app/lib/feed-response.ts

Functions

Imports

It imports app/db/index.ts, app/lib/seo.ts, app/lib/series-path.mjs, app/lib/tag-path.mjs. Imported by app/routes/blog.atom[.xml].ts, app/routes/blog.feed[.json].ts, app/routes/blog.rss[.xml].ts, app/routes/blog.series.$series.feed[.json].ts, app/routes/blog.series.$series.rss[.xml].ts, app/routes/blog.tags.$tag.feed[.json].ts, app/routes/blog.tags.$tag.rss[.xml].ts.

Source

1import { listBlogPostsFullText, listBlogPostsRendered, nextScheduledPublishAt } from "~/db";
2import { atomDocument, jsonFeedDocument, rssDocument } from "@drdustinedwards/site-helpers";
3import {
4  EDGE_CACHE_HEADER,
5  SHARED_CACHE_CONTROL,
6  SITE,
7  SITE_ORIGIN,
8  cacheTags,
9  scheduledEdgeCacheControl,
10} from "~/lib/seo";
11import { seriesPath } from "~/lib/series-path.mjs";
12import { tagPath } from "~/lib/tag-path.mjs";
13
14export type FeedFormat = "json" | "rss" | "atom";
15
16/** check:headers reads these literals and asserts isUnpolicedType() exempts each from the CSP. */
17const FEED_CONTENT_TYPES = {
18  /*
19   * `application/json`, not `application/feed+json`: Cloudflare does not compress `+json` types, and
20   * this is the largest response on the site. Readers identify it by the `version` member.
21   */
22  json: "application/json; charset=utf-8",
23  rss: "application/rss+xml; charset=utf-8",
24  atom: "application/atom+xml; charset=utf-8",
25} as const;
26
27const FEED_FILES = { json: "feed.json", rss: "rss.xml", atom: "atom.xml" } as const;
28
29const FEED_ITEMS = 20;
30
31/** What one feed covers: its page, its title and blurb, and which posts it lists in what order. */
32interface FeedScope {
33  path: string;
34  title: string;
35  description: string;
36  list: Parameters<typeof listBlogPostsFullText>[1];
37}
38
39export const blogFeed: FeedScope = {
40  path: "/writing",
41  title: `${SITE.name} blog`,
42  description: "Writing on building for the web, mostly on Cloudflare.",
43  list: { perPage: FEED_ITEMS },
44};
45
46/** 404 on an unknown tag stays with the route: a feed and its page must agree about whether a tag exists. */
47export function tagFeed(tag: { slug: string; name: string }): FeedScope {
48  return {
49    path: tagPath(tag.slug),
50    title: `${SITE.name} blog: ${tag.name}`,
51    description: `Posts tagged ${tag.name}.`,
52    list: { perPage: FEED_ITEMS, tag: tag.slug },
53  };
54}
55
56/** Ordered by part, not date, and uncapped: a subscriber receives part one first and loses no later part. */
57export function seriesFeed(series: { name: string }): FeedScope {
58  return {
59    path: seriesPath(series.name),
60    title: `${SITE.name} blog: ${series.name}`,
61    description: `Every part of ${series.name}, in order.`,
62    list: { series: series.name, orderBy: "part" },
63  };
64}
65
66/** One feed document for a scope, in JSON Feed, RSS or Atom, shared-cached. */
67export async function feedResponse(env: Env, format: FeedFormat, scope: FeedScope) {
68  const pageUrl = `${SITE_ORIGIN}${scope.path}`;
69  const selfUrl = `${pageUrl}/${FEED_FILES[format]}`;
70
71  let body: string;
72  if (format === "json") {
73    const posts = await listBlogPostsFullText(env, scope.list);
74    const feed = jsonFeedDocument({
75      title: scope.title,
76      homePageUrl: pageUrl,
77      feedUrl: selfUrl,
78      description: scope.description,
79      authorName: SITE.name,
80      posts,
81      origin: SITE_ORIGIN,
82    });
83    body = `${JSON.stringify(feed, null, 2)}\n`;
84  } else {
85    const posts = await listBlogPostsRendered(env, scope.list);
86    body =
87      format === "rss"
88        ? rssDocument({
89            title: scope.title,
90            link: pageUrl,
91            description: scope.description,
92            selfUrl,
93            posts,
94            origin: SITE_ORIGIN,
95          })
96        : atomDocument({
97            title: scope.title,
98            subtitle: scope.description,
99            alternateUrl: pageUrl,
100            selfUrl,
101            authorName: SITE.name,
102            posts,
103            origin: SITE_ORIGIN,
104          });
105  }
106
107  const nextPublishAt = await nextScheduledPublishAt(env);
108
109  return new Response(body, {
110    headers: {
111      "content-type": FEED_CONTENT_TYPES[format],
112      "cache-control": SHARED_CACHE_CONTROL,
113      // Every scope lists posts only, so a posts purge (a save, a delete) must reach it.
114      "cache-tag": cacheTags(),
115      [EDGE_CACHE_HEADER]: scheduledEdgeCacheControl(new Date(), nextPublishAt),
116    },
117  });
118}