Resource event model

app/models/concerns/label_eventable.rb

+# frozen_string_literal: true
+
+# == LabelEventable concern
+#
+# Contains functionality related to objects that support adding/removing labels.
+#
+# This concern is not used yet, it will be used for:
+# https://gitlab.com/gitlab-org/gitlab-ce/issues/48483
+
+module LabelEventable
+  extend ActiveSupport::Concern
+
+  included do
+    has_many :resource_label_events
+  end
+end

app/models/issue.rb

@@ -12,6 +12,7 @@ class Issue < ActiveRecord::Base
   include TimeTrackable
   include ThrottledTouch
   include IgnorableColumn
+  include LabelEventable
 
   ignore_column :assignee_id, :branch_name, :deleted_at
 

app/models/merge_request.rb

@@ -10,6 +10,7 @@ class MergeRequest < ActiveRecord::Base
   include EachBatch
   include ThrottledTouch
   include Gitlab::Utils::StrongMemoize
+  include LabelEventable
 
   ignore_column :locked_at,
                 :ref_fetched,

app/models/resource_label_event.rb

+# frozen_string_literal: true
+
+# This model is not used yet, it will be used for:
+# https://gitlab.com/gitlab-org/gitlab-ce/issues/48483
+class ResourceLabelEvent < ActiveRecord::Base
+  belongs_to :user
+  belongs_to :issue
+  belongs_to :merge_request
+  belongs_to :label
+
+  validates :user, presence: true, on: :create
+  validates :label, presence: true, on: :create
+  validate :exactly_one_issuable
+
+  enum action: {
+    add: 1,
+    remove: 2
+  }
+
+  def self.issuable_columns
+    %i(issue_id merge_request_id).freeze
+  end
+
+  def issuable
+    issue || merge_request
+  end
+
+  private
+
+  def exactly_one_issuable
+    if self.class.issuable_columns.count { |attr| self[attr] } != 1
+      errors.add(:base, "Exactly one of #{self.class.issuable_columns.join(', ')} is required")
+    end
+  end
+end

app/services/resource_events/change_labels_service.rb

+# 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
+
+    def initialize(resource, user)
+      @resource, @user = resource, user
+    end
+
+    def execute(added_labels: [], removed_labels: [])
+      label_hash = {
+        resource_column(resource) => resource.id,
+        user_id: user.id,
+        created_at: Time.now
+      }
+
+      labels = added_labels.map do |label|
+        label_hash.merge(label_id: label.id, action: ResourceLabelEvent.actions['add'])
+      end
+      labels += removed_labels.map do |label|
+        label_hash.merge(label_id: label.id, action: ResourceLabelEvent.actions['remove'])
+      end
+
+      Gitlab::Database.bulk_insert(ResourceLabelEvent.table_name, labels)
+    end
+
+    private
+
+    def resource_column(resource)
+      case resource
+      when Issue
+        :issue_id
+      when MergeRequest
+        :merge_request_id
+      else
+        raise ArgumentError, "Unknown resource type #{resource.class.name}"
+      end
+    end
+  end
+end

changelogs/unreleased/jprovazn-resource-events.yml

+---
+title: Add new model for tracking label events.
+merge_request:
+author:
+type: added

db/migrate/20180726172057_create_resource_label_events.rb

+# frozen_string_literal: true
+
+class CreateResourceLabelEvents < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    create_table :resource_label_events, id: :bigserial do |t|
+      t.integer :action, null: false
+      t.references :issue, null: true, index: true, foreign_key: { on_delete: :cascade }
+      t.references :merge_request, null: true, index: true, foreign_key: { on_delete: :cascade }
+      t.references :label, index: true, foreign_key: { on_delete: :nullify }
+      t.references :user, index: true, foreign_key: { on_delete: :nullify }
+      t.datetime_with_timezone :created_at, null: false
+    end
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180722103201) do
+ActiveRecord::Schema.define(version: 20180726172057) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -1787,6 +1787,20 @@ ActiveRecord::Schema.define(version: 20180722103201) do
   add_index "remote_mirrors", ["last_successful_update_at"], name: "index_remote_mirrors_on_last_successful_update_at", using: :btree
   add_index "remote_mirrors", ["project_id"], name: "index_remote_mirrors_on_project_id", using: :btree
 
+  create_table "resource_label_events", id: :bigserial, force: :cascade do |t|
+    t.integer "action", null: false
+    t.integer "issue_id"
+    t.integer "merge_request_id"
+    t.integer "label_id"
+    t.integer "user_id"
+    t.datetime_with_timezone "created_at", null: false
+  end
+
+  add_index "resource_label_events", ["issue_id"], name: "index_resource_label_events_on_issue_id", using: :btree
+  add_index "resource_label_events", ["label_id"], name: "index_resource_label_events_on_label_id", using: :btree
+  add_index "resource_label_events", ["merge_request_id"], name: "index_resource_label_events_on_merge_request_id", using: :btree
+  add_index "resource_label_events", ["user_id"], name: "index_resource_label_events_on_user_id", using: :btree
+
   create_table "routes", force: :cascade do |t|
     t.integer "source_id", null: false
     t.string "source_type", null: false
@@ -2337,6 +2351,10 @@ ActiveRecord::Schema.define(version: 20180722103201) do
   add_foreign_key "push_event_payloads", "events", name: "fk_36c74129da", on_delete: :cascade
   add_foreign_key "releases", "projects", name: "fk_47fe2a0596", on_delete: :cascade
   add_foreign_key "remote_mirrors", "projects", on_delete: :cascade
+  add_foreign_key "resource_label_events", "issues", on_delete: :cascade
+  add_foreign_key "resource_label_events", "labels", on_delete: :nullify
+  add_foreign_key "resource_label_events", "merge_requests", on_delete: :cascade
+  add_foreign_key "resource_label_events", "users", on_delete: :nullify
   add_foreign_key "services", "projects", name: "fk_71cce407f9", on_delete: :cascade
   add_foreign_key "snippets", "projects", name: "fk_be41fd4bb7", on_delete: :cascade
   add_foreign_key "subscriptions", "projects", on_delete: :cascade

spec/factories/resource_label_events.rb

+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :resource_label_event do
+    user { issue.project.creator }
+    action :add
+    label
+    issue
+  end
+end

spec/lib/gitlab/import_export/all_models.yml

@@ -7,6 +7,7 @@ issues:
 - updated_by
 - milestone
 - notes
+- resource_label_events
 - label_links
 - labels
 - last_edited_by
@@ -76,6 +77,7 @@ merge_requests:
 - updated_by
 - milestone
 - notes
+- resource_label_events
 - label_links
 - labels
 - last_edited_by

spec/models/resource_label_event_spec.rb

+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe ResourceLabelEvent, type: :model do
+  subject { build(:resource_label_event) }
+  let(:issue) { create(:issue) }
+  let(:merge_request) { create(:merge_request) }
+
+  describe 'associations' do
+    it { is_expected.to belong_to(:user) }
+    it { is_expected.to belong_to(:issue) }
+    it { is_expected.to belong_to(:merge_request) }
+    it { is_expected.to belong_to(:label) }
+  end
+
+  describe 'validations' do
+    it { is_expected.to be_valid }
+    it { is_expected.to validate_presence_of(:label) }
+    it { is_expected.to validate_presence_of(:user) }
+
+    describe 'Issuable validation' do
+      it 'is invalid if issue_id and merge_request_id are missing' do
+        subject.attributes = { issue: nil, merge_request: nil }
+
+        expect(subject).to be_invalid
+      end
+
+      it 'is invalid if issue_id and merge_request_id are set' do
+        subject.attributes = { issue: issue, merge_request: merge_request }
+
+        expect(subject).to be_invalid
+      end
+
+      it 'is valid if only issue_id is set' do
+        subject.attributes = { issue: issue, merge_request: nil }
+
+        expect(subject).to be_valid
+      end
+
+      it 'is valid if only merge_request_id is set' do
+        subject.attributes = { merge_request: merge_request, issue: nil }
+
+        expect(subject).to be_valid
+      end
+    end
+  end
+end

spec/services/resource_events/change_labels_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe ResourceEvents::ChangeLabelsService do
+  set(:project)  { create(:project) }
+  set(:author)   { create(:user) }
+  let(:resource) { create(:issue, project: project) }
+
+  describe '.change_labels' do
+    subject { described_class.new(resource, author).execute(added_labels: added, removed_labels: removed) }
+
+    let(:labels)  { create_list(:label, 2, project: project) }
+
+    def expect_label_event(event, label, action)
+      expect(event.user).to eq(author)
+      expect(event.label).to eq(label)
+      expect(event.action).to eq(action)
+    end
+
+    context 'when adding a label' do
+      let(:added)   { [labels[0]] }
+      let(:removed) { [] }
+
+      it 'creates new label event' do
+        expect { subject }.to change { resource.resource_label_events.count }.from(0).to(1)
+
+        expect_label_event(resource.resource_label_events.first, labels[0], 'add')
+      end
+    end
+
+    context 'when removing a label' do
+      let(:added)   { [] }
+      let(:removed) { [labels[1]] }
+
+      it 'creates new label event' do
+        expect { subject }.to change { resource.resource_label_events.count }.from(0).to(1)
+
+        expect_label_event(resource.resource_label_events.first, labels[1], 'remove')
+      end
+    end
+
+    context 'when both adding and removing labels' do
+      let(:added)   { [labels[0]] }
+      let(:removed) { [labels[1]] }
+
+      it 'creates all label events in a single query' do
+        expect(Gitlab::Database).to receive(:bulk_insert).once.and_call_original
+        expect { subject }.to change { resource.resource_label_events.count }.from(0).to(2)
+      end
+    end
+  end
+end