# include the MD5 gem, this should be part of a standard ruby install
 require 'digest/md5'
 
 module Jekyll
 
 	class Gravatar < Liquid::Tag
 
                 def initialize(tag_name, size, token)
                   super
                   @size = size.strip
                 end
 
 		def render(context)
 			# get the site config variables
 			site_config = context.registers[:site].config
 
 			# get the email address from the site config
 			email_address = site_config['gravatar_email']
 			# change the email address to all lowercase
 			email_address = email_address.downcase
 
 			# create an md5 hash from the email address
 			gravatar_hash = Digest::MD5.hexdigest(email_address)
 
 			# compile the full Gravatar URL
 			image_src = "http://www.gravatar.com/avatar/#{gravatar_hash}"
 			
                         # append size query to URL if provided in tag
                         unless @size.empty?
                           image_src = image_src+"?s=#{@size}"
                         end
 			
 			# output the full Gravatar URL
 			image_src
 		end
 
 	end
 	
 end
 
 # register the "gravatar_image" tag
 Liquid::Template.register_tag('gravatar_image', Jekyll::Gravatar)