gregbell/active_admin

# frozen_string_literal: true
require "csv"

module ActiveAdmin
  class ResourceController < BaseController

    # This module overrides CSV responses to allow large data downloads.
    # Could be expanded to JSON and XML in the future.
    #
    module Streaming

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

      protected

      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] # rubocop:disable Performance/UnfreezeString to preserve encoding
        else
          self.response_body = Enumerator.new &block
        end
      end

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

    end
  end
end