/**
 * The RSS 2.0 feed: blog posts and case studies, newest first, with absolute
 * links from the configured site address or the request's origin.
 */
import type { APIRoute } from "astro";
import { xml } from "../lib/blog.ts";
import { site } from "../lib/page.ts";

export const GET: APIRoute = async ({ site: configured, url }) => {
  const s = await site();
  const origin = (configured ?? new URL(url.origin)).href.replace(/\/$/, "");
  const abs = (path: string) => new URL(path, `${origin}/`).href;
  const settings = s.settings();
  const name = settings?.name ?? "Greg Kilmer";
  const posts = s.posts({ includeCaseStudies: true }).slice(0, 50);
  const rfc822 = (iso: string) => new Date(`${iso}T12:00:00Z`).toUTCString();

  const items = posts
    .map((p) => {
      const href = s.href(p);
      if (!href) return "";
      const link = abs(href);
      const category = p.data.postType === "case study" ? "Case study" : p.data.topic;
      return [
        "    <item>",
        `      <title>${xml(p.title)}</title>`,
        `      <link>${xml(link)}</link>`,
        `      <guid isPermaLink="true">${xml(link)}</guid>`,
        `      <pubDate>${rfc822(p.data.date)}</pubDate>`,
        `      <category>${xml(category)}</category>`,
        p.data.summary ? `      <description>${xml(p.data.summary)}</description>` : "",
        "    </item>",
      ]
        .filter(Boolean)
        .join("\n");
    })
    .filter(Boolean)
    .join("\n");

  const body = `<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <title>${xml(name)}</title>
    <link>${xml(abs("/blog"))}</link>
    <atom:link href="${xml(abs("/rss.xml"))}" rel="self" type="application/rss+xml" />
    <description>${xml(settings?.tagline ?? "What I am making, learning, playing and building.")}</description>
    <language>en-us</language>
${posts[0] ? `    <lastBuildDate>${rfc822(posts[0].data.date)}</lastBuildDate>\n` : ""}${items}
  </channel>
</rss>
`;
  return new Response(body, { headers: { "content-type": "application/rss+xml; charset=utf-8", "cache-control": "public, max-age=600" } });
};