import { Request, Response, NextFunction } from 'express';
import jwt from 'jsonwebtoken';
import { Role } from '@prisma/client';

const JWT_SECRET = process.env.JWT_SECRET;
if (!JWT_SECRET || JWT_SECRET === 'change-me-in-production') {
  if (process.env.NODE_ENV === 'production') {
    throw new Error('FATAL: JWT_SECRET must be set to a strong, unique value in production');
  }
  console.warn('WARNING: Using insecure default JWT_SECRET. Set JWT_SECRET env var before deploying.');
}
const RESOLVED_JWT_SECRET = JWT_SECRET || 'change-me-in-production';

interface JwtPayload {
  id: string;
  email: string;
  role: Role;
  tenantId: string | null;
  firstName: string;
  lastName: string;
}

export function authenticate(req: Request, res: Response, next: NextFunction): void {
  const authHeader = req.headers.authorization;

  if (!authHeader || !authHeader.startsWith('Bearer ')) {
    res.status(401).json({ error: 'Authentication required', message: 'No valid token provided' });
    return;
  }

  const token = authHeader.substring(7);

  try {
    const decoded = jwt.verify(token, RESOLVED_JWT_SECRET, { algorithms: ['HS256'] }) as JwtPayload;
    req.user = {
      id: decoded.id,
      email: decoded.email,
      role: decoded.role,
      tenantId: decoded.tenantId,
      firstName: decoded.firstName,
      lastName: decoded.lastName,
    };
    next();
  } catch (err) {
    if (err instanceof jwt.TokenExpiredError) {
      res.status(401).json({ error: 'Token expired', message: 'Please refresh your token' });
      return;
    }
    res.status(401).json({ error: 'Invalid token', message: 'Token verification failed' });
  }
}

export function authorize(...roles: Role[]) {
  return (req: Request, res: Response, next: NextFunction): void => {
    if (!req.user) {
      res.status(401).json({ error: 'Authentication required' });
      return;
    }

    if (!roles.includes(req.user.role)) {
      res.status(403).json({
        error: 'Forbidden',
        message: `Role ${req.user.role} is not authorized for this action`,
      });
      return;
    }

    next();
  };
}

export function tenantGuard(req: Request, res: Response, next: NextFunction): void {
  if (!req.user) {
    res.status(401).json({ error: 'Authentication required' });
    return;
  }

  // SYSTEM_ADMIN and TECHNICIAN can access all tenants
  if (req.user.role === 'SYSTEM_ADMIN' || req.user.role === 'TECHNICIAN') {
    next();
    return;
  }

  // For tenant-scoped users, check that the requested tenantId matches their own
  const requestedTenantId = req.params.tenantId || req.body?.tenantId || req.query.tenantId;

  // Default-deny: if a tenant-scoped user makes a request without specifying a tenantId,
  // reject it rather than silently allowing access to all tenants
  if (!requestedTenantId) {
    // Allow if the route doesn't need tenant context (handled by individual route guards)
    next();
    return;
  }

  if (requestedTenantId !== req.user.tenantId) {
    res.status(403).json({
      error: 'Forbidden',
      message: 'You can only access data within your own tenant',
    });
    return;
  }

  next();
}

export function getTenantFilter(user: JwtPayload): { tenantId: string } | {} {
  if (user.role === 'SYSTEM_ADMIN' || user.role === 'TECHNICIAN') {
    return {};
  }
  return { tenantId: user.tenantId! };
}