import { NextRequest, NextResponse } from 'next/server';
import { jwtVerify } from 'jose';

/**
 * Next.js middleware for frontend route protection (Pattern 4).
 *
 * Validates JWT session cookie on every request. Redirects to /login
 * if missing or invalid. This is an optimistic check -- the API still
 * validates the JWT independently on every request.
 */

const publicRoutes = ['/login', '/reset-password'];

function getSecret() {
  const secret = process.env.JWT_SECRET || process.env.SESSION_SECRET;
  if (!secret) {
    // In development, allow a fallback to prevent startup crashes
    // when env vars are not yet configured
    return new TextEncoder().encode('development-secret-change-me');
  }
  return new TextEncoder().encode(secret);
}

export async function middleware(req: NextRequest) {
  const path = req.nextUrl.pathname;

  // Allow public routes without authentication
  if (publicRoutes.some((route) => path.startsWith(route))) {
    return NextResponse.next();
  }

  // Skip static assets and API routes (handled by NestJS)
  if (
    path.startsWith('/_next/static') ||
    path.startsWith('/_next/image') ||
    path.startsWith('/favicon.ico') ||
    path.startsWith('/api')
  ) {
    return NextResponse.next();
  }

  // Read session cookie
  const session = req.cookies.get('session')?.value;

  if (!session) {
    return NextResponse.redirect(new URL('/login', req.nextUrl));
  }

  try {
    const { payload } = await jwtVerify(session, getSecret(), {
      algorithms: ['HS256'],
    });

    // D-06: Force password change redirect
    if (
      payload.mustChangePassword === true &&
      !path.startsWith('/change-password')
    ) {
      return NextResponse.redirect(new URL('/change-password', req.nextUrl));
    }

    return NextResponse.next();
  } catch {
    // JWT verification failed -- clear stale cookie and redirect to login
    const response = NextResponse.redirect(new URL('/login', req.nextUrl));
    response.cookies.delete('session');
    return response;
  }
}

export const config = {
  matcher: ['/((?!api|_next/static|_next/image|.*\\.png$).*)'],
};