class Grape::Middleware::Stack

def [](index)
  middlewares[index]
end

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

def build(builder = Rack::Builder.new)
  others.shift(others.size).each { |m| merge_with(m) }
  middlewares.each do |m|
    m.use_in(builder)
  end
  builder
end

def concat(other_specs)
  @others << Array(other_specs).reject { |o| o.first == :use }
  merge_with(Array(other_specs).select { |o| o.first == :use })
end

def each(&block)
  @middlewares.each(&block)
end

def initialize
  @middlewares = []
  @others = []
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 merge_with(middleware_specs)
  middleware_specs.each do |operation, *args|
    if args.last.is_a?(Proc)
      last_proc = args.pop
      public_send(operation, *args, &last_proc)
    else
      public_send(operation, *args)
    end
  end
end

def size
  middlewares.size
end

def use(...)
  middleware = self.class::Middleware.new(...)
  middlewares.push(middleware)
end