLength(1));
      expect(state.mastery[submitted.id]!.checkpoint, 1);
    },
  );

  test('one review failure requests a check, two lower one checkpoint', () {
    final state = AppState();
    state.reviewQueue.add(dueItem());
    final item = state.reviewQueue.first;
    state.mastery[item.id] = MasteryItem(
      id: item.id,
      label: item.target,
      status: MasteryStatus.master,
      checkpoint: 4,
      evidence: const [EvidenceKind.independentSuccess],
    );

    state.reportReviewFailure(item);
    expect(state.mastery[item.id]!.needsReview, isTrue);
    expect(state.mastery[item.id]!.checkpoint, 4);
    state.reportReviewFailure(item);
    expect(state.mastery[item.id]!.checkpoint, 3);
    expect(state.mastery[item.id]!.status, MasteryStatus.use);
  });

  test(
    'lesson dialogue must finish before independent attempt can complete lesson',
    () {
      final state = AppState();
      state.completePreview();
      state.completeListening();
      state.completeSpeaking();
      state.completeReading();
      state.completeWriting(assisted: true);

      expect(state.lessonCanComplete, isFalse);
      state.completeLessonDialogue();
      expect(state.lessonStep, LessonStep.independent);
      state.completeIndependentAttempt(assisted: false);
      expect(state.lessonCanComplete, isTrue);
    },
  );

  test(
    'restores lesson settings and review schedule from local storage',
    () async {
      SharedPreferences.setMockInitialValues({});
      final first = AppState();
      await first.load();
      first.setDailyMinutes(30);
      first.setGoal(LearningGoal.travel);
      first.completePreview();
      await Future<void>.delayed(Duration.zero);
      await Future<void>.delayed(Duration.zero);

      final restored = AppState();
      await restored.load();
      expect(restored.dailyMinutes, 30);
      expect(restored.goal, LearningGoal.travel);
      expect(restored.lessonStep, LessonStep.listening);
      expect(restored.reviewQueue, isEmpty);
    },
  );

  test('restores in-progress writing and independent-answer drafts', () async {
    SharedPreferences.setMockInitialValues({});
    final first = AppState();
    await first.load();
    first.advanceLesson(LessonStep.writing);
    first.setLessonWritingDraft("I'm from Hong Kong.");
    first.setIndependentAttemptDraft('I like tea.');
    await Future<void>.delayed(Duration.zero);
    await Future<void>.delayed(Duration.zero);

    final restored = AppState();
    await restored.load();
    expect(restored.lessonStep, LessonStep.writing);
    expect(restored.lessonWritingDraft, "I'm from Hong Kong.");
    expect(restored.independentAttemptDraft, 'I like tea.');
  });

  test('restores an approved cached adaptive lesson', () async {
    SharedPreferences.setMockInitialValues({});
    final first = AppState();
    await first.load();
    first.cacheApprovedAdaptiveLesson(
      const GeneratedLesson(
        lessonId: 'ai-a0-p12-1',
        revision: 1,
        stageVersion: 'A0-1.0',
        abilityIds: ['A0-C06'],
        prerequisiteIds: ['a0-05'],
        targetItemIds: ['A0-P12'],
        receptiveChunks: [],
        previewItemIds: [],
        estimatedMinutes: 10,
        tasks: [
          GeneratedLessonTask(
            taskId: 'l',
            skill: 'listening',
            type: 'listenChoice',
            prompt: '听。',
            stimulus: 'I am from Hong Kong.',
            answer: 'Hong Kong',
            targetItemIds: ['A0-P12'],
          ),
          GeneratedLessonTask(
            taskId: 's',
            skill: 'speaking',
            type: 'repeat',
            prompt: '说。',
            stimulus: 'I am from Hong Kong.',
            answer: 'I am from Hong Kong.',
            targetItemIds: ['A0-P12'],
          ),
          GeneratedLessonTask(
            taskId: 'r',
            skill: 'reading',
            type: 'readAnswer',
            prompt: '读。',
            stimulus: 'I am from Hong Kong.',
            answer: 'Hong Kong',
            targetItemIds: ['A0-P12'],
          ),
          GeneratedLessonTask(
            taskId: 'w',
            skill: 'writing',
            type: 'writeAnswer',
            prompt: '写。',
            stimulus: '来自香港。',
            answer: 'I am from Hong Kong.',
            targetItemIds: ['A0-P12'],
          ),
        ],
      ),
      auditedAt: DateTime.utc(2026, 9, 13, 9, 30),
      auditor: 'compatible:test-model',
    );
    await Future<void>.delayed(Duration.zero);
    await Future<void>.delayed(Duration.zero);

    final restored = AppState();
    await restored.load();
    expect(restored.cachedAdaptiveLesson, isNotNull);
    expect(restored.cachedAdaptiveLesson!.targetItemIds, ['A0-P12']);
    expect(
      restored.cachedAdaptiveLessonAuditedAt,
      DateTime.utc(2026, 9, 13, 9, 30),
    );
    expect(restored.cachedAdaptiveLessonAuditor, 'compatible:test-model');
  });

  test(
    'adaptive lesson draft restores and a report isolates its cache',
    () async {
      SharedPreferences.setMockInitialValues({});
      final first = AppState();
      await first.load();
      first.cacheApprovedAdaptiveLesson(
        const GeneratedLesson(
          lessonId: 'ai-a0-p12-2',
          revision: 1,
          stageVersion: 'A0-1.0',
          abilityIds: ['A0-C06'],
          prerequisiteIds: ['a0-05'],
          targetItemIds: ['A0-P12'],
          receptiveChunks: [],
          previewItemIds: [],
          estimatedMinutes: 10,
          tasks: [
            GeneratedLessonTask(
              taskId: 'l',
              skill: 'listening',
              type: 'listenChoice',
              prompt: 'Listen.',
              stimulus: 'I am from Hong Kong.',
              answer: 'Hong Kong',
              targetItemIds: ['A0-P12'],
            ),
            GeneratedLessonTask(
              taskId: 's',
              skill: 'speaking',
              type: 'repeat',
              prompt: 'Say it.',
              stimulus: 'I am from Hong Kong.',
              answer: 'I am from Hong Kong.',
              targetItemIds: ['A0-P12'],
            ),
            GeneratedLessonTask(
              taskId: 'r',
              skill: 'reading',
              type: 'readAnswer',
              prompt: 'Read.',
              stimulus: 'I am from Hong Kong.',
              answer: 'Hong Kong',
              targetItemIds: ['A0-P12'],
            ),
            GeneratedLessonTask(
              taskId: 'w',
              skill: 'writing',
              type: 'writeAnswer',
              prompt: 'Write.',
              stimulus: 'From Hong Kong.',
              answer: 'I am from Hong Kong.',
              targetItemIds: ['A0-P12'],
            ),
          ],
        ),
      );
      final lesson = first.cachedAdaptiveLesson!;
      first.saveAdaptiveLessonDraft(
        lesson: lesson,
        taskIndex: 2,
        answer: 'Hong Kong',
        referenceShown: true,
        usedVoice: true,
        transcriptConfirmed: true,
        originalTranscript: 'Hong Kong',
        recordingPath: '/private/local/answer.m4a',
      );
      await Future<void>.delayed(Duration.zero);
      await Future<void>.delayed(Duration.zero);

      final restored = AppState();
      await restored.load();
      expect(restored.adaptiveLessonDraftId, 'ai-a0-p12-2');
      expect(restored.adaptiveLessonDraftIndex, 2);
      expect(restored.adaptiveLessonDraftAnswer, 'Hong Kong');
      expect(restored.adaptiveLessonDraftReferenceShown, isTrue);
      expect(restored.adaptiveLessonDraftUsedVoice, isTrue);
      expect(restored.adaptiveLessonDraftTranscriptConfirmed, isTrue);
      expect(restored.adaptiveLessonDraftTranscriptEdited, isFalse);
      expect(restored.adaptiveLessonDraftOriginalTranscript, 'Hong Kong');
      expect(
        restored.adaptiveLessonDraftRecordingPath,
        '/private/local/answer.m4a',
      );

      restored.reportAdaptiveLesson(restored.cachedAdaptiveLesson!);
      expect(restored.cachedAdaptiveLesson, isNull);
      expect(restored.reportedAdaptiveLessonIds, contains('ai-a0-p12-2'));
    },
  );

  test('an edited adaptive transcript is persisted only as text evidence', () {
    final state = AppState();
    const lesson = GeneratedLesson(
      lessonId: 'ai-a0-p12-boundary',
      revision: 1,
      stageVersion: 'A0-1.0',
      abilityIds: ['A0-C06'],
      prerequisiteIds: ['a0-05'],
      targetItemIds: ['A0-P12'],
      receptiveChunks: [],
      previewItemIds: [],
      estimatedMinutes: 10,
      tasks: [
        GeneratedLessonTask(
          taskId: 'speaking',
          skill: 'speaking',
          type: 'repeat',
          prompt: 'Say it.',
          stimulus: 'I am from Hong Kong.',
          answer: 'I am from Hong Kong.',
          targetItemIds: ['A0-P12'],
        ),
      ],
    );
    const task = GeneratedLessonTask(
      taskId: 'speaking',
      skill: 'speaking',
      type: 'repeat',
      prompt: 'Say it.',
      stimulus: 'I am from Hong Kong.',
      answer: 'I am from Hong Kong.',
      targetItemIds: ['A0-P12'],
    );

    // This deliberately contradictory input models a future caller bug.
    // The domain layer, rather than only the widget, must protect evidence.
    state.recordAdaptiveLessonTask(
      lesson: lesson,
      task: task,
      rawAnswer: 'I am from Hong Kong.',
      assisted: false,
      correct: true,
      inputMode: 'speechToText',
      originalTranscript: 'I am from Home Kong.',
      transcriptConfirmed: true,
      transcriptEdited: true,
    );

    final evidence = state.attemptEvidence.single;
    expect(evidence.inputMode, 'text');
    expect(evidence.transcriptConfirmed, isFalse);
    expect(evidence.transcriptEdited, isTrue);
    expect(evidence.originalTranscript, 'I am from Home Kong.');

    state.saveAdaptiveLessonDraft(
      lesson: lesson,
      taskIndex: 0,
      answer: evidence.rawAnswer ?? '',
      referenceShown: false,
      usedVoice: true,
      transcriptConfirmed: true,
      transcriptEdited: true,
      originalTranscript: evidence.originalTranscript ?? '',
    );
    expect(state.adaptiveLessonDraftTranscriptConfirmed, isFalse);
    expect(state.adaptiveLessonDraftTranscriptEdited, isTrue);

    state.recordAdaptiveLessonTask(
      lesson: lesson,
      task: task,
      rawAnswer: 'I am from Hong Kong.',
      assisted: false,
      correct: true,
    );
    expect(state.attemptEvidence, hasLength(1));
    // An unaided adaptive answer is recall in a situation other than the
    // lesson, which is what usable means.
    expect(state.mastery['A0-P12']!.status, MasteryStatus.use);
  });

  test(
    'temporary definitions remain local and survive state restoration',
    () async {
      SharedPreferences.setMockInitialValues({});
      final first = AppState();
      await first.load();
      first.setAiProvider(AiProviderType.compatible);
      first.saveAiConfiguration(
        endpoint: 'https://example.test/v1',
        model: 'demo',
      );
      first.cacheTemporaryDefinition(query: 'library', definition: '图书馆');
      expect(first.mastery, isEmpty);
      expect(first.reviewQueue, isEmpty);
      expect(first.attemptEvidence, isEmpty);
      await Future<void>.delayed(Duration.zero);
      await Future<void>.delayed(Duration.zero);

      final restored = AppState();
      await restored.load();
      final entry = restored.temporaryDefinitionFor(' Library ');
      expect(entry, isNotNull);
      expect(entry!.definition, '图书馆');
      expect(entry.provider, 'compatible');
      expect(entry.model, 'demo');
      expect(restored.mastery, isEmpty);
      expect(restored.reviewQueue, isEmpty);
      expect(restored.attemptEvidence, isEmpty);
      restored.removeTemporaryDefinition('library');
      expect(restored.temporaryDefinitionFor('library'), isNull);
      expect(restored.mastery, isEmpty);
      expect(restored.reviewQueue, isEmpty);
      expect(restored.attemptEvidence, isEmpty);
    },
  );

  test('preview exposure alone does not add mastery or a review item', () {
    final state = AppState();
    final reviewCount = state.reviewQueue.length;
    final masteryCount = state.mastery.length;

    state.completePreview();

    expect(state.reviewQueue, hasLength(reviewCount));
    expect(state.mastery, hasLength(masteryCount));
    expect(state.lessonStep, LessonStep.listening);
  });

  test(
    'each target records first formal teaching before lesson completion',
    () {
      final state = AppState();
      state.completePreview();
      state.completeListening();

      for (final id in lessonById('a0-01').targetItemIds) {
        expect(state.mastery[id]!.firstTaughtAt, isNotNull);
      }
      expect(state.lessonCanComplete, isFalse);
    },
  );

  test('lesson evidence is task- and target-specific', () {
    final state = AppState();
    final targets = lessonById('a0-01').targetItemIds;
    const segmentId = 'a0-01-a';
    state.completePreview();
    state.completeListening();

    for (final id in targets) {
      expect(
        state.attemptEvidence.any(
          (entry) =>
              entry.itemId == id &&
              entry.taskId == 'lesson-$segmentId-listening' &&
              entry.outcome == EvidenceKind.exposure,
        ),
        isTrue,
      );
    }
    state.completeSpeaking();
    final speaking = state.attemptEvidence.where(
      (entry) => entry.taskId == 'lesson-$segmentId-speaking',
    );
    // Follow-reading is assisted practice for every target, never
    // independent evidence for one of them.
    expect(speaking.map((entry) => entry.itemId), targets);
    expect(
      speaking.every((entry) => entry.outcome == EvidenceKind.assisted),
      isTrue,
    );

    state.completeReading();
    state.completeWriting(rawAnswer: 'Hello. My name is Mia.');
    final writing = state.attemptEvidence.where(
      (entry) => entry.taskId == 'lesson-$segmentId-writing',
    );
    expect(writing.map((entry) => entry.itemId).toSet(), {'A0-W36', 'A0-P01'});
  });

  test('a first-try listening choice is recognition evidence', () {
    final state = AppState();
    state.completePreview();
    state.completeListening(recognized: true);

    for (final id in lessonById('a0-01').targetItemIds) {
      expect(state.mastery[id]!.status, MasteryStatus.recognize);
    }
  });

  test('scene dialogue credits taught items the learner actually used', () {
    final state = AppState();
    state.completePreview();
    state.completeListening();

    state.recordDialogueAttempt(
      taskId: 'dialogue-scene-a0-meet-0',
      rawAnswer: 'Hi! My name is Mia.',
      assisted: false,
      sceneId: 'a0-meet',
    );

    final used = state.attemptEvidence
        .where((entry) => entry.taskId == 'dialogue-scene-a0-meet-0')
        .map((entry) => entry.itemId)
        .toSet();
    expect(used, {'A0-W37', 'A0-P01'});
    expect(state.mastery['A0-P01']!.status, MasteryStatus.use);
    expect(state.mastery['A0-P03']!.status, MasteryStatus.newItem);
  });

  test(
    'mastery rebuild derives first teaching and teaching level from evidence',
    () {
      final state = AppState();
      state.completePreview();
      state.completeListening();
      state.completeSpeaking();
      state.completeReading();
      state.completeWriting(rawAnswer: 'Hello. I am Mia.');
      state.completeLessonDialogue();
      state.completeIndependentAttempt(
        assisted: false,
        rawAnswer: 'Hello. I am Mia.',
      );
      const introduced = 'A0-P01';

      state.mastery.clear();
      state.rebuildMasteryFromEvidence();

      expect(state.mastery[introduced]!.firstTaughtAt, isNotNull);
      // Recalled inside the lesson, not yet used in another situation.
      expect(state.mastery[introduced]!.status, MasteryStatus.recall);
      // The answer never said "Nice to meet you", so that target gets no
      // production evidence from it.
      expect(state.mastery['A0-P03']!.status, MasteryStatus.newItem);
      expect(
        state.mastery[lessonById('a0-01').targetItemIds.first]!.firstTaughtAt,
        isNotNull,
      );
    },
  );

  test('every A0 seed lesson has complete local activities', () {
    expect(a0SeedLessons, hasLength(10));
    for (final lesson in a0SeedLessons) {
      final activity = activityByLessonId(lesson.id);
      expect(lesson.vocabulary, isNotEmpty);
      expect(activity.answers, hasLength(3));
      expect(activity.answers.first, isNotEmpty);
      expect(activity.independentPrompt, isNotEmpty);
      expect(lesson.schemaVersion, '1.0');
      expect(lesson.status, ContentStatus.approved);
      expect(lesson.source, ContentSource.builtInOriginal);
      expect(lesson.targetItemIds, isNotEmpty);
    }
    expect(
      a0SeedLessons.expand((lesson) => lesson.targetItemIds).toSet(),
      containsAll(a0CoreItems.keys),
    );
  });

  test('every A0 seed lesson has a practical grammar reminder', () {
    for (final lesson in a0SeedLessons) {
      expect(grammarNoteForLesson(lesson.id).trim(), isNotEmpty);
    }
  });

  test('A0 lesson segments stay within new-item budget and cover targets', () {
    for (final lesson in a0SeedLessons) {
      final segmented = lesson.segments.expand(
        (segment) => segment.targetItemIds,
      );
      expect(
        lesson.segments.every((segment) => segment.targetItemIds.length <= 8),
        isTrue,
      );
      expect(segmented.toSet(), equals(lesson.targetItemIds.toSet()));
    }
  });

  test('segment completion advances only within its lesson', () {
    final state = AppState();
    state.completeSegment('a0-04', 0);

    expect(state.isSegmentComplete('a0-04-a'), isTrue);
    expect(state.isSegmentComplete('a0-04-b'), isFalse);
    expect(state.activeSegmentIndexFor('a0-04'), 1);
  });

  test('split lesson segments have their own reviewed activities', () {
    for (final lessonId in ['a0-04', 'a0-08']) {
      for (final segment in lessonById(lessonId).segments) {
        expect(a0SegmentActivities, contains(segment.id));
        expect(activityBySegmentId(segment.id, lessonId).listening, isNotEmpty);
      }
    }
    expect(activityBySegmentId('a0-01-a', 'a0-01').writingPrompt, isNotEmpty);
  });

  test('split lesson segments have their own controlled dialogues', () {
    for (final lessonId in ['a0-04', 'a0-08']) {
      for (final segment in lessonById(lessonId).segments) {
        expect(a0SegmentDialogues, contains(segment.id));
        expect(dialogueBySegmentId(segment.id, lessonId).prompts, isNotEmpty);
      }
    }
  });

  test('split lesson segments have reviewed vocabulary and grammar notes', () {
    for (final lessonId in ['a0-04', 'a0-08']) {
      for (final segment in lessonById(lessonId).segments) {
        final vocabulary = vocabularyBySegmentId(segment.id, lessonId);
        expect(vocabulary.map((item) => item.id), segment.previewItemIds);
        expect(vocabulary.every((item) => item.meaning.isNotEmpty), isTrue);
        expect(vocabulary.every((item) => item.example.isNotEmpty), isTrue);
        expect(grammarNoteForSegment(segment.id, lessonId).trim(), isNotEmpty);
      }
    }
  });

  test('split dialogue validators require the current segment content', () {
    expect(matchesSegmentDialogue('a0-04-a', 0, 'zero, one, two'), isTrue);
    expect(matchesSegmentDialogue('a0-04-a', 0, 'hello'), isFalse);
    expect(
      matchesSegmentDialogue('a0-04-c', 0, 'My number is one-three-eight'),
      isTrue,
    );
    expect(matchesSegmentDialogue('a0-04-c', 0, 'one-three-eight'), isFalse);
    expect(matchesSegmentDialogue('a0-08-c', 1, "It is three o'clock"), isTrue);
    expect(matchesSegmentDialogue('a0-08-c', 1, 'It is Monday'), isFalse);
  });

  test('split independent attempts need their taught information', () {
    expect(matchesSegmentIndependent('a0-04-a', 'zero, one, two'), isTrue);
    expect(matchesSegmentIndependent('a0-04-a', 'zero, one'), isFalse);
    expect(matchesSegmentIndependent('a0-08-b', 'It is Friday.'), isTrue);
    expect(matchesSegmentIndependent('a0-08-b', 'It is Monday.'), isFalse);
  });

  test('single-segment independent attempts reject off-task answers', () {
    const offTask = 'abc';
    for (final lessonId in [
      'a0-01',
      'a0-02',
      'a0-03',
      'a0-05',
      'a0-06',
      'a0-07',
      'a0-09',
      'a0-10',
    ]) {
      expect(
        matchesSegmentIndependent('$lessonId-a', offTask),
        isFalse,
        reason: lessonId,
      );
    }
    expect(
      matchesSegmentIndependent('a0-01-a', "Hi, I'm Mia. Nice to meet you."),
      isTrue,
    );
    expect(matchesSegmentIndependent('a0-01-a', "Hi, I'm Mia."), isFalse);
    expect(matchesSegmentIndependent('a0-05-a', "It's a pen."), isTrue);
    expect(
      matchesSegmentIndependent(
        'a0-06-a',
        "I'm from Guangzhou. Where are you from?",
      ),
      isTrue,
    );
    expect(
      matchesSegmentIndependent('a0-06-a', "I'm from Guangzhou."),
      isFalse,
    );
    expect(
      matchesSegmentIndependent(
        'a0-10-a',
        "I'm Mia. I'm from Guangzhou. I like tea. Do you like tea?",
      ),
      isTrue,
    );
  });

  test('each free scene keeps its own daily recap', () {
    final state = AppState();

    state.addDialogueRecap('My name is Alex.');
    state.addDialogueRecap('It is Monday.', sceneId: 'a0-plan');

    expect(
      state.reviewQueue.where(
        (item) => item.id.startsWith('dialogue-a0-meet-'),
      ),
      hasLength(1),
    );
    final plan = state.reviewQueue.singleWhere(
      (item) => item.id.startsWith('dialogue-a0-plan-'),
    );
    expect(plan.prompt, sceneById('a0-plan').recapPrompt);
  });

  test('scenes open with their lessons and rotate the recommendation', () {
    final state = AppState();
    expect(a0Scenes.where(state.isSceneUnlocked).map((scene) => scene.id), [
      'a0-meet',
    ]);
    state.completedLessonIds.addAll(['a0-01', 'a0-02', 'a0-03', 'a0-04']);
    expect(state.recommendedScene.id, 'a0-number');
    state.addDialogueRecap('My number is one two three.', sceneId: 'a0-number');
    expect(state.recommendedScene.id, 'a0-meet');
  });

  test('completed independent dialogue creates one daily non-core recap', () {
    final state = AppState();

    state.addDialogueRecap('My name is Alex.');
    state.addDialogueRecap('My name is Mia.');

    final recap = state.reviewQueue.where(
      (item) => item.id.startsWith('dialogue-a0-meet-'),
    );
    expect(recap, hasLength(1));
    expect(recap.single.target, 'My name is Alex.');
    expect(a0CoreItems, isNot(contains(recap.single.id)));
  });

  test('A0 upgrade denominator is the frozen 60-item core list', () {
    expect(a0CoreItems, hasLength(60));
    expect(a0CoreItems['A0-W01'], 'zero');
    expect(a0CoreItems['A0-P20'], 'Please say that again.');
  });

  test('the ten A0 lessons introduce every frozen core item to review', () {
    final state = AppState();
    for (final lesson in a0SeedLessons) {
      state.openLesson(lesson.id);
      for (var segment = 0; segment < lesson.segments.length; segment++) {
        state.completePreview();
        state.completeListening();
        state.completeSpeaking();
        state.completeReading();
        state.completeWriting(assisted: true);
        state.completeLessonDialogue();
        state.completeIndependentAttempt(assisted: true);
        state.finishCurrentLessonSegment();
      }
    }

    expect(state.mastery.keys.where(a0CoreItems.containsKey), hasLength(60));
    expect(
      state.reviewQueue.map((item) => item.id).toSet(),
      containsAll(a0CoreItems.keys),
    );
    final fromReview = state.reviewQueue.firstWhere(
      (item) => item.id == 'A0-P12',
    );
    expect(fromReview.prompt, contains('来自哪里'));
    expect(fromReview.prompt, isNot(contains("I'm from")));
  });

  test('A0 pass requires two different, spaced four-skill assessments', () {
    final state = AppState();
    for (final entry in a0CoreItems.entries) {
      state.mastery[entry.key] = MasteryItem(
        id: entry.key,
        label: entry.value,
        status: MasteryStatus.master,
        evidence: const [EvidenceKind.independentSuccess],
      );
    }
    const results = {
      AssessmentSkill.listening: true,
      AssessmentSkill.speaking: true,
      AssessmentSkill.reading: true,
      AssessmentSkill.writing: true,
    };
    final now = DateTime.now();
    state.recordAssessment(
      AssessmentRecord(
        packId: 'A',
        completedAt: now.subtract(const Duration(hours: 25)),
        results: results,
      ),
    );
    expect(state.a0Passed, isFalse);
    state.recordAssessment(
      AssessmentRecord(packId: 'B', completedAt: now, results: results),
    );
    expect(state.a0Passed, isTrue);
  });

  test('both A0 assessment packs meet the documented task blueprint', () {
    expect(a0AssessmentPacks, hasLength(2));
    for (final pack in a0AssessmentPacks) {
      expect(pack.forSkill(AssessmentSkill.listening), hasLength(10));
      expect(pack.forSkill(AssessmentSkill.reading), hasLength(5));
      expect(pack.forSkill(AssessmentSkill.writing), hasLength(5));
      expect(pack.forSkill(AssessmentSkill.speaking), hasLength(8));
      expect(
        pack.tasks.map((task) => task.id).toSet(),
        hasLength(pack.tasks.length),
      );
    }
  });

  test('open A0 assessment tasks require their actual information slots', () {
    final pack = a0AssessmentPacks.first;
    final writing = pack.forSkill(AssessmentSkill.writing);
    final speaking = pack.forSkill(AssessmentSkill.speaking);
    expect(checkOpenAssessmentAnswer(writing[1], 'Hong Kong.'), isFalse);
    expect(
      checkOpenAssessmentAnswer(writing[1], "I'm from Hong Kong."),
      isTrue,
    );
    expect(checkOpenAssessmentAnswer(speaking[2], 'one.'), isFalse);
    expect(checkOpenAssessmentAnswer(speaking[2], 'one-three-eight.'), isTrue);
    expect(
      checkOpenAssessmentAnswer(
        speaking.first,
        'Hello. I am Alex. I am from Beijing. I like tea. What do you like?',
      ),
      isTrue,
    );
    expect(
      checkOpenAssessmentAnswer(speaking[5], "It's three o'clock."),
      isTrue,
    );
    expect(
      checkOpenAssessmentAnswer(speaking[5], 'It is two o’clock.'),
      isTrue,
    );
    expect(
      checkOpenAssessmentAnswer(speaking[6], 'Please speak slowly.'),
      isTrue,
    );
    expect(checkOpenAssessmentAnswer(speaking[6], 'Repeat, please.'), isTrue);
  });

  test('finishLesson advances activeLessonId to next available lesson', () {
    final state = AppState();
    expect(state.activeLessonId, 'a0-01');
    state.completePreview();
    state.completeListening();
    state.completeSpeaking();
    state.completeReading();
    state.completeWriting(assisted: false);
    state.completeLessonDialogue();
    state.completeIndependentAttempt(assisted: false);
    expect(state.lessonCanComplete, isTrue);
    state.finishLesson();

    expect(state.completedLessonIds, contains('a0-01'));
    expect(state.activeLessonId, 'a0-02');
  });

  void finishActiveLesson(AppState state) {
    state.completePreview();
    state.completeListening();
    state.completeSpeaking();
    state.completeReading();
    state.completeWriting(assisted: true);
    state.completeLessonDialogue();
    state.completeIndependentAttempt(assisted: true);
    state.finishLesson();
  }

  test('switching lessons clears step flags from the previous lesson', () {
    final state = AppState();
    state.completePreview();
    state.completeListening();
    state.completeSpeaking();
    state.completeReading();
    state.completeWriting(assisted: true);
    state.completeLessonDialogue();
    state.completeIndependentAttempt(assisted: true);
    state.completedLessonIds.add('a0-01');

    state.openLesson('a0-02');

    expect(state.lessonCanComplete, isFalse);
    expect(state.lessonListeningComplete, isFalse);
  });

  test('placement opens its start lesson without passing earlier ones', () {
    final state = AppState();
    state.setPlacementStartLesson('a0-02');

    expect(state.activeLessonId, 'a0-02');
    expect(state.isLessonUnlocked('a0-01'), isTrue);
    expect(state.isLessonUnlocked('a0-02'), isTrue);
    expect(state.isLessonUnlocked('a0-03'), isFalse);
    expect(state.completedLessonIds, isEmpty);

    finishActiveLesson(state);
    expect(state.activeLessonId, 'a0-03');
  });

  test('after the last lesson the learner is sent to unfinished lessons', () {
    final state = AppState();
    state.setPlacementStartLesson('a0-02');
    for (var index = 1; index < a0SeedLessons.length; index++) {
      final lesson = a0SeedLessons[index];
      state.openLesson(lesson.id);
      for (var segment = 0; segment < lesson.segments.length; segment++) {
        state.completeSegment(lesson.id, segment);
      }
      finishActiveLesson(state);
    }
    expect(state.activeLessonId, 'a0-01');
    expect(state.allLessonsComplete, isFalse);

    finishActiveLesson(state);
    expect(state.allLessonsComplete, isTrue);
    expect(state.a0AssessmentReady, isFalse);
    expect(state.nextAssessmentPackId, 'A0-E1');
  });

  test(
    'a passed assessment skill remains valid during the seven-day retest window',
    () {
      final state = AppState();
      final now = DateTime.now();
      state.recordAssessment(
        AssessmentRecord(
          packId: 'A0-E1',
          completedAt: now.subtract(const Duration(days: 1)),
          results: const {
            AssessmentSkill.listening: true,
            AssessmentSkill.speaking: false,
            AssessmentSkill.reading: false,
            AssessmentSkill.writing: false,
          },
        ),
      );
      final merged = state.recordAssessment(
        AssessmentRecord(
          packId: 'A0-E1',
          completedAt: now,
          results: const {
            AssessmentSkill.listening: false,
            AssessmentSkill.speaking: true,
            AssessmentSkill.reading: false,
            AssessmentSkill.writing: false,
          },
        ),
      );
      expect(merged.results[AssessmentSkill.listening], isTrue);
      expect(merged.results[AssessmentSkill.speaking], isTrue);
    },
  );

  test('a technical speaking gap remains pending instead of failed', () {
    final state = AppState();
    final record = state.recordAssessment(
      AssessmentRecord(
        packId: 'A0-E1',
        completedAt: DateTime.now(),
        results: const {
          AssessmentSkill.listening: true,
          AssessmentSkill.reading: true,
          AssessmentSkill.writing: true,
          AssessmentSkill.speaking: false,
        },
        pendingSkills: const {AssessmentSkill.speaking},
      ),
    );
    expect(record.pendingSkills, contains(AssessmentSkill.speaking));
    expect(record.failedSkills, isNot(contains(AssessmentSkill.speaking)));
  });

  test('replacement assessment packs use a different task value set', () {
    expect(a0ReplacementPacks, hasLength(2));
    expect(replacementFor('A0-E1')!.id, 'A0-E1R');
    expect(
      a0ReplacementPacks.first.tasks.first.audio,
      isNot(a0AssessmentPacks.first.tasks.first.audio),
    );
  });

  test(
    'replacement results merge into their original seven-day skill window',
    () {
      final state = AppState();
      final now = DateTime.now();
      state.recordAssessment(
        AssessmentRecord(
          packId: 'A0-E1',
          completedAt: now.subtract(const Duration(days: 1)),
          results: const {AssessmentSkill.listening: true},
        ),
      );
      final merged = state.recordAssessment(
        AssessmentRecord(
          packId: 'A0-E1R',
          completedAt: now,
          results: const {AssessmentSkill.speaking: true},
        ),
      );
      expect(merged.packId, 'A0-E1');
      expect(merged.results[AssessmentSkill.listening], isTrue);
      expect(merged.results[AssessmentSkill.speaking], isTrue);
    },
  );

  test('assessment draft survives a local-state restore', () async {
    SharedPreferences.setMockInitialValues({});
    final first = AppState();
    await first.load();
    first.saveAssessmentDraft(
      const AssessmentDraft(
        packId: 'A0-E1',
        taskIndex: 4,
        results: {'A0-A-L1': true},
      ),
    );
    await Future<void>.delayed(Duration.zero);
    await Future<void>.delayed(Duration.zero);
    final restored = AppState();
    await restored.load();
    expect(restored.assessmentDraft!.packId, 'A0-E1');
    expect(restored.assessmentDraft!.taskIndex, 4);
    expect(restored.assessmentDraft!.results['A0-A-L1'], isTrue);
  });

  test('review attempt evidence survives a local-state restore', () async {
    SharedPreferences.setMockInitialValues({});
    final first = AppState();
    await first.load();
    final item = dueItem();
    first.reviewQueue.add(item);
    first.completeReview(
      item,
      assisted: true,
      rawAnswer: "I'm from Hong Kong.",
    );
    await Future<void>.delayed(Duration.zero);
    await Future<void>.delayed(Duration.zero);

    final restored = AppState();
    await restored.load();
    expect(restored.attemptEvidence, hasLength(1));
    expect(restored.attemptEvidence.single.itemId, 'A0-P12');
    expect(restored.attemptEvidence.single.rawAnswer, "I'm from Hong Kong.");
    expect(restored.attemptEvidence.single.assisted, isTrue);
    expect(restored.attemptEvidence.single.outcome, EvidenceKind.assisted);
  });

  test('clearing progress also removes local learning evidence', () {
    final state = AppState();
    final item = dueItem();
    state.reviewQueue.add(item);
    state.completeReview(item, assisted: false, rawAnswer: "I'm from London.");

    state.clearProgress();

    expect(state.attemptEvidence, isEmpty);
    expect(state.reviewQueue, isEmpty);
    expect(state.mastery, isEmpty);
  });

  test('clearing progress keeps AI service configuration', () {
    final state = AppState();
    state.setAiProvider(AiProviderType.compatible);
    state.saveAiConfiguration(
      endpoint: 'https://example.test/v1',
      model: 'test-model',
    );

    state.clearProgress();

    expect(state.aiProvider, AiProviderType.compatible);
    expect(state.aiEndpoint, 'https://example.test/v1');
    expect(state.aiModel, 'test-model');
  });

  test('lesson dialogue draft survives a local-state restore', () async {
    SharedPreferences.setMockInitialValues({});
    final first = AppState();
    await first.load();
    first.saveDialogueDraft(
      const DialogueDraft(
        lessonId: 'a0-03',
        stage: 2,
        usedHelp: true,
        turns: [
          DialogueTurn(text: 'Hi! How are you?', isLearner: false),
          DialogueTurn(text: 'I am good.', isLearner: true),
        ],
      ),
    );
    await Future<void>.delayed(Duration.zero);
    await Future<void>.delayed(Duration.zero);

    final restored = AppState();
    await restored.load();
    expect(restored.dialogueDraft!.lessonId, 'a0-03');
    expect(restored.dialogueDraft!.stage, 2);
    expect(restored.dialogueDraft!.usedHelp, isTrue);
    expect(restored.dialogueDraft!.turns, hasLength(2));
    expect(restored.dialogueDraft!.turns.last.isLearner, isTrue);
  });
}