Using Nokogiri to generate static header list in Slate/Middleman - ruby

Question

I'm inexperienced with middleman and ruby, but I've been trying to get Slate working so it generates a side navigation/list of header during build time instead of client side using javascript. The problem I am running into is getting the code to include the headers from partials.
An example of the directory structure:
Source
+--config.rb
+--includes
+--file.md
+--otherfile.md
+--index.html
+--layouts
+--layout.erb
Gist of layout and config.rb
Config.rb snippet for this:
require 'nokogiri'
helpers do
def toc_data(page_content)
html_doc = Nokogiri::HTML::DocumentFragment.parse(page_content)
# get a flat list of headers
headers = []
html_doc.css('h1, h2, h3').each do |header|
headers.push({
id: header.attribute('id').to_s,
content: header.content,
level: header.name[1].to_i,
children: []
})
end
[3,2].each do |header_level|
header_to_nest = nil
headers = headers.reject do |header|
if header[:level] == header_level
header_to_nest[:children].push header if header_to_nest
true
else
header_to_nest = header if header[:level] == (header_level - 1)
false
end
end
end
headers
end
end
Layout snippet for this:
<ul id="toc" class="toc">
<% toc_data(page_content).each do |h1| %>
<li>
<%= h1[:content] %>
<ul class="toc-section">
<% h1[:children].each do |h2| %>
<li>
<%= h2[:content] %>
<ul class="toc-submenu">
<% h2[:children].each do |h3| %>
<li>
<%= h3[:content] %>
</li>
<% end %>
</ul>
</li>
<% end %>
</ul>
</li>
<% end %>
</ul>
...
<div class="page-wrapper">
<div class="content">
<%= page_content %>
<% current_page.data.includes && current_page.data.includes.each do |include| %>
<%= partial "includes/#{include}" %>
<% end %>
</div>
</div>
Currently, only headers from the index.html file are getting populated and nothing from the included partials. I believe I may need the existing helper to occur post build similar to what is described in the Middleman docs for sitemaps using a ready helper. I believe I have to make another change to the config code so that it captures additional content outside of the page_content, but I'm not sure what that is due to lack of familiarity. Any pointers would be appreciated.
Edit: After looking into the middleman basics docs, there appear to be two helpers from the Padrino framework that I could make use of: capture_html and concat_content. I'm trying to find where the helper page_content is defined to get extra context for the specific changes I'm making.

Answer 1

Not familiar with that framework but looks like toc_data(page_content) only looks at the main content but not at the current_page.data.includes partials.
So guess you need to pass the partial to your toc_data function as well.
Maybe this works?
<%
full_content = page_content
current_page.data.includes && current_page.data.includes.each do |include|
full_content += partial("includes/#{include}")
end
toc_data(full_content).each do |h1|
%>
...
<% end %>
Hope that helps.

Answer 2

In order to concatenate the current page data with partials with the page_content, use the code below. This also changes what all is needed to yield a complete page.
<%
if current_page.data.includes
current_page.data.includes.each do |include|
page_content += partial("includes/#{include}")
end
end
%>
...
<%= page_content %>