Fs-river and autocomplete

Hi I am trying to use auto complete.
But my documents are getting indexed using fs-river.
Suppose the content is

dolor asmit domen
dujocokvic amuro aantaha

so when a user types "aa" then it should show "aantaha"

How do I achieve it. I have googled a lot of stuff but none is completely helpful.

Check out https://www.elastic.co/guide/en/elasticsearch/reference/current/search-suggesters.html#search-suggesters

Yeah but FSRiver does not generate anything in _suggest endpoint.

May be something based on edgengram analyzer with aggregation like filter agg and a terms inside?

Unsure if this would work. You should try first with an example outside FSRiver context.