Compare/sort grades

lib/cryptcheck/grade.rb

@@ -1,6 +1,6 @@
 module CryptCheck
   module Grade
-    GRADES        = %i(A+ A B+ B C+ C D E F G V T X)
+    GRADES        = %i(A+ A B+ B C+ C D E F G V T X).freeze
     GRADE_STATUS  = {
       :'A+' => :best,
       A:    :best,
@@ -16,7 +16,7 @@ module CryptCheck
       V:    :critical,
       T:    :critical,
       X:    :critical
-    }
+    }.freeze
     STATUS_GRADES = {
       critical: :G,
       error:    :F,
@@ -25,7 +25,7 @@ module CryptCheck
       good:     :C,
       great:    :B,
       best:     :A
-    }
+    }.freeze
 
     def grade
       @grade ||= calculate_grade
@@ -34,5 +34,21 @@ module CryptCheck
     def grade_status
       GRADE_STATUS.fetch self.grade, :unknown
     end
+
+    def self.compare(a, b)
+      GRADES.index(a.to_sym) <=> GRADES.index(b.to_sym)
+    end
+
+    def self.sort(grades)
+      grades.sort &self.method(:compare)
+    end
+
+    def self.better(grades)
+      self.sort(grades).first
+    end
+
+    def self.worst(grades)
+      self.sort(grades).last
+    end
   end
 end