import type { SimulationFunction } from '@x12i/api-simulator';
import { returnBook, LibraryError } from '../state/checkout-ledger.js';

/** POST /books/:bookId/return { memberId } */
export const returnBookHandler: SimulationFunction = ({ request }) => {
  const bookId = request.params.bookId ?? '';
  const memberId = (request.body as { memberId?: string } | undefined)?.memberId;

  if (!memberId) {
    return {
      status: 400,
      body: { error: 'MEMBER_ID_REQUIRED', message: 'Request body must include memberId.' }
    };
  }

  try {
    const record = returnBook(bookId, memberId);
    return { status: 200, body: { ...record, status: 'returned' } };
  } catch (error) {
    if (error instanceof LibraryError) {
      return { status: error.status, body: { error: error.code, message: error.message } };
    }
    throw error;
  }
};