1 files changed, 32 insertions, 0 deletions
diff --git a/lib/gitlab/metrics/delta.rb b/lib/gitlab/metrics/delta.rb
new file mode 100644
index 00000000000..bcf28eed84d
--- /dev/null
+++ b/lib/gitlab/metrics/delta.rb
@@ -0,0 +1,32 @@
+module Gitlab
+  module Metrics
+    # Class for calculating the difference between two numeric values.
+    #
+    # Every call to `compared_with` updates the internal value. This makes it
+    # possible to use a single Delta instance to calculate the delta over time
+    # of an ever increasing number.
+    #
+    # Example usage:
+    #
+    #     delta = Delta.new(0)
+    #
+    #     delta.compared_with(10) # => 10
+    #     delta.compared_with(15) # => 5
+    #     delta.compared_with(20) # => 5
+    class Delta
+      def initialize(value = 0)
+        @value = value
+      end
+
+      # new_value - The value to compare with as a Numeric.
+      #
+      # Returns a new Numeric (depending on the type of `new_value`).
+      def compared_with(new_value)
+        delta  = new_value - @value
+        @value = new_value
+
+        delta
+      end
+    end
+  end
+end