Fix Telegram Problem (unforwarded formatting and skipping of linebreaks) (#1749)

* Change bridge/telegram/handlers.go

Comment out the removing of empty lines
add support for bold, italic and striked telegram messages

* Implement Telegram MessageEntities correctly

* Apply gofmt

Co-authored-by: Jan Martin Reckel <jan-martin.reckel@s2017.tu-chemnitz.de>
Co-authored-by: Wim <wim@42.be>

bridge/telegram/handlers.go

@@ -201,7 +201,8 @@ func (b *Btelegram) handleRecv(updates <-chan tgbotapi.Update) {
 		b.handleEntities(&rmsg, message)
 
 		if rmsg.Text != "" || len(rmsg.Extra) > 0 {
-			rmsg.Text = helper.RemoveEmptyNewLines(rmsg.Text)
+			// Comment the next line out due to avoid removing empty lines in Telegram
+			// rmsg.Text = helper.RemoveEmptyNewLines(rmsg.Text)
 			// channels don't have (always?) user information. see #410
 			if message.From != nil {
 				rmsg.Avatar = helper.GetAvatar(b.avatarMap, strconv.FormatInt(message.From.ID, 10), b.General)
@@ -509,5 +510,21 @@ func (b *Btelegram) handleEntities(rmsg *config.Message, message *tgbotapi.Messa
 			rmsg.Text = rmsg.Text[:offset] + "```\n" + rmsg.Text[offset:offset+e.Length] + "\n```" + rmsg.Text[offset+e.Length:]
 			indexMovedBy += 8
 		}
+
+		if e.Type == "bold" {
+			offset := e.Offset + indexMovedBy
+			rmsg.Text = rmsg.Text[:offset] + "*" + rmsg.Text[offset:offset+e.Length] + "*" + rmsg.Text[offset+e.Length:]
+			indexMovedBy += 2
+		}
+		if e.Type == "italic" {
+			offset := e.Offset + indexMovedBy
+			rmsg.Text = rmsg.Text[:offset] + "_" + rmsg.Text[offset:offset+e.Length] + "_" + rmsg.Text[offset+e.Length:]
+			indexMovedBy += 2
+		}
+		if e.Type == "strike" {
+			offset := e.Offset + indexMovedBy
+			rmsg.Text = rmsg.Text[:offset] + "~" + rmsg.Text[offset:offset+e.Length] + "~" + rmsg.Text[offset+e.Length:]
+			indexMovedBy += 2
+		}
 	}
 }