import 'dart:convert';

import 'package:http/http.dart' as http;
import 'package:practice_engine/practice_engine.dart';

import '../env.dart';
import 'api_auth_service.dart';

/// Sync metadata for a deck that came from the API (server id, copy source, etc.).
class DeckSyncMetadata {
  final String serverDeckId;
  final String? ownerId;
  final String? copiedFromDeckId;
  final int? copiedFromVersion;
  final bool published;
  final bool needsUpdate;

  const DeckSyncMetadata({
    required this.serverDeckId,
    this.ownerId,
    this.copiedFromDeckId,
    this.copiedFromVersion,
    this.published = false,
    this.needsUpdate = false,
  });
}

/// Remote deck list item (from GET /api/decks/mine or /api/decks/published).
class RemoteDeckListItem {
  final String id;
  final String title;
  final String description;
  final int questionCount;
  final bool userHasThis;
  final bool needsUpdate;
  final String? copiedFromDeckId;
  final String? ownerDisplayName;
  final double? averageRating;
  final int? ratingCount;

  const RemoteDeckListItem({
    required this.id,
    required this.title,
    required this.description,
    required this.questionCount,
    this.userHasThis = false,
    this.needsUpdate = false,
    this.copiedFromDeckId,
    this.ownerDisplayName,
    this.averageRating,
    this.ratingCount,
  });
}

/// Update preview for a community copy (from GET /api/decks/:id/update-preview).
class UpdatePreview {
  final List<String> changes;

  const UpdatePreview({required this.changes});
}

/// HTTP client for the deck REST API.
class RemoteDeckService {
  RemoteDeckService._();
  static final RemoteDeckService _instance = RemoteDeckService._();
  static RemoteDeckService get instance => _instance;

  String? get _token => ApiAuthService.instance.token;

  Future<Map<String, String>> get _headers async {
    final t = _token;
    if (t == null) return {'Content-Type': 'application/json'};
    return {
      'Content-Type': 'application/json',
      'Authorization': 'Bearer $t',
    };
  }

  void _checkResponse(http.Response res) {
    if (res.statusCode >= 400) {
      throw RemoteDeckException(
        statusCode: res.statusCode,
        body: res.body,
      );
    }
  }

  static String? _stringOrNull(dynamic v) {
    if (v == null) return null;
    final s = v.toString().trim();
    return s.isEmpty ? null : s;
  }

  List<RemoteDeckListItem> _parseDeckList(dynamic body) {
    if (body is List) {
      return body.map((e) => _parseDeckListItem(e as Map<String, dynamic>)).toList();
    }
    if (body is Map<String, dynamic>) {
      final list = body['decks'] as List<dynamic>? ?? [];
      return list.map((e) => _parseDeckListItem(e as Map<String, dynamic>)).toList();
    }
    return [];
  }

  /// GET /api/decks/mine
  Future<List<RemoteDeckListItem>> getMyDecks() async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/mine');
    final res = await http.get(uri, headers: await _headers);
    _checkResponse(res);
    final body = jsonDecode(res.body);
    return _parseDeckList(body);
  }

  /// GET /api/decks/published
  Future<List<RemoteDeckListItem>> getPublishedDecks() async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/published');
    final res = await http.get(uri, headers: await _headers);
    _checkResponse(res);
    final body = jsonDecode(res.body);
    return _parseDeckList(body);
  }

  RemoteDeckListItem _parseDeckListItem(Map<String, dynamic> json) {
    return RemoteDeckListItem(
      id: (json['id']?.toString() ?? '').trim(),
      title: json['title'] as String? ?? '',
      description: json['description'] as String? ?? '',
      questionCount: json['question_count'] as int? ?? 0,
      userHasThis: json['user_has_this'] as bool? ?? false,
      needsUpdate: json['needs_update'] as bool? ?? false,
      copiedFromDeckId: _stringOrNull(json['copied_from_deck_id']),
      ownerDisplayName: json['owner_display_name'] as String?,
      averageRating: (json['average_rating'] as num?)?.toDouble(),
      ratingCount: json['rating_count'] as int?,
    );
  }

  /// GET /api/decks/:id — full deck with questions.
  Future<Deck> getDeck(String deckId) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/$deckId');
    final res = await http.get(uri, headers: await _headers);
    _checkResponse(res);
    final json = jsonDecode(res.body) as Map<String, dynamic>;
    return _jsonToDeck(json);
  }

  /// POST /api/decks — create deck; returns new deck id.
  Future<String> createDeck({
    required String title,
    required String description,
    Map<String, dynamic>? config,
    List<Map<String, dynamic>>? questions,
    String? copiedFromDeckId,
    int? copiedFromVersion,
  }) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks');
    final body = <String, dynamic>{
      'title': title,
      'description': description,
      if (config != null) 'config': config,
      if (questions != null) 'questions': questions,
      if (copiedFromDeckId != null) 'copiedFromDeckId': copiedFromDeckId,
      if (copiedFromVersion != null) 'copiedFromVersion': copiedFromVersion,
    };
    final res = await http.post(
      uri,
      headers: await _headers,
      body: jsonEncode(body),
    );
    _checkResponse(res);
    final data = jsonDecode(res.body) as Map<String, dynamic>;
    return data['id'] as String? ?? '';
  }

  /// PATCH /api/decks/:id
  Future<void> updateDeck(
    String deckId, {
    String? title,
    String? description,
    Map<String, dynamic>? config,
    List<Map<String, dynamic>>? questions,
  }) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/$deckId');
    final body = <String, dynamic>{};
    if (title != null) body['title'] = title;
    if (description != null) body['description'] = description;
    if (config != null) body['config'] = config;
    if (questions != null) body['questions'] = questions;
    final res = await http.patch(
      uri,
      headers: await _headers,
      body: jsonEncode(body),
    );
    _checkResponse(res);
  }

  /// POST /api/decks/:id/publish
  Future<void> setPublished(String deckId, bool published) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/$deckId/publish');
    final res = await http.post(
      uri,
      headers: await _headers,
      body: jsonEncode({'published': published}),
    );
    _checkResponse(res);
  }

  /// POST /api/decks/:id/copy — copy published deck to current user; returns new deck id.
  Future<String> copyDeck(String deckId) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/$deckId/copy');
    final res = await http.post(uri, headers: await _headers);
    _checkResponse(res);
    final data = jsonDecode(res.body) as Map<String, dynamic>;
    return data['id'] as String? ?? '';
  }

  /// GET /api/decks/:id/update-preview
  Future<UpdatePreview> getUpdatePreview(String copyDeckId) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/$copyDeckId/update-preview');
    final res = await http.get(uri, headers: await _headers);
    _checkResponse(res);
    final data = jsonDecode(res.body) as Map<String, dynamic>;
    final changes = (data['changes'] as List<dynamic>?)?.cast<String>() ?? [];
    return UpdatePreview(changes: changes);
  }

  /// POST /api/decks/:id/apply-update
  Future<void> applyUpdate(String copyDeckId) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/$copyDeckId/apply-update');
    final res = await http.post(uri, headers: await _headers);
    _checkResponse(res);
  }

  Future<void> deleteDeck(String deckId) async {
    final uri = Uri.parse('$apiBaseUrl/api/decks/$deckId');
    final res = await http.delete(uri, headers: await _headers);
    _checkResponse(res);
  }

  Deck _jsonToDeck(Map<String, dynamic> json) {
    final configJson = json['config'] as Map<String, dynamic>? ?? {};
    final config = DeckConfig(
      requiredConsecutiveCorrect: configJson['requiredConsecutiveCorrect'] as int? ?? 3,
      defaultAttemptSize: configJson['defaultAttemptSize'] as int? ?? 10,
      priorityIncreaseOnIncorrect: configJson['priorityIncreaseOnIncorrect'] as int? ?? 5,
      priorityDecreaseOnCorrect: configJson['priorityDecreaseOnCorrect'] as int? ?? 2,
      immediateFeedbackEnabled: configJson['immediateFeedbackEnabled'] as bool? ?? true,
      includeKnownInAttempts: configJson['includeKnownInAttempts'] as bool? ?? false,
      shuffleAnswerOrder: configJson['shuffleAnswerOrder'] as bool? ?? true,
      excludeFlaggedQuestions: configJson['excludeFlaggedQuestions'] as bool? ?? false,
      timeLimitSeconds: configJson['timeLimitSeconds'] as int?,
    );

    final questionsJson = json['questions'] as List<dynamic>? ?? [];
    final questions = questionsJson.asMap().entries.map((entry) {
      final i = entry.key;
      final qJson = entry.value as Map<String, dynamic>;
      return _jsonToQuestion(qJson, defaultId: 'q$i');
    }).toList();

    return Deck(
      id: json['id'] as String? ?? '',
      title: json['title'] as String? ?? '',
      description: json['description'] as String? ?? '',
      questions: questions,
      config: config,
      currentAttemptIndex: 0,
      attemptHistory: const [],
      incompleteAttempt: null,
    );
  }

  Question _jsonToQuestion(Map<String, dynamic> q, {String? defaultId}) {
    List<int>? correctIndices;
    if (q['correct_answer_indices'] != null) {
      final arr = q['correct_answer_indices'] as List<dynamic>?;
      correctIndices = arr?.map((e) => e as int).toList();
    }
    if (correctIndices == null && q['correctAnswerIndices'] != null) {
      final arr = q['correctAnswerIndices'] as List<dynamic>?;
      correctIndices = arr?.map((e) => e as int).toList();
    }

    return Question(
      id: q['id'] as String? ?? defaultId ?? '',
      prompt: q['prompt'] as String? ?? '',
      explanation: q['explanation'] as String?,
      answers: (q['answers'] as List<dynamic>?)
              ?.map((e) => e.toString())
              .toList() ??
          [],
      correctAnswerIndices: correctIndices ?? [0],
      consecutiveCorrect: q['consecutiveCorrect'] as int? ?? 0,
      isKnown: q['isKnown'] as bool? ?? false,
      isFlagged: q['isFlagged'] as bool? ?? false,
      priorityPoints: q['priorityPoints'] as int? ?? 0,
      lastAttemptIndex: q['lastAttemptIndex'] as int? ?? -1,
      totalCorrectAttempts: q['totalCorrectAttempts'] as int? ?? 0,
      totalAttempts: q['totalAttempts'] as int? ?? 0,
    );
  }

  static List<Map<String, dynamic>> deckQuestionsToApi(List<Question> questions) {
    return questions.asMap().entries.map((entry) {
      final q = entry.value;
      return {
        'prompt': q.prompt,
        'explanation': q.explanation,
        'answers': q.answers,
        'correct_answer_indices': q.correctAnswerIndices,
      };
    }).toList();
  }

  static Map<String, dynamic> deckConfigToApi(DeckConfig config) {
    return {
      'requiredConsecutiveCorrect': config.requiredConsecutiveCorrect,
      'defaultAttemptSize': config.defaultAttemptSize,
      'priorityIncreaseOnIncorrect': config.priorityIncreaseOnIncorrect,
      'priorityDecreaseOnCorrect': config.priorityDecreaseOnCorrect,
      'immediateFeedbackEnabled': config.immediateFeedbackEnabled,
      'includeKnownInAttempts': config.includeKnownInAttempts,
      'shuffleAnswerOrder': config.shuffleAnswerOrder,
      'excludeFlaggedQuestions': config.excludeFlaggedQuestions,
      'timeLimitSeconds': config.timeLimitSeconds,
    };
  }
}

class RemoteDeckException implements Exception {
  final int statusCode;
  final String body;

  const RemoteDeckException({required this.statusCode, required this.body});

  @override
  String toString() => 'RemoteDeckException($statusCode): $body';
}