feat(cache): 新增 store-factory（CACHE_DRIVER 切换）

src/shared/lib/cache/store-factory.ts

@@ -0,0 +1,36 @@
+import "server-only"
+
+import { env } from "@/env.mjs"
+
+import type { CacheStore } from "./types"
+import { MemoryCacheStore } from "./memory-store"
+
+let singleton: CacheStore | null = null
+let loadPromise: Promise<CacheStore> | null = null
+
+/**
+ * 获取当前进程的 CacheStore 实例。
+ *
+ * - 默认返回 MemoryCacheStore
+ * - 当 CACHE_DRIVER=redis 时动态加载 RedisCacheStore
+ * - Redis 实现懒加载 @upstash/redis 依赖，未安装时首次调用抛错
+ *
+ * 返回 Promise：Redis 实现需动态 import 模块，故为异步。
+ */
+export async function getCacheStore(): Promise<CacheStore> {
+  if (singleton) return singleton
+  if (loadPromise) return loadPromise
+
+  loadPromise = (async () => {
+    if (env.CACHE_DRIVER === "redis") {
+      const { RedisCacheStore } = await import("./redis-store")
+      singleton = new RedisCacheStore()
+    } else {
+      singleton = new MemoryCacheStore()
+    }
+    loadPromise = null
+    return singleton
+  })()
+
+  return loadPromise
+}