Add table of contents filter

Rules

@@ -46,6 +46,7 @@ compile '*' do
     filter :bootstrappify
     filter :admonition
     filter :colorize_syntax, :default_colorizer => :pygmentsrb
+    filter :toc, style: item[:toc]
     if item[:kind] == 'article'
       layout 'blog'
     else

content/docs/introduction/faq.md

 ---
 title: FAQ
 sort_rank: 5
+toc: full-width
 ---
 
 # Frequently Asked Questions

lib/filters/toc.rb

+# encoding: utf-8
+
+require 'nokogiri'
+
+class TocFilter < ::Nanoc::Filter
+  identifier :toc
+
+  # Number of items required to render a table of contents.
+  TOC_MINIMUM = 2
+
+  def run(content, params={})
+    doc = Nokogiri::HTML(content)
+    titles = doc.xpath('//h1')
+    headers = doc.xpath('//h2|//h3')
+
+    if titles.empty? || headers.length < TOC_MINIMUM
+      return content
+    end
+
+    style = params[:style] || 'right'
+    items = headers.map do |header|
+      title = header.inner_html.sub(/^(.*)<a .*$/, '\1')
+      { :level => header.name, :title => title, :id => header['id'] }
+    end
+
+    titles.first.after(%(<div class="toc toc-#{style}">#{toc(items)}</div>))
+    doc.to_s
+  end
+
+  def toc(items)
+    return '' if items.empty?
+
+    level = ''
+    table = []
+    items.each do |item|
+      if item[:level] > level
+        table << '<ul>'
+      elsif item[:level] < level
+        table << '</ul>'
+      end
+      level = item[:level]
+
+      table << %(<li><a href="##{item[:id]}">#{item[:title]}</a></li>)
+    end
+    table << '</ul>'
+
+    table.join('')
+  end
+end

static/docs.css

@@ -201,6 +201,27 @@ a.sc-logo img {
   display: block;
 }
 
+.toc {
+  padding: 1em;
+  background-color: #eee;
+}
+
+.toc-right {
+  float: right;
+  width: 40%;
+  margin: 0 0 0.5em 0.5em;
+}
+
+.toc ul {
+  padding: 0 0 0 1.5em;
+  margin: 0;
+}
+
+.toc a code {
+  color: #337ab7;
+  background-color: transparent;
+}
+
 pre {
   font-family: "Courier New", Monaco, Menlo, Consolas, monospace;
   background-color: #444;