307 lines
11 KiB
Dart
307 lines
11 KiB
Dart
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/// 上传准备阶段（P3 计划 Task 6）。
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///
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/// 选图（image_picker）或连拍（camera）得到的源文件 → 复制到受管目录
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/// （app 支持目录/uploads/{accountId}/{albumId}/{taskId}{ext}）→ stat 字节
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/// → MIME 嗅探（扩展名映射 + jpg/png 魔数校验）→ 尺寸上限本地预检 →
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/// 入队 queued。任一步失败 → 独立状态 preparationFailed（可重试，见
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/// [UploadPreparer.retry]），lastError 携带客户端伪码（[PrepErrorCodes]）。
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///
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/// 设计取舍（对齐计划 Task 6 评审口径）：
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/// - **串行执行**：文件复制是最容易造成 IO 风暴的环节（连拍场景一次
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/// 落盘多张），队列化逐张处理；传输并发由 UploadEngine 另行控制；
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/// - **磁盘空间不显式预检**：引入 disk_space 插件成本（新依赖 + 平台
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/// 误差）高于收益——复制失败本身即失败信号（ENOSPC 走 copy 失败分支
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/// → preparationFailed，用户可见可重试）。此为有意裁剪，登记为计划
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/// 偏差；
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/// - **本地尺寸上限**：客户端无法得知服务端 UPLOAD_MAX 环境变量，取
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/// 保守常量 50MB 预检（超限直接 preparationFailed，不浪费复制与传输）；
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/// 界于本地上限与服务端真实上限之间的文件由服务端 400 兜底。
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library;
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import 'dart:async';
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import 'dart:io';
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import 'dart:math';
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import 'package:path/path.dart' as p;
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import 'package:path_provider/path_provider.dart';
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import '../../core/device_id.dart';
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import 'task_state.dart';
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import 'task_store.dart';
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/// 准备阶段失败伪码（客户端本地，契约外；lastError 展示用，
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/// UI 层映射本地化文案）。
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abstract final class PrepErrorCodes {
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/// 源文件不可读（已被清理/权限/不存在）。
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static const String sourceUnreadable = 'PREP_SOURCE_UNREADABLE';
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/// MIME 不在白名单（jpg/png/heic 之外）。
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static const String unsupportedType = 'PREP_UNSUPPORTED_TYPE';
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/// 超过本地尺寸上限（50MB 预检）。
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static const String tooLarge = 'PREP_TOO_LARGE';
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/// 复制到受管目录失败（含磁盘满/复制期间源被改动）。
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static const String copyFailed = 'PREP_COPY_FAILED';
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}
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/// 上传准备器：入队唯一入口（队列 UI/连拍页调用；引擎消费产出）。
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///
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/// 所有操作串行（连拍入队逐张复制，避免 IO 风暴，见库级注释）。
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class UploadPreparer {
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UploadPreparer(
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this._store, {
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Future<Directory> Function()? baseDirProvider,
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Random? random,
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this.maxBytes = kMaxUploadBytes,
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this.onEnqueued,
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}) : _baseDirProvider = baseDirProvider ?? getApplicationSupportDirectory,
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_random = random ?? Random.secure();
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final TaskStore _store;
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final Future<Directory> Function() _baseDirProvider;
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final Random _random;
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/// 本地尺寸预检上限（默认 [kMaxUploadBytes]；测试可注入小值）。
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final int maxBytes;
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/// 本地尺寸预检上限（50MB；服务端 UPLOAD_MAX 由 400 兜底，见库级注释）。
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static const int kMaxUploadBytes = 50 * 1024 * 1024;
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/// 入队成功回调（唤醒传输引擎立即出队）。
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final void Function()? onEnqueued;
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/// 串行队列尾部。
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Future<void> _tail = Future<void>.value();
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/// 准备一张图片并入队。
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///
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/// [sourcePath] 为 image_picker/camera 返回的源文件路径（App 沙箱内
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/// 可直接 File 读取）；[filename] 缺省取源文件 basename。
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///
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/// 返回入队后的任务（state=queued）；失败返回 state=preparationFailed
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/// 的任务（不抛异常——准备失败是业务状态而非调用错误）。
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Future<UploadTask> prepare({
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required String accountId,
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required String albumId,
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String? categoryId,
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required String sourcePath,
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String? filename,
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}) {
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return _serialize(() => _prepare(
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accountId: accountId,
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albumId: albumId,
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categoryId: categoryId,
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sourcePath: sourcePath,
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filename: filename,
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));
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}
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/// 重试准备失败的任务（preparationFailed → preparing → 复制 → queued）。
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///
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/// 源文件原始路径不落库（任务表仅存受管副本路径），调用方（队列 UI）
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/// 需重新提供 [sourcePath]（重新选图，或相机缓存仍存时直传）。
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Future<UploadTask> retry({
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required String accountId,
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required String taskId,
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required String sourcePath,
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}) {
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return _serialize(() => _retry(
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accountId: accountId,
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taskId: taskId,
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sourcePath: sourcePath,
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));
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}
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/// 串行化：所有准备操作首尾相接（错误吞掉以不断链，错误经返回值上抛）。
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Future<T> _serialize<T>(Future<T> Function() op) {
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final result = _tail.then((_) => op());
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_tail = result.then<void>((_) {}, onError: (Object _) {});
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return result;
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}
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Future<UploadTask> _prepare({
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required String accountId,
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required String albumId,
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required String? categoryId,
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required String sourcePath,
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required String? filename,
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}) async {
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final id = _newId();
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final clientTaskId = _newId();
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final ext = _normalizeExt(sourcePath);
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final contentType = await _sniffContentType(sourcePath, ext);
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final bytes = await _statBytes(sourcePath);
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// 快速失败预检：类型不在白名单 / 源不可读（bytes=0）/ 超本地上限。
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final failCode = _preCheck(contentType: contentType, bytes: bytes);
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final dir = await _managedDir(accountId, albumId);
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final targetPath = p.join(dir.path, '$id$ext');
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final task = await _store.create(
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UploadTaskDraft(
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id: id,
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accountId: accountId,
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albumId: albumId,
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categoryId: categoryId,
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clientTaskId: clientTaskId,
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sourceFilePath: targetPath,
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filename: filename ?? p.basename(sourcePath),
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// 预检失败时占位（该行永不进入传输；成功路径 bytes 来自源 stat）。
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bytes: bytes > 0 ? bytes : 1,
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contentType: contentType ?? 'application/octet-stream',
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),
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);
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if (failCode != null) {
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return _store.updateState(
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id,
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UploadTaskState.preparationFailed,
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patch: UploadTaskPatch(lastError: failCode),
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);
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}
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return _copyAndQueue(task, sourcePath: sourcePath);
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}
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Future<UploadTask> _retry({
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required String accountId,
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required String taskId,
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required String sourcePath,
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}) async {
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final task = await _store.get(accountId, taskId);
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if (task == null) {
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throw StateError('上传任务不存在：$taskId');
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}
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if (task.state != UploadTaskState.preparationFailed) {
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throw StateError('仅 preparationFailed 可重试准备（当前：${task.state}）');
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}
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final preparing = await _store.updateState(
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taskId,
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UploadTaskState.preparing,
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patch: const UploadTaskPatch(clearLastError: true),
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);
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return _copyAndQueue(preparing, sourcePath: sourcePath);
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}
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/// 复制到受管路径并入队；复制失败 → preparationFailed（返回，不抛）。
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Future<UploadTask> _copyAndQueue(
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UploadTask task, {
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required String sourcePath,
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}) async {
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final source = File(sourcePath);
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final target = File(task.sourceFilePath);
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try {
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final expected = await source.length();
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if (expected <= 0) {
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throw StateError('empty source');
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}
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await target.parent.create(recursive: true);
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await source.copy(task.sourceFilePath);
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final copied = await target.length();
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if (copied != expected) {
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// 源在复制期间被改动（相机流水写入中）——按复制失败处理，
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// 用户可重试。
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if (await target.exists()) {
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await target.delete();
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}
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throw StateError('copy size mismatch');
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}
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// 声明值与副本对齐（重试换源场景下行内 bytes 可能是占位值；
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// TaskStore.updateMeta 旁路写入，不迁移状态）。
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if (copied != task.bytes) {
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await _store.updateMeta(task.id, bytes: copied);
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}
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} on Object {
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return _store.updateState(
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task.id,
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UploadTaskState.preparationFailed,
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patch: const UploadTaskPatch(lastError: PrepErrorCodes.copyFailed),
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);
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}
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final queued = await _store.updateState(
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task.id,
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UploadTaskState.queued,
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patch: const UploadTaskPatch(clearLastError: true),
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);
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onEnqueued?.call();
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return queued;
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}
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/// 快速预检：返回失败伪码（null=通过）。
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String? _preCheck({required String? contentType, required int bytes}) {
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if (bytes <= 0) return PrepErrorCodes.sourceUnreadable;
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if (contentType == null) return PrepErrorCodes.unsupportedType;
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if (bytes > maxBytes) return PrepErrorCodes.tooLarge;
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return null;
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}
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/// MIME 嗅探：魔数优先（jpg/png），回退扩展名映射（含无魔数的 heic）。
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///
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/// 返回 null=无法确定白名单内类型（调用方按 unsupportedType 失败）。
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Future<String?> _sniffContentType(String sourcePath, String ext) async {
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try {
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final head = await File(sourcePath).openRead(0, 8).first;
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if (head.length >= 3 &&
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head[0] == 0xFF &&
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head[1] == 0xD8 &&
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head[2] == 0xFF) {
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return 'image/jpeg';
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}
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if (head.length >= 4 &&
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head[0] == 0x89 &&
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head[1] == 0x50 &&
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head[2] == 0x4E &&
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head[3] == 0x47) {
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return 'image/png';
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}
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} on Object {
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// 魔数读取失败（源不存在/权限）：交由 _statBytes→sourceUnreadable。
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}
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return _contentTypeByExt(ext);
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}
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/// 扩展名 → 白名单 MIME（未知扩展返回 null）。
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static String? _contentTypeByExt(String ext) {
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switch (ext) {
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case '.jpg':
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case '.jpeg':
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return 'image/jpeg';
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case '.png':
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return 'image/png';
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case '.heic':
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case '.heif':
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return 'image/heic';
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}
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return null;
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}
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/// stat 源字节数；不可读返回 0（触发 sourceUnreadable 预检失败）。
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Future<int> _statBytes(String sourcePath) async {
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try {
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return await File(sourcePath).length();
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} on Object {
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return 0;
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}
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}
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/// 归一小写扩展名（含点；无扩展返回空串）。
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static String _normalizeExt(String sourcePath) =>
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p.extension(sourcePath).toLowerCase();
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/// 受管目录：{base}/uploads/{accountId}/{albumId}/。
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Future<Directory> _managedDir(String accountId, String albumId) async {
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final base = await _baseDirProvider();
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final dir = Directory(p.join(base.path, 'uploads', accountId, albumId));
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await dir.create(recursive: true);
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return dir;
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}
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/// 32 位十六进制随机 ID（任务 id 与 clientTaskId 各一次生成，
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/// 与 core/device_id.dart 同一编码方式）。
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String _newId() {
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final bytes = List<int>.generate(16, (_) => _random.nextInt(256));
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return DeviceId.hexEncode(bytes);
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}
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}
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