import { Feed, type Item as FeedItem } from "feed";

import ogImage from "@/app/opengraph-image.jpg";
import authorConfig from "@/lib/config/author";
import siteConfig from "@/lib/config/site";
import { getContent, getFrontMatter } from "@/lib/posts";

/**
 * Returns a `Feed` object, which can then be processed with `feed.rss2()`, `feed.atom1()`, or `feed.json1()`.
 * @see https://github.com/jpmonette/feed#example
 */
export const buildFeed = async (): Promise<Feed> => {
  const feed = new Feed({
    id: `${process.env.NEXT_PUBLIC_BASE_URL}`,
    link: `${process.env.NEXT_PUBLIC_BASE_URL}`,
    title: siteConfig.name,
    description: siteConfig.description,
    copyright: `https://spdx.org/licenses/${siteConfig.license}.html`,
    updated: new Date(),
    image: `${process.env.NEXT_PUBLIC_BASE_URL}${ogImage.src}`,
    feedLinks: {
      rss: `${process.env.NEXT_PUBLIC_BASE_URL}/feed.xml`,
      atom: `${process.env.NEXT_PUBLIC_BASE_URL}/feed.atom`,
    },
    author: {
      name: authorConfig.name,
      link: process.env.NEXT_PUBLIC_BASE_URL,
      email: authorConfig.email,
    },
  });

  // parse posts into feed items
  const frontmatter = await getFrontMatter();
  const posts: FeedItem[] = await Promise.all(
    frontmatter.map(async (post) => ({
      guid: post.permalink,
      link: post.permalink,
      title: post.title,
      description: post.description,
      author: [
        {
          name: authorConfig.name,
          link: `${process.env.NEXT_PUBLIC_BASE_URL}`,
        },
      ],
      date: new Date(post.date),
      content: `
        ${await getContent(post.slug)}
        <p><a href="${post.permalink}"><strong>Continue reading...</strong></a></p>
      `.trim(),
    })),
  );

  // sort posts reverse chronologically in case the promises resolved out of order
  posts.sort((post1, post2) => new Date(post2.date).getTime() - new Date(post1.date).getTime());

  // officially add each post to the feed
  posts.forEach((post) => {
    feed.addItem(post);
  });

  return feed;
};