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Cabify Mobile Challenge

Besides providing exceptional transportation services, Cabify also runs a physical store which sells Products.

Our list of products looks like this:

Code         | Name                |  Price
-------------------------------------------------
VOUCHER      | Cabify Voucher      |   5.00€
TSHIRT       | Cabify T-Shirt      |  20.00€
MUG          | Cabify Coffee Mug   |   7.50€

Various departments have insisted on the following discounts:

  • The marketing department believes in 2-for-1 promotions (buy two of the same product, get one free), and would like to have a 2-for-1 special on VOUCHER items.

  • The CFO insists that the best way to increase sales is with discounts on bulk purchases (buying x or more of a product, the price of that product is reduced), and demands that if you buy 3 or more TSHIRT items, the price per unit should be 19.00€.

Cabify's checkout process allows for items to be scanned in any order, and should return the total amount to be paid.

Examples:

Items: VOUCHER, TSHIRT, MUG
Total: 32.50€

Items: VOUCHER, TSHIRT, VOUCHER
Total: 25.00€

Items: TSHIRT, TSHIRT, TSHIRT, VOUCHER, TSHIRT
Total: 81.00€

Items: VOUCHER, TSHIRT, VOUCHER, VOUCHER, MUG, TSHIRT, TSHIRT
Total: 74.50€

To do

  • Implement an app where a user can pick products from a list and checkout them to get the resulting price. No need to implement any real payment system, just a fake feedback about the payment has been completed.
  • The discounts can change in the future, depending on the year season we apply different ones.
  • There is no need for a user login screen.
  • We would like to show users what discounts have been applied in their purchase.
  • You should get the list of products from here.

Bonus

  • The app should work also offline, and all that this implies.

The code should:

  • Be written as production-ready code. You will write production code. We would like you to build it in the same way as if you were going to publish to the store.
  • Be easy to grow and easy to add new functionality.
  • Have notes attached, explaning the solution and why certain things are included and others are left out.
  • Be written either in Swift or Kotlin, preferably in the latest stable version of the language.

Architecture

A customized version of VIPER is used as arquitecture pattern. The project is divided in the next layers:

-Presentation: The presentation folder contains all the classes to implement the presentation logic using MVP pattern.

-Domain: In this layer, we found the business logic of the app implemented using use cases.

-Data: The third layer is meant to provide access to the all the data of the app. It follows the repository pattern. Each repository give access to the data of a logical entity (for example, UserRepository for User entity). The repository sync one or more data sources (for example, RemoteDataSource and LocalDataSource)

Setup

The project uses Cocoapods as dependency manager. In order to set up the project runs pod install. Then open CabifyMobileChallenge.xcworkspace file

Localization

All strings used in the app are localized using NSLocalized API.

Testing

In order to test the app, some UI tests are added. The following dependencies are used:

  • KIF: iOS integration test framework. Allows to test UI
  • Cuckoo: Generate mocks automatically

To tests all the cases, Data Layer (Repositories) is mocked. In this way, a single test can cover:

  • ViewController
  • Presenter
  • Use cases

Error management

As we perform a network request to retrieve the list of the products, errors must be managed:

CustomError enum contains two errors:

  • NoInternetConnection: If there is no Internet connection
  • Unknown: For another type of errors

Design decisions

Discounts

In order to easily adds discounts, a protocol Discount is defined. I have decided that only one discount can be applied to each product, to avoid conflicts while applying two different discounts to one product.

A HardcodedDiscountDatasource is created to provide the discounts. New discounts can be easily added by modifiying it. In the future, the discounts could be obtained from a remote endpoint by using the URLRemoteDataSource

Shopping Cart

Shopping cart is modeled as a dictionary with Product as key and the quantity as value. Performance of this data structure is O(1)

In ShoppingCartViewController we show the discounts although the discounted amount is zero. In this way, user can know what discounts can be applied to the products.

Improvements

  • Specify a CI/CD pipeline to test and deliver the app automatically.
  • Test URLRemoteDataSource using https://github.com/AliSoftware/OHHTTPStubs or similar.
  • Add tests for repositories. I haven't add it because don't have so much logic.
  • Offline storage of product list and shopping cart.