.list-group
  = link_to t('all_categories'), url_for(category_id: nil), class: "list-group-item #{'active' if current_page?(root_path) || current_page?(items_path)}"
  - Category.all.each do |category|
    = link_to category.name, url_for(category_id: category.slug, teacher: params[:teacher]), class: "list-group-item #{'active' if current_page?(items_by_category_path(category_id: category.slug))}"
.list-group
  = link_to t('all_teachers'), url_for(teacher: nil), class: "list-group-item #{'active' if params[:teacher].nil?}"
  - Item.all_teachers_for_locale(I18n.locale).each do |teacher|
    = link_to teacher, url_for(teacher: teacher), class: "list-group-item #{'active' if params[:teacher] == teacher}"