feat: 添加分页功能和缓存管理，优化问答记录展示

server/utils/cache.ts

@@ -1,100 +0,0 @@
-// server/utils/cache.ts - 简单内存缓存，按题目、题型和选项生成缓存键
-import { createHash } from "node:crypto";
-
-import { serverEnv } from "~~/server/utils/env";
-
-/**
- * 旧 Python 服务使用进程内字典缓存答案
- *
- * Nuxt 版保持同样的“内存缓存”语义：服务重启后缓存清空，不跨实例共享；
- * 这对个人题库服务足够简单，也避免为了缓存引入数据库或 Redis
- */
-export class SimpleCache {
-  /** Map key 是题目、题型和选项计算出的 md5；value 保存写入时间和答案 */
-  private readonly cache = new Map<
-    string,
-    {
-      timestamp: number;
-      value: string;
-    }
-  >();
-
-  constructor(private readonly expirationSeconds: number) {}
-
-  /**
-   * 根据题目、题型和选项生成缓存键
-   *
-   * 同一道题如果选项不同，不能复用旧答案，所以三个字段都参与计算
-   */
-  private generateKey(question: string, questionType = "", options = "") {
-    return createHash("md5")
-      .update(`${question}|${questionType}|${options}`, "utf8")
-      .digest("hex");
-  }
-
-  /**
-   * 读取缓存答案
-   *
-   * 命中过期项时会顺手删除，避免长时间运行后堆积无效缓存
-   */
-  get(question: string, questionType = "", options = "") {
-    const key = this.generateKey(question, questionType, options);
-    const item = this.cache.get(key);
-    if (!item) return undefined;
-
-    if (Date.now() - item.timestamp < this.expirationSeconds * 1000) {
-      return item.value;
-    }
-
-    this.cache.delete(key);
-    return undefined;
-  }
-
-  /** 写入答案缓存，时间戳使用当前进程时间即可 */
-  set(question: string, answer: string, questionType = "", options = "") {
-    const key = this.generateKey(question, questionType, options);
-    this.cache.set(key, {
-      timestamp: Date.now(),
-      value: answer
-    });
-  }
-
-  /** 清空全部缓存，对应 `/api/cache/clear` */
-  clear() {
-    this.cache.clear();
-  }
-
-  /**
-   * 批量移除过期项
-   *
-   * 目前在统计缓存大小时调用，避免 stats 返回已经过期的数量
-   */
-  removeExpired() {
-    const now = Date.now();
-    let removedCount = 0;
-
-    for (const [key, item] of this.cache.entries()) {
-      if (now - item.timestamp >= this.expirationSeconds * 1000) {
-        this.cache.delete(key);
-        removedCount += 1;
-      }
-    }
-
-    return removedCount;
-  }
-
-  /** 获取当前有效缓存数量 */
-  size() {
-    this.removeExpired();
-    return this.cache.size;
-  }
-}
-
-/**
- * 全局答案缓存实例
- *
- * 如果 `ENABLE_CACHE=false`，导出 undefined，调用处用可选链即可保持逻辑简洁
- */
-export const answerCache = serverEnv.enableCache
-  ? new SimpleCache(serverEnv.cacheExpiration)
-  : undefined;

server/utils/env.ts

@@ -73,10 +73,6 @@ export const serverEnv = {
   maxTokens: readInteger("MAX_TOKENS", 500),
   /** 模型采样温度，越低越稳定 */
   temperature: readNumber("TEMPERATURE", 0.7),
-  /** 是否启用内存缓存 */
-  enableCache: readBoolean("ENABLE_CACHE", true),
-  /** 缓存过期时间，单位秒 */
-  cacheExpiration: readInteger("CACHE_EXPIRATION", 86_400),
   /** 预留日志级别配置，目前日志工具只负责安全输出 */
   logLevel: readString("LOG_LEVEL", "INFO"),
   /** 单行 SSE data 的最大字节数，用于防止异常流无限堆内存 */

server/utils/runtimeState.ts

@@ -1,5 +1,4 @@
 // server/utils/runtimeState.ts - 服务启动时间内存状态 + 问答记录 DB 读写
-import { answerCache } from "~~/server/utils/cache";
 import { prisma } from "~~/server/utils/db";
 import { serverEnv } from "~~/server/utils/env";
 
@@ -29,6 +28,7 @@ export const addQaRecord = async (record: {
   type: string;
   options: string;
   answer: string;
+  hash: string;
 }) => {
   await prisma.qaRecord.create({
     data: {
@@ -36,11 +36,34 @@ export const addQaRecord = async (record: {
       question: record.question,
       type: record.type,
       options: record.options || null,
-      answer: record.answer || null
+      answer: record.answer || null,
+      hash: record.hash
     }
   });
 };
 
+/**
+ * 按用户 + hash 查找 DB 缓存答案
+ *
+ * 只返回 cacheClearedAt 之后写入的记录；未存入时间或 hash 为 null 的老记录不会命中
+ */
+export const lookupCachedAnswer = async (
+  userId: string,
+  hash: string,
+  cacheClearedAt: Date | null
+): Promise<string | null> => {
+  const record = await prisma.qaRecord.findFirst({
+    where: {
+      userId,
+      hash,
+      ...(cacheClearedAt ? { createdAt: { gt: cacheClearedAt } } : {})
+    },
+    orderBy: { createdAt: "desc" },
+    select: { answer: true }
+  });
+  return record?.answer ?? null;
+};
+
 /**
  * 从数据库分页读取指定用户的问答记录，按创建时间倒序
  */
@@ -76,13 +99,11 @@ export const getQaRecords = async (
   }));
   return { records, total };
 };
-/** 生成 `/api/stats` 响应，实时计算 uptime 和有效缓存数量 */
+/** 生成 `/api/stats` 的基础运行时信息，不包含用户相关数据 */
 export const getRuntimeStats = () => {
   return {
     version: SERVICE_VERSION,
     uptime: (Date.now() - startTime) / 1000,
-    model: serverEnv.openAiModel,
-    cache_enabled: serverEnv.enableCache,
-    cache_size: answerCache?.size() ?? 0
+    model: serverEnv.openAiModel
   };
 };