3 files changed, 98 insertions, 3 deletions
diff --git a/guides/rails_guides/generator.rb b/guides/rails_guides/generator.rb
index 230bebf3bb..ee97c37fac 100644
--- a/guides/rails_guides/generator.rb
+++ b/guides/rails_guides/generator.rb
@@ -65,7 +65,7 @@ module RailsGuides
   class Generator
     attr_reader :guides_dir, :source_dir, :output_dir, :edge, :warnings, :all
 
-    GUIDES_RE = /\.(?:textile|erb)$/
+    GUIDES_RE = /\.(?:textile|erb|md|markdown)$/
 
     def initialize(output=nil)
       set_flags_from_environment
@@ -171,8 +171,8 @@ module RailsGuides
     end
 
     def output_file_for(guide)
-      if guide =~/\.textile$/
-        guide.sub(/\.textile$/, '.html')
+      if guide =~ /\.(textile|markdown|md)$/
+        guide.sub(/\.(textile|markdown|md)$/, '.html')
       else
         guide.sub(/\.erb$/, '')
       end
@@ -201,6 +201,11 @@ module RailsGuides
           # Generate the special pages like the home.
           # Passing a template handler in the template name is deprecated. So pass the file name without the extension.
           result = view.render(:layout => layout, :formats => [$1], :file => $`)
+        elsif guide =~ /\.(md|markdown)$/
+          body = File.read(File.join(source_dir, guide))
+          result = RailsGuides::Markdown.new(view, layout).render(body)
+
+          warn_about_broken_links(result) if @warnings
         else
           body = File.read(File.join(source_dir, guide))
           body = set_header_section(body, view)
diff --git a/guides/rails_guides/markdown.rb b/guides/rails_guides/markdown.rb
new file mode 100644
index 0000000000..a56d0d2d85
--- /dev/null
+++ b/guides/rails_guides/markdown.rb
@@ -0,0 +1,42 @@
+require 'redcarpet'
+require 'nokogiri'
+require 'rails_guides/markdown/renderer'
+
+module RailsGuides
+  class Markdown
+    def initialize(view, layout)
+      @view = view
+      @layout = layout
+    end
+
+    def render(body)
+      @header, _, @body = body.partition(/^\-{40,}$/)
+      render_header
+      render_body
+    end
+
+    private
+      def engine
+        @engine ||= Redcarpet::Markdown.new(Renderer, {
+          no_intra_emphasis: true,
+          fenced_code_blocks: true,
+          autolink: true,
+          strikethrough: true,
+          superscript: true
+        })
+      end
+
+      def render_header
+        header_content = engine.render(@header)
+        @view.content_for(:header_section) { header_content.html_safe }
+
+        @view.content_for(:page_title) do
+          "Ruby on Rails Guides: #{Nokogiri::HTML(header_content).at(:h2).text}".html_safe
+        end
+      end
+
+      def render_body
+        @view.render(:layout => @layout, :text => engine.render(@body))
+      end
+  end
+end
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