refactor: describe asset completion results

backend/app/services/story_service.py

@@ -1,6 +1,8 @@
 """Story business logic service."""
 
 import asyncio
+from dataclasses import dataclass
+from typing import Literal
 
 from fastapi import HTTPException
 from sqlalchemy import desc, select
@@ -40,6 +42,25 @@ from app.tasks.achievements import extract_story_achievements
 
 logger = get_logger(__name__)
 
+AssetCompletionKind = Literal["cover_image", "storybook_images", "audio"]
+
+
+@dataclass(frozen=True)
+class AssetCompletionResult:
+    """Service-level result for a generated asset completion attempt."""
+
+    asset: AssetCompletionKind
+    status: StoryAssetStatus
+    value: str | bytes | None = None
+    error: str | None = None
+    blocks_main_result: bool = False
+
+    @property
+    def succeeded(self) -> bool:
+        """Whether the asset reached a usable ready state."""
+
+        return self.status == StoryAssetStatus.READY and self.error is None
+
 
 def _build_storybook_error_message(
     *,
@@ -281,7 +302,7 @@ async def _complete_cover_image_asset(
     raise_on_failure: bool = False,
     last_error_prefix: str | None = None,
     log_event: str = "cover_asset_generation_failed",
-) -> tuple[str | None, str | None]:
+) -> AssetCompletionResult:
     """Generate or retry a text story cover through one asset workflow."""
 
     if not story.cover_prompt:
@@ -295,7 +316,12 @@ async def _complete_cover_image_asset(
         story.image_url = image_url
         sync_story_status(story, image_status=StoryAssetStatus.READY)
         await db.commit()
-        return image_url, None
+        return AssetCompletionResult(
+            asset="cover_image",
+            status=StoryAssetStatus.READY,
+            value=image_url,
+            blocks_main_result=raise_on_failure,
+        )
     except Exception as exc:
         provider_error = str(exc)
         last_error = (
@@ -317,7 +343,12 @@ async def _complete_cover_image_asset(
                 detail=f"Image generation failed: {provider_error}",
             ) from exc
 
-        return None, provider_error
+        return AssetCompletionResult(
+            asset="cover_image",
+            status=StoryAssetStatus.FAILED,
+            error=provider_error,
+            blocks_main_result=raise_on_failure,
+        )
 
 
 def _get_storybook_pages_data(story: Story) -> list[dict]:
@@ -329,7 +360,7 @@ def _get_storybook_pages_data(story: Story) -> list[dict]:
 async def _complete_storybook_image_assets(
     story: Story,
     db: AsyncSession,
-) -> None:
+) -> AssetCompletionResult:
     """Complete missing cover/page images for a persisted storybook."""
 
     pages_data = _get_storybook_pages_data(story)
@@ -374,20 +405,28 @@ async def _complete_storybook_image_assets(
             )
 
     story.pages = pages_data
-    sync_story_status(
-        story,
-        image_status=_resolve_storybook_image_status(
+    error_message = _build_storybook_error_message(
+        cover_failed=cover_failed,
+        failed_pages=failed_pages,
+    )
+    image_status = _resolve_storybook_image_status(
         generate_images=True,
         cover_prompt=story.cover_prompt,
         cover_url=story.image_url,
         pages_data=pages_data,
-        ),
-        last_error=_build_storybook_error_message(
-            cover_failed=cover_failed,
-            failed_pages=failed_pages,
-        ),
+    )
+    sync_story_status(
+        story,
+        image_status=image_status,
+        last_error=error_message,
     )
     await db.commit()
+    return AssetCompletionResult(
+        asset="storybook_images",
+        status=image_status,
+        value=story.image_url,
+        error=error_message,
+    )
 
 
 async def _read_cached_audio_asset(story: Story, db: AsyncSession) -> bytes | None:
@@ -418,7 +457,7 @@ async def _complete_audio_asset(
     db: AsyncSession,
     *,
     raise_on_failure: bool = True,
-) -> bytes | None:
+) -> AssetCompletionResult:
     """Complete TTS audio generation through one asset workflow."""
 
     if not story.story_text:
@@ -426,7 +465,12 @@ async def _complete_audio_asset(
 
     cached_audio = await _read_cached_audio_asset(story, db)
     if cached_audio is not None:
-        return cached_audio
+        return AssetCompletionResult(
+            asset="audio",
+            status=StoryAssetStatus.READY,
+            value=cached_audio,
+            blocks_main_result=raise_on_failure,
+        )
 
     from app.services.provider_router import text_to_speech
 
@@ -441,7 +485,12 @@ async def _complete_audio_asset(
             audio_status=StoryAssetStatus.READY,
         )
         await db.commit()
-        return audio_data
+        return AssetCompletionResult(
+            asset="audio",
+            status=StoryAssetStatus.READY,
+            value=audio_data,
+            blocks_main_result=raise_on_failure,
+        )
     except Exception as exc:
         provider_error = str(exc)
         story.audio_path = None
@@ -459,7 +508,12 @@ async def _complete_audio_asset(
                 detail=f"Audio generation failed: {provider_error}",
             ) from exc
 
-        return None
+        return AssetCompletionResult(
+            asset="audio",
+            status=StoryAssetStatus.FAILED,
+            error=provider_error,
+            blocks_main_result=raise_on_failure,
+        )
 
 
 async def validate_profile_and_universe(
@@ -550,13 +604,15 @@ async def generate_full_story_service(
     errors: dict[str, str | None] = {}
 
     if story.cover_prompt:
-        image_url, image_error = await _complete_cover_image_asset(
+        image_result = await _complete_cover_image_asset(
             story,
             db,
             log_event="image_generation_failed",
         )
-        if image_error:
-            errors["image"] = image_error
+        if image_result.succeeded and isinstance(image_result.value, str):
+            image_url = image_result.value
+        if image_result.error:
+            errors["image"] = image_result.error
 
     return FullStoryResponse(
         id=story.id,
@@ -854,14 +910,14 @@ async def generate_story_cover(
     """Generate cover image for an existing story."""
     story = await get_story_detail(story_id, user_id, db)
 
-    image_url, _ = await _complete_cover_image_asset(
+    image_result = await _complete_cover_image_asset(
         story,
         db,
         raise_on_failure=True,
         log_event="cover_generation_failed",
     )
-    if image_url is not None:
-        return image_url
+    if image_result.succeeded and isinstance(image_result.value, str):
+        return image_result.value
 
     raise HTTPException(status_code=500, detail="Image generation failed")
 
@@ -874,9 +930,9 @@ async def generate_story_audio(
     """Generate audio for a story."""
     story = await get_story_detail(story_id, user_id, db)
 
-    audio_data = await _complete_audio_asset(story, db, raise_on_failure=True)
-    if audio_data is not None:
-        return audio_data
+    audio_result = await _complete_audio_asset(story, db, raise_on_failure=True)
+    if audio_result.succeeded and isinstance(audio_result.value, bytes):
+        return audio_result.value
 
     raise HTTPException(status_code=500, detail="Audio generation failed")
 

docs/planning/week-1-execution-backlog.md

@@ -69,12 +69,13 @@
   - 普通故事封面生成/重试
   - 绘本缺失插图补全
   - 故事音频缓存读取与 TTS 生成
+- 已引入首版服务层 `AssetCompletionResult`，用于统一表达资产补全结果
 
 ### What Is In Progress
 
 - 统一状态模型与统一外部 API 已落地，内部 service workflow 已开始收束公共步骤
 - 旧生成 API 仍保留为兼容层，后续需要继续降低重复实现
-- 资产补全已经具备统一重试入口首版，封面/绘本插图/音频已有 asset completion helper；后续需要继续抽象 generation job 边界
+- 资产补全已经具备统一重试入口首版，封面/绘本插图/音频已有 asset completion helper 与结果对象；后续需要评估是否落库为 generation job
 
 ### What Is Still Pending
 

docs/product/unified-generation-workflow-prd.md

@@ -43,13 +43,14 @@ DreamWeaver 当前同时支持普通故事生成、完整故事生成和绘本
   - 上下文准备：档案/宇宙校验 + memory context 构建
   - 主记录保存：文本故事与绘本统一持久化入口
   - 资产补全：普通故事封面、绘本缺失插图、故事音频缓存/生成统一封装
+- 已引入首版服务层 `AssetCompletionResult`，用于表达资产补全类型、状态、结果值、错误信息和是否阻塞主结果
 - 故事详情页封面补全已切换到统一资产重试入口
 - 管理端前端构建阻塞已修复，主前端与 admin 前端均可完成生产构建
 
 ### Still Missing
 
 - 普通故事、完整生成、绘本生成已有统一外部入口，内部 workflow 已开始抽取公共步骤，但旧 service 函数仍作为兼容层保留
-- 统一资产重试入口仍是首版：已覆盖普通故事封面、绘本缺失插图、故事音频，并已抽出 asset completion helper，但尚未抽象成完整 generation job 模型
+- 统一资产重试入口仍是首版：已覆盖普通故事封面、绘本缺失插图、故事音频，并已抽出 asset completion helper 与 `AssetCompletionResult`，但尚未落库为完整 generation job 模型
 - `partial_ready`、`retryable_assets` 等更细粒度状态仍停留在目标态
 
 ### What This Means
@@ -65,10 +66,10 @@ DreamWeaver 当前同时支持普通故事生成、完整故事生成和绘本
 DreamWeaver 当前存在以下工作流层面问题：
 
 1. **生成入口已建立，内部路径正在收束**
-   当前前端已切到 `/api/generations`，旧的 `/api/stories/generate`、`/api/stories/generate/full`、`/api/storybook/generate` 仍作为兼容入口保留。service 内部已抽取上下文准备、主记录保存、封面补全、绘本插图补全和音频补全 helper，下一步重点是把这些 helper 组织成更明确的 generation job 边界。
+   当前前端已切到 `/api/generations`，旧的 `/api/stories/generate`、`/api/stories/generate/full`、`/api/storybook/generate` 仍作为兼容入口保留。service 内部已抽取上下文准备、主记录保存、封面补全、绘本插图补全和音频补全 helper，并用 `AssetCompletionResult` 表达资产补全结果。下一步重点是决定这些结果是否需要进一步沉淀为可查询的 generation job。
 
 2. **保存与资产补全过程正在统一**
-   文本故事和绘本已拥有更清晰的主记录保存 helper；普通故事封面、绘本缺失插图、故事音频生成/缓存已共用各自的 asset completion helper。剩余差异集中在还没有统一的 job 对象来描述资产任务。
+   文本故事和绘本已拥有更清晰的主记录保存 helper；普通故事封面、绘本缺失插图、故事音频生成/缓存已共用各自的 asset completion helper。服务层已经能表达资产任务结果，剩余差异集中在还没有持久化 job 对象。
 
 3. **状态表达不统一**  
    系统缺少标准的“生成中、部分完成、已完成、失败、可重试”等状态定义，导致前端难以做出成熟体验。