Proyectos de Subversion Moodle

<?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.

//

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// 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/>.

/**

 * This file defines the class {@link question_definition} and its subclasses.

 *

 * The type hierarchy is quite complex. Here is a summary:

 * - question_definition

 *   - question_information_item

 *   - question_with_responses implements question_manually_gradable

 *     - question_graded_automatically implements question_automatically_gradable

 *       - question_graded_automatically_with_countback implements question_automatically_gradable_with_countback

 *       - question_graded_by_strategy

 *

 * Other classes:

 * - question_classified_response

 * - question_answer

 * - question_hint

 *   - question_hint_with_parts

 * - question_first_matching_answer_grading_strategy implements question_grading_strategy

 *

 * Other interfaces:

 * - question_response_answer_comparer

 *

 * @package    moodlecore

 * @subpackage questiontypes

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

use core_question\output\question_version_info;

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

/**

 * The definition of a question of a particular type.

 *

 * This class is a close match to the question table in the database.

 * Definitions of question of a particular type normally subclass one of the

 * more specific classes {@link question_with_responses},

 * {@link question_graded_automatically} or {@link question_information_item}.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

abstract class question_definition {

    /** @var integer id of the question in the datase, or null if this question

     * is not in the database. */

    public $id;

    /** @var integer question category id. */

    public $category;

    /** @var integer question context id. */

    public $contextid;

    /** @var integer parent question id. */

    public $parent = 0;

    /** @var question_type the question type this question is. */

    public $qtype;

    /** @var string question name. */

    public $name;

    /** @var string question text. */

    public $questiontext;

    /** @var integer question test format. */

    public $questiontextformat;

    /** @var string question general feedback. */

    public $generalfeedback;

    /** @var integer question test format. */

    public $generalfeedbackformat;

    /** @var float what this quetsion is marked out of, by default. */

    public $defaultmark = 1;

    /** @var integer How many question numbers this question consumes. */

    public $length = 1;

    /** @var number penalty factor of this question. */

    public $penalty = 0;

    /** @var string unique identifier of this question. */

    public $stamp;

    /** @var string question idnumber. */

    public $idnumber;

    /** @var integer timestamp when this question was created. */

    public $timecreated;

    /** @var integer timestamp when this question was modified. */

    public $timemodified;

    /** @var integer userid of the use who created this question. */

    public $createdby;

    /** @var integer userid of the use who modified this question. */

    public $modifiedby;

    /** @var array of question_hints. */

    public $hints = array();

    /** @var boolean question status hidden/ready/draft in the question bank. */

    public $status = \core_question\local\bank\question_version_status::QUESTION_STATUS_READY;

    /** @var int Version id of the question in a question bank */

    public $versionid;

    /** @var int Version number of the question in a question bank */

    public $version;

    /** @var int Bank entry id for the question */

    public $questionbankentryid;

    /** @var ?int The latest version of the question. null if we haven't checked yet. */

    protected $latestversion = null;

    /**

     * @var array of array of \core_customfield\data_controller objects indexed by fieldid for the questions custom fields.

     */

    public $customfields = array();

    /**

     * Constructor. Normally to get a question, you call

     * {@link question_bank::load_question()}, but questions can be created

     * directly, for example in unit test code.

     */

    public function __construct() {

    }

    /**

     * When a pending definition tries to read its latest version, fill in the latest version for all pending definitions

     *

     * @param string $name

     * @return mixed

     */

    public function __get($name) {

        if ($name === 'latestversion') {

            if (isset(question_version_info::$pendingdefinitions[$this->id])) {

                question_version_info::populate_latest_versions();

            }

            return $this->latestversion;

        }

    }

    /**

     * @return string the name of the question type (for example multichoice) that this

     * question is.

     */

    public function get_type_name() {

        return $this->qtype->name();

    }

    /**

     * Creat the appropriate behaviour for an attempt at this quetsion,

     * given the desired (archetypal) behaviour.

     *

     * This default implementation will suit most normal graded questions.

     *

     * If your question is of a patricular type, then it may need to do something

     * different. For example, if your question can only be graded manually, then

     * it should probably return a manualgraded behaviour, irrespective of

     * what is asked for.

     *

     * If your question wants to do somthing especially complicated is some situations,

     * then you may wish to return a particular behaviour related to the

     * one asked for. For example, you migth want to return a

     * qbehaviour_interactive_adapted_for_myqtype.

     *

     * @param question_attempt $qa the attempt we are creating a behaviour for.

     * @param string $preferredbehaviour the requested type of behaviour.

     * @return question_behaviour the new behaviour object.

     */

    public function make_behaviour(question_attempt $qa, $preferredbehaviour) {

        return question_engine::make_archetypal_behaviour($preferredbehaviour, $qa);

    }

    /**

     * Start a new attempt at this question, storing any information that will

     * be needed later in the step.

     *

     * This is where the question can do any initialisation required on a

     * per-attempt basis. For example, this is where the multiple choice

     * question type randomly shuffles the choices (if that option is set).

     *

     * Any information about how the question has been set up for this attempt

     * should be stored in the $step, by calling $step->set_qt_var(...).

     *

     * @param question_attempt_step The first step of the {@link question_attempt}

     *      being started. Can be used to store state.

     * @param int $varant which variant of this question to start. Will be between

     *      1 and {@link get_num_variants()} inclusive.

     */

    public function start_attempt(question_attempt_step $step, $variant) {

    }

    /**

     * When an in-progress {@link question_attempt} is re-loaded from the

     * database, this method is called so that the question can re-initialise

     * its internal state as needed by this attempt.

     *

     * For example, the multiple choice question type needs to set the order

     * of the choices to the order that was set up when start_attempt was called

     * originally. All the information required to do this should be in the

     * $step object, which is the first step of the question_attempt being loaded.

     *

     * @param question_attempt_step The first step of the {@link question_attempt}

     *      being loaded.

     */

    public function apply_attempt_state(question_attempt_step $step) {

    }

    /**

     * Verify if an attempt at this question can be re-graded using the other question version.

     *

     * To put it another way, will {@see update_attempt_state_date_from_old_version()} be able to work?

     *

     * It is expected that this relationship is symmetrical, so if you can regrade from V1 to V3, then

     * you can change back from V3 to V1.

     *

     * @param question_definition $otherversion a different version of the question to use in the regrade.

     * @return string|null null if the regrade can proceed, else a reason why not.

     */

    public function validate_can_regrade_with_other_version(question_definition $otherversion): ?string {

        if (get_class($otherversion) !== get_class($this)) {

            return get_string('cannotregradedifferentqtype', 'question');

        }

        return null;

    }

    /**

     * Update the data representing the initial state of an attempt another version of this question, to allow for the changes.

     *

     * What is required is probably most easily understood using an example. Think about multiple choice questions.

     * The first step has a variable '_order' which is a comma-separated list of question_answer ids.

     * A different version of the question will have different question_answers with different ids. However, the list of

     * choices should be similar, and so we need to shuffle the new list of ids in the same way that the old one was.

     *

     * Note: be sure to return all the data that was originally in $oldstep, while updating the fields that

     * require it. Otherwise you might break features like 'Each attempt builds on last' in the quiz.

     *

     * This method should only be called if {@see validate_can_regrade_with_other_version()} did not

     * flag up a potential problem. So, this method will throw a {@see coding_exception} if it is not

     * possible to work out a return value.

     *

     * @param question_attempt_step $oldstep the first step of a {@see question_attempt} at $oldquestion.

     * @param question_definition $oldquestion the previous version of the question, which $oldstate comes from.

     * @return array the submit data which can be passed to {@see apply_attempt_state} to start

     *     an attempt at this version of this question, corresponding to the attempt at the old question.

     * @throws coding_exception if this can't be done.

     */

    public function update_attempt_state_data_for_new_version(

            question_attempt_step $oldstep, question_definition $oldquestion) {

        $message = $this->validate_can_regrade_with_other_version($oldquestion);

        if ($message) {

            throw new coding_exception($message);

        }

        return $oldstep->get_qt_data();

    }

    /**

     * Generate a brief, plain-text, summary of this question. This is used by

     * various reports. This should show the particular variant of the question

     * as presented to students. For example, the calculated quetsion type would

     * fill in the particular numbers that were presented to the student.

     * This method will return null if such a summary is not possible, or

     * inappropriate.

     * @return string|null a plain text summary of this question.

     */

    public function get_question_summary() {

        return $this->html_to_text($this->questiontext, $this->questiontextformat);

    }

    /**

     * @return int the number of vaiants that this question has.

     */

    public function get_num_variants() {

        return 1;

    }

    /**

     * @return string that can be used to seed the pseudo-random selection of a

     *      variant.

     */

    public function get_variants_selection_seed() {

        return $this->stamp;

    }

    /**

     * Some questions can return a negative mark if the student gets it wrong.

     *

     * This method returns the lowest mark the question can return, on the

     * fraction scale. that is, where the maximum possible mark is 1.0.

     *

     * @return float minimum fraction this question will ever return.

     */

    public function get_min_fraction() {

        return 0;

    }

    /**

     * Some questions can return a mark greater than the maximum.

     *

     * This method returns the lowest highest the question can return, on the

     * fraction scale. that is, where the nominal maximum mark is 1.0.

     *

     * @return float maximum fraction this question will ever return.

     */

    public function get_max_fraction() {

        return 1;

    }

    /**

     * Given a response, rest the parts that are wrong.

     * @param array $response a response

     * @return array a cleaned up response with the wrong bits reset.

     */

    public function clear_wrong_from_response(array $response) {

        return array();

    }

    /**

     * Return the number of subparts of this response that are right.

     * @param array $response a response

     * @return array with two elements, the number of correct subparts, and

     * the total number of subparts.

     */

    public function get_num_parts_right(array $response) {

        return array(null, null);

    }

    /**

     * @param moodle_page the page we are outputting to.

     * @return qtype_renderer the renderer to use for outputting this question.

     */

    public function get_renderer(moodle_page $page) {

        return $page->get_renderer($this->qtype->plugin_name());

    }

    /**

     * What data may be included in the form submission when a student submits

     * this question in its current state?

     *

     * This information is used in calls to optional_param. The parameter name

     * has {@link question_attempt::get_field_prefix()} automatically prepended.

     *

     * @return array|string variable name => PARAM_... constant, or, as a special case

     *      that should only be used in unavoidable, the constant question_attempt::USE_RAW_DATA

     *      meaning take all the raw submitted data belonging to this question.

     */

    abstract public function get_expected_data();

    /**

     * What data would need to be submitted to get this question correct.

     * If there is more than one correct answer, this method should just

     * return one possibility. If it is not possible to compute a correct

     * response, this method should return null.

     *

     * @return array|null parameter name => value.

     */

    abstract public function get_correct_response();

    /**

     * Takes an array of values representing a student response represented in a way that is understandable by a human and

     * transforms that to the response as the POST values returned from the HTML form that takes the student response during a

     * student attempt. Primarily this is used when reading csv values from a file of student responses in order to be able to

     * simulate the student interaction with a quiz.

     *

     * In most cases the array will just be returned as is. Some question types will need to transform the keys of the array,

     * as the meaning of the keys in the html form is deliberately obfuscated so that someone looking at the html does not get an

     * advantage. The values that represent the response might also be changed in order to more meaningful to a human.

     *

     * See the examples of question types that have overridden this in core and also see the csv files of simulated student

     * responses used in unit tests in :

     * - mod/quiz/tests/fixtures/stepsXX.csv

     * - mod/quiz/report/responses/tests/fixtures/steps00.csv

     * - mod/quiz/report/statistics/tests/fixtures/stepsXX.csv

     *

     * Also see {@link https://github.com/jamiepratt/moodle-quiz_simulate}, a quiz report plug in for uploading and downloading

     * student responses as csv files.

     *

     * @param array $simulatedresponse an array of data representing a student response

     * @return array a response array as would be returned from the html form (but without prefixes)

     */

    public function prepare_simulated_post_data($simulatedresponse) {

        return $simulatedresponse;

    }

    /**

     * Does the opposite of {@link prepare_simulated_post_data}.

     *

     * This takes a student response (the POST values returned from the HTML form that takes the student response during a

     * student attempt) it then represents it in a way that is understandable by a human.

     *

     * Primarily this is used when creating a file of csv from real student responses in order later to be able to

     * simulate the same student interaction with a quiz later.

     *

     * @param string[] $realresponse the response array as was returned from the form during a student attempt (without prefixes).

     * @return string[] an array of data representing a student response.

     */

    public function get_student_response_values_for_simulation($realresponse) {

        return $realresponse;

    }

    /**

     * Apply {@link format_text()} to some content with appropriate settings for

     * this question.

     *

     * @param string $text some content that needs to be output.

     * @param int $format the FORMAT_... constant.

     * @param question_attempt $qa the question attempt.

     * @param string $component used for rewriting file area URLs.

     * @param string $filearea used for rewriting file area URLs.

     * @param bool $clean Whether the HTML needs to be cleaned. Generally,

     *      parts of the question do not need to be cleaned, and student input does.

     * @return string the text formatted for output by format_text.

     */

    public function format_text($text, $format, $qa, $component, $filearea, $itemid,

            $clean = false) {

        $formatoptions = new stdClass();

        $formatoptions->noclean = !$clean;

        $formatoptions->para = false;

        $text = $qa->rewrite_pluginfile_urls($text, $component, $filearea, $itemid);

        return format_text($text, $format, $formatoptions);

    }

    /**

     * Convert some part of the question text to plain text. This might be used,

     * for example, by get_response_summary().

     * @param string $text The HTML to reduce to plain text.

     * @param int $format the FORMAT_... constant.

     * @return string the equivalent plain text.

     */

    public function html_to_text($text, $format) {

        return question_utils::to_plain_text($text, $format);

    }

    /** @return the result of applying {@link format_text()} to the question text. */

    public function format_questiontext($qa) {

        return $this->format_text($this->questiontext, $this->questiontextformat,

                $qa, 'question', 'questiontext', $this->id);

    }

    /** @return the result of applying {@link format_text()} to the general feedback. */

    public function format_generalfeedback($qa) {

        return $this->format_text($this->generalfeedback, $this->generalfeedbackformat,

                $qa, 'question', 'generalfeedback', $this->id);

    }

    /**

     * Take some HTML that should probably already be a single line, like a

     * multiple choice choice, or the corresponding feedback, and make it so that

     * it is suitable to go in a place where the HTML must be inline, like inside a <p> tag.

     * @param string $html to HTML to fix up.

     * @return string the fixed HTML.

     */

    public function make_html_inline($html) {

        $html = preg_replace('~\s*<p>\s*~u', '', $html);

        $html = preg_replace('~\s*</p>\s*~u', '<br />', $html);

        $html = preg_replace('~(<br\s*/?>)+$~u', '', $html);

        return trim($html);

    }

    /**

     * Checks whether the users is allow to be served a particular file.

     * @param question_attempt $qa the question attempt being displayed.

     * @param question_display_options $options the options that control display of the question.

     * @param string $component the name of the component we are serving files for.

     * @param string $filearea the name of the file area.

     * @param array $args the remaining bits of the file path.

     * @param bool $forcedownload whether the user must be forced to download the file.

     * @return bool true if the user can access this file.

     */

    public function check_file_access($qa, $options, $component, $filearea, $args, $forcedownload) {

        if ($component == 'question' && $filearea == 'questiontext') {

            // Question text always visible, but check it is the right question id.

            return $args[0] == $this->id;

        } else if ($component == 'question' && $filearea == 'generalfeedback') {

            return $options->generalfeedback && $args[0] == $this->id;

        } else {

            // Unrecognised component or filearea.

            return false;

        }

    }

    /**

     * Return the question settings that define this question as structured data.

     *

     * This is used by external systems such as the Moodle mobile app, which want to display the question themselves,

     * rather than using the renderer provided.

     *

     * This method should only return the data that the student is allowed to see or know, given the current state of

     * the question. For example, do not include the 'General feedback' until the student has completed the question,

     * and even then, only include it if the question_display_options say it should be visible.

     *

     * But, within those rules, it is recommended that you return all the settings for the question,

     * to give maximum flexibility to the external system providing its own rendering of the question.

     *

     * @param question_attempt $qa the current attempt for which we are exporting the settings.

     * @param question_display_options $options the question display options which say which aspects of the question

     * should be visible.

     * @return mixed structure representing the question settings. In web services, this will be JSON-encoded.

     */

    public function get_question_definition_for_external_rendering(question_attempt $qa, question_display_options $options) {

        debugging('This question does not implement the get_question_definition_for_external_rendering() method yet.',

            DEBUG_DEVELOPER);

        return null;

    }

    /**

     * Set the latest version.

     *

     * Making $this->latestversion public would break the magic __get() behaviour above, so allow it to be set externally.

     *

     * @param int $latestversion

     * @return void

     */

    public function set_latest_version(int $latestversion): void {

        $this->latestversion = $latestversion;

    }

}

/**

 * This class represents a 'question' that actually does not allow the student

 * to respond, like the description 'question' type.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class question_information_item extends question_definition {

    public function __construct() {

        parent::__construct();

        $this->defaultmark = 0;

        $this->penalty = 0;

        $this->length = 0;

    }

    public function make_behaviour(question_attempt $qa, $preferredbehaviour) {

        return question_engine::make_behaviour('informationitem', $qa, $preferredbehaviour);

    }

    public function get_expected_data() {

        return array();

    }

    public function get_correct_response() {

        return array();

    }

    public function get_question_summary() {

        return null;

    }

}

/**

 * Interface that a {@link question_definition} must implement to be usable by

 * the manual graded behaviour.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

interface question_manually_gradable {

    /**

     * Use by many of the behaviours to determine whether the student

     * has provided enough of an answer for the question to be graded automatically,

     * or whether it must be considered aborted.

     *

     * @param array $response responses, as returned by

     *      {@link question_attempt_step::get_qt_data()}.

     * @return bool whether this response can be graded.

     */

    public function is_gradable_response(array $response);

    /**

     * Used by many of the behaviours, to work out whether the student's

     * response to the question is complete. That is, whether the question attempt

     * should move to the COMPLETE or INCOMPLETE state.

     *

     * @param array $response responses, as returned by

     *      {@link question_attempt_step::get_qt_data()}.

     * @return bool whether this response is a complete answer to this question.

     */

    public function is_complete_response(array $response);

    /**

     * Use by many of the behaviours to determine whether the student's

     * response has changed. This is normally used to determine that a new set

     * of responses can safely be discarded.

     *

     * @param array $prevresponse the responses previously recorded for this question,

     *      as returned by {@link question_attempt_step::get_qt_data()}

     * @param array $newresponse the new responses, in the same format.

     * @return bool whether the two sets of responses are the same - that is

     *      whether the new set of responses can safely be discarded.

     */

    public function is_same_response(array $prevresponse, array $newresponse);

    /**

     * Produce a plain text summary of a response.

     * @param array $response a response, as might be passed to {@link grade_response()}.

     * @return string a plain text summary of that response, that could be used in reports.

     */

    public function summarise_response(array $response);

    /**

     * If possible, construct a response that could have lead to the given

     * response summary. This is basically the opposite of {@link summarise_response()}

     * but it is intended only to be used for testing.

     *

     * @param string $summary a string, which might have come from summarise_response

     * @return array a response that could have lead to that.

     */

    public function un_summarise_response(string $summary);

    /**

     * Categorise the student's response according to the categories defined by

     * get_possible_responses.

     * @param $response a response, as might be passed to {@link grade_response()}.

     * @return array subpartid => {@link question_classified_response} objects.

     *      returns an empty array if no analysis is possible.

     */

    public function classify_response(array $response);

}

/**

 * This class is used in the return value from

 * {@link question_manually_gradable::classify_response()}.

 *

 * @copyright  2010 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class question_classified_response {

    /**

     * @var string the classification of this response the student gave to this

     * part of the question. Must match one of the responseclasses returned by

     * {@link question_type::get_possible_responses()}.

     */

    public $responseclassid;

    /** @var string the actual response the student gave to this part. */

    public $response;

    /** @var number the fraction this part of the response earned. */

    public $fraction;

    /**

     * Constructor, just an easy way to set the fields.

     * @param string $responseclassid see the field descriptions above.

     * @param string $response see the field descriptions above.

     * @param number $fraction see the field descriptions above.

     */

    public function __construct($responseclassid, $response, $fraction) {

        $this->responseclassid = $responseclassid;

        $this->response = $response;

        $this->fraction = $fraction;

    }

    public static function no_response() {

        return new question_classified_response(null, get_string('noresponse', 'question'), null);

    }

}

/**

 * Interface that a {@link question_definition} must implement to be usable by

 * the various automatic grading behaviours.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

interface question_automatically_gradable extends question_manually_gradable {

    /**

     * In situations where is_gradable_response() returns false, this method

     * should generate a description of what the problem is.

     * @return string the message.

     */

    public function get_validation_error(array $response);

    /**

     * Grade a response to the question, returning a fraction between

     * get_min_fraction() and get_max_fraction(), and the corresponding {@link question_state}

     * right, partial or wrong.

     * @param array $response responses, as returned by

     *      {@link question_attempt_step::get_qt_data()}.

     * @return array (float, integer) the fraction, and the state.

     */

    public function grade_response(array $response);

    /**

     * Get one of the question hints. The question_attempt is passed in case

     * the question type wants to do something complex. For example, the

     * multiple choice with multiple responses question type will turn off most

     * of the hint options if the student has selected too many opitions.

     * @param int $hintnumber Which hint to display. Indexed starting from 0

     * @param question_attempt $qa The question_attempt.

     */

    public function get_hint($hintnumber, question_attempt $qa);

    /**

     * Generate a brief, plain-text, summary of the correct answer to this question.

     * This is used by various reports, and can also be useful when testing.

     * This method will return null if such a summary is not possible, or

     * inappropriate.

     * @return string|null a plain text summary of the right answer to this question.

     */

    public function get_right_answer_summary();

}

/**

 * Interface that a {@link question_definition} must implement to be usable by

 * the interactivecountback behaviour.

 *

 * @copyright  2010 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

interface question_automatically_gradable_with_countback extends question_automatically_gradable {

    /**

     * Work out a final grade for this attempt, taking into account all the

     * tries the student made.

     * @param array $responses the response for each try. Each element of this

     * array is a response array, as would be passed to {@link grade_response()}.

     * There may be between 1 and $totaltries responses.

     * @param int $totaltries The maximum number of tries allowed.

     * @return numeric the fraction that should be awarded for this

     * sequence of response.

     */

    public function compute_final_grade($responses, $totaltries);

}

/**

 * This class represents a real question. That is, one that is not a

 * {@link question_information_item}.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

abstract class question_with_responses extends question_definition

        implements question_manually_gradable {

    public function classify_response(array $response) {

        return array();

    }

    public function is_gradable_response(array $response) {

        return $this->is_complete_response($response);

    }

    public function un_summarise_response(string $summary) {

        throw new coding_exception('This question type (' . get_class($this) .

                ' does not implement the un_summarise_response testing method.');

    }

}

/**

 * This class represents a question that can be graded automatically.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

abstract class question_graded_automatically extends question_with_responses

        implements question_automatically_gradable {

    /** @var Some question types have the option to show the number of sub-parts correct. */

    public $shownumcorrect = false;

    public function get_right_answer_summary() {

        $correctresponse = $this->get_correct_response();

        if (empty($correctresponse)) {

            return null;

        }

        return $this->summarise_response($correctresponse);

    }

    /**

     * Check a request for access to a file belonging to a combined feedback field.

     * @param question_attempt $qa the question attempt being displayed.

     * @param question_display_options $options the options that control display of the question.

     * @param string $filearea the name of the file area.

     * @param array $args the remaining bits of the file path.

     * @return bool whether access to the file should be allowed.

     */

    protected function check_combined_feedback_file_access($qa, $options, $filearea, $args = null) {

        $state = $qa->get_state();

        if ($args === null) {

            debugging('You must pass $args as the fourth argument to check_combined_feedback_file_access.',

                    DEBUG_DEVELOPER);

            $args = array($this->id); // Fake it for now, so the rest of this method works.

        }

        if (!$state->is_finished()) {

            $response = $qa->get_last_qt_data();

            if (!$this->is_gradable_response($response)) {

                return false;

            }

            list($notused, $state) = $this->grade_response($response);

        }

        return $options->feedback && $state->get_feedback_class() . 'feedback' == $filearea &&

                $args[0] == $this->id;

    }

    /**

     * Check a request for access to a file belonging to a hint.

     * @param question_attempt $qa the question attempt being displayed.

     * @param question_display_options $options the options that control display of the question.

     * @param array $args the remaining bits of the file path.

     * @return bool whether access to the file should be allowed.

     */

    protected function check_hint_file_access($qa, $options, $args) {

        if (!$options->feedback) {

            return false;

        }

        $hint = $qa->get_applicable_hint();

        $hintid = reset($args); // Itemid is hint id.

        return $hintid == $hint->id;

    }

    public function get_hint($hintnumber, question_attempt $qa) {

        if (!isset($this->hints[$hintnumber])) {

            return null;

        }

        return $this->hints[$hintnumber];

    }

    public function format_hint(question_hint $hint, question_attempt $qa) {

        return $this->format_text($hint->hint, $hint->hintformat, $qa,

                'question', 'hint', $hint->id);

    }

}

/**

 * This class represents a question that can be graded automatically with

 * countback grading in interactive mode.

 *

 * @copyright  2010 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

abstract class question_graded_automatically_with_countback

        extends question_graded_automatically

        implements question_automatically_gradable_with_countback {

    public function make_behaviour(question_attempt $qa, $preferredbehaviour) {

        if ($preferredbehaviour == 'interactive') {

            return question_engine::make_behaviour('interactivecountback',

                    $qa, $preferredbehaviour);

        }

        return question_engine::make_archetypal_behaviour($preferredbehaviour, $qa);

    }

}

/**

 * This class represents a question that can be graded automatically by using

 * a {@link question_grading_strategy}.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

abstract class question_graded_by_strategy extends question_graded_automatically {

    /** @var question_grading_strategy the strategy to use for grading. */

    protected $gradingstrategy;

    /** @param question_grading_strategy  $strategy the strategy to use for grading. */

    public function __construct(question_grading_strategy $strategy) {

        parent::__construct();

        $this->gradingstrategy = $strategy;

    }

    public function get_correct_response() {

        $answer = $this->get_correct_answer();

        if (!$answer) {

            return array();

        }

        return array('answer' => $answer->answer);

    }

    /**

     * Get an answer that contains the feedback and fraction that should be

     * awarded for this resonse.

     * @param array $response a response.

     * @return question_answer the matching answer.

     */

    public function get_matching_answer(array $response) {

        return $this->gradingstrategy->grade($response);

    }

    /**

     * @return question_answer an answer that contains the a response that would

     *      get full marks.

     */

    public function get_correct_answer() {

        return $this->gradingstrategy->get_correct_answer();

    }

    public function grade_response(array $response) {

        $answer = $this->get_matching_answer($response);

        if ($answer) {

            return array($answer->fraction,

                    question_state::graded_state_for_fraction($answer->fraction));

        } else {

            return array(0, question_state::$gradedwrong);

        }

    }

    public function classify_response(array $response) {

        if (empty($response['answer'])) {

            return array($this->id => question_classified_response::no_response());

        }

        $ans = $this->get_matching_answer($response);

        if (!$ans) {

            return array($this->id => new question_classified_response(

                    0, $response['answer'], 0));

        }

        return array($this->id => new question_classified_response(

                $ans->id, $response['answer'], $ans->fraction));

    }

}

/**

 * Class to represent a question answer, loaded from the question_answers table

 * in the database.

 *

 * @copyright  2009 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class question_answer {

    /** @var integer the answer id. */

    public $id;

    /** @var string the answer. */

    public $answer;

    /** @var integer one of the FORMAT_... constans. */

    public $answerformat = FORMAT_PLAIN;

    /** @var number the fraction this answer is worth. */

    public $fraction;

    /** @var string the feedback for this answer. */

    public $feedback;

    /** @var integer one of the FORMAT_... constans. */

    public $feedbackformat;

    /**

     * Constructor.

     * @param int $id the answer.

     * @param string $answer the answer.

     * @param number $fraction the fraction this answer is worth.

     * @param string $feedback the feedback for this answer.

     * @param int $feedbackformat the format of the feedback.

     */

    public function __construct($id, $answer, $fraction, $feedback, $feedbackformat) {

        $this->id = $id;

        $this->answer = $answer;

        $this->fraction = $fraction;

        $this->feedback = $feedback;

        $this->feedbackformat = $feedbackformat;

    }

}

/**

 * Class to represent a hint associated with a question.

 * Used by iteractive mode, etc. A question has an array of these.

 *

 * @copyright  2010 The Open University

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class question_hint {

    /** @var integer The hint id. */