module UnitConversion
  class ParsedNumber

    attr_reader :value

    def initialize(str)
      @original_value = str
      @value = str.is_a?(Numeric) ? str : parse_value(str)
    end

    def to_s
      @value.to_s
    end

    def rational?
      value.is_a?(Integer) || value.is_a?(Rational)
    end

    def parse_value(str)
      if str =~ /^#{INTEGER_REGEX}$/
        str.to_i
      elsif str =~ /^#{RATIONAL_REGEX}$/
        parts = str.split(' ')
        if parts.length == 2
          whole = parts.first.to_r
          fractional = parts.last.to_r
          (whole.abs + fractional) * (whole < 0 ? -1.to_r : 1.to_r)
        else
          str.to_r
        end
      elsif str =~ /^#{DECIMAL_REGEX}$/
        str.to_d
      else
        raise UnparseableUnitError, "str [#{str}] is not a valid number"
      end
    end
  end
end