const rateLimit = require("express-rate-limit");

const jwt = require('jsonwebtoken');
const prisma = require('../config/db');
const { mustEnrolTwoFactor } = require('../utils/twoFactor');

// The setup wizard's token may finish setup without 2FA for this long.
const SETUP_TOKEN_GRACE_SECONDS = 2 * 60 * 60;

// Protect routes - verify token
const protect = async (req, res, next) => {
  let token;

  // Check if token exists in headers
  if (req.headers.authorization && req.headers.authorization.startsWith('Bearer')) {
    try {
      // Get token from header
      token = req.headers.authorization.split(' ')[1];

      // Verify token — pin the algorithm so a token signed with an
      // unexpected/attacker-chosen algorithm is never accepted.
      const decoded = jwt.verify(token, process.env.JWT_SECRET, { algorithms: ['HS256'] });

      // Get user from the token (exclude password)
      req.user = await prisma.user.findUnique({
        where: { id: decoded.id },
        select: {
          id: true,
          name: true,
          email: true,
          role: true,
          isActive: true,
          createdAt: true,
          updatedAt: true,
          phoneNumber: true,
          tokenVersion: true,
          twoFactorEnabled: true
        }
      });

      if (!req.user) {
        res.status(401);
        return next(new Error('User not found'));
      }

      if (!req.user.isActive) {
        res.status(401);
        return next(new Error('User account is deactivated'));
      }

      // An admin viewing as this user: only while the session is live, and read-only.
      if (decoded.imp) {
        const { liveSession } = require('../utils/impersonation');
        const session = await liveSession(String(decoded.imp));
        if (!session || session.targetUserId !== req.user.id) {
          return res.status(401).json({ message: 'The impersonation session has ended.', code: 'IMPERSONATION_ENDED' });
        }
        req.impersonation = session;
        req.readOnly = true;
      }

      // Revocation check — tokenVersion in JWT must match DB
      // Old tokens without tokenVersion are treated as version 0
      const tokenVer = decoded.tokenVersion ?? 0;
      if (tokenVer !== req.user.tokenVersion) {
        res.status(401);
        return next(new Error('Session has been revoked. Please log in again.'));
      }

      // Admins and supervisors must use 2FA. A session that predates the
      // requirement (or the user's promotion) is sent back to log in, where they
      // enrol. The setup wizard's own token gets a short grace period.
      const inSetupGrace = decoded.setup === true && Date.now() / 1000 - (decoded.iat || 0) < SETUP_TOKEN_GRACE_SECONDS;
      // (An impersonating admin has already passed 2FA themselves.)
      if (!inSetupGrace && !req.impersonation && (await mustEnrolTwoFactor(req.user))) {
        return res.status(401).json({
          message: 'Two-factor authentication is required for your role. Please log in again to set it up.',
          code: 'TWO_FACTOR_REQUIRED',
        });
      }

      next();
    } catch (error) {
      console.error(error);
      res.status(401);
      return next(new Error('Not authorized, token failed'));
    }
  } else {
    res.status(401);
    return next(new Error('Not authorized, no token'));
  }
};

// Admin only middleware
const admin = (req, res, next) => {
  if (req.user && req.user.role === 'admin') {
    next();
  } else {
    res.status(403);
    return next(new Error('Not authorized as an admin'));
  }
};

// Staff or higher middleware
const staff = (req, res, next) => {
  if (req.user && (req.user.role === 'admin' || req.user.role === 'supervisor' || req.user.role === 'staff')) {
    next();
  } else {
    res.status(403);
    return next(new Error('Not authorized as staff'));
  }
};

// Supervisor or higher middleware
const supervisor = (req, res, next) => {
  if (req.user && (req.user.role === 'admin' || req.user.role === 'supervisor')) {
    next();
  } else {
    res.status(403);
    return next(new Error('Not authorized as a supervisor'));
  }
};

const loginLimiter = rateLimit({
  windowMs: 60 * 1000,
  max: 15,
  message: "Too many login attempts. Try again later.",
});

// Optional auth — populates req.user if a valid token is present, but never rejects the request
const optionalAuth = async (req, res, next) => {
  if (!req.headers.authorization || !req.headers.authorization.startsWith('Bearer')) {
    return next();
  }
  try {
    const token = req.headers.authorization.split(' ')[1];
    const decoded = jwt.verify(token, process.env.JWT_SECRET, { algorithms: ['HS256'] });
    const user = await prisma.user.findUnique({
      where: { id: decoded.id },
      select: { id: true, name: true, email: true, role: true, isActive: true, createdAt: true, updatedAt: true, phoneNumber: true, tokenVersion: true }
    });
    if (user && user.isActive && (decoded.tokenVersion ?? 0) === user.tokenVersion) {
      if (decoded.imp) {
        const { liveSession } = require('../utils/impersonation');
        const session = await liveSession(String(decoded.imp));
        req.readOnly = true;
        if (session && session.targetUserId === user.id) {
          req.user = user;
          req.impersonation = session;
        }
      } else {
        req.user = user;
      }
    }
  } catch {
    // Token invalid or expired — proceed without user
  }
  next();
};

module.exports = { protect, admin, staff, supervisor, loginLimiter, optionalAuth };