/**
 * Authentication routes
 *
 * POST /api/v1/auth/login   — exchange username+password for a session cookie
 * POST /api/v1/auth/logout  — destroy the current session
 * GET  /api/v1/auth/me      — return the currently authenticated user
 * POST /api/v1/auth/setup   — one-time admin bootstrap (disabled after first user exists)
 */
import express from 'express';
import bcrypt from 'bcrypt';
import pool from '../db/pool.js';

const router = express.Router();

// ---------------------------------------------------------------------------
// BUG FIX #6: In-memory login rate limiter.
//
// Brute-force protection for POST /login. Tracks failed attempts per
// (IP, username) pair; after MAX_ATTEMPTS failures within WINDOW_MS the
// endpoint returns 429 for LOCKOUT_MS regardless of the password supplied.
//
// This is intentionally simple — no Redis dependency, no persistent state
// across restarts. For a production deployment behind a load balancer, use
// express-rate-limit with a Redis store or a dedicated WAF rule instead.
// ---------------------------------------------------------------------------
const MAX_ATTEMPTS  = parseInt(process.env.LOGIN_MAX_ATTEMPTS  || '10', 10);
const WINDOW_MS     = parseInt(process.env.LOGIN_WINDOW_MS     || String(15 * 60 * 1000), 10);  // 15 min
const LOCKOUT_MS    = parseInt(process.env.LOGIN_LOCKOUT_MS    || String(15 * 60 * 1000), 10);  // 15 min

// Map key → { attempts: number, lockedUntil: number | null, firstAttempt: number }
const loginAttempts = new Map();

// Housekeeping: prune expired entries every 10 min so the Map doesn't grow
// unboundedly on high-traffic or attack traffic.
setInterval(() => {
  const now = Date.now();
  for (const [key, entry] of loginAttempts.entries()) {
    const expired = entry.lockedUntil
      ? now > entry.lockedUntil
      : now - entry.firstAttempt > WINDOW_MS;
    if (expired) loginAttempts.delete(key);
  }
}, 10 * 60 * 1000).unref();

function getAttemptKey(req, username) {
  // Use the real client IP (trust proxy headers set by nginx/load-balancer)
  const ip = req.ip || req.socket.remoteAddress || 'unknown';
  return `${ip}:${(username || '').trim().toLowerCase()}`;
}

function checkRateLimit(req, username) {
  const key = getAttemptKey(req, username);
  const now = Date.now();
  const entry = loginAttempts.get(key);

  if (entry) {
    // Still locked out?
    if (entry.lockedUntil && now < entry.lockedUntil) {
      const retryAfterSec = Math.ceil((entry.lockedUntil - now) / 1000);
      return { limited: true, retryAfterSec };
    }
    // Window expired — reset
    if (now - entry.firstAttempt > WINDOW_MS) {
      loginAttempts.delete(key);
    }
  }
  return { limited: false };
}

function recordFailedAttempt(req, username) {
  const key = getAttemptKey(req, username);
  const now = Date.now();
  const entry = loginAttempts.get(key) || { attempts: 0, lockedUntil: null, firstAttempt: now };

  // Don't update firstAttempt if there's an existing entry within the window
  entry.attempts += 1;
  if (entry.attempts >= MAX_ATTEMPTS) {
    entry.lockedUntil = now + LOCKOUT_MS;
  }
  loginAttempts.set(key, entry);
}

function clearAttempts(req, username) {
  loginAttempts.delete(getAttemptKey(req, username));
}

// ---------------------------------------------------------------------------
// POST /login
// ---------------------------------------------------------------------------
router.post('/login', async (req, res, next) => {
  try {
    const { username, password } = req.body;

    if (!username || !password) {
      return res.status(400).json({ error: 'Username and password are required' });
    }

    // BUG FIX #6: Check rate limit before hitting the DB or bcrypt.
    const rateCheck = checkRateLimit(req, username);
    if (rateCheck.limited) {
      res.set('Retry-After', String(rateCheck.retryAfterSec));
      return res.status(429).json({
        error: `Too many failed login attempts. Try again in ${rateCheck.retryAfterSec} seconds.`,
      });
    }

    const result = await pool.query(
      'SELECT * FROM users WHERE username = $1',
      [username.trim().toLowerCase()]
    );

    if (result.rows.length === 0) {
      // Timing-safe: still run compare on a dummy hash so response time is constant
      await bcrypt.compare(password, '$2b$12$invalidhashpadding000000000000000000000000000000000000');
      recordFailedAttempt(req, username);
      return res.status(401).json({ error: 'Invalid credentials' });
    }

    const user = result.rows[0];
    const valid = await bcrypt.compare(password, user.password_hash);

    if (!valid) {
      recordFailedAttempt(req, username);
      return res.status(401).json({ error: 'Invalid credentials' });
    }

    // Successful login — clear any accumulated failed attempts
    clearAttempts(req, username);

    // Regenerate session ID to prevent fixation attacks
    req.session.regenerate((err) => {
      if (err) return next(err);
      req.session.userId   = user.id;
      req.session.username = user.username;
      req.session.role     = user.role;
      res.json({
        id:           user.id,
        username:     user.username,
        display_name: user.display_name,
        role:         user.role,
      });
    });
  } catch (err) {
    next(err);
  }
});

// ---------------------------------------------------------------------------
// POST /logout
// ---------------------------------------------------------------------------
router.post('/logout', (req, res, next) => {
  req.session.destroy((err) => {
    if (err) return next(err);
    res.clearCookie('connect.sid');
    res.json({ message: 'Logged out' });
  });
});

// ---------------------------------------------------------------------------
// GET /me
// ---------------------------------------------------------------------------
router.get('/me', async (req, res) => {
  // When auth is disabled return a synthetic user so the frontend auth-guard
  // never receives a 401. Prefer LOCAL_OPERATOR (explicit) or the OS user
  // running the server over a generic "Admin" — that label is misleading
  // because it implies an actual admin account is signed in.
  if (process.env.AUTH_ENABLED !== 'true') {
    const osUser = process.env.LOCAL_OPERATOR
      || process.env.USER
      || process.env.USERNAME
      || 'operator';
    return res.json({
      id: null,
      username: osUser.toLowerCase().replace(/[^a-z0-9._-]/g, ''),
      display_name: osUser,
      role: 'admin',
      synthetic: true,
    });
  }

  if (!req.session || !req.session.userId) {
    return res.status(401).json({ error: 'Not authenticated' });
  }
  try {
    const result = await pool.query(
      'SELECT id, username, display_name, role FROM users WHERE id = $1',
      [req.session.userId]
    );
    if (result.rows.length === 0) {
      req.session.destroy(() => {});
      return res.status(401).json({ error: 'User not found' });
    }
    res.json(result.rows[0]);
  } catch (err) {
    // Fallback to session data if DB unreachable
    res.json({
      id:       req.session.userId,
      username: req.session.username,
      role:     req.session.role,
    });
  }
});

// ---------------------------------------------------------------------------
// GET /setup-status  — does ANY user exist? login.html flips into setup mode
// automatically when this returns { needs_setup: true }, instead of forcing
// the operator to click "Create admin account".
// ---------------------------------------------------------------------------
router.get('/setup-status', async (req, res, next) => {
  try {
    const count = await pool.query('SELECT COUNT(*) FROM users');
    const n = parseInt(count.rows[0].count, 10);
    res.json({
      needs_setup:   n === 0,
      user_count:    n,
      auth_enabled:  process.env.AUTH_ENABLED === 'true',
    });
  } catch (err) { next(err); }
});

// ---------------------------------------------------------------------------
// POST /setup  — one-time first-admin bootstrap
// ---------------------------------------------------------------------------
router.post('/setup', async (req, res, next) => {
  try {
    const { username, password, display_name } = req.body;

    if (!username || !password) {
      return res.status(400).json({ error: 'Username and password are required' });
    }
    if (password.length < 8) {
      return res.status(400).json({ error: 'Password must be at least 8 characters' });
    }

    // Block if any user already exists
    const count = await pool.query('SELECT COUNT(*) FROM users');
    if (parseInt(count.rows[0].count, 10) > 0) {
      return res.status(403).json({
        error: 'Setup is already complete. Use an existing admin account to add more users.',
      });
    }

    const hash = await bcrypt.hash(password, 12);
    const result = await pool.query(
      `INSERT INTO users (username, password_hash, display_name, role)
       VALUES ($1, $2, $3, 'admin')
       RETURNING id, username, display_name, role`,
      [username.trim().toLowerCase(), hash, display_name || username]
    );

    res.status(201).json(result.rows[0]);
  } catch (err) {
    next(err);
  }
});

export default router;