assignation.rb

  # POST
  def check_assignation
    @inventory_ids = params[:inv]
    @inventories = OleCore::Inventory.includes(:course, account: {subscription: :subscription_plan})
                                     .where(id: params[:inv])
    
    prevent_empty_trainees_and_courses
    
    # If this assignation doesn't require addons, no confirmation required either.
    if !CourseAssigner.requires_addons?(@inventories, @checked_users, current_user)
      @confirmation = OpenStruct.new(needs_confirmation: false)
      return
    end

    user_count = User.outside_subscription.where(login_id: @checked_users).count
    new_price  = current_subscription.price_for_extra_users(user_count)
    if new_price > 0
      @confirmation = OpenStruct.new(needs_confirmation: true, extra_amount: new_price)
    else
      @confirmation = OpenStruct.new(needs_confirmation: false)
    end
    
  rescue AllocateException => e
    flash.now[:alert] = e.to_s
  end

  private

  def prevent_empty_trainees_and_courses
    raise AllocateException.new t(:please_select_at_least_one_course_and_one_trainee) if @inventories.empty? && @checked_users.nil?
    raise AllocateException.new t(:please_select_at_least_one_course_to_assign) if @inventories.empty?
    raise AllocateException.new t(:please_select_at_least_one_trainee_to_assign_units_to) if @checked_users.nil?
  end