import { promises as fs, readFileSync } from 'node:fs'
import path from 'node:path'
import { fileURLToPath } from 'url'

import { render } from './dist/ssr/entry-server.js'

const dirname = path.dirname(fileURLToPath(import.meta.url))

const cache = {}

const htmlBodyStart = '<!--app-html:start-->'
const htmlBodyEnd = '<!--app-html:end-->'
const headTagsStart = '<!--app-helmet-tags:start-->'
const headTagsEnd = '<!--app-helmet-tags:end-->'

const regexHTML = new RegExp(htmlBodyStart + '[\\s\\S]+' + htmlBodyEnd, 'm')
const regexHelmet = new RegExp(headTagsStart + '[\\s\\S]+' + headTagsEnd, 'm')

export default async ({ site, url, lang }) => {
	// TODO: Add CI test to enforce meta tags on SSR pages
	const { html, styleTags, helmet } = render(url, lang)

	const template =
		cache[site] ??
		readFileSync(path.join(dirname, `./dist/${site}.html`), 'utf-8')

	cache[site] = template

	const page = template
		.replace(regexHTML, html)
		.replace('<!--app-style-->', styleTags)
		.replace(regexHelmet, helmet.title.toString() + helmet.meta.toString())

	const dir = path.join(dirname, 'dist/prerender', site, decodeURI(url))

	await fs.mkdir(dir, { recursive: true })
	await fs.writeFile(path.join(dir, 'index.html'), page)

	return path.relative(path.join(dirname, 'dist'), path.join(dir, 'index.html'))
}