using System;
using System.Collections.Generic;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            App app = new App();
            app.Use(next => {
                Console.WriteLine(1);
                return i => {
                    Console.WriteLine("1-before");
                    next.Invoke(11);
                    Console.WriteLine("1-after");
                };
            });
            app.Use(next => {
                Console.WriteLine(2);
                return i => {
                    Console.WriteLine("2-before");
                    next.Invoke(22);
                    Console.WriteLine("2-after");
                };
            });
            app.Use(next => {
                Console.WriteLine(3);
                return i => {
                    Console.WriteLine("3-before");
                    next.Invoke(33);
                    Console.WriteLine("3-after");
                };
            });
            Action<int> act=  app.Builder();
            act.Invoke(100);
            Console.ReadLine();
        }
    }


    public class App
    {
        List<Func<Action<int>, Action<int>>> list = new List<Func<Action<int>, Action<int>>>();

        public void Use(Func<Action<int>, Action<int>> func)
        {
            list.Add(func);
        }

        public Action<int> Builder()
        {
            //当集合为空时执行，相当于.net core 下的404
            Action<int> action = act => { Console.WriteLine("404"); };
            list.Reverse();
            foreach (Func<Action<int>, Action<int>> item in list)
            {
                action = item.Invoke(action);
            }
            return action;
        }
    }
}