From 42a3448391bcf637a6d35ec20af009ae38e522cf Mon Sep 17 00:00:00 2001
From: Gabina Luz Bianchi <gabinaluz@gmail.com>
Date: Fri, 7 Feb 2025 16:56:27 -0300
Subject: [PATCH] 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 | 16 +++++++
 .../update_timeslices_course_date_spec.rb     | 46 ++++++++++++++++++-
 2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/app/services/update_timeslices_course_date.rb b/app/services/update_timeslices_course_date.rb
index 2f0be6364e..e2e942ab46 100644
--- a/app/services/update_timeslices_course_date.rb
+++ b/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)
diff --git a/spec/services/update_timeslices_course_date_spec.rb b/spec/services/update_timeslices_course_date_spec.rb
index 9dec4845d3..843cd092b4 100644
--- a/spec/services/update_timeslices_course_date_spec.rb
+++ b/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