module ApplicationHelper

def gravatar_url(email, options={})
  # Default to highest rating. Rating can be one of G, PG, R X.
  options[:rating] ||= "G"
  # Default size of the image.
  options[:size] ||= "32px"
  # Default image url to be used when no gravatar is found
  # or when an image exceeds the rating parameter.
  local_avatar_url = "/images/admin/avatar_#{([options[:size].to_i] * 2).join('x')}.png"
  default_avatar_url = "#{request.protocol}#{request.host_with_port}#{ActionController::Base.relative_url_root}#{local_avatar_url}"
  options[:default] ||= default_avatar_url
  unless email.blank?
    # Build the Gravatar url.
    url = '//gravatar.com/avatar/'
    url << "#{Digest::MD5.new.update(email)}?"
    url << "rating=#{options[:rating]}" if options[:rating]
    url << "&size=#{options[:size]}" if options[:size]
    url << "&default=#{options[:default]}" if options[:default]
    # Test the Gravatar url
    require 'open-uri'
    begin; open "http:#{url}", :proxy => true
    rescue; local_avatar_url
    else; url
    end
  else
    local_avatar_url
  end
end