osem/app/controllers/admin/difficulty_levels_controller.rb

module Admin
  class DifficultyLevelsController < Admin::BaseController
    load_and_authorize_resource :conference, find_by: :short_title
    authorize_resource through: :conference

    def index
      authorize! :index, DifficultyLevel.new(conference_id: @conference.id)
    end

    def update
      if @conference.update_attributes(params[:conference])
        if !(@conference.difficulty_levels.count > 0) && @conference.use_difficulty_levels == true
          begin
            @conference.use_difficulty_levels = false
            @conference.save!
            flash[:error] = 'You cannot enable the usage of difficulty levels without having set any levels.'
            redirect_to(admin_conference_difficulty_levels_path(conference_id: @conference.short_title))
          rescue ActiveRecord::RecordInvalid
            flash[:error] = 'Something went wrong. Difficulty Levels update failed.'
            redirect_to(admin_conference_difficulty_levels_path(conference_id: @conference.short_title))
          end
        else
          flash[:notice] = 'Difficulty Levels were successfully updated.'
          redirect_to(admin_conference_difficulty_levels_path(conference_id: @conference.short_title))
        end
      else
        flash[:error] = 'Difficulty Levels update failed.'
        redirect_to(admin_conference_difficulty_levels_path(conference_id: @conference.short_title))
      end
    end
  end
end