Elasticsearch autocomplete search on array field

I am working on autocomplete suggestion on document field that has array of type string. My document is like below;

{

    "title": "Product1",
    "sales": "6",
    "rating": "0.0",
    "cost": "45.00",
    "tags": [
        "blog",
        "magazine",
        "responsive",
        "two columns",
        "wordpress"
    ],
    "category": "wordpress",
    "description": "Product1 Description",
    "createDate": "2013-12-19"
}

{

    "title": "Product1",
    "sales": "6",
    "rating": "0.0",
    "cost": "45.00",
    "tags": [
        "blog",
        "paypal",
        "responsive",
        "skrill",
        "wordland"
    ],
    "category": "wordpress",
    "description": "Product1 Description",
    "createDate": "2013-12-19"
}

I am performing autocomplete search on tags field. My query is like;

query: {
                    query_string: {
                        query: "word*",
                        fields: ["tags"]
                    }
                },
                facets: {
                    tags: {
                        terms: {
                            field: "tags"
                        }
                    }
                }

When user type "word" I want to display "wordland" and "wordpress". However, I couldn't manage to do that.

Could you please help on this?

Thanks