package main

import (
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"runtime"
	"time"

	mqtt "github.com/eclipse/paho.mqtt.golang"
	"github.com/joho/godotenv"
	"github.com/shirou/gopsutil/cpu"
	"github.com/shirou/gopsutil/mem"
)

// PCInfo 定义 PC 使用信息的结构。
type PCInfo struct {
	CPUUsage float64 `json:"cpu_usage"` // CPU
	MemUsage float64 `json:"mem_usage"` // Memory
}

// Command 定义接收命令的结构。
type Command struct {
	Action string `json:"action"` // Action 待执行
}

// loadEnv 加载 .env 文件以读取环境变量。
func loadEnv() {
	err := godotenv.Load(".env")
	if err != nil {
		fmt.Println("Error loading .env file")
	}
}

// getPCInfo 检索当前 PC 使用信息。
func getPCInfo() (PCInfo, error) {
	cpuPercentages, err := cpu.Percent(0, false)
	if err != nil {
		return PCInfo{}, err
	}

	memInfo, err := mem.VirtualMemory()
	if err != nil {
		return PCInfo{}, err
	}

	// 保留2位小数
	return PCInfo{
		CPUUsage: float64(int(cpuPercentages[0]*100)) / 100,
		MemUsage: float64(int(memInfo.UsedPercent*100)) / 100,
	}, nil
}

// onMessageReceived 处理从 MQTT 接收的消息。
func onMessageReceived(client mqtt.Client, msg mqtt.Message) {
	var cmd Command
	err := json.Unmarshal(msg.Payload(), &cmd)
	if err != nil {
		fmt.Println("Error decoding JSON command:", err)
		return
	}

	if cmd.Action == "shutdown" {
		fmt.Println("Shutdown command received. Shutting down...")
		executeShutdown()
	}
}

// executeShutdown 根据操作系统执行关机命令。
func executeShutdown() {
	var cmd *exec.Cmd
	switch runtime.GOOS {
	case "windows":
		cmd = exec.Command("shutdown", "/s", "/t", "0")
	case "linux", "darwin":
		cmd = exec.Command("shutdown", "-h", "now")
	default:
		fmt.Println("Shutdown not supported on this OS")
		return
	}
	err := cmd.Run()
	if err != nil {
		fmt.Println("Failed to execute shutdown:", err)
	}
}

func main() {
	loadEnv()

	broker := os.Getenv("MQTT_BROKER")
	clientID := os.Getenv("MQTT_CLIENT_ID")
	topic := os.Getenv("MQTT_TOPIC")

	opts := mqtt.NewClientOptions()
	opts.AddBroker(broker)
	opts.SetClientID(clientID)
	opts.SetDefaultPublishHandler(onMessageReceived)

	client := mqtt.NewClient(opts)
	if token := client.Connect(); token.Wait() && token.Error() != nil {
		fmt.Println(token.Error())
		return
	}

	// 订阅主题以接收命令
	client.Subscribe(topic, 0, nil)

	for {
		pcInfo, err := getPCInfo()
		if err != nil {
			fmt.Println("Error getting PC info:", err)
			continue
		}

		pcInfoJSON, err := json.Marshal(pcInfo)
		if err != nil {
			fmt.Println("Error encoding PC info to JSON:", err)
			continue
		}

		token := client.Publish(topic, 0, false, pcInfoJSON)
		token.Wait()

		fmt.Println("Message published:", string(pcInfoJSON))

		time.Sleep(10 * time.Second) // 控制发送频率，例如每10秒发送一次
	}

	// 完成后断开 MQTT 客户端连接
	// client.Disconnect(250)
}