todo.rb

module ToDo
  class List
    include Enumerable

    def initialize
      @items = []
    end

    def each(&block)
      @items.each(&block)
    end

    def <<(item)
      @items << item
    end

    def [](index)
      @items[index]
    end

    def delete_at(index)
      @items.delete_at(index)
    end

    def size
      @items.size
    end
  end

  class UI
    def initialize
      @list = List.new
    end

    def run
      choice = nil

      until choice == :exit
        choice = menu
        case choice
          when :add    then add
          when :delete then delete
          when :show   then show
          when :exit   then true # do nothing
          when nil     then invalid_choice
        end
      end

      puts "Good bye!"
    end

    def get_integer
      gets.to_i
    end

    def invalid_choice
      puts "You just entered a wrong option, Going back to main menu"
    end

    def add
      puts "You selected to add a item to ToDo list",
           "Type your todo"

      @list << gets.chomp
    end

    def delete
      puts "You selected 2 to delete an item",
           "Enter a list no to delete?"

      number = get_integer
      puts "Deleting #{number} #{@list[number-1]}",
           "Are you sure?"
      if gets.chomp == "yes"
        @list.delete_at(number-1)
        puts "Deleted"
      else
        puts "item not deleted"
      end
    end

    def show
      puts "You selected 3 to display the list"
      @list.each.with_index(1) do |todo, number|
        puts "#{number}: #{todo}"
      end
    end

    def menu
      puts "Enter 1 to add, 2 delete, 3 to display the list, 4 to exit"
   
      [nil, :add, :delete, :show, :exit][get_integer]
    end
  end
end

ToDo::UI.new.run