Add course exclusivity rules

Add exclusivity groups to course editions. If there are two course editions with the same exclusivity group, then a student can only enrol in one of them.

An explanatory message is shown and the button will be disabled for other courses where they try to enrol.

Adding exclusivity groups can be done by typing a new group name, or by selecting one of the existing groups from the suggestion list. Exclusivity groups are automatically deleted if there are no course editions in them.

Closes #80 (closed)

app/controllers/admin/course_editions_controller.rb

@@ -34,8 +34,13 @@ module Admin
       @course_edition = CourseEdition.create(
         course_edition_params.merge(course: @course)
       )
+
       if @course_edition.persisted?
-        flash[:success] = 'Succesfully created course edition'
+        if update_exclusivity_groups.empty?
+          flash[:success] = 'Successfully created course edition'
+        else
+          flash[:danger] = 'Course edition was created, but exclusivity groups could not be set'
+        end
         redirect_to admin_course_edition_url(@course, @course_edition)
       else
         flash[:danger] = 'Failed to create course edition'
@@ -49,8 +54,8 @@ module Admin
     end
 
     def update
-      if @course_edition.update(course_edition_params)
-        flash[:success] = 'Succesfully updated course edition'
+      if @course_edition.update(course_edition_params) && update_exclusivity_groups.empty?
+        flash[:success] = 'Successfully updated course edition'
         redirect_to admin_course_edition_url(@course, @course_edition)
       else
         flash[:danger] = 'Failed to update course edition'
@@ -128,9 +133,36 @@ module Admin
       )
     end
 
+    def course_edition_params_with_exclusivity_groups
+      params.require(:course_edition).permit(
+        course_edition_params_keys + [exclusivity_groups: %i[id name _destroy]]
+      )
+    end
+
     def load_configuration
       @course_edition.configuration ||= CourseConfiguration.new
       @configuration = @course_edition.configuration
     end
+
+    def update_exclusivity_groups
+      failed = []
+      groups_params = course_edition_params_with_exclusivity_groups[:exclusivity_groups] || {}
+      groups_params.each do |id, group_params|
+        current = CourseEditionExclusivityGroup.where(course_edition: @course_edition).find_by(exclusivity_group_id: id)
+        if group_params[:_destroy].to_s == '1'
+          # Ignore if this currently does not exist
+          current&.destroy
+        elsif group_params[:id].nil? # New exclusivity group
+          current&.destroy
+          exclusivity_group = ExclusivityGroup.find_by(name: group_params[:name]) || ExclusivityGroup.create(name: group_params[:name])
+          @course_edition.exclusivity_groups << exclusivity_group
+        elsif group_params[:id] != id # Modified exclusivity group
+          failed << id if current.nil? # Record failure if not found
+          current&.destroy
+          @course_edition.exclusivity_groups.create(name: group_params[:name])
+        end
+      end
+      failed
+    end
   end
 end