Dev: Add new column 'seed' to dynamic survey table

application/helpers/admin/activate_helper.php

@@ -273,6 +273,9 @@ function activateSurvey($iSurveyID, $simulate = false)
     {
         switch($aRow['type'])
         {
+            case 'seed':
+                $aTableDefinition[$aRow['fieldname']] = "string(31)";
+                break;
             case 'startlanguage':
                 $aTableDefinition[$aRow['fieldname']] = "string(20) NOT NULL";
                 break;

application/helpers/common_helper.php

@@ -1810,6 +1810,14 @@ function createFieldMap($surveyid, $style='short', $force_refresh=false, $questi
         $fieldmap["startlanguage"]['group_name']="";
     }
 
+    $fieldmap['seed'] = array('fieldname' => 'seed', 'sid' => $surveyid, 'type' => 'seed', 'gid' => '', 'qid' => '', 'aid' => '');
+    if ($style == 'full')
+    {
+        $fieldmap["seed"]['title']="";
+        $fieldmap["seed"]['question']=gT("Seed");
+        $fieldmap["seed"]['group_name']="";
+    }
+
     //Check for any additional fields for this survey and create necessary fields (token and datestamp and ipaddr)
     $prow = Survey::model()->findByPk($surveyid)->getAttributes(); //Checked
 

application/helpers/frontend_helper.php

@@ -11,6 +11,9 @@
 * See COPYRIGHT.php for copyright notices and details.
 */
 
+// TODO: Why needed?
+require_once(Yii::app()->basePath . '/libraries/MersenneTwister.php');
+
 function loadanswers()
 {
     Yii::trace('start', 'survey.loadanswers');
@@ -1060,6 +1063,8 @@ function buildsurveysession($surveyid,$preview=false)
     $qtypes=getQuestionTypeList('','array');
     $fieldmap=createFieldMap($surveyid,'full',true,false,$_SESSION['survey_'.$surveyid]['s_lang']);
 
+    $seed = ls\mersenne\getSeed($surveyid, $preview);
+
     // Randomization groups for groups
     list($fieldmap, $randomized1) = randomizationGroup($surveyid, $fieldmap, $preview);
 

application/libraries/MersenneTwister.php

@@ -0,0 +1,109 @@
+<?php
+
+namespace ls\mersenne;
+
+/**
+ * Get seed for this answer
+ * If there is no seed create a new one
+ * @param int $surveyId
+ * @param boolean $preview
+ * @return int
+ */
+function getSeed($surveyId, $preview)
+{
+    $columnNames = \SurveyDynamic::model($surveyId)->getTableSchema()->getColumnNames();
+    traceVar($columnNames);
+    // Get columns
+    // Check if we have seed column
+    // Yes: check value
+    //   have value, use it
+    //   no value, generate new seed
+    // No: create column
+    //   generate seed
+    //   insert seed
+    // Use seed to instantiate twister
+}
+
+/**
+ * Shuffle with seed
+ * @param array $arr
+ * @param $seed
+ * @return array
+ */
+function shuffle($arr, $seed=-1)
+{
+    if ( $seed == -1 ) return $arr;
+    $mt = new MersenneTwister($seed);
+    $new = $arr;
+    for ($i = count($new) - 1; $i > 0; $i--)
+    {
+        $j = $mt->getNext(0,$i);
+        $tmp = $new[$i];
+        $new[$i] = $new[$j];
+        $new[$j] = $tmp;
+    }
+    return $new;
+}
+
+/**
+ * Custom random algorithm to get consistent behaviour between PHP versions.
+ *
+ * Copied from: http://www.dr-chuck.com/csev-blog/2015/09/a-mersenne_twister-implementation-in-php/
+ */
+class MersenneTwister
+{
+  private $state = array ();
+  private $index = 0;
+
+  public function __construct($seed = null) {
+    if ($seed === null)
+      $seed = mt_rand();
+
+    $this->setSeed($seed);
+  }
+
+  public function setSeed($seed) {
+    $this->state[0] = $seed & 0xffffffff;
+
+    for ($i = 1; $i < 624; $i++) {
+      $this->state[$i] = (((0x6c078965 * ($this->state[$i - 1] ^ ($this->state[$i - 1] >> 30))) + $i)) & 0xffffffff;
+    }
+
+    $this->index = 0;
+  }
+
+  private function generateTwister() {
+    for ($i = 0; $i < 624; $i++) {
+      $y = (($this->state[$i] & 0x1) + ($this->state[$i] & 0x7fffffff)) & 0xffffffff;
+      $this->state[$i] = ($this->state[($i + 397) % 624] ^ ($y >> 1)) & 0xffffffff;
+
+      if (($y % 2) == 1) {
+        $this->state[$i] = ($this->state[$i] ^ 0x9908b0df) & 0xffffffff;
+      }
+    }
+  }
+
+  public function getNext($min = null, $max = null) {
+    if (($min === null && $max !== null) || ($min !== null && $max === null))
+      throw new Exception('Invalid arguments');
+
+    if ($this->index === 0) {
+      $this->generateTwister();
+    }
+
+    $y = $this->state[$this->index];
+    $y = ($y ^ ($y >> 11)) & 0xffffffff;
+    $y = ($y ^ (($y << 7) & 0x9d2c5680)) & 0xffffffff;
+    $y = ($y ^ (($y << 15) & 0xefc60000)) & 0xffffffff;
+    $y = ($y ^ ($y >> 18)) & 0xffffffff;
+
+    $this->index = ($this->index + 1) % 624;
+
+    if ($min === null && $max === null)
+      return $y;
+
+    $range = abs($max - $min);
+
+    return min($min, $max) + ($y % ($range + 1));
+  }
+}

application/models/SurveyDynamic.php

@@ -540,7 +540,7 @@ public function getTokenForGrid()
     // Get the list of default columns for surveys
     public function getDefaultColumns()
     {
-        return array('id', 'token', 'submitdate', 'lastpage','startlanguage', 'completed');
+        return array('id', 'token', 'submitdate', 'lastpage','startlanguage', 'completed', 'seed');
     }
 
     /**