feat: provide both Atom and RSS feeds, renamed endpoints, WebSub hub links

Endpoints:
- /atom.xml + /rss.xml — all diffs
- /feed/{feedId}/atom.xml + /feed/{feedId}/rss.xml — per source
- /article/{id}/atom.xml + /article/{id}/rss.xml — per article

- Replaced atom-builder.ts with feed-builder.ts (builds both formats)
- Shared feed-entries.ts for consistent entry construction
- WebSub hub link included in Atom (<link rel="hub">) and RSS (<atom:link rel="hub">)
- Autodiscovery <link> tags for both formats in layout head
- Footer links to both Atom and RSS
- RSS icon on homepage links to rss.xml

Author: rmdes

src/lib/server/services/atom-builder.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { buildAtomFeed } from './atom-builder';
+import { buildAtomFeed, buildRssFeed } from './feed-builder';
 
 describe('buildAtomFeed', () => {
 	it('generates valid Atom XML with entries', () => {
@@ -72,4 +72,56 @@ describe('buildAtomFeed', () => {
 		expect(xml).toContain('rel="self"');
 		expect(xml).toContain('type="application/atom+xml"');
 	});
+
+	it('includes WebSub hub link when provided', () => {
+		const xml = buildAtomFeed({
+			id: 'https://example.com/atom.xml',
+			title: 'Test',
+			link: 'https://example.com',
+			updated: '2026-03-29T10:00:00Z',
+			entries: [],
+			hubUrl: 'https://hub.example.com'
+		});
+
+		expect(xml).toContain('rel="hub"');
+		expect(xml).toContain('https://hub.example.com');
+	});
+});
+
+describe('buildRssFeed', () => {
+	it('generates valid RSS 2.0 XML', () => {
+		const xml = buildRssFeed({
+			id: 'https://example.com/rss.xml',
+			title: 'Test RSS',
+			link: 'https://example.com',
+			updated: '2026-03-29T10:00:00Z',
+			entries: [{
+				id: 'https://example.com/diff/1',
+				title: 'Content changed: Article',
+				link: 'https://example.com/diff/1',
+				updated: '2026-03-29T10:00:00Z',
+				summary: 'Test summary'
+			}]
+		});
+
+		expect(xml).toContain('<rss version="2.0"');
+		expect(xml).toContain('<channel>');
+		expect(xml).toContain('<item>');
+		expect(xml).toContain('<pubDate>');
+		expect(xml).toContain('Test RSS');
+	});
+
+	it('includes WebSub hub in RSS', () => {
+		const xml = buildRssFeed({
+			id: 'https://example.com/rss.xml',
+			title: 'Test',
+			link: 'https://example.com',
+			updated: '2026-03-29T10:00:00Z',
+			entries: [],
+			hubUrl: 'https://hub.example.com'
+		});
+
+		expect(xml).toContain('rel="hub"');
+		expect(xml).toContain('https://hub.example.com');
+	});
 });

src/lib/server/services/atom-builder.ts

@@ -0,0 +1,75 @@
+export interface FeedEntry {
+	id: string;
+	title: string;
+	link: string;
+	updated: string;
+	summary: string;
+}
+
+export interface FeedOptions {
+	id: string;
+	title: string;
+	link: string;
+	updated: string;
+	entries: FeedEntry[];
+	hubUrl?: string;
+}
+
+const escape = (s: string) => s
+	.replace(/&/g, '&')
+	.replace(/</g, '&lt;')
+	.replace(/>/g, '&gt;')
+	.replace(/"/g, '&quot;');
+
+export function buildAtomFeed(opts: FeedOptions): string {
+	const hub = opts.hubUrl
+		? `\n  <link href="${escape(opts.hubUrl)}" rel="hub" />`
+		: '';
+
+	const entries = opts.entries.map(e => `  <entry>
+    <id>${escape(e.id)}</id>
+    <title>${escape(e.title)}</title>
+    <link href="${escape(e.link)}" rel="alternate" />
+    <updated>${e.updated}</updated>
+    <summary type="html">${escape(e.summary)}</summary>
+  </entry>`).join('\n');
+
+	return `<?xml version="1.0" encoding="UTF-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom">
+  <id>${escape(opts.id)}</id>
+  <title>${escape(opts.title)}</title>
+  <link href="${escape(opts.link)}" rel="alternate" />
+  <link href="${escape(opts.id)}" rel="self" type="application/atom+xml" />${hub}
+  <updated>${opts.updated}</updated>
+  <generator>NewsDiff</generator>
+${entries}
+</feed>`;
+}
+
+export function buildRssFeed(opts: FeedOptions): string {
+	const hub = opts.hubUrl
+		? `\n    <atom:link href="${escape(opts.hubUrl)}" rel="hub" />`
+		: '';
+
+	const selfLink = `\n    <atom:link href="${escape(opts.id)}" rel="self" type="application/rss+xml" />`;
+
+	const items = opts.entries.map(e => `    <item>
+      <guid isPermaLink="true">${escape(e.id)}</guid>
+      <title>${escape(e.title)}</title>
+      <link>${escape(e.link)}</link>
+      <pubDate>${new Date(e.updated).toUTCString()}</pubDate>
+      <description>${escape(e.summary)}</description>
+    </item>`).join('\n');
+
+	return `<?xml version="1.0" encoding="UTF-8"?>
+<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
+  <channel>
+    <title>${escape(opts.title)}</title>
+    <link>${escape(opts.link)}</link>
+    <description>${escape(opts.title)}</description>
+    <lastBuildDate>${opts.updated ? new Date(opts.updated).toUTCString() : new Date().toUTCString()}</lastBuildDate>
+    <generator>NewsDiff</generator>${selfLink}${hub}
+${items}
+  </channel>
+</rss>`;
+}

src/lib/server/services/feed-builder.ts

@@ -0,0 +1,22 @@
+import type { FeedEntry } from './feed-builder';
+
+/**
+ * Convert a diff record (with relations) to a feed entry.
+ */
+export function diffToFeedEntry(diff: any, origin: string): FeedEntry {
+	const title = diff.newVersion?.title || diff.oldVersion?.title || 'Untitled';
+	const feedName = diff.article?.feed?.name || '';
+	const changes = [
+		diff.titleChanged ? 'headline' : '',
+		diff.contentChanged ? 'content' : ''
+	].filter(Boolean).join(' & ');
+	const changeDesc = changes ? `${changes.charAt(0).toUpperCase() + changes.slice(1)} changed` : 'Updated';
+
+	return {
+		id: `${origin}/diff/${diff.id}`,
+		title: `${changeDesc}: ${title}`,
+		link: `${origin}/diff/${diff.id}`,
+		updated: new Date(diff.createdAt).toISOString(),
+		summary: `${changeDesc} in "${title}" (${feedName}). +${diff.charsAdded} / -${diff.charsRemoved} chars.`
+	};
+}

src/lib/server/services/feed-entries.ts

@@ -35,7 +35,8 @@
 
 <svelte:head>
 	{#if botActorUrl}<link rel="me" href={botActorUrl} />{/if}
-	<link rel="alternate" type="application/atom+xml" title="NewsDiff — All Diffs" href="/feed.xml" />
+	<link rel="alternate" type="application/atom+xml" title="NewsDiff — All Diffs (Atom)" href="/atom.xml" />
+	<link rel="alternate" type="application/rss+xml" title="NewsDiff — All Diffs (RSS)" href="/rss.xml" />
 </svelte:head>
 
 <header>
@@ -76,7 +77,7 @@
 			</a>
 		{/if}
 	</div>
-	<p><a href="https://github.com/rmdes/newsdiff">Source code</a> · <a href="/feed.xml">Atom feed</a></p>
+	<p><a href="https://github.com/rmdes/newsdiff">Source code</a> · <a href="/atom.xml">Atom</a> · <a href="/rss.xml">RSS</a></p>
 </footer>
 
 <!-- Fediverse instance picker modal (shared across pages) -->

src/routes/+layout.svelte

@@ -45,7 +45,7 @@
 				style={data.feedFilter === String(feed.id) ? `background: ${feedColor(feed.name)};` : `border: 1px solid ${feedColor(feed.name)}; color: ${feedColor(feed.name)}; background: transparent;`}
 			>{feed.name}</a>
 		{/each}
-		<a href={data.feedFilter ? `/feed/${data.feedFilter}.xml` : '/feed.xml'}
+		<a href={data.feedFilter ? `/feed/${data.feedFilter}/rss.xml` : '/rss.xml'}
 			class="rss-icon" title="Subscribe to this feed (Atom)">
 			<svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 256 256">
 				<rect width="256" height="256" rx="55" ry="55" fill="#f26522"/>

src/routes/+page.svelte

@@ -10,7 +10,8 @@
 	<a href={article.url} target="_blank" rel="noopener">{article.url}</a>
 	<span>{article.feed.name}</span>
 	<span>{article.versions.length} version{article.versions.length !== 1 ? 's' : ''}</span>
-	<a href="/article/{article.id}/feed.xml" class="feed-link">Atom feed</a>
+	<a href="/article/{article.id}/atom.xml" class="feed-link">Atom</a>
+	<a href="/article/{article.id}/rss.xml" class="feed-link">RSS</a>
 </div>
 
 {#if article.diffs.length > 0}

src/routes/article/[id]/+page.svelte

@@ -0,0 +1,37 @@
+import type { RequestHandler } from './$types';
+import { db } from '$lib/server/db';
+import { diffs, articles } from '$lib/server/db/schema';
+import { eq, desc } from 'drizzle-orm';
+import { error } from '@sveltejs/kit';
+import { buildAtomFeed } from '$lib/server/services/feed-builder';
+import { diffToFeedEntry } from '$lib/server/services/feed-entries';
+
+export const GET: RequestHandler = async ({ params, url }) => {
+	const articleId = Number(params.id);
+	if (isNaN(articleId)) throw error(404, 'Not found');
+
+	const origin = process.env.ORIGIN || url.origin;
+	const article = await db.query.articles.findFirst({ where: eq(articles.id, articleId), with: { feed: true } });
+	if (!article) throw error(404, 'Article not found');
+
+	const articleDiffs = await db.query.diffs.findMany({
+		where: eq(diffs.articleId, articleId),
+		with: { article: { with: { feed: true } }, oldVersion: true, newVersion: true },
+		orderBy: [desc(diffs.createdAt)]
+	});
+
+	const latestTitle = articleDiffs[0]?.newVersion?.title || article.url;
+	const entries = articleDiffs.map(d => diffToFeedEntry(d, origin));
+
+	const xml = buildAtomFeed({
+		id: `${origin}/article/${articleId}/atom.xml`,
+		title: `NewsDiff — ${latestTitle}`,
+		link: `${origin}/article/${articleId}`,
+		updated: entries[0]?.updated || new Date().toISOString(),
+		entries
+	});
+
+	return new Response(xml, {
+		headers: { 'Content-Type': 'application/atom+xml; charset=utf-8', 'Cache-Control': 'public, max-age=300' }
+	});
+};

src/routes/article/[id]/atom.xml/+server.ts

@@ -0,0 +1,37 @@
+import type { RequestHandler } from './$types';
+import { db } from '$lib/server/db';
+import { diffs, articles } from '$lib/server/db/schema';
+import { eq, desc } from 'drizzle-orm';
+import { error } from '@sveltejs/kit';
+import { buildRssFeed } from '$lib/server/services/feed-builder';
+import { diffToFeedEntry } from '$lib/server/services/feed-entries';
+
+export const GET: RequestHandler = async ({ params, url }) => {
+	const articleId = Number(params.id);
+	if (isNaN(articleId)) throw error(404, 'Not found');
+
+	const origin = process.env.ORIGIN || url.origin;
+	const article = await db.query.articles.findFirst({ where: eq(articles.id, articleId), with: { feed: true } });
+	if (!article) throw error(404, 'Article not found');
+
+	const articleDiffs = await db.query.diffs.findMany({
+		where: eq(diffs.articleId, articleId),
+		with: { article: { with: { feed: true } }, oldVersion: true, newVersion: true },
+		orderBy: [desc(diffs.createdAt)]
+	});
+
+	const latestTitle = articleDiffs[0]?.newVersion?.title || article.url;
+	const entries = articleDiffs.map(d => diffToFeedEntry(d, origin));
+
+	const xml = buildRssFeed({
+		id: `${origin}/article/${articleId}/rss.xml`,
+		title: `NewsDiff — ${latestTitle}`,
+		link: `${origin}/article/${articleId}`,
+		updated: entries[0]?.updated || new Date().toISOString(),
+		entries
+	});
+
+	return new Response(xml, {
+		headers: { 'Content-Type': 'application/rss+xml; charset=utf-8', 'Cache-Control': 'public, max-age=300' }
+	});
+};