# Uniquify
#
# Return a version of the given 'base' string that is unique
# by appending a counter to it. Uniqueness is determined by
# repeated calls to the passed block.
#
# You can pass an initial value for the counter, if not given
# counting starts from 1.
#
# If `base` is a function/proc, we expect that calling it with a
# candidate counter returns a string to test/return.
class Uniquify
  def initialize(counter = nil)
    @counter = counter
  end

  def string(base)
    @base = base

    increment_counter! while yield(base_string)
    base_string
  end

  private

  def base_string
    if @base.respond_to?(:call)
      @base.call(@counter)
    else
      "#{@base}#{@counter}"
    end
  end

  def increment_counter!
    @counter ||= 0
    @counter += 1
  end
end