// Minimal static SPA server for the OpenPencil Vue editor (dist/).
//
// Serves the built SPA from OPENPENCIL_WEB_ROOT (default ./dist) on
// OPENPENCIL_WEB_PORT (default 3100). Implements the SPA fallback that
// Cloudflare Pages provides via dist/_redirects (`/* /index.html 200`), plus
// correct MIME types — notably application/wasm for CanvasKit.
//
// Runs under bun in the container: `bun static-server.mjs`.

import { createServer } from 'node:http'
import { readFile, stat } from 'node:fs/promises'
import { extname, join, normalize } from 'node:path'

const ROOT = process.env.OPENPENCIL_WEB_ROOT ?? join(import.meta.dir, 'dist')
const PORT = Number(process.env.OPENPENCIL_WEB_PORT ?? 3100)
const HOST = process.env.OPENPENCIL_WEB_HOST ?? '0.0.0.0'

// W4C fork delta: same-origin proxy for CORS-hostile online-font endpoints
// (https://fonts.google.com/metadata/fonts and https://fonts.googleapis.com/css2).
// The browser app (which is a W4C fork) rewrites those requests to
// /__font-proxy?url=... so they stay same-origin; we forward them upstream here.
// Mirrors vite/font-proxy.ts.
const FONT_PROXY_PREFIX = '/__font-proxy'
const PROXIED_FONT_HOSTS = ['fonts.google.com', 'fonts.googleapis.com']
const FONT_PROXY_USER_AGENT =
  'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126 Safari/537.36'

async function handleFontProxy(req, res, hostHeader) {
  const url = new URL(req.url ?? '/', `http://${hostHeader}`)
  const target = url.searchParams.get('url')
  // The browser forwards the original `user-agent` here because it cannot send
  // one cross-origin; unifont uses it to pick the glyph format (ttf/otf/woff2).
  const ua = url.searchParams.get('ua')
  if (!target) {
    res.writeHead(400)
    res.end('missing url')
    return
  }
  let targetUrl
  try {
    targetUrl = new URL(decodeURIComponent(target))
  } catch {
    res.writeHead(400)
    res.end('invalid url')
    return
  }
  if (targetUrl.protocol !== 'https:' || !PROXIED_FONT_HOSTS.includes(targetUrl.host)) {
    res.writeHead(403)
    res.end('proxied host denied')
    return
  }
  try {
    const upstream = await fetch(targetUrl, {
      headers: {
        'user-agent': ua ?? FONT_PROXY_USER_AGENT,
        accept: 'application/json, text/plain, */*'
      },
      redirect: 'follow'
    })
    const body = Buffer.from(await upstream.arrayBuffer())
    const type = upstream.headers.get('content-type')
    res.writeHead(upstream.status, {
      'content-type': type ?? 'application/octet-stream',
      'cache-control': upstream.status === 200 ? 'public, max-age=86400' : 'no-store',
      'access-control-allow-origin': '*'
    })
    res.end(body)
  } catch (err) {
    res.writeHead(502)
    res.end(String(err))
  }
}

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',
  '.wasm': 'application/wasm',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.svg': 'image/svg+xml',
  '.webp': 'image/webp',
  '.ico': 'image/x-icon',
  '.ttf': 'font/ttf',
  '.otf': 'font/otf',
  '.woff': 'font/woff',
  '.woff2': 'font/woff2',
  '.txt': 'text/plain; charset=utf-8',
  '.webmanifest': 'application/manifest+json'
}

const server = createServer(async (req, res) => {
  try {
    let pathname
    try {
      pathname = decodeURIComponent(new URL(req.url ?? '/', `http://${req.headers.host}`).pathname)
    } catch {
      pathname = '/'
    }
    if (pathname === FONT_PROXY_PREFIX) {
      await handleFontProxy(req, res, req.headers.host)
      return
    }
    if (pathname === '/') pathname = '/index.html'

    // Prevent path traversal outside ROOT.
    const filePath = normalize(join(ROOT, pathname))
    if (!filePath.startsWith(ROOT)) {
      res.writeHead(403)
      res.end('Forbidden')
      return
    }

    let fullPath = filePath
    try {
      const s = await stat(fullPath)
      if (s.isDirectory()) fullPath = join(fullPath, 'index.html')
    } catch {
      // 404 → SPA fallback to index.html (vite preview behaviour).
      fullPath = join(ROOT, 'index.html')
    }

    const body = await readFile(fullPath)
    res.writeHead(200, {
      'content-type': MIME[extname(fullPath)] ?? 'application/octet-stream',
      'cache-control': extname(fullPath) === '.html' ? 'no-cache' : 'public, max-age=31536000, immutable'
    })
    res.end(body)
  } catch (err) {
    res.writeHead(500)
    res.end(`Internal Server Error: ${String(err)}`)
  }
})

server.listen(PORT, HOST, () => {
  process.stderr.write(`Static server: http://${HOST}:${PORT} (root ${ROOT})\n`)
})