[Rails] Markdown support with Code Pygmentation and Embeddable Videos

README.md

Some notes

When embedding a YouTube video, just paste the link, but you need to remove a few characters.

https://www.youtube.com/watch?v=NvX9Dmxixaw

• Remove the 's' from the http protocal.
• Remove the 'www.'
• Remove the '.com'
• Remove the 'watch?v='

So you are just left with:

`http://youtube/NvX9Dmxixaw

application_helper.rb

# ./app/helper/application_helper.rb
module ApplicationHelper
  require './lib/helpers/markdown_renderer_with_special_links'
  class HTMLwithPygments < Redcarpet::Render::HTML
    def block_code(code, language)
      Pygments.highlight(code, lexer: language)
    end
  end
  def markdown(content)
    renderer = HTMLwithPygments.new
    options = {
      autolink: true,
      filter_html: true,
      hard_wrap: true,
      link_attributes: { rel: 'nofollow', target: "_blank" },
      no_intra_emphasis: true,
      disable_indented_code_blocks: true,
      fenced_code_blocks: true,
      lax_html_blocks: true,
      strikethrough: true,
      superscript: true
    }
    Redcarpet::Markdown.new(renderer, options).render(content).html_safe
    @markdown ||= Redcarpet::Markdown.new(MarkdownRendererWithSpecialLinks, autolink: true, space_after_headers: true, fenced_code_blocks: true)
    @markdown.render(content).html_safe
  end
end

index.html.haml

# example file of index displaying posts, written in HAML
- @posts.each do |post|
  %article.a-blog-post
    %h1= link_to post.title, post
    %p= markdown truncate post.content, length:300
    
# Just add 'markdown' before your 'post.content' or whatever you want formatted in Markdown

Markdown w pygments

# allows code pygmentation
gem 'pygments.rb'
# allows markdown functionality
gem 'redcarpet'

markdown_renderer_with_special_links.rb

# "./lib/helpers/markdown_renderer_with_special_links.rb
class MarkdownRendererWithSpecialLinks < Redcarpet::Render::HTML
  def autolink(link, link_type)
    case link_type
      when :url then url_link(link)
      when :email then email_link(link)
    end
  end
  def url_link(link)
    case link
      when /^http:\/\/youtube/ then youtube_link(link)
      else normal_link(link)
    end
  end
  def youtube_link(link)
    parameters_start = link.index('?')
    video_id = link[15..(parameters_start ? parameters_start-1 : -1)]
    "<iframe width=\"560\" height=\"315\" src=\"//www.youtube.com/embed/#{video_id}?rel=0\" frameborder=\"0\" allowfullscreen></iframe>"
  end
  def normal_link(link)
    "<a href=\"#{link}\">#{link}</a>"
  end
  def email_link(email)
    "<a href=\"mailto:#{email}\">#{email}</a>"
  end
end