1 files changed, 72 insertions, 0 deletions
diff --git a/lib/gitlab/cycle_analytics/usage_data.rb b/lib/gitlab/cycle_analytics/usage_data.rb
new file mode 100644
index 00000000000..5122e3417ca
--- /dev/null
+++ b/lib/gitlab/cycle_analytics/usage_data.rb
@@ -0,0 +1,72 @@
+module Gitlab
+  module CycleAnalytics
+    class UsageData
+      PROJECTS_LIMIT = 10
+
+      attr_reader :projects, :options
+
+      def initialize
+        @projects = Project.sorted_by_activity.limit(PROJECTS_LIMIT)
+        @options = { from: 7.days.ago }
+      end
+
+      def to_json
+        total = 0
+
+        values =
+          medians_per_stage.each_with_object({}) do |(stage_name, medians), hsh|
+            calculations = stage_values(medians)
+
+            total += calculations.values.compact.sum
+            hsh[stage_name] = calculations
+          end
+
+        values[:total] = total
+
+        { avg_cycle_analytics: values }
+      end
+
+      private
+
+      def medians_per_stage
+        projects.each_with_object({}) do |project, hsh|
+          ::CycleAnalytics.new(project, options).all_medians_per_stage.each do |stage_name, median|
+            hsh[stage_name] ||= []
+            hsh[stage_name] << median
+          end
+        end
+      end
+
+      def stage_values(medians)
+        medians = medians.map(&:presence).compact
+        average = calc_average(medians)
+
+        {
+          average: average,
+          sd: standard_deviation(medians, average),
+          missing: projects.length - medians.length
+        }
+      end
+
+      def calc_average(values)
+        return if values.empty?
+
+        (values.sum / values.length).to_i
+      end
+
+      def standard_deviation(values, average)
+        Math.sqrt(sample_variance(values, average)).to_i
+      end
+
+      def sample_variance(values, average)
+        return 0 if values.length <= 1
+
+        sum = values.inject(0) do |acc, val|
+          acc + (val - average)**2
+        end
+
+        sum / (values.length - 1)
+      end
+    end
+  end
+end