class ActionDispatch::Journey::Path::Pattern::RegexpOffsets

def initialize(matchers)
  @matchers      = matchers
  @capture_count = [0]
end

def visit(node)
  super
  @capture_count
end

def visit_SYMBOL(node)
  node = node.to_sym
  if @matchers.key?(node)
    re = /#{@matchers[node]}|/
    @capture_count.push((re.match('').length - 1) + (@capture_count.last || 0))
  else
    @capture_count << (@capture_count.last || 0)
  end
end