1 files changed, 72 insertions, 0 deletions
diff --git a/app/models/concerns/update_project_statistics.rb b/app/models/concerns/update_project_statistics.rb
new file mode 100644
index 00000000000..1f881249322
--- /dev/null
+++ b/app/models/concerns/update_project_statistics.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+# This module is providing helpers for updating `ProjectStatistics` with `after_save` and `before_destroy` hooks.
+#
+# It deals with `ProjectStatistics.increment_statistic` making sure not to update statistics on a cascade delete from the
+# project, and keeping track of value deltas on each save. It updates the DB only when a change is needed.
+#
+# Example:
+#
+# module Ci
+#   class JobArtifact < ApplicationRecord
+#     include UpdateProjectStatistics
+#
+#     update_project_statistics project_statistics_name: :build_artifacts_size
+#   end
+# end
+#
+# Expectation:
+#
+# - `statistic_attribute` must be an ActiveRecord attribute
+# - The model must implement `project` and `project_id`. i.e. direct Project relationship or delegation
+#
+module UpdateProjectStatistics
+  extend ActiveSupport::Concern
+
+  class_methods do
+    attr_reader :project_statistics_name, :statistic_attribute
+
+    # Configure the model to update `project_statistics_name` on ProjectStatistics,
+    # when `statistic_attribute` changes
+    #
+    # - project_statistics_name: A column of `ProjectStatistics` to update
+    # - statistic_attribute: An attribute of the current model, default to `size`
+    #
+    def update_project_statistics(project_statistics_name:, statistic_attribute: :size)
+      @project_statistics_name = project_statistics_name
+      @statistic_attribute = statistic_attribute
+
+      after_save(:update_project_statistics_after_save, if: :update_project_statistics_attribute_changed?)
+      after_destroy(:update_project_statistics_after_destroy, unless: :project_destroyed?)
+    end
+
+    private :update_project_statistics
+  end
+
+  included do
+    private
+
+    def update_project_statistics_after_save
+      attr = self.class.statistic_attribute
+      delta = read_attribute(attr).to_i - attribute_before_last_save(attr).to_i
+
+      update_project_statistics(delta)
+    end
+
+    def update_project_statistics_attribute_changed?
+      saved_change_to_attribute?(self.class.statistic_attribute)
+    end
+
+    def update_project_statistics_after_destroy
+      update_project_statistics(-read_attribute(self.class.statistic_attribute).to_i)
+    end
+
+    def project_destroyed?
+      project.pending_delete?
+    end
+
+    def update_project_statistics(delta)
+      ProjectStatistics.increment_statistic(project_id, self.class.project_statistics_name, delta)
+    end
+  end
+end