telegram-to-discord/tgBot/handler.go

package tgBot

import (
	"bytes"
	"context"
	"fmt"
	"github.com/go-telegram/bot"
	"github.com/go-telegram/bot/models"
	log "github.com/sirupsen/logrus"
	"io"
	"net/http"
	"path/filepath"
	"sync"
	"tg-disc-bot/config"
	"tg-disc-bot/dto"
	"time"
)

type TgBot struct {
	ctx             context.Context
	bot             *bot.Bot
	chatID          int64
	token           string
	msgChan         chan dto.TelegramDTO
	mediaGroupCache map[string][]dto.Image
	cacheMutex      sync.Mutex
}

func NewTgBot(ctx context.Context, config config.TelegramConfig) (*TgBot, error) {
	tgBot := &TgBot{
		ctx:             ctx,
		chatID:          config.ChatID,
		token:           config.Token,
		msgChan:         make(chan dto.TelegramDTO, 100),
		mediaGroupCache: make(map[string][]dto.Image, 10),
		cacheMutex:      sync.Mutex{},
	}
	var err error

	tgBot.bot, err = bot.New(config.Token)
	if err != nil {
		return nil, err
	}

	return tgBot, nil
}

func (b *TgBot) Start(fromDiscord chan dto.DiscordDTO) chan dto.TelegramDTO {

	b.bot.RegisterHandler(bot.HandlerTypeMessageText, "", bot.MatchTypeContains, b.mainHandler)

	go func() {
		log.Info("Starting telegram bot...")
		b.bot.Start(b.ctx)
	}()

	go func() {
		for msg := range fromDiscord {
			log.WithField("content", msg).Debug("TG | Message from Discord")

			m := fmt.Sprintf("*\\[ %s \\]*\n%s", msg.AuthorName, msg.Content)

			b.bot.SendMessage(b.ctx, &bot.SendMessageParams{
				ChatID:    b.chatID,
				Text:      m,
				ParseMode: "",
			})

			if msg.Images != nil {
				var mediaGroup []models.InputMedia
				for _, img := range *msg.Images {
					photo := &models.InputMediaPhoto{
						Media: fmt.Sprintf("attach://%s", img.Filename),
						//Caption:         "test caption",
						MediaAttachment: bytes.NewReader(img.Data),
					}
					mediaGroup = append(mediaGroup, photo)
				}

				_, err := b.bot.SendMediaGroup(b.ctx, &bot.SendMediaGroupParams{
					ChatID: b.chatID,
					Media:  mediaGroup,
				})

				if err != nil {
					log.Error("TG | Failed to send media group")
				}
			}
		}
	}()

	return b.msgChan
}

func (b *TgBot) mainHandler(ctx context.Context, bt *bot.Bot, update *models.Update) {
	if update.Message != nil && !update.Message.From.IsBot {
		mediaGroupID := update.Message.MediaGroupID
		if mediaGroupID != "" {
			b.processMediaGroup(update, mediaGroupID, b.msgChan)
		} else {
			b.proccessSimple(update, b.msgChan)
		}
	}
}

func (b *TgBot) getImage(photo models.PhotoSize) *dto.Image {
	fileID := &bot.GetFileParams{FileID: photo.FileID}
	file, err := b.bot.GetFile(b.ctx, fileID)
	if err != nil {
		log.Errorf("GetFile error: %s", err)
		return nil
	}

	if file.FilePath == "" {
		log.Errorf("FilePath is empty for fileID: %s", photo.FileID)
		return nil
	}

	resp, err := http.Get(fmt.Sprintf("https://api.telegram.org/file/bot%s/%s", b.token, file.FilePath))
	if err != nil {
		log.Errorf("Download error: %s", err)
		return nil
	}
	defer resp.Body.Close()

	imgBytes, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Errorf("ReadAll error: %s", err)
		return nil
	}

	image := dto.Image{
		Filename: filepath.Base(file.FilePath),
		Data:     imgBytes,
	}

	return &image
}

func (b *TgBot) proccessSimple(update *models.Update, msgChan chan<- dto.TelegramDTO) {
	var images []dto.Image
	content := update.Message.Text

	if update.Message.Photo != nil {
		largest := update.Message.Photo[len(update.Message.Photo)-1]
		images = append(images, *b.getImage(largest))
		content = update.Message.Caption
	}

	msg := dto.TelegramDTO{
		AuthorName: b.getName(update),
		Content:    content,
		Images:     &images,
	}

	msgChan <- msg
}

func (b *TgBot) processMediaGroup(update *models.Update, mediaGroupID string, msgChan chan<- dto.TelegramDTO) {
	b.cacheMutex.Lock()
	defer b.cacheMutex.Unlock()

	if update.Message.Photo != nil {
		largest := update.Message.Photo[len(update.Message.Photo)-1]
		image := b.getImage(largest)
		b.mediaGroupCache[mediaGroupID] = append(b.mediaGroupCache[mediaGroupID], *image)
	}

	var content string
	if update.Message.Caption != "" {
		content = update.Message.Caption
	} else {
		content = update.Message.Text
	}

	go func() {
		time.Sleep(2 * time.Second)

		b.cacheMutex.Lock()
		defer b.cacheMutex.Unlock()

		images, exists := b.mediaGroupCache[mediaGroupID]
		if !exists || len(images) == 0 {
			return
		}

		delete(b.mediaGroupCache, mediaGroupID)

		msg := dto.TelegramDTO{
			AuthorName: b.getName(update),
			Content:    content,
			Images:     &images,
		}

		msgChan <- msg
	}()
}

func (b *TgBot) getName(update *models.Update) string {
	switch {
	case update.Message.From.Username != "":
		return update.Message.From.Username
	case update.Message.From.FirstName != "":
		return update.Message.From.FirstName
	case update.Message.From.LastName != "":
		return update.Message.From.LastName
	default:
		return "No name"
	}
}