Shopify Commerce-Backend

A bare-bones back-end implementation of an online marketplace as described by the Shopify Intern Developer Challenge.

Table of Contents

• Overview
• Versions
• Endpoints
  • Inventory List
  • Inventory Detail
• Security
• Setup
• Next Steps

Overview

The purpose of this Django Web Application is to simulate an API for an online marketplace. My implementation uses a cart system to allow merchants to create, update and complete a cart object to organize customer purchases made to the marketplace back-end. The complete action for a cart can be considered the moment a customer has completed the transaction for the merchandise and allows the system to separate the financial transactions from the inventory management.

Versions

There are two versions of the API that are available on this web application.

commerce/v1/

This endpoint is the most basic version of the API where a user can present an item and quantity and the inventory is adjusted immediately.

commerce/v2/

v2 supports the cart object. Inventory is only updated when the cart work flow is followed.

Endpoints

Inventory List

commerce/v#/?avail=1

Methods supported: GET POST

This is the main endpoint to list all the items stored in the marketplace database.

The GET method lists all inventory. The query parameter avail=1 results in only the available inventory to be returned (inventory_count > 0) . In the absence of the query parameter, all inventory will be listed.

Ex: commerce/v1/?avail=1

[
    {
        "title": "pen",
        "price": 1.99,
        "inventory_count": 120
    },
    {
        "title": "shirt",
        "price": 10.99,
        "inventory_count": 167
    },
]    

v1 POST

The POST method requires a key-value pair listing the item information as follows:

{
  "title" : "pen",
  "quantity" : 100
}

If a successful operation occurs, the response received will be a relay of the items passed through. A successful transaction will result in the item inventory_count updating at the GET endpoint.

Note: If the quantity of an item passed through this endpoint exceeds the inventory_count available for the item, the operation will fail.

v2 POST

Version 2 of the commerce API follows a cart workflow. The cart has three different states (create, update, complete) and each state is set by the command key in the json that is passed to the API.

create A user must first create a cart using the create value. The user can also provide a name for the cart to give context as to what items might be in the cart.

{
  "command" : "create",
  "cart_name" : "stationary"
}

Below is the resultant response after a create post is made to the API. The cart_id must be retained for the following steps in the cart workflow.

{
  "cart_id" : 1
}

update Once a cart has been provisioned, users can add items to the cart via the update command. Each item must be entered one at a time with the appropriate quantity for each item. A user can add a duplicate version of an item.

{
  "command" : "update",
  "cart_id" : 1
  "title" : "pen",
  "quantity" : 5
}

Note: If the quantity of an item order passed through this endpoint exceeds the inventory_count available for the item, the update will fail.

complete Finally, once all items have been added to the cart, the user can call the complete command and provide the cart id. Once a cart has been completed, the inventory counts are updated and the cart can no longer be updated.

{
  "command" : "complete",
  "cart_id" : 1
}

Once the cart has been completed, the return json response will detail the total value of the cart at the time of completion.

{
  "message" : "cart complete!",
  "Total Value" : 14.95
}

Note: A cart can only be completed once. An attempt at updating the cart, or completing the cart again will fail.

Inventory Detail

commerce/v#/<str:title>/

Methods supported: GET

This API endpoint returns the item details for a given item title.

Ex: commerce/v2/pen/

{
    "title": "pen",
    "price": 1.99,
    "inventory_count": 120
}

Security

To prevent unauthorized access to the API endpoints, a token based authentication is integrated into the API. With every GET and POST call to the API, a bearer token needs to be sent along with the payload to ensure that the API accepts the methods. To receive a token, the user must do the following.

The user must provide their account credentials as a key-value pair in the body of their request as shown below:

{
	'username': 'user1',
	'password': 'userpassword'
}

The request must then be made to the url: api-token-auth/. The user must than store the token that is passed as a response. An example of the response can be seen below:

{
	'token': 'd525e2211d3a8ad0044fdf289299f5ec7b1abca7'
}

With the token acquired, every call to the API needs to have the following key-value pair in the header of request.

{
	'Authorization': 'Token d525e2211d3a8ad0044fdf289299f5ec7b1abca7'
}

Setup

Details to an example script that performs the basic funcationality can be found in v1_example.py. The cart workflow can be found in v2_example.py.

Next Steps

• Add caching to speed up API
• Add throttling
• Integrate OAuth2.0
• Look into porting system with GraphQL