properly insert CAS as another auth method

app/controllers/application_controller.rb

@@ -30,7 +30,13 @@ class ApplicationController < ActionController::Base
   exempt_from_layout /\.js\.erb$/
 
   if ( SITE_CONFIG['authentication_schemes'].include? 'cas')
-    before_filter CASClient::Frameworks::Rails::Filter
+    # This will allow the user to view the index page without authentication
+    # but will process CAS authentication data if the user already
+    # has an SSO session open.
+    before_filter CASClient::Frameworks::Rails::GatewayFilter, :only => :login
+
+    # This requires the user to be authenticated for viewing allother pages.
+    before_filter CASClient::Frameworks::Rails::Filter, :except => :login
   end
   before_filter :set_session_expiration
   before_filter :set_time_zone

app/controllers/login_controller.rb

@@ -6,11 +6,15 @@ class LoginController < ApplicationController
   skip_before_filter :login_required
   before_filter :login_optional
   before_filter :get_current_user
-  
+
   def login
+    if cas_enabled?
+      @username = session[:cas_user]
+      @login_url = CASClient::Frameworks::Rails::Filter.login_url(self)
+    end
     if openid_enabled? && using_open_id?
       login_openid
-    elsif cas_enabled?
+    elsif cas_enabled? && session[:cas_user]
       login_cas
     else
       @page_title = "TRACKS::Login"
@@ -136,7 +140,7 @@ class LoginController < ApplicationController
         end
         redirect_back_or_home
       else
-        notify :warning, "Sorry, no user by that identity URL exists (#{identity_url})"
+        notify :warning, "Sorry, no user by that CAS username exists (#{session[:cas_user]})"
       end
     else
       notify :warning, result.message