Rails Helper Module: Encodes the asset's timestamp into the request URL as directory which will be removed by Apache's mod_rewrite

cache_helper.rb

module CacheHelper
  #
  # Implements Google's "Leverage Proxy Caching" tip:
  # Instead of using a query parameter as cache buster -
  # encode it into the URL to ensure public proxies can
  # cache it too.
  #
  # NOTE: Activates in production mode only because it's
  # not necessary for development and needs a mod_rewrite
  # rule for Apache anyway:
  #
  # RewriteEngine On
  # RewriteRule ^/\d{5,}(/.+)$ $1
  #
  # This will remove the (fake) directory named after
  # the cache buster from the front of the incoming URL.
  #
  def rewrite_asset_path(*args)
    source = super

    if Rails.env.production?
      path, cache_buster = source.split("?")

      if cache_buster.blank?
        source
      else
        "/#{cache_buster}#{path}"
      end
    else
      source
    end
  end
end