/// API 服务 — 封装所有 HTTP 请求

import 'dart:convert';
import 'package:crypto/crypto.dart';
import 'package:dio/dio.dart';
import 'package:shared_preferences/shared_preferences.dart';

class ApiService {
  late final Dio _dio;
  String? _baseUrl;
  String? _token;

  String? get token => _token;
  String? get baseUrl => _baseUrl;

  ApiService() {
    _dio = Dio(BaseOptions(
      connectTimeout: const Duration(seconds: 10),
      receiveTimeout: const Duration(seconds: 30),
      headers: {'Content-Type': 'application/json'},
    ));

    // 签名拦截器：给每个 API 请求加上客户端签名
    _dio.interceptors.add(InterceptorsWrapper(
      onRequest: (options, handler) {
        if (_token != null && !options.path.contains('/auth/verify') &&
            !options.path.contains('/health')) {
          final ts = DateTime.now().millisecondsSinceEpoch ~/ 1000;
          final payload = utf8.encode('${options.method}${options.path}$ts');
          final key = utf8.encode(_token!);
          final sig = Hmac(sha256, key).convert(payload);
          final sigHex = sig.bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
          options.headers['X-Timestamp'] = '$ts';
          options.headers['X-Signature'] = sigHex;
        }
        handler.next(options);
      },
    ));

    _dio.interceptors.add(LogInterceptor(requestBody: false, responseBody: false));
  }

  // ── 连接配置 ──────────────────────────────────────

  bool get isConfigured => _baseUrl != null && _token != null;

  Future<void> loadConfig() async {
    final prefs = await SharedPreferences.getInstance();
    _baseUrl = prefs.getString('server_url');
    _token = prefs.getString('api_token');
    if (_baseUrl != null) {
      _dio.options.baseUrl = _baseUrl!;
    }
  }

  Future<void> saveConfig(String url, String token) async {
    _baseUrl = url.endsWith('/') ? url.substring(0, url.length - 1) : url;
    _token = token;
    _dio.options.baseUrl = _baseUrl!;

    final prefs = await SharedPreferences.getInstance();
    await prefs.setString('server_url', _baseUrl!);
    await prefs.setString('api_token', token);
  }

  Future<bool> verifyToken(String url, String token) async {
    try {
      final testDio = Dio(BaseOptions(
        baseUrl: url.endsWith('/') ? url.substring(0, url.length - 1) : url,
        connectTimeout: const Duration(seconds: 5),
      ));
      final response = await testDio.post('/api/auth/verify', data: {'token': token});
      return response.data['valid'] == true;
    } catch (_) {
      return false;
    }
  }

  Future<void> clearConfig() async {
    _baseUrl = null;
    _token = null;
    final prefs = await SharedPreferences.getInstance();
    await prefs.remove('server_url');
    await prefs.remove('api_token');
  }

  Options get _authOptions => Options(headers: {
        'Authorization': 'Bearer $_token',
      });

  // ── 健康检查 ──────────────────────────────────────

  Future<Map<String, dynamic>> health() async {
    final response = await _dio.get('/api/health');
    return response.data;
  }

  // ── 统计 ──────────────────────────────────────────

  Future<Map<String, dynamic>> stats() async {
    final response = await _dio.get('/api/stats', options: _authOptions);
    return response.data;
  }

  // ── 题目列表 ──────────────────────────────────────

  Future<Map<String, dynamic>> listProblems({
    String? chapter,
    String? knowledgeCode,
    String? questionType,
    String? importType,
    String? annotated,
    int page = 1,
    int pageSize = 20,
  }) async {
    final params = <String, dynamic>{
      'page': page,
      'page_size': pageSize,
    };
    if (chapter != null && chapter.isNotEmpty) params['chapter'] = chapter;
    if (knowledgeCode != null && knowledgeCode.isNotEmpty) params['knowledge_code'] = knowledgeCode;
    if (questionType != null && questionType.isNotEmpty) params['question_type'] = questionType;
    if (importType != null && importType.isNotEmpty) params['import_type'] = importType;
    if (annotated != null && annotated.isNotEmpty) params['annotated'] = annotated;

    final response = await _dio.get('/api/problems', queryParameters: params, options: _authOptions);
    return response.data;
  }

  // WebDAV
  Future<Map<String, dynamic>> getWebDAVConfig() async {
    final response = await _dio.get('/api/admin/backup-config', options: _authOptions);
    return response.data;
  }

  Future<void> setWebDAVConfig(String url, String username, String password) async {
    await _dio.put('/api/admin/backup-config',
        data: {'url': url, 'username': username, 'password': password},
        options: _authOptions);
  }

  Future<void> triggerFullBackup() async {
    await _dio.post('/api/admin/full-backup', options: _authOptions);
  }

  // ── 题目详情 ──────────────────────────────────────

  Future<Map<String, dynamic>> problemDetail(String id) async {
    final response = await _dio.get('/api/problems/$id', options: _authOptions);
    return response.data;
  }

  // ── 题目渲染 ──────────────────────────────────────

  Future<Map<String, dynamic>> renderProblem(String id, {bool includeAnswer = true}) async {
    final response = await _dio.get(
      '/api/problems/$id/render',
      queryParameters: {'include_answer': includeAnswer},
      options: _authOptions,
    );
    return response.data;
  }

  // ── 搜索 ──────────────────────────────────────────

  Future<Map<String, dynamic>> search(String query, {int page = 1, int pageSize = 20}) async {
    final response = await _dio.get(
      '/api/search',
      queryParameters: {'q': query, 'page': page, 'page_size': pageSize},
      options: _authOptions,
    );
    return response.data;
  }

  // ── 元数据更新 ────────────────────────────────────

  Future<void> updateMetadata(String id, Map<String, dynamic> fields) async {
    await _dio.put('/api/problems/$id/metadata', data: fields, options: _authOptions);
  }

  Future<void> updateKnowledge(String id, List<String> codes) async {
    await _dio.put('/api/problems/$id/knowledge', data: {'knowledge_codes': codes}, options: _authOptions);
  }

  // ── 连续标注导航 ──────────────────────────────────

  Future<Map<String, dynamic>> nextUnannotated({String? currentId, String direction = 'next'}) async {
    final params = <String, dynamic>{'direction': direction};
    if (currentId != null) params['current_id'] = currentId;
    final response = await _dio.get('/api/problems/next-unannotated', queryParameters: params, options: _authOptions);
    return response.data;
  }

  // ── 导入 ──────────────────────────────────────────

  Future<Map<String, dynamic>> importDocx(String filePath, String importType) async {
    final formData = FormData.fromMap({
      'file': await MultipartFile.fromFile(filePath, filename: filePath.split('/').last),
      'import_type': importType,
    });
    final response = await _dio.post('/api/import', data: formData, options: _authOptions);
    return response.data;
  }

  Future<Map<String, dynamic>> importStatus(String taskId) async {
    final response = await _dio.get('/api/import/$taskId/status', options: _authOptions);
    return response.data;
  }

  // ── 导出 ──────────────────────────────────────────

  Future<Map<String, dynamic>> exportChapter(String? chapter, String? importType, String title) async {
    final response = await _dio.post('/api/export/chapter',
        data: {'chapter': chapter, 'import_type': importType, 'title': title},
        options: _authOptions);
    return response.data;
  }

  Future<Map<String, dynamic>> exportCart(int cartId, String title) async {
    final response = await _dio.post('/api/export/cart/$cartId',
        data: {'title': title}, options: _authOptions);
    return response.data;
  }

  String get downloadUrl => '$_baseUrl/api/exports/';

  Future<String> downloadExport(String filename, String savePath) async {
    await _dio.download('/api/exports/$filename', savePath, options: _authOptions);
    return savePath;
  }

  // ── 知识点 ────────────────────────────────────────

  Future<Map<String, dynamic>> knowledgeTree() async {
    final response = await _dio.get('/api/knowledge/tree', options: _authOptions);
    return response.data;
  }

  Future<Map<String, dynamic>> searchKnowledge(String query) async {
    final response = await _dio.get('/api/knowledge/search', queryParameters: {'q': query}, options: _authOptions);
    return response.data;
  }

  // ── 试题篮 ────────────────────────────────────────

  Future<Map<String, dynamic>> listCarts() async {
    final response = await _dio.get('/api/carts', options: _authOptions);
    return response.data;
  }

  Future<Map<String, dynamic>> createCart(String name) async {
    final response = await _dio.post('/api/carts', data: {'name': name}, options: _authOptions);
    return response.data;
  }

  Future<void> deleteCart(int id) async {
    await _dio.delete('/api/carts/$id', options: _authOptions);
  }

  Future<Map<String, dynamic>> cartDetail(int id) async {
    final response = await _dio.get('/api/carts/$id', options: _authOptions);
    return response.data;
  }

  Future<void> addToCart(int cartId, String problemId) async {
    await _dio.post('/api/carts/$cartId/items', data: {'problem_id': problemId}, options: _authOptions);
  }

  Future<void> removeFromCart(int cartId, String problemId) async {
    await _dio.delete('/api/carts/$cartId/items/$problemId', options: _authOptions);
  }

  Future<void> clearCart(int cartId) async {
    await _dio.post('/api/carts/$cartId/clear', options: _authOptions);
  }
}