ecommerce-patterns

E-commerce Patterns Skill

Platform Selection

Scenario	Platform
Enterprise B2B	OroCommerce
Enterprise B2C	Magento 2
Mid-market	Shopify Plus
Small business	WooCommerce, PrestaShop
Custom/Headless	Medusa, Saleor

---

Magento 2 Patterns

Module Structure

app/code/Vendor/Module/
├── Api/
│   └── Data/
│       └── EntityInterface.php
├── Block/
├── Controller/
│   └── Index/
│       └── Index.php
├── etc/
│   ├── module.xml
│   ├── di.xml
│   ├── routes.xml
│   └── frontend/
├── Model/
│   └── ResourceModel/
├── Setup/
├── view/
│   └── frontend/
│       ├── layout/
│       └── templates/
├── registration.php
└── composer.json

Dependency Injection

<!-- etc/di.xml -->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="Vendor\Module\Api\ServiceInterface" type="Vendor\Module\Model\Service"/>
    <type name="Vendor\Module\Model\Service">
        <arguments>
            <argument name="logger" xsi:type="object">Psr\Log\LoggerInterface</argument>
        </arguments>
    </type>
</config>

GraphQL

type Query {
    customProducts(
        search: String
        pageSize: Int = 20
        currentPage: Int = 1
    ): CustomProductOutput @resolver(class: "Vendor\\Module\\Model\\Resolver\\Products")
}

---

Cart & Checkout Patterns

Cart State Machine

Empty → Has Items → Checkout Started → Payment → Order Placed
                  ↑                    ↓
                  └──── Abandoned ←────┘

Checkout Flow

1. Cart Review
2. Shipping Address
3. Shipping Method
4. Payment Method
5. Order Review
6. Place Order
7. Confirmation

Price Calculation

Base Price
- Catalog Discounts
= Adjusted Price
× Quantity
= Line Total
+ Tax (if exclusive)
= Line Total with Tax
Σ All Lines
= Subtotal
+ Shipping
- Cart Discounts
= Grand Total