questiontype.php

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<?php  // $Id: questiontype.php,v 1.12.2.9 2009/02/17 06:14:48 tjhunt Exp $
/**
 * Class for the random question type.
 *
 * The random question type does not have any options. When the question is
 * attempted, it picks a question at random from the category it is in (and
 * optionally its subcategories). For details see create_session_and_responses.
 * Then all other method calls as delegated to that other question.
 *
 * @package questionbank
 * @subpackage questiontypes
 */
class random_qtype extends default_questiontype {
    var $selectmanual;
    var $excludedqtypes = null;
    var $manualqtypes = null;

    function random_qtype() {
        $this->selectmanual = get_config('qtype_random', 'selectmanual');
    }

    // Caches questions available as randoms sorted by category
    // This is a 2-d array. The first key is question category, and the
    // second is whether to include subcategories.
    var $catrandoms = array();

    function name() {
        return 'random';
    }

    function menu_name() {
        // Don't include this question type in the 'add new question' menu.
        return false;
    }

    function is_manual_graded() {
        return $this->selectmanual;
    }

    function is_question_manual_graded($question, $otherquestionsinuse) {
        if (!$this->selectmanual) {
            return false;
        }
        // We take our best shot at working whether a particular question is manually
        // graded follows: We look to see if any of the questions that this random
        // question might select if of a manually graded type. If a category contains
        // a mixture of manual and non-manual questions, and if all the attempts so
        // far selected non-manual ones, this will give the wrong answer, but we
        // don't care. Even so, this is an expensive calculation!
        $this->init_qtype_lists();
        if (!$this->manualqtypes) {
            return false;
        }
        if ($question->questiontext) {
            $categorylist = question_categorylist($question->category);
        } else {
            $categorylist = $question->category;
        }
        return record_exists_select('question',
                "category IN ($categorylist)
                     AND parent = 0
                     AND hidden = 0
                     AND id NOT IN ($otherquestionsinuse)
                     AND qtype IN ($this->manualqtypes)");
    }

    function is_usable_by_random() {
        return false;
    }

    /**
     * This method needs to be called before the ->excludedqtypes and
     *      ->manualqtypes fields can be used.
     */
    function init_qtype_lists() {
        global $QTYPES;
        if (is_null($this->excludedqtypes)) {
            $excludedqtypes = array();
            $manualqtypes = array();
            foreach ($QTYPES as $qtype) {
                $quotedname = "'" . $qtype->name() . "'";
                if (!$qtype->is_usable_by_random()) {
                    $excludedqtypes[] = $quotedname;
                } else if ($this->selectmanual && $qtype->is_manual_graded()) {
                    $manualqtypes[] = $quotedname;
                }
            }
            $this->excludedqtypes = implode(',', $excludedqtypes);
            $this->manualqtypes = implode(',', $manualqtypes);
        }
    }

    function get_question_options(&$question) {
        // Don't do anything here, because the random question has no options.
        // Everything is handled by the create- or restore_session_and_responses
        // functions.
        return true;
    }

    /**
     * Random questions always get a question name that is Random (cateogryname).
     * This function is a centralised place to calculate that, given the category.
     */
    function question_name($category) {
        return get_string('random', 'quiz') .' ('. $category->name .')';
    }

    function save_question($question, $form, $course) {
        $form->name = '';
        // Name is not a required field for random questions, but parent::save_question
        // Assumes that it is.
        return parent::save_question($question, $form, $course);
    }

    function save_question_options($question) {
        // No options, as such, but we set the parent field to the question's
        // own id. Setting the parent field has the effect of hiding this
        // question in various places.
        $updateobject = new stdClass;
        $updateobject->id = $question->id;
        $updateobject->parent = $question->id;

        // We also force the question name to be 'Random (categoryname)'.
        if (!$category = get_record('question_categories', 'id', $question->category)) {
            error('Could retrieve question category');
        }
        $updateobject->name = addslashes($this->question_name($category));
        return update_record('question', $updateobject);
    }

    /**
     * Get all the usable questions from a particular question category.
     *
     * @param integer $categoryid the id of a question category.
     * @param boolean whether to include questions from subcategories.
     * @param string $questionsinuse comma-separated list of question ids to exclude from consideration.
     * @return array of question records.
     */
    function get_usable_questions_from_category($categoryid, $subcategories, $questionsinuse) {
        $this->init_qtype_lists();
        if ($subcategories) {
            $categorylist = question_categorylist($categoryid);
        } else {
            $categorylist = $categoryid;
        }
        if (!$catrandoms = get_records_select('question',
                "category IN ($categorylist)
                     AND parent = 0
                     AND hidden = 0
                     AND id NOT IN ($questionsinuse)
                     AND qtype NOT IN ($this->excludedqtypes)", '', 'id')) {
            $catrandoms = array();
        }
        return $catrandoms;
    }

    function create_session_and_responses(&$question, &$state, $cmoptions, $attempt) {
        global $QTYPES;
        // Choose a random question from the category:
        // We need to make sure that no question is used more than once in the
        // quiz. Therfore the following need to be excluded:
        // 1. All questions that are explicitly assigned to the quiz
        // 2. All random questions
        // 3. All questions that are already chosen by an other random question
        // 4. Deleted questions
        if (!isset($cmoptions->questionsinuse)) {
            $cmoptions->questionsinuse = $attempt->layout;
        }

        if (!isset($this->catrandoms[$question->category][$question->questiontext])) {
            $catrandoms = $this->get_usable_questions_from_category($question->category,
                    $question->questiontext == "1", $cmoptions->questionsinuse);
            $this->catrandoms[$question->category][$question->questiontext] = swapshuffle_assoc($catrandoms);
        }

        while ($wrappedquestion =
                array_pop($this->catrandoms[$question->category][$question->questiontext])) {
            if (!ereg("(^|,)$wrappedquestion->id(,|$)", $cmoptions->questionsinuse)) {
                /// $randomquestion is not in use and will therefore be used
                /// as the randomquestion here...
                $wrappedquestion = get_record('question', 'id', $wrappedquestion->id);
                $QTYPES[$wrappedquestion->qtype]
                 ->get_question_options($wrappedquestion);
                $QTYPES[$wrappedquestion->qtype]
                 ->create_session_and_responses($wrappedquestion,
                 $state, $cmoptions, $attempt);
                $wrappedquestion->name_prefix = $question->name_prefix;
                $wrappedquestion->maxgrade    = $question->maxgrade;
                $cmoptions->questionsinuse .= ",$wrappedquestion->id";
                $state->options->question = &$wrappedquestion;
                return true;
            }
        }
        $question->questiontext = '<span class="notifyproblem">'.
         get_string('toomanyrandom', 'quiz'). '</span>';
        $question->qtype = 'description';
        $state->responses = array('' => '');
        return true;
    }

    function restore_session_and_responses(&$question, &$state) {
        /// The raw response records for random questions come in two flavours: