import 'dart:async';
import 'dart:convert';
import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:shared_preferences/shared_preferences.dart';

import 'models.dart';
import 'a0_core.dart';
import 'generated_content.dart';
import 'local_store.dart';
import 'seed_courses.dart';
import 'ai_config.dart';
import 'ai_service.dart';
import 'sherpa_stt_service.dart';
import 'sync/sync_coordinator.dart';

part 'app_state_ai_content.dart';
part 'app_state_assessment.dart';
part 'app_state_lesson.dart';
part 'app_state_review.dart';
part 'app_state_snapshot.dart';

/// Everything the app persists. Behaviour lives in the domain mixins that
/// [AppState] composes.
abstract class _AppStateData extends ChangeNotifier {
  LearningGoal goal = LearningGoal.dailyLife;
  int dailyMinutes = 20;
  PlacementLevel placement = PlacementLevel.beginner;
  bool onboardingComplete = false;
  bool showChineseHints = true;
  bool keepRecordings = false;
  int completedLessons = 0;
  String activeLessonId = 'a0-01';
  final Set<String> completedLessonIds = {};
  final Set<String> completedSegmentIds = {};
  final Set<String> reportedAiVariantKeys = {};
  final Map<String, int> activeSegmentIndexes = {};
  final List<AssessmentRecord> assessments = [];
  AssessmentDraft? assessmentDraft;
  DialogueDraft? dialogueDraft;

  /// The free "初次见面" scene keeps its own slot, so resuming a scene never
  /// overwrites an unfinished lesson dialogue.
  DialogueDraft? sceneDialogueDraft;
  LessonStep lessonStep = LessonStep.preview;
  int previewIndex = 0;
  bool lessonListeningComplete = false;
  bool lessonSpeakingComplete = false;
  bool lessonReadingComplete = false;
  bool lessonWritingComplete = false;
  bool lessonDialogueComplete = false;
  bool independentAttemptComplete = false;
  bool independentAttemptAssisted = false;
  bool independentAttemptSpoken = false;
  String lessonWritingDraft = '';
  String independentAttemptDraft = '';
  AiProviderType aiProvider = AiProviderType.mock;
  String aiEndpoint = '';
  String aiModel = '';

  AiConfigFile get aiConfig =>
      AiConfigFile(provider: aiProvider, endpoint: aiEndpoint, model: aiModel);
  String? cachedAdaptiveLessonRaw;
  DateTime? cachedAdaptiveLessonAuditedAt;
  String? cachedAdaptiveLessonAuditor;
  String? adaptiveLessonDraftId;
  int adaptiveLessonDraftIndex = 0;
  String adaptiveLessonDraftAnswer = '';
  bool adaptiveLessonDraftReferenceShown = false;
  bool adaptiveLessonDraftUsedVoice = false;
  bool adaptiveLessonDraftTranscriptEdited = false;
  bool adaptiveLessonDraftTranscriptConfirmed = false;
  String adaptiveLessonDraftOriginalTranscript = '';
  String? adaptiveLessonDraftRecordingPath;
  final Set<String> reportedAdaptiveLessonIds = {};
  final Map<String, TemporaryLexiconEntry> temporaryLexicon = {};
  final Map<String, SentenceAnalysisResult> sentenceAnalyses = {};

  final List<ReviewItem> reviewQueue = [];
  final List<AttemptEvidence> attemptEvidence = [];

  final Map<String, MasteryItem> mastery = {};

  void _syncInBackground();
}

class AppState extends _AppStateData
    with _ReviewAndMastery, _LessonProgress, _AssessmentProgress, _AiContent {
  static const _storageKey = 'learning_state_v1';
  bool isLoaded = false;
  bool _writing = false;
  bool _dirty = false;

  // Widget/unit tests keep using the mock preference backend. Production uses
  // SQLite through Drift; this also prevents test cases sharing a real device
  // database between runs.
  bool get _usesLegacyTestStore =>
      Platform.environment['FLUTTER_TEST'] == 'true';

  AppState() {
    addListener(_persist);
  }

  Future<void> load() async {
    try {
      unawaited(SherpaSttService.instance.initialize());
      final config = await AiConfigFile.loadFromAsset();
      if (config != null) {
        if (config.apiKey != null && config.apiKey!.trim().isNotEmpty) {
          AiService.instance.setFallbackApiKey(config.apiKey);
        }
        if (aiEndpoint.isEmpty && config.endpoint.isNotEmpty) {
          aiEndpoint = config.endpoint;
        }
        if (aiModel.isEmpty && config.model.isNotEmpty) {
          aiModel = config.model;
        }
        if (aiProvider == AiProviderType.mock &&
            config.provider != AiProviderType.mock) {
          aiProvider = config.provider;
        }
      }
      String? raw;
      if (!_usesLegacyTestStore) {
        raw = await LocalSnapshotStore.instance.read();
      }
      if (raw == null) {
        final preferences = await SharedPreferences.getInstance();
        raw = preferences.getString(_storageKey);
        // One-time migration from builds that used SharedPreferences only.
        if (raw != null && !_usesLegacyTestStore) {
          await LocalSnapshotStore.instance.write(raw);
        }
      }
      if (raw != null) _restore(jsonDecode(raw) as Map<String, dynamic>);
      if (config != null) {
        if (aiEndpoint.isEmpty && config.endpoint.isNotEmpty) {
          aiEndpoint = config.endpoint;
        }
        if (aiModel.isEmpty && config.model.isNotEmpty) {
          aiModel = config.model;
        }
        if (aiProvider == AiProviderType.mock &&
            config.provider != AiProviderType.mock &&
            raw == null) {
          aiProvider = config.provider;
        }
      }
    } catch (_) {
      // A corrupt local cache must never prevent access to offline lessons.
    } finally {
      isLoaded = true;
      notifyListeners();
    }
  }

  Future<bool> reloadAiConfigFromAsset() async {
    final config = await AiConfigFile.loadFromAsset();
    if (config == null) return false;
    aiProvider = config.provider;
    aiEndpoint = config.endpoint;
    aiModel = config.model;
    if (config.apiKey != null && config.apiKey!.trim().isNotEmpty) {
      AiService.instance.setFallbackApiKey(config.apiKey);
    }
    notifyListeners();
    return true;
  }

  void _persist() {
    if (!isLoaded) return;
    _dirty = true;
    if (_writing) return;
    _writing = true;
    _dirty = false;
    _writeSnapshot(
      jsonEncode(_toSnapshotJson()),
    ).catchError((_) => false).whenComplete(() {
      _writing = false;
      if (_dirty) _persist();
    });
  }

  Future<void> _writeSnapshot(String payload) async {
    if (_usesLegacyTestStore) {
      final preferences = await SharedPreferences.getInstance();
      await preferences.setString(_storageKey, payload);
      return;
    }
    await LocalSnapshotStore.instance.write(payload);
  }

  void finishOnboarding() {
    onboardingComplete = true;
    notifyListeners();
    _syncInBackground();
  }

  void setGoal(LearningGoal value) {
    goal = value;
    notifyListeners();
  }

  void setDailyMinutes(int value) {
    dailyMinutes = value;
    notifyListeners();
  }

  void setPlacement(PlacementLevel value) {
    placement = value;
    notifyListeners();
  }

  void setAiProvider(AiProviderType value) {
    aiProvider = value;
    notifyListeners();
  }

  void saveAiConfiguration({required String endpoint, required String model}) {
    aiEndpoint = endpoint.trim();
    aiModel = model.trim();
    notifyListeners();
  }

  void toggleChineseHints(bool value) {
    showChineseHints = value;
    notifyListeners();
  }

  void toggleKeepRecordings(bool value) {
    keepRecordings = value;
    notifyListeners();
  }

  void clearProgress() {
    completedLessons = 0;
    activeLessonId = 'a0-01';
    completedLessonIds.clear();
    completedSegmentIds.clear();
    reportedAiVariantKeys.clear();
    activeSegmentIndexes.clear();
    reviewQueue.clear();
    attemptEvidence.clear();
    cachedAdaptiveLessonRaw = null;
    cachedAdaptiveLessonAuditedAt = null;
    cachedAdaptiveLessonAuditor = null;
    adaptiveLessonDraftId = null;
    adaptiveLessonDraftIndex = 0;
    adaptiveLessonDraftAnswer = '';
    adaptiveLessonDraftReferenceShown = false;
    adaptiveLessonDraftUsedVoice = false;
    adaptiveLessonDraftTranscriptEdited = false;
    adaptiveLessonDraftTranscriptConfirmed = false;
    adaptiveLessonDraftOriginalTranscript = '';
    adaptiveLessonDraftRecordingPath = null;
    reportedAdaptiveLessonIds.clear();
    assessments.clear();
    assessmentDraft = null;
    dialogueDraft = null;
    sceneDialogueDraft = null;
    lessonStep = LessonStep.preview;
    previewIndex = 0;
    lessonListeningComplete = false;
    lessonSpeakingComplete = false;
    lessonReadingComplete = false;
    lessonWritingComplete = false;
    lessonDialogueComplete = false;
    independentAttemptComplete = false;
    independentAttemptAssisted = false;
    independentAttemptSpoken = false;
    mastery.clear();
    notifyListeners();
  }

  @override
  void _syncInBackground() {
    SyncCoordinator.instance.triggerBackgroundSync(this);
  }
}