IOTA for ruby

iota.rb

# inspired by https://github.com/golang/go/wiki/Iota
module IOTA
  class Counter
    def initialize(start, increment, max)
      @start = start
      @times = 0
      @increment = increment
      @max = max
    end

    def next
      actual = @start + (@times * @increment)

      if !@max.nil? && actual > @max
        raise "#{actual} exceeds max #{@max}! #{self}"
      end
      @times += 1

      actual
    end

    def to_s
      "IOTA(start=#{@start},times=#{@times},increment=#{@increment},max=#{@max})"
    end
  end

  def with_iota(start: 0, increment: 1, max: nil)
    yield Counter.new(start, increment, max)
  end
end

if __FILE__ == $0
  # run tests with ruby iota.rb
  require "minitest/autorun"

  class IOTATest < Minitest::Test
    include IOTA

    def test_works_with_defaults
      with_iota do |iota|
        assert_equal 0, iota.next
        assert_equal 1, iota.next
        assert_equal 2, iota.next
        assert_equal 3, iota.next
        assert_equal 4, iota.next
      end
    end

    def test_works_with_increment
      with_iota(start: 1, increment: 2) do |iota|
        assert_equal 1, iota.next
        assert_equal 3, iota.next
        assert_equal 5, iota.next
      end
    end

    def test_works_with_max
      with_iota(start: 1, increment: 2, max: 5) do |iota|
        assert_equal 1, iota.next
        assert_equal 3, iota.next
        assert_equal 5, iota.next

        assert_raises do
          iota.next
        end
      end
    end
  end
end