import { getCollection } from "astro:content";

function formatPubDate(date) {
  const timezone = process.env.PUBLIC_RSS_TIMEZONE
    ? process.env.PUBLIC_RSS_TIMEZONE
    : import.meta.env.PUBLIC_RSS_TIMEZONE;

  if (!timezone) {
    return date;
  }

  try {
    const year = date.getUTCFullYear();
    const month = String(date.getUTCMonth() + 1).padStart(2, "0");
    const day = String(date.getUTCDate()).padStart(2, "0");

    const formatter = new Intl.DateTimeFormat("en-US", {
      timeZone: timezone,
      timeZoneName: "longOffset",
    });

    const parts = formatter.formatToParts(date);
    const offsetPart = parts.find((p) => p.type === "timeZoneName");
    const offset = offsetPart ? offsetPart.value.replace("GMT", "") : "+00:00";

    const dateStr = `${year}-${month}-${day}T00:00:00${offset}`;

    return new Date(dateStr);
  } catch (e) {
    console.warn(`Invalid timezone "${timezone}":`, e.message);
    return date;
  }
}

export async function GET(context) {
  const posts = await getCollection("posts");

  // Sort posts by date, newest first
  posts.sort((a, b) => new Date(b.data.pubDate) - new Date(a.data.pubDate));

  const siteUrl = context.site?.toString().replace(/\/$/, "") || "";

  const items = posts
    .map((post) => {
      const title = post.data.title;
      const description = post.data.description || "";
      const link = `${siteUrl}/post/${post.id}/`;
      const pubDate = formatPubDate(post.data.pubDate).toUTCString();

      return `    <item>
      <title><![CDATA[${title}]]></title>
      <link>${link}</link>
      <guid isPermaLink="true">${link}</guid>
      <description><![CDATA[${description}]]></description>
      <pubDate>${pubDate}</pubDate>
    </item>`;
    })
    .join("\n");

  const rssXml = `<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <title>Atridad Lahiji</title>
    <description>Recent posts from Atridad Lahiji</description>
    <link>${siteUrl}/</link>
    <language>en-us</language>
    <atom:link href="${siteUrl}/rss.xml" rel="self" type="application/rss+xml" />
${items}
  </channel>
</rss>`;

  return new Response(rssXml, {
    headers: {
      "Content-Type": "application/xml",
    },
  });
}