# FizzBuzz module iterates over a sequence of numbers, printing
# 'Fizz' on multiples of three, 'Buzz' for multiples of five,
# 'FizzBuzz' on multiples of both three and five, and otherwise
# prints the number itself.
module FizzBuzz
  # Main class that runs the application.
  class App
    # Constructor, checks and stores options.
    #
    # *Params*
    #   +options+: Hash containing :to and :from parameters.
    def initialize(options)
      # Make sure to/from values are provided as integers.
      unless options.has_key?(:from) && options[:from] % 1 === 0 &&
             options.has_key?(:to)   && options[:to]   % 1 === 0
        raise ArgumentError, 'Please provide to and from options as whole numbers.'
      end

      @from = options[:from].to_i
      @to   = options[:to].to_i
    end

    # Run application and print output based on parameters passed
    # to constructor.
    def run
      # Iterate over provided numbers.
      @from.upto @to do |number|
        if number.is_fizzbuzz
          puts 'FizzBuzz'
        elsif number.is_fizz
          puts 'Fizz'
        elsif number.is_buzz
          puts 'Buzz'
        else
          puts number
        end
      end
    end
  end

  # Utility methods to be included in Kernel::Integer.
  module Integer
    # True if integer is multiple of three.
    def is_fizz
      self % 3 === 0
    end

    # True if integer is multiple of five.
    def is_buzz
      self % 5 === 0
    end

    # True if integer is multiple of three and five.
    def is_fizzbuzz
      is_fizz && is_buzz
    end
  end
end

Integer.send :include, FizzBuzz::Integer

app = FizzBuzz::App.new from: 1, to: 100
app.run