class ActionDispatch::Routing::RouteSet::CustomUrlHelper

def call(t, args, only_path = false)
  options = args.extract_options!
  url = t.full_url_for(eval_block(t, args, options))
  if only_path
    "/" + url.partition(%r{(?<!/)/(?!/)}).last
  else
    url
  end
end

def eval_block(t, args, options)
  t.instance_exec(*args, merge_defaults(options), &block)
end

def initialize(name, defaults, &block)
  @name = name
  @defaults = defaults
  @block = block
end

def merge_defaults(options)
  defaults ? defaults.merge(options) : options
end