webhook-everything/backend/internal/telegrampackage/telegram.go

package telegrampackage

import (
	"errors"
	"fmt"
	"log"
	"math/rand"
	"strings"
	"time"

	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
	"github.com/google/uuid"
	"gorm.io/gorm"
)

type ChatIDMap struct {
	ID          uuid.UUID `gorm:"primaryKey;type:uuid;default:uuid_generate_v4()"`
	CreatedAt   time.Time
	UpdatedAt   time.Time
	DeletedAt   gorm.DeletedAt `gorm:"index"`
	ChatID      int64
	ChatIDShort string
}

func (env *Env) TelegramSend(chatIDShort string, msg string) error {
	if chatIDShort == "" {
		return errors.New("no chat ID provided")
	}
	bot, err := tgbotapi.NewBotAPI(env.TelegramAPIKey)
	if err != nil {
		log.Println(err)
		return err
	}
	var chatIDMap ChatIDMap
	err = env.DB.Where(&ChatIDMap{ChatIDShort: chatIDShort}).Last(&chatIDMap).Error
	if err != nil {
		log.Println(err)
		log.Println("No such telegram chat ID")
		return err
	}
	chatMsg := tgbotapi.NewMessage(chatIDMap.ChatID, msg)
	_, err = bot.Send(chatMsg)
	if err != nil {
		log.Println(err)
	}
	return nil
}

func (env *Env) TelegramListenAndGen() error {
	for {
		bot, err := tgbotapi.NewBotAPI(env.TelegramAPIKey)
		if err != nil {
			log.Println(err)
			log.Println("Error occured on Telegram listen. Waiting 1 minute")
			time.Sleep(60 * time.Second)
		}
		u := tgbotapi.NewUpdate(0)
		u.Timeout = 60

		updates := bot.GetUpdatesChan(u)

		for update := range updates {
			if update.Message == nil { // ignore any non-Message Updates
				continue
			}

			log.Printf("New message: [%s] %s", update.Message.From.UserName, update.Message.Text)

			// check if contains registration
			if strings.Compare(update.Message.Text, "/register") == 0 {
				var chatIDMap ChatIDMap
				err := env.DB.Where(&ChatIDMap{ChatID: update.Message.Chat.ID}).Last(&chatIDMap).Error
				// chatID already exists
				if err == nil {
					msg := tgbotapi.NewMessage(update.Message.Chat.ID, "You already have a chat ID")
					_, err := bot.Send(msg)
					if err != nil {
						log.Println(err)
					}
					msg = tgbotapi.NewMessage(update.Message.Chat.ID, fmt.Sprintf("Your chat ID is: %s", chatIDMap.ChatIDShort))
					_, err = bot.Send(msg)
					if err != nil {
						log.Println(err)
					}
				} else {
					currChatCode := genShortCode(5)
					chatIDMap.ChatIDShort = currChatCode
					chatIDMap.ChatID = update.Message.Chat.ID
					err := env.DB.Create(&chatIDMap).Error
					if err != nil {
						fmt.Println(err)
					}
					msg := tgbotapi.NewMessage(update.Message.Chat.ID, fmt.Sprintf("Your chat ID is: %s", chatIDMap.ChatIDShort))
					_, err = bot.Send(msg)
					if err != nil {
						log.Println(err)
					}
				}
			} else {
				// Get his current chat ID
				var chatIDMap ChatIDMap
				err := env.DB.Where(&ChatIDMap{ChatID: update.Message.Chat.ID}).Last(&chatIDMap).Error
				if err != nil {
					fmt.Println(err)
				}

				var handled = false
				for _, currFunc := range env.HandlerFunctions {
					currHandled, responseText := currFunc(chatIDMap.ChatIDShort, update.Message.Text)
					handled = handled || currHandled
					if responseText != nil {
						splitSendMessage(bot, update.Message.Chat.ID, *responseText)
					}
				}
				if !handled {
					msg := tgbotapi.NewMessage(update.Message.Chat.ID, "Please send /register to register for a chat ID")
					_, err := bot.Send(msg)
					if err != nil {
						log.Println(err)
					}
				}
			}

		}
	}
}

func genShortCode(n int) string {
	var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
	runeCode := make([]rune, n)
	for i := range runeCode {
		runeCode[i] = letters[rand.Intn(len(letters))]
	}
	return string(runeCode)
}

func splitSendMessage(bot *tgbotapi.BotAPI, chatID int64, message string) {
	MAXMESSAGELENGTH := 2000

	leftoverMessage := []rune(tgbotapi.EscapeText("HTML", message))
	if len(leftoverMessage) > MAXMESSAGELENGTH {
		for len(leftoverMessage) > 0 {
			var currMessage []rune
			if len(leftoverMessage) <= MAXMESSAGELENGTH {
				currMessage = leftoverMessage[:]
				leftoverMessage = []rune("")
			} else {
				currMessage = leftoverMessage[:MAXMESSAGELENGTH]
				leftoverMessage = leftoverMessage[MAXMESSAGELENGTH:]
			}

			msg := tgbotapi.NewMessage(chatID, string(currMessage))
			msg.ParseMode = "HTML"
			msg.DisableWebPagePreview = true
			_, err := bot.Send(msg)
			if err != nil {
				msg := tgbotapi.NewMessage(chatID, err.Error())
				bot.Send(msg)
				log.Println(err)
			}
		}
	} else {
		msg := tgbotapi.NewMessage(chatID, string(message))
		msg.ParseMode = "HTML"
		msg.DisableWebPagePreview = true
		_, err := bot.Send(msg)
		if err != nil {
			msg := tgbotapi.NewMessage(chatID, err.Error())
			bot.Send(msg)
			log.Println(err)
		}
	}
}