#!/usr/bin/env node
/**
 * 文档站本地预览服务
 *
 * 站点是按 /ny-exam-platform 子路径构建的（base: '/ny-exam-platform/'），
 * 直接把 dist 目录当根来跑静态服务会导致所有资源 404。
 * 这里做一层前缀重写：把 /ny-exam-platform/<path> 映射到 dist 目录下的 <path>，
 * 根路径 / 自动跳转到 /ny-exam-platform/。
 *
 * 用法：
 *   node tools/docs-preview.js [端口] [dist目录]
 *   node tools/docs-preview.js 5199 docs/.vitepress/dist-final
 */
'use strict';

const http = require('http');
const fs = require('fs');
const path = require('path');

const PORT = parseInt(process.argv[2], 10) || 5199;
const DIST = path.resolve(process.argv[3] || path.join(__dirname, '..', 'docs', '.vitepress', 'dist-final'));
const BASE = (process.env.DOCS_BASE || '/ny-exam-platform').replace(/\/+$/, '');

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',
  '.gif': 'image/gif',
  '.webp': 'image/webp',
  '.ico': 'image/x-icon',
  '.woff': 'font/woff',
  '.woff2': 'font/woff2',
  '.ttf': 'font/ttf',
  '.txt': 'text/plain; charset=utf-8',
  '.map': 'application/json; charset=utf-8',
};

if (!fs.existsSync(DIST)) {
  console.error('[docs-preview] 找不到构建产物：' + DIST);
  console.error('请先构建：DOCS_OUT=.vitepress/dist-final npx vitepress build .');
  process.exit(1);
}

/** 把 URL 中的前缀剥掉，得到 dist 内的相对路径 */
function toRel(urlPath) {
  let p = decodeURIComponent(urlPath.split('?')[0].split('#')[0]);
  if (p === BASE || p === BASE + '/') return '/index.html';
  if (p.startsWith(BASE + '/')) p = p.slice(BASE.length);
  return p;
}

/** 依次尝试：原样 / .html / 目录下 index.html，模拟静态托管的行为 */
function resolveFile(rel) {
  const clean = path.normalize(rel).replace(/^([/\\])+/, '');
  const full = path.join(DIST, clean);
  if (full.indexOf(DIST) !== 0) return null;        // 防目录穿越
  const candidates = [full, full + '.html', path.join(full, 'index.html')];
  for (const c of candidates) {
    try {
      if (fs.existsSync(c) && fs.statSync(c).isFile()) return c;
    } catch (e) { /* 忽略 */ }
  }
  return null;
}

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

  // 根路径 / 直接跳到子路径首页
  if (urlPath === '/' || urlPath === '') {
    res.writeHead(302, { Location: BASE + '/' });
    res.end();
    return;
  }

  const rel = toRel(urlPath);
  const file = resolveFile(rel);
  if (!file) {
    res.writeHead(404, { 'Content-Type': 'text/plain; charset=utf-8' });
    res.end('404 Not Found: ' + urlPath);
    return;
  }

  const ext = path.extname(file).toLowerCase();
  res.writeHead(200, {
    'Content-Type': MIME[ext] || 'application/octet-stream',
    'Cache-Control': 'no-cache',
  });
  fs.createReadStream(file).pipe(res);
});

server.listen(PORT, '127.0.0.1', () => {
  console.log('[docs-preview] 文档站已启动');
  console.log('  访问地址：http://127.0.0.1:' + PORT + BASE + '/');
  console.log('  构建目录：' + DIST);
});
server.on('error', e => {
  console.error('[docs-preview] 启动失败：' + e.message);
  process.exit(1);
});