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require 'digest/md5'

require 'cgi'

module GravatarHelper

  # These are the options that control the default behavior of the public

  # methods. They can be overridden during the actual call to the helper,

  # or you can set them in your environment.rb as such:

  #

  #   # Allow racier gravatars

  #   GravatarHelper::DEFAULT_OPTIONS[:rating] = 'R'

  #

  DEFAULT_OPTIONS = {

    # The URL of a default image to display if the given email address does

    # not have a gravatar.

    :default => nil,

    # The default size in pixels for the gravatar image (they're square).

    :size => 50,

    # The maximum allowed MPAA rating for gravatars. This allows you to 

    # exclude gravatars that may be out of character for your site.

    :rating => 'PG',

    # The alt text to use in the img tag for the gravatar.  Since it's a

    # decorational picture, the alt text should be empty according to the

    # XHTML specs.

    :alt => '',

    # The title text to use for the img tag for the gravatar.

    :title => '',

    # The class to assign to the img tag for the gravatar.

    :class => 'gravatar',

    # Whether or not to display the gravatars using HTTPS instead of HTTP

    :ssl => false,

  }

  # The methods that will be made available to your views.

  module PublicMethods

    # Return the HTML img tag for the given user's gravatar. Presumes that 

    # the given user object will respond_to "email", and return the user's

    # email address.

    def gravatar_for(user, options={})

      gravatar(user.email, options)

    end

    # Return the HTML img tag for the given email address's gravatar.

    def gravatar(email, options={})

      src = h(gravatar_url(email, options))

      options = DEFAULT_OPTIONS.merge(options)

      [:class, :alt, :size, :title].each { |opt| options[opt] = h(options[opt]) }

      "<img class=\"#{options[:class]}\" alt=\"#{options[:alt]}\" title=\"#{options[:title]}\" width=\"#{options[:size]}\" height=\"#{options[:size]}\" src=\"#{src}\" />"

    end

    # Returns the base Gravatar URL for the given email hash. If ssl evaluates to true,

    # a secure URL will be used instead. This is required when the gravatar is to be 

    # displayed on a HTTPS site.

    def gravatar_api_url(hash, ssl=false)

      if ssl

        "https://secure.gravatar.com/avatar/#{hash}"

      else

        "http://www.gravatar.com/avatar/#{hash}"

      end

    end

    # Return the gravatar URL for the given email address.

    def gravatar_url(email, options={})

      email_hash = Digest::MD5.hexdigest(email)

      options = DEFAULT_OPTIONS.merge(options)

      options[:default] = CGI::escape(options[:default]) unless options[:default].nil?

      gravatar_api_url(email_hash, options.delete(:ssl)).tap do |url|

        opts = []

        [:rating, :size, :default].each do |opt|

          unless options[opt].nil?

            value = h(options[opt])

            opts << [opt, value].join('=')

          end

        end

        url << "?#{opts.join('&')}" unless opts.empty?

      end

    end

  end

end