feeds: an Atom feed of new sources per category

The only feeds covered the whole catalog. A reader who only wants audio or
fonts had to follow every new source.

The build now writes category/<id>/feed.xml: the newest non-deprecated
entries in that category by `added`, built by atomFeed with its own id,
title, self and alternate links. Each category page advertises its feed in
<head> and links it beside the catalog-search link. docs/data.md lists the
new files.

Closes #214

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LpkeXRUqm7oDedPDk3QWtK

Author: TMHSDigital

docs/data.md

@@ -12,6 +12,7 @@ The catalog is published as machine-readable files on every deploy. The metadata
 | [`catalog.csv`](https://tmhsdigital.github.io/Free-Game-Dev-Assets/catalog.csv) | One row per entry, for spreadsheets. Lists are joined with `; ` |
 | [`feed.xml`](https://tmhsdigital.github.io/Free-Game-Dev-Assets/feed.xml) | Atom feed of newly added sources |
 | [`reverified.xml`](https://tmhsdigital.github.io/Free-Game-Dev-Assets/reverified.xml) | Atom feed of entries whose licence was most recently re-read |
+| `category/<id>/feed.xml` | Atom feed of new sources in one category, such as [`category/audio/feed.xml`](https://tmhsdigital.github.io/Free-Game-Dev-Assets/category/audio/feed.xml); each category page links its own |
 | [`llms.txt`](https://tmhsdigital.github.io/Free-Game-Dev-Assets/llms.txt) | A plain-text summary for language-model tools |
 
 These URLs always serve the latest build. To pin a version, download the same files from a tagged [release](https://github.com/TMHSDigital/Free-Game-Dev-Assets/releases). Releases are tagged `vYYYY.MM.DD`, and the attached `data.json` carries the same string as `version`.

site/build.mjs

@@ -634,6 +634,11 @@ function main() {
   writeOut("catalog.csv", catalogCsv(entries, config.site.siteUrl));
   writeOut("feed.xml", atomFeed({ entries, site: config.site, generatedAt: payload.generatedAt, kind: "added" }));
   writeOut("reverified.xml", atomFeed({ entries, site: config.site, generatedAt: payload.generatedAt, kind: "verified" }));
+  // New sources per category, linked from each category page.
+  for (const [id, meta] of Object.entries(config.categories)) {
+    if (!entries.some((e) => e.category === id)) continue;
+    writeOut(path.join("category", id, "feed.xml"), atomFeed({ entries, site: config.site, generatedAt: payload.generatedAt, kind: "added", category: { id, label: meta.label || id } }));
+  }
 
   // Prerender. The served HTML must be complete without JavaScript: this is a
   // catalog whose whole value is that its entries can be found.

site/lib/category-page.mjs

@@ -48,6 +48,7 @@ export function categoryPageHtml({ cat, meta, entries, site, stamp, total, hasCa
     <title>${esc(clipText(title, SEO_TITLE_MAX))}</title>
     <meta name="description" content="${esc(description)}" />
     ${baseHeadHtml({ site, title, description, url, hasCard, root: "../../", modules: PAGE_MODULES.category })}
+    <link rel="alternate" type="application/atom+xml" title="${esc(`${site.title}: new sources in ${label}`)}" href="${esc(`${url}feed.xml`)}" />
     <script type="application/ld+json">${scriptJson(categoryJsonLd({ cat, label, description, entries, site }))}</script>
   </head>
   <body>
@@ -60,7 +61,7 @@ export function categoryPageHtml({ cat, meta, entries, site, stamp, total, hasCa
       </nav>
       <h1>${esc(label)}</h1>
       <p class="section-blurb">${esc(sources)} · ${esc(blurb)}</p>
-      <p class="category-search"><a href="../../?cat=${encodeURIComponent(cat)}#catalog">Search and filter on the catalog page</a></p>
+      <p class="category-search"><a href="../../?cat=${encodeURIComponent(cat)}#catalog">Search and filter on the catalog page</a> · <a href="feed.xml">Feed of new ${esc(label)} sources</a></p>
       <div class="entry-list" id="entry-grid">
 ${grid}
       </div>

site/lib/exports.mjs

@@ -114,12 +114,17 @@ export const FEEDS = {
  * feed.xml) or "verified" (licence re-reads, reverified.xml). Two feeds, so
  * a re-verification sweep of old entries cannot bury the new ones.
  */
-export function atomFeed({ entries, site, generatedAt, limit = 40, kind = "added" }) {
+export function atomFeed({ entries, site, generatedAt, limit = 40, kind = "added", category = null }) {
   const spec = FEEDS[kind];
   if (!spec) throw new Error(`atomFeed: unknown kind "${kind}"`);
   const base = site.siteUrl.replace(/\/+$/, "");
+  // A category feed (category/<id>/feed.xml): new sources in that category only.
+  const file = category ? `category/${category.id}/feed.xml` : spec.file;
+  const home = category ? `${base}/category/${category.id}/` : `${base}/`;
+  const feedTitle = category ? `${spec.title} in ${category.label}` : spec.title;
+  const feedId = category ? `${base}/${file}` : `${base}/${kind === "added" ? "" : spec.file}`;
   const recent = entries
-    .filter((e) => e.status !== "deprecated" && e[kind])
+    .filter((e) => (!category || e.category === category.id) && e.status !== "deprecated" && e[kind])
     .sort((a, b) => String(b[kind]).localeCompare(String(a[kind])) || a.name.localeCompare(b.name))
     .slice(0, limit);
   const items = recent.map((e) => {
@@ -137,13 +142,13 @@ export function atomFeed({ entries, site, generatedAt, limit = 40, kind = "added
   return [
     '<?xml version="1.0" encoding="UTF-8"?>',
     '<feed xmlns="http://www.w3.org/2005/Atom">',
-    `  <id>${esc(base)}/${kind === "added" ? "" : spec.file}</id>`,
-    `  <title>${esc(site.title)}: ${spec.title}</title>`,
+    `  <id>${esc(feedId)}</id>`,
+    `  <title>${esc(site.title)}: ${esc(feedTitle)}</title>`,
     `  <subtitle>${esc(`${site.tagline} ${spec.what[0].toUpperCase()}${spec.what.slice(1)}.`)}</subtitle>`,
     // RFC 4287 4.1.1: a feed-level author covers every entry.
     `  <author><name>${esc(site.title)}</name><uri>${esc(base)}/</uri></author>`,
-    `  <link href="${esc(base)}/" />`,
-    `  <link rel="self" href="${esc(base)}/${spec.file}" />`,
+    `  <link href="${esc(home)}" />`,
+    `  <link rel="self" href="${esc(base)}/${file}" />`,
     `  <updated>${esc(generatedAt)}</updated>`,
     ...items,
     "</feed>",

site/lib/lib.test.mjs

@@ -691,6 +691,15 @@ eq("new-sources feed is by added, newest first", newFeed.indexOf("entry/c/") < n
 has("new-sources feed is the default feed.xml", newFeed, '<link rel="self" href="https://s.test/site/feed.xml" />');
 has("new-sources feed uses the added date", newFeed, "<updated>2026-09-20T00:00:00Z</updated>");
 has("new-sources feed title", newFeed, "<title>T: new sources</title>");
+{
+  const catFeed = atomFeed({ entries: sample, site: { title: "T", tagline: "t", siteUrl: "https://s.test/site/" }, generatedAt: "2026-10-01T00:00:00.000Z", category: { id: sample[0].category, label: "Cat & Co" } });
+  const others = sample.filter((e) => e.category !== sample[0].category && e.status !== "deprecated");
+  has("category feed names itself", catFeed, `<link rel="self" href="https://s.test/site/category/${sample[0].category}/feed.xml" />`);
+  has("category feed links its page", catFeed, `<link href="https://s.test/site/category/${sample[0].category}/" />`);
+  has("category feed title escapes the label", catFeed, "<title>T: new sources in Cat &amp; Co</title>");
+  has("category feed keeps its own entries", catFeed, `entry/${sample[0].id}/`);
+  for (const e of others) lacks(`category feed leaves out ${e.id}`, catFeed, `entry/${e.id}/`);
+}
 
 /* review fixes, 2026-10 (#59-#66) ------------------------------------------ */
 import { csvField } from "./exports.mjs";