From 5d441ebbce6066c3636168ec5332ae9c2bdb8607 Mon Sep 17 00:00:00 2001
From: Adam Soltys <adam@coinos.io>
Date: Thu, 1 Oct 2026 06:55:14 -0700
Subject: Serve a shared snapshot for the public feed

Build the default Popular feed once on the server and let browsers verify and paint its signed events before slow media finishes. Keep custom relays, pagination, filtering, and relay fallback on their existing paths.\n\nAdd stale-while-refresh persistence, service-worker bypass, development integration, and unit/browser coverage.
---
 feed/cache.js | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 feed/cache.js

(limited to 'feed/cache.js')

diff --git a/feed/cache.js b/feed/cache.js
new file mode 100644
index 0000000..4edc017
--- /dev/null
+++ b/feed/cache.js
@@ -0,0 +1,59 @@
+import { PUBLIC_FEED_RELAYS, popularCandidates } from '../src/popular-feed.js';
+import { isMachinePost } from '../src/lang-guess.js';
+
+// One snapshot for all languages; language/mute filtering stays in the browser.
+export async function buildSnapshot(query, now = Date.now) {
+  const notes = new Map();
+  let until;
+  for (let round = 0; round < 3; round++) {
+    const reactions = await query({ kinds: [6, 7, 9735], limit: 600, ...(until ? { until } : {}) });
+    if (!reactions.length) break;
+    until = Math.min(...reactions.map((e) => e.created_at)) - 1;
+    const candidates = popularCandidates(reactions);
+    const batches = [];
+    for (let i = 0; i < candidates.ids.length; i += 40) batches.push(query({ ids: candidates.ids.slice(i, i + 40) }));
+    for (const e of (await Promise.all(batches)).flat()) {
+      if (candidates.qualifies(e) && !isMachinePost(e.content) && JSON.stringify(e).length <= 32_000) notes.set(e.id, e);
+    }
+  }
+  if (!notes.size) throw new Error('No public posts returned; retaining previous snapshot');
+  const posts = [...notes.values()].sort((a, b) => b.created_at - a.created_at);
+  const authors = [...new Set(posts.map((e) => e.pubkey))];
+  const profiles = new Map();
+  for (let i = 0; i < authors.length; i += 100) {
+    for (const e of await query({ kinds: [0], authors: authors.slice(i, i + 100) })) {
+      if (e.kind === 0 && authors.includes(e.pubkey) && JSON.stringify(e).length <= 32_000
+        && (!profiles.has(e.pubkey) || profiles.get(e.pubkey).created_at < e.created_at)) profiles.set(e.pubkey, e);
+    }
+  }
+  return { version: 1, generatedAt: now(), notes: posts, profiles: [...profiles.values()], popUntil: until + 1 };
+}
+
+// Single flight, stale-while-refresh, and a retry delay when relays are down.
+export function createSnapshotCache({ build, initial = null, save = async () => {}, now = Date.now, ttl = 60_000, maxAge = 86400_000, onError = console.error }) {
+  let snapshot = initial, pending = null, retryAt = 0;
+  function refresh() {
+    if (pending) return pending;
+    if (now() < retryAt) return Promise.resolve();
+    pending = Promise.resolve().then(build).then(async (next) => {
+      snapshot = next;
+      await save(next);
+    }).catch(onError).finally(() => { pending = null; retryAt = now() + 15_000; });
+    return pending;
+  }
+  function read() {
+    if (!snapshot || now() - snapshot.generatedAt >= ttl) void refresh();
+    return snapshot && now() - snapshot.generatedAt <= maxAge ? snapshot : null;
+  }
+  return { read, refresh };
+}
+
+export function snapshotResponse(cache, req) {
+  if (!['GET', 'HEAD'].includes(req.method)) return new Response(null, { status: 405, headers: { Allow: 'GET, HEAD' } });
+  const snapshot = cache.read();
+  if (!snapshot) return new Response(null, { status: 503, headers: { 'Retry-After': '15', 'Cache-Control': 'no-store' } });
+  return new Response(req.method === 'HEAD' ? null : JSON.stringify(snapshot), {
+    headers: { 'Content-Type': 'application/json', 'Cache-Control': 'public, max-age=15, stale-while-revalidate=60' },
+  });
+}
+export { PUBLIC_FEED_RELAYS };
-- 
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