Create an alert when a course announcement is active

Refs MBL-10480

Test Plan:
 - Create a course with an observer linked to a student
 - Create a threshold for that observer-student link in the
   rails console for 'course_announcement' alert type
 - As a teacher create an announcement in the course
 - From the rails console see if an ObserverAlert model
   was created for that observer-student link
 - As a teacher create an announcement that is delayed
   for just a few minutes in the future
 - Once the announcement is active go to the rails console
   and check that there is an ObserverAlert for that
   observer-student link for that announcement (context)

Change-Id: Ia193df0135f314fd3e3f47a17d6fdd59dfb1eb00
Reviewed-on: https://gerrit.instructure.com/149718
Tested-by: Jenkins
Reviewed-by: Cameron Sutter <csutter@instructure.com>
QA-Review: Cameron Sutter <csutter@instructure.com>
Product-Review: Matthew Sessions <msessions@instructure.com>

app/models/announcement.rb

@@ -28,6 +28,7 @@ class Announcement < DiscussionTopic
 
   before_save :infer_content
   before_save :respect_context_lock_rules
+  after_save :create_alert
   validates_presence_of :context_id
   validates_presence_of :context_type
   validates_presence_of :message
@@ -133,4 +134,22 @@ class Announcement < DiscussionTopic
   def assignment
     nil
   end
+
+  def create_alert
+    return if !saved_changes.keys.include?('workflow_state') || saved_changes['workflow_state'][1] != 'active'
+    return if self.context_type != 'Course'
+
+    observers = self.course.enrollments.active.where(type: 'ObserverEnrollment')
+    observers.each do |observer|
+      link = UserObservationLink.active.
+        where(user_id: observer.associated_user_id, observer_id: observer.user_id).first
+
+      threshold = ObserverAlertThreshold.where(user_observation_link: link, alert_type: 'course_announcement').first
+      next if threshold.nil?
+
+      ObserverAlert.create!(user_observation_link: link, observer_alert_threshold: threshold,
+                            context: self, alert_type: 'course_announcement', action_date: self.updated_at,
+                            title: I18n.t("Announcement posted: %{title}", title: self.title))
+    end
+  end
 end

app/models/observer_alert.rb

@@ -18,5 +18,5 @@
 class ObserverAlert < ActiveRecord::Base
   belongs_to :user_observation_link, :inverse_of => :observer_alerts
   belongs_to :observer_alert_threshold, :inverse_of => :observer_alerts
-  belongs_to :context, polymorphic: [:announcement, :assignment, :course, :account_notification]
+  belongs_to :context, polymorphic: [:discussion_topic, :assignment, :course, :account_notification]
 end

spec/models/observer_alert_spec.rb

@@ -39,4 +39,41 @@ describe ObserverAlert do
     expect(saved_alert.user_observation_link).not_to be_nil
     expect(saved_alert.observer_alert_threshold).not_to be_nil
   end
+
+  describe 'course_announcement' do
+    before :once do
+      @course = course_factory()
+      @student = student_in_course(:active_all => true, :course => @course).user
+      @observer = course_with_observer(:course => @course, :associated_user_id => @student.id, :active_all => true).user
+      @link = UserObservationLink.create!(student: @student, observer: @observer, root_account: @account)
+      ObserverAlertThreshold.create!(user_observation_link: @link, alert_type: 'course_announcement')
+
+      # user without a threshold
+      @observer2 = course_with_observer(:course => @course, :associated_user_id => @student.id, :active_all => true).user
+      @link2 = UserObservationLink.create!(student: @student, observer: @observer2, root_account: @account)
+    end
+
+    it 'creates an alert when a user has a threshold for course announcements' do
+      a = announcement_model(:context => @course)
+      alert = ObserverAlert.where(user_observation_link: @link).first
+      expect(alert).not_to be_nil
+      expect(alert.context).to eq a
+      expect(alert.title).to include('Announcement posted: ')
+
+      alert2 = ObserverAlert.where(user_observation_link: @link2).first
+      expect(alert2).to be_nil
+    end
+
+    it 'creates an alert when the delayed announcement becomes active' do
+      a = announcement_model(:context => @course, :delayed_post_at => Time.zone.now, :workflow_state => :post_delayed)
+      alert = ObserverAlert.where(user_observation_link: @link, context: a).first
+      expect(alert).to be_nil
+
+      a.workflow_state = 'active'
+      a.save!
+
+      alert = ObserverAlert.where(user_observation_link: @link, context: a).first
+      expect(alert).not_to be_nil
+    end
+  end
 end