feat(cache): TTL

Author: aster-void

src/lib/cache.ts

@@ -1,27 +1,43 @@
 import fs from "node:fs/promises";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
-import type { Schema } from "astro/zod";
+import { type Schema, z } from "zod";
+
+// 1 week
+const DEFAULT_TTL = 7 * 24 * 60 * 60;
+const Meta = z.object({
+  writtenAt: z.number(),
+});
+type Meta = z.infer<typeof Meta>;
 /**
   - this uses FS to cache. only use this for expensive things that need FS caching (such as fetching from the Internet)
   - this does not cache `null` or `undefined`.
   */
 export async function cache<T>(
   key: string,
-  schema: Schema<T>,
+  Schema: Schema<T>,
   load: () => Promise<T>,
+  /** ttl: time-to-live in seconds */
+  options: {
+    ttl?: number;
+  } = {},
 ): Promise<T> {
+  const ttl = options.ttl ?? DEFAULT_TTL;
+  const now = new Date().getTime() / 1000;
   const path = await toPath(sanitizeKey(key));
 
   // cache load
   if (await exists(path)) {
     try {
-      const file = await fs.readFile(path, {
-        encoding: "utf8",
-      });
-      const val = schema.parse(JSON.parse(file));
+      const file = JSON.parse(
+        await fs.readFile(path, {
+          encoding: "utf8",
+        }),
+      );
+      const data = Schema.parse(file.data);
+      const meta = Meta.parse(file.meta);
       // cache hit
-      return val;
+      if (now - meta.writtenAt <= ttl) return data;
     } catch (err) {
       console.warn("failed to parse retrieved cache:", err);
     }
@@ -30,11 +46,17 @@ export async function cache<T>(
   // cache miss
   const val = await load();
 
-  const parse = schema.safeParse(val);
+  const parse = Schema.safeParse(val);
   if (parse.success) {
     if (val != null) {
       // write cache
-      await fs.writeFile(path, JSON.stringify(val));
+      const content = {
+        data: val,
+        meta: {
+          writtenAt: now,
+        } satisfies Meta,
+      };
+      await fs.writeFile(path, JSON.stringify(content));
     }
   } else {
     // skip lcache