module ActiveAdmin::ResourceController::Streaming

def csv_filename
  "#{resource_collection_name.to_s.gsub('_', '-')}-#{Time.zone.now.to_date.to_s(:default)}.csv"
end

def index
  super do |format|
    format.csv { stream_csv }
    yield(format) if block_given?
  end
end

def stream_csv
  headers['Content-Type'] = 'text/csv; charset=utf-8' # In Rails 5 it's set to HTML??
  headers['Content-Disposition'] = %{attachment; filename="#{csv_filename}"}
  stream_resource &active_admin_config.csv_builder.method(:build).to_proc.curry[self]
end

def stream_resource(&block)
  headers['X-Accel-Buffering'] = 'no'
  headers['Cache-Control'] = 'no-cache'
  if ActiveAdmin.application.disable_streaming_in.include? Rails.env
    self.response_body = block['']
  else
    self.response_body = Enumerator.new &block
  end
end