connector/matrix: force .jpg suffix on image filenames without extensions

Signed-off-by: Sumner Evans <sumner.evans@automattic.com>

pkg/connector/matrix.go

@@ -33,12 +33,22 @@ import (
 	"go.mau.fi/mautrix-telegram/pkg/connector/waveform"
 )
 
-func getMediaFilename(content *event.MessageEventContent) string {
+func getMediaFilename(content *event.MessageEventContent) (filename string) {
 	if content.FileName != "" {
-		return content.FileName
+		filename = content.FileName
 	} else {
-		return content.Body
+		filename = content.Body
 	}
+	if filename == "" {
+		return "image.jpg" // Assume it's a JPEG image
+	}
+	if content.MsgType == event.MsgImage && (!strings.HasSuffix(filename, ".jpg") && !strings.HasSuffix(filename, ".jpeg") && !strings.HasSuffix(filename, ".png")) {
+		if content.Info != nil && content.Info.MimeType != "" {
+			return filename + strings.TrimPrefix(content.Info.MimeType, "image/")
+		}
+		return filename + ".jpg" // Assume it's a JPEG
+	}
+	return filename
 }
 
 func (t *TelegramClient) transferMediaToTelegram(ctx context.Context, content *event.MessageEventContent, sticker bool) (tg.InputMediaClass, error) {