Cart

The CartService in the Geins SDK OMS package is a stateless service for managing shopping carts. Every method takes a cartId (where applicable) and returns the full CartType. It holds no per-request state, making it safe for server-side shared singletons.

For browser-side convenience (cookie persistence, quantity increment/decrement), use the CartSession wrapper.

Overview

The CartService provides:

• Cart Lifecycle: Create, fetch, complete, and copy carts.
• Item Management: Add, update, and delete items.
• Promotion Codes: Apply and remove promotional codes.
• Shipping Fees: Configure shipping charges.
• Merchant Data: Store custom metadata on the cart.
• Cart Copying: Create new carts based on existing ones.
• Cart Completion: Mark carts as read-only after checkout.

Stateless API

const geinsOMS = new GeinsOMS(geinsCore);
const cart = geinsOMS.cart; // CartService instance (stateless)

All methods return the full CartType:

type CartType = {
  id: string;
  items: CartItemType[];
  freeShipping: boolean;
  readonly completed: boolean;
  readonly merchantData?: string;
  readonly promoCode?: string;
  readonly fixedDiscount: number;
  readonly appliedCampaigns: CampaignRuleType[];
  readonly summary: CartSummaryType;
};

Cart Management

Create

Creates a new cart and returns it with a generated ID.

const cart = await geinsOMS.cart.create();
console.log(`Cart created with id: ${cart.id}`);

Get

Fetches an existing cart by ID.

const cart = await geinsOMS.cart.get(cartId);
console.log(`Cart has ${cart.items.length} items`);

Complete

Marks a cart as completed (read-only). A completed cart cannot be modified.

const cart = await geinsOMS.cart.complete(cartId);
console.log(`Cart completed: ${cart.completed}`); // true

WARNING

Make sure not to complete a cart before the user has finished the checkout process. A completed cart cannot be modified.

Copy

Creates a new cart based on an existing one. Returns the new cart.

const newCart = await geinsOMS.cart.copy(cartId, { resetPromotions: true });
console.log(`Copied cart ID: ${newCart.id}`);

TIP

Use this in combination with merchant data to add features like "share cart as wishlist" to your application.

Item Methods

All item methods take cartId as the first argument and return the full updated CartType.

Add Item

const cart = await geinsOMS.cart.addItem(cartId, {
  skuId: 1234,
  quantity: 1,
});

Update Item

Sets an item to an exact quantity:

const cart = await geinsOMS.cart.updateItem(cartId, {
  skuId: 1234,
  quantity: 3,
  message: 'Gift wrapping please',
});

Delete Item

Removes an item entirely (by item ID):

const cart = await geinsOMS.cart.deleteItem(cartId, itemId);

See the Items page for full details.

Modifier Methods

Promotion Code

// Apply
const cart = await geinsOMS.cart.setPromotionCode(cartId, 'SUMMER20');

// Remove
const cart = await geinsOMS.cart.removePromotionCode(cartId);

Shipping Fee

const cart = await geinsOMS.cart.setShippingFee(cartId, 59);

Merchant Data

const data = JSON.stringify({ extraData: 'test', extraNumber: 123 });
const cart = await geinsOMS.cart.setMerchantData(cartId, data);

Session Layer (Browser)

For browser apps, CartSession wraps the stateless CartService with pluggable storage, event emission, typed errors, and convenience methods.

Basic Usage

import { CartSession } from '@geins/oms';

const session = new CartSession(geinsOMS.cart, locale);

// Reads cartId from storage, or creates a new cart
await session.get();

// Convenience: increments quantity if item already exists
await session.items.add({ skuId: 1234 });

// Convenience: decrements quantity
await session.items.remove({ skuId: 1234 });

// Direct access to cached cart
const items = session.items.get();

// Clear session (removes storage and cache)
session.remove();

Session Options

import { CartSession } from '@geins/oms';
import { MemoryStorage } from '@geins/core';

const session = new CartSession(geinsOMS.cart, locale, {
  storage: new MemoryStorage(),  // or CookieStorageAdapter (default)
  events: geinsCore.events,      // optional — enables cart events
});

Option	Type	Default	Description
storage	StorageInterface	CookieStorageAdapter	Where cart ID is persisted
events	EventService	undefined	Enables cart state change events

Events

When an EventService is provided, the session emits events using GeinsEventType:

Event	When
CART_ADD	Item added
CART_REMOVE	Item removed or deleted
CART_UPDATE	Item quantity updated
CART_CLEAR	All items cleared

Parent event CART is also emitted alongside each specific event.

import { GeinsEventType } from '@geins/types';

geinsCore.events.listenerAdd((data) => {
  console.log('Cart changed:', data);
}, GeinsEventType.CART);

Associate User

Link an anonymous cart to a user identity after login:

await cartSession.associateUser({
  userId: authResponse.user.userId,
  username: authResponse.user.username,
  customerType: authResponse.user.customerType,
});

This stores user info in the cart's merchant data, preserving any existing merchant data.

Error Handling

Cart operations throw typed CartError on failure:

import { CartError } from '@geins/core';

try {
  await session.items.add({ skuId: 1234 });
} catch (error) {
  if (error instanceof CartError) {
    console.error(error.code, error.message);
  }
}

The session layer is not safe for server-side shared singletons — use one instance per browser session.