url2png.rb

# place this file in _plugins/url2png.rb

# add this to your _config.yml
# url2png:
#   apikey: <apikey>
#   secret: <secret>

require 'liquid'
require 'cgi' unless defined?(CGI)
require 'digest' unless defined?(Digest)


class Url2png < Liquid::Tag

  @@URL2PNG_PARAMETERS = ['viewport', 'thumbnail_max_width', 'fullpage']
  # more options available at url2png.com/docs
  
  def initialize(tag_name, text, tokens)
    super

    tokens = text.split /\,\s/

    @url = tokens.shift

    raise "No URL provided" if @url.nil?
    raise "TODO: Relative URLs are tricky with Jekyll..." if @url =~ /^\//

    @options = {}
    tokens.each do |arg|
      key, value = arg.split /:/
      value ||= "true"
      @options[key.strip] = value.strip
    end

    @options['url'] = @url

  end

  def render(context)

    config = context.registers[:site].config['url2png']
    @apikey = config['apikey']
    @secret = config['secret']

    raise "Url2png apikey/token required" if @apikey.nil? or @secret.nil?

    generate_request

  end

  private

  def generate_request

    query_string = @options.sort.map { |k,v| "#{CGI::escape(k.to_s)}=#{CGI::escape(v.to_s)}" }.join("&")
    token = Digest::MD5.hexdigest(query_string + @secret)

    "https://api.url2png.com/v6/#{@apikey}/#{token}/png/?#{query_string}"

  end

  Liquid::Template.register_tag "url2png", self

end