+server.ts

import * as config from '$lib/config'
import type { PostsApiResponse } from '$api/posts/+server.js'
import type { RequestHandler } from './$types'

export const prerender = true

export const GET: RequestHandler = async ({ fetch }) => {
	const response = await fetch('api/posts')
	const posts = (await response.json()) as PostsApiResponse

	const headers = { 'Content-Type': 'application/xml' }

	const xml = `
		<rss xmlns:atom="http://www.w3.org/2005/Atom" version="2.0">
			<channel>
				<title>${config.title}</title>
				<description>${config.description}</description>
				<link>${config.url}</link>
				<atom:link href="${config.url}/rss.xml" rel="self" type="application/rss+xml"/>
				${posts
					.map(
						(post) => `
						<item>
							<title>${escapeXml(post.title ?? 'Untitled')}</title>
							<description>${post.description ? escapeXml(post.description) : ''}</description>
							<link>${config.url}/${post.slug}</link>
							<guid isPermaLink="true">${config.url}/${post.slug}</guid>
							${post.date ? `<pubDate>${new Date(post.date).toUTCString()}</pubDate>` : ''}
						</item>
					`
					)
					.join('')}
			</channel>
		</rss>
	`.trim()

	return new Response(xml, { headers })
}

function escapeXml(unsafe: string) {
	return unsafe.replace(/[<>&'"]/g, (c) => {
		switch (c) {
			case '<':
				return '&lt;'
			case '>':
				return '&gt;'
			case '&':
				return '&amp;'
			case "'":
				return '&apos;'
			case '"':
				return '&quot;'
			default:
				return c
		}
	})
}