Example of how to approach route containers with groups and sub groups in crystal language (inspired by php frameworks such as Slim Framework 3)

route-container.cr

class Route
  def initialize(@route = "")
  end

  def route
    @route
  end
end

class RouteContainer

  @routes = [] of Route
  @groups = [] of String

  def routes
    @routes
  end

  def add(route : String)
    route = parse_route(route)
    @routes << Route.new route
  end

  def group(route : String, &closure : RouteContainer ->)
    @groups << route
    closure.call(self)
    @groups.pop?
  end

  private def parse_route(route : String)
    
    # remove trailing forward slash from end of each group before joining
    @groups.map!{ |g| g.chomp('/').lchomp('/') }
    group_prefix = @groups.join('/').strip

    route = route.lchomp('/')
    route = group_prefix + "/" + route
    route = "/" + route if !group_prefix.empty?
    
    route

  end
end

container = RouteContainer.new
container.group "/admin", do |router|
  router.group "/users", do |router|
    router.add("/update")
    router.add("/edit")
  end
  router.group "/staff", do |router|
    router.add("/promotion")
  end
end

container.routes.each do |route|
  puts route.route
end