/lib/questionlib.php

<?php  // $Id$
/**
 * 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.
 *
 * @author Martin Dougiamas and many others. This has recently been completely
 *         rewritten by Alex Smith, Julian Sedding and Gustav Delius as part of
 *         the Serving Mathematics project
 *         {@link http://maths.york.ac.uk/serving_maths}
 * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
 * @package question
 */

/// 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);
/**#@-*/

/**#@+
 * 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 used in forms that move files.
 *
 */
define('QUESTION_FILENOTHINGSELECTED', 0);
define('QUESTION_FILEDONOTHING', 1);
define('QUESTION_FILECOPY', 2);
define('QUESTION_FILEMOVE', 3);
define('QUESTION_FILEMOVELINKSONLY', 4);

/**#@-*/

/// QTYPES INITIATION //////////////////
// These variables get initialised via calls to question_register_questiontype
// as the question type classes are included.
global $QTYPES, $QTYPE_MANUAL, $QTYPE_EXCLUDE_FROM_RANDOM;
/**
 * Array holding question type objects
 */
$QTYPES = array();
/**
 * String in the format "'type1','type2'" that can be used in SQL clauses like
 * "WHERE q.type IN ($QTYPE_MANUAL)".
 */
$QTYPE_MANUAL = '';
/**
 * String in the format "'type1','type2'" that can be used in SQL clauses like
 * "WHERE q.type NOT IN ($QTYPE_EXCLUDE_FROM_RANDOM)".
 */
$QTYPE_EXCLUDE_FROM_RANDOM = '';

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

    $name = $qtype->name();
    $QTYPES[$name] = $qtype;
    if ($qtype->is_manual_graded()) {
        if ($QTYPE_MANUAL) {
            $QTYPE_MANUAL .= ',';
        }
        $QTYPE_MANUAL .= "'$name'";
    }
    if (!$qtype->is_usable_by_random()) {
        if ($QTYPE_EXCLUDE_FROM_RANDOM) {
            $QTYPE_EXCLUDE_FROM_RANDOM .= ',';
        }
        $QTYPE_EXCLUDE_FROM_RANDOM .= "'$name'";
    }
}

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.
$qtypenames= get_list_of_plugins('question/type');
foreach($qtypenames as $qtypename) {
    // Instanciates all plug-in question types
    $qtypefilepath= "$CFG->dirroot/question/type/$qtypename/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.
 *
 * @return array an array of question type names translated to the user's language.
 */
function question_type_menu() {
    global $QTYPES;
    static $menu_options = null;
    if (is_null($menu_options)) {
        $menu_options = array();
        foreach ($QTYPES as $name => $qtype) {
            $menuname = $qtype->menu_name();
            if ($menuname) {
                $menu_options[$name] = $menuname;
            }
        }
    }
    return $menu_options;
}

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

/**
 * This holds the options that are set by the course module
 */
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
 *
 * @param object $questionid
 * @return array of strings
 */
function question_list_instances($questionid) {
    global $CFG;
    $instances = array();
    $modules = get_records('modules');
    foreach ($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.
 *
 * @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 $CFG;
    if (is_object($context)) {
        $contextid = $context->id;
    } else if (is_numeric($context)) {
        $contextid = $context;
    } else {
        print_error('invalidcontextinhasanyquestions', 'question');
    }
    return record_exists_sql('SELECT * FROM ' . $CFG->prefix . 'question q ' .
            'JOIN ' . $CFG->prefix . 'question_categories qc ON qc.id = q.category ' .
            "WHERE qc.contextid = $contextid AND q.parent = 0");
}

/**
 * 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
    $grades = array(
        1.00,
        0.90,
        0.83333,
        0.80,
        0.75,
        0.70,
        0.66666,
        0.60,
        0.50,
        0.40,
        0.33333,
        0.30,
        0.25,
        0.20,
        0.16666,
        0.142857,
        0.125,
        0.11111,
        0.10,
        0.05,
        0);

    // 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
 *
 * @return boolean
 * @param integer $categoryid
 * @param boolean $recursive Whether to examine category children recursively
 */
function question_category_isused($categoryid, $recursive = false) {

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

    //Look under child categories recursively
    if ($recursive) {
        if ($children = get_records('question_categories', '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
 *
 * @param integer $attemptid The id of the attempt being deleted
 */
function delete_attempt($attemptid) {
    global $QTYPES;

    $states = get_records('question_states', '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
    delete_records("question_states", "attempt", $attemptid);
    delete_records("question_sessions", "attemptid", $attemptid);
    delete_records("question_attempts", "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
 * @param object $question  The question being deleted
 */
function delete_question($questionid) {
    global $QTYPES;

    if (!$question = get_record('question', 'id', $questionid)) {
        // 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($question, 'edit');
    if ($question) {
        if (isset($QTYPES[$question->qtype])) {
            $QTYPES[$question->qtype]->delete_question($questionid);
        }
    } else {
        echo "Question with id $questionid does not exist.<br />";
    }

    if ($states = get_records('question_states', '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
    delete_records("question_answers", "question", $questionid);
    delete_records("question_states", "question", $questionid);
    delete_records("question_sessions", "questionid", $questionid);

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

    // Finally delete the question record itself
    delete_records('question', 'id', $questionid);

    return;
}

/**
 * All question categories and their questions are deleted for this course.
 *
 * @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) {
    //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 = get_records('question_categories', 'contextid', $coursecontext->id, 'parent', 'id, parent, name');

    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 = get_records("question", "category", $category->id)) {
                foreach ($questions as $question) {
                    delete_question($question->id);
                }
                delete_records("question", "category", $category->id);
            }
            //delete the category
            delete_records('question_categories', 'id', $category->id);

            //Fill feedback
            $feedbackdata[] = array($category->name, $strcatdeleted);
        }
        //Inform about changes performed if feedback is enabled
        if ($feedback) {
            $table = new stdClass;
            $table->head = array(get_string('category','quiz'), get_string('action'));
            $table->data = $feedbackdata;
            print_table($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
 *
 * @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) {
    $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 = get_records('question_categories', 'contextid', $context->id, 'parent', 'id, parent, name')) {
            foreach ($categories as $category) {

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

                    // 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 = get_records_select_menu('question', 'category = ' . $category->id, '', 'id,1');
                    if (!empty($questionids)) {
                        if (!$rescueqcategory = question_save_from_deletion(implode(',', array_keys($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 (!delete_records('question_categories', 'id', $category->id)) {
                    return false;
                }
                $feedbackdata[] = array($category->name, $strcatdeleted);

            } // End loop over categories.
        }

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

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

    return true;
}

/**
 * Enter description here...
 *
 * @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, $newcategory = null) {
    // Make a category in the parent context to move the questions to.
    if (is_null($newcategory)) {
        $newcategory = new object();
        $newcategory->parent = 0;
        $newcategory->contextid = $newcontextid;
        $newcategory->name = addslashes(get_string('questionsrescuedfrom', 'question', $oldplace));
        $newcategory->info = addslashes(get_string('questionsrescuedfrominfo', 'question', $oldplace));
        $newcategory->sortorder = 999;
        $newcategory->stamp = make_unique_id_code();
        if (!$newcategory->id = insert_record('question_categories', $newcategory)) {
            return false;
        }
    }

    // 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.
 *
 * @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) {
    //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 = get_records('question_categories', 'contextid', $modcontext->id, 'parent', 'id, parent, name')){
        //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 = get_records("question", "category", $category->id)) {
                foreach ($questions as $question) {
                    delete_question($question->id);
                }
                delete_records("question", "category", $category->id);
            }
            //delete the category
            delete_records('question_categories', 'id', $category->id);

            //Fill feedback
            $feedbackdata[] = array($category->name, $strcatdeleted);
        }
        //Inform about changes performed if feedback is enabled
        if ($feedback) {
            $table = new stdClass;
            $table->head = array(get_string('category','quiz'), get_string('action'));
            $table->data = $feedbackdata;
            print_table($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.
 *
 * @param string $questionids a comma-separated list of question ids.
 * @param integer $newcategory the id of the category to move to.
 */
function question_move_questions_to_category($questionids, $newcategory) {
    $result = true;

    // Move the questions themselves.
    $result = $result && set_field_select('question', 'category', $newcategory, "id IN ($questionids)");

    // Move any subquestions belonging to them.
    $result = $result && set_field_select('question', 'category', $newcategory, "parent IN ($questionids)");

    // TODO Deal with datasets.

    return $result;
}

/**
 * @param array $row tab objects
 * @param question_edit_contexts $contexts object representing contexts available from this context
 * @param string $querystring to append to urls
 * */
function questionbank_navigation_tabs(&$row, $contexts, $querystring) {
    global $CFG, $QUESTION_EDITTABCAPS;
    $tabs = array(
            'questions' =>array("$CFG->wwwroot/question/edit.php?$querystring", get_string('questions', 'quiz'), get_string('editquestions', 'quiz')),
            'categories' =>array("$CFG->wwwroot/question/category.php?$querystring", get_string('categories', 'quiz'), get_string('editqcats', 'quiz')),
            'import' =>array("$CFG->wwwroot/question/import.php?$querystring", get_string('import', 'quiz'), get_string('importquestions', 'quiz')),
            'export' =>array("$CFG->wwwroot/question/export.php?$querystring", get_string('export', 'quiz'), get_string('exportquestions', 'quiz')));
    foreach ($tabs as $tabname => $tabparams){
        if ($contexts->have_one_edit_tab_cap($tabname)) {
            $row[] = new tabobject($tabname, $tabparams[0], $tabparams[1], $tabparams[2]);
        }
    }
}

/**
 * Private function to factor common code out of get_question_options().
 *
 * @param object $question the question to tidy.
 * @return boolean true if successful, else false.
 */
function _tidy_question(&$question) {
    global $QTYPES;
    if (!array_key_exists($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);
    return $QTYPES[$question->qtype]->get_question_options($question);
}

/**
 * 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 $questions Either an array of question objects to be updated
 *         or just a single question object
 * @return bool Indicates success or failure.
 */
function get_question_options(&$questions) {
    if (is_array($questions)) { // deal with an array of questions
        foreach ($questions as $i => $notused) {
            if (!_tidy_question($questions[$i])) {
                return false;
            }
        }
        return true;
    } else { // deal with single question
        return _tidy_question($questions);
    }
}

/**
* 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) {
    global $CFG, $QTYPES;

    // get the question ids
    $ids = array_keys($questions);
    $questionlist = implode(',', $ids);

    // The question field must be listed first so that it is used as the
    // array index in the array returned by get_records_sql
    $statefields = 'n.questionid as question, s.*, n.sumpenalty, n.manualcomment';
    // Load the newest states for the questions
    $sql = "SELECT $statefields".
           "  FROM {$CFG->prefix}question_states s,".
           "       {$CFG->prefix}question_sessions n".
           " WHERE s.id = n.newest".
           "   AND n.attemptid = '$attempt->uniqueid'".
           "   AND n.questionid IN ($questionlist)";
    $states = get_records_sql($sql);

    // Load the newest graded states for the questions
    $sql = "SELECT $statefields".
           "  FROM {$CFG->prefix}question_states s,".
           "       {$CFG->prefix}question_sessions n".
           " WHERE s.id = n.newgraded".
           "   AND n.attemptid = '$attempt->uniqueid'".
           "   AND n.questionid IN ($questionlist)";
    $gradedstates = get_records_sql($sql);

    // loop through all questions and set the last_graded states
    foreach ($ids as $i) {
        if (isset($states[$i])) {
            restore_question_state($questions[$i], $states[$i]);
            if (isset($gradedstates[$i])) {
                restore_question_state($questions[$i], $gradedstates[$i]);
                $states[$i]->last_graded = $gradedstates[$i];
            } else {
                $states[$i]->last_graded = clone($states[$i]);
            }
        } 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
                $statefields = 'n.questionid as question, s.*, n.sumpenalty';
                $sql = "SELECT $statefields".
                       "  FROM {$CFG->prefix}question_states s,".
                       "       {$CFG->prefix}question_sessions n".
                       " WHERE s.id = n.newgraded".
                       "   AND n.attemptid = '$lastattemptid'".
                       "   AND n.questionid = '$i'";
                if (!$laststate = get_record_sql($sql)) {
                    // Only restore previous responses that have been graded
                    continue;
                }
                // Restore the state so that the responses will be restored
                restore_question_state($questions[$i], $laststate);
                $states[$i] = clone($laststate);
                unset($states[$i]->id);
            } else {
                // create a new empty state
                $states[$i] = new object;
                $states[$i]->question = $i;
                $states[$i]->responses = array('' => '');
                $states[$i]->raw_grade = 0;
            }

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

            // Prevent further changes to the session from incrementing the
            // sequence number
            $states[$i]->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($questions[$i], $states[$i], $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) ) {
                    $states[$i]->options = $laststate->options;
                }
            } else {
                // Create the empty question type specific information
                if (!$QTYPES[$questions[$i]->qtype]->create_session_and_responses(
                        $questions[$i], $states[$i], $cmoptions, $attempt)) {
                    return false;
                }
            }
            $states[$i]->last_graded = clone($states[$i]);
        }
    }
    return $states;
}


/**
* Creates the run-time fields for the states
*
* Extends the state objects for a question by calling
* {@link restore_session_and_responses()}
* @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
    $state->responses = array('' => addslashes($state->answer));
    unset($state->answer);
    $state->manualcomment = isset($state->manualcomment) ? addslashes($state->manualcomment) : '';

    // 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 session to the database
*
* The state object representing the current state of the session for the
* question is saved to the question_states table with ->responses[''] saved
* to the answer field of the database table. The information in the
* question_sessions table is updated.
* The question type specific data is then saved.
* @return mixed           The id of the saved or updated state or false
* @param object $question The question for which session is to be saved.
* @param object $state    The state information to be saved. In particular the
*                         most recent responses are in ->responses. The object
*                         is updated to hold the new ->id.
*/
function save_question_session(&$question, &$state) {
    global $QTYPES;
    // Check if the state has changed
    if (!$state->changed && isset($state->id)) {
        return $state->id;
    }
    // Set the legacy answer field
    $state->answer = isset($state->responses['']) ? $state->responses[''] : '';

    // Save the state
    if (!empty($state->update)) { // this forces the old state record to be overwritten
        update_record('question_states', $state);
    } else {
        if (!$state->id = insert_record('question_states', $state)) {
            unset($state->id);
            unset($state->answer);
            return false;
        }
    }

    // create or update the session
    if (!$session = get_record('question_sessions', 'attemptid',
            $state->attempt, 'questionid', $question->id)) {
        $session->attemptid = $state->attempt;
        $session->questionid = $question->id;
        $session->newest = $state->id;
        // The following may seem weird, but the newgraded field needs to be set
        // already even if there is no graded state yet.
        $session->newgraded = $state->id;
        $session->sumpenalty = $state->sumpenalty;
        $session->manualcomment = $state->manualcomment;
        if (!insert_record('question_sessions', $session)) {
            error('Could not insert entry in question_sessions');
        }
    } else {
        $session->newest = $state->id;
        if (question_state_is_graded($state) or $state->event == QUESTION_EVENTOPEN) {
            // this state is graded or newly opened, so it goes into the lastgraded field as well
            $session->newgraded = $state->id;
            $session->sumpenalty = $state->sumpenalty;
            $session->manualcomment = $state->manualcomment;
        } else {
            $session->manualcomment = addslashes($session->manualcomment);
        }
        update_record('question_sessions', $session);
    }

    unset($state->answer);

    // Save the question type specific state information and responses
    if (!$QTYPES[$question->qtype]->save_session_and_responses(
     $question, $state)) {
        return false;
    }
    // Reset the changed flag
    $state->changed = false;
    return $state->id;
}

/**
* Determines whether a state has been graded by looking at the event field
*
* @return boolean         true if the state has been graded
* @param object $state
*/
function question_state_is_graded($state) {
    $gradedevents = explode(',', QUESTION_EVENTS_GRADED);
    return (in_array($state->event, $gradedevents));
}

/**
* Determines whether a state has been closed by looking at the event field
*
* @return boolean         true if the state has been closed
* @param object $state
*/
function question_state_is_closed($state) {
    return ($state->event == QUESTION_EVENTCLOSE
        or $state->event == QUESTION_EVENTCLOSEANDGRADE
        or $state->event == QUESTION_EVENTMANUALGRADE);
}


/**
 * Extracts responses from submitted form
 *
 * This can extract the responses given to one or several questions present on a page
 * It returns an array with one entry for each question, indexed by question id
 * Each entry is an object with the properties
 *  ->event     The event that has triggered the submission. This is determined by which button
 *               the user has pressed.
 *  ->responses An array holding the responses to an individual question, indexed by the
 *               name of the corresponding form element.
 *  ->timestamp A unix timestamp
 * @return array            array of action objects, indexed by question ids.
 * @param array $questions  an array containing at least all questions that are used on the form
 * @param array $formdata   the data submitted by the form on the question page
 * @param integer $defaultevent  the event type used if no 'mark' or 'validate' is submitted
 */
function question_extract_responses($questions, $formdata, $defaultevent=QUESTION_EVENTSAVE) {

    $time = time();
    $actions = array();
    foreach ($formdata as $key => $response) {
        // Get the question id from the response name
        if (false !== ($quid = question_get_id_from_name_prefix($key))) {
            // check if this is a valid id
            if (!isset($questions[$quid])) {
                error('Form contained question that is not in questionids');
            }

            // Remove the name prefix from the name
            //decrypt trying
            $key = substr($key, strlen($questions[$quid]->name_prefix));
            if (false === $key) {
                $key = '';
            }
            // Check for question validate and mark buttons & set events
            if ($key === 'validate') {
                $actions[$quid]->event = QUESTION_EVENTVALIDATE;
            } else if ($key === 'submit') {
                $actions[$quid]->event = QUESTION_EVENTSUBMIT;
            } else {
                $actions[$quid]->event = $defaultevent;
            }

            // Update the state with the new response
            $actions[$quid]->responses[$key] = $response;

            // Set the timestamp
            $actions[$quid]->timestamp = $time;
        }
    }
    foreach ($actions as $quid => $notused) {
        ksort($actions[$quid]->responses);
    }
    return $actions;
}


/**
 * Returns the html for question feedback image.
 * @param float   $fraction  value representing the correctness of the user's
 *                           response to a question.
 * @param boolean $selected  whether or not the answer is the one that the
 *                           user picked.
 * @return string
 */
function question_get_feedback_image($fraction, $selected=true) {

    global $CFG;

    if ($fraction >= 1.0) {
        if ($selected) {
            $feedbackimg = '<img src="'.$CFG->pixpath.'/i/tick_green_big.gif" '.
                            'alt="'.get_string('correct', 'quiz').'" class="icon" />';
        } else {
            $feedbackimg = '<img src="'.$CFG->pixpath.'/i/tick_green_small.gif" '.
                            'alt="'.get_string('correct', 'quiz').'" class="icon" />';
        }
    } else if ($fraction > 0.0 && $fraction < 1.0) {
        if ($selected) {
            $feedbackimg = '<img src="'.$CFG->pixpath.'/i/tick_amber_big.gif" '.
                            'alt="'.get_string('partiallycorrect', 'quiz').'" class="icon" />';
        } else {
            $feedbackimg = '<img src="'.$CFG->pixpath.'/i/tick_amber_small.gif" '.
                            'alt="'.get_string('partiallycorrect', 'quiz').'" class="icon" />';
        }
    } else {
        if ($selected) {
            $feedbackimg = '<img src="'.$CFG->pixpath.'/i/cross_red_big.gif" '.
                            'alt="'.get_string('incorrect', 'quiz').'" class="icon" />';
        } else {
            $feedbackimg = '<img src="'.$CFG->pixpath.'/i/cross_red_small.gif" '.
                            'alt="'.get_string('incorrect', 'quiz').'" class="icon" />';
        }
    }
    return $feedbackimg;
}


/**
 * Returns the class name for question feedback.
 * @param float  $fraction  value representing the correctness of the user's
 *                          response to a question.
 * @return string
 */
function question_get_feedback_class($fraction) {

    global $CFG;

    if ($fraction >= 1.0) {
        $class = 'correct';
    } else if ($fraction > 0.0 && $fraction < 1.0) {
        $class = 'partiallycorrect';
    } else {
        $class = 'incorrect';
    }
    return $class;
}


/**
* For a given question in an attempt we walk the complete history of states
* and recalculate the grades as we go along.
*
* This is used when a question is changed and old student
* responses need to be marked with the new version of a question.
*
* TODO: Make sure this is not quiz-specific
*
* @return boolean            Indicates whether the grade has changed
* @param object  $question   A question object
* @param object  $attempt    The attempt, in which the question needs to be regraded.
* @param object  $cmoptions
* @param boolean $verbose    Optional. Whether to print progress information or not.
*/
function regrade_question_in_attempt($question, $attempt, $cmoptions, $verbose=false) {

    // load all states for this question in this attempt, ordered in sequence
    if ($states = get_records_select('question_states',
            "attempt = '{$attempt->uniqueid}' AND question = '{$question->id}'",
            'seq_number ASC')) {
        $states = array_values($states);

        // Subtract the grade for the latest state from $attempt->sumgrades to get the
        // sumgrades for the attempt without this question.
        $attempt->sumgrades -= $states[count($states)-1]->grade;

        // Initialise the replaystate
        $state = clone($states[0]);
        $state->manualcomment = get_field('question_sessions', 'manualcomment', 'attemptid',
                $attempt->uniqueid, 'questionid', $question->id);
        restore_question_state($question, $state);
        $state->sumpenalty = 0.0;
        $replaystate = clone($state);
        $replaystate->last_graded = $state;

        $changed = false;
        for($j = 1; $j < count($states); $j++) {
            restore_question_state($question, $states[$j]);
            $action = new stdClass;
            $action->responses = $states[$j]->responses;
            $action->timestamp = $states[$j]->timestamp;

            // Change event to submit so that it will be reprocessed
            if (QUESTION_EVENTCLOSE == $states[$j]->event
                    or QUESTION_EVENTGRADE == $states[$j]->event
                    or QUESTION_EVENTCLOSEANDGRADE == $states[$j]->event) {
                $action->event = QUESTION_EVENTSUBMIT;

            // By default take the event that was saved in the database
            } else {
                $action->event = $states[$j]->event;
            }

            if ($action->event == QUESTION_EVENTMANUALGRADE) {
                // Ensure that the grade is in range - in the past this was not checked,
                // but now it is (MDL-14835) - so we need to ensure the data is valid before
                // proceeding.
                if ($states[$j]->grade < 0) {
                    $states[$j]->grade = 0;
                } else if ($states[$j]->grade > $question->maxgrade) {
                    $states[$j]->grade = $question->maxgrade;
                }
                $error = question_process_comment($question, $replaystate, $attempt,
                        $replaystate->manualcomment, $states[$j]->grade);
                if (is_string($error)) {
                     notify($error);
                }
            } else {

                // Reprocess (regrade) responses
                if (!question_process_responses($question, $replaystate,
                        $action, $cmoptions, $attempt)) {
                    $verbose && notify("Couldn't regrade state #{$state->id}!");
                }
            }

            // We need rounding here because grades in the DB get truncated
            // e.g. 0.33333 != 0.3333333, but we want them to be equal here
            if ((round((float)$replaystate->raw_grade, 5) != round((float)$states[$j]->raw_grade, 5))
                    or (round((float)$replaystate->penalty, 5) != round((float)$states[$j]->penalty, 5))
                    or (round((float)$replaystate->grade, 5) != round((float)$states[$j]->grade, 5))) {
                $changed = true;
            }

            $replaystate->id = $states[$j]->id;
            $replaystate->changed = true;
            $replaystate->update = true; // This will ensure that the existing database entry is updated rather than a new one created
            save_question_session($question, $replaystate);
        }
        if ($changed) {
            // TODO, call a method in quiz to do this, where 'quiz' comes from
            // the question_attempts table.
            update_record('quiz_attempts', $attempt);
        }

        return $changed;
    }
    return false;
}

/**
* Processes an array of student responses, grading and saving them as appropriate
*
* @param object $question Full question object, passed by reference
* @param object $state    Full state object, passed by reference
* @param object $action   object with the fields ->responses which
*                         is an array holding the student responses,
*                         ->action which specifies the action, e.g., QUESTION_EVENTGRADE,
*                         and ->timestamp which is a timestamp from when the responses
*                         were submitted by the student.
* @param object $cmoptions
* @param object $attempt  The attempt is passed by reference so that
*                         during grading its ->sumgrades field can be updated
* @return boolean         Indicates success/failure
*/
function question_process_responses(&$question