feat(lpt-ai)：异步任务队列 + 提交/轮询路由

lpt-ai 新增异步任务处理能力，LLM 调用改为后台 Worker 顺序执行：

新增 src/task-queue.ts：
- createTask(type, params) → taskId（randomUUID）
- getTask(taskId) → { status, result?, error? }
- 单线程 Worker（setImmediate 链），同一时刻只处理一个 LLM 调用
- 按类型分派到对应的 prompt 函数
- TTL 清理：5 分钟/次，移除完成超过 1 小时的记录
- 异常隔离 + logStore 集成

修改 src/routes/ai.ts：
- POST /ai/tasks：接收 { type, params }，返回 201 { taskId }
- GET /ai/tasks/:taskId：返回任务状态与结果（pending/running/done/failed）
- 旧同步端点完全不动，向后兼容

src/routes/ai.ts

@@ -6,6 +6,7 @@ import type { FastifyInstance } from "fastify";
 import { chat, isAvailable, loadConfig, LlmError } from "../llm/client.js";
 import { aggregateReportPrompt, compareRecallPrompt, generateMindMapPrompt, type FragmentInput } from "../llm/prompts.js";
 import { logStore } from "../admin/store.js";
+import { createTask, getTask, type TaskType } from "../task-queue.js";
 
 interface AggregateReportBody {
   taskName: string;
@@ -173,4 +174,31 @@ export async function aiRoutes(app: FastifyInstance): Promise<void> {
       throw err;
     }
   });
+
+  // ============ 异步任务（提交 + 轮询）============
+
+  /** 提交 AI 任务，立即返回 taskId */
+  app.post<{ Body: { type: string; params: Record<string, unknown> } }>("/ai/tasks", async (request, reply) => {
+    const { type, params } = request.body ?? {};
+
+    if (!type || !["aggregate-report", "generate-mind-map", "compare-recall"].includes(type)) {
+      return reply.status(400).send({ error: "无效的 type，允许: aggregate-report, generate-mind-map, compare-recall" });
+    }
+    if (!params || typeof params !== "object") {
+      return reply.status(400).send({ error: "params 必须为非空对象" });
+    }
+
+    const taskId = createTask(type as TaskType, params as Record<string, unknown>);
+    return reply.status(201).send({ taskId });
+  });
+
+  /** 查询任务状态与结果 */
+  app.get<{ Params: { taskId: string } }>("/ai/tasks/:taskId", async (request, reply) => {
+    const { taskId } = request.params;
+    const task = getTask(taskId);
+    if (!task) {
+      return reply.status(404).send({ error: "任务不存在" });
+    }
+    return task;
+  });
 }

src/task-queue.ts

@@ -0,0 +1,196 @@
+/**
+ * 异步任务队列 —— 接收任务，后台 Worker 顺序处理，提供查询。
+ *
+ * 设计要点：
+ * - 单线程 Worker（setImmediate 链），同一时刻只处理一个 LLM 调用
+ * - TTL 清理：5 分钟一次，移除完成超过 1 小时的记录
+ * - 异常隔离：单个任务失败不影响后续任务
+ * - 日志复用 logStore，与管理面板日志统一
+ */
+
+import { randomUUID } from "node:crypto";
+import { chat, isAvailable, loadConfig, LlmError } from "./llm/client.js";
+import { aggregateReportPrompt, compareRecallPrompt, generateMindMapPrompt } from "./llm/prompts.js";
+import { logStore } from "./admin/store.js";
+
+// ---- 类型 ----
+
+export type TaskType = "aggregate-report" | "generate-mind-map" | "compare-recall";
+
+export type TaskStatus = "pending" | "running" | "done" | "failed";
+
+export interface TaskRecord {
+  id: string;
+  type: TaskType;
+  params: Record<string, unknown>;
+  status: TaskStatus;
+  result?: unknown;
+  error?: string;
+  createdAt: string; // ISO 8601
+  startedAt?: string;
+  completedAt?: string;
+}
+
+// ---- 存储 ----
+
+const records = new Map<string, TaskRecord>();
+const queue: TaskRecord[] = [];
+let processing = false;
+
+// ---- 公开 API ----
+
+export function createTask(type: TaskType, params: Record<string, unknown>): string {
+  const id = randomUUID();
+  const task: TaskRecord = {
+    id,
+    type,
+    params,
+    status: "pending",
+    createdAt: new Date().toISOString(),
+  };
+  records.set(id, task);
+  queue.push(task);
+  setImmediate(() => tryProcessNext());
+  return id;
+}
+
+export function getTask(id: string): TaskRecord | undefined {
+  const t = records.get(id);
+  if (!t) return undefined;
+  // 返回浅拷贝，防止外部修改
+  return { ...t };
+}
+
+// ---- 后台 Worker ----
+
+async function tryProcessNext(): Promise<void> {
+  if (processing || queue.length === 0) return;
+  processing = true;
+
+  const task = queue.shift()!;
+
+  try {
+    task.status = "running";
+    task.startedAt = new Date().toISOString();
+
+    const config = loadConfig();
+
+    if (!isAvailable(config)) {
+      throw new LlmError("LLM API Key 未配置", 503);
+    }
+
+    const messages = buildMessages(task);
+    let callOptions: { temperature?: number; maxTokens?: number } | undefined;
+    if (task.type === "compare-recall") {
+      callOptions = { temperature: 0.2, maxTokens: 4096 };
+    } else if (task.type === "generate-mind-map") {
+      callOptions = { temperature: 0.3, maxTokens: 4096 };
+    } else {
+      callOptions = { temperature: 0.3, maxTokens: 2048 };
+    }
+
+    const raw = await chat(config, messages, callOptions);
+
+    let result: unknown;
+    if (task.type === "aggregate-report") {
+      result = { report: raw.trim(), model: config.model };
+    } else if (task.type === "generate-mind-map") {
+      result = { outline: raw.trim(), model: config.model };
+    } else {
+      // compare-recall: 清理可能的 ```json 包裹
+      const clean = raw.trim().replace(/^```(?:json)?\s*/, "").replace(/\s*```$/, "");
+      result = JSON.parse(clean);
+    }
+
+    task.status = "done";
+    task.result = result;
+    task.completedAt = new Date().toISOString();
+
+    // 记录到管理面板日志
+    logStore.add({
+      timestamp: new Date().toISOString(),
+      endpoint: `/ai/tasks#${task.type}`,
+      model: config.model,
+      durationMs: task.startedAt ? Date.parse(task.completedAt) - Date.parse(task.startedAt) : 0,
+      status: 200,
+      requestBody: task.params,
+      responseBody: result,
+      messages,
+      params: callOptions,
+    });
+
+  } catch (err: unknown) {
+    const errMsg = err instanceof Error ? err.message : String(err);
+    task.status = "failed";
+    task.error = errMsg;
+    task.completedAt = new Date().toISOString();
+
+    const config = loadConfig();
+    logStore.add({
+      timestamp: new Date().toISOString(),
+      endpoint: `/ai/tasks#${task.type}`,
+      model: config.model,
+      durationMs: task.startedAt ? Date.parse(task.completedAt) - Date.parse(task.startedAt) : 0,
+      status: err instanceof LlmError ? err.statusCode : 500,
+      requestBody: task.params,
+      responseBody: {},
+      error: errMsg,
+    });
+  } finally {
+    processing = false;
+    // 处理下一个任务
+    if (queue.length > 0) {
+      setImmediate(() => tryProcessNext());
+    }
+  }
+}
+
+// ---- Prompt 构建 ----
+
+function buildMessages(task: TaskRecord) {
+  const p = task.params;
+  switch (task.type) {
+    case "aggregate-report": {
+      const fragments = p.fragments as Array<{ content: string }> | undefined;
+      return aggregateReportPrompt(
+        p.taskName as string,
+        fragments ?? [],
+        p.expectation as string | undefined,
+      );
+    }
+    case "generate-mind-map": {
+      const reports = p.reports as string[] | undefined;
+      const fragments = p.fragments as string[] | undefined;
+      return generateMindMapPrompt(
+        p.taskName as string,
+        (p.taskDescription as string) ?? "",
+        reports ?? [],
+        fragments ?? [],
+      );
+    }
+    case "compare-recall": {
+      return compareRecallPrompt(
+        p.taskName as string,
+        p.standardOutline as string,
+        p.recallOutline as string,
+      );
+    }
+  }
+}
+
+// ---- TTL 清理 ----
+
+const TTL_MS = 60 * 60 * 1000; // 1 小时
+const CLEANUP_INTERVAL_MS = 5 * 60 * 1000; // 5 分钟
+
+setInterval(() => {
+  const cutoff = Date.now() - TTL_MS;
+  for (const [id, task] of records) {
+    if (task.status === "done" || task.status === "failed") {
+      const completed = task.completedAt ? Date.parse(task.completedAt) : 0;
+      if (completed > 0 && completed < cutoff) {
+        records.delete(id);
+      }
+    }
+  }
+}, CLEANUP_INTERVAL_MS);