nanoc/nanoc

Hey everyone. I thought I'd come back and post my solution to the problem I asked help with. This preprocess block will use :mtime and a separate (and auto generated) meta file to keep track of the updates and, hopefully, make item[:updated_at] automatically available only when relevant. Maybe there's a simpler way to achieve this but this is the best I got for now!

Thanks for the help!

preprocess do
  def prepare_blog_articles
    now = Time.now.round

    @items.select { |i| i.identifier.to_s =~ %r{^/blog/[^_]} }.each do |item|
      if item[:meta_filename]
        item_check_updates(item, now)
      else
        item_first_publish(item, now)
      end
    end
  end

  def item_first_publish(item, now)
    item[:created_at] = now
    item[:last_updated_at] = now

    create_meta_file(item, now)
    update_mtime(item, now)
  end

  def item_check_updates(item, now)
    # Abnormal cases; if this happens, it was a mistake and must be fixed manually:
    abort "#{item[:meta_filename]} should contain 'created_at' info" unless item.key?(:created_at)
    abort "#{item[:meta_filename]} should contain 'last_updated_at' info" unless item.key?(:last_updated_at)

    # We only set item[:updated_at] if we want that info to appear in the final
    # rendering of the item. If the item has never been updated, both fields in
    # the meta file should be equal here. Otherwise we use the :last_updated_at
    # as the most recent date.
    if item[:last_updated_at] != item[:created_at]
      item[:updated_at] = item[:last_updated_at]
    end

    # But maybe the item has been updated but the meta file hasn't. In that
    # case, item[:mtime] will not be equal to item[:last_updated_at]. So we set
    # the revelant values for NOW and record them. (This may override
    # item[:update_at] if it was set in the previously if block, but that is by
    # design: it means the item was updated again after the last update.)
    if item[:last_updated_at].to_i != item[:mtime].to_i
      item[:updated_at] = now

      update_meta_file(item, now)
      update_mtime(item, now)
    end
  end

  def create_meta_file(item, now)
    meta_filename = Pathname(item.raw_filename).sub_ext(".yaml")
    File.open(meta_filename, 'wb') { |f| f.write "created_at: #{now}\nlast_updated_at: #{now}\n" }
  end

  def update_meta_file(item, now)
    meta_content = IO.read(item[:meta_filename])
    IO.write(item[:meta_filename], meta_content.sub(/^last_updated_at:.+/, "last_updated_at: #{now}"))
  end

  def update_mtime(item, now)
    File.utime(now, now, item.raw_filename)
  end

  prepare_blog_articles
end