React Native (AsyncStorage) Add to Cart Functions

addToCartRNAsyncStorage.js

// @flow
// with flow types -> https://flow.org
import AsyncStorage from '@react-native-async-storage/async-storage';

// common types
type CartItem = { itemId: number, quantity: number };
type Cart = Array<CartItem>;

const CART: string = 'QUOTE_LIST';

const getCartItems = async (): Promise<Cart> => {
  const itemsInCart: string = await AsyncStorage.getItem(CART);
  if (!itemsInCart) {
    return [];
  }
  return JSON.parse(itemsInCart);
};

// Delete old cart and create a new one
const updateCartFunc = async (newCartItems: Cart): Promise<boolean> => {
  try {
    await AsyncStorage.removeItem(CART);
  } catch (e) {
    return false;
  }
  // new cart
  try {
    await AsyncStorage.setItem(CART, JSON.stringify(newCartItems));
  } catch (e) {
    return false;
  }

  return true;
};

// Add item to cart
// check if there is a cart, if not, create one
// check if item in cart, if so update it, if not, append to cart
export const addItemToCartFunc = async (
  itemId: number,
  quantity: number,
): Promise<boolean> => {
  try {
    let itemsInCart: ?Cart = await getCartItems();

    // cart is available -------------------->
    if (itemsInCart) {
      // check if in cart
      const requiredItemFromCart: ?CartItem = itemsInCart.find(
        (item) => item.itemId === itemId,
      );

      // item is already in cart
      if (requiredItemFromCart) {
        // remove form our items list
        const newItemsInCart: Cart = itemsInCart.filter(
          (itm) => itm !== requiredItemFromCart,
        );
        // update quentity
        const updatedItem: CartItem = {
          itemId: itemId,
          quantity: requiredItemFromCart.quantity + quantity,
        };
        newItemsInCart.push(updatedItem);
        return await updateCartFunc(newItemsInCart);
      }
      // item was not in cart
      else {
        const newItem: CartItem = {
          itemId: itemId,
          quantity: quantity,
        };
        itemsInCart.push(newItem);
        return await updateCartFunc(itemsInCart);
      }
    }
    // cart is not available -------------------->
    else {
      // create cart
      const newItem: CartItem = {
        itemId: itemId,
        quantity: quantity,
      };
      const newCart: Cart = [newItem];
      await AsyncStorage.setItem(CART, JSON.stringify(newCart));
    }
  } catch (e) {
    // error reading itemsInCart
    return false;
  }
  return true;
};

// reset cart
export const resetCartFunc = async (): Promise<boolean> => {
  try {
    await AsyncStorage.removeItem(CART);
  } catch (e) {
    return false;
  }

  return true;
};