Idea for plain dumb navigation active state

application.html.haml

%body
  %nav.main
    %ul
      %li= link_to 'main 1', some_path, class: active_navigation_item?(:main) # => true
      %li= link_to 'main 2', some_path, class: active_navigation_item?(:more) # => false
  = yield

navigation_helper.rb

module NavigationHelper
  # set active navigation item state
  def active_nagigation_item(*hierarchy)
    ...
  end
  # get active navigation item state
  def active_navigation_item?(*hierarchy)
    ...
  end
end

view.html.haml

- active_navigation_item :main, :second

%nav.second
  %ul
    %li= link_to 'second 1', another_path, class: active_navigation_item?(:main, :second) # => true
    %li= link_to 'second 2', another_path, class: active_navigation_item?(:main, :less) # => false

.content
  Lorem