/**
 * GET /api/users - Benutzerverwaltung (nur ADMIN).
 *
 * Liefert alle Benutzer mit Rolle und Kalender-Beziehungen, damit
 * ein Admin Rollen vergeben und Zuordnungen ueberblicken kann.
 */
import { NextResponse } from 'next/server';
import { prisma } from '@/lib/db/client';
import { requireDbUser } from '@/lib/api/context';
import { errorResponse, forbiddenResponse } from '@/lib/api/responses';

export async function GET(): Promise<NextResponse> {
  try {
    const user = await requireDbUser();
    if (user.role !== 'ADMIN') {
      return forbiddenResponse();
    }

    const users = await prisma.user.findMany({
      orderBy: { createdAt: 'asc' },
      select: {
        id: true,
        email: true,
        username: true,
        role: true,
        createdAt: true,
        memberships: {
          select: {
            calendar: { select: { id: true, title: true, isActive: true } },
          },
        },
        ownedCalendars: {
          select: { id: true, title: true, isActive: true },
        },
      },
    });

    return NextResponse.json({ users });
  } catch (error) {
    return errorResponse(error);
  }
}