feat: add generation job cancel and retry queue

backend/app/services/generation_jobs.py

@@ -16,6 +16,26 @@ from app.db.models import GenerationJob, GenerationJobEvent, Story
 logger = get_logger(__name__)
 
 
+def _is_terminal_status(status: str) -> bool:
+    return status in {"completed", "degraded_completed", "failed", "canceled"}
+
+
+def _job_supports_queue_control(job: GenerationJob) -> bool:
+    return job.output_mode in {"story", "storybook"}
+
+
+def generation_job_can_cancel(job: GenerationJob) -> bool:
+    return (
+        _job_supports_queue_control(job)
+        and job.status == "running"
+        and job.current_step != "cancel_requested"
+    )
+
+
+def generation_job_can_retry(job: GenerationJob) -> bool:
+    return _job_supports_queue_control(job) and job.status in {"failed", "canceled"}
+
+
 def _story_snapshot(story: Story | None) -> dict[str, Any]:
     if story is None:
         return {}
@@ -50,6 +70,13 @@ def _job_progress(job: GenerationJob) -> dict[str, Any]:
             "is_terminal": True,
         }
 
+    if job.status == "canceled":
+        return {
+            "progress_percent": 100,
+            "progress_label": "已取消",
+            "is_terminal": True,
+        }
+
     if job.status in {"completed", "degraded_completed"}:
         return {
             "progress_percent": 100,
@@ -59,7 +86,9 @@ def _job_progress(job: GenerationJob) -> dict[str, Any]:
 
     progress_map: dict[str, tuple[int, str]] = {
         "request_accepted": (5, "已接收请求"),
+        "retry_queued": (8, "重新排队中"),
         "worker_started": (12, "后台任务已开始"),
+        "cancel_requested": (15, "已请求取消"),
         "context_prepared": (20, "上下文已准备"),
         "narrative_generated": (45, "正文已生成"),
         "story_saved": (60, "主记录已保存"),
@@ -83,6 +112,7 @@ def _job_progress(job: GenerationJob) -> dict[str, Any]:
         "postprocessing_queued": (90, "后处理已排队"),
         "asset_generation_completed": (100, "资源已完成"),
         "asset_retry_completed": (100, "资源重试完成"),
+        "generation_canceled": (100, "任务已取消"),
         "generation_completed": (100, "生成完成"),
         "generation_stale_failed": (100, "任务超时已收敛"),
     }
@@ -106,6 +136,8 @@ def _is_stale_job(job: GenerationJob, *, stale_after_minutes: int) -> bool:
 
 
 def _failure_label(job: GenerationJob) -> str:
+    if job.status == "canceled":
+        return "任务已取消"
     if job.current_step == "generation_stale_failed":
         return "任务超时"
     if job.output_mode == "asset_retry":
@@ -196,7 +228,7 @@ async def claim_generation_job_for_worker(
         .where(
             GenerationJob.id == job_id,
             GenerationJob.status == "running",
-            GenerationJob.current_step == "request_accepted",
+            GenerationJob.current_step.in_(["request_accepted", "retry_queued"]),
         )
         .values(current_step="worker_started")
     )
@@ -283,6 +315,8 @@ def generation_job_to_summary(job: GenerationJob) -> dict[str, Any]:
         "status": job.status,
         "current_step": job.current_step,
         **progress,
+        "can_cancel": generation_job_can_cancel(job),
+        "can_retry": generation_job_can_retry(job),
         "result_snapshot": job.result_snapshot or {},
         "error_message": job.error_message,
         "created_at": job.created_at,
@@ -290,6 +324,88 @@ def generation_job_to_summary(job: GenerationJob) -> dict[str, Any]:
     }
 
 
+async def get_generation_job_for_user(
+    db: AsyncSession,
+    *,
+    job_id: str,
+    user_id: str,
+) -> GenerationJob:
+    """Load one generation job owned by the current user."""
+
+    result = await db.execute(
+        select(GenerationJob).where(
+            GenerationJob.id == job_id,
+            GenerationJob.user_id == user_id,
+        )
+    )
+    job = result.scalar_one_or_none()
+    if job is None:
+        raise HTTPException(status_code=404, detail="Generation job not found")
+    return job
+
+
+async def request_generation_job_cancel(
+    db: AsyncSession,
+    *,
+    job_id: str,
+    user_id: str,
+) -> dict[str, Any]:
+    """Request cancellation for one queued/running generation job."""
+
+    job = await get_generation_job_for_user(db, job_id=job_id, user_id=user_id)
+
+    if not _job_supports_queue_control(job):
+        raise HTTPException(status_code=409, detail="当前任务不支持取消")
+
+    if job.status == "canceled":
+        return generation_job_to_summary(job)
+
+    if _is_terminal_status(job.status):
+        raise HTTPException(status_code=409, detail="当前任务已终止，无法取消")
+
+    if job.current_step == "cancel_requested":
+        return generation_job_to_summary(job)
+
+    if job.current_step in {"request_accepted", "retry_queued"}:
+        story = None
+        if job.story_id is not None:
+            story = (
+                await db.execute(
+                    select(Story).where(
+                        Story.id == job.story_id,
+                        Story.user_id == job.user_id,
+                    )
+                )
+            ).scalar_one_or_none()
+
+        await finish_generation_job(
+            db,
+            job=job,
+            story=story,
+            status="canceled",
+            current_step="generation_canceled",
+            error_message="Generation canceled by user before worker execution started.",
+            message="Generation job was canceled before worker execution started.",
+        )
+        return generation_job_to_summary(job)
+
+    previous_step = job.current_step
+    job.error_message = "Cancellation requested by user."
+    await record_generation_event(
+        db,
+        job=job,
+        story_id=job.story_id,
+        event_type="cancel_requested",
+        status="running",
+        message="Cancellation requested; worker will stop at the next safe checkpoint.",
+        metadata={"requested_from_step": previous_step},
+        commit=False,
+    )
+    await db.commit()
+    await db.refresh(job)
+    return generation_job_to_summary(job)
+
+
 async def get_generation_job_detail(
     db: AsyncSession,
     *,