// Production server for Shelfless.
// Serves the built SPA (dist/) and reverse-proxies ABS API paths to the Audiobookshelf
// server given by ABS_URL — so the browser talks to a single origin (no CORS) and the
// ABS address is fixed by the deployment, not entered per browser.
//
//   ABS_URL=http://127.0.0.1:13378 PORT=8080 node server/index.mjs
//
// Only Node built-ins are used (no dependencies to install on the container).

import http from 'node:http'
import https from 'node:https'
import { createReadStream, existsSync, statSync } from 'node:fs'
import { join, extname, normalize } from 'node:path'
import { fileURLToPath } from 'node:url'

const PORT = Number(process.env.PORT || 8080)
const HOST = process.env.HOST || '0.0.0.0'
const ABS_URL = process.env.ABS_URL || 'http://127.0.0.1:13378'

const ROOT = fileURLToPath(new URL('..', import.meta.url))
const DIST = join(ROOT, 'dist')

// Paths that must be forwarded to Audiobookshelf.
const PROXY_PREFIXES = ['/api', '/login', '/logout', '/public', '/status', '/hls', '/feed', '/socket.io']

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.mjs': 'text/javascript; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.webp': 'image/webp',
  '.ico': 'image/x-icon',
  '.woff2': 'font/woff2',
  '.woff': 'font/woff',
  '.webmanifest': 'application/manifest+json',
  '.txt': 'text/plain; charset=utf-8',
}

const target = new URL(ABS_URL)
const proxyLib = target.protocol === 'https:' ? https : http

function isProxied(url) {
  return PROXY_PREFIXES.some((p) => url === p || url.startsWith(p + '/') || url.startsWith(p + '?'))
}

function proxy(req, res) {
  const headers = { ...req.headers, host: target.host }
  delete headers.origin
  delete headers.referer

  const proxyReq = proxyLib.request(
    {
      protocol: target.protocol,
      hostname: target.hostname,
      port: target.port || (target.protocol === 'https:' ? 443 : 80),
      method: req.method,
      path: req.url,
      headers,
    },
    (proxyRes) => {
      res.writeHead(proxyRes.statusCode || 502, proxyRes.headers)
      proxyRes.pipe(res)
    },
  )
  proxyReq.on('error', (e) => {
    res.statusCode = 502
    res.end(`Upstream error: ${e.message}`)
  })
  req.pipe(proxyReq)
}

function sendFile(res, filePath, status = 200) {
  res.writeHead(status, {
    'Content-Type': MIME[extname(filePath)] || 'application/octet-stream',
    // Hashed asset files are immutable; index.html should not be cached.
    'Cache-Control': filePath.includes(`${join('dist', 'assets')}`)
      ? 'public, max-age=31536000, immutable'
      : 'no-cache',
  })
  createReadStream(filePath).pipe(res)
}

// Resolve a request path to an existing static file inside dist/, or null.
function resolveStaticFile(url) {
  const urlPath = decodeURIComponent((url || '/').split('?')[0])
  const safe = normalize(urlPath).replace(/^(\.\.[/\\])+/, '')
  const filePath = join(DIST, safe)
  if (!filePath.startsWith(DIST)) return null
  if (existsSync(filePath) && statSync(filePath).isFile()) return filePath
  return null
}

const INDEX_HTML = join(DIST, 'index.html')

const server = http.createServer((req, res) => {
  const url = req.url || '/'

  // 1) Known ABS paths → forward upstream.
  if (isProxied(url)) return proxy(req, res)

  // 2) An existing static asset of the SPA → serve it.
  const file = resolveStaticFile(url)
  if (file) return sendFile(res, file)

  // 3) A browser navigating to a client-side route → serve the SPA shell.
  const accept = String(req.headers.accept || '')
  if (req.method === 'GET' && accept.includes('text/html') && existsSync(INDEX_HTML)) {
    return sendFile(res, INDEX_HTML)
  }

  // 4) Anything else (any other API/data request) → forward to ABS, so the real
  //    server never needs to be exposed on its own domain.
  return proxy(req, res)
})

server.listen(PORT, HOST, () => {
  console.log(`Shelfless running on http://${HOST}:${PORT}  →  ABS ${ABS_URL}`)
})