How to refactor a Markdown conversion class to a struct

new.rb

Markdown = Struct.new(:markdown_text) do
  class << self
    def convert(text)
      Markdown.new(text).to_html
    end
  end

  def to_html(renderer_options = {hard_wrap: true, filter_html: true})
    renderer_options = {hard_wrap: true, filter_html: true}.merge renderer_options
    redcarpet_options = {
      autolink: true,
      no_intra_emphasis: true,
      fenced_code_blocks: true,
      lax_html_blocks: true,
      strikethrough: true,
      superscript: true,
      tables: true
    }

    Rails.cache.fetch ["markdown", Digest::SHA1.hexdigest(markdown_text)].join('-') do
      Redcarpet::Markdown.new(renderer.new(renderer_options), redcarpet_options).render(markdown_text)
    end
  end

private
  def renderer
    Class.new(Redcarpet::Render::HTML) do
      def block_code(code, language)
        sha = Digest::SHA1.hexdigest(code)
        Rails.cache.fetch ["code", language, sha].join('-') do
          lexer_aliases = Pygments.lexers.map { |l| l.second[:aliases] }.flatten

          pygments_options = {}
          pygments_options[:lexer] = code if lexer_aliases.include? language

          Pygments.highlight(code, pygments_options)
        end
      end
    end
  end
end

old.rb

module Markdown
  extend self
  def convert(text, options={})
    options[:engine] ||= :redcarpet_with_pygments

    sha = Digest::SHA1.hexdigest(text)

    Rails.cache.fetch ["markdown", options[:engine].to_s, sha].join('-') do
      send("engine_#{options[:engine]}".intern, text)
    end
  end

  def engine_kramdown_with_pygments(text)
    pygs = Class.new(Kramdown::Converter::Html)
    pygs.send :define_method, :convert_codeblock do |el, indent|
      attr = el.attr.dup
      lang = extract_code_language!(attr)
      if lang
        add_code_tags(
        Pygments.highlight(el.value,
        :lexer => lang,
        :options => { :encoding => 'utf-8' })
        )
      else
        "<pre><code>#{el.value}</code></pre>"
      end
    end

    pygs.send :define_method, :add_code_tags do |code|
      code = code.sub(/<pre>/,'<pre><code>')
      code = code.sub(/<\/pre>/,"</code></pre>")
    end

    self.const_set 'Pygs', pygs

    options = {
      auto_ids: false,
      input: 'gfm'
    }

    Kramdown::Document.new(text, options).to_pygs
  end

  def engine_redcarpet_with_pygments(text)
    html_with_pygments = Class.new(Redcarpet::Render::HTML)
    html_with_pygments.send :define_method, :block_code do |code, language|
      sha = Digest::SHA1.hexdigest(code)
      Rails.cache.fetch ["code", language, sha].join('-') do
        lexer_aliases = Pygments.lexers.map { |l| l.second[:aliases] }.flatten

        pygments_options = {}
        pygments_options[:lexer] = code if lexer_aliases.include? language

        Pygments.highlight(code, pygments_options)
      end
    end
    self.const_set 'HTMLwithPygments', html_with_pygments

    renderer = HTMLwithPygments.new(hard_wrap: true, filter_html: true)
    options = {
      autolink: true,
      no_intra_emphasis: true,
      fenced_code_blocks: true,
      lax_html_blocks: true,
      strikethrough: true,
      superscript: true,
      tables: true # TODO: Fix table formatting
    }
    Redcarpet::Markdown.new(renderer, options).render(text)
  end
end