Astro Container RSS rendering

rss.xml.ts

import rss, { type RSSFeedItem } from "@astrojs/rss";
import { getCollection } from "astro:content";
import type { APIContext } from "astro";
import { getContainerRenderer } from "@astrojs/mdx";
import { loadRenderers } from "astro:container";
import { experimental_AstroContainer as AstroContainer } from "astro/container";

import { transform, walk } from "ultrahtml";
import sanitize from "ultrahtml/transformers/sanitize";
import { getBaseURL } from "@/utils";

import RSSRenderer from "@/components/RSSRenderer.astro";

export async function fixLinks(html: string, baseUrl: string) {
  return await transform(html, [
    async (node) => {
      await walk(node, (node) => {
        if (node.name === "a" && node.attributes.href?.startsWith("/")) {
          node.attributes.href = baseUrl + node.attributes.href;
        }
        if (node.name === "img" && node.attributes.src?.startsWith("/")) {
          node.attributes.src = baseUrl + node.attributes.src;
        }
      });
      return node;
    },

    sanitize({ dropElements: ["script", "style"] })
  ]);
}

export async function GET(context: APIContext) {
  const baseUrl = getBaseURL(context);
  const blog = await getCollection("blog");
  const items: RSSFeedItem[] = [];
  const renderers = await loadRenderers([getContainerRenderer()]);
  const container = await AstroContainer.create({
    renderers
  });

  for (const post of blog) {
    let html = await container.renderToString(RSSRenderer, {
      params: { slug: post.slug }
    });
    html = await fixLinks(html, baseUrl);

    items.push({
      title: post.data.title,
      description: post.data.description,
      pubDate: post.data.date,
      link: baseUrl + `/blog/${post.slug}`,
      content: html
    });
  }

  return await rss({
    title: "notnite's blog",
    description: "My ramblings assembled into one tidy place",
    site: context.site!,
    items
  });
}

RSSRenderer.astro

---
import type { ValidContentEntrySlug } from "astro:content";
import { getEntry } from "astro:content";
const { slug } = Astro.params;

const entry = await getEntry("blog", slug as ValidContentEntrySlug<"blog">);
const { Content } = await entry.render();
---

<Content />

utils.ts

import type { APIContext } from "astro";

export function getBaseURL(context?: APIContext) {
  let baseUrl = import.meta.env.PROD
    ? import.meta.env.SITE
    : (context?.url?.origin ?? "http://localhost:4321");
  if (baseUrl.at(-1) === "/") baseUrl = baseUrl.slice(0, -1);
  return baseUrl;
}