app.rb

require_relative "router"
require_relative "task_repository"
require_relative "tasks_controller"

# Start a task repo and add a task to it
task_repository = TaskRepository.new
tasks_controller = TasksController.new(task_repository)
router = Router.new(tasks_controller)

router.run

router.rb

class Router
  def initialize(tasks_controller)
    @tasks_controller = tasks_controller
  end

  def run
    puts "Welcome to Taskmaster"
    loop do
      puts "What do you want to do?"
      puts "1. Create a task"
      puts "2. List tasks"
      puts "3. Mark a task as done"
      puts "0. Leave"
      
      user_input = gets.chomp.to_i
      case user_input
      when 1 then @tasks_controller.create
      when 2 then @tasks_controller.list
      when 3 then @tasks_controller.mark
      when 0 then break
      end
    end
  end
end

task.rb

class Task # model
  attr_reader :description

  def initialize(description)
    @description = description
    @done        = false
  end

  def done!
    @done = true
  end

  def done?
    @done
  end
end

task_repository.rb

class TaskRepository
  def initialize
    @tasks = []
  end

  def add(task_instance)
    @tasks << task_instance
  end

  def all
    @tasks
  end
end

task_view.rb

class TaskView
  def ask_for_description # instance method
    puts "Describe the task:"
    gets.chomp
  end

  def display(tasks)
    tasks.each_with_index do |task, index|
      # task -> Task instance
      box = task.done? ? "[X]" : "[ ]"
      puts "#{index + 1}. #{box} - #{task.description}"
    end
  end

  def ask_for_index
    puts "Which number?"
    gets.chomp.to_i - 1
  end
end

tasks_controller.rb

require_relative "task_view"
require_relative "task"

class TasksController
  # DATA
  # - Task view
  def initialize(task_repository)
    @task_view = TaskView.new
    @task_repository = task_repository
  end

  # User Action -> Create
  def create
    description = @task_view.ask_for_description
    task = Task.new(description)
    @task_repository.add(task)
  end

  # User Action -> List
  def list
    display_tasks
  end

  def mark
    display_tasks
    # Ask VIEW to ask user for a task number
    index = @task_view.ask_for_index
    # Get the task by index
    task = @task_repository.find(index)
    # Ask TASK instance to mark itself as done
    task.done!
  end

  private

  def display_tasks
    tasks = @task_repository.all
    @task_view.display(tasks)
  end
end