feat(blog/nuldoc): implement generating Atom feed

2 files changed, 105 insertions, 0 deletions

diff --git a/vhosts/blog/nuldoc-src/atom/generate.ts b/vhosts/blog/nuldoc-src/atom/generate.ts
new file mode 100644
index 00000000..cb425aba
--- /dev/null
+++ b/vhosts/blog/nuldoc-src/atom/generate.ts
@@ -0,0 +1,86 @@
+import { Config } from "../config.ts";
+import { el, text } from "../dom.ts";
+import { Page } from "../page.ts";
+import { Entry, Feed } from "./types.ts";
+import { PostPage } from "../pages/post.ts";
+import { SlidePage } from "../pages/slide.ts";
+import { dateToRfc3339String } from "../revision.ts";
+
+const BASE_NAME = "atom.xml";
+
+export function generateFeedPageFromEntries(
+  alternateLink: string,
+  feedSlug: string,
+  feedTitle: string,
+  entries: Array<PostPage | SlidePage>,
+  config: Config,
+): Page {
+  const entries_: Entry[] = [];
+  for (const entry of entries) {
+    entries_.push({
+      id: `urn:uuid:${entry.uuid}`,
+      linkToAlternate: `https://${config.blog.fqdn}${entry.href}`,
+      title: entry.title,
+      summary: entry.description,
+      published: dateToRfc3339String(entry.published),
+      updated: dateToRfc3339String(entry.updated),
+    });
+  }
+  // Sort by published date in ascending order.
+  entries_.sort((a, b) => {
+    if (a.published < b.published) {
+      return 1;
+    } else if (a.published > b.published) {
+      return -1;
+    }
+    return 0;
+  });
+  const feedPath = `${alternateLink}${BASE_NAME}`;
+  const feed: Feed = {
+    author: config.blog.author,
+    icon: `https://${config.blog.fqdn}/favicon.svg`,
+    id: `tag:${config.blog.fqdn},${config.blog.siteCopyrightYear}:${feedSlug}`,
+    linkToSelf: `https://${config.blog.fqdn}${feedPath}`,
+    linkToAlternate: `https://${config.blog.fqdn}${alternateLink}`,
+    title: feedTitle,
+    updated: entries_.reduce(
+      (latest, entry) => entry.updated > latest ? entry.updated : latest,
+      entries_[0].updated,
+    ),
+    entries: entries_,
+  };
+
+  const xml = buildXmlTree(feed);
+  return {
+    root: el("__root__", [], xml),
+    renderer: "xml",
+    destFilePath: feedPath,
+    href: feedPath,
+  };
+}
+
+function buildXmlTree(feed: Feed) {
+  return el(
+    "feed",
+    [["xmlns", "http://www.w3.org/2005/Atom"]],
+    el("id", [], text(feed.id)),
+    el("title", [], text(feed.title)),
+    el("link", [["rel", "alternate"], ["href", feed.linkToAlternate]]),
+    el("link", [["rel", "self"], ["href", feed.linkToSelf]]),
+    el("author", [], el("name", [], text(feed.author))),
+    el("updated", [], text(feed.updated)),
+    ...feed.entries.map(
+      (entry) =>
+        el(
+          "entry",
+          [],
+          el("id", [], text(entry.id)),
+          el("link", [["rel", "alternate"], ["href", entry.linkToAlternate]]),
+          el("title", [], text(entry.title)),
+          el("summary", [], text(entry.summary)),
+          el("published", [], text(entry.published)),
+          el("updated", [], text(entry.updated)),
+        ),
+    ),
+  );
+}
diff --git a/vhosts/blog/nuldoc-src/atom/types.ts b/vhosts/blog/nuldoc-src/atom/types.ts
new file mode 100644
index 00000000..66fde5ba
--- /dev/null
+++ b/vhosts/blog/nuldoc-src/atom/types.ts
@@ -0,0 +1,19 @@
+export type Feed = {
+  author: string;
+  icon: string;
+  id: string;
+  linkToSelf: string;
+  linkToAlternate: string;
+  title: string;
+  updated: string;
+  entries: Entry[];
+};
+
+export type Entry = {
+  id: string;
+  linkToAlternate: string;
+  published: string;
+  summary: string;
+  title: string;
+  updated: string;
+};