package main

import (
	"context"
	"log"
	"net"
	"os"
	"os/signal"
	"syscall"
	"time"

	"go.etcd.io/etcd/client/v3"
	"go.etcd.io/etcd/client/v3/naming/endpoints"
)

// UserServer 用户服务结构体
type UserServer struct{}

// Login 登录方法示例
func (u *UserServer) Login(username string, password string) string {
	if username == "admin" && password == "123456" {
		return "登录成功，token: abc123"
	}
	return "登录失败，用户名或密码错误"
}

// 服务注册到etcd
func registerService(etcdAddr []string, serviceName, serviceAddr string) (*clientv3.Client, error) {
	// 1. 创建etcd客户端（返回客户端，方便后续注销）
	client, err := clientv3.New(clientv3.Config{
		Endpoints:   etcdAddr,
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		return nil, err
	}

	// 2. 创建租约（10秒有效期）
	leaseResp, err := client.Grant(context.Background(), 10)
	if err != nil {
		client.Close()
		return nil, err
	}
	leaseID := leaseResp.ID

	// 3. 启动租约续约
	keepAliveChan, err := client.KeepAlive(context.Background(), leaseID)
	if err != nil {
		client.Revoke(context.Background(), leaseID) // 清理租约
		client.Close()
		return nil, err
	}

	// 后台处理续约结果
	go func() {
		for {
			select {
			case keepAliveResp, ok := <-keepAliveChan:
				if !ok {
					// 续约通道关闭，尝试重新连接
					log.Println("租约续约通道关闭，尝试重新连接...")
					return
				}
				log.Printf("服务续约成功，租约ID: %v", keepAliveResp.ID)
			}
		}
	}()

	// 4. 注册服务到etcd
	em, err := endpoints.NewManager(client, "/services/"+serviceName)
	if err != nil {
		client.Revoke(context.Background(), leaseID)
		client.Close()
		return nil, err
	}

	// 注册服务并绑定租约
	err = em.AddEndpoint(
		context.Background(),
		"/services/"+serviceName+"/"+serviceAddr,
		endpoints.Endpoint{Addr: serviceAddr},
		clientv3.WithLease(leaseID),
	)
	if err != nil {
		client.Revoke(context.Background(), leaseID)
		client.Close()
		return nil, err
	}

	return client, nil
}

// 从etcd注销服务
func unregisterService(client *clientv3.Client, serviceName, serviceAddr string) {
	if client == nil {
		return
	}
	defer client.Close()

	em, err := endpoints.NewManager(client, "/services/"+serviceName)
	if err != nil {
		log.Printf("注销服务失败: %v", err)
		return
	}

	// 主动删除服务节点
	err = em.DeleteEndpoint(context.Background(), "/services/"+serviceName+"/"+serviceAddr)
	if err != nil {
		log.Printf("删除服务节点失败: %v", err)
	} else {
		log.Println("服务已从etcd注销")
	}
}

func main() {
	// 服务配置
	etcdAddr := []string{"http://127.0.0.1:2379"}
	serviceName := "user-service"
	serviceAddr := "127.0.0.1:8080" // 服务监听地址

	// 注册服务到etcd
	etcdClient, err := registerService(etcdAddr, serviceName, serviceAddr)
	if err != nil {
		log.Fatalf("服务注册失败: %v", err)
	}
	log.Printf("服务 %s 已注册到etcd，地址: %s", serviceName, serviceAddr)

	// 启动一个实际的服务监听（例如TCP服务），避免程序立即退出
	listener, err := net.Listen("tcp", serviceAddr)
	if err != nil {
		log.Fatalf("服务监听失败: %v", err)
	}
	defer listener.Close()
	log.Printf("服务已启动，监听地址: %s", serviceAddr)

	// 优雅退出处理（捕获中断信号，注销服务）
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
	<-sigChan // 等待中断信号

	// 程序退出前注销服务
	unregisterService(etcdClient, serviceName, serviceAddr)
	log.Println("服务已停止")
}