Challenge Summary

We are in the business of selling Star Wars themed Legos. There is a database which stores data related to all the Lego products and its inventories. The database consists of two tables with the following schema.

products

• product_id (int): unique product identifier
• name (string): name of the product

inventories

• product_id (string): unique product identifier
• inventory (int): the count of the product inventory available
• updated_at (datetime): the datetime when the inventory was updated

We need to build a REST API to expose some basic functionality to the client to retrieve, create, and update product and inventory records.

Assumptions

1. We do not have to use a database for this exercise, instead, a very simple in-memory datastore is provided for you (see datastore.go for the interface and helpful usage example).
2. The test cases will automatically load the following seed data into the datastore and pass them to your server.
3. A basic router is provided that will forward requests to the relevant handler in your server, you just need to parse the request path and body (as needed), prepare and send an appropriate response.
4. An API spec is provided that shows all the operations you need to implement. Pay careful attention to the request methods and response codes. The tests will cover every error scenario included in the spec.

Sample Data

products

product_id	name
1	R2D2
2	Millennium Falcon
3	Darth Vader
4	Yoda

inventories

product_id	inventory	updated_at
1	100	2022-01-01
2	200	2022-01-02
3	50	2022-01-03
4	10	2022-01-04

API Spec

The API should support the following operations

Get all inventories

URL Path: /inventories

Sample Request: GET /inventories

Sample Response:

[
  {
    "product_id": 1,
    "name": "R2D2",
    "inventory": 100,
    "updated_at": "2022-01-01T00:00:00Z"
  },
  {
    "product_id": 2,
    "name": "Millenium Falcon",
    "inventory": 200,
    "updated_at": "2022-01-02T00:00:00Z"
  }
]

Errors: N/A

Get one inventory

URL path: /inventories/{product_id}

Sample Request: GET /inventories/1

Sample response:

{
    "product_id": 1,
    "name": "R2D2",
    "inventory": 100,
    "updated_at": "2022-01-01T00:00:00Z"
}

Errors:

• 404 (product not found): this status can also be used for invalid IDs

Create a new inventory record

URL path: /inventories/{product_id}

Sample Request: PUT /inventories/5

{
    "product_id": 5,
    "name": "C-3PO",
    "inventory": 40,
    "updated_at": "2022-09-21T00:00:00Z"
}

Sample Response:

{
   "product_id": 5,
   "name": "C-3PO",
   "inventory": 40,
   "updated_at": "2022-09-21T00:00:00Z"
}

Note: a successful create should return a 201 (created) status code.

Errors:

• 400 (Bad Request): malformed request (including mismatch between ID in URL and request body)
• 409 (Conflict): product with the same id already exists

Update an existing inventory

URL path: /inventories/{product_id}

Sample Request:

POST /inventories/5

{
   "inventory_adjustment": -3
}

Response:

{
   "product_id": 5,
   "name": "C-3PO",
   "inventory": 37,
   "updated_at": "2022-09-21T00:10:00Z"
}

Errors:

• 400 (Bad Request): malformed request. In addition to malformed JSON, 400 should be returned requested update would cause inventory to drop below zero.
• 404 (Not found): product not found

Tasks

• Complete the methods in server.go to load data from the provided datastore and render appropriate response.
• Ensure that your server passes all the supplied tests.

Instructor's Recommendations

The following are your instructor's recommendations on what you need to know and be comfortable with as concepts in order to successfully complete this challenge:

• Know how to write HTTP handlers
• Know how to read request bodies and using the json package to unmarshal payloads
• Know how to marshal JSON payloads back to a client
• Know which HTTP status codes to return in difference circumstances