// RainID OIDC 授权码 + PKCE 接入（挂 /api/auth/oidc）
// 流程：GET /login 发起 → RainID 登录/同意 → GET /callback 换 token 建影子账号
//       → 一次性 ticket → 前端 POST /exchange 换本地 JWT（避免长 token 进 URL）
//       → GET /logout 登出联动（end_session）
// 安全：state 一次性 + PKCE S256（SDK 自动验 id_token iss/aud/exp/签名）；ticket 30s 一次性。
const express = require('express');
const crypto = require('crypto');
const jwt = require('jsonwebtoken');
const openidClient = require('openid-client'); // v6 函数式 API
const { SECRET } = require('../middleware/auth');
const {
  getOidcSettings,
  getOidcConfig,
  siteBase,
  findOrCreateRainidUser,
} = require('../lib/rainid');

const router = express.Router();

// ---- OIDC 流程状态：内存 Map + 短 TTL（模式同 routes/captcha.js 的 captchaStore）----
const OIDC_STATE_TTL = 10 * 60 * 1000;   // state：发起登录 → 回调，10 分钟
const OIDC_TICKET_TTL = 30 * 1000;       // ticket：回调 → 前端换 JWT，30 秒
const oidcStates = new Map();            // state -> { verifier, createdAt }
const oidcTickets = new Map();           // ticket -> { jwt, username, role, email, email_verified, createdAt }

setInterval(() => {
  const now = Date.now();
  for (const [k, v] of oidcStates) if (now - v.createdAt > OIDC_STATE_TTL) oidcStates.delete(k);
  for (const [k, v] of oidcTickets) if (now - v.createdAt > OIDC_TICKET_TTL) oidcTickets.delete(k);
}, 60000);

const REDIRECT_PATH = '/api/auth/oidc/callback';
const LOGOUT_REDIRECT_PATH = '/login.html'; // RainID 登出回跳白名单需登记该地址

function frontLoginUrl(req, qs) {
  return siteBase(req) + '/login.html' + (qs || '');
}

// ① 发起登录：PKCE + state → 302 RainID authorize
router.get('/login', async (req, res) => {
  const s = getOidcSettings();
  if (!s.enabled) return res.status(400).json({ error: '未启用 RainID 登录' });
  try {
    const config = await getOidcConfig();
    const codeVerifier = openidClient.randomPKCECodeVerifier();
    const codeChallenge = await openidClient.calculatePKCECodeChallenge(codeVerifier);
    const state = openidClient.randomState();
    oidcStates.set(state, { verifier: codeVerifier, createdAt: Date.now() });
    const url = openidClient.buildAuthorizationUrl(config, {
      redirect_uri: siteBase(req) + REDIRECT_PATH,
      scope: 'openid profile email',
      code_challenge: codeChallenge,
      code_challenge_method: 'S256',
      state,
    });
    res.redirect(url.href);
  } catch (err) {
    console.error('[RainID] login redirect error:', err.message);
    res.status(502).json({ error: 'RainID 服务暂不可用' });
  }
});

// ② 回调：state 校验 → 换 token → userinfo → 影子账号 → 发 JWT → 一次性 ticket → 302 前端
router.get('/callback', async (req, res) => {
  const state = req.query.state;
  const stored = state && oidcStates.get(state);
  if (!stored) {
    return res.status(400).send('登录状态已失效，请重新使用 RainID 登录');
  }
  oidcStates.delete(state); // state 一次性
  let config;
  try { config = await getOidcConfig(); }
  catch { return res.status(500).send('RainID 客户端未配置'); }

  const base = siteBase(req);
  const currentUrl = new URL(req.originalUrl, base);
  try {
    // openid-client 自动验 id_token：签名(RS256/JWKS) + iss(discovery issuer) + aud(client_id) + exp
    const tokens = await openidClient.authorizationCodeGrant(config, currentUrl, {
      pkceCodeVerifier: stored.verifier,
      expectedState: state,
      idTokenExpected: true,
    });
    const claims = tokens.claims();
    const sub = claims && claims.sub;
    if (!sub) throw new Error('id_token 缺少 sub');
    const userinfo = await openidClient.fetchUserInfo(config, tokens.access_token, sub);
    const user = findOrCreateRainidUser(sub, userinfo);
    const token = jwt.sign({ id: user.id, username: user.username, role: user.role }, SECRET, { expiresIn: '7d' });
    const ticket = crypto.randomBytes(16).toString('hex');
    oidcTickets.set(ticket, {
      jwt: token,
      username: user.username,
      role: user.role,
      email: user.email,
      email_verified: user.email_verified,
      createdAt: Date.now(),
    });
    res.redirect(frontLoginUrl(req, '?oidc_ticket=' + encodeURIComponent(ticket)));
  } catch (err) {
    // error 参数（access_denied / consent_required 等）或换 token 失败 → 回前端登录页带错误码
    const code = err && err.error;
    console.error('[RainID] callback error:', code || err.message);
    res.redirect(frontLoginUrl(req, '?oidc_error=' + encodeURIComponent(code || 'server_error')));
  }
});

// ③ 一次性 ticket 换本地 JWT（响应结构同 /api/auth/login，auth.js:91）
router.post('/exchange', (req, res) => {
  const ticket = req.body && req.body.ticket;
  if (!ticket) return res.status(400).json({ error: '缺少 ticket' });
  const rec = oidcTickets.get(ticket);
  if (!rec) return res.status(401).json({ error: '登录已过期，请重新使用 RainID 登录' });
  oidcTickets.delete(ticket); // 一次性
  res.json({
    token: rec.jwt,
    username: rec.username,
    role: rec.role,
    email: rec.email,
    email_verified: rec.email_verified,
  });
});

// ④ 登出联动：302 RainID end_session（post_logout_redirect_uri 需先在 RainID Admin 登记）
router.get('/logout', async (req, res) => {
  const s = getOidcSettings();
  if (!s.enabled) return res.redirect('/');
  try {
    const config = await getOidcConfig();
    const url = openidClient.buildEndSessionUrl(config, {
      post_logout_redirect_uri: siteBase(req) + LOGOUT_REDIRECT_PATH,
    });
    res.redirect(url.href);
  } catch (err) {
    console.error('[RainID] logout error:', err.message);
    res.redirect('/');
  }
});

module.exports = router;