Destroy talk media upon user deletion

app/models/user.rb

@@ -99,6 +99,11 @@ class User < ApplicationRecord
   after_create :set_consented_at
   before_destroy :destroy_single_submissions, prepend: true
 
+  attr_accessor :skip_destroy_talk_media
+
+  before_destroy :destroy_talk_media_upon_user_deletion, prepend: true,
+                                                         unless: :skip_destroy_talk_media
+
   # users can comment stuff
   acts_as_commontator
 
@@ -704,6 +709,7 @@ def archive_and_destroy(archive_name)
       success = transfer_contributions_to(archive_user(archive_name))
       return false unless success
     end
+    self.skip_destroy_talk_media = true
     destroy
   end
 
@@ -826,6 +832,17 @@ def destroy_single_submissions
                                       .map(&:id)).destroy_all
     end
 
+    # Destroys all talk media of the user.
+    # If the user is an editor of media other than talk-related media,
+    # nothing will happen.
+    def destroy_talk_media_upon_user_deletion
+      return if edited_media.where.not(teachable_type: "Talk").any?
+
+      # Only delete media where the user is the sole editor.
+      sole_editor_media = edited_media.select { |m| m.editors.count == 1 }
+      Medium.where(id: sole_editor_media.pluck(:id)).destroy_all
+    end
+
     def archive_email
       splitting = DefaultSetting::PROJECT_EMAIL.split("@")
       "#{splitting.first}-archive-#{id}@#{splitting.second}"

spec/models/user_spec.rb

@@ -99,4 +99,69 @@
   #     end
   #   end
   # end
+
+  describe("#destroy_talk_media") do
+    let(:medium) do
+      medium = FactoryBot.build(:medium)
+      medium.teachable_type = "Lecture"
+      medium.save(validate: false)
+      medium
+    end
+
+    let(:medium_talk) do
+      medium = FactoryBot.build(:medium)
+      medium.teachable_type = "Talk"
+      medium.save(validate: false)
+      medium
+    end
+
+    context("when user is destroyed") do
+      it("method is called") do
+        user = FactoryBot.create(:confirmed_user)
+        expect(user).to receive(:destroy_talk_media_upon_user_deletion)
+        user.destroy
+      end
+
+      context("when user self-deletes (archive & destroy)") do
+        it("method is not called") do
+          user = FactoryBot.create(:confirmed_user)
+          expect(user).not_to receive(:destroy_talk_media_upon_user_deletion)
+          user.archive_and_destroy("dummy archive user name")
+        end
+      end
+    end
+
+    context("when user has media other than talk media") do
+      it("does not destroy any media") do
+        user = FactoryBot.create(:confirmed_user)
+        medium
+        medium_talk
+
+        # use .send(:...) to access private method
+        expect { user.send(:destroy_talk_media_upon_user_deletion) }
+          .not_to(change { Medium.count })
+      end
+    end
+
+    context("when user has only talk media") do
+      it("does not destroy talk media that has multiple editors") do
+        user = FactoryBot.create(:confirmed_user)
+        user2 = FactoryBot.create(:confirmed_user)
+        medium_talk.editors << user
+        medium_talk.editors << user2
+
+        expect { user.send(:destroy_talk_media_upon_user_deletion) }
+          .not_to(change { Medium.count })
+      end
+
+      it("destroys talk media that has only one editor") do
+        user = FactoryBot.create(:confirmed_user)
+        medium_talk.editors << user
+
+        expect { user.send(:destroy_talk_media_upon_user_deletion) }
+          .to(change { Medium.count }.by(-1)
+          .and(change { Medium.exists?(medium_talk.id) }.from(true).to(false)))
+      end
+    end
+  end
 end