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 { getPost, 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 = (): Feed => {
  const frontmatter = getFrontMatter();

  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/${siteConfig.license}.html`,
    updated: frontmatter[0] ? new Date(frontmatter[0].date) : undefined,
    image: `${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 posts: FeedItem[] = frontmatter.map((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: `
        ${getPost(post.slug)?.feedHtml}
        <p><a href="${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;
};