Activeadmin MongoID with Fulltext Search on Sidebar

_search.html.haml

/ file: app/views/admin/users/_search.html.haml
#panel_contents
  = form_for(admin_users_path, method: :get) do |f|
    .filter_form_field.filter_string
      = label_tag :query, "Full Text Search"
      = text_field_tag :query, params[:query], { placeholder: "Keyword to search" }
    .buttons
      = submit_tag "Search"

user.rb

# app/models/user.rb

class User
  include Mongoid::Document
  
  field :name,      type: String
  field :email,     type: String
  field :phone,     type: String

  # Full Text search for users, only one per collection allowed
  index({ name: 'text', email: 'text', phone: 'text' })
  
end

user_admin.rb

# app/admin/user.rb
ActiveAdmin.register User do

  # Filter does not work yet, so using full text search from mongoDB
  config.filters = false
  sidebar :search, partial: 'search'
  
  # ... the usual admin code

  
  controller do

    def scoped_collection
      scope = User
      if params[:query].present?
        ids = User.text_search(params[:query]).map { |t| t.id.to_s }
        # text_search method is not a MongoID::Criteria
        # so need to search again using :id in array
        scope = scope.in(id: ids)
      end
      scope
    end

  end
  
end