media_embed.rb

#!/usr/bin/env ruby
## Deal with media embed output format
require "paru/filter"
require 'addressable/uri'
require "youtube_id"

format = if ARGV.first.nil? then "unknown" else ARGV.first end
warn "Filter :: Rewrite media embed code for output format: #{format}"

Paru::Filter.run do

	with "Para" do |paragraph|
		
		if paragraph.inner_markdown.start_with?('::') then 
			command, type, *args =  paragraph.inner_markdown.gsub(/\s+\r\n?/,'').strip.split('::').drop(1) #=> remove first blank element. Sure there's another way...
			if "insert" == command and "media" == type then 
				if args.length == 1 then
					link = args.first.lstrip.chop
					# https://stackoverflow.com/questions/9268407/how-to-convert-markdown-style-links-using-regex
					title, url  = link.split(%r{\[([^\]]+)\]\(([^)]+)\)}x).drop(1) #=> sure is there another way to parse this

					uri = Addressable::URI.parse url
					if "www.youtube.com" == uri.host then 
						id_youtube =  YoutubeID.from(url)
					end

					if "html" == format then
						html_embed = Paru::PandocFilter::RawBlock.new(["html", "<iframe width=\"560\" height=\"315\" src=\"https:\/\/www.youtube.com\/embed\/#{id_youtube}\" frameborder=\"0\" allowfullscreen><\/iframe><p>#{title}<\/p>"]) #=> need to find another way to generate html code
						paragraph.parent.replace(paragraph, html_embed) #=> replace it html code

					elsif "latex" == format then 
						latex_embed = Paru::PandocFilter::RawBlock.new(["latex", "\\begin{pspicture}(1in,1in) \\psbarcode{#{url}}{}{qrcode} \\end{pspicture}"])
						paragraph.parent.replace(paragraph, latex_embed)
					end
				end
			end 				

		end
	end
end