1 files changed, 48 insertions, 0 deletions
diff --git a/guides/rails_guides/markdown/renderer.rb b/guides/rails_guides/markdown/renderer.rb
new file mode 100644
index 0000000000..ea3b7fc044
--- /dev/null
+++ b/guides/rails_guides/markdown/renderer.rb
@@ -0,0 +1,48 @@
+module RailsGuides
+  class Markdown
+    class Renderer < Redcarpet::Render::HTML
+      def initialize(options={})
+        super
+      end
+
+      def header(text, header_level)
+        # Always increase the heading level by, so we can use h1, h2 heading in the document
+        header_level += 1
+
+        %(<h#{header_level} id="#{dom_id(text)}">#{text}</h#{header_level}>)
+      end
+
+      def preprocess(full_document)
+        convert_notes(full_document)
+      end
+
+      private
+
+        def convert_notes(body)
+          # The following regexp detects special labels followed by a
+          # paragraph, perhaps at the end of the document.
+          #
+          # It is important that we do not eat more than one newline
+          # because formatting may be wrong otherwise. For example,
+          # if a bulleted list follows the first item is not rendered
+          # as a list item, but as a paragraph starting with a plain
+          # asterisk.
+          body.gsub(/^(TIP|IMPORTANT|CAUTION|WARNING|NOTE|INFO|TODO)[.:](.*?)(\n(?=\n)|\Z)/m) do |m|
+            css_class = case $1
+                        when 'CAUTION', 'IMPORTANT'
+                          'warning'
+                        when 'TIP'
+                          'info'
+                        else
+                          $1.downcase
+                        end
+            %Q(<div class="#{css_class}"><p>#{$2.strip}</p></div>\n)
+          end
+        end
+
+        def dom_id(text)
+          text.downcase.gsub(/[^a-z0-9]+/, '-').strip
+        end
+    end
+  end
+end