megaverse-exercise

tonilopezmr.com Megaverse exercise

I have created an empty Spring boot project thinking I'd create an API, but finally, I have created a simple App.

That's why to run the project you can use springBoot features.

Code Entry Point

TonilopezmrApplication.kt is the code entry point where everything starts.

You can configure the TONILOPEZMR_CANDIDATE_ID with a different CANDIDATE-ID.

The App Creates a Megaverse from a Goal map returned by the Megaverse API. It sends one request per second to not receive a rate limit, It can be adjusted in Coroutines.kt changing how much requests (batchSize) you want to do in parallel per second (delayInSeconds).

The App can be run in parallel if you increase the batchSize, but also It can be done sequentially by changing the Coroutine Context.

Programming Style

I have tried to create a simple app meanwhile I showcase what I think is important.

Errors

I have decided to throws errors to stop the App, there are many ways to handle errors, but this way the code is easy to read for this test.

In Kotlin/Java I prefer to use Result which is a Either<A, Exception> than throwing errors because the methods give more transparency than throwing errors.

Structure

As It's a small App, I'm not sure how structured it is, I didn't want to create so many folders / subfolders.

domain package: Domain models of the App usecases package: App Actions like Get Goal Map and Create Megaverso services package: External Services like MegaverseAPI

Domain

sealed class AstralObject(val x: Int, val y: Int)
data class EmptySpace(val row: Int, val column: Int) : AstralObject(row, column)
data class POLYanet(val row: Int, val column: Int) : AstralObject(row, column)
data class SOLoon(val color: Color, val row: Int, val column: Int) : AstralObject(row, column)
data class ComETH(val direction: Direction, val row: Int, val column: Int) : AstralObject(row, column)

For each AstralObject I save the x,y position for easy Objects manipulations. AstralObject is a sealed class to be able to know the inheritance in compile time and don't miss any case or the build won't compile.

Decoupling

App Layer -> Bussines logic -> External Services

It's important to decouple App layer from business logic layer and External Services layer, that's why each layer uses different DTO's and Objects through mappers. Using Megaverse instead of Array<Array<String>> or SOLoon instead of BLUE_SOLOON or SOLoonBody.

Extension

object AstralObjectBuilder {

  private val possibleAstralObjects = listOf(
    EmptySpaceProcessor(),
    POLYanetProcessor(),
    SOLoonProcessor(),
    ComETHProcessor()
  )

  fun build(rawAstralObject: String, row: Int, column: Int): AstralObject =
    possibleAstralObjects.firstNotNullOfOrNull { it.process(rawAstralObject, row, column) }
      ?: throw UnidentifiedAstralObject(rawAstralObject)
}

If in the future there are new Astral Objects from the API, we would create a new AstralObjectProcessor and add it to the possibleAstralObjects list.

private fun create(candidateId: String, megaverse: Megaverse, astralObject: AstralObject) = when (astralObject) {
    is ComETH -> apiService.createCometh(candidateId, astralObject)
    is POLYanet -> apiService.createPolyanet(candidateId, astralObject)
    is SOLoon -> create(candidateId, megaverse, astralObject)
    is EmptySpace -> false
  }

Probably that will require we need to create a new AstralObject child, and our Build will fail because we don't contemplate the option in our when.

Tests

I have been creating the tests at the same time I develop, creating smaller cases to make sure what I'm coding is right.

90% of the tests are unit tests except:

MegaverseAPIServiceIntegrationTest.kt which makes Network API calls.
TonilopezmrMegaverseAppTest.kt which makes an Integration App tests, except Making Network Calls.

⚠️ MegaverseAPIServiceIntegrationTest.kt doesn't work because, I created the tests when I was implementing the API, once the challenge is solved, the API returns 500 error.

How to run it

Execute the TonilopezmrApplication:

./gradlew bootRun

How to execute the tests

 ./gradlew test

Code linter

Check code style:

./gradlew ktlintCheck

Check and solve the code style problems that can be solved automatically:

./gradlew ktlintFormat

tonilopezmr / megaverse-exercise