ruby-on-rails-engineer-v2.md

Job Description

https://wellfound.com/jobs/2404014-senior-ruby-engineer-remote-europe

Reedsy's (fictional) Merchandising Store

Reedsy would like to expand its business to include a merchandise store for our professionals. It will be comprised of 3 items:

Code         | Name                   |  Price
-------------------------------------------------
MUG          | Reedsy Mug             |   6.00
TSHIRT       | Reedsy T-shirt         |  15.00
HOODIE       | Reedsy Hoodie          |  20.00

We would like you to provide us with a small web application to help us manage this store.

Guidelines

Some important notes before diving into the specifics:

• we expect this challenge to be done using Ruby on Rails;
• any detail that is not specified throughout this assignment is for you to decide. Our questions and examples are agnostic on purpose, so as to not bias your toward a specific format. If you work at Reedsy you will make decisions and we want that to reflect here. This being said, if you spot anything that you really think should be detailed here, feel free to let us know;
• the goal of this challenge is to see if you're able to write code that follows development best practices and is maintainable. It shouldn't be too complicated (you don't need to worry about authentication, for example) but it should be solid enough to ship to production;
• regarding dependencies:
  • try to keep them to a minimum. It's OK to add a dependency that adds a localized and easy to understand functionality;
  • avoid dependencies that significantly break away from standard Rails or that have a big DSL to learn (e.g., Grape). It makes it much harder for us to evaluate the challenge if it deviates a lot from vanilla Rails. If in doubt, err on the side of using less dependencies or check with us if it's OK to use;
• in terms of database any of SQLite, PostgreSQL or MySQL will be fine;
• include also with your solution:
  • instructions on how to setup and run your application;
  • a description of the API endpoints with cURL examples.

Out of scope

Here's a non-exhaustive list of functionalities that you don't need to worry about in your solution:

• UI - the application should be API only, so don't include any sort of front-end;
• Swagger / Postman documentation or anything of that sort;
• authentication / authorization;
• filters / search / pagination;
• asynchronous jobs.

How do I know when to stop adding more functionalities?

This challenge was designed to not take too much of your precious time. If it's taking you the whole day or more, maybe it's time to wrap up what you already have and ship it.

Question 1

Implement an API endpoint that allows listing the existing items in the store, as well as their attributes.

Question 2

Implement an API endpoint that allows updating the price of a given product.

Question 3

Implement an API endpoint that allows one to check the price of a given list of items.

Some examples on the values expected:

Items: 1 MUG, 1 TSHIRT, 1 HOODIE
Total: 41.00

Items: 2 MUG, 1 TSHIRT
Total: 27.00

Items: 3 MUG, 1 TSHIRT
Total: 33.00

Items: 2 MUG, 4 TSHIRT, 1 HOODIE
Total: 92.00

Question 4

We'd like to expand our store to provide some discounted prices in some situations.

• 30% discounts on all TSHIRT items when buying 3 or more.
• Volume discount for MUG items:
  • 2% discount for 10 to 19 items
  • 4% discount for 20 to 29 items
  • 6% discount for 30 to 39 items
  • ... (and so forth with discounts increasing in steps of 2%)
  • 30% discount for 150 or more items

Make the necessary changes to your code to allow these discounts to be in place and to be reflected in the existing endpoints. Also make your discounts flexible enough so that it's easy to change a discount's percentage (i.e., with minimal impact to the source code).

Here's how the above price examples would be updated with these discounts:

Items: 1 MUG, 1 TSHIRT, 1 HOODIE
Total: 41.00

Items: 9 MUG, 1 TSHIRT
Total: 69.00

Items: 10 MUG, 1 TSHIRT
Total: 73.80

Explanation:
  - Total without discount: 60.00 + 15.00 = 75.00
  - Discount: 1.20 (2% discount on MUG)
  - Total: 75.00 - 1.20 = 73.80

Items: 45 MUG, 3 TSHIRT
Total: 279.90

Explanation:
  - Total without discount: 270.00 + 45.00 = 315.00
  - Discount: 21.60 (8% discount on MUG) + 13.50 (30% discount on TSHIRT) = 35.10
  - Total: 315.00 - 35.10 = 279.90

Items: 200 MUG, 4 TSHIRT, 1 HOODIE
Total: 902.00

Explanation:
  - Total without discount: 1200.00 + 60.00 + 20.00 = 1280.00
  - Discount: 360.00 (30% discount on MUG) + 18.00 (30% discount on TSHIRT) = 378.00
  - Total: 1280.00 - 378.00 = 902.00