class ActiveSupport::NumberHelper::RoundingHelper

def absolute_precision(number)
  if options[:significant] && options[:precision] > 0
    options[:precision] - digit_count(convert_to_decimal(number))
  else
    options[:precision]
  end
end

def convert_to_decimal(number)
  case number
  when Float, String
    BigDecimal(number.to_s)
  when Rational
    BigDecimal(number, digit_count(number.to_i) + options[:precision])
  else
    number.to_d
  end
end

def digit_count(number)
  return 1 if number.zero?
  (Math.log10(number.abs) + 1).floor
end

def initialize(options)
  @options = options
end

def round(number)
  precision = absolute_precision(number)
  return number unless precision
  rounded_number = convert_to_decimal(number).round(precision, options.fetch(:round_mode, :default).to_sym)
  rounded_number.zero? ? rounded_number.abs : rounded_number # prevent showing negative zeros
end