Refactoring Interview Problem

The goal of this problem is to try to see how you tackle refactoring code from one project to another.

Project Goals

The goal of this problem is to refactor the logic in the monolith project so that it resides in the library project. There are a few pre-written tests in the library project that should be re-enabled and made to pass.

Constraints

You are not allowed to change any code inside of the external sub-project.
The monolith project must depend upon the library project and the external project. The library project can not depend upon the external project. (The project is already configured this way, if you don't touch the build files you should be fine.)
You should not need to change the AlgorithmEngineTest but you are free to change the AlgorithmEngine as much as you wish.

Hints

Are there methods that are instance methods that could be made static?
- If a method has a dependency on a field, could that field be passed as an argument instead?
Are there methods that can be made private?
Are there fields in classes that are not being used?
In general, constructors should "do no work". Instead, try to make it so that constructors are simply assigning their parameters to fields.
In IntelliJ pressing F6 when a class is selected in the project view will pull up a UI to help moving classes. This can also be used to move static methods to another class.
If a symbol can't be resolved after moving it, make sure that the type has the right access level. Eg. private, public, protected, "package private". In Kotlin internal is nearly equivalent to Java's "package private".
Look for TODOs in the source code for additional pointers.

Solutions to Potential Problems

When moving code around IntelliJ may cause problems where IntelliJ can't find symbols it should be able to find. If you start seeing java: cannot find symbol and you think the type should be seen by the compiler try the following:

Refresh your projects by using ⌘ + Shift + A and typing "refresh all external projects". Then hit enter.
From the top menu do Build -> Rebuild Project.

If this does not work then try the following.

Click the "Gradle" tab on the right side of IntelliJ. Then click the blue refresh button on the Gradle tab that has appeared. Then try Build -> Rebuild Project again.
Contact me directly with your problem.

Environment Setup

You will need:

JDK 8 installed on your machine with the $JAVA_HOME environment variable set correctly.
A recent version of IntelliJ IDE Community Edition.

Configure IntelliJ IDEA Community Edition

In order to setup IntelliJ for development use the following steps:

If you already have a project open use File -> Open or just select Open from the welcome screen.
Select the settings.gradle file and click Open.
When prompted:
1. Un-check the Create seperate module per source set option.
2. Check the Use auto-import option.
3. Make sure the Gradle JVM option is set to 1.8.
Wait for the project to load.
Update your Kotlin Plugin:
1. Open the Kotlin Plugin Updates window using ⌘ + Shift + A and typing "kotlin plugin updates".
2. Ensure Stable is selected and press Check for updates.
3. Update and restart IntelliJ when prompted (if necessary).

Testing Before Submission

Before you submit this project make sure you run ./gradlew check this will ensure that your submission passes all tests and conforms to the style formatter.

Reformatting Your Code Before Submission

To reformat your code quickly simply run ./gradlew spotlessApply.

Preparing For Your Interview

Be prepared to discuss your solution during your interview.

JLLeitschuh / refactoring-interview-question