Update UpdateTimeslicesCourseDate class to support drastic changes in…

… course dates. Now when the previous course period and the current one have no overlap, delete the existing timeslices and generate new ones. Add basic specs for it. (#6185)

app/services/update_timeslices_course_date.rb

@@ -12,12 +12,28 @@ def initialize(course)
   end
 
   def run
+    update_timeslices_if_drastic_change
     update_timeslices_if_start_date_changed
     update_timeslices_if_end_date_changed
   end
 
   private
 
+  # A 'drastic' change occurs when the previous course period and the current one have no overlap.
+  # In this case, we delete the existing timeslices and generate new ones.
+  def update_timeslices_if_drastic_change
+    min_course_start = CourseWikiTimeslice.where(course: @course).minimum(:start)
+    max_course_end = CourseWikiTimeslice.where(course: @course).maximum(:end)
+
+    drastic_change = @course.start >= max_course_end || @course.end <= min_course_start
+
+    return unless drastic_change
+
+    remove_timeslices_prior_to_start_date
+    remove_timeslices_after_end_date
+    @timeslice_manager.create_timeslices_for_new_course_wiki_records(@course.wikis)
+  end
+
   def update_timeslices_if_start_date_changed
     # Get the min course wiki timeslice end date
     min_course_end = CourseWikiTimeslice.where(course: @course)

spec/services/update_timeslices_course_date_spec.rb

@@ -4,7 +4,7 @@
 
 describe UpdateTimeslicesCourseDate do
   let(:start) { '2021-01-24'.to_datetime }
-  let(:course) { create(:course, start: '2021-01-24', end: '2021-01-30') }
+  let(:course) { create(:course, start:, end: '2021-01-30') }
   let(:enwiki) { Wiki.get_or_create(language: 'en', project: 'wikipedia') }
   let(:updater) { described_class.new(course).run }
   let(:user1) { create(:user, username: 'Ragesoss') }
@@ -127,4 +127,48 @@
       expect(course.article_course_timeslices.count).to eq(1)
     end
   end
+
+  context 'when the course was entirely moved backward' do
+    before do
+      course.update(start: '2020-02-10')
+      course.update(end: '2020-02-20')
+    end
+
+    it 'deletes existing timeslices and create new ones' do
+      # There are two users, two articles and one wiki
+      expect(course.course_wiki_timeslices.count).to eq(7)
+      expect(course.course_wiki_timeslices.needs_update.count).to eq(0)
+      expect(course.course_user_wiki_timeslices.count).to eq(3)
+      expect(course.article_course_timeslices.count).to eq(2)
+
+      described_class.new(course).run
+      # Timeslices from old period were deleted and new ones were created
+      expect(course.course_wiki_timeslices.count).to eq(11)
+      expect(course.course_wiki_timeslices.needs_update.count).to eq(0)
+      expect(course.course_user_wiki_timeslices.count).to eq(0)
+      expect(course.article_course_timeslices.count).to eq(0)
+    end
+  end
+
+  context 'when the course was entirely moved forward' do
+    before do
+      course.update(start: '2022-02-10')
+      course.update(end: '2022-02-20')
+    end
+
+    it 'deletes existing timeslices and create new ones' do
+      # There are two users, two articles and one wiki
+      expect(course.course_wiki_timeslices.count).to eq(7)
+      expect(course.course_wiki_timeslices.needs_update.count).to eq(0)
+      expect(course.course_user_wiki_timeslices.count).to eq(3)
+      expect(course.article_course_timeslices.count).to eq(2)
+
+      described_class.new(course).run
+      # Timeslices from old period were deleted and new ones were created
+      expect(course.course_wiki_timeslices.count).to eq(11)
+      expect(course.course_wiki_timeslices.needs_update.count).to eq(0)
+      expect(course.course_user_wiki_timeslices.count).to eq(0)
+      expect(course.article_course_timeslices.count).to eq(0)
+    end
+  end
 end