1 files changed, 31 insertions, 0 deletions
diff --git a/lib/gitlab/email/handler/create_note_handler.rb b/lib/gitlab/email/handler/create_note_handler.rb
index 7daa1bb96a1..817956831e3 100644
--- a/lib/gitlab/email/handler/create_note_handler.rb
+++ b/lib/gitlab/email/handler/create_note_handler.rb
@@ -33,6 +33,8 @@ module Gitlab
             record: create_note,
             invalid_exception: InvalidNoteError,
             record_name: 'comment')
+
+          reopen_issue_on_external_participant_note
         end
 
         def metrics_event
@@ -71,6 +73,35 @@ module Gitlab
 
           raise UserNotFoundError unless from_address && author.verified_email?(from_address)
         end
+
+        def reopen_issue_on_external_participant_note
+          return unless noteable.respond_to?(:closed?)
+          return unless noteable.closed?
+          return unless author == Users::Internal.support_bot
+          return unless project.service_desk_setting&.reopen_issue_on_external_participant_note?
+
+          ::Notes::CreateService.new(
+            project,
+            Users::Internal.support_bot,
+            noteable: noteable,
+            note: build_reopen_message,
+            confidential: true
+          ).execute
+        end
+
+        def build_reopen_message
+          translated_text = s_(
+            "ServiceDesk|This issue has been reopened because it received a new comment from an external participant."
+          )
+
+          "#{assignees_references} :wave: #{translated_text}\n/reopen".lstrip
+        end
+
+        def assignees_references
+          return unless noteable.assignees.any?
+
+          noteable.assignees.map(&:to_reference).join(' ')
+        end
       end
     end
   end