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, but we do need a nice user experience where our customers can understand what items are they purchasing, the price and the discount we are applying.
• You should fetch the list of products from here .

Considerations

• Be aware that the discounts are going to change frequently. So the code should support that.
• There is no need for a user login screen.
• Be written as production-ready code. We would like you to build it in the same way as if you were going to publish to the store.
• Consider 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.
• If possible, use the latest stable version (no Betas) of Xcode or Android Studio.

Solution

I have solved this challenge with a simple and intuitive design, in which the user is informed at all times of all the available offers that the products have and the final discount that they get in total.

The solution is based on 3 main screens, a Modal Bottom Sheet (product detail) and an order confirmation screen.

The screens are:

1. Products: The list of Products is displayed with the offers available for each product and the option to see more details about it. In addition, a slider with photos of the available products is displayed.

2. Shopping cart: A list is displayed with all the products that are currently added to the cart. The units of each product are indicated, giving the option to increase, decrease or eliminate it from the basket. Also, the offer that each one has available is shown. On this screen, a summary of the price of all the items, the price of the total discounts and the total price, discounting the price of the discounts, is indicated. On this screen the user is shown the Pay button so that he can place his order.

3. Orders: A list is displayed with all the orders made, indicating the order number, date, order status, number of items purchased and the total price.

4. Product details: It is a Modal Bottom Sheet where the product information is displayed, including the price and the available offer and a button that indicates in real time if the product is in the basket or not, and gives the option of add them to the basket or go to the basket in case it is already added.

5. Order Confirmation: It is a screen that indicates that the order has been successfully placed and automatically redirects to the Products screen.

App screenshots:

Important considerations taken:

The Strategy package contains the configuration and logic of the product discount strategies and new discount strategies can be added, being scalable and maintainable.

Testing: Many unit tests of the application have been carried out, especially of the use cases, but more things could be tested.

Architecture

This project has been developed following the Clean Code and Clean Architecture principles and the good practices set by Google.

• Have a clear separation between layers, as can be seen in the explanation of Modules.
• Decoupling code using dependency injection.
• Use of MVVM design pattern.

MVVM

In my opinion, it is one of the best architectures to use in an application and have a scalable application and be able to control the states at all times. BasketShoppingViewModel is a good example viewmodel to see how it is used in the application.

Domain

In Domain you will find the definition of the model and the use cases of the application. All Use Cases make use of coroutines, which run on a thread that stays in the background and returns the result to the main thread when available.

Data

In Data there is the repository interface ProductApiClient that makes use of Retrofit to make the calls and makes use of Gson for the analysis of the responses and their subsequent conversion to the ProductEntity, BasketShoppingEntity and OrdersEntity objects, in addition to the repository file ProductRepository. There is also the interface of the local BBDD Room and its corresponding logic and files.

UI

In UI you will find all the screens of the user interface of the application, including their respective ViewModels and the Adapters in the necessary cases.

Libraries

Next, I will explain the libraries that I have used to develop the project:

Dependency Inversion: Hilt

I have used Hilt as dependency injection, because I have worked with it the most before and, furthermore, it is the one that Google recommends and has the most support from the community.

Database: Room

I have used as Room to store BBDD locally. I use Room on a daily basis and I feel comfortable using it, that's why I decided to use it in this project.

Coroutines: LiveData & Coroutines

I have used them as Coroutines because I think they are wonderful and I really like using them, in addition, it is essential to be able to manage the requests of the services in the background and not leave the application blocked to the user. Also, the learning curve is not even close to what it is with RxJava or RxKotlin.

Image Loader: Coil

I have used as Coil because it is the one that I usually use all the time.

Serialization: Gson

I have used as Gson but I think I am going to change it to Moshi because I think it can be more powerful and is more current.

Network: Retrofit

I have used as Retrofit because it is the most widely used library for making network calls and it is the one I have always used in all my projects.

Functional Programming: Firebase

I haven't used Firebase because of the size of the project and not to make it too fat, but I have worked a lot with Firebase, using all its features and the truth is that I really like it and above all, I feel very safe working with it.

Testing Mockk and Mockito: Mockk Mockito

I have used Mockk and Mockito for the programming of the test