serverQueriesResolver.js

const paginateQuery = (query, page = 1, pageSize = 5) =>
  query.drop((page - 1) * pageSize).take(pageSize);

const product = ({ id }, { db }) => db.get("products").getById(id).value();

const products = ({ category }, { db }) => ({
  totalSize: () =>
    db
      .get("products")
      .filter((p) =>
        category ? new RegExp(category, "i").test(p.category) : p
      )
      .size()
      .value(),
  products: ({ page, pageSize, sort }) => {
    let query = db.get("products");
    if (category) {
      query = query.filter((item) =>
        new RegExp(category, "i").test(item.category)
      );
    }
    if (sort) {
      query = query.orderBy(sort);
    }

    return paginateQuery(query, page, pageSize).value();
  },
});

const categories = (args, { db }) => db.get("categories").value();

const resolveProducts = (products, db) =>
  products.map((p) => ({
    quantity: p.quantity,
    product: product({ id: p.product_id }, { db }),
  }));

const resolveOrders = (onlyUnshipped, { page, pageSize, sort }, { db }) => {
  let query = db.get("orders");
  if (onlyUnshipped) {
    query = query.filter({ shipped: false });
  }
  if (sort) {
    query = query.orderBy(sort);
  }
  return paginateQuery(query, page, pageSize)
    .value()
    .map((order) => ({
      ...order,
      products: () => resolveProducts(order.products, db),
    }));
};

const orders = ({ onlyUnshipped = false }, { db }) => ({
  totalSize: () =>
    db
      .get("orders")
      .filter((o) => (onlyUnshipped ? o.shipped === false : o))
      .size()
      .value(),
  orders: (...args) => resolveOrders(onlyUnshipped, ...args),
});

module.exports = { product, products, categories, orders }