/*
 * A second sitemap for the URLs Next owns.
 *
 * /sitemap.xml is proxied from FastAPI (app/(frontend)/sitemap.xml), which
 * knows nothing about Payload — the backend and frontend ship as separate
 * images. Rather than teach it, the Next-owned URLs get their own sitemap and
 * robots.txt lists both.
 */
import { getCachedPayload } from '@/lib/payload';
import { absoluteUrl } from '@/lib/site';
import { getFlags } from '@/lib/flags';

/*
 * Dynamic, not ISR.
 *
 * This route has no dynamic params, so Next prerenders it at build time — and
 * CI builds the image with no database reachable, which fails the build. It is
 * a single indexed query against Postgres on the same Docker network, so
 * rendering per request is cheap, and it means a newly published post appears
 * here immediately rather than waiting on a revalidation.
 */
export const dynamic = 'force-dynamic';

export async function GET() {
  /*
   * A dark page must not be advertised. Submitting a URL that 404s is the one
   * thing a sitemap is not allowed to do, so each entry is gated on the same
   * flag that gates the page itself.
   *
   * With both flags dark this emits a valid, empty <urlset> rather than a 404:
   * robots.txt names this sitemap unconditionally, and an empty sitemap is a
   * well-formed statement that there is nothing here yet.
   */
  const flags = await getFlags();
  const aboutEnabled = flags.about_page === true;
  const blogEnabled = flags.blog === true;

  // Only query Payload when the blog is actually being advertised.
  const docs = blogEnabled
    ? (await (await getCachedPayload()).find({
      collection: 'posts',
      where: { _status: { equals: 'published' } },
      sort: '-publishedAt',
      limit: 500,
      depth: 0,
    })).docs
    : [];

  const urls: Array<{ loc: string; lastmod: string | null }> = [
    ...(aboutEnabled ? [{ loc: absoluteUrl('/about'), lastmod: null }] : []),
    ...(blogEnabled ? [{ loc: absoluteUrl('/blog'), lastmod: null }] : []),
    ...docs.map((post) => ({
      loc: absoluteUrl(`/blog/${post.slug}`),
      lastmod: new Date(String(post.updatedAt ?? post.publishedAt)).toISOString(),
    })),
  ];

  const xml = `<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
${urls.map(({ loc, lastmod }) =>
  `  <url><loc>${loc}</loc>${lastmod ? `<lastmod>${lastmod}</lastmod>` : ''}</url>`,
).join('\n')}
</urlset>`;

  return new Response(xml, {
    headers: { 'Content-Type': 'application/xml; charset=utf-8' },
  });
}