1. I know how to use ace editor in web page
2. I know how to add a completer

I want to do like this, input a command, a blank space, then press `-` (dash),
let ace editor autocomplete options(parameters), what should I do?

For example, here is a command `Print` with options `-a|-b|-c|-d`,
when I input `Print -`, how can trigger autocomplete, and let you select
`-a` or `-b` or `-c` or `-d`?