Simplify handling of negative durations

We can condense our code a bit by handling the sign at the point where
we coerce the duration parts from strings to numbers.

Author: Simon Coffey

lib/onelogin/ruby-saml/utils.rb

@@ -59,25 +59,17 @@ def self.parse_duration(duration, timestamp=Time.now.utc)
           raise Exception.new("Invalid ISO 8601 duration")
         end
 
+        sign = matches[1] == '-' ? -1 : 1
+
         durYears, durMonths, durDays, durHours, durMinutes, durSeconds, durWeeks =
           matches[2..8].map do |match|
             if match.nil?
               0.0
             else
-              match.tr(',', '.').to_f
+              sign * match.tr(',', '.').to_f
             end
           end
 
-        if matches[1] == "-"
-          durYears = -durYears
-          durMonths = -durMonths
-          durDays = -durDays
-          durHours = -durHours
-          durMinutes = -durMinutes
-          durSeconds = -durSeconds
-          durWeeks = -durWeeks
-        end
-
         initial_datetime = Time.at(timestamp).utc.to_datetime
         final_datetime = initial_datetime.next_year(durYears)
         final_datetime = final_datetime.next_month(durMonths)