Support for google apps script file

Can someone explain how to get google apps script code completion working? I'd like to edit some google app script files and have code completion support.
It's just a flavor of javascript with their various services in the name space.
I know they can support eclipse, so there must be a way to get the namespace (if i'm using that term correctly)?
Can anyone help?
I understand for now have to manage moving files but I'd love to work on some scripts and save the files via icloud between devices and then just copy paste when ready to test from google editor.

Thanks.