Add table and model for `zoom_meetings`

Add Active Record backed class `ZoomMeeting`s to persist and validate
zoom links associated to an issue. We also associate meetings to a
project (via project_id) to avoid table joins. `ZoomMeeting`s can have
an issue_status of `added` or `removed` which will be used to show or
hide the zoom link on an issue via quick actions.

app/models/zoom_meeting.rb

+# frozen_string_literal: true
+
+class ZoomMeeting < ApplicationRecord
+  belongs_to :project, optional: false
+  belongs_to :issue, optional: false
+
+  validates :url, presence: true, length: { maximum: 255 }, zoom_url: true
+  validates :issue, same_project_association: true
+
+  enum issue_status: {
+    added: 1,
+    removed: 2
+  }
+
+  scope :added_to_issue, -> { where(issue_status: :added) }
+  scope :removed_from_issue, -> { where(issue_status: :removed) }
+end

app/validators/same_project_association_validator.rb

+# frozen_string_literal: true
+
+# SameProjectAssociationValidator
+#
+# Custom validator to validate that the same project associated with
+# the record is also associated with the value
+#
+# Example:
+# class ZoomMeeting < ApplicationRecord
+#   belongs_to :project, optional: false
+#   belongs_to :issue, optional: false
+
+#   validates :issue, same_project_association: true
+# end
+class SameProjectAssociationValidator < ActiveModel::EachValidator
+  def validate_each(record, attribute, value)
+    return if record.project == value&.project
+
+    record.errors[attribute] << 'must associate the same project'
+  end
+end

app/validators/zoom_url_validator.rb

+# frozen_string_literal: true
+
+# ZoomUrlValidator
+#
+# Custom validator for zoom urls
+#
+class ZoomUrlValidator < ActiveModel::EachValidator
+  def validate_each(record, attribute, value)
+    return if Gitlab::ZoomLinkExtractor.new(value).links.size == 1
+
+    record.errors.add(:url, 'must contain one valid Zoom URL')
+  end
+end

db/migrate/20190930153535_create_zoom_meetings.rb

+# frozen_string_literal: true
+
+class CreateZoomMeetings < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  ZOOM_MEETING_STATUS_ADDED = 1
+
+  def change
+    create_table :zoom_meetings do |t|
+      t.references :project, foreign_key: { on_delete: :cascade },
+        null: false
+      t.references :issue, foreign_key: { on_delete: :cascade },
+        null: false
+      t.timestamps_with_timezone null: false
+      t.integer :issue_status, limit: 2, default: 1, null: false
+      t.string :url, limit: 255
+
+      t.index [:issue_id, :issue_status], unique: true,
+        where: "issue_status = #{ZOOM_MEETING_STATUS_ADDED}"
+    end
+  end
+end

db/schema.rb

@@ -3992,6 +3992,18 @@ ActiveRecord::Schema.define(version: 2019_10_16_220135) do
     t.index ["type"], name: "index_web_hooks_on_type"
   end
 
+  create_table "zoom_meetings", force: :cascade do |t|
+    t.bigint "project_id", null: false
+    t.bigint "issue_id", null: false
+    t.datetime_with_timezone "created_at", null: false
+    t.datetime_with_timezone "updated_at", null: false
+    t.integer "issue_status", limit: 2, default: 1, null: false
+    t.string "url", limit: 255
+    t.index ["issue_id", "issue_status"], name: "index_zoom_meetings_on_issue_id_and_issue_status", unique: true, where: "(issue_status = 1)"
+    t.index ["issue_id"], name: "index_zoom_meetings_on_issue_id"
+    t.index ["project_id"], name: "index_zoom_meetings_on_project_id"
+  end
+
   add_foreign_key "alerts_service_data", "services", on_delete: :cascade
   add_foreign_key "allowed_email_domains", "namespaces", column: "group_id", on_delete: :cascade
   add_foreign_key "analytics_cycle_analytics_group_stages", "labels", column: "end_event_label_id", on_delete: :cascade
@@ -4406,4 +4418,6 @@ ActiveRecord::Schema.define(version: 2019_10_16_220135) do
   add_foreign_key "vulnerability_scanners", "projects", on_delete: :cascade
   add_foreign_key "web_hook_logs", "web_hooks", on_delete: :cascade
   add_foreign_key "web_hooks", "projects", name: "fk_0c8ca6d9d1", on_delete: :cascade
+  add_foreign_key "zoom_meetings", "issues", on_delete: :cascade
+  add_foreign_key "zoom_meetings", "projects", on_delete: :cascade
 end

spec/factories/zoom_meetings.rb

+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :zoom_meeting do
+    project { issue.project }
+    issue
+    url { 'https://zoom.us/j/123456789' }
+    issue_status { :added }
+
+    trait :added_to_issue do
+      issue_status { :added }
+    end
+
+    trait :removed_from_issue do
+      issue_status { :removed }
+    end
+  end
+end

spec/models/zoom_meeting_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe ZoomMeeting do
+  let(:project) { build(:project) }
+
+  describe 'Factory' do
+    subject { build(:zoom_meeting) }
+
+    it { is_expected.to be_valid }
+  end
+
+  describe 'Associations' do
+    it { is_expected.to belong_to(:project).required }
+    it { is_expected.to belong_to(:issue).required }
+  end
+
+  describe 'scopes' do
+    let(:issue) { create(:issue, project: project) }
+    let!(:added_meeting) { create(:zoom_meeting, :added_to_issue, issue: issue) }
+    let!(:removed_meeting) { create(:zoom_meeting, :removed_from_issue, issue: issue) }
+
+    describe '.added_to_issue' do
+      it 'gets only added meetings' do
+        meetings_added = described_class.added_to_issue.pluck(:id)
+
+        expect(meetings_added).to include(added_meeting.id)
+        expect(meetings_added).not_to include(removed_meeting.id)
+      end
+    end
+    describe '.removed_from_issue' do
+      it 'gets only removed meetings' do
+        meetings_removed = described_class.removed_from_issue.pluck(:id)
+
+        expect(meetings_removed).to include(removed_meeting.id)
+        expect(meetings_removed).not_to include(added_meeting.id)
+      end
+    end
+  end
+
+  describe 'Validations' do
+    describe 'url' do
+      it { is_expected.to validate_presence_of(:url) }
+      it { is_expected.to validate_length_of(:url).is_at_most(255) }
+
+      shared_examples 'invalid Zoom URL' do
+        it do
+          expect(subject).to be_invalid
+          expect(subject.errors[:url])
+            .to contain_exactly('must contain one valid Zoom URL')
+        end
+      end
+
+      context 'with non-Zoom URL' do
+        before do
+          subject.url = %{https://non-zoom.url}
+        end
+
+        include_examples 'invalid Zoom URL'
+      end
+
+      context 'with multiple Zoom-URLs' do
+        before do
+          subject.url = %{https://zoom.us/j/123 https://zoom.us/j/456}
+        end
+
+        include_examples 'invalid Zoom URL'
+      end
+    end
+
+    describe 'issue association' do
+      let(:issue) { build(:issue, project: project) }
+
+      subject { build(:zoom_meeting, project: project, issue: issue) }
+
+      context 'for the same project' do
+        it { is_expected.to be_valid }
+      end
+
+      context 'for a different project' do
+        let(:issue) { build(:issue) }
+
+        it do
+          expect(subject).to be_invalid
+          expect(subject.errors[:issue])
+            .to contain_exactly('must associate the same project')
+        end
+      end
+    end
+  end
+
+  describe 'limit number of meetings per issue' do
+    shared_examples 'can add meetings' do
+      it 'can add new Zoom meetings' do
+        create(:zoom_meeting, :added_to_issue, issue: issue)
+      end
+    end
+
+    shared_examples 'can remove meetings' do
+      it 'can remove Zoom meetings' do
+        create(:zoom_meeting, :removed_from_issue, issue: issue)
+      end
+    end
+
+    shared_examples 'cannot add meetings' do
+      it 'fails to add a new meeting' do
+        expect do
+          create(:zoom_meeting, :added_to_issue, issue: issue)
+        end.to raise_error ActiveRecord::RecordNotUnique
+      end
+    end
+
+    let(:issue) { create(:issue, project: project) }
+
+    context 'without meetings' do
+      it_behaves_like 'can add meetings'
+    end
+
+    context 'when no other meeting is added' do
+      before do
+        create(:zoom_meeting, :removed_from_issue, issue: issue)
+      end
+
+      it_behaves_like 'can add meetings'
+    end
+
+    context 'when meeting is added' do
+      before do
+        create(:zoom_meeting, :added_to_issue, issue: issue)
+      end
+
+      it_behaves_like 'cannot add meetings'
+    end
+
+    context 'when meeting is added to another issue' do
+      let(:another_issue) { create(:issue, project: project) }
+
+      before do
+        create(:zoom_meeting, :added_to_issue, issue: another_issue)
+      end
+
+      it_behaves_like 'can add meetings'
+    end
+
+    context 'when second meeting is removed' do
+      before do
+        create(:zoom_meeting, :removed_from_issue, issue: issue)
+      end
+
+      it_behaves_like 'can remove meetings'
+    end
+  end
+end