module Sprockets::Server

def cache_headers(env, etag)
  headers = {}
  # Set caching headers
  headers["Cache-Control"] = "public"
  headers["ETag"]          = %("#{etag}")
  # If the request url contains a fingerprint, set a long
  # expires on the response
  if path_fingerprint(env["PATH_INFO"])
    headers["Cache-Control"] << ", max-age=31536000"
  # Otherwise set `must-revalidate` since the asset could be modified.
  else
    headers["Cache-Control"] << ", must-revalidate"
    headers["Vary"] = "Accept-Encoding"
  end
  headers
end