module ActionDispatch::Http::Cache::Response

def merge_and_normalize_cache_control!(cache_control)
  control = cache_control_headers
  return if control.empty? && cache_control.empty?  # Let middleware handle default behavior
  if cache_control.any?
    # Any caching directive coming from a controller overrides no-cache/no-store in
    # the default Cache-Control header.
    control.delete(:no_cache)
    control.delete(:no_store)
    if extras = control.delete(:extras)
      cache_control[:extras] ||= []
      cache_control[:extras] += extras
      cache_control[:extras].uniq!
    end
    control.merge! cache_control
  end
  options = []
  if control[:no_store]
    options << PRIVATE if control[:private]
    options << NO_STORE
  elsif control[:no_cache]
    options << PUBLIC if control[:public]
    options << NO_CACHE
    options.concat(control[:extras]) if control[:extras]
  else
    extras = control[:extras]
    max_age = control[:max_age]
    stale_while_revalidate = control[:stale_while_revalidate]
    stale_if_error = control[:stale_if_error]
    options << "max-age=#{max_age.to_i}" if max_age
    options << (control[:public] ? PUBLIC : PRIVATE)
    options << MUST_REVALIDATE if control[:must_revalidate]
    options << "stale-while-revalidate=#{stale_while_revalidate.to_i}" if stale_while_revalidate
    options << "stale-if-error=#{stale_if_error.to_i}" if stale_if_error
    options << IMMUTABLE if control[:immutable]
    options.concat(extras) if extras
  end
  self._cache_control = options.join(", ")
end