import fs from 'node:fs/promises'
import express from 'express'
import cookieParser from 'cookie-parser'
import { compress } from 'compress-json'

const isProd = process.env.NODE_ENV !== 'development'
const port = process.env.PORT || 5174
const base = process.env.BASE || '/'

const MESSAGE = {
	404: 'Not Found',
	0: 'Unknown'
}

const templateHtml = isProd
	? await fs.readFile('./dist/client/index.html', 'utf-8')
	: ''

const app = express()
app.set('trust proxy', true)
app.use(cookieParser())

let vite
if (!isProd) {
	const { createServer } = await import('vite')
	vite = await createServer({
		server: { middlewareMode: true },
		appType: 'custom',
		base,
	})
	app.use(vite.middlewares)
} else {
	const sirv = (await import('sirv')).default
	app.use(base, sirv('./dist/client', { extensions: [] }))
}

function generateHead({ title, metas }) {
	const heads = [`<title>${title}</title>`]
	for (const meta of metas) {
		const attrs = Object.entries(meta).map(([k, v]) => `${k}="${v}"`).join(' ')
		heads.push(`<meta ${attrs}>`)
	}
	return heads.join('')
}

function injectHTML(template, { head, state }) {
	return template
		.replace('<!--app-head-->', head)
		.replace('<!--app-state-->', `<script>window.__PINIA_STATE__=${state}</script>`)
}

app.use('*all', async (req, res) => {
	try {
		const url = req.originalUrl.replace(base, '')
		console.log(`${req.ip} /${url} "${req.get('User-Agent')}"`)

		let template, render, getRoute
		if (!isProd) {
			template = await fs.readFile('./index.html', 'utf-8')
			template = await vite.transformIndexHtml(url, template)
			const mod = await vite.ssrLoadModule('/src/entry-server.js')
			render = mod.render
			getRoute = mod.getRoute
		} else {
			template = templateHtml
			const mod = await import('./dist/server/entry-server.js')
			render = mod.render
			getRoute = mod.getRoute
		}

		const { router, code, title, metas, meta } = await getRoute(url)

		if (code !== 200 && !req.accepts('html')) {
			res.status(code).type('text').send(MESSAGE[code] || MESSAGE[0])
			return
		}

		const { stream, piniaState, headState } = await render(router, req.cookies, req.headers.host)
		const [htmlStart, htmlEnd] = template.split('<!--app-html-->')

		if (meta) {
			const buffer = []
			let headSent = false

			for await (const chunk of stream) {
				if (res.closed) break

				if (headSent) {
					res.write(chunk)
				} else {
					if (headState.ready) {
						const head = generateHead({
							title: headState.title || title,
							metas: [...metas, ...headState.meta],
						})
						res.status(headState.code || code).type('html')
						res.write(htmlStart.replace('<!--app-head-->', head))
						buffer.forEach(c => res.write(c))
						res.write(chunk)
						headSent = true
					} else {
						buffer.push(chunk)
					}
				}
			}

			if (!headState.ready) {
				console.warn('[WARN] meta not ready, falling back to default meta')
				const head = generateHead({ title, metas })
				res.status(code).type('html')
				res.write(htmlStart.replace('<!--app-head-->', head))
				for await (const chunk of buffer) {
					if (res.closed) break
					res.write(chunk)
				}
			}
		} else {
			const head = generateHead({ title, metas })
			res.status(code).type('html')
			res.write(htmlStart.replace('<!--app-head-->', head))
			for await (const chunk of stream) {
				if (res.closed) break
				res.write(chunk)
			}
		}

		const stateScript = JSON.stringify(compress(piniaState))
		res.write(htmlEnd.replace('<!--app-state-->', `<script>window.__PINIA_STATE__=${stateScript}</script>`))
		res.end()

	} catch (err) {
		vite?.ssrFixStacktrace(err)
		console.error('[ERROR]', err.stack || err)
		res.status(500).end(err.stack)
	}
})

app.listen(port, () => {
	console.log(`🚀 Server running at http://localhost:${port} in mode ${isProd ? 'production' : 'development'}`)
})