import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../../core/utils/app_logger.dart';
import '../../data/models/socratic_checkpoint_model.dart';
import '../../data/models/subject_model.dart';
import '../../data/repositories/curriculum_repository.dart';

abstract class VideoPlaybackState {}

class VideoPlaybackInitial extends VideoPlaybackState {}
class VideoPlaybackLoading extends VideoPlaybackState {}

class VideoPlaybackReady extends VideoPlaybackState {
  final LessonPlaybackData playbackData;
  final CurriculumLessonItemModel? lessonItem;
  final SubjectModel? subject;
  final int currentPositionSeconds;
  final bool isPlaying;
  final SocraticCheckpointModel? activeCheckpoint;
  final bool isCheckpointPassed;
  final String? remediationNotice;
  final double readinessBonusAdded;
  final Set<int> passedCheckpointIds;

  VideoPlaybackReady({
    required this.playbackData,
    this.lessonItem,
    this.subject,
    this.currentPositionSeconds = 0,
    this.isPlaying = true,
    this.activeCheckpoint,
    this.isCheckpointPassed = false,
    this.remediationNotice,
    this.readinessBonusAdded = 0.0,
    this.passedCheckpointIds = const {},
  });

  VideoPlaybackReady copyWith({
    LessonPlaybackData? playbackData,
    CurriculumLessonItemModel? lessonItem,
    SubjectModel? subject,
    int? currentPositionSeconds,
    bool? isPlaying,
    SocraticCheckpointModel? activeCheckpoint,
    bool? isCheckpointPassed,
    String? remediationNotice,
    double? readinessBonusAdded,
    Set<int>? passedCheckpointIds,
    bool clearActiveCheckpoint = false,
  }) {
    return VideoPlaybackReady(
      playbackData: playbackData ?? this.playbackData,
      lessonItem: lessonItem ?? this.lessonItem,
      subject: subject ?? this.subject,
      currentPositionSeconds: currentPositionSeconds ?? this.currentPositionSeconds,
      isPlaying: isPlaying ?? this.isPlaying,
      activeCheckpoint: clearActiveCheckpoint ? null : (activeCheckpoint ?? this.activeCheckpoint),
      isCheckpointPassed: isCheckpointPassed ?? this.isCheckpointPassed,
      remediationNotice: remediationNotice,
      readinessBonusAdded: readinessBonusAdded ?? this.readinessBonusAdded,
      passedCheckpointIds: passedCheckpointIds ?? this.passedCheckpointIds,
    );
  }
}

class VideoPlaybackError extends VideoPlaybackState {
  final String message;
  VideoPlaybackError(this.message);
}

class VideoPlaybackCubit extends Cubit<VideoPlaybackState> {
  final CurriculumRepository _repo;
  int _lastObservedPosition = -1;
  String? _watchSessionId;
  int _watchSequence = 1;
  int _lastWatchEventPosition = 0;

  VideoPlaybackCubit({CurriculumRepository? repo})
      : _repo = repo ?? CurriculumRepository(),
        super(VideoPlaybackInitial());

  String _getLessonStorageKey(CurriculumLessonItemModel? lesson, {String? fallbackId}) {
    if (lesson?.markdownFilePath != null && lesson!.markdownFilePath!.isNotEmpty) {
      return lesson.markdownFilePath!.replaceAll(RegExp(r'[^a-zA-Z0-9_]'), '_');
    }
    if (lesson?.id != null && lesson!.id.isNotEmpty) {
      return lesson.id.replaceAll(RegExp(r'[^a-zA-Z0-9_]'), '_');
    }
    return fallbackId ?? 'lesson_default';
  }

  Future<void> loadLesson(CurriculumLessonItemModel lesson, {SubjectModel? subject, String? selectedVideoVersionId}) async {
    AppLogger.log('Loading Socratic playback for lesson: ${lesson.title}', tag: 'VIDEO_CUBIT');
    _lastObservedPosition = -1;
    emit(VideoPlaybackLoading());
    final storageKey = _getLessonStorageKey(lesson);

    try {
      final versionId = lesson.curriculumLessonId;
      if (versionId == null || versionId.isEmpty) {
        throw StateError('هذا الدرس غير منشور بعد ضمن حزمة المحتوى المعتمدة.');
      }
      final published = await _repo.getPublishedLessonVideos(versionId);
      if (published.isEmpty) throw StateError('لا توجد حصة منشورة ومصرح بها لهذا الدرس بعد.');
      // Selection is performed in the lesson screen when several teachers exist.
      var playback = await _repo.getVideoVersionPlayback(selectedVideoVersionId ?? published.first.videoVersionId);
      if (playback.videoUrl.isEmpty) {
        throw StateError('لم يربط الخادم فيديو R2 بهذا الدرس بعد.');
      }
      
      _watchSessionId = null; _watchSequence = 1; _lastWatchEventPosition = 0;
      if (playback.videoVersionId != null && playback.videoVersionId!.isNotEmpty) {
        try { _watchSessionId = await _repo.startWatchSession(playback.videoVersionId!); } catch (_) {}
      }

      // Load saved resume position strictly per video
      int resumePos = playback.lastPositionSeconds ?? 0;
      Set<int> passedIds = {};
      try {
        final prefs = await SharedPreferences.getInstance();
        final localPos = prefs.getInt('saved_video_pos_$storageKey') ?? 0;
        if (localPos > resumePos) resumePos = localPos;
        final savedPassed = prefs.getStringList('passed_checkpoints_$storageKey') ?? [];
        passedIds = savedPassed.map((s) => int.tryParse(s) ?? 0).where((id) => id > 0).toSet();
      } catch (_) {}

      emit(VideoPlaybackReady(
        playbackData: playback,
        lessonItem: lesson,
        subject: subject,
        currentPositionSeconds: resumePos,
        passedCheckpointIds: passedIds,
        isPlaying: true,
      ));
    } catch (e) {
      AppLogger.error('Playback API unavailable (${lesson.title})', error: e, tag: 'VIDEO_CUBIT');
      emit(VideoPlaybackError(e.toString()));
    }
  }

  void updatePosition(int seconds) {
    final currentState = state;
    if (currentState is VideoPlaybackReady && currentState.activeCheckpoint == null) {
      // Check if natural forward playback reaches a Socratic checkpoint
      for (var cp in currentState.playbackData.checkpoints) {
        final hitCheckpoint = !currentState.passedCheckpointIds.contains(cp.id) &&
            _lastObservedPosition < cp.timestampSeconds &&
            seconds >= cp.timestampSeconds &&
            (seconds - _lastObservedPosition).abs() <= 3; // Natural sequential playback

        if (hitCheckpoint) {
          AppLogger.log('🚨 Socratic Checkpoint Triggered at ${cp.timestampSeconds}s! (${cp.questionText})', tag: 'SOCRATIC_ENGINE');
          _lastObservedPosition = cp.timestampSeconds;
          emit(currentState.copyWith(
            currentPositionSeconds: cp.timestampSeconds,
            isPlaying: false, // Freeze video playback
            activeCheckpoint: cp,
          ));
          return;
        }
      }

      _lastObservedPosition = seconds;
      emit(currentState.copyWith(currentPositionSeconds: seconds));
    }
  }

  Future<void> endWatchSession() async {
    final session = _watchSessionId;
    if (session == null) return;
    _watchSessionId = null;
    try { await _repo.recordWatchEvent(session, ++_watchSequence, 'end', _lastObservedPosition.clamp(0, 1 << 31) * 1000); } catch (_) {}
  }

  void togglePlayPause() {
    final currentState = state;
    if (currentState is VideoPlaybackReady && currentState.activeCheckpoint == null) {
      emit(currentState.copyWith(isPlaying: !currentState.isPlaying));
    }
  }

  void seekTo(int seconds) {
    final currentState = state;
    if (currentState is VideoPlaybackReady) {
      // Find the earliest unpassed checkpoint before or at this target
      SocraticCheckpointModel? blockingCheckpoint;
      for (var cp in currentState.playbackData.checkpoints) {
        if (!currentState.passedCheckpointIds.contains(cp.id) && seconds > cp.timestampSeconds) {
          if (blockingCheckpoint == null || cp.timestampSeconds < blockingCheckpoint.timestampSeconds) {
            blockingCheckpoint = cp;
          }
        }
      }

      // If user tries to skip past an unpassed checkpoint, snap precisely to that checkpoint
      final actualSeek = blockingCheckpoint != null ? blockingCheckpoint.timestampSeconds : seconds;
      _lastObservedPosition = actualSeek;

      emit(currentState.copyWith(
        currentPositionSeconds: actualSeek,
        activeCheckpoint: blockingCheckpoint,
        isPlaying: blockingCheckpoint == null ? currentState.isPlaying : false,
      ));
    }
  }

  Future<void> saveProgress({required int positionSeconds, required int watchedSeconds}) async {
    final currentState = state;
    if (currentState is! VideoPlaybackReady) return;
    try {
      final storageKey = _getLessonStorageKey(currentState.lessonItem, fallbackId: '${currentState.playbackData.lessonId}');
      final prefs = await SharedPreferences.getInstance();
      await prefs.setInt('saved_video_pos_$storageKey', positionSeconds);
      if (currentState.passedCheckpointIds.isNotEmpty) {
        await prefs.setStringList(
          'passed_checkpoints_$storageKey',
          currentState.passedCheckpointIds.map((id) => id.toString()).toList(),
        );
      }
      if (currentState.playbackData.lessonId > 0) {
        await _repo.saveProgress(lessonId: currentState.playbackData.lessonId, positionSeconds: positionSeconds, watchedSeconds: watchedSeconds);
      }
      if (_watchSessionId != null && positionSeconds - _lastWatchEventPosition >= 30) {
        _watchSequence++; _lastWatchEventPosition = positionSeconds;
        await _repo.recordWatchEvent(_watchSessionId!, _watchSequence, 'heartbeat', positionSeconds * 1000);
      }
    } catch (e) {
      AppLogger.log('Progress sync deferred: $e', tag: 'VIDEO_CUBIT');
    }
  }

  /// Submit Socratic Checkpoint Answer
  bool submitCheckpointAnswer(SocraticOptionModel selectedOption) {
    final currentState = state;
    if (currentState is VideoPlaybackReady && currentState.activeCheckpoint != null) {
      final cp = currentState.activeCheckpoint!;
      
      if (selectedOption.isCorrect) {
        // Correct Answer -> Reward readiness score (+0.5%) & resume video
        AppLogger.log('✅ Correct answer! Rewarding +0.5% readiness.', tag: 'SOCRATIC_ENGINE');
        final updatedPassed = Set<int>.from(currentState.passedCheckpointIds)..add(cp.id);
        _lastObservedPosition = cp.timestampSeconds;

        // Persist passed checkpoint for this specific video
        final storageKey = _getLessonStorageKey(currentState.lessonItem, fallbackId: '${currentState.playbackData.lessonId}');
        SharedPreferences.getInstance().then((prefs) {
          prefs.setStringList('passed_checkpoints_$storageKey', updatedPassed.map((id) => id.toString()).toList());
        }).catchError((_) {});

        emit(currentState.copyWith(
          clearActiveCheckpoint: true,
          isPlaying: true,
          readinessBonusAdded: currentState.readinessBonusAdded + 0.5,
          passedCheckpointIds: updatedPassed,
          remediationNotice: 'إجابة نموذجية ممتازة! تم تعزيز مؤشر الجاهزية (+0.5%) 🚀',
        ));
        if (cp.id > 0) {
          _repo.submitCheckpoint(examId: cp.id, questionId: cp.questionId, optionId: selectedOption.id).catchError((e) {
            AppLogger.log('Checkpoint sync deferred: $e', tag: 'VIDEO_CUBIT');
          });
        }
        return true;
      } else {
        // Wrong Answer -> Socratic Productive Struggle: Rewind video by N seconds from checkpoint
        final rewindTo = (cp.timestampSeconds - cp.rewindSecondsOnFail).clamp(0, currentState.playbackData.durationSeconds);
        _lastObservedPosition = rewindTo;
        AppLogger.log('❌ Incorrect answer. Socratic remediation: Rewinding to ${rewindTo}s.', tag: 'SOCRATIC_ENGINE');
        emit(currentState.copyWith(
          clearActiveCheckpoint: true,
          currentPositionSeconds: rewindTo,
          isPlaying: true,
          remediationNotice: 'تعثرت في هذا المفهوم. تم إرجاع الفيديو ${cp.rewindSecondsOnFail} ثانية لإعادة الاستماع بتركيز 🔄',
        ));
        if (cp.id > 0 && cp.questionId > 0) {
          _repo.submitCheckpoint(examId: cp.id, questionId: cp.questionId, optionId: selectedOption.id).catchError((e) {
            AppLogger.log('Checkpoint sync deferred: $e', tag: 'VIDEO_CUBIT');
          });
        }
        return false;
      }
    }
    return false;
  }
}