main.go

package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	smartmeter = prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "SmartMater_Value",
		Help: "Watt value from SmartMeter",
	})
)

func init() {
	prometheus.MustRegister(smartmeter)
}

func fetchSmartMeterValue() {
	for {
		client := &http.Client{}
		req, err := http.NewRequest("GET", "http://192.168.xxx.xxx/php/get_property_m.php?ba=xx:xx:xx:xx:xx:xx:xx:xx&eoj=0x028801&epc=0xE7", nil)
		if err != nil {
			fmt.Println("Error:", err)
			continue
		}
		req.Header.Set("Referer", "http://192.168.xxx.xxx/smartmeter.html")

		resp, err := client.Do(req)
		if err != nil {
			fmt.Println("Error:", err)
			continue
		}

		body, err := ioutil.ReadAll(resp.Body)
		if err != nil {
			fmt.Println("Error:", err)
			continue
		}
		resp.Body.Close()

		hexValue := strings.TrimSpace(string(body))
		hexValue = strings.TrimPrefix(hexValue, "0x")

		value, err := strconv.ParseInt(hexValue, 16, 64)
		if err != nil {
			fmt.Println("Error:", err)
			continue
		}

		smartmeter.Set(float64(value))

		time.Sleep(10 * time.Second)
	}
}

func main() {
	go fetchSmartMeterValue()

	http.Handle("/metrics", promhttp.Handler())
	http.ListenAndServe(":9091", nil)
}