module ActiveAdmin::ResourceController::Streaming

def csv_filename
  "#{resource_collection_name.to_s.gsub('_', '-')}-#{Time.zone.now.to_date.to_s}.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"
  headers["Last-Modified"] = Time.current.httpdate
  if ActiveAdmin.application.disable_streaming_in.include? Rails.env
    self.response_body = block[String.new]
  else
    self.response_body = Enumerator.new &block
  end
end