postcast-tool/app/api/billing/checkout/route.js

import { NextResponse } from 'next/server';
import { requireUser } from '@/lib/session';
import { engine } from '@/lib/engine';

export async function POST(req) {
  const user = await requireUser();
  if (!user) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
  try {
    const { plan_code } = await req.json();
    const data = await engine.call('/api/billing/checkout', {
      userId: user.id, method: 'POST', body: { plan_code },
    });
    return NextResponse.json(data);
  } catch (err) { return NextResponse.json({ error: err.message }, { status: 500 }); }
}