Enable hooks and implement global login checking

Controllers that have to be publicly available can be
introduced in application/hooks/global.php

application/config/config.sample.php

@@ -91,7 +91,7 @@ $config['charset'] = 'UTF-8';
 | setting this variable to TRUE (boolean).  See the user guide for details.
 |
 */
-$config['enable_hooks'] = false;
+$config['enable_hooks'] = true;
 
 
 /*

application/config/hooks.php

@@ -10,6 +10,12 @@
 |
 */
 
+$hook['post_controller_constructor'] = array(
+	'class'    => '',
+	'function' => 'check_login',
+	'filename' => 'global.php',
+	'filepath' => 'hooks'
+);
 
 
 /* End of file hooks.php */

application/hooks/global.php

@@ -0,0 +1,41 @@
+<?php
+
+/*
+ * Copyright (c) 2011 Karsten Heiken <karsten@disposed.de>
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is 
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * Check if the user is logged in.
+ *
+ * If the user is not logged in, he is redirected to the login screen.
+ * Controllers that have to be globally available can be added to the array
+ * $public_controllers.
+ */
+function check_login() {
+
+	// whitelisted (publicly available) controllers
+	$public_controllers = array('auth');
+	
+	$CI = & get_instance();
+	if (!$CI->access->loggedIn() && !in_array($CI->router->class, $public_controllers)) {
+		redirect('auth/login');
+	}
+}