From 85be8375c7483898cefb4fd6dbbb752922dde573 Mon Sep 17 00:00:00 2001
From: Tim Hunt <T.J.Hunt@open.ac.uk>
Date: Thu, 22 Dec 2011 18:02:24 +0000
Subject: [PATCH] MDL-30766 mod_quiz: fix edge cases of repaginate function.

---
 mod/quiz/locallib.php                | 27 ++++++++++++++---------
 mod/quiz/simpletest/testlocallib.php | 32 ++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/mod/quiz/locallib.php b/mod/quiz/locallib.php
index 3d4858133ec..21b5aaf7a4e 100644
--- a/mod/quiz/locallib.php
+++ b/mod/quiz/locallib.php
@@ -246,22 +246,29 @@ function quiz_number_of_questions_in_quiz($layout) {
  * @return string the new layout string
  */
 function quiz_repaginate($layout, $perpage, $shuffle = false) {
-    $layout = str_replace(',0', '', $layout); // remove existing page breaks
-    $questions = explode(',', $layout);
+    $questions = quiz_questions_in_quiz($layout);
+    if (!$questions) {
+        return '0';
+    }
+
+    $questions = explode(',', quiz_questions_in_quiz($layout));
     if ($shuffle) {
         shuffle($questions);
     }
-    $i = 1;
-    $layout = '';
+
+    $onthispage = 0;
+    $layout = array();
     foreach ($questions as $question) {
-        if ($perpage and $i > $perpage) {
-            $layout .= '0,';
-            $i = 1;
+        if ($perpage and $onthispage >= $perpage) {
+            $layout[] = 0;
+            $onthispage = 0;
         }
-        $layout .= $question.',';
-        $i++;
+        $layout[] = $question;
+        $onthispage += 1;
     }
-    return $layout.'0';
+
+    $layout[] = 0;
+    return implode(',', $layout);
 }
 
 /// Functions to do with quiz grades //////////////////////////////////////////
diff --git a/mod/quiz/simpletest/testlocallib.php b/mod/quiz/simpletest/testlocallib.php
index 25d0e032cea..13117e1394a 100644
--- a/mod/quiz/simpletest/testlocallib.php
+++ b/mod/quiz/simpletest/testlocallib.php
@@ -96,6 +96,38 @@ class quiz_locallib_test extends UnitTestCase {
         $this->assertEqual(quiz_clean_layout('0,1,0,0,2,0', true), '1,0,2,0');
     }
 
+    public function test_quiz_repaginate() {
+        // Test starting with 1 question per page.
+        $this->assertEqual(quiz_repaginate('1,0,2,0,3,0', 0), '1,2,3,0');
+        $this->assertEqual(quiz_repaginate('1,0,2,0,3,0', 3), '1,2,3,0');
+        $this->assertEqual(quiz_repaginate('1,0,2,0,3,0', 2), '1,2,0,3,0');
+        $this->assertEqual(quiz_repaginate('1,0,2,0,3,0', 1), '1,0,2,0,3,0');
+
+        // Test starting with all on one page page.
+        $this->assertEqual(quiz_repaginate('1,2,3,0', 0), '1,2,3,0');
+        $this->assertEqual(quiz_repaginate('1,2,3,0', 3), '1,2,3,0');
+        $this->assertEqual(quiz_repaginate('1,2,3,0', 2), '1,2,0,3,0');
+        $this->assertEqual(quiz_repaginate('1,2,3,0', 1), '1,0,2,0,3,0');
+
+        // Test single question case.
+        $this->assertEqual(quiz_repaginate('100,0', 0), '100,0');
+        $this->assertEqual(quiz_repaginate('100,0', 1), '100,0');
+
+        // No questions case.
+        $this->assertEqual(quiz_repaginate('0', 0), '0');
+
+        // Test empty pages are removed.
+        $this->assertEqual(quiz_repaginate('1,2,3,0,0,0', 0), '1,2,3,0');
+        $this->assertEqual(quiz_repaginate('1,0,0,0,2,3,0', 0), '1,2,3,0');
+        $this->assertEqual(quiz_repaginate('0,0,0,1,2,3,0', 0), '1,2,3,0');
+
+        // Test shuffle option.
+        $this->assertTrue(in_array(quiz_repaginate('1,2,0', 0, true),
+                array('1,2,0', '2,1,0')));
+        $this->assertTrue(in_array(quiz_repaginate('1,2,0', 1, true),
+                array('1,0,2,0', '2,0,1,0')));
+    }
+
     public function test_quiz_rescale_grade() {
         $quiz = new stdClass();
         $quiz->decimalpoints = 2;