Nubank - Code Challenge

This challenge is part of job process from Nubank. It was necessary to make an application which authorizes transactions for a specific account following a set of predefined rules.

Technologies

• NodeJS - I chose to use it because I am used to and its where I feel more comfortable. Besides this the Node works good in these problems involving emit of events.
• Javascript - I think it will be better to use Typescript to avoid writing errors and improve the maintenance, but the challenge recommend do not use dependencies, I chose to use Vanilla.
• Jest - It is to make the tests. I chose Jest because its the tool that I most use to and I had experience working with Models mock using it.

Disclaimer

The Authorizer its an application that looks similar to a messaging queue, in my opinion. Its receive data, process it independently even has the data is not useful and delivery result. Therefore, I chose to think about the solution in these steps:

• Receive all data and saved it as operations;
• Transform it in common object that Authorizer could know what kind of data is (account/transaction);
• Process these formatted messages applying the business rules.

I decided to divide the generical and individual parts to better enjoy the process, so if Authorizer in the future must process another kind of data, it is only necessary to understand what is generical/individual and put correctly in each step.

I created 3 models:

• Account - It has some getters/setters, a method to do a transaction and another one to get a log message.
• Task - It is a helpful model to store the operations.
• Validator - It is a generic validator to apply the business rules. The business rules are compiled in a individual file cause it is something shared to the project. It is a object [key: value] that enables easily add, modify or delete some rule from kind of data.

Observation: I created a folder called examples with all example files to test each business rule.

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Run by Docker (recomendable)

1. You first must to build the image from project docker build -t authorizer .

2. After that you can run as standalone command, such example: docker run -i authorizer < examples/operations-account-already-initialized

Run without Docker

You must have Node 14 installed to run the project.

1. Install dependencies npm install

2. Create standalone command npm link

3. Execute the commands authorizer < examples/operations-account-not-initialized

Run tests

1. Make sure dependencies is already installed npm install

2. Run the tests npm test