Paperclip.interpolates(:product_code) do |attachment, style|
  attachment.instance.product.code
end

Paperclip.interpolates(:size) do |attachment, style|
  attachment.instance.size
end

Paperclip.interpolates(:timestamp) do |attachment, style|
  attachment.instance_read(:updated_at).in_time_zone(7).strftime("%s")
end

Paperclip.interpolates(:s3_url) do |attachment, style|
  path = attachment.path(style)
  "#{attachment.s3_protocol}://#{Settings.uploadable_asset_host % (path.hash % 4)}/#{path.gsub(%r{^/}, "")}"
end