/lib/questionlib.php

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<?php

// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * Code for handling and processing questions
 *
 * This is code that is module independent, i.e., can be used by any module that
 * uses questions, like quiz, lesson, ..
 * This script also loads the questiontype classes
 * Code for handling the editing of questions is in {@link question/editlib.php}
 *
 * TODO: separate those functions which form part of the API
 *       from the helper functions.
 *
 * Major Contributors
 *     - Alex Smith, Julian Sedding and Gustav Delius {@link http://maths.york.ac.uk/serving_maths}
 *
 * @package    core
 * @subpackage question
 * @copyright  1999 onwards Martin Dougiamas  {@link http://moodle.com}
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();

/// CONSTANTS ///////////////////////////////////

/**#@+
 * The different types of events that can create question states
 */
define('QUESTION_EVENTOPEN', '0');      // The state was created by Moodle
define('QUESTION_EVENTNAVIGATE', '1');  // The responses were saved because the student navigated to another page (this is not currently used)
define('QUESTION_EVENTSAVE', '2');      // The student has requested that the responses should be saved but not submitted or validated
define('QUESTION_EVENTGRADE', '3');     // Moodle has graded the responses. A SUBMIT event can be changed to a GRADE event by Moodle.
define('QUESTION_EVENTDUPLICATE', '4'); // The responses submitted were the same as previously
define('QUESTION_EVENTVALIDATE', '5');  // The student has requested a validation. This causes the responses to be saved as well, but not graded.
define('QUESTION_EVENTCLOSEANDGRADE', '6'); // Moodle has graded the responses. A CLOSE event can be changed to a CLOSEANDGRADE event by Moodle.
define('QUESTION_EVENTSUBMIT', '7');    // The student response has been submitted but it has not yet been marked
define('QUESTION_EVENTCLOSE', '8');     // The response has been submitted and the session has been closed, either because the student requested it or because Moodle did it (e.g. because of a timelimit). The responses have not been graded.
define('QUESTION_EVENTMANUALGRADE', '9');   // Grade was entered by teacher

define('QUESTION_EVENTS_GRADED', QUESTION_EVENTGRADE.','.
                    QUESTION_EVENTCLOSEANDGRADE.','.
                    QUESTION_EVENTMANUALGRADE);


define('QUESTION_EVENTS_CLOSED', QUESTION_EVENTCLOSE.','.
                    QUESTION_EVENTCLOSEANDGRADE.','.
                    QUESTION_EVENTMANUALGRADE);

define('QUESTION_EVENTS_CLOSED_OR_GRADED', QUESTION_EVENTGRADE.','.
                    QUESTION_EVENTS_CLOSED);

/**#@-*/

/**#@+
 * The core question types.
 */
define("SHORTANSWER",   "shortanswer");
define("TRUEFALSE",     "truefalse");
define("MULTICHOICE",   "multichoice");
define("RANDOM",        "random");
define("MATCH",         "match");
define("RANDOMSAMATCH", "randomsamatch");
define("DESCRIPTION",   "description");
define("NUMERICAL",     "numerical");
define("MULTIANSWER",   "multianswer");
define("CALCULATED",    "calculated");
define("ESSAY",         "essay");
/**#@-*/

/**
 * Constant determines the number of answer boxes supplied in the editing
 * form for multiple choice and similar question types.
 */
define("QUESTION_NUMANS", "10");

/**
 * Constant determines the number of answer boxes supplied in the editing
 * form for multiple choice and similar question types to start with, with
 * the option of adding QUESTION_NUMANS_ADD more answers.
 */
define("QUESTION_NUMANS_START", 3);

/**
 * Constant determines the number of answer boxes to add in the editing
 * form for multiple choice and similar question types when the user presses
 * 'add form fields button'.
 */
define("QUESTION_NUMANS_ADD", 3);

/**
 * The options used when popping up a question preview window in Javascript.
 */
define('QUESTION_PREVIEW_POPUP_OPTIONS', 'scrollbars=yes&resizable=yes&width=700&height=540');

/**#@+
 * Option flags for ->optionflags
 * The options are read out via bitwise operation using these constants
 */
/**
 * Whether the questions is to be run in adaptive mode. If this is not set then
 * a question closes immediately after the first submission of responses. This
 * is how question is Moodle always worked before version 1.5
 */
define('QUESTION_ADAPTIVE', 1);
/**#@-*/

/**#@+
 * Options for whether flags are shown/editable when rendering questions.
 */
define('QUESTION_FLAGSHIDDEN', 0);
define('QUESTION_FLAGSSHOWN', 1);
define('QUESTION_FLAGSEDITABLE', 2);
/**#@-*/

/**
 * GLOBAL VARAIBLES
 * @global array $QTYPES
 * @name $QTYPES
 */
global $QTYPES;
/**
 * Array holding question type objects. Initialised via calls to
 * question_register_questiontype as the question type classes are included.
 */
$QTYPES = array();

/**
 * Add a new question type to the various global arrays above.
 *
 * @global object
 * @param object $qtype An instance of the new question type class.
 */
function question_register_questiontype($qtype) {
    global $QTYPES;

    $name = $qtype->name();
    $QTYPES[$name] = $qtype;
}

require_once("$CFG->dirroot/question/type/questiontype.php");

// Load the questiontype.php file for each question type
// These files in turn call question_register_questiontype()
// with a new instance of each qtype class.
$qtypenames = get_plugin_list('qtype');
foreach($qtypenames as $qtypename => $qdir) {
    // Instanciates all plug-in question types
    $qtypefilepath= "$qdir/questiontype.php";

    // echo "Loading $qtypename<br/>"; // Uncomment for debugging
    if (is_readable($qtypefilepath)) {
        require_once($qtypefilepath);
    }
}

/**
 * An array of question type names translated to the user's language, suitable for use when
 * creating a drop-down menu of options.
 *
 * Long-time Moodle programmers will realise that this replaces the old $QTYPE_MENU array.
 * The array returned will only hold the names of all the question types that the user should
 * be able to create directly. Some internal question types like random questions are excluded.
 *
 * @global object
 * @return array an array of question type names translated to the user's language.
 */
function question_type_menu() {
    global $QTYPES;
    static $menuoptions = null;
    if (is_null($menuoptions)) {
        $config = get_config('question');
        $menuoptions = array();
        foreach ($QTYPES as $name => $qtype) {
            // Get the name if this qtype is enabled.
            $menuname = $qtype->menu_name();
            $enabledvar = $name . '_disabled';
            if ($menuname && !isset($config->$enabledvar)) {
                $menuoptions[$name] = $menuname;
            }
        }

        $menuoptions = question_sort_qtype_array($menuoptions, $config);
    }
    return $menuoptions;
}

/**
 * Sort an array of question type names according to the question type sort order stored in
 * config_plugins. Entries for which there is no xxx_sortorder defined will go
 * at the end, sorted according to textlib_get_instance()->asort($inarray).
 * @param $inarray an array $qtype => $QTYPES[$qtype]->local_name().
 * @param $config get_config('question'), if you happen to have it around, to save one DB query.
 * @return array the sorted version of $inarray.
 */
function question_sort_qtype_array($inarray, $config = null) {
    if (is_null($config)) {
        $config = get_config('question');
    }

    $sortorder = array();
    foreach ($inarray as $name => $notused) {
        $sortvar = $name . '_sortorder';
        if (isset($config->$sortvar)) {
            $sortorder[$config->$sortvar] = $name;
        }
    }

    ksort($sortorder);
    $outarray = array();
    foreach ($sortorder as $name) {
        $outarray[$name] = $inarray[$name];
        unset($inarray[$name]);
    }
    textlib_get_instance()->asort($inarray);
    return array_merge($outarray, $inarray);
}

/**
 * Move one question type in a list of question types. If you try to move one element
 * off of the end, nothing will change.
 *
 * @param array $sortedqtypes An array $qtype => anything.
 * @param string $tomove one of the keys from $sortedqtypes
 * @param integer $direction +1 or -1
 * @return array an array $index => $qtype, with $index from 0 to n in order, and
 *      the $qtypes in the same order as $sortedqtypes, except that $tomove will
 *      have been moved one place.
 */
function question_reorder_qtypes($sortedqtypes, $tomove, $direction) {
    $neworder = array_keys($sortedqtypes);
    // Find the element to move.
    $key = array_search($tomove, $neworder);
    if ($key === false) {
        return $neworder;
    }
    // Work out the other index.
    $otherkey = $key + $direction;
    if (!isset($neworder[$otherkey])) {
        return $neworder;
    }
    // Do the swap.
    $swap = $neworder[$otherkey];
    $neworder[$otherkey] = $neworder[$key];
    $neworder[$key] = $swap;
    return $neworder;
}

/**
 * Save a new question type order to the config_plugins table.
 * @global object
 * @param $neworder An arra $index => $qtype. Indices should start at 0 and be in order.
 * @param $config get_config('question'), if you happen to have it around, to save one DB query.
 */
function question_save_qtype_order($neworder, $config = null) {
    global $DB;

    if (is_null($config)) {
        $config = get_config('question');
    }

    foreach ($neworder as $index => $qtype) {
        $sortvar = $qtype . '_sortorder';
        if (!isset($config->$sortvar) || $config->$sortvar != $index + 1) {
            set_config($sortvar, $index + 1, 'question');
        }
    }
}

/// OTHER CLASSES /////////////////////////////////////////////////////////

/**
 * This holds the options that are set by the course module
 *
 * @package moodlecore
 * @subpackage question
 * @copyright 1999 onwards Martin Dougiamas  {@link http://moodle.com}
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class cmoptions {
    /**
    * Whether a new attempt should be based on the previous one. If true
    * then a new attempt will start in a state where all responses are set
    * to the last responses from the previous attempt.
    */
    var $attemptonlast = false;

    /**
    * Various option flags. The flags are accessed via bitwise operations
    * using the constants defined in the CONSTANTS section above.
    */
    var $optionflags = QUESTION_ADAPTIVE;

    /**
    * Determines whether in the calculation of the score for a question
    * penalties for earlier wrong responses within the same attempt will
    * be subtracted.
    */
    var $penaltyscheme = true;

    /**
    * The maximum time the user is allowed to answer the questions withing
    * an attempt. This is measured in minutes so needs to be multiplied by
    * 60 before compared to timestamps. If set to 0 no timelimit will be applied
    */
    var $timelimit = 0;

    /**
    * Timestamp for the closing time. Responses submitted after this time will
    * be saved but no credit will be given for them.
    */
    var $timeclose = 9999999999;

    /**
    * The id of the course from withing which the question is currently being used
    */
    var $course = SITEID;

    /**
    * Whether the answers in a multiple choice question should be randomly
    * shuffled when a new attempt is started.
    */
    var $shuffleanswers = true;

    /**
    * The number of decimals to be shown when scores are printed
    */
    var $decimalpoints = 2;
}


/// FUNCTIONS //////////////////////////////////////////////////////

/**
 * Returns an array of names of activity modules that use this question
 *
 * @global object
 * @global object
 * @param object $questionid
 * @return array of strings
 */
function question_list_instances($questionid) {
    global $CFG, $DB;
    $instances = array();
    $modules = $DB->get_records('modules');
    foreach ($modules as $module) {
        $fullmod = $CFG->dirroot . '/mod/' . $module->name;
        if (file_exists($fullmod . '/lib.php')) {
            include_once($fullmod . '/lib.php');
            $fn = $module->name.'_question_list_instances';
            if (function_exists($fn)) {
                $instances = $instances + $fn($questionid);
            }
        }
    }
    return $instances;
}

/**
 * Determine whether there arey any questions belonging to this context, that is whether any of its
 * question categories contain any questions. This will return true even if all the questions are
 * hidden.
 *
 * @global object
 * @param mixed $context either a context object, or a context id.
 * @return boolean whether any of the question categories beloning to this context have
 *         any questions in them.
 */
function question_context_has_any_questions($context) {
    global $DB;
    if (is_object($context)) {
        $contextid = $context->id;
    } else if (is_numeric($context)) {
        $contextid = $context;
    } else {
        print_error('invalidcontextinhasanyquestions', 'question');
    }
    return $DB->record_exists_sql("SELECT *
                                     FROM {question} q
                                     JOIN {question_categories} qc ON qc.id = q.category
                                    WHERE qc.contextid = ? AND q.parent = 0", array($contextid));
}

/**
 * Returns list of 'allowed' grades for grade selection
 * formatted suitably for dropdown box function
 * @return object ->gradeoptionsfull full array ->gradeoptions +ve only
 */
function get_grade_options() {
    // define basic array of grades. This list comprises all fractions of the form:
    // a. p/q for q <= 6, 0 <= p <= q
    // b. p/10 for 0 <= p <= 10
    // c. 1/q for 1 <= q <= 10
    // d. 1/20
    $grades = array(
        1.0000000,
        0.9000000,
        0.8333333,
        0.8000000,
        0.7500000,
        0.7000000,
        0.6666667,
        0.6000000,
        0.5000000,
        0.4000000,
        0.3333333,
        0.3000000,
        0.2500000,
        0.2000000,
        0.1666667,
        0.1428571,
        0.1250000,
        0.1111111,
        0.1000000,
        0.0500000,
        0.0000000);

    // iterate through grades generating full range of options
    $gradeoptionsfull = array();
    $gradeoptions = array();
    foreach ($grades as $grade) {
        $percentage = 100 * $grade;
        $neggrade = -$grade;
        $gradeoptions["$grade"] = "$percentage %";
        $gradeoptionsfull["$grade"] = "$percentage %";
        $gradeoptionsfull["$neggrade"] = -$percentage." %";
    }
    $gradeoptionsfull["0"] = $gradeoptions["0"] = get_string("none");

    // sort lists
    arsort($gradeoptions, SORT_NUMERIC);
    arsort($gradeoptionsfull, SORT_NUMERIC);

    // construct return object
    $grades = new stdClass;
    $grades->gradeoptions = $gradeoptions;
    $grades->gradeoptionsfull = $gradeoptionsfull;

    return $grades;
}

/**
 * match grade options
 * if no match return error or match nearest
 * @param array $gradeoptionsfull list of valid options
 * @param int $grade grade to be tested
 * @param string $matchgrades 'error' or 'nearest'
 * @return mixed either 'fixed' value or false if erro
 */
function match_grade_options($gradeoptionsfull, $grade, $matchgrades='error') {
    // if we just need an error...
    if ($matchgrades=='error') {
        foreach($gradeoptionsfull as $value => $option) {
            // slightly fuzzy test, never check floats for equality :-)
            if (abs($grade-$value)<0.00001) {
                return $grade;
            }
        }
        // didn't find a match so that's an error
        return false;
    }
    // work out nearest value
    else if ($matchgrades=='nearest') {
        $hownear = array();
        foreach($gradeoptionsfull as $value => $option) {
            if ($grade==$value) {
                return $grade;
            }
            $hownear[ $value ] = abs( $grade - $value );
        }
        // reverse sort list of deltas and grab the last (smallest)
        asort( $hownear, SORT_NUMERIC );
        reset( $hownear );
        return key( $hownear );
    }
    else {
        return false;
    }
}

/**
 * Tests whether a category is in use by any activity module
 *
 * @global object
 * @return boolean
 * @param integer $categoryid
 * @param boolean $recursive Whether to examine category children recursively
 */
function question_category_isused($categoryid, $recursive = false) {
    global $DB;

    //Look at each question in the category
    if ($questions = $DB->get_records('question', array('category'=>$categoryid), '', 'id,qtype')) {
        foreach ($questions as $question) {
            if (count(question_list_instances($question->id))) {
                return true;
            }
        }
    }

    //Look under child categories recursively
    if ($recursive) {
        if ($children = $DB->get_records('question_categories', array('parent'=>$categoryid))) {
            foreach ($children as $child) {
                if (question_category_isused($child->id, $recursive)) {
                    return true;
                }
            }
        }
    }

    return false;
}

/**
 * Deletes all data associated to an attempt from the database
 *
 * @global object
 * @global object
 * @param integer $attemptid The id of the attempt being deleted
 */
function delete_attempt($attemptid) {
    global $QTYPES, $DB;

    $states = $DB->get_records('question_states', array('attempt'=>$attemptid));
    if ($states) {
        $stateslist = implode(',', array_keys($states));

        // delete question-type specific data
        foreach ($QTYPES as $qtype) {
            $qtype->delete_states($stateslist);
        }
    }

    // delete entries from all other question tables
    // It is important that this is done only after calling the questiontype functions
    $DB->delete_records("question_states", array("attempt"=>$attemptid));
    $DB->delete_records("question_sessions", array("attemptid"=>$attemptid));
    $DB->delete_records("question_attempts", array("id"=>$attemptid));
}

/**
 * Deletes question and all associated data from the database
 *
 * It will not delete a question if it is used by an activity module
 *
 * @global object
 * @global object
 * @param object $question  The question being deleted
 */
function delete_question($questionid) {
    global $QTYPES, $DB;

    $question = $DB->get_record_sql('
            SELECT q.*, qc.contextid
            FROM {question} q
            JOIN {question_categories} qc ON qc.id = q.category
            WHERE q.id = ?', array($questionid));
    if (!$question) {
        // In some situations, for example if this was a child of a
        // Cloze question that was previously deleted, the question may already
        // have gone. In this case, just do nothing.
        return;
    }

    // Do not delete a question if it is used by an activity module
    if (count(question_list_instances($questionid))) {
        return;
    }

    // delete questiontype-specific data
    question_require_capability_on($question, 'edit');
    if (isset($QTYPES[$question->qtype])) {
        $QTYPES[$question->qtype]->delete_question($questionid, $question->contextid);
    }

    if ($states = $DB->get_records('question_states', array('question'=>$questionid))) {
        $stateslist = implode(',', array_keys($states));

        // delete questiontype-specific data
        foreach ($QTYPES as $qtype) {
            $qtype->delete_states($stateslist);
        }
    }

    // Delete entries from all other question tables
    // It is important that this is done only after calling the questiontype functions
    $DB->delete_records('question_answers', array('question' => $questionid));
    $DB->delete_records('question_states', array('question' => $questionid));
    $DB->delete_records('question_sessions', array('questionid' => $questionid));

    // Now recursively delete all child questions
    if ($children = $DB->get_records('question', array('parent' => $questionid), '', 'id,qtype')) {
        foreach ($children as $child) {
            if ($child->id != $questionid) {
                delete_question($child->id);
            }
        }
    }

    // Finally delete the question record itself
    $DB->delete_records('question', array('id'=>$questionid));
}

/**
 * All question categories and their questions are deleted for this course.
 *
 * @global object
 * @param object $mod an object representing the activity
 * @param boolean $feedback to specify if the process must output a summary of its work
 * @return boolean
 */
function question_delete_course($course, $feedback=true) {
    global $DB, $OUTPUT;

    //To store feedback to be showed at the end of the process
    $feedbackdata   = array();

    //Cache some strings
    $strcatdeleted = get_string('unusedcategorydeleted', 'quiz');
    $coursecontext = get_context_instance(CONTEXT_COURSE, $course->id);
    $categoriescourse = $DB->get_records('question_categories', array('contextid'=>$coursecontext->id), 'parent', 'id, parent, name, contextid');

    if ($categoriescourse) {

        //Sort categories following their tree (parent-child) relationships
        //this will make the feedback more readable
        $categoriescourse = sort_categories_by_tree($categoriescourse);

        foreach ($categoriescourse as $category) {

            //Delete it completely (questions and category itself)
            //deleting questions
            if ($questions = $DB->get_records('question', array('category' => $category->id), '', 'id,qtype')) {
                foreach ($questions as $question) {
                    delete_question($question->id);
                }
                $DB->delete_records("question", array("category"=>$category->id));
            }
            //delete the category
            $DB->delete_records('question_categories', array('id'=>$category->id));

            //Fill feedback
            $feedbackdata[] = array($category->name, $strcatdeleted);
        }
        //Inform about changes performed if feedback is enabled
        if ($feedback) {
            $table = new html_table();
            $table->head = array(get_string('category','quiz'), get_string('action'));
            $table->data = $feedbackdata;
            echo html_writer::table($table);
        }
    }
    return true;
}

/**
 * Category is about to be deleted,
 * 1/ All question categories and their questions are deleted for this course category.
 * 2/ All questions are moved to new category
 *
 * @global object
 * @param object $category course category object
 * @param object $newcategory empty means everything deleted, otherwise id of category where content moved
 * @param boolean $feedback to specify if the process must output a summary of its work
 * @return boolean
 */
function question_delete_course_category($category, $newcategory, $feedback=true) {
    global $DB, $OUTPUT;

    $context = get_context_instance(CONTEXT_COURSECAT, $category->id);
    if (empty($newcategory)) {
        $feedbackdata   = array(); // To store feedback to be showed at the end of the process
        $rescueqcategory = null; // See the code around the call to question_save_from_deletion.
        $strcatdeleted = get_string('unusedcategorydeleted', 'quiz');

        // Loop over question categories.
        if ($categories = $DB->get_records('question_categories', array('contextid'=>$context->id), 'parent', 'id, parent, name')) {
            foreach ($categories as $category) {

                // Deal with any questions in the category.
                if ($questions = $DB->get_records('question', array('category' => $category->id), '', 'id,qtype')) {

                    // Try to delete each question.
                    foreach ($questions as $question) {
                        delete_question($question->id);
                    }

                    // Check to see if there were any questions that were kept because they are
                    // still in use somehow, even though quizzes in courses in this category will
                    // already have been deteted. This could happen, for example, if questions are
                    // added to a course, and then that course is moved to another category (MDL-14802).
                    $questionids = $DB->get_records_menu('question', array('category'=>$category->id), '', 'id,1');
                    if (!empty($questionids)) {
                        if (!$rescueqcategory = question_save_from_deletion(array_keys($questionids),
                                get_parent_contextid($context), print_context_name($context), $rescueqcategory)) {
                            return false;
                       }
                       $feedbackdata[] = array($category->name, get_string('questionsmovedto', 'question', $rescueqcategory->name));
                    }
                }

                // Now delete the category.
                if (!$DB->delete_records('question_categories', array('id'=>$category->id))) {
                    return false;
                }
                $feedbackdata[] = array($category->name, $strcatdeleted);

            } // End loop over categories.
        }

        // Output feedback if requested.
        if ($feedback and $feedbackdata) {
            $table = new html_table();
            $table->head = array(get_string('questioncategory','question'), get_string('action'));
            $table->data = $feedbackdata;
            echo html_writer::table($table);
        }

    } else {
        // Move question categories ot the new context.
        if (!$newcontext = get_context_instance(CONTEXT_COURSECAT, $newcategory->id)) {
            return false;
        }
        $DB->set_field('question_categories', 'contextid', $newcontext->id, array('contextid'=>$context->id));
        if ($feedback) {
            $a = new stdClass;
            $a->oldplace = print_context_name($context);
            $a->newplace = print_context_name($newcontext);
            echo $OUTPUT->notification(get_string('movedquestionsandcategories', 'question', $a), 'notifysuccess');
        }
    }

    return true;
}

/**
 * Enter description here...
 *
 * @global object
 * @param string $questionids list of questionids
 * @param object $newcontext the context to create the saved category in.
 * @param string $oldplace a textual description of the think being deleted, e.g. from get_context_name
 * @param object $newcategory
 * @return mixed false on
 */
function question_save_from_deletion($questionids, $newcontextid, $oldplace, $newcategory = null) {
    global $DB;

    // Make a category in the parent context to move the questions to.
    if (is_null($newcategory)) {
        $newcategory = new stdClass();
        $newcategory->parent = 0;
        $newcategory->contextid = $newcontextid;
        $newcategory->name = get_string('questionsrescuedfrom', 'question', $oldplace);
        $newcategory->info = get_string('questionsrescuedfrominfo', 'question', $oldplace);
        $newcategory->sortorder = 999;
        $newcategory->stamp = make_unique_id_code();
        $newcategory->id = $DB->insert_record('question_categories', $newcategory);
    }

    // Move any remaining questions to the 'saved' category.
    if (!question_move_questions_to_category($questionids, $newcategory->id)) {
        return false;
    }
    return $newcategory;
}

/**
 * All question categories and their questions are deleted for this activity.
 *
 * @global object
 * @param object $cm the course module object representing the activity
 * @param boolean $feedback to specify if the process must output a summary of its work
 * @return boolean
 */
function question_delete_activity($cm, $feedback=true) {
    global $DB, $OUTPUT;

    //To store feedback to be showed at the end of the process
    $feedbackdata   = array();

    //Cache some strings
    $strcatdeleted = get_string('unusedcategorydeleted', 'quiz');
    $modcontext = get_context_instance(CONTEXT_MODULE, $cm->id);
    if ($categoriesmods = $DB->get_records('question_categories', array('contextid'=>$modcontext->id), 'parent', 'id, parent, name, contextid')){
        //Sort categories following their tree (parent-child) relationships
        //this will make the feedback more readable
        $categoriesmods = sort_categories_by_tree($categoriesmods);

        foreach ($categoriesmods as $category) {

            //Delete it completely (questions and category itself)
            //deleting questions
            if ($questions = $DB->get_records('question', array('category' => $category->id), '', 'id,qtype')) {
                foreach ($questions as $question) {
                    delete_question($question->id);
                }
                $DB->delete_records("question", array("category"=>$category->id));
            }
            //delete the category
            $DB->delete_records('question_categories', array('id'=>$category->id));

            //Fill feedback
            $feedbackdata[] = array($category->name, $strcatdeleted);
        }
        //Inform about changes performed if feedback is enabled
        if ($feedback) {
            $table = new html_table();
            $table->head = array(get_string('category','quiz'), get_string('action'));
            $table->data = $feedbackdata;
            echo html_writer::table($table);
        }
    }
    return true;
}

/**
 * This function should be considered private to the question bank, it is called from
 * question/editlib.php question/contextmoveq.php and a few similar places to to the work of
 * acutally moving questions and associated data. However, callers of this function also have to
 * do other work, which is why you should not call this method directly from outside the questionbank.
 *
 * @global object
 * @param string $questionids a comma-separated list of question ids.
 * @param integer $newcategoryid the id of the category to move to.
 */
function question_move_questions_to_category($questionids, $newcategoryid) {
    global $DB, $QTYPES;

    $newcontextid = $DB->get_field('question_categories', 'contextid',
            array('id' => $newcategoryid));
    list($questionidcondition, $params) = $DB->get_in_or_equal($questionids);
    $questions = $DB->get_records_sql("
            SELECT q.id, q.qtype, qc.contextid
              FROM {question} q
              JOIN {question_categories} qc ON q.category = qc.id
             WHERE  q.id $questionidcondition", $params);
    foreach ($questions as $question) {
        if ($newcontextid != $question->contextid) {
            $QTYPES[$question->qtype]->move_files($question->id,
                    $question->contextid, $newcontextid);
        }
    }

    // Move the questions themselves.
    $DB->set_field_select('question', 'category', $newcategoryid, "id $questionidcondition", $params);

    // Move any subquestions belonging to them.
    $DB->set_field_select('question', 'category', $newcategoryid, "parent $questionidcondition", $params);

    // TODO Deal with datasets.

    return true;
}

/**
 * This function helps move a question cateogry to a new context by moving all
 * the files belonging to all the questions to the new context.
 * Also moves subcategories.
 * @param integer $categoryid the id of the category being moved.
 * @param integer $oldcontextid the old context id.
 * @param integer $newcontextid the new context id.
 */
function question_move_category_to_context($categoryid, $oldcontextid, $newcontextid) {
    global $DB, $QTYPES;

    $questionids = $DB->get_records_menu('question',
            array('category' => $categoryid), '', 'id,qtype');
    foreach ($questionids as $questionid => $qtype) {
        $QTYPES[$qtype]->move_files($questionid, $oldcontextid, $newcontextid);
    }

    $subcatids = $DB->get_records_menu('question_categories',
            array('parent' => $categoryid), '', 'id,1');
    foreach ($subcatids as $subcatid => $notused) {
        $DB->set_field('question_categories', 'contextid', $newcontextid, array('id' => $subcatid));
        question_move_category_to_context($subcatid, $oldcontextid, $newcontextid);
    }
}

/**
 * Given a list of ids, load the basic information about a set of questions from the questions table.
 * The $join and $extrafields arguments can be used together to pull in extra data.
 * See, for example, the usage in mod/quiz/attemptlib.php, and
 * read the code below to see how the SQL is assembled. Throws exceptions on error.
 *
 * @global object
 * @global object
 * @param array $questionids array of question ids.
 * @param string $extrafields extra SQL code to be added to the query.
 * @param string $join extra SQL code to be added to the query.
 * @param array $extraparams values for any placeholders in $join.
 * You are strongly recommended to use named placeholder.
 *
 * @return array partially complete question objects. You need to call get_question_options
 * on them before they can be properly used.
 */
function question_preload_questions($questionids, $extrafields = '', $join = '', $extraparams = array()) {
    global $CFG, $DB;
    if (empty($questionids)) {
        return array();
    }
    if ($join) {
        $join = ' JOIN '.$join;
    }
    if ($extrafields) {
        $extrafields = ', ' . $extrafields;
    }
    list($questionidcondition, $params) = $DB->get_in_or_equal(
            $questionids, SQL_PARAMS_NAMED, 'qid0000');
    $sql = 'SELECT q.*' . $extrafields . ' FROM {question} q' . $join .
            ' WHERE q.id ' . $questionidcondition;

    // Load the questions
    if (!$questions = $DB->get_records_sql($sql, $extraparams + $params)) {
        return 'Could not load questions.';
    }

    foreach ($questions as $question) {
        $question->_partiallyloaded = true;
    }

    // Note, a possible optimisation here would be to not load the TEXT fields
    // (that is, questiontext and generalfeedback) here, and instead load them in
    // question_load_questions. That would add one DB query, but reduce the amount
    // of data transferred most of the time. I am not going to do this optimisation
    // until it is shown to be worthwhile.

    return $questions;
}

/**
 * Load a set of questions, given a list of ids. The $join and $extrafields arguments can be used
 * together to pull in extra data. See, for example, the usage in mod/quiz/attempt.php, and
 * read the code below to see how the SQL is assembled. Throws exceptions on error.
 *
 * @param array $questionids array of question ids.
 * @param string $extrafields extra SQL code to be added to the query.
 * @param string $join extra SQL code to be added to the query.
 * @param array $extraparams values for any placeholders in $join.
 * You are strongly recommended to use named placeholder.
 *
 * @return array question objects.
 */
function question_load_questions($questionids, $extrafields = '', $join = '') {
    $questions = question_preload_questions($questionids, $extrafields, $join);

    // Load the question type specific information
    if (!get_question_options($questions)) {
        return 'Could not load the question options';
    }

    return $questions;
}

/**
 * Private function to factor common code out of get_question_options().
 *
 * @global object
 * @global object
 * @param object $question the question to tidy.
 * @param boolean $loadtags load the question tags from the tags table. Optional, default false.
 * @return boolean true if successful, else false.
 */
function _tidy_question(&$question, $loadtags = false) {
    global $CFG, $QTYPES;
    if (!array_key_exists($question->qtype, $QTYPES)) {
        $question->qtype = 'missingtype';
        $question->questiontext = '<p>' . get_string('warningmissingtype', 'quiz') . '</p>' . $question->questiontext;
    }
    $question->name_prefix = question_make_name_prefix($question->id);
    if ($success = $QTYPES[$question->qtype]->get_question_options($question)) {
        if (isset($question->_partiallyloaded)) {
            unset($question->_partiallyloaded);
        }
    }
    if ($loadtags && !empty($CFG->usetags)) {
        require_once($CFG->dirroot . '/tag/lib.php');
        $question->tags = tag_get_tags_array('question', $question->id);
    }
    return $success;
}

/**
 * Updates the question objects with question type specific
 * information by calling {@link get_question_options()}
 *
 * Can be called either with an array of question objects or with a single
 * question object.
 *
 * @param mixed $questions Either an array of question objects to be updated
 *         or just a single question object
 * @param boolean $loadtags load the question tags from the tags table. Optional, default false.
 * @return bool Indicates success or failure.
 */
function get_question_options(&$questions, $loadtags = false) {
    if (is_array($questions)) { // deal with an array of questions
        foreach ($questions as $i => $notused) {
            if (!_tidy_question($questions[$i], $loadtags)) {
                return false;
            }
        }
        return true;
    } else { // deal with single question
        return _tidy_question($questions, $loadtags);
    }
}

/**
 * Load the basic state information for
 *
 * @global object
 * @param integer $attemptid the attempt id to load the states for.
 * @return array an array of state data from the database, you will subsequently
 *      need to call question_load_states to get fully loaded states that can be
 *      used by the question types. The states here should be sufficient for
 *      basic tasks like rendering navigation.
 */
function question_preload_states($attemptid) {
    global $DB;
    // Note, changes here probably also need to be reflected in
    // regrade_question_in_attempt and question_load_specific_state.

    // The questionid field must be listed first so that it is used as the
    // array index in the array returned by $DB->get_records_sql
    $statefields = 'n.questionid as question, s.id, s.attempt, ' .
            's.seq_number, s.answer, s.timestamp, s.event, s.grade, s.raw_grade, ' .
            's.penalty, n.sumpenalty, n.manualcomment, n.manualcommentformat, ' .
            'n.flagged, n.id as questionsessionid';

    // Load the newest states for the questions
    $sql = "SELECT $statefields
              FROM {question_states} s, {question_sessions} n
             WHERE s.id = n.newest AND n.attemptid = ?";
    $states = $DB->get_records_sql($sql, array($attemptid));
    if (!$states) {
        return false;
    }

    // Load the newest graded states for the questions
    $sql = "SELECT $statefields
              FROM {question_states} s, {question_sessions} n
             WHERE s.id = n.newgraded AND n.attemptid = ?";
    $gradedstates = $DB->get_records_sql($sql, array($attemptid));

    // Hook the two together.
    foreach ($states as $questionid => $state) {
        $states[$questionid]->_partiallyloaded = true;
        if ($gradedstates[$questionid]) {
            $states[$questionid]->last_graded = $gradedstates[$questionid];
            $states[$questionid]->last_graded->_partiallyloaded = true;
        }
    }

    return $states;
}

/**
 * Finish loading the question states that were extracted from the database with
 * question_preload_states, creating new states for any question where there
 * is not a state in the database.
 *
 * @global object
 * @global object
 * @param array $questions the questions to load state for.
 * @param array $states the partially loaded states this array is updated.
 * @param object $cmoptions options from the module we are loading the states for. E.g. $quiz.
 * @param object $attempt The attempt for which the question sessions are
 *      to be restored or created.
 * @param mixed either the id of a previous attempt, if this attmpt is
 *      building on a previous one, or false for a clean attempt.
 * @return true or false for success or failure.
 */
function question_load_states(&$questions, &$states, $cmoptions, $attempt, $lastattemptid = false) {
    global $QTYPES, $DB;

    // loop through all questions and set the last_graded states
    foreach (array_keys($questions) as $qid) {
        if (isset($states[$qid])) {
            restore_question_state($questions[$qid], $states[$qid]);
            if (isset($states[$qid]->_partiallyloaded)) {
                unset($states[$qid]->_partiallyloaded);
            }
            if (isset($states[$qid]->last_graded)) {
                restore_question_state($questions[$qid], $states[$qid]->last_graded);
                if (isset($states[$qid]->last_graded->_partiallyloaded)) {
                    unset($states[$qid]->last_graded->_partiallyloaded);
                }
            } else {
                $states[$qid]->last_graded = clone($states[$qid]);
            }
        } else {

            if ($lastattemptid) {
                // If the new attempt is to be based on this previous attempt.
                // Find the responses from the previous attempt and save them to the new session

                // Load the last graded state for the question. Note, $statefields is
                // the same as above, except that we don't want n.manualcomment.
                $statefields = 'n.questionid as question, s.id, s.attempt, ' .
                        's.seq_number, s.answer, s.timestamp, s.event, s.grade, s.raw_grade, ' .
                        's.penalty, n.sumpenalty';
                $sql = "SELECT $statefields
                          FROM {question_states} s, {question_sessions} n
                         WHERE s.id = n.newest
                               AND n.attemptid = ?
                               AND n.questionid = ?";
                if (!$laststate = $DB->get_record_sql($sql, array($lastattemptid, $qid))) {
                    // Only restore previous responses that have been graded
                    continue;
                }
                // Restore the state so that the responses will be restored
                restore_question_state($questions[$qid], $laststate);
                $states[$qid] = clone($laststate);
                unset($states[$qid]->id);
            } else {
                // create a new empty state
                $states[$qid] = new stdClass();
                $states[$qid]->question = $qid;
                $states[$qid]->responses = array('' => '');
                $states[$qid]->raw_grade = 0;
            }

            // now fill/overide initial values
            $states[$qid]->attempt = $attempt->uniqueid;
            $states[$qid]->seq_number = 0;
            $states[$qid]->timestamp = $attempt->timestart;
            $states[$qid]->event = ($attempt->timefinish) ? QUESTION_EVENTCLOSE : QUESTION_EVENTOPEN;
            $states[$qid]->grade = 0;
            $states[$qid]->penalty = 0;
            $states[$qid]->sumpenalty = 0;
            $states[$qid]->manualcomment = '';
            $states[$qid]->manualcommentformat = FORMAT_HTML;
            $states[$qid]->flagged = 0;

            // Prevent further changes to the session from incrementing the
            // sequence number
            $states[$qid]->changed = true;

            if ($lastattemptid) {
                // prepare the previous responses for new processing
                $action = new stdClass;
                $action->responses = $laststate->responses;
                $action->timestamp = $laststate->timestamp;
                $action->event = QUESTION_EVENTSAVE; //emulate save of questions from all pages MDL-7631

                // Process these responses ...
                question_process_responses($questions[$qid], $states[$qid], $action, $cmoptions, $attempt);

                // Fix for Bug #5506: When each attempt is built on the last one,
                // preserve the options from any previous attempt.
                if ( isset($laststate->options) ) {
                    $states[$qid]->options = $laststate->options;
                }
            } else {
                // Create the empty question type specific information
                if (!$QTYPES[$questions[$qid]->qtype]->create_session_and_responses(
                        $questions[$qid], $states[$qid], $cmoptions, $attempt)) {
                    return false;
                }
            }
            $states[$qid]->last_graded = clone($states[$qid]);
        }
    }
    return true;
}

/**
* Loads the most recent state of each question session from the database
* or create new one.
*
* For each question the most recent session state for the current attempt
* is loaded from the question_states table and the question type specific data and
* responses are added by calling {@link restore_question_state()} which in turn
* calls {@link restore_session_and_responses()} for each question.
* If no states exist for the question instance an empty state object is
* created representing the start of a session and empty question
* type specific information and responses are created by calling
* {@link create_session_and_responses()}.
*
* @return array           An array of state objects representing the most recent
*                         states of the question sessions.
* @param array $questions The questions for which sessions are to be restored or
*                         created.
* @param object $cmoptions
* @param object $attempt  The attempt for which the question sessions are
*                         to be restored or created.
* @param mixed either the id of a previous attempt, if this attmpt is
*                         building on a previous one, or false for a clean attempt.
*/
function get_question_states(&$questions, $cmoptions, $attempt, $lastattemptid = false) {
    // Preload the states.
    $states = question_preload_states($attempt->uniqueid);
    if (!$states) {
        $states = array();
    }

    // Then finish the job.
    if (!question_load_states($questions, $states, $cmoptions, $attempt, $lastattemptid)) {
        return false;
    }

    return $states;
}

/**
 * Load a particular previous state of a question.
 *
 * @global object
 * @param array $question The question to load the state for.
 * @param object $cmoptions Options from the specifica activity module, e.g. $quiz.
 * @param integer $attemptid The question_attempts this is part of.
 * @param integer $stateid The id of a specific state of this question.
 * @return object the requested state. False on error.
 */
function question_load_specific_state($question, $cmoptions, $attemptid, $stateid) {
    global $DB;

    // Load specified states for the question.
    // sess.sumpenalty is probably wrong here shoul really be a sum of penalties from before the one we are asking for.
    $sql = 'SELECT st.*, sess.sumpenalty, sess.manualcomment, sess.manualcommentformat,
                        sess.flagged, sess.id as questionsessionid
              FROM {question_states} st, {question_sessions} sess
             WHERE st.id = ?
               AND st.attempt = ?
               AND sess.attemptid = st.attempt
               AND st.question = ?
               AND sess.questionid = st.question';
    $state = $DB->get_record_sql($sql, array($stateid, $attemptid, $question->id));
    if (!$state) {
        return false;
    }
    restore_question_state($question, $state);

    // Load the most recent graded states for the questions before the specified one.
    $sql = 'SELECT st.*, sess.sumpenalty, sess.manualcomment, sess.manualcommentformat,
                        sess.flagged, sess.id as questionsessionid
              FROM {question_states} st, {question_sessions} sess
             WHERE st.seq_number <= ?
               AND st.attempt = ?
               AND sess.attemptid = st.attempt
               AND st.question = ?
               AND sess.questionid = st.question
               AND st.event IN ('.QUESTION_EVENTS_GRADED.') '.
           'ORDER BY st.seq_number DESC';
    $gradedstates = $DB->get_records_sql($sql, array($state->seq_number, $attemptid, $question->id), 0, 1);
    if (empty($gradedstates)) {
        $state->last_graded = clone($state);
    } else {
        $gradedstate = reset($gradedstates);
        restore_question_state($question, $gradedstate);
        $state->last_graded = $gradedstate;
    }
    return $state;
}

/**
* Creates the run-time fields for the states
*
* Extends the state objects for a question by calling
* {@link restore_session_and_responses()}
 *
 * @global object
* @param object $question The question for which the state is needed
* @param object $state The state as loaded from the database
* @return boolean Represents success or failure
*/
function restore_question_state(&$question, &$state) {
    global $QTYPES;

    // initialise response to the value in the answer field
    $state->responses = array('' => $state->answer);

    // Set the changed field to false; any code which changes the
    // question session must set this to true and must increment
    // ->seq_number. The save_question_session
    // function will save the new state object to the database if the field is
    // set to true.
    $state->changed = false;

    // Load the question type specific data
    return $QTYPES[$question->qtype]->restore_session_and_responses($question, $state);

}

/**
* Saves the current state of the question…

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