trulia/hologram

class ExampleMarkdownRenderer < Redcarpet::Render::HTML
  def block_code(code, language)
    if language and language.include?('example')
      if language.include?('js')
        # first actually insert the code in the docs so that it will run and make our example work.
        '<script>' + code + '</script>
        <div class="codeBlock jsExample">' + Pygments.highlight(code) + '</div>'
      else
        '<div class="codeExample">' + '<div class="exampleOutput">' + render_html(code, language) + '</div>' + '<div class="codeBlock">' + Pygments.highlight(code, :lexer => get_lexer(language)) + '</div>' + '</div>'
      end
    else
      '<div class="codeBlock">' + Pygments.highlight(code) + '</div>'
    end
  end

  private
  def render_html(code, language)
    case language
      when 'haml_example'
        safe_require('haml', language)
        return Haml::Engine.new(code.strip).render(template_rendering_scope, {})
      else
        code
    end
  end

  def template_rendering_scope
    Object.new
  end

  def get_lexer(language)
    case language
      when 'haml_example'
        'haml'
      else
        'html'
    end
  end

  def safe_require(templating_library, language)
    begin
      require templating_library
    rescue LoadError
      raise "#{templating_library} must be present for you to use #{language}"
    end
  end
end