import 'dart:io';
import 'dart:math';
import 'package:dio/dio.dart';
import 'package:mime/mime.dart';
import 'package:path/path.dart' as path;
import 'package:path_provider/path_provider.dart';
import 'package:permission_handler/permission_handler.dart';


const _show_debug_info = true;



/// 下载状态枚举
enum DownloadStatus {
  downloading,
  completed,
  failed,
}

/// 下载结果
class DownloadResult {
  final DownloadStatus status;
  final String? filePath;
  final double? progress;
  final int? errorCode;
  final String? errorReason;

  bool get isCompleted => status == DownloadStatus.completed;
  bool get isDownloading => status == DownloadStatus.downloading;
  bool get isFailed => status == DownloadStatus.failed;


  /// ----- error code -----
  static const int errorCodeError = -1;
  static const int errorCodePermissionDenied = -2;


  /// ----- constructor -----
  DownloadResult({
    required this.status,
    this.filePath,
    this.progress,
    this.errorCode,
    this.errorReason,
  });

  factory DownloadResult.downloading(double progress) {
    if (progress < 0) { progress = 0; }
    else if (progress > 1) { progress = 1; }
    return DownloadResult(
      status: DownloadStatus.downloading,
      progress: progress,
    );
  }

  factory DownloadResult.failed({
    int errorCode = errorCodeError,
    String? errorReason,
  }) {
    return DownloadResult(
      status: DownloadStatus.failed,
      errorCode: errorCode,
      errorReason: errorReason,
    );
  }

  factory DownloadResult.completed({
    required String filePath,
  }) {
    return DownloadResult(
      status: DownloadStatus.completed,
      filePath: filePath,
      progress: 1.0,
    );
  }
}


class HttpDownloader {

  //下载
  static Future<DownloadResult> download({
    required String fileUrl,
    String? fileName,
    void Function(DownloadResult)? onProgress,
  }) async {

    // 请求存储权限
    PermissionStatus status = await Permission.storage.request();
    if (!status.isGranted) {
      final result = DownloadResult.failed(
        errorCode: DownloadResult.errorCodePermissionDenied,
        errorReason: 'no storage permission',
      );
      if (onProgress != null) {
        onProgress(result);
      }
      return result;
    }


    // 获取下载目录
    final saveDir = await getDownloadDirectory();
    // 处理保存文件名
    fileName ??= await processFileName(fileUrl, fileName);
    final savePath = '$saveDir/$fileName';

    try {
      final dio = Dio();

      // 发送开始下载状态
      if (_show_debug_info) {
        print('┌────────────────────────────────────────────────────────────────────────────────────────');
        print('│ ⬇️ start download: $fileUrl');
        print('│    save path: $fileName');
        print('└────────────────────────────────────────────────────────────────────────────────────────');
      }
      if (onProgress != null) {
        onProgress(DownloadResult.downloading(0.0));
      }

      await dio.download(
        fileUrl,
        savePath,
        onReceiveProgress: (received, total) {
          if (_show_debug_info) {
            print('$fileName receive: $received/$total');
          }
          if (total != -1) {
            if (onProgress != null) {
              onProgress(DownloadResult.downloading(received / total));
            }
          }
        },
      );

      // 发送完成状态
      if (_show_debug_info) {
        print('文件下载完成: $savePath');
      }
      final result = DownloadResult.completed(filePath: savePath);
      if (onProgress != null) {
        onProgress(result);
      }
      return result;

    } catch (e) {
      print('下载失败: $e');
      // 发送失败状态
      final result = DownloadResult.failed(
        errorReason: e.toString(),
      );
      if (onProgress != null) {
        onProgress(result);
      }
      return result;
    }
  }

  //  文件存储路径
  static Future<String> getDownloadDirectory() async {

    Directory directory;
    if (Platform.isAndroid) {
      // Android: 外部存储目录（对应 RNFS.ExternalDirectoryPath）
      directory = await getExternalStorageDirectory() ??
          await getApplicationDocumentsDirectory();
    } else if (Platform.isIOS) {
      // iOS: Library 目录
      directory = await getLibraryDirectory();
    } else {
      // 其他平台使用文档目录
      directory = await getApplicationDocumentsDirectory();
    }

    // 创建 dl_cache 子目录
    final cacheDir = Directory(path.join(directory.path, 'cache'));
    if (!await cacheDir.exists()) {
      await cacheDir.create(recursive: true);
    }
    return cacheDir.path;
  }


  //验证文件名
  static String getValidFileName(String name) {
    // 替换无效字符
    return name.replaceAll(RegExp(r'[\\/:*?"<>|]'), '_');
  }

  // 获取文件名
  static Future<String> processFileName(String url, String? customName) async {
    String fileName;

    if (customName != null) {
      fileName = getValidFileName(customName);
    } else {
      // 尝试从URL获取
      final uri = Uri.parse(url);
      fileName = uri.pathSegments.lastOrNull ?? _randomFileName();

      // 如果没有扩展名，尝试添加
      if (!fileName.contains('.')) {
        final mimeType = await getMimeTypeAccurate(url); // 需要网络请求获取Content-Type
        if (mimeType != null) {
          final ext = mimeType.split('/').last;
          fileName = '$fileName.$ext';
        }
      }
    }
    return fileName;
  }

  static String _randomFileName() {
    const charset = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
    final random = Random.secure();
    final result = StringBuffer();

    for (int i = 0; i < 16; i++) {
      final index = random.nextInt(charset.length);
      result.write(charset[index]);
    }

    return '${result.toString()}${DateTime.now().millisecondsSinceEpoch}';
  }

  // 或者结合网络请求获取更准确的结果
  static Future<String?> getMimeTypeAccurate(String url) async {
    // 先尝试从扩展名获取
    final fromExtension = lookupMimeType(url);

    // 如果无法确定或想验证，可以发送HEAD请求
    try {
      final response = await Dio().head(url);
      final fromHeader = response.headers
          .value('content-type')
          ?.split(';')
          .first;
      return fromHeader ?? fromExtension;
    } catch (e) {
      return fromExtension; // 回退到扩展名推断
    }
  }

}