1 files changed, 31 insertions, 0 deletions
diff --git a/app/models/concerns/resource_event_tools.rb b/app/models/concerns/resource_event_tools.rb
new file mode 100644
index 00000000000..7226b9573e1
--- /dev/null
+++ b/app/models/concerns/resource_event_tools.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+module ResourceEventTools
+  extend ActiveSupport::Concern
+
+  included do
+    belongs_to :user
+
+    validates :user, presence: { unless: :importing? }, on: :create
+
+    validate :exactly_one_issuable
+
+    scope :created_after, ->(time) { where('created_at > ?', time) }
+  end
+
+  def exactly_one_issuable
+    issuable_count = self.class.issuable_attrs.count { |attr| self["#{attr}_id"] }
+
+    return true if issuable_count == 1
+
+    # if none of issuable IDs is set, check explicitly if nested issuable
+    # object is set, this is used during project import
+    if issuable_count == 0 && importing?
+      issuable_count = self.class.issuable_attrs.count { |attr| self.public_send(attr) } # rubocop:disable GitlabSecurity/PublicSend
+
+      return true if issuable_count == 1
+    end
+
+    errors.add(:base, "Exactly one of #{self.class.issuable_attrs.join(', ')} is required")
+  end
+end