class ActiveAdmin::CSVBuilder

def self.default_for_resource(resource)
  new resource: resource do
    column :id
    resource.content_columns.each { |c| column c.name.to_sym }
  end
end

def batch_size
  1000
end

def build(controller, receiver)
  @collection = controller.send(:find_collection, except: :pagination)
  options = ActiveAdmin.application.csv_options.merge self.options
  columns = exec_columns controller.view_context
  if byte_order_mark = options.delete(:byte_order_mark)
    receiver << byte_order_mark
  end
  if options.delete(:column_names) { true }
    receiver << CSV.generate_line(columns.map{ |c| encode c.name, options }, options)
  end
  (1..paginated_collection.total_pages).each do |page_no|
    paginated_collection(page_no).each do |resource|
       resource = controller.send :apply_decorator, resource
       receiver << CSV.generate_line(build_row(resource, columns, options), options)
    end
  end
end

def build_row(resource, columns, options)
  columns.map do |column|
    encode call_method_or_proc_on(resource, column.data), options
  end
end

def column(name, options={}, &block)
  @columns << Column.new(name, @resource, column_transitive_options.merge(options), block)
end

def column_transitive_options
  @column_transitive_options ||= @options.slice(*COLUMN_TRANSITIVE_OPTIONS)
end

def encode(content, options)
  if options[:encoding]
    content.to_s.encode options[:encoding], options[:encoding_options]
  else
    content
  end
end

def exec_columns(view_context = nil)
  @view_context = view_context
  @columns = [] # we want to re-render these every instance
  instance_exec &@block if @block.present?
  columns
end

def initialize(options={}, &block)
  @resource = options.delete(:resource)
  @columns, @options, @block = [], options, block
end

def method_missing(method, *args, &block)
  if @view_context.respond_to? method
    @view_context.public_send method, *args, &block
  else
    super
  end
end

def paginated_collection(page_no = 1)
  @collection.public_send(Kaminari.config.page_method_name, page_no).per(batch_size)
end