package main

import (
	"fmt"
	"sync"
	"sync/atomic"
	"unsafe"
)

type node struct {
	value interface{}
	next  unsafe.Pointer
}

type LockFreeStack struct {
	top unsafe.Pointer
}

func (s *LockFreeStack) Push(v interface{}) {
	newNode := &node{value: v}
	for {
		oldTop := atomic.LoadPointer(&s.top)
		newNode.next = oldTop
		if atomic.CompareAndSwapPointer(&s.top, oldTop, unsafe.Pointer(newNode)) {
			break
		}
	}
}

func (s *LockFreeStack) Pop() (interface{}, bool) {
	for {
		oldTop := atomic.LoadPointer(&s.top)
		if oldTop == nil {
			return nil, false // 栈空：返回 false
		}
		node := (*node)(oldTop)
		if atomic.CompareAndSwapPointer(&s.top, oldTop, node.next) {
			return node.value, true // 弹出成功：返回 true
		}
	}
}

func main() {
	stack := &LockFreeStack{}
	var wg sync.WaitGroup
	const ops = 1000

	wg.Add(2)
	// 生产者：压入 1000 个元素
	go func() {
		defer wg.Done()
		for i := 0; i < ops; i++ {
			stack.Push(i)
		}
	}()

	// 消费者：弹出 1000 个元素
	go func() {
		defer wg.Done()
		count := 0
		for count < ops {
			if _, ok := stack.Pop(); ok {
				count++
			}
		}
	}()

	wg.Wait()

	// 🔑 核心修正：验证栈是否为空
	_, popped := stack.Pop() // popped = true 表示"成功弹出"（栈非空）
	if !popped {             // !popped = true 表示"弹出失败"（栈已空）✅
		fmt.Println("✅ 无锁栈验证通过：所有元素正确入栈出栈，栈已空")
	} else {
		fmt.Println("❌ 栈非空，存在数据不一致（验证逻辑已修正）")
	}
}