import { createReadStream } from 'node:fs'
import { readFile, stat } from 'node:fs/promises'
import { createServer } from 'node:http'
import { createCipheriv, createDecipheriv, createHash, randomBytes } from 'node:crypto'
import path from 'node:path'
import { fileURLToPath } from 'node:url'

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

const root = fileURLToPath (new URL ('./dist/client/', import.meta.url))
const template = await readFile (path.join (root, 'index.html'), 'utf8')
const origin = new URL (process.env.PUBLIC_ORIGIN ?? 'http://localhost:5173').origin
const apiBaseURL = process.env.SSR_API_BASE_URL ?? 'http://127.0.0.1:3002'
const sessionSecret = process.env.SSR_COOKIE_SECRET
if (process.env.NODE_ENV === 'production' && (!sessionSecret || sessionSecret.length < 32))
  throw new Error ('SSR_COOKIE_SECRET must contain at least 32 characters in production')
const sessionKey = createHash ('sha256').update (sessionSecret ?? randomBytes (32)).digest ()
const cookieName = '__Host-btrc-session'
const sessionSeconds = 7 * 24 * 60 * 60

const encodeSession = code => {
  const iv = randomBytes (12)
  const cipher = createCipheriv ('aes-256-gcm', sessionKey, iv)
  const payload = JSON.stringify ({ code, expires: Date.now () + sessionSeconds * 1000 })
  const encrypted = Buffer.concat ([cipher.update (payload, 'utf8'), cipher.final ()])
  return Buffer.concat ([iv, cipher.getAuthTag (), encrypted]).toString ('base64url')
}

const decodeSession = cookie => {
  try
  {
    const token = cookie?.split (';').map (part => part.trim ())
      .find (part => part.startsWith (`${cookieName}=`))?.slice (cookieName.length + 1)
    if (!token || token.length > 2048) return undefined
    const payload = Buffer.from (token, 'base64url')
    const decipher = createDecipheriv ('aes-256-gcm', sessionKey, payload.subarray (0, 12))
    decipher.setAuthTag (payload.subarray (12, 28))
    const data = JSON.parse (Buffer.concat ([
      decipher.update (payload.subarray (28)), decipher.final ()]).toString ('utf8'))
    return typeof data.code === 'string' && data.expires > Date.now () ? data.code : undefined
  }
  catch
  {
    return undefined
  }
}
const types = {
    '.js': 'text/javascript', '.css': 'text/css', '.json': 'application/json',
    '.png': 'image/png', '.gif': 'image/gif', '.jpg': 'image/jpeg',
    '.svg': 'image/svg+xml', '.ico': 'image/x-icon', '.webp': 'image/webp',
    '.woff': 'font/woff', '.woff2': 'font/woff2', '.otf': 'font/otf',
    '.mp4': 'video/mp4', '.mp3': 'audio/mpeg', '.txt': 'text/plain' }

if (process.env.NODE_ENV === 'production' && !process.env.PUBLIC_ORIGIN)
  throw new Error ('PUBLIC_ORIGIN is required in production')

const server = createServer (async (request, response) => {
  response.setHeader ('Cache-Control', 'private, no-store')
  const forwardedFor = request.headers['x-forwarded-for'] ?? request.socket.remoteAddress
  if (request.url === '/_ssr/session')
  {
    if (request.method !== 'POST' || request.headers.origin !== origin)
    {
      response.writeHead (403).end ()
      return
    }
    const code = request.headers['x-transfer-code']
    if (typeof code !== 'string' || code.length > 512 || code.length === 0)
    {
      response.writeHead (400).end ()
      return
    }
    try
    {
      const verified = await fetch (new URL ('users/session', apiBaseURL.replace (/\/?$/, '/')), {
        headers: { 'X-Transfer-Code': code, 'X-Forwarded-For': forwardedFor },
        signal: AbortSignal.timeout (10_000) })
      if (!verified.ok)
      {
        response.writeHead (verified.status === 401 || verified.status === 403
          ? verified.status : 503).end ()
        return
      }
      response.setHeader ('Set-Cookie', `${cookieName}=${encodeSession (code)}; `
        + `Path=/; HttpOnly; Secure; SameSite=Lax; Max-Age=${sessionSeconds}`)
      response.writeHead (204).end ()
    }
    catch
    {
      response.writeHead (503).end ()
    }
    return
  }
  if (!['GET', 'HEAD'].includes (request.method))
  {
    response.writeHead (405, { Allow: 'GET, HEAD' }).end ()
    return
  }
  try
  {
    const url = new URL (request.url, origin)
    const pathname = decodeURIComponent (url.pathname)
    const file = path.resolve (root, '.' + pathname)
    const allowed = file.startsWith (root)
        && !pathname.split ('/').some (segment => segment.startsWith ('.'))
        && pathname !== '/index.html'
    const info = allowed ? await stat (file).catch (() => null) : null
    if (info?.isFile ())
    {
      response.writeHead (200, {
	'Content-Type': types[path.extname (file)] ?? 'application/octet-stream',
	'Content-Length': info.size,
	'Cache-Control': /\/[^/]+-[\w-]{8}\.[^.]+$/.test (pathname)
	    ? 'public, max-age=31536000, immutable' : 'public, max-age=3600' })
      if (request.method === 'HEAD')
	response.end ()
      else
	createReadStream (file).on ('error', () => response.destroy ()).pipe (response)
      return
    }
    if (pathname.startsWith ('/assets/'))
    {
      response.writeHead (404).end ()
      return
    }
    const result = await render (url.pathname + url.search, origin, apiBaseURL, {
      transferCode: decodeSession (request.headers.cookie), forwardedFor })
    if (result?.location != null)
    {
      response.writeHead (result.status, { Location: result.location }).end ()
      return
    }
    const html = result?.html == null
        ? template.replace ('<!-- helmet -->', result?.status === 404
            ? '<meta name="robots" content="noindex" data-rh="true">' : '')
        : template
	.replace ('lang="ja"', `lang="${result.locale}"`)
	.replace (/<title>[\s\S]*?<\/title>/, '')
	.replace (/<meta name="description"[^>]*>/, '')
	.replace ('<!-- helmet -->', () => result.head)
	.replace ('<!-- outlet -->', () => result.html)
	.replace ('<!-- ssr-state -->',
	    () => `<script id="ssr-state" type="application/json">${result.bootstrap}</script>`)
    response.writeHead (result?.status ?? 200, {
	'Content-Type': 'text/html; charset=utf-8' })
    response.end (request.method === 'HEAD' ? undefined : html)
  }
  catch (error)
  {
    console.error ('[SSR]', error instanceof Error ? error.message : 'Rendering failed')
    const denied = error?.response?.status === 401 || error?.response?.status === 403
    response.writeHead (error instanceof URIError ? 400
      : (denied ? error.response.status : 503)).end ()
  }
})

server.listen (Number (process.env.PORT ?? 5173), process.env.HOST ?? '127.0.0.1', () => {
  console.info ('[SSR] listening on', server.address ().port)
})