import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../models/saf_permission_state.dart';

class SafStorageService {
  static final SafStorageService _instance = SafStorageService._internal();
  factory SafStorageService() => _instance;
  SafStorageService._internal();

  static const MethodChannel _channel = MethodChannel(
    'com.lxh.battery_health/saf',
  );
  static const String _prefKeySafUri = 'saf_storage_uri';
  String? _cachedUri;

  // 🟢 初始化时从 SharedPreferences 恢复 URI
  Future<void> init() async {
    try {
      final prefs = await SharedPreferences.getInstance();
      _cachedUri = prefs.getString(_prefKeySafUri);
      if (kDebugMode) {
        print('[SAF] 初始化，缓存 URI: $_cachedUri');
      }
    } catch (e) {
      if (kDebugMode) {
        print('[SAF] 初始化失败: $e');
      }
      _cachedUri = null;
    }
  }

  Future<SafPermissionState> getPermissionState() async {
    if (_cachedUri == null || _cachedUri!.isEmpty) {
      return SafPermissionState.unauthorized;
    }
    // 🟢 直接返回 authorized，相信缓存
    return SafPermissionState.authorized;
  }

  Future<SafAuthorizationResult> requestPermission() async {
    try {
      final String? uriString = await _channel.invokeMethod('selectFolder');

      if (uriString == null || uriString.isEmpty) {
        return SafAuthorizationResult.denied();
      }

      _cachedUri = uriString;
      await _saveUri(uriString);

      if (kDebugMode) {
        print('[SAF] 授权成功，URI: $uriString');
      }

      return SafAuthorizationResult.success(uriString);
    } catch (e) {
      if (kDebugMode) {
        print('[SAF] 授权失败: $e');
      }
      return SafAuthorizationResult.error('授权失败: $e');
    }
  }

  Future<bool> logFileExists(String fileName) async {
    final state = await getPermissionState();
    if (state != SafPermissionState.authorized) return false;
    try {
      final files = await _channel.invokeMethod('listFiles');
      if (files is List) {
        return files.contains(fileName);
      }
      return false;
    } catch (e) {
      return false;
    }
  }

  Future<List<String>> readLogFile(String fileName) async {
    final state = await getPermissionState();
    if (state != SafPermissionState.authorized) return [];
    try {
      final String? content = await _channel.invokeMethod('readLogFile', {
        'fileName': fileName,
      });
      if (content == null || content.isEmpty) return [];
      return content.split('\n');
    } catch (e) {
      if (kDebugMode) {
        print('[SAF] 读取文件失败: $e');
      }
      return [];
    }
  }

  Future<List<String>> listFiles() async {
    final state = await getPermissionState();
    if (state != SafPermissionState.authorized) return [];
    try {
      final result = await _channel.invokeMethod('listFiles');
      if (result is List) {
        return result.cast<String>();
      }
      return [];
    } catch (e) {
      if (kDebugMode) {
        print('[SAF] 列出文件失败: $e');
      }
      return [];
    }
  }

  Future<bool> validatePermission() async {
    final state = await getPermissionState();
    return state == SafPermissionState.authorized;
  }

  void _clearCache() {
    _cachedUri = null;
    _saveUri(null);
  }

  Future<void> _saveUri(String? uri) async {
    try {
      final prefs = await SharedPreferences.getInstance();
      if (uri != null && uri.isNotEmpty) {
        await prefs.setString(_prefKeySafUri, uri);
        if (kDebugMode) {
          print('[SAF] 保存 URI 成功: $uri');
        }
      } else {
        await prefs.remove(_prefKeySafUri);
        if (kDebugMode) {
          print('[SAF] 清除 URI');
        }
      }
    } catch (e) {
      if (kDebugMode) {
        print('[SAF] 保存 URI 失败: $e');
      }
    }
  }

  String? get cachedUri => _cachedUri;
}