a simple example robot for telegram

main.go

package main

import (
	"image"
	_ "image/png"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"regexp"
	"time"

	"github.com/tucnak/telebot"
)

var bot *telebot.Bot

func getImageDimension(imagePath string) (int, int, error) {
	file, err := os.Open(imagePath)
	if err != nil {
		return 0, 0, err
	}
	defer file.Close()

	image, _, err := image.DecodeConfig(file)
	if err != nil {
		return 0, 0, err
	}
	return image.Width, image.Height, nil
}

func snapshot(url string, message telebot.Message) {
	tmp, err := ioutil.TempFile("", "bot")
	if err != nil {
		bot.SendMessage(message.Chat, "Sorry but there is an error :) "+err.Error(), nil)
		return
	}
	log.Print("getting snapshot of " + url)
	f := tmp.Name()
	tmp.Close()
	defer os.Remove(f)
	cmd := exec.Command("wkhtmltoimage", "-f", "png", url, f+".png")
	cmd.Start()
	err = cmd.Wait()
	if err != nil {
		bot.SendMessage(message.Chat, "Sorry but there is an error in getting the screen shot :) "+err.Error(), nil)
		return
	}
	defer os.Remove(f + ".png")
	log.Print("get size")
	w, h, err := getImageDimension(f + ".png")
	if err != nil {
		bot.SendMessage(message.Chat, "Sorry but there is an error in getting the screen shot :) "+err.Error(), nil)
		return
	}
	file, err := telebot.NewFile(f + ".png")
	if err != nil {
		bot.SendMessage(message.Chat, "Sorry but there is an error :) "+err.Error(), nil)
		return
	}

	photo := &telebot.Photo{Thumbnail: telebot.Thumbnail{File: file, Width: w, Height: h}, Caption: "the url result"}
	log.Print("sending...")
	err = bot.SendPhoto(message.Chat, photo, nil)
	if err != nil {
		bot.SendMessage(message.Chat, "Sorry but there is an error :) "+err.Error(), nil)
		return
	}
	log.Print("done...")

}

var accept = regexp.MustCompile("^/snap[ ]+(.*)$")

func main() {
	var err error
	bot, err = telebot.NewBot("-------------------------------------------")
	if err != nil {
		return
	}

	messages := make(chan telebot.Message)
	bot.Listen(messages, 1*time.Second)

	for message := range messages {
		match := accept.FindStringSubmatch(message.Text)
		if len(match) > 1 {
			go snapshot(match[1], message)
		}
	}
}