/// 上传传输抽象与双实现（P3 计划 Task 7；Task 8 扩展 iOS 选择分支）。
///
/// 引擎的传输步骤（presign PUT）经 [Transport] 接口委托：
/// - **[DartHttpTransport]**（Task 6 逻辑原样抽出）：裸 dio 流式 PUT +
///   进度计数流 + 取消令牌——桌面 / 调试路径（dart-define
///   `FORCE_DART_TRANSPORT=true` 强制启用）；
/// - **[NativeTransport]**（Task 7 新增，Android；Task 8 起含 iOS）：
///   MethodChannel `photolive/uploads` 注册原生后台上传——Android =
///   WorkManager 后台工作（expedited + dataSync 前台服务）；iOS =
///   URLSession background（identifier com.photolive.photo_live.uploads，
///   编译留 G3）。两平台协议逐字一致（Kotlin `UploadProtocol.kt` /
///   Swift `UploadBridge.swift`），EventChannel `photolive/uploads/events`
///   回流 progress/completed/failed/needsRenew 事件——App 切后台/锁屏后
///   续传由系统调度承担。
///
/// 失败语义（两实现归一为 [TransportException] 族，引擎分类见
/// upload_engine.dart `_classifyFailure`）：
/// | 情形 | 异常 |
/// |---|---|
/// | 网络不可达/超时/取消令牌触发前的连接层失败 | `TransportException(network)` |
/// | HTTP 403（presign 凭证过期） | [TransportRenewRequiredException]（引擎 renew 后重发） |
/// | 其余 HTTP 非 2xx | `TransportException(http, statusCode)` |
/// | 源文件缺失（原生 worker 发现） | `TransportException(sourceMissing)` |
/// | 平台通道调用失败 | `TransportException(channel)` |
/// | 取消令牌触发 | `TransportException(cancelled)`（引擎静默收敛） |
library;

import 'dart:async';
import 'dart:io';

import 'package:dio/dio.dart';
import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter/services.dart';

/// presign PUT 传输接口（引擎只委托文件 PUT；init/complete/renew 仍在
/// Dart 引擎内，保持服务端交互语义单源）。
abstract interface class Transport {
  /// 单次文件 PUT。
  ///
  /// - 成功返回 [TransportResult]（ETag 供诊断；完成核验以服务端为准）；
  /// - 失败抛 [TransportException] 族（见库级注释分类表）；
  /// - [cancelToken] 取消时抛 `TransportException(cancelled)`。
  Future<TransportResult> send({
    required String taskId,
    required String url,
    required String method,
    required Map<String, String> headers,
    required String filePath,
    Map<String, Object?>? metadata,
    void Function(int sent, int total)? onProgress,
    CancelToken? cancelToken,
  });

  /// 释放底层资源（引擎 dispose 调用；注入方自持传输时自行管理）。
  void dispose();
}

/// PUT 成功结果。
class TransportResult {
  const TransportResult({this.etag});

  /// 服务端返回的 ETag 响应头（可空；仅诊断用途）。
  final String? etag;
}

/// 传输失败码（原生侧事件码与本侧异常码的归一层）。
abstract final class TransportErrorCodes {
  /// 网络不可达/超时/连接层失败。
  static const String network = 'NETWORK';

  /// HTTP 层失败（statusCode 保留在异常上）。
  static const String http = 'HTTP';

  /// 取消令牌触发（非失败分类；引擎静默收敛）。
  static const String cancelled = 'CANCELLED';

  /// 源文件缺失（受管副本被清理，不可恢复）。
  static const String sourceMissing = 'SOURCE_MISSING';

  /// 平台通道调用失败（桥接层异常）。
  static const String channel = 'CHANNEL';
}

/// 传输失败（两实现统一的异常类型）。
class TransportException implements Exception {
  const TransportException(this.code, {this.statusCode, this.cause});

  /// 失败分类（[TransportErrorCodes]）。
  final String code;

  /// HTTP 状态码（http 类失败携带）。
  final int? statusCode;

  /// 底层异常（诊断）。
  final Object? cause;

  @override
  String toString() =>
      'TransportException($code${statusCode != null ? ', status=$statusCode' : ''}'
      '${cause != null ? ', cause=$cause' : ''})';
}

/// HTTP 403（presign 凭证过期）：引擎 renewUpload 换新凭证后重发。
class TransportRenewRequiredException extends TransportException {
  const TransportRenewRequiredException({super.cause})
      : super(TransportErrorCodes.http, statusCode: 403);
}

// ── Dart（dio）实现 ──────────────────────────────────────────────────────

/// Task 6 的裸 dio 直传实现（iOS / 桌面 / FORCE_DART_TRANSPORT 调试）。
///
/// 严格携带 credential.headers（+ Content-Length——流式发送 dio 无法自动
/// 推断，显式声明）；进度经计数流上报（不依赖适配器对 onSendProgress 的
/// 实现）。
class DartHttpTransport implements Transport {
  DartHttpTransport({Dio? dio})
      : _dio = dio,
        _ownedDio = dio == null;

  final Dio? _dio;
  final bool _ownedDio;

  /// 自建实例惰性创建（注入 dio 时不建）。
  Dio? _created;
  Dio get _client => _dio ?? (_created ??= Dio());

  @override
  Future<TransportResult> send({
    required String taskId,
    required String url,
    required String method,
    required Map<String, String> headers,
    required String filePath,
    Map<String, Object?>? metadata,
    void Function(int sent, int total)? onProgress,
    CancelToken? cancelToken,
  }) async {
    final file = File(filePath);
    final length = await file.length();
    var sent = 0;
    final progressStream = file.openRead().map((List<int> chunk) {
      sent += chunk.length;
      onProgress?.call(sent, length);
      return chunk;
    });
    try {
      final resp = await _client.put<void>(
        url,
        data: progressStream,
        cancelToken: cancelToken,
        options: Options(
          method: method,
          headers: {
            ...headers,
            Headers.contentLengthHeader: length,
          },
          // 响应体非 JSON（MinIO XML/空），防 transformer 解析报错。
          responseType: ResponseType.plain,
          receiveDataWhenStatusError: true,
        ),
      );
      final etag = resp.headers.value(HttpHeaders.etagHeader);
      return TransportResult(etag: etag);
    } on DioException catch (e) {
      throw _mapDioException(e);
    }
  }

  /// dio 异常 → 传输异常归一（403 → renew；连接层 → network；取消 →
  /// cancelled；其余 badResponse → http）。
  static TransportException _mapDioException(DioException e) {
    if (e.type == DioExceptionType.cancel) {
      return const TransportException(TransportErrorCodes.cancelled);
    }
    final status = e.response?.statusCode;
    if (status != null) {
      if (status == 403) return const TransportRenewRequiredException();
      return TransportException(TransportErrorCodes.http,
          statusCode: status, cause: e);
    }
    if (e.type == DioExceptionType.connectionTimeout ||
        e.type == DioExceptionType.sendTimeout ||
        e.type == DioExceptionType.receiveTimeout ||
        e.type == DioExceptionType.transformTimeout ||
        e.type == DioExceptionType.connectionError ||
        e.type == DioExceptionType.badCertificate ||
        e.type == DioExceptionType.unknown) {
      return TransportException(TransportErrorCodes.network, cause: e);
    }
    // badResponse 无响应必经上方分支，防御性兜底为网络类。
    return TransportException(TransportErrorCodes.network, cause: e);
  }

  @override
  void dispose() {
    if (_ownedDio) {
      _client.close();
    }
  }
}

// ── 原生（Android WorkManager / iOS URLSession background）实现 ─────────

/// 平台通道名（与 Android `UploadPlugin.kt` / iOS `UploadPlugin.swift`
/// 一致；原生常量见 UploadProtocol.kt 与 UploadBridge.swift——Task 8 起
/// iOS 为同一协议的 Swift 镜像，无协议分歧）。
abstract final class UploadBridgeChannels {
  /// 命令通道：registerTask / cancelTask / queryTask / ackEvents。
  static const String methods = 'photolive/uploads';

  /// 事件流：progress / completed / failed / needsRenew（带 seq，
  /// 终态事件未 ack 前原生侧缓存重放——生命周期安全）。
  static const String events = 'photolive/uploads/events';
}

/// 平台通道绑定薄层（默认真实通道；测试注入替身）。
class NativeUploadChannel {
  const NativeUploadChannel();

  static const MethodChannel _methods = MethodChannel(
    UploadBridgeChannels.methods,
  );
  static const EventChannel _events = EventChannel(
    UploadBridgeChannels.events,
  );

  Future<Object?> invoke(String method, Map<String, Object?> args) =>
      _methods.invokeMethod<Object?>(method, args);

  Stream<dynamic> get events => _events.receiveBroadcastStream();
}

/// 原生事件等待句柄。
class _NativeWaiter {
  _NativeWaiter(this.onProgress);

  final void Function(int sent, int total)? onProgress;
  final Completer<TransportResult> completer = Completer<TransportResult>();

  void complete(TransportResult result) {
    if (!completer.isCompleted) completer.complete(result);
  }

  void completeError(Object error) {
    if (!completer.isCompleted) completer.completeError(error);
  }
}

/// Android/iOS 原生传输：registerTask 入队原生后台上传（Android =
/// WorkManager；iOS = URLSession background），事件流回流终态/进度。
///
/// 生命周期安全：事件带单调 seq；终态事件在 Dart ack 前由原生侧缓存，
/// 重新 listen 时重放——进程重启/切后台恢复后不丢完成信号（iOS 侧缓存
/// 另落盘，系统后台拉起投递的终态在进程重启后同样重放）。进度事件不
/// 重放（瞬态）。
class NativeTransport implements Transport {
  NativeTransport({NativeUploadChannel? channel})
      : _channel = channel ?? const NativeUploadChannel();

  final NativeUploadChannel _channel;

  StreamSubscription<dynamic>? _eventsSub;
  final Map<String, _NativeWaiter> _waiters = <String, _NativeWaiter>{};

  void _ensureSubscribed() {
    if (_eventsSub != null) return;
    _eventsSub = _channel.events.listen(
      _onEvent,
      onError: (Object _) {
        // 事件流出错：丢弃订阅，下次 send 重建（注册重试语义兜底）。
        _eventsSub?.cancel();
        _eventsSub = null;
      },
      onDone: () => _eventsSub = null,
    );
  }

  void _onEvent(dynamic raw) {
    if (raw is! Map) return;
    final event = Map<String, Object?>.from(raw);
    final taskId = event['taskId'] as String?;
    final waiter = taskId == null ? null : _waiters[taskId];
    switch (event['event']) {
      case 'progress':
        final sent = (event['sent'] as num?)?.toInt();
        final total = (event['total'] as num?)?.toInt();
        if (waiter != null && sent != null && total != null) {
          waiter.onProgress?.call(sent, total);
        }
      case 'completed':
        waiter?.complete(
          TransportResult(etag: event['etag'] as String?),
        );
        _ackTerminal(event);
      case 'needsRenew':
        waiter?.completeError(const TransportRenewRequiredException());
        _ackTerminal(event);
      case 'failed':
        waiter?.completeError(_mapFailedEvent(event));
        _ackTerminal(event);
      default:
        break; // 未知事件：前向兼容忽略。
    }
  }

  /// 原生失败码 → 传输异常。
  static TransportException _mapFailedEvent(Map<String, Object?> event) {
    final status = (event['status'] as num?)?.toInt();
    switch (event['code']) {
      case 'NETWORK':
        return const TransportException(TransportErrorCodes.network);
      case 'SOURCE_MISSING':
        return const TransportException(TransportErrorCodes.sourceMissing);
      case 'HTTP_4XX':
      case 'SERVER_ERROR':
        return TransportException(
          TransportErrorCodes.http,
          statusCode: status,
        );
      default:
        return TransportException(
          event['code'] as String? ?? TransportErrorCodes.channel,
          statusCode: status,
        );
    }
  }

  void _ackTerminal(Map<String, Object?> event) {
    final seq = (event['seq'] as num?)?.toInt();
    if (seq == null) return;
    unawaited(
      _channel
          .invoke('ackEvents', <String, Object?>{'seq': seq})
          .catchError((Object _) => null),
    );
  }

  @override
  Future<TransportResult> send({
    required String taskId,
    required String url,
    required String method,
    required Map<String, String> headers,
    required String filePath,
    Map<String, Object?>? metadata,
    void Function(int sent, int total)? onProgress,
    CancelToken? cancelToken,
  }) async {
    _ensureSubscribed();
    final waiter = _NativeWaiter(onProgress);
    _waiters[taskId] = waiter;
    // 取消令牌联动：cancelTask（原生尽力停止 worker）+ 等待句柄立即失败。
    cancelToken?.whenCancel.then((_) {
      // 已终结则 no-op（isCompleted 守护）。
      waiter.completeError(
        const TransportException(TransportErrorCodes.cancelled),
      );
      unawaited(
        _channel
            .invoke('cancelTask', <String, Object?>{'taskId': taskId})
            .catchError((Object _) => null),
      );
    });
    try {
      await _channel.invoke('registerTask', <String, Object?>{
        'taskId': taskId,
        'url': url,
        'method': method,
        'headers': headers,
        'filePath': filePath,
        'metadata': metadata ?? const <String, Object?>{},
      });
    } on PlatformException catch (e) {
      // 注册失败：摘除等待句柄后归一为通道异常。
      if (_waiters[taskId] == waiter) _waiters.remove(taskId);
      throw TransportException(TransportErrorCodes.channel, cause: e);
    }
    try {
      return await waiter.completer.future;
    } finally {
      if (_waiters[taskId] == waiter) _waiters.remove(taskId);
    }
  }

  /// 查询原生侧工作状态（WorkInfo 概览；Task 9/11 校准用）。
  Future<Map<String, Object?>?> queryTask(String taskId) async {
    try {
      final result = await _channel
          .invoke('queryTask', <String, Object?>{'taskId': taskId});
      return result == null
          ? null
          : Map<String, Object?>.from(result as Map<dynamic, dynamic>);
    } on PlatformException {
      return null;
    }
  }

  @override
  void dispose() {
    _eventsSub?.cancel();
    _eventsSub = null;
  }
}

// ── 传输选择 ─────────────────────────────────────────────────────────────

/// dart-define FORCE_DART_TRANSPORT=true：Android/iOS 也强制 Dart dio
/// 路径（桥接层问题排查用）。
const bool kForceDartTransport = bool.fromEnvironment('FORCE_DART_TRANSPORT');

/// 传输选择纯函数（可测）：Android 或 iOS 且未强制 Dart → 原生。
///
/// Task 8 起含 iOS：协议与 Android 逐字一致（同一 [NativeTransport]
/// 经同一通道名驱动 Swift 侧 UploadPlugin——iOS 编译/真机验证留 G3，
/// 代码路径在此之前即纳入原生选择）。
bool preferNativeTransport({
  required bool isAndroid,
  required bool isIOS,
  bool forceDartTransport = kForceDartTransport,
}) =>
    (isAndroid || isIOS) && !forceDartTransport;

/// 默认传输解析：Android/iOS → [NativeTransport]（WorkManager /
/// URLSession background 后台续传）；其余平台 / 强制覆盖 →
/// [DartHttpTransport]。
Transport defaultUploadTransport() {
  if (preferNativeTransport(
    isAndroid: !kIsWeb && Platform.isAndroid,
    isIOS: !kIsWeb && Platform.isIOS,
  )) {
    return NativeTransport();
  }
  return DartHttpTransport();
}