module ActionView::CollectionCaching

def cache_collection_render(instrumentation_payload)
  return yield unless @options[:cached]
  keyed_collection = collection_by_cache_keys
  cached_partials  = collection_cache.read_multi(*keyed_collection.keys)
  instrumentation_payload[:cache_hits] = cached_partials.size
  @collection = keyed_collection.reject { |key, _| cached_partials.key?(key) }.values
  rendered_partials = @collection.empty? ? [] : yield
  index = 0
  fetch_or_cache_partial(cached_partials, order_by: keyed_collection.each_key) do
    rendered_partials[index].tap { index += 1 }
  end
end

def collection_by_cache_keys
  @collection.each_with_object({}) do |item, hash|
    hash[expanded_cache_key(item)] = item
  end
end

def expanded_cache_key(key)
  key = @view.fragment_cache_key(@view.cache_fragment_name(key, virtual_path: @template.virtual_path))
  key.frozen? ? key.dup : key # #read_multi & #write may require mutability, Dalli 2.6.0.
end

def fetch_or_cache_partial(cached_partials, order_by:)
  order_by.map do |cache_key|
    cached_partials.fetch(cache_key) do
      yield.tap do |rendered_partial|
        collection_cache.write(cache_key, rendered_partial)
      end
    end
  end
end