Rails conditional controller

slug_rack_app.rb

# routes.rb (very bottom route):

match '*path' => SlugRackApp


# slug_rack_app.rb

class SlugRackApp
  def self.call(env)
    path = env["action_dispatch.request.path_parameters"][:path]

    query_params = if env["QUERY_STRING"]
      Rack::Utils.parse_nested_query(env["QUERY_STRING"]).with_indifferent_access
    else
      {}
    end

    # here you need to find the controller/action according to a condition (using data in params)
    controller = ArticlesController
    action = :show
    
    # you can manipulate params and put it back on the env, Rails middlewares will convert it back to params in your controller
    article = Article.find_by_slug(query_params[:slug])
    query_params[:id] = article.id

    env["QUERY_STRING"] = query_params.to_query
    
    response = controller.action(action).call(env)
    
    response
  end
end