move model validation into pattern classes and link from recurring_todo model

app/models/recurring_todos/yearly_repeat_pattern.rb

@@ -6,6 +6,47 @@ module RecurringTodos
       super user
     end
 
+    def recurrence_selector
+      get :recurrence_selector
+    end
+
+    def month_of_year
+      get :every_other2
+    end
+
+    def every_x_day
+      get :every_other1
+    end
+
+    def every_xth_day
+      get :every_other3
+    end
+
+    def day_of_week
+      get :every_count
+    end
+
+    def month_of_year2
+      # if recurrence pattern is every xth day in a month, return month otherwise
+      # return a default value
+      get(:recurrence_selector) == 1 ? get(:every_other2) : Time.zone.now.month
+    end
+
+    def validate
+      super
+      case recurrence_selector
+      when 0 # 'yearly_every_x_day'
+        errors[:base] << "The month of the year may not be empty for recurrence setting" if month_of_year.blank?
+        errors[:base] << "The day of the month may not be empty for recurrence setting" if every_x_day.blank?
+      when 1 # 'yearly_every_xth_day'
+        errors[:base] << "The month of the year may not be empty for recurrence setting" if month_of_year2.blank?
+        errors[:base] << "The nth day of the month may not be empty for recurrence setting" if every_xth_day.blank?
+        errors[:base] << "The day of the week may not be empty for recurrence setting" if day_of_week.blank?
+      else
+        raise "unexpected value of recurrence selector '#{recurrence_selector}'"
+      end      
+    end
+
   end
   
 end