Markdown to Html with code highlight

README.md

Have a model with this attributes

• md
• html

Usage

class Article < ActiveRecord::Base
  include MdToHtml
end

Gemfile

gem 'redcarpet'
gem 'pygmentize'

md_to_html.rb

require 'digest/md5'

module MdToHtml
  extend ActiveSupport::Concern

 included do
   before_save :convert_md
 end

  private

	def convert_md
		markdown  = Redcarpet::Markdown.new(PygmentizeHTML, :autolink => true, :space_after_headers => true, :fenced_code_blocks => true)
		self.html = markdown.render(gfm(self.md))
	end

	# from https://help.github.com/articles/github-flavored-markdown
	def gfm(text)
	  # Extract pre blocks
	  extractions = {}
	  text.gsub!(%r{<pre>.*?</pre>}m) do |match|
	    md5 = Digest::MD5.hexdigest(match)
	    extractions[md5] = match
	    "{gfm-extraction-#{md5}}"
	  end
	 
	  # prevent foo_bar_baz from ending up with an italic word in the middle
	  text.gsub!(/(^(?! {4}|\t)\w+_\w+_\w[\w_]*)/) do |x|
	    x.gsub('_', '\_') if x.split('').sort.to_s[0..1] == '__'
	  end
	 
	  # in very clear cases, let newlines become <br /> tags
	  text.gsub!(/^[\w\<][^\n]*\n+/) do |x|
	    x =~ /\n{2}/ ? x : (x.strip!; x << "  \n")
	  end
	 
	  # Insert pre block extractions
	  text.gsub!(/\{gfm-extraction-([0-9a-f]{32})\}/) do
	    "\n\n" + extractions[$1]
	  end
	 
	  text
	end
end