module SimpleFlickr
  class Authentication
    
    AuthenticationService = 'http://www.flickr.com/services/auth/?'
    attr_reader :permission
    
    def initialize(options)
      # This class must be subclassed
      if self.class.name =~ /::Authentication$/
        raise "The Authentication class must be subclassed"
      end
      
      unless options.key?(:api_key) && options.key?(:secret)
        raise ArgumentError.new("Options should contain at least :api_key and :secret")
      end
      
      @permission = (options[:permission] || :read).to_sym
      @default_params = { :api_key => options[:api_key], :secret => options[:secret] }
    end
    
    def token_url(frob)
      params = default_params.merge(:frob => frob, :method => 'flickr.auth.getToken')
      url_for(params)
    end
    
    def get_token_from_frob(frob)
      response = HTTP.start do |flickr|
        flickr.get(token_url(frob))
      end
      doc = Hpricot::XML response.body
      doc.at('token').inner_text
    end
    
    private
      attr_reader :default_params
  end
end