Cache trending tags (with code copied from Mostr)

src/app.ts

@@ -14,6 +14,7 @@ import {
   serveStatic,
 } from '@/deps.ts';
 import '@/firehose.ts';
+import { Time } from '@/utils.ts';
 
 import { actorController } from './controllers/activitypub/actor.ts';
 import {
@@ -62,6 +63,7 @@ import { nostrController } from './controllers/well-known/nostr.ts';
 import { webfingerController } from './controllers/well-known/webfinger.ts';
 import { auth19, requirePubkey } from './middleware/auth19.ts';
 import { auth98, requireProof, requireRole } from './middleware/auth98.ts';
+import { cache } from './middleware/cache.ts';
 import { csp } from './middleware/csp.ts';
 
 interface AppEnv extends HonoEnv {
@@ -151,8 +153,8 @@ app.get('/api/v2/search', searchController);
 
 app.get('/api/pleroma/frontend_configurations', frontendConfigController);
 
-app.get('/api/v1/trends/tags', trendingTagsController);
-app.get('/api/v1/trends', trendingTagsController);
+app.get('/api/v1/trends/tags', cache({ cacheName: 'web', expires: Time.minutes(15) }), trendingTagsController);
+app.get('/api/v1/trends', cache({ cacheName: 'web', expires: Time.minutes(15) }), trendingTagsController);
 
 app.get('/api/v1/notifications', requirePubkey, notificationsController);
 app.get('/api/v1/favourites', requirePubkey, favouritesController);

src/middleware/cache.ts

@@ -0,0 +1,25 @@
+import ExpiringCache from '@/utils/expiring-cache.ts';
+
+import type { MiddlewareHandler } from '@/deps.ts';
+
+export const cache = (options: {
+  cacheName: string;
+  expires?: number;
+}): MiddlewareHandler => {
+  return async (c, next) => {
+    const key = c.req.url.replace('http://', 'https://');
+    const cache = new ExpiringCache(await caches.open(options.cacheName));
+    const response = await cache.match(key);
+    if (!response) {
+      console.debug('Building cache for page', c.req.url);
+      await next();
+      const response = c.res.clone();
+      if (response.status < 500) {
+        await cache.putExpiring(key, response, options.expires ?? 0);
+      }
+    } else {
+      console.debug('Serving page from cache', c.req.url);
+      return response;
+    }
+  };
+};

src/utils/expiring-cache.test.ts

@@ -0,0 +1,18 @@
+import { assert } from '@/deps-test.ts';
+
+import ExpiringCache from './expiring-cache.ts';
+
+Deno.test('ExpiringCache', async () => {
+  const cache = new ExpiringCache(await caches.open('test'));
+
+  await cache.putExpiring('http://mostr.local/1', new Response('hello world'), 300);
+  await cache.putExpiring('http://mostr.local/2', new Response('hello world'), -1);
+
+  // const resp1 = await cache.match('http://mostr.local/1');
+  const resp2 = await cache.match('http://mostr.local/2');
+
+  // assert(resp1!.headers.get('Expires'));
+  assert(!resp2);
+
+  // await resp1!.text();
+});

src/utils/expiring-cache.ts

@@ -0,0 +1,68 @@
+class ExpiringCache implements Cache {
+  #cache: Cache;
+
+  constructor(cache: Cache) {
+    this.#cache = cache;
+  }
+
+  add(request: RequestInfo | URL): Promise<void> {
+    return this.#cache.add(request);
+  }
+
+  addAll(requests: RequestInfo[]): Promise<void> {
+    return this.#cache.addAll(requests);
+  }
+
+  keys(request?: RequestInfo | URL | undefined, options?: CacheQueryOptions | undefined): Promise<readonly Request[]> {
+    return this.#cache.keys(request, options);
+  }
+
+  matchAll(
+    request?: RequestInfo | URL | undefined,
+    options?: CacheQueryOptions | undefined,
+  ): Promise<readonly Response[]> {
+    return this.#cache.matchAll(request, options);
+  }
+
+  put(request: RequestInfo | URL, response: Response): Promise<void> {
+    return this.#cache.put(request, response);
+  }
+
+  putExpiring(request: RequestInfo | URL, response: Response, expiresIn: number): Promise<void> {
+    const expires = Date.now() + expiresIn;
+
+    const clone = new Response(response.body, {
+      status: response.status,
+      headers: {
+        expires: new Date(expires).toUTCString(),
+        ...Object.fromEntries(response.headers.entries()),
+      },
+    });
+
+    return this.#cache.put(request, clone);
+  }
+
+  async match(request: RequestInfo | URL, options?: CacheQueryOptions | undefined): Promise<Response | undefined> {
+    const response = await this.#cache.match(request, options);
+    const expires = response?.headers.get('Expires');
+
+    if (response && expires) {
+      if (new Date(expires).getTime() > Date.now()) {
+        return response;
+      } else {
+        await Promise.all([
+          this.delete(request),
+          response.text(), // Prevent memory leaks
+        ]);
+      }
+    } else if (response) {
+      return response;
+    }
+  }
+
+  delete(request: RequestInfo | URL, options?: CacheQueryOptions | undefined): Promise<boolean> {
+    return this.#cache.delete(request, options);
+  }
+}
+
+export default ExpiringCache;