// Passkeys (WebAuthn sign-in with Face ID, a fingerprint or a security key) and the list of devices signed in.
// A passkey is a second factor in itself (the device checks it is really you), so signing in with one skips the
// authenticator-code step. Passwords and 2FA keep working as before.
import { createHash } from 'crypto';
import {
  generateAuthenticationOptions, generateRegistrationOptions, verifyAuthenticationResponse, verifyRegistrationResponse,
} from '@simplewebauthn/server';
import {
  addPasskey, deletePasskey, destroyAllSessionsForUser, destroySession, getPasskey, getUserById, listPasskeys,
  listUserSessions, renamePasskey, setLoginAlerts, touchPasskey,
} from './db.js';
import { logEvent } from './health.js';
import { sendNtfy } from './reminders.js';

const MONTH = 30 * 24 * 60 * 60 * 1000;
const APP_NAME = 'Bible Study';

// "Chrome on macOS" from a User-Agent string; good enough to recognise your own devices.
export function describeDevice(ua = '') {
  const browser = /Edg\//.test(ua) ? 'Edge' : /OPR\//.test(ua) ? 'Opera' : /Firefox\//.test(ua) ? 'Firefox' : /Chrome\/|CriOS\//.test(ua) ? 'Chrome' : /Safari\//.test(ua) ? 'Safari' : null;
  const os = /iPhone/.test(ua) ? 'iPhone' : /iPad/.test(ua) ? 'iPad' : /Android/.test(ua) ? 'Android' : /Windows/.test(ua) ? 'Windows' : /Mac OS X|Macintosh/.test(ua) ? 'macOS' : /CrOS/.test(ua) ? 'ChromeOS' : /Linux/.test(ua) ? 'Linux' : null;
  if (browser && os) return `${browser} on ${os}`;
  return browser ?? os ?? 'Unknown device';
}

export const sessionKey = (sid) => createHash('sha256').update(sid).digest('hex').slice(0, 16);

// Where the browser says it is, for checking passkeys: APP_URL when set, else the address this request came to.
export function relyingParty(req, env = process.env) {
  if (env.APP_URL) {
    try { const u = new URL(env.APP_URL); return { rpID: u.hostname, origin: u.origin }; } catch { /* fall through */ }
  }
  return { rpID: req.hostname, origin: `${req.protocol}://${req.get('host')}` };
}

/** Called right after a session gets its userId: remembers the device and (if asked) sends a sign-in alert. */
export function noteSignIn(req, user, method) {
  const label = describeDevice(req.get('user-agent') ?? '');
  req.session.device = { label, ip: req.ip, at: Date.now(), method };
  if (user.loginAlerts && user.ntfyTopic) {
    const how = { password: 'password', passkey: 'passkey', mfa: 'password and authenticator code', register: 'a new account' }[method] ?? method;
    sendNtfy(user, { title: 'New sign-in', body: `${label} signed in to your Bible Study account with ${how}. If that wasn’t you, change your password and sign out other devices.`, tags: 'warning' })
      .catch((err) => { console.error('Sign-in alert failed:', err.message); logEvent('notify', `Sign-in alert: ${err.message}`, { userId: user.id }); });
  }
}

const publicPasskey = (p) => ({ id: p.id, name: p.name, createdAt: p.createdAt, lastUsedAt: p.lastUsedAt });

export function registerDeviceRoutes(app, { requireAuth, userPayload, isLimited, recordFailure, clearFailures, tooMany }) {
  const fail = (res, status, error) => res.status(status).json({ error });

  // ---- Signing in with a passkey (no email needed: the passkey says who you are) ----
  app.post('/api/auth/passkey/options', async (req, res) => {
    try {
      if (isLimited(`ip:${req.ip}`)) return res.status(429).json(tooMany);
      const { rpID } = relyingParty(req);
      const options = await generateAuthenticationOptions({ rpID, userVerification: 'required' });
      req.session.passkeyChallenge = options.challenge;
      res.json(options);
    } catch (err) {
      console.error('POST /api/auth/passkey/options error:', err);
      fail(res, 500, 'Could not start passkey sign-in.');
    }
  });

  app.post('/api/auth/passkey/verify', async (req, res) => {
    const keys = [`ip:${req.ip}`];
    try {
      if (isLimited(...keys)) return res.status(429).json(tooMany);
      const challenge = req.session?.passkeyChallenge;
      const response = req.body;
      const passkey = typeof response?.id === 'string' ? getPasskey(response.id) : null;
      const failed = () => { recordFailure(...keys); logEvent('signin', `Passkey sign-in failed from ${req.ip}`); return fail(res, 401, 'That passkey didn’t work. Try again, or use your password.'); };
      if (!challenge || !passkey) return failed();
      const { rpID, origin } = relyingParty(req);
      let result;
      try {
        result = await verifyAuthenticationResponse({
          response, expectedChallenge: challenge, expectedOrigin: origin, expectedRPID: rpID, requireUserVerification: true,
          credential: { id: passkey.id, publicKey: Buffer.from(passkey.publicKey, 'base64url'), counter: passkey.counter, transports: passkey.transports },
        });
      } catch { return failed(); }
      if (!result.verified) return failed();
      const user = getUserById(passkey.userId);
      if (!user) return failed();
      touchPasskey(passkey.id, result.authenticationInfo.newCounter);
      clearFailures(...keys);
      req.session.regenerate((err) => {
        if (err) return fail(res, 500, 'Could not create session.');
        req.session.userId = user.id;
        noteSignIn(req, user, 'passkey');
        res.json(userPayload(user));
      });
    } catch (err) {
      console.error('POST /api/auth/passkey/verify error:', err);
      fail(res, 500, 'Could not check that passkey.');
    }
  });

  // ---- Managing passkeys (signed in) ----
  app.get('/api/passkeys', requireAuth, (req, res) => res.json(listPasskeys(req.session.userId).map(publicPasskey)));

  app.post('/api/passkeys/options', requireAuth, async (req, res) => {
    try {
      const user = getUserById(req.session.userId);
      const { rpID } = relyingParty(req);
      const options = await generateRegistrationOptions({
        rpName: APP_NAME, rpID, userName: user.email, userID: new TextEncoder().encode(user.id), attestationType: 'none',
        excludeCredentials: listPasskeys(user.id).map((p) => ({ id: p.id, transports: p.transports })),
        authenticatorSelection: { residentKey: 'required', userVerification: 'required' },
      });
      req.session.passkeyChallenge = options.challenge;
      res.json(options);
    } catch (err) {
      console.error('POST /api/passkeys/options error:', err);
      fail(res, 500, 'Could not start adding a passkey.');
    }
  });

  app.post('/api/passkeys', requireAuth, async (req, res) => {
    try {
      const challenge = req.session.passkeyChallenge;
      if (!challenge) return fail(res, 400, 'Start again: that request expired.');
      const { rpID, origin } = relyingParty(req);
      let result;
      try {
        result = await verifyRegistrationResponse({ response: req.body?.response, expectedChallenge: challenge, expectedOrigin: origin, expectedRPID: rpID, requireUserVerification: true });
      } catch (err) { return fail(res, 400, `That passkey couldn’t be added (${err.message}).`); }
      if (!result.verified) return fail(res, 400, 'That passkey couldn’t be added.');
      delete req.session.passkeyChallenge;
      const { credential } = result.registrationInfo;
      if (getPasskey(credential.id)) return fail(res, 409, 'That passkey is already registered.');
      const name = String(req.body?.name ?? '').trim().slice(0, 60) || describeDevice(req.get('user-agent') ?? '');
      addPasskey({ id: credential.id, userId: req.session.userId, publicKey: Buffer.from(credential.publicKey).toString('base64url'), counter: credential.counter, transports: credential.transports, name });
      res.json(listPasskeys(req.session.userId).map(publicPasskey));
    } catch (err) {
      console.error('POST /api/passkeys error:', err);
      fail(res, 500, 'Could not save that passkey.');
    }
  });

  app.patch('/api/passkeys/:id', requireAuth, (req, res) => {
    const name = String(req.body?.name ?? '').trim().slice(0, 60);
    if (!name) return fail(res, 400, 'Give it a name.');
    if (!renamePasskey(req.params.id, req.session.userId, name)) return fail(res, 404, 'No such passkey.');
    res.json(listPasskeys(req.session.userId).map(publicPasskey));
  });

  app.delete('/api/passkeys/:id', requireAuth, (req, res) => {
    if (!deletePasskey(req.params.id, req.session.userId)) return fail(res, 404, 'No such passkey.');
    res.json(listPasskeys(req.session.userId).map(publicPasskey));
  });

  // ---- Where you are signed in ----
  app.get('/api/sessions', requireAuth, (req, res) => {
    const rows = listUserSessions(req.session.userId).map(({ sid, sess, expires }) => ({
      id: sessionKey(sid), current: sid === req.sessionID,
      label: sess.device?.label ?? 'Signed in before this list existed', ip: sess.device?.ip ?? null,
      method: sess.device?.method ?? null, signedInAt: sess.device?.at ?? null,
      lastSeen: expires - MONTH, // sessions are renewed on each request, so this is when it was last used
    })).sort((a, b) => Number(b.current) - Number(a.current) || b.lastSeen - a.lastSeen);
    res.json(rows);
  });

  app.delete('/api/sessions/:id', requireAuth, (req, res) => {
    const found = listUserSessions(req.session.userId).find((s) => sessionKey(s.sid) === req.params.id);
    if (!found) return fail(res, 404, 'That device is already signed out.');
    if (found.sid === req.sessionID) return fail(res, 400, 'Use Sign out for this device.');
    destroySession(found.sid);
    res.json({ ok: true });
  });

  app.post('/api/sessions/sign-out-others', requireAuth, (req, res) => {
    destroyAllSessionsForUser(req.session.userId, req.sessionID);
    res.json({ ok: true });
  });

  app.put('/api/auth/login-alerts', requireAuth, (req, res) => {
    const user = getUserById(req.session.userId);
    const enabled = !!req.body?.enabled;
    if (enabled && !user.ntfyTopic) return fail(res, 400, 'Set up a notification topic first (under Notifications).');
    setLoginAlerts(user.id, enabled);
    res.json({ loginAlerts: enabled });
  });
}