store meta values in cookies on client

#290, https://github.com/MartijnR/enketo-core/issues/159, https://github.com/MartijnR/enketo-core/issues/35

Code_Igniter/application/controllers/webform.php

@@ -25,7 +25,7 @@ function __construct()
         parent::__construct();
         $this->load->helper(array('subdomain','url', 'form'));
         $this->load->model('Survey_model','',TRUE);
-        $this->load->library('encrypt');
+        $this->load->library(array('encrypt', 'meta'));
         $sub = get_subdomain();
         $suf = $this->Survey_model->ONLINE_SUBDOMAIN_SUFFIX;
         $this->subdomain = ($this->Survey_model->has_offline_launch_enabled()) 
@@ -39,7 +39,7 @@ function __construct()
             $this->xsl_version_prev = (isset($form_props['xsl_version'])) ? $form_props['xsl_version'] : NULL; 
         }
         $this->iframe = ( $this->input->get('iframe', TRUE) == 'true' );
-
+       
         if ($this->config->item('auth_support')) {
             $this->load->add_package_path(APPPATH.'third_party/form_auth');
         }
@@ -48,6 +48,7 @@ function __construct()
             $this->load->add_package_path(APPPATH.'third_party/account');
         }
         $this->load->library('account');
+
         log_message('debug', 'Webform Controller Initialized');
     }
 
@@ -295,6 +296,9 @@ private function _get_form()
         $this->credentials = $this->form_auth->get_credentials($s);
         $this->Form_model->setup($this->server_url, $this->form_id, $this->credentials, $this->form_hash_prev, $this->xsl_version_prev, $this->media_hash_prev);
 
+        $uid = ($this->credentials) ? $this->credentials['username'] : NULL;
+        $this->meta->setMeta($uid);
+
         if($this->Form_model->requires_auth()) {
             log_message('debug', "AUTHENTICATION REQUIRED");
             $form = new stdClass();

Code_Igniter/application/libraries/Meta.php

@@ -0,0 +1,72 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); 
+/**
+ * Meta Class
+ *
+ * Deals with Meta values that are best generated at server
+ *
+ * @author          Martijn van de Rijdt
+ * @license         see link
+ * @link            https://github.com/MartijnR/enketo
+ */
+class Meta {
+
+    private $CI;
+    private $cookie_prefix = '__enketo_meta_';
+
+    public function __construct()
+    {
+        $this->CI =& get_instance();
+        $this->CI->load->helper('url');
+        $this->domain = $this->get_domain();
+        log_message('debug', 'Meta library initialized');
+    }
+
+    public function setMeta($username = NULL) {
+
+        log_message('debug', 'setting meta with username:'.$username);
+        if ($username && !$this->getCookie('uid')) {
+            $this->setCookie( 'uid', $this->domain.':'.$username);
+        }
+
+        if (!$this->getCookie('deviceid')) {
+            $this->setCookie('deviceid', $this->domain.':'.$this->generate_deviceid(), TRUE);
+        }
+
+    }
+
+    private function setCookie($name, $value, $expire_as_late_as_possible = FALSE )
+    {
+        if (empty($name) || empty($value)) {
+            return;
+        }
+        $cookie = array(
+            'name'   => $this->cookie_prefix . $name,
+            'value'  => $value,
+            'expire' => ($expire_as_late_as_possible) ? 10 * 365 * 24 * 60 * 60 : 7 * 24 * 60 *60,
+            'domain' => $this->CI->config->item('cookie_domain'),
+            'path'   => $this->CI->config->item('cookie_path'),
+            'prefix' => $this->CI->config->item('cookie_prefix'),
+            'secure' => $this->CI->config->item('cookie_secure')
+        );
+        $this->CI->input->set_cookie($cookie);
+    }
+
+    private function getCookie($name)
+    {
+        return $this->CI->input->cookie($this->cookie_prefix . $name, TRUE);
+    }
+
+    private function generate_deviceid()
+    {
+        $this->CI->load->helper('string');
+        return random_string('alnum', 16);
+    }
+
+    private function get_domain() 
+    {
+        $base_url = base_url();
+        return substr( $base_url, strpos($base_url, '://') + 3 );
+    }
+}
+
+/* End of file Meta.php */