move recurrence text helpers into patterns. move next_date calculation into

respective models

app/models/recurring_todos/weekly_repeat_pattern.rb

@@ -35,6 +35,48 @@ module RecurringTodos
       errors[:base] << "You must specify at least one day on which the todo recurs" unless something_set
     end
 
+    def get_next_date(previous)
+      # determine start
+      if previous.nil?
+        start = start_from.nil? ? Time.zone.now : self.start_from
+      else
+        start = previous + 1.day
+        if start.wday() == 0
+          # we went to a new week , go to the nth next week and find first match
+          # that week. Note that we already went into the next week, so -1
+          start += (every_x_week-1).week
+        end
+        unless self.start_from.nil?
+          # check if the start_from date is later than previous. If so, use
+          # start_from as start to search for next date
+          start = self.start_from if self.start_from > previous
+        end
+      end
+
+      day = find_first_day_in_this_week(start)
+      return day unless day == -1
+
+      # we did not find anything this week, so check the nth next, starting from
+      # sunday
+      start = start + self.every_x_week.week - (start.wday()).days
+
+      start = find_first_day_in_this_week(start)
+      return start unless start == -1
+
+      raise Exception.new, "unable to find next weekly date (#{self.every_day})"
+    end
+
+    private
+
+    def find_first_day_in_this_week(start)
+      # check if there are any days left this week for the next todo
+      start.wday().upto 6 do |i|
+        return start + (i-start.wday()).days if on_xday(i) 
+      end
+      -1
+    end
+
+
   end
   
 end