Use ResourceLabelEvent for tracking label changes

6 files changed, 79 insertions, 44 deletions

diff --git a/app/services/issuable/common_system_notes_service.rb b/app/services/issuable/common_system_notes_service.rb
index 028b350ca07..ab53c38aa3a 100644
--- a/app/services/issuable/common_system_notes_service.rb
+++ b/app/services/issuable/common_system_notes_service.rb
@@ -55,7 +55,9 @@ module Issuable
       added_labels = issuable.labels - old_labels
       removed_labels = old_labels - issuable.labels
 
-      SystemNoteService.change_label(issuable, issuable.project, current_user, added_labels, removed_labels)
+      ResourceEvents::ChangeLabelsService
+        .new(issuable, current_user)
+        .execute(added_labels: added_labels, removed_labels: removed_labels)
     end
 
     def create_title_change_note(old_title)
diff --git a/app/services/issues/move_service.rb b/app/services/issues/move_service.rb
index 841bce9949e..c52aa577dd8 100644
--- a/app/services/issues/move_service.rb
+++ b/app/services/issues/move_service.rb
@@ -36,6 +36,7 @@ module Issues
 
     def update_new_issue
       rewrite_notes
+      copy_resource_label_events
       rewrite_issue_award_emoji
       add_note_moved_from
     end
@@ -96,6 +97,18 @@ module Issues
       end
     end
 
+    def copy_resource_label_events
+      @old_issue.resource_label_events.find_in_batches do |batch|
+        events = batch.map do |event|
+          event.attributes
+            .except('id', 'reference', 'reference_html')
+            .merge('issue_id' => @new_issue.id, 'created_at' => event.created_at)
+        end
+
+        Gitlab::Database.bulk_insert(ResourceLabelEvent.table_name, events)
+      end
+    end
+
     def rewrite_issue_award_emoji
       rewrite_award_emoji(@old_issue, @new_issue)
     end
diff --git a/app/services/labels/promote_service.rb b/app/services/labels/promote_service.rb
index 623a5f0950e..fcdcea2d0ea 100644
--- a/app/services/labels/promote_service.rb
+++ b/app/services/labels/promote_service.rb
@@ -13,6 +13,7 @@ module Labels
 
         label_ids_for_merge(new_label).find_in_batches(batch_size: BATCH_SIZE) do |batched_ids|
           update_issuables(new_label, batched_ids)
+          update_resource_label_events(new_label, batched_ids)
           update_issue_board_lists(new_label, batched_ids)
           update_priorities(new_label, batched_ids)
           subscribe_users(new_label, batched_ids)
@@ -52,6 +53,12 @@ module Labels
         .update_all(label_id: new_label)
     end
 
+    def update_resource_label_events(new_label, label_ids)
+      ResourceLabelEvent
+        .where(label: label_ids)
+        .update_all(label_id: new_label)
+    end
+
     def update_issue_board_lists(new_label, label_ids)
       List
         .where(label: label_ids)
diff --git a/app/services/resource_events/change_labels_service.rb b/app/services/resource_events/change_labels_service.rb
index 8edb0ddb3ed..039d6e2ebad 100644
--- a/app/services/resource_events/change_labels_service.rb
+++ b/app/services/resource_events/change_labels_service.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-# This service is not used yet, it will be used for:
-# https://gitlab.com/gitlab-org/gitlab-ce/issues/48483
 module ResourceEvents
   class ChangeLabelsService
     attr_reader :resource, :user
@@ -25,6 +23,7 @@ module ResourceEvents
       end
 
       Gitlab::Database.bulk_insert(ResourceLabelEvent.table_name, labels)
+      resource.expire_note_etag_cache
     end
 
     private
diff --git a/app/services/resource_events/merge_into_notes_service.rb b/app/services/resource_events/merge_into_notes_service.rb
new file mode 100644
index 00000000000..1b02a1602e2
--- /dev/null
+++ b/app/services/resource_events/merge_into_notes_service.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+# We store events about issuable label changes in a separate table (not as
+# other system notes), but we still want to display notes about label changes
+# as classic system notes in UI.  This service generates "synthetic" notes for
+# label event changes and merges them with classic notes and sorts them by
+# creation time.
+
+module ResourceEvents
+  class MergeIntoNotesService
+    include Gitlab::Utils::StrongMemoize
+
+    attr_reader :resource, :current_user, :params
+
+    def initialize(resource, current_user, params = {})
+      @resource = resource
+      @current_user = current_user
+      @params = params
+    end
+
+    def execute(notes = [])
+      (notes + label_notes).sort_by { |n| n.created_at }
+    end
+
+    private
+
+    def label_notes
+      label_events_by_discussion_id.map do |discussion_id, events|
+        LabelNote.from_events(events, resource: resource, resource_parent: resource_parent)
+      end
+    end
+
+    def label_events_by_discussion_id
+      return [] unless resource.respond_to?(:resource_label_events)
+
+      events = resource.resource_label_events.includes(:label, :user)
+      events = since_fetch_at(events)
+
+      events.group_by { |event| event.discussion_id }
+    end
+
+    def since_fetch_at(events)
+      return events unless params[:last_fetched_at].present?
+
+      last_fetched_at = Time.at(params.fetch(:last_fetched_at).to_i)
+      events.created_after(last_fetched_at - NotesFinder::FETCH_OVERLAP)
+    end
+
+    def resource_parent
+      strong_memoize(:resource_parent) do
+        resource.project || resource.group
+      end
+    end
+  end
+end
diff --git a/app/services/system_note_service.rb b/app/services/system_note_service.rb
index dda89830179..3ea81445798 100644
--- a/app/services/system_note_service.rb
+++ b/app/services/system_note_service.rb
@@ -98,47 +98,6 @@ module SystemNoteService
     create_note(NoteSummary.new(issue, project, author, body, action: 'assignee'))
   end
 
-  # Called when one or more labels on a Noteable are added and/or removed
-  #
-  # noteable       - Noteable object
-  # project        - Project owning noteable
-  # author         - User performing the change
-  # added_labels   - Array of Labels added
-  # removed_labels - Array of Labels removed
-  #
-  # Example Note text:
-  #
-  #   "added ~1 and removed ~2 ~3 labels"
-  #
-  #   "added ~4 label"
-  #
-  #   "removed ~5 label"
-  #
-  # Returns the created Note object
-  def change_label(noteable, project, author, added_labels, removed_labels)
-    labels_count = added_labels.count + removed_labels.count
-
-    references     = ->(label) { label.to_reference(format: :id) }
-    added_labels   = added_labels.map(&references).join(' ')
-    removed_labels = removed_labels.map(&references).join(' ')
-
-    text_parts = []
-
-    if added_labels.present?
-      text_parts << "added #{added_labels}"
-      text_parts << 'and' if removed_labels.present?
-    end
-
-    if removed_labels.present?
-      text_parts << "removed #{removed_labels}"
-    end
-
-    text_parts << 'label'.pluralize(labels_count)
-    body = text_parts.join(' ')
-
-    create_note(NoteSummary.new(noteable, project, author, body, action: 'label'))
-  end
-
   # Called when the milestone of a Noteable is changed
   #
   # noteable  - Noteable object