package main

import (
	"encoding/json"
	mqtt "github.com/eclipse/paho.mqtt.golang"
	"log"
	"os"
	"os/exec"
	"time"
)

type Result struct {
	Command string
	Output  string
	Error   string
}

func main() {

	var msgchan = make(chan mqtt.Message, 4)

	if len(os.Args) < 5 {
		log.Fatalf("Usage: %s <broker> <client_id> <username> <password>", os.Args[0])
	}
	opts := mqtt.NewClientOptions()
	opts.AddBroker(os.Args[1])
	opts.SetClientID(os.Args[2])
	opts.SetUsername(os.Args[3])
	opts.SetPassword(os.Args[4])
	opts.SetDefaultPublishHandler(func(client mqtt.Client, msg mqtt.Message) {
		msgchan <- msg
	})
	opts.OnConnect = connectHandler
	opts.SetKeepAlive(20 * time.Second)
	opts.SetAutoReconnect(true)
	opts.SetWill("mqtt2exec/"+os.Args[2]+"/state", "offline", 1, true)
	client := mqtt.NewClient(opts)
	sleep := 1 * time.Second
	for {
		if token := client.Connect(); token.Wait() && token.Error() != nil {
			log.Printf("Initial connection failed: %s", token.Error())
			sleep *= 2
			time.Sleep(sleep)
		} else {
			log.Printf("Connected to broker: %s", os.Args[1])
			break
		}
	}
	for {
		msg := <-msgchan
		if msg.Topic() == "mqtt2exec/"+os.Args[2]+"/run" {
			cmd := exec.Command("/system/xbin/busybox", "ash", "-c", string(msg.Payload()))
			cmd.Stdin = nil
			out, err := cmd.CombinedOutput()
			result := Result{
				Command: string(msg.Payload()),
				Output:  string(out),
			}
			if err != nil {
				result.Error = err.Error()
			}
			resultJSON, _ := json.Marshal(result)
			client.Publish("mqtt2exec/"+os.Args[2]+"/result", 0, false, resultJSON)
		}
	}

}

func connectHandler(c mqtt.Client) {
	token := c.Subscribe("mqtt2exec/"+os.Args[2]+"/run", 2, nil)
	token.Wait()
	if token.Error() != nil {
		log.Printf("mqtt2exec: Error subscribing to topic: %s", token.Error())
	}
	c.Publish("mqtt2exec/"+os.Args[2]+"/state", 1, true, "online")
}