How to pass a product reference key as a filter in search in oracle knowledge advance CP

Summary

I have a requirement, where I have to pass product Id reference key to the search as a filter. So that the search result would show articles tagged with that specific product.

Content

I have a requirement, where I have to pass product  reference key to the search as a filter. So that the search result would show knowledge advance articles tagged with that specific product. I cannot use the OKCSProductCategorySearchFilter widget along with Search as a form input, since user would not select product from the filter dropdown and do key word search. User would do search keyword and programmatically a certain product reference key would be passed as a filter to the search result. I am not able to figure out where to pass the filter array to the search. Any idea