Upgrading to Redcarpet v2.0 with highlighting of code blocks with Albino/Pygments

application_helper.rb

module ApplicationHelper
  def markdown(text, *renderer)      
    rndr_flags = { 
      hard_wrap:       true,
      gh_blockcode:    true,
      safe_links_only: true,
      filter_html:     true
    }
    case renderer[0]
    when :authored
      rndr_flags[:filter_html] = false
    else
      rndr_flags.merge({:no_images => true, :no_styles => true})
    end
    rndr = HTMLwithAlbino.new(rndr_flags)
    redcarpet = Redcarpet::Markdown.new(rndr, :space_after_headers => true,
      :fenced_code_blocks => true, :autolink => true, :no_intra_emphasis => true,
      :strikethrough => true, :superscripts => true)
    redcarpet.render(text).html_safe
  end  
end

# create a custom renderer that allows highlighting of code blocks
class HTMLwithAlbino < Redcarpet::Render::HTML      
  def block_code(code, language)
    Albino.colorize(code, language)
  end
end

Calling markdown without any arguments will assume publicly created content, hence, it filters out as much as possible; still doing Albino.colorize() instead of Albino.safe_colorize() as I haven't upgraded it yet.

Thanks to @clooth for https://gist.github.com/1472055