const express = require('express');
const cors = require('cors');
const helmet = require('helmet');
const fs = require('fs');
const path = require('path');
const { isInstalled, getConfig } = require('./db');
const {
  sanitizeBody, generalLimiter, loginLimiter, registerLimiter,
  ticketLimiter, captchaLimiter, apiKeyGuard, methodGuard
} = require('./middleware/security');

const app = express();
app.set('trust proxy', 1);
const PORT = process.env.PORT || 3100;
const PUBLIC_DIR = path.join(__dirname, '..', 'public');
const HTML_PATH = path.join(PUBLIC_DIR, 'index.html');

let cachedHtml = null;
let htmlTimestamp = 0;
let htmlKey = null;

function getSiteName() {
  if (!isInstalled()) return 'MC举报系统';
  try {
    const { getPool } = require('./db');
    return getPool().then(p => p.execute("SELECT v FROM settings WHERE k='site_name'")).then(([rows]) => rows.length > 0 ? rows[0].v : 'MC举报系统').catch(() => 'MC举报系统');
  } catch { return 'MC举报系统'; }
}

function getHtmlWithKey() {
  return Promise.resolve(getSiteName()).then(siteName => {
    const stat = fs.statSync(HTML_PATH);
    const mtime = stat.mtimeMs;
    const cfg = getConfig();
    const key = cfg?.api_key || '';
    if (!cachedHtml || htmlTimestamp < mtime || htmlKey !== key || cachedHtml.indexOf(siteName) === -1) {
      let html = fs.readFileSync(HTML_PATH, 'utf-8');
      const redirect = isInstalled() ? '' : '<script>location.hash="#/install"</script>';
      html = html.replace('</head>', `<script>window.__API_KEY__=${JSON.stringify(key)};window.__SITE_NAME__=${JSON.stringify(siteName)}</script>${redirect}</head>`);
      cachedHtml = html;
      htmlTimestamp = mtime;
      htmlKey = key;
    }
    return cachedHtml;
  });
}

app.use(helmet({
  contentSecurityPolicy: {
    directives: {
      defaultSrc: ["'self'"],
      scriptSrc: ["'self'", "'unsafe-inline'", "https://cdnjs.cloudflare.com"],
      styleSrc: ["'self'", "'unsafe-inline'", "https://cdnjs.cloudflare.com"],
      fontSrc: ["'self'", "https://cdnjs.cloudflare.com"],
      imgSrc: ["'self'", "data:", "blob:"],
      mediaSrc: ["'self'"],
      connectSrc: ["'self'"],
      scriptSrcAttr: ["'unsafe-inline'"],
    },
  },
  crossOriginEmbedderPolicy: false,
  crossOriginResourcePolicy: { policy: 'cross-origin' },
}));

app.use(cors({
  origin: (origin, cb) => {
    const allowed = process.env.CORS_ORIGIN;
    if (!allowed || allowed === '*') return cb(null, true);
    if (allowed === origin) return cb(null, true);
    const host = origin || '';
    if (host.startsWith('http://localhost:') || host.startsWith('https://localhost:')) return cb(null, true);
    cb(null, false);
  },
  credentials: true,
  methods: ['GET','POST','PUT','DELETE'],
  allowedHeaders: ['Content-Type','Authorization','x-api-key'],
}));
app.disable('x-powered-by');
app.use(express.json({ limit: '1mb' }));
app.use(express.urlencoded({ extended: true, limit: '1mb' }));
app.use(sanitizeBody);
app.use(generalLimiter);
app.use('/api', apiKeyGuard);
app.use('/api', (req, res, next) => {
  res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate, private');
  res.setHeader('Pragma', 'no-cache');
  res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin');
  next();
});

const staticOpts = {
  maxAge: 0,
  setHeaders: (res, p) => {
    res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
  },
};
app.use('/css', express.static(path.join(PUBLIC_DIR, 'css'), staticOpts));
app.use('/js', express.static(path.join(PUBLIC_DIR, 'js'), staticOpts));

const installRoutes = require('./routes/install');
app.use('/api/install', installRoutes);

// 业务路由挂在独立 Router 上: 动态添加的路由在 Router 内部按序匹配,
// 不会被注册在 Router 之后的 404 兜底抢先(修复安装后"接口不存在")
const businessRouter = express.Router();
app.use('/api', businessRouter);

let businessLoaded = false;
function loadBusinessRoutes() {
  if (businessLoaded) return;
  businessLoaded = true;

  const authRoutes = require('./routes/auth');
  businessRouter.use('/auth/login', methodGuard(['POST']), loginLimiter);
  businessRouter.use('/auth/register', methodGuard(['POST']), registerLimiter);
  businessRouter.use('/auth', authRoutes);

  businessRouter.use('/captcha', methodGuard(['GET']), captchaLimiter, require('./routes/captcha'));

  businessRouter.use('/tickets', methodGuard(['GET','POST','PUT']), ticketLimiter, require('./routes/tickets'));
  businessRouter.use('/reports', methodGuard(['GET','POST','PUT']), ticketLimiter, require('./routes/tickets'));

  businessRouter.use('/users', methodGuard(['GET','POST','PUT']), generalLimiter, require('./routes/users'));
  businessRouter.use('/settings', methodGuard(['GET','PUT']), generalLimiter, require('./routes/settings'));
  businessRouter.use('/export', methodGuard(['GET']), generalLimiter, require('./routes/export'));
  businessRouter.use('/uploads', methodGuard(['GET']), generalLimiter, require('./routes/uploads'));
  businessRouter.use('/notifications', methodGuard(['GET','POST','PUT','DELETE']), generalLimiter, require('./routes/notifications'));
  businessRouter.use('/polls', methodGuard(['GET','POST','PUT','DELETE']), generalLimiter, require('./routes/polls'));
  businessRouter.use('/features', methodGuard(['GET','POST','PUT','DELETE']), generalLimiter, require('./routes/features'));
  businessRouter.use('/bans', methodGuard(['GET','POST','PUT','DELETE']), generalLimiter, require('./routes/bans'));
  businessRouter.use('/external', require('./routes/external'));

  businessRouter.get('/verify', (req, res) => res.redirect(`/#/verify?token=${req.query.token}`));
}

if (isInstalled()) loadBusinessRoutes();
global.__loadBusinessRoutes = loadBusinessRoutes;

app.get('/api/health', (req, res) => res.json({ status: 'ok', installed: isInstalled() }));

app.get('/', async (req, res) => {
  res.setHeader('Cache-Control', 'no-cache');
  res.type('html').send(await getHtmlWithKey());
});

app.get('*', async (req, res) => {
  if (req.path.startsWith('/api')) return res.status(404).json({ error: '接口不存在' });
  res.setHeader('Cache-Control', 'no-cache');
  res.type('html').send(await getHtmlWithKey());
});

app.use((err, req, res, next) => {
  if (err.message === 'SYSTEM_NOT_INSTALLED') return res.status(503).json({ error: '系统未安装' });
  if (err.code === 'LIMIT_FILE_SIZE') return res.status(400).json({ error: '文件大小超过限制(50MB)' });
  if (err.message?.includes('不支持的文件类型')) return res.status(400).json({ error: err.message });
  if (err.message?.includes('文件内容与声明类型不符')) return res.status(400).json({ error: '文件类型校验失败' });
  console.error(err);
  res.status(500).json({ error: '服务器内部错误' });
});

app.listen(PORT, () => {
  if (isInstalled()) console.log(`Server running at http://localhost:${PORT}`);
  else console.log(`System not installed. Visit http://localhost:${PORT}/#/install`);
}).on('error', (err) => { console.error('Failed to start:', err.message); process.exit(1); });