selectors.ts

export const getCatalogState = createFeatureSelector<fromCatalog.State>('catalog');
export const getProducts = createSelector(
  getCatalogState,
  catalog => catalog.products,
);
export const getProductSkus = createSelector(
  getCatalogState,
  catalog => catalog.productSkus,
);
export const getCatalog = createSelector(
  getProductSkus,
  getProducts,
  (skus, products) => skus.map(sku => products[sku]),
);

export const getCartState = createFeatureSelector<fromCart.State>('cart');
export const getCartItems = createSelector(
  getCartState,
  cart => cart.cartItems,
);

export const getAllCartSummary = createSelector(
  getProducts,
  getCartItems,
  (products, cart): CartItem[] =>
    Object.keys(cart).map(sku => ({
      product: products[sku],
      amount: cart[sku],
    })),
);
export const getCartSummary = createSelector(getAllCartSummary, cart =>
  cart.filter(item => item.amount > 0),
);