Improve generated file's filename

app/app.py

@@ -85,13 +85,24 @@ async def generate_rest(name: str):
                         break
                     bytes_io.write(data)
 
+            out_filename = secure_filename(name)
+
+            # a tester found that, if only special characters (like _) are sent to this method, it will return an
+            # empty string
+            # to improve UX, we replace empty strings with a _
+            if not out_filename:
+                out_filename = "_"
+
+            # to further improve the UX, let's add some prefix and the .stl suffix
+            out_filename = f"bottle-clip-{out_filename}.stl"
+
             # using secure_filename allows us to send the file to the user with some safe yet reasonably
             # identifiable filename
             return await send_file(
                 bytes_io,
                 mimetype="model/stl",
                 as_attachment=True,
-                attachment_filename=secure_filename(f"{name}.stl")
+                attachment_filename=out_filename,
             )