link_filter.rb

module LinkFilter
  def gen_link(link)
    if link.start_with?('http://', 'https://', '#')
      link
    elsif link.start_with?('site.data.links.')
      desired_link = link.slice('site.data.links.'.length, link.length)
      @context.registers[:site].data['links'][desired_link]
    else
      baseurl = @context.registers[:site].baseurl
      jekyll_link = Jekyll::Tags::Link.send(
        :new,
        Jekyll::Tags::Link.tag_name,
        link,
        Liquid::ParseContext.new
      ).render(@context)
      "#{baseurl}#{jekyll_link}"
    end
  end
end