require 'csv'

module Effective
  module EffectiveDatatable
    module Csv

      def csv_filename
        self.class.name.underscore.parameterize + '.csv'
      end

      def csv_content_type
        'text/csv; charset=utf-8'
      end

      def csv_header
        columns.map { |_, opts| opts[:label] || '' }
      end

      def csv_file
        CSV.generate do |csv|
          csv << csv_header()

          collection.send(csv_collection_method) do |resources|
            resources = arrayize(resources, csv: true)
            format(resources, csv: true)
            finalize(resources)

            resources.each { |resource| csv << resource }
          end
        end
      end

      def csv_stream
        EffectiveResources.with_resource_enumerator do |lines|
          lines << CSV.generate_line(csv_header)

          collection.public_send(csv_collection_method) do |resources|
            resources = arrayize(resources, csv: true)
            format(resources, csv: true)
            finalize(resources)

            resources.each { |resource| lines << CSV.generate_line(resource) }
          end
        end
      end

      private

      def csv_collection_method
        (active_record_collection? ? :find_in_batches : :to_a)
      end

    end
  end
end