/**
 * A tiny in-memory "database" for the demo.
 *
 * Catalog books use `@x12i/api-simulator/store`. Active checkouts stay on a Map
 * keyed by book+member (composite key), which is a natural fit alongside createStore.
 */
import { createStore } from '@x12i/api-simulator/store';
import { books, type Book } from '../data/books.js';

export interface CheckoutRecord {
  bookId: string;
  memberId: string;
  checkedOutAt: string;
  dueAt: string;
}

const CHECKOUT_DAYS = 14;

const catalog = createStore<Book>(books.map((book) => ({ ...book })));
const activeCheckouts = new Map<string, CheckoutRecord>();

const checkoutKey = (bookId: string, memberId: string): string => `${bookId}::${memberId}`;

export class LibraryError extends Error {
  readonly status: number;
  readonly code: string;

  constructor(status: number, code: string, message: string) {
    super(message);
    this.name = 'LibraryError';
    this.status = status;
    this.code = code;
  }
}

export const findBook = (bookId: string): Book | undefined => catalog.get(bookId);

export const listBooks = (): Book[] => catalog.all();

export const checkoutBook = (bookId: string, memberId: string): CheckoutRecord => {
  const book = catalog.get(bookId);
  if (!book) throw new LibraryError(404, 'BOOK_NOT_FOUND', `No book with id ${bookId}.`);
  if (book.copiesAvailable < 1) {
    throw new LibraryError(409, 'BOOK_UNAVAILABLE', `${book.title} has no available copies.`);
  }

  catalog.update(bookId, { copiesAvailable: book.copiesAvailable - 1 });
  const checkedOutAt = new Date();
  const dueAt = new Date(checkedOutAt.getTime() + CHECKOUT_DAYS * 24 * 60 * 60 * 1000);
  const record: CheckoutRecord = {
    bookId,
    memberId,
    checkedOutAt: checkedOutAt.toISOString(),
    dueAt: dueAt.toISOString()
  };
  activeCheckouts.set(checkoutKey(bookId, memberId), record);
  return record;
};

export const returnBook = (bookId: string, memberId: string): CheckoutRecord => {
  const key = checkoutKey(bookId, memberId);
  const record = activeCheckouts.get(key);
  if (!record) {
    throw new LibraryError(
      409,
      'NO_ACTIVE_CHECKOUT',
      `Member ${memberId} has no active checkout for book ${bookId}.`
    );
  }

  const book = catalog.get(bookId);
  if (book) {
    catalog.update(bookId, {
      copiesAvailable: Math.min(book.copiesTotal, book.copiesAvailable + 1)
    });
  }
  activeCheckouts.delete(key);
  return record;
};

export const checkoutsForMember = (memberId: string): CheckoutRecord[] =>
  [...activeCheckouts.values()].filter((record) => record.memberId === memberId);

export const resetLibraryState = (): void => {
  catalog.reset();
  activeCheckouts.clear();
};