fix: split the message for Telegram if it's too long (close #79)

channel/telegram.go

@@ -9,6 +9,8 @@ import (
 	"net/http"
 )
 
+var TelegramMaxMessageLength = 4096
+
 type telegramMessageRequest struct {
 	ChatId    string `json:"chat_id"`
 	Text      string `json:"text"`
@@ -34,6 +36,15 @@ func SendTelegramMessage(message *model.Message, user *model.User, channel_ *mod
 		messageRequest.Text = message.Content
 		messageRequest.ParseMode = "markdown"
 	}
+	text := messageRequest.Text
+	idx := 0
+	for idx < len(text) {
+		nextIdx := idx + TelegramMaxMessageLength
+		if nextIdx > len(text) {
+			nextIdx = len(text)
+		}
+		messageRequest.Text = text[idx:nextIdx]
+		idx = nextIdx
 		jsonData, err := json.Marshal(messageRequest)
 		if err != nil {
 			return err
@@ -51,5 +62,6 @@ func SendTelegramMessage(message *model.Message, user *model.User, channel_ *mod
 		if !res.Ok {
 			return errors.New(res.Description)
 		}
+	}
 	return nil
 }