1 files changed, 54 insertions, 0 deletions
diff --git a/lib/gitlab/event_store/event.rb b/lib/gitlab/event_store/event.rb
new file mode 100644
index 00000000000..ee0c329b8e8
--- /dev/null
+++ b/lib/gitlab/event_store/event.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+# An Event object represents a domain event that occurred in a bounded context.
+# By publishing events we notify other bounded contexts about something
+# that happened, so that they can react to it.
+#
+# Define new event classes under `app/events/<namespace>/` with a name
+# representing something that happened in the past:
+#
+#   class Projects::ProjectCreatedEvent < Gitlab::EventStore::Event
+#     def schema
+#       {
+#         'type' => 'object',
+#         'properties' => {
+#           'project_id' => { 'type' => 'integer' }
+#         }
+#       }
+#     end
+#   end
+#
+# To publish it:
+#
+#   Gitlab::EventStore.publish(
+#     Projects::ProjectCreatedEvent.new(data: { project_id: project.id })
+#   )
+#
+module Gitlab
+  module EventStore
+    class Event
+      attr_reader :data
+
+      def initialize(data:)
+        validate_schema!(data)
+        @data = data
+      end
+
+      def schema
+        raise NotImplementedError, 'must specify schema to validate the event'
+      end
+
+      private
+
+      def validate_schema!(data)
+        unless data.is_a?(Hash)
+          raise Gitlab::EventStore::InvalidEvent, "Event data must be a Hash"
+        end
+
+        unless JSONSchemer.schema(schema).valid?(data.deep_stringify_keys)
+          raise Gitlab::EventStore::InvalidEvent, "Data for event #{self.class} does not match the defined schema: #{schema}"
+        end
+      end
+    end
+  end
+end