An attempt to solve Mars Rover Kata

About

Based on this problem statement, this program calculates a rovers final position after traversing a given path within a terrain.

• Code related design decisions gives a high level overview of the approach & thought process behind the solution
• This program also uses the Flog metric to observe scores of individual methods.
  • I make use of the blog: What's a Good Flog Score? as a reference to see how the written code is currently fairing
  • In the entire app, the method Path#navigate_steps has the highest complexity score of 10.8
• One can see how the sample output looks like from the program output section

Code related design decisions

• The entities in the problem domain are - Rover, Position, Rectangular Plateau, Path and Four Cardinal compass directions: North, South, East & West

• A Rover has a Position. This satisfies a "has a" relationship hence I've made use of composition here.

• A Position has properties/attributes like an x cordinate, y coordinate, an orientation/direction which refers to one of the four cardinal compass directions(North, South, East, West) and it can travel within a terrain.

• The code is designed in such a way that a Rover can navigate freely within the perimeter of the specified terrain.

  • In case a Rover attempts to traverse outside the given terrain, they get a OutsideBoundaryLimitsError and an appropriate error message

• The code also checks to ensure that a Rover can only traverse along a valid path.

  • In case of an invalid step in the path, an InvalidStepError us returned with an appropriate error message

• With Single Responsibility Principle in mind, the responsibility of each class is:

  • A Rover class ensures the overall rover movement can happen along a specific path and within a given terrain
  • A Position class ensures that an entity makes the movement by one unit in either of the four compass directions - North, South, East, West
  • A Rectangular Plateau is the terrain within which actual permissible movement is checked
  • A Path class that has a clear representation of valid steps in a given path that a rover can take
  • A separate class each for the four compass directions - North, South, East and West with each respective class having a clear way of indicating what movement along that specific direction could look like and what comes to the left & right of each direction

Areas of Improvement

• The application can be further improved to read input dynamically from a given file and then print the output accordingly. I felt that's a more nice to have currently for the initial version of the app and hence I've not implemented this in the my first working iteration of the Mars Rover Kata.

Assumptions

• While moving horizontally or vertically, we specifically do not check the current value of orientation from within the Position class.
  • For the scope of the given problem statement, since the given compass directions determine the movement along the X & Y axis(through the #move method in their respective classes), I currently feel that could be a good start to determine how and when x & y coordinates can be incremented or decremented
  • Since we don't know what the future need of enhancing this application can currently look like, I leaned on the side of applying the YAGNI principle and not checking the orientation for the current position object when incrementing or decrementing the x or y coordinate.

Usage

Dependencies

• Ruby 3.2.2
• Please refer to the Gemfile for the other dependencies

Setup

• Run bundle install from a project's root directory to install the related dependencies.
  • A CI/CD setup running automated RSpec tests is also in place for new merge requests made to the current project

Running the program

One can run the Mars Rover program with the below command from the projects root directory.

ruby bin/deploy_mars_rover.rb

Running the tests

• One can run the specs from the project's root directory with the command rspec

Program Output

• Below is a sample program output run against the command ruby bin/deploy_mars_rover.rb

1 3 N
5 1 E