excercise.rb

# https://dev.to/r0f1/write-a-simple-but-impactful-script-7ba
# Write a script that produces all possible 4-digit numbers (0000...9999), 
# then put them into a random order and 
# save the output into a text file

class ExcerciseOrquestrator

  attr_reader :output_file_name

  def initialize(output_file_name)
    @output_file_name = output_file_name
  end

  def process(digits)
    output = NumberGenerator.new(digits).process
    write_to_file(output)
  end
  private

  def write_to_file(output)
    open_file do |file|
      output.each do |row|
        file.write("#{row}\n")
      end
    end
  end

  def open_file
    File.open(output_file_name, 'w') do |file|
      yield(file)
    end
  end
end


class NumberGenerator
  attr_reader :digits

  def initialize(digits)
    @digits = digits
  end

  def max_number
    (10 ** digits) -1
  end

  def first_number
    0
  end

  def process
    arr = do_generate
    (arr || []).shuffle
  end

  private

  def do_generate
    (first_number..max_number).each_with_object([]) do |digit, acc|
      acc << digit.to_s.rjust(digits, '0')
    end
  end
end


ExcerciseOrquestrator.new('randon_numbers').process(4)