serve.js

#!/usr/bin/env node
/*
 * 离线数学工具箱 · 局域网静态服务器（零依赖，只需 Node.js）
 *
 *   node serve.js            # 默认 8080 端口
 *   node serve.js 9000       # 指定端口
 *
 * 启动后：本机访问 http://localhost:8080/
 *         同局域网的学生/其他电脑访问 http://<本机IP>:8080/
 */
'use strict';

const http = require('http');
const fs = require('fs');
const path = require('path');
const os = require('os');
const { exec } = require('child_process');
const { URL } = require('url');

const ROOT = __dirname;

/* ---------------- 命令行参数 ----------------
 *   node serve.js              自动选端口(8080 起)，并自动打开浏览器
 *   node serve.js 9000         指定端口
 *   node serve.js --no-open    不自动打开浏览器（测试用）
 */
const argv = process.argv.slice(2);
const NO_OPEN = argv.includes('--no-open');
const portArg = argv.find((a) => /^\d+$/.test(a)) || process.env.PORT || null;
const START_PORT = portArg ? parseInt(portArg, 10) : 8080;
const MAX_TRIES = portArg ? 0 : 50; // 未指定端口时，被占用就往后找

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.htm': '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',
  '.map': 'application/json; charset=utf-8',
  '.txt': 'text/plain; charset=utf-8',
  '.md': 'text/plain; charset=utf-8',
  '.xml': 'application/xml; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.gif': 'image/gif',
  '.webp': 'image/webp',
  '.ico': 'image/x-icon',
  '.bmp': 'image/bmp',
  '.woff': 'font/woff',
  '.woff2': 'font/woff2',
  '.ttf': 'font/ttf',
  '.otf': 'font/otf',
  '.eot': 'application/vnd.ms-fontobject',
  '.pdf': 'application/pdf',
  '.wasm': 'application/wasm',
  '.zip': 'application/zip',
  '.ggb': 'application/octet-stream',
  '.ggt': 'application/octet-stream',
  '.mp3': 'audio/mpeg',
  '.mp4': 'video/mp4',
};

function log(...a) {
  console.log('[server]', ...a);
}

function localIPs() {
  const out = [];
  const ifaces = os.networkInterfaces();
  for (const name of Object.keys(ifaces)) {
    for (const info of ifaces[name] || []) {
      if (info.family === 'IPv4' && !info.internal) out.push({ name, address: info.address });
    }
  }
  return out;
}

const server = http.createServer((req, res) => {
  let pathname;
  try {
    pathname = decodeURIComponent(new URL(req.url, 'http://localhost').pathname);
  } catch {
    res.writeHead(400, { 'Content-Type': 'text/plain; charset=utf-8' });
    return res.end('400 Bad Request');
  }

  // 目录穿越防护
  const safe = path.normalize(path.join(ROOT, pathname));
  if (!safe.startsWith(ROOT)) {
    res.writeHead(403, { 'Content-Type': 'text/plain; charset=utf-8' });
    return res.end('403 Forbidden');
  }

  fs.stat(safe, (err, st) => {
    if (err) return notFound(res, pathname);
    if (st.isDirectory()) {
      const idx = path.join(safe, 'index.html');
      if (fs.existsSync(idx)) return sendFile(req, res, idx, 'text/html; charset=utf-8');
      return sendDirListing(res, safe, pathname);
    }
    sendFile(req, res, safe, MIME[path.extname(safe).toLowerCase()] || 'application/octet-stream');
  });
});

function notFound(res, pathname) {
  log('404', pathname);
  res.writeHead(404, { 'Content-Type': 'text/html; charset=utf-8' });
  res.end(
    '<meta charset="utf-8"><h2>404 找不到文件</h2>' +
      '<p>' + escapeHtml(pathname) + '</p><p><a href="/">← 返回首页</a></p>'
  );
}

function escapeHtml(s) {
  return String(s).replace(/[&<>"]/g, (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;' }[c]));
}

function sendDirListing(res, dir, pathname) {
  const items = fs.readdirSync(dir, { withFileTypes: true });
  const rows = items
    .map((d) => {
      const href = encodeURI(pathname.replace(/\/?$/, '/') + d.name) + (d.isDirectory() ? '/' : '');
      return `<li><a href="${href}">${escapeHtml(d.name)}${d.isDirectory() ? '/' : ''}</a></li>`;
    })
    .join('');
  res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' });
  res.end(`<meta charset="utf-8"><h2>目录 ${escapeHtml(pathname)}</h2><ul>${rows}</ul>`);
}

function sendFile(req, res, file, type) {
  fs.stat(file, (err, st) => {
    if (err || !st.isFile()) return notFound(res, file);
    const headers = {
      'Content-Type': type,
      /* 页面/脚本/样式不缓存：老师更新 U 盘里的文件后立刻生效，
         大体积的离线包（GeoGebra / Desmos）才允许缓存一小时 */
      'Cache-Control': /\.(html|js|css|json|txt)$/i.test(file)
        ? 'no-cache'
        : 'public, max-age=3600',
      'Last-Modified': st.mtime.toUTCString(),
      'Accept-Ranges': 'bytes',
    };

    // 简单的 Range 支持
    const range = req.headers.range;
    if (range) {
      const m = /^bytes=(\d*)-(\d*)$/.exec(range);
      if (m) {
        let start = m[1] === '' ? st.size - parseInt(m[2], 10) : parseInt(m[1], 10);
        let end = m[1] === '' || m[2] === '' ? st.size - 1 : parseInt(m[2], 10);
        if (isNaN(start) || isNaN(end) || start < 0 || end >= st.size || start > end) {
          res.writeHead(416, { 'Content-Range': `bytes */${st.size}` });
          return res.end();
        }
        headers['Content-Range'] = `bytes ${start}-${end}/${st.size}`;
        headers['Content-Length'] = end - start + 1;
        res.writeHead(206, headers);
        return fs.createReadStream(file, { start, end }).pipe(res);
      }
    }

    headers['Content-Length'] = st.size;
    res.writeHead(200, headers);
    fs.createReadStream(file).pipe(res);
  });
}

/* ---------------- 自动打开浏览器 ---------------- */
function openBrowser(url) {
  if (NO_OPEN) {
    log('已跳过自动打开浏览器（--no-open）：', url);
    return;
  }
  if (process.platform === 'win32') {
    exec(`start "" "${url}"`, { shell: 'cmd.exe' }, () => {});
  } else if (process.platform === 'darwin') {
    exec(`open "${url}"`, () => {});
  } else {
    exec(`xdg-open "${url}"`, () => {});
  }
}

/* ---------------- 启动，端口被占用自动顺延 ---------------- */
let tries = 0;
function listen(port) {
  server.listen(port, '0.0.0.0');
}

server.on('error', (e) => {
  if (e.code === 'EADDRINUSE' && tries < MAX_TRIES) {
    tries += 1;
    listen(START_PORT + tries);
    return;
  }
  if (e.code === 'EADDRINUSE') {
    console.error(`\n端口 ${START_PORT} 已被占用，请换一个端口：  node serve.js 9000\n`);
  } else {
    console.error(e);
  }
  process.exit(1);
});

server.on('listening', () => {
  const PORT = server.address().port;
  const ips = localIPs();
  console.log('');
  console.log('');
  console.log('  ==================================================');
  console.log('        离线数学工具箱  服务已启动');
  console.log('  ==================================================');
  console.log('');
  console.log('');
  console.log(`   本机访问 :  http://localhost:${PORT}/`);
  if (ips.length) {
    console.log('   局域网访问（学生机 / 一体机输入下面地址）：');
    ips.forEach((i) => console.log(`               http://${i.address}:${PORT}/    (${i.name})`));
  } else {
    console.log('   未检测到局域网 IP（可能未联网 / 未连 Wi-Fi）');
  }
  console.log('');
  console.log(`   网站根目录 :  ${ROOT}`);
  console.log('   停止服务   :  直接关闭本窗口');
  console.log('');

  openBrowser(`http://127.0.0.1:${PORT}/`);
});

listen(START_PORT);