module Sprockets::Server

def headers(env, asset, length)
  Hash.new.tap do |headers|
    # Set content type and length headers
    headers["Content-Type"]   = asset.content_type
    headers["Content-Length"] = length.to_s
    # Set caching headers
    headers["Cache-Control"]  = "public"
    headers["Last-Modified"]  = asset.mtime.httpdate
    headers["ETag"]           = etag(asset)
    # 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"
    end
  end
end