class ActionDispatch::MiddlewareStack

def [](i)
  middlewares[i]
end

def assert_index(index, where)
  i = index.is_a?(Integer) ? index : middlewares.index(index)
  raise "No such middleware to insert #{where}: #{index.inspect}" unless i
  i
end

def build(app = nil, &block)
  app ||= block
  raise "MiddlewareStack#build requires an app" unless app
  middlewares.reverse.inject(app) { |a, e| e.build(a) }
end

def delete(target)
  middlewares.delete target
end

def each
  @middlewares.each { |x| yield x }
end

def initialize(*args)
  @middlewares = []
  yield(self) if block_given?
end

def initialize_copy(other)
  self.middlewares = other.middlewares.dup
end

def insert(index, *args, &block)
  index = assert_index(index, :before)
  middleware = self.class::Middleware.new(*args, &block)
  middlewares.insert(index, middleware)
end

def insert_after(index, *args, &block)
  index = assert_index(index, :after)
  insert(index + 1, *args, &block)
end

def last
  middlewares.last
end

def size
  middlewares.size
end

def swap(target, *args, &block)
  index = assert_index(target, :before)
  insert(index, *args, &block)
  middlewares.delete_at(index + 1)
end

def use(*args, &block)
  middleware = self.class::Middleware.new(*args, &block)
  middlewares.push(middleware)
end