/lib/formslib.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/>.

/**
 * formslib.php - library of classes for creating forms in Moodle, based on PEAR QuickForms.
 *
 * To use formslib then you will want to create a new file purpose_form.php eg. edit_form.php
 * and you want to name your class something like {modulename}_{purpose}_form. Your class will
 * extend moodleform overriding abstract classes definition and optionally defintion_after_data
 * and validation.
 *
 * See examples of use of this library in course/edit.php and course/edit_form.php
 *
 * A few notes :
 *      form definition is used for both printing of form and processing and should be the same
 *              for both or you may lose some submitted data which won't be let through.
 *      you should be using setType for every form element except select, radio or checkbox
 *              elements, these elements clean themselves.
 *
 * @package   core_form
 * @copyright 2006 Jamie Pratt <me@jamiep.org>
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

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

/** setup.php includes our hacked pear libs first */
require_once 'HTML/QuickForm.php';
require_once 'HTML/QuickForm/DHTMLRulesTableless.php';
require_once 'HTML/QuickForm/Renderer/Tableless.php';
require_once 'HTML/QuickForm/Rule.php';

require_once $CFG->libdir.'/filelib.php';

/**
 * EDITOR_UNLIMITED_FILES - hard-coded value for the 'maxfiles' option
 */
define('EDITOR_UNLIMITED_FILES', -1);

/**
 * Callback called when PEAR throws an error
 *
 * @param PEAR_Error $error
 */
function pear_handle_error($error){
    echo '<strong>'.$error->GetMessage().'</strong> '.$error->getUserInfo();
    echo '<br /> <strong>Backtrace </strong>:';
    print_object($error->backtrace);
}

if ($CFG->debugdeveloper) {
    //TODO: this is a wrong place to init PEAR!
    $GLOBALS['_PEAR_default_error_mode'] = PEAR_ERROR_CALLBACK;
    $GLOBALS['_PEAR_default_error_options'] = 'pear_handle_error';
}

/**
 * Initalize javascript for date type form element
 *
 * @staticvar bool $done make sure it gets initalize once.
 * @global moodle_page $PAGE
 */
function form_init_date_js() {
    global $PAGE;
    static $done = false;
    if (!$done) {
        $done = true;
        $calendar = \core_calendar\type_factory::get_calendar_instance();
        if ($calendar->get_name() !== 'gregorian') {
            // The YUI2 calendar only supports the gregorian calendar type.
            return;
        }
        $module   = 'moodle-form-dateselector';
        $function = 'M.form.dateselector.init_date_selectors';
        $defaulttimezone = date_default_timezone_get();

        $config = array(array(
            'firstdayofweek'    => $calendar->get_starting_weekday(),
            'mon'               => date_format_string(strtotime("Monday"), '%a', $defaulttimezone),
            'tue'               => date_format_string(strtotime("Tuesday"), '%a', $defaulttimezone),
            'wed'               => date_format_string(strtotime("Wednesday"), '%a', $defaulttimezone),
            'thu'               => date_format_string(strtotime("Thursday"), '%a', $defaulttimezone),
            'fri'               => date_format_string(strtotime("Friday"), '%a', $defaulttimezone),
            'sat'               => date_format_string(strtotime("Saturday"), '%a', $defaulttimezone),
            'sun'               => date_format_string(strtotime("Sunday"), '%a', $defaulttimezone),
            'january'           => date_format_string(strtotime("January 1"), '%B', $defaulttimezone),
            'february'          => date_format_string(strtotime("February 1"), '%B', $defaulttimezone),
            'march'             => date_format_string(strtotime("March 1"), '%B', $defaulttimezone),
            'april'             => date_format_string(strtotime("April 1"), '%B', $defaulttimezone),
            'may'               => date_format_string(strtotime("May 1"), '%B', $defaulttimezone),
            'june'              => date_format_string(strtotime("June 1"), '%B', $defaulttimezone),
            'july'              => date_format_string(strtotime("July 1"), '%B', $defaulttimezone),
            'august'            => date_format_string(strtotime("August 1"), '%B', $defaulttimezone),
            'september'         => date_format_string(strtotime("September 1"), '%B', $defaulttimezone),
            'october'           => date_format_string(strtotime("October 1"), '%B', $defaulttimezone),
            'november'          => date_format_string(strtotime("November 1"), '%B', $defaulttimezone),
            'december'          => date_format_string(strtotime("December 1"), '%B', $defaulttimezone)
        ));
        $PAGE->requires->yui_module($module, $function, $config);
    }
}

/**
 * Wrapper that separates quickforms syntax from moodle code
 *
 * Moodle specific wrapper that separates quickforms syntax from moodle code. You won't directly
 * use this class you should write a class definition which extends this class or a more specific
 * subclass such a moodleform_mod for each form you want to display and/or process with formslib.
 *
 * You will write your own definition() method which performs the form set up.
 *
 * @package   core_form
 * @copyright 2006 Jamie Pratt <me@jamiep.org>
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @todo      MDL-19380 rethink the file scanning
 */
abstract class moodleform {
    /** @var string name of the form */
    protected $_formname;       // form name

    /** @var MoodleQuickForm quickform object definition */
    protected $_form;

    /** @var array globals workaround */
    protected $_customdata;

    /** @var array submitted form data when using mforms with ajax */
    protected $_ajaxformdata;

    /** @var object definition_after_data executed flag */
    protected $_definition_finalized = false;

    /** @var bool|null stores the validation result of this form or null if not yet validated */
    protected $_validated = null;

    /**
     * The constructor function calls the abstract function definition() and it will then
     * process and clean and attempt to validate incoming data.
     *
     * It will call your custom validate method to validate data and will also check any rules
     * you have specified in definition using addRule
     *
     * The name of the form (id attribute of the form) is automatically generated depending on
     * the name you gave the class extending moodleform. You should call your class something
     * like
     *
     * @param mixed $action the action attribute for the form. If empty defaults to auto detect the
     *              current url. If a moodle_url object then outputs params as hidden variables.
     * @param mixed $customdata if your form defintion method needs access to data such as $course
     *              $cm, etc. to construct the form definition then pass it in this array. You can
     *              use globals for somethings.
     * @param string $method if you set this to anything other than 'post' then _GET and _POST will
     *               be merged and used as incoming data to the form.
     * @param string $target target frame for form submission. You will rarely use this. Don't use
     *               it if you don't need to as the target attribute is deprecated in xhtml strict.
     * @param mixed $attributes you can pass a string of html attributes here or an array.
     *               Special attribute 'data-random-ids' will randomise generated elements ids. This
     *               is necessary when there are several forms on the same page.
     *               Special attribute 'data-double-submit-protection' set to 'off' will turn off
     *               double-submit protection JavaScript - this may be necessary if your form sends
     *               downloadable files in response to a submit button, and can't call
     *               \core_form\util::form_download_complete();
     * @param bool $editable
     * @param array $ajaxformdata Forms submitted via ajax, must pass their data here, instead of relying on _GET and _POST.
     */
    public function __construct($action=null, $customdata=null, $method='post', $target='', $attributes=null, $editable=true,
                                $ajaxformdata=null) {
        global $CFG, $FULLME;
        // no standard mform in moodle should allow autocomplete with the exception of user signup
        if (empty($attributes)) {
            $attributes = array('autocomplete'=>'off');
        } else if (is_array($attributes)) {
            $attributes['autocomplete'] = 'off';
        } else {
            if (strpos($attributes, 'autocomplete') === false) {
                $attributes .= ' autocomplete="off" ';
            }
        }


        if (empty($action)){
            // do not rely on PAGE->url here because dev often do not setup $actualurl properly in admin_externalpage_setup()
            $action = strip_querystring($FULLME);
            if (!empty($CFG->sslproxy)) {
                // return only https links when using SSL proxy
                $action = preg_replace('/^http:/', 'https:', $action, 1);
            }
            //TODO: use following instead of FULLME - see MDL-33015
            //$action = strip_querystring(qualified_me());
        }
        // Assign custom data first, so that get_form_identifier can use it.
        $this->_customdata = $customdata;
        $this->_formname = $this->get_form_identifier();
        $this->_ajaxformdata = $ajaxformdata;

        $this->_form = new MoodleQuickForm($this->_formname, $method, $action, $target, $attributes, $ajaxformdata);
        if (!$editable){
            $this->_form->hardFreeze();
        }

        $this->definition();

        $this->_form->addElement('hidden', 'sesskey', null); // automatic sesskey protection
        $this->_form->setType('sesskey', PARAM_RAW);
        $this->_form->setDefault('sesskey', sesskey());
        $this->_form->addElement('hidden', '_qf__'.$this->_formname, null);   // form submission marker
        $this->_form->setType('_qf__'.$this->_formname, PARAM_RAW);
        $this->_form->setDefault('_qf__'.$this->_formname, 1);
        $this->_form->_setDefaultRuleMessages();

        // Hook to inject logic after the definition was provided.
        $this->after_definition();

        // we have to know all input types before processing submission ;-)
        $this->_process_submission($method);
    }

    /**
     * Old syntax of class constructor. Deprecated in PHP7.
     *
     * @deprecated since Moodle 3.1
     */
    public function moodleform($action=null, $customdata=null, $method='post', $target='', $attributes=null, $editable=true) {
        debugging('Use of class name as constructor is deprecated', DEBUG_DEVELOPER);
        self::__construct($action, $customdata, $method, $target, $attributes, $editable);
    }

    /**
     * It should returns unique identifier for the form.
     * Currently it will return class name, but in case two same forms have to be
     * rendered on same page then override function to get unique form identifier.
     * e.g This is used on multiple self enrollments page.
     *
     * @return string form identifier.
     */
    protected function get_form_identifier() {
        $class = get_class($this);

        return preg_replace('/[^a-z0-9_]/i', '_', $class);
    }

    /**
     * To autofocus on first form element or first element with error.
     *
     * @param string $name if this is set then the focus is forced to a field with this name
     * @return string javascript to select form element with first error or
     *                first element if no errors. Use this as a parameter
     *                when calling print_header
     */
    function focus($name=NULL) {
        $form =& $this->_form;
        $elkeys = array_keys($form->_elementIndex);
        $error = false;
        if (isset($form->_errors) &&  0 != count($form->_errors)){
            $errorkeys = array_keys($form->_errors);
            $elkeys = array_intersect($elkeys, $errorkeys);
            $error = true;
        }

        if ($error or empty($name)) {
            $names = array();
            while (empty($names) and !empty($elkeys)) {
                $el = array_shift($elkeys);
                $names = $form->_getElNamesRecursive($el);
            }
            if (!empty($names)) {
                $name = array_shift($names);
            }
        }

        $focus = '';
        if (!empty($name)) {
            $focus = 'forms[\''.$form->getAttribute('id').'\'].elements[\''.$name.'\']';
        }

        return $focus;
     }

    /**
     * Internal method. Alters submitted data to be suitable for quickforms processing.
     * Must be called when the form is fully set up.
     *
     * @param string $method name of the method which alters submitted data
     */
    function _process_submission($method) {
        $submission = array();
        if (!empty($this->_ajaxformdata)) {
            $submission = $this->_ajaxformdata;
        } else if ($method == 'post') {
            if (!empty($_POST)) {
                $submission = $_POST;
            }
        } else {
            $submission = $_GET;
            merge_query_params($submission, $_POST); // Emulate handling of parameters in xxxx_param().
        }

        // following trick is needed to enable proper sesskey checks when using GET forms
        // the _qf__.$this->_formname serves as a marker that form was actually submitted
        if (array_key_exists('_qf__'.$this->_formname, $submission) and $submission['_qf__'.$this->_formname] == 1) {
            if (!confirm_sesskey()) {
                print_error('invalidsesskey');
            }
            $files = $_FILES;
        } else {
            $submission = array();
            $files = array();
        }
        $this->detectMissingSetType();

        $this->_form->updateSubmission($submission, $files);
    }

    /**
     * Internal method - should not be used anywhere.
     * @deprecated since 2.6
     * @return array $_POST.
     */
    protected function _get_post_params() {
        return $_POST;
    }

    /**
     * Internal method. Validates all old-style deprecated uploaded files.
     * The new way is to upload files via repository api.
     *
     * @param array $files list of files to be validated
     * @return bool|array Success or an array of errors
     */
    function _validate_files(&$files) {
        global $CFG, $COURSE;

        $files = array();

        if (empty($_FILES)) {
            // we do not need to do any checks because no files were submitted
            // note: server side rules do not work for files - use custom verification in validate() instead
            return true;
        }

        $errors = array();
        $filenames = array();

        // now check that we really want each file
        foreach ($_FILES as $elname=>$file) {
            $required = $this->_form->isElementRequired($elname);

            if ($file['error'] == 4 and $file['size'] == 0) {
                if ($required) {
                    $errors[$elname] = get_string('required');
                }
                unset($_FILES[$elname]);
                continue;
            }

            if (!empty($file['error'])) {
                $errors[$elname] = file_get_upload_error($file['error']);
                unset($_FILES[$elname]);
                continue;
            }

            if (!is_uploaded_file($file['tmp_name'])) {
                // TODO: improve error message
                $errors[$elname] = get_string('error');
                unset($_FILES[$elname]);
                continue;
            }

            if (!$this->_form->elementExists($elname) or !$this->_form->getElementType($elname)=='file') {
                // hmm, this file was not requested
                unset($_FILES[$elname]);
                continue;
            }

            // NOTE: the viruses are scanned in file picker, no need to deal with them here.

            $filename = clean_param($_FILES[$elname]['name'], PARAM_FILE);
            if ($filename === '') {
                // TODO: improve error message - wrong chars
                $errors[$elname] = get_string('error');
                unset($_FILES[$elname]);
                continue;
            }
            if (in_array($filename, $filenames)) {
                // TODO: improve error message - duplicate name
                $errors[$elname] = get_string('error');
                unset($_FILES[$elname]);
                continue;
            }
            $filenames[] = $filename;
            $_FILES[$elname]['name'] = $filename;

            $files[$elname] = $_FILES[$elname]['tmp_name'];
        }

        // return errors if found
        if (count($errors) == 0){
            return true;

        } else {
            $files = array();
            return $errors;
        }
    }

    /**
     * Internal method. Validates filepicker and filemanager files if they are
     * set as required fields. Also, sets the error message if encountered one.
     *
     * @return bool|array with errors
     */
    protected function validate_draft_files() {
        global $USER;
        $mform =& $this->_form;

        $errors = array();
        //Go through all the required elements and make sure you hit filepicker or
        //filemanager element.
        foreach ($mform->_rules as $elementname => $rules) {
            $elementtype = $mform->getElementType($elementname);
            //If element is of type filepicker then do validation
            if (($elementtype == 'filepicker') || ($elementtype == 'filemanager')){
                //Check if rule defined is required rule
                foreach ($rules as $rule) {
                    if ($rule['type'] == 'required') {
                        $draftid = (int)$mform->getSubmitValue($elementname);
                        $fs = get_file_storage();
                        $context = context_user::instance($USER->id);
                        if (!$files = $fs->get_area_files($context->id, 'user', 'draft', $draftid, 'id DESC', false)) {
                            $errors[$elementname] = $rule['message'];
                        }
                    }
                }
            }
        }
        // Check all the filemanager elements to make sure they do not have too many
        // files in them.
        foreach ($mform->_elements as $element) {
            if ($element->_type == 'filemanager') {
                $maxfiles = $element->getMaxfiles();
                if ($maxfiles > 0) {
                    $draftid = (int)$element->getValue();
                    $fs = get_file_storage();
                    $context = context_user::instance($USER->id);
                    $files = $fs->get_area_files($context->id, 'user', 'draft', $draftid, '', false);
                    if (count($files) > $maxfiles) {
                        $errors[$element->getName()] = get_string('err_maxfiles', 'form', $maxfiles);
                    }
                }
            }
        }
        if (empty($errors)) {
            return true;
        } else {
            return $errors;
        }
    }

    /**
     * Load in existing data as form defaults. Usually new entry defaults are stored directly in
     * form definition (new entry form); this function is used to load in data where values
     * already exist and data is being edited (edit entry form).
     *
     * note: $slashed param removed
     *
     * @param stdClass|array $default_values object or array of default values
     */
    function set_data($default_values) {
        if (is_object($default_values)) {
            $default_values = (array)$default_values;
        }
        $this->_form->setDefaults($default_values);
    }

    /**
     * Check that form was submitted. Does not check validity of submitted data.
     *
     * @return bool true if form properly submitted
     */
    function is_submitted() {
        return $this->_form->isSubmitted();
    }

    /**
     * Checks if button pressed is not for submitting the form
     *
     * @staticvar bool $nosubmit keeps track of no submit button
     * @return bool
     */
    function no_submit_button_pressed(){
        static $nosubmit = null; // one check is enough
        if (!is_null($nosubmit)){
            return $nosubmit;
        }
        $mform =& $this->_form;
        $nosubmit = false;
        if (!$this->is_submitted()){
            return false;
        }
        foreach ($mform->_noSubmitButtons as $nosubmitbutton){
            if ($this->optional_param($nosubmitbutton, 0, PARAM_RAW)) {
                $nosubmit = true;
                break;
            }
        }
        return $nosubmit;
    }

    /**
     * Returns an element of multi-dimensional array given the list of keys
     *
     * Example:
     * $array['a']['b']['c'] = 13;
     * $v = $this->get_array_value_by_keys($array, ['a', 'b', 'c']);
     *
     * Will result it $v==13
     *
     * @param array $array
     * @param array $keys
     * @return mixed returns null if keys not present
     */
    protected function get_array_value_by_keys(array $array, array $keys) {
        $value = $array;
        foreach ($keys as $key) {
            if (array_key_exists($key, $value)) {
                $value = $value[$key];
            } else {
                return null;
            }
        }
        return $value;
    }

    /**
     * Checks if a parameter was passed in the previous form submission
     *
     * @param string $name the name of the page parameter we want, for example 'id' or 'element[sub][13]'
     * @param mixed  $default the default value to return if nothing is found
     * @param string $type expected type of parameter
     * @return mixed
     */
    public function optional_param($name, $default, $type) {
        $nameparsed = [];
        // Convert element name into a sequence of keys, for example 'element[sub][13]' -> ['element', 'sub', '13'].
        parse_str($name . '=1', $nameparsed);
        $keys = [];
        while (is_array($nameparsed)) {
            $key = key($nameparsed);
            $keys[] = $key;
            $nameparsed = $nameparsed[$key];
        }

        // Search for the element first in $this->_ajaxformdata, then in $_POST and then in $_GET.
        if (($value = $this->get_array_value_by_keys($this->_ajaxformdata ?? [], $keys)) !== null ||
            ($value = $this->get_array_value_by_keys($_POST, $keys)) !== null ||
            ($value = $this->get_array_value_by_keys($_GET, $keys)) !== null) {
            return $type == PARAM_RAW ? $value : clean_param($value, $type);
        }

        return $default;
    }

    /**
     * Check that form data is valid.
     * You should almost always use this, rather than {@link validate_defined_fields}
     *
     * @return bool true if form data valid
     */
    function is_validated() {
        //finalize the form definition before any processing
        if (!$this->_definition_finalized) {
            $this->_definition_finalized = true;
            $this->definition_after_data();
        }

        return $this->validate_defined_fields();
    }

    /**
     * Validate the form.
     *
     * You almost always want to call {@link is_validated} instead of this
     * because it calls {@link definition_after_data} first, before validating the form,
     * which is what you want in 99% of cases.
     *
     * This is provided as a separate function for those special cases where
     * you want the form validated before definition_after_data is called
     * for example, to selectively add new elements depending on a no_submit_button press,
     * but only when the form is valid when the no_submit_button is pressed,
     *
     * @param bool $validateonnosubmit optional, defaults to false.  The default behaviour
     *             is NOT to validate the form when a no submit button has been pressed.
     *             pass true here to override this behaviour
     *
     * @return bool true if form data valid
     */
    function validate_defined_fields($validateonnosubmit=false) {
        $mform =& $this->_form;
        if ($this->no_submit_button_pressed() && empty($validateonnosubmit)){
            return false;
        } elseif ($this->_validated === null) {
            $internal_val = $mform->validate();

            $files = array();
            $file_val = $this->_validate_files($files);
            //check draft files for validation and flag them if required files
            //are not in draft area.
            $draftfilevalue = $this->validate_draft_files();

            if ($file_val !== true && $draftfilevalue !== true) {
                $file_val = array_merge($file_val, $draftfilevalue);
            } else if ($draftfilevalue !== true) {
                $file_val = $draftfilevalue;
            } //default is file_val, so no need to assign.

            if ($file_val !== true) {
                if (!empty($file_val)) {
                    foreach ($file_val as $element=>$msg) {
                        $mform->setElementError($element, $msg);
                    }
                }
                $file_val = false;
            }

            // Give the elements a chance to perform an implicit validation.
            $element_val = true;
            foreach ($mform->_elements as $element) {
                if (method_exists($element, 'validateSubmitValue')) {
                    $value = $mform->getSubmitValue($element->getName());
                    $result = $element->validateSubmitValue($value);
                    if (!empty($result) && is_string($result)) {
                        $element_val = false;
                        $mform->setElementError($element->getName(), $result);
                    }
                }
            }

            // Let the form instance validate the submitted values.
            $data = $mform->exportValues();
            $moodle_val = $this->validation($data, $files);
            if ((is_array($moodle_val) && count($moodle_val)!==0)) {
                // non-empty array means errors
                foreach ($moodle_val as $element=>$msg) {
                    $mform->setElementError($element, $msg);
                }
                $moodle_val = false;

            } else {
                // anything else means validation ok
                $moodle_val = true;
            }

            $this->_validated = ($internal_val and $element_val and $moodle_val and $file_val);
        }
        return $this->_validated;
    }

    /**
     * Return true if a cancel button has been pressed resulting in the form being submitted.
     *
     * @return bool true if a cancel button has been pressed
     */
    function is_cancelled(){
        $mform =& $this->_form;
        if ($mform->isSubmitted()){
            foreach ($mform->_cancelButtons as $cancelbutton){
                if ($this->optional_param($cancelbutton, 0, PARAM_RAW)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Return submitted data if properly submitted or returns NULL if validation fails or
     * if there is no submitted data.
     *
     * note: $slashed param removed
     *
     * @return object submitted data; NULL if not valid or not submitted or cancelled
     */
    function get_data() {
        $mform =& $this->_form;

        if (!$this->is_cancelled() and $this->is_submitted() and $this->is_validated()) {
            $data = $mform->exportValues();
            unset($data['sesskey']); // we do not need to return sesskey
            unset($data['_qf__'.$this->_formname]);   // we do not need the submission marker too
            if (empty($data)) {
                return NULL;
            } else {
                return (object)$data;
            }
        } else {
            return NULL;
        }
    }

    /**
     * Return submitted data without validation or NULL if there is no submitted data.
     * note: $slashed param removed
     *
     * @return object submitted data; NULL if not submitted
     */
    function get_submitted_data() {
        $mform =& $this->_form;

        if ($this->is_submitted()) {
            $data = $mform->exportValues();
            unset($data['sesskey']); // we do not need to return sesskey
            unset($data['_qf__'.$this->_formname]);   // we do not need the submission marker too
            if (empty($data)) {
                return NULL;
            } else {
                return (object)$data;
            }
        } else {
            return NULL;
        }
    }

    /**
     * Save verified uploaded files into directory. Upload process can be customised from definition()
     *
     * @deprecated since Moodle 2.0
     * @todo MDL-31294 remove this api
     * @see moodleform::save_stored_file()
     * @see moodleform::save_file()
     * @param string $destination path where file should be stored
     * @return bool Always false
     */
    function save_files($destination) {
        debugging('Not used anymore, please fix code! Use save_stored_file() or save_file() instead');
        return false;
    }

    /**
     * Returns name of uploaded file.
     *
     * @param string $elname first element if null
     * @return string|bool false in case of failure, string if ok
     */
    function get_new_filename($elname=null) {
        global $USER;

        if (!$this->is_submitted() or !$this->is_validated()) {
            return false;
        }

        if (is_null($elname)) {
            if (empty($_FILES)) {
                return false;
            }
            reset($_FILES);
            $elname = key($_FILES);
        }

        if (empty($elname)) {
            return false;
        }

        $element = $this->_form->getElement($elname);

        if ($element instanceof MoodleQuickForm_filepicker || $element instanceof MoodleQuickForm_filemanager) {
            $values = $this->_form->exportValues($elname);
            if (empty($values[$elname])) {
                return false;
            }
            $draftid = $values[$elname];
            $fs = get_file_storage();
            $context = context_user::instance($USER->id);
            if (!$files = $fs->get_area_files($context->id, 'user', 'draft', $draftid, 'id DESC', false)) {
                return false;
            }
            $file = reset($files);
            return $file->get_filename();
        }

        if (!isset($_FILES[$elname])) {
            return false;
        }

        return $_FILES[$elname]['name'];
    }

    /**
     * Save file to standard filesystem
     *
     * @param string $elname name of element
     * @param string $pathname full path name of file
     * @param bool $override override file if exists
     * @return bool success
     */
    function save_file($elname, $pathname, $override=false) {
        global $USER;

        if (!$this->is_submitted() or !$this->is_validated()) {
            return false;
        }
        if (file_exists($pathname)) {
            if ($override) {
                if (!@unlink($pathname)) {
                    return false;
                }
            } else {
                return false;
            }
        }

        $element = $this->_form->getElement($elname);

        if ($element instanceof MoodleQuickForm_filepicker || $element instanceof MoodleQuickForm_filemanager) {
            $values = $this->_form->exportValues($elname);
            if (empty($values[$elname])) {
                return false;
            }
            $draftid = $values[$elname];
            $fs = get_file_storage();
            $context = context_user::instance($USER->id);
            if (!$files = $fs->get_area_files($context->id, 'user', 'draft', $draftid, 'id DESC', false)) {
                return false;
            }
            $file = reset($files);

            return $file->copy_content_to($pathname);

        } else if (isset($_FILES[$elname])) {
            return copy($_FILES[$elname]['tmp_name'], $pathname);
        }

        return false;
    }

    /**
     * Returns a temporary file, do not forget to delete after not needed any more.
     *
     * @param string $elname name of the elmenet
     * @return string|bool either string or false
     */
    function save_temp_file($elname) {
        if (!$this->get_new_filename($elname)) {
            return false;
        }
        if (!$dir = make_temp_directory('forms')) {
            return false;
        }
        if (!$tempfile = tempnam($dir, 'tempup_')) {
            return false;
        }
        if (!$this->save_file($elname, $tempfile, true)) {
            // something went wrong
            @unlink($tempfile);
            return false;
        }

        return $tempfile;
    }

    /**
     * Get draft files of a form element
     * This is a protected method which will be used only inside moodleforms
     *
     * @param string $elname name of element
     * @return array|bool|null
     */
    protected function get_draft_files($elname) {
        global $USER;

        if (!$this->is_submitted()) {
            return false;
        }

        $element = $this->_form->getElement($elname);

        if ($element instanceof MoodleQuickForm_filepicker || $element instanceof MoodleQuickForm_filemanager) {
            $values = $this->_form->exportValues($elname);
            if (empty($values[$elname])) {
                return false;
            }
            $draftid = $values[$elname];
            $fs = get_file_storage();
            $context = context_user::instance($USER->id);
            if (!$files = $fs->get_area_files($context->id, 'user', 'draft', $draftid, 'id DESC', false)) {
                return null;
            }
            return $files;
        }
        return null;
    }

    /**
     * Save file to local filesystem pool
     *
     * @param string $elname name of element
     * @param int $newcontextid id of context
     * @param string $newcomponent name of the component
     * @param string $newfilearea name of file area
     * @param int $newitemid item id
     * @param string $newfilepath path of file where it get stored
     * @param string $newfilename use specified filename, if not specified name of uploaded file used
     * @param bool $overwrite overwrite file if exists
     * @param int $newuserid new userid if required
     * @return mixed stored_file object or false if error; may throw exception if duplicate found
     */
    function save_stored_file($elname, $newcontextid, $newcomponent, $newfilearea, $newitemid, $newfilepath='/',
                              $newfilename=null, $overwrite=false, $newuserid=null) {
        global $USER;

        if (!$this->is_submitted() or !$this->is_validated()) {
            return false;
        }

        if (empty($newuserid)) {
            $newuserid = $USER->id;
        }

        $element = $this->_form->getElement($elname);
        $fs = get_file_storage();

        if ($element instanceof MoodleQuickForm_filepicker) {
            $values = $this->_form->exportValues($elname);
            if (empty($values[$elname])) {
                return false;
            }
            $draftid = $values[$elname];
            $context = context_user::instance($USER->id);
            if (!$files = $fs->get_area_files($context->id, 'user' ,'draft', $draftid, 'id DESC', false)) {
                return false;
            }
            $file = reset($files);
            if (is_null($newfilename)) {
                $newfilename = $file->get_filename();
            }

            if ($overwrite) {
                if ($oldfile = $fs->get_file($newcontextid, $newcomponent, $newfilearea, $newitemid, $newfilepath, $newfilename)) {
                    if (!$oldfile->delete()) {
                        return false;
                    }
                }
            }

            $file_record = array('contextid'=>$newcontextid, 'component'=>$newcomponent, 'filearea'=>$newfilearea, 'itemid'=>$newitemid,
                                 'filepath'=>$newfilepath, 'filename'=>$newfilename, 'userid'=>$newuserid);
            return $fs->create_file_from_storedfile($file_record, $file);

        } else if (isset($_FILES[$elname])) {
            $filename = is_null($newfilename) ? $_FILES[$elname]['name'] : $newfilename;

            if ($overwrite) {
                if ($oldfile = $fs->get_file($newcontextid, $newcomponent, $newfilearea, $newitemid, $newfilepath, $newfilename)) {
                    if (!$oldfile->delete()) {
                        return false;
                    }
                }
            }

            $file_record = array('contextid'=>$newcontextid, 'component'=>$newcomponent, 'filearea'=>$newfilearea, 'itemid'=>$newitemid,
                                 'filepath'=>$newfilepath, 'filename'=>$newfilename, 'userid'=>$newuserid);
            return $fs->create_file_from_pathname($file_record, $_FILES[$elname]['tmp_name']);
        }

        return false;
    }

    /**
     * Get content of uploaded file.
     *
     * @param string $elname name of file upload element
     * @return string|bool false in case of failure, string if ok
     */
    function get_file_content($elname) {
        global $USER;

        if (!$this->is_submitted() or !$this->is_validated()) {
            return false;
        }

        $element = $this->_form->getElement($elname);

        if ($element instanceof MoodleQuickForm_filepicker || $element instanceof MoodleQuickForm_filemanager) {
            $values = $this->_form->exportValues($elname);
            if (empty($values[$elname])) {
                return false;
            }
            $draftid = $values[$elname];
            $fs = get_file_storage();
            $context = context_user::instance($USER->id);
            if (!$files = $fs->get_area_files($context->id, 'user', 'draft', $draftid, 'id DESC', false)) {
                return false;
            }
            $file = reset($files);

            return $file->get_content();

        } else if (isset($_FILES[$elname])) {
            return file_get_contents($_FILES[$elname]['tmp_name']);
        }

        return false;
    }

    /**
     * Print html form.
     */
    function display() {
        //finalize the form definition if not yet done
        if (!$this->_definition_finalized) {
            $this->_definition_finalized = true;
            $this->definition_after_data();
        }

        $this->_form->display();
    }

    /**
     * Renders the html form (same as display, but returns the result).
     *
     * Note that you can only output this rendered result once per page, as
     * it contains IDs which must be unique.
     *
     * @return string HTML code for the form
     */
    public function render() {
        ob_start();
        $this->display();
        $out = ob_get_contents();
        ob_end_clean();
        return $out;
    }

    /**
     * Form definition. Abstract method - always override!
     */
    protected abstract function definition();

    /**
     * After definition hook.
     *
     * This is useful for intermediate classes to inject logic after the definition was
     * provided without requiring developers to call the parent {{@link self::definition()}}
     * as it's not obvious by design. The 'intermediate' class is 'MyClass extends
     * IntermediateClass extends moodleform'.
     *
     * Classes overriding this method should always call the parent. We may not add
     * anything specifically in this instance of the method, but intermediate classes
     * are likely to do so, and so it is a good practice to always call the parent.
     *
     * @return void
     */
    protected function after_definition() {
    }

    /**
     * Dummy stub method - override if you need to setup the form depending on current
     * values. This method is called after definition(), data submission and set_data().
     * All form setup that is dependent on form values should go in here.
     */
    function definition_after_data(){
    }

    /**
     * Dummy stub method - override if you needed to perform some extra validation.
     * If there are errors return array of errors ("fieldname"=>"error message"),
     * otherwise true if ok.
     *
     * Server side rules do not work for uploaded files, implement serverside rules here if needed.
     *
     * @param array $data array of ("fieldname"=>value) of submitted data
     * @param array $files array of uploaded files "element_name"=>tmp_file_path
     * @return array of "element_name"=>"error_description" if there are errors,
     *         or an empty array if everything is OK (true allowed for backwards compatibility too).
     */
    function validation($data, $files) {
        return array();
    }

    /**
     * Helper used by {@link repeat_elements()}.
     *
     * @param int $i the index of this element.
     * @param HTML_QuickForm_element $elementclone
     * @param array $namecloned array of names
     */
    function repeat_elements_fix_clone($i, $elementclone, &$namecloned) {
        $name = $elementclone->getName();
        $namecloned[] = $name;

        if (!empty($name)) {
            $elementclone->setName($name."[$i]");
        }

        if (is_a($elementclone, 'HTML_QuickForm_header')) {
            $value = $elementclone->_text;
            $elementclone->setValue(str_replace('{no}', ($i+1), $value));

        } else if (is_a($elementclone, 'HTML_QuickForm_submit') || is_a($elementclone, 'HTML_QuickForm_button')) {
            $elementclone->setValue(str_replace('{no}', ($i+1), $elementclone->getValue()));

        } else {
            $value=$elementclone->getLabel();
            $elementclone->setLabel(str_replace('{no}', ($i+1), $value));
        }
    }

    /**
     * Method to add a repeating group of elements to a form.
     *
     * @param array $elementobjs Array of elements or groups of elements that are to be repeated
     * @param int $repeats no of times to repeat elements initially
     * @param array $options a nested array. The first array key is the element name.
     *    the second array key is the type of option to set, and depend on that option,
     *    the value takes different forms.
     *         'default'    - default value to set. Can include '{no}' which is replaced by the repeat number.
     *         'type'       - PARAM_* type.
     *         'helpbutton' - array containing the helpbutton params.
     *         'disabledif' - array containing the disabledIf() arguments after the element name.
     *         'rule'       - array containing the addRule arguments after the element name.
     *         'expanded'   - whether this section of the form should be expanded by default. (Name be a header element.)
     *         'advanced'   - whether this element is hidden by 'Show more ...'.
     * @param string $repeathiddenname name for hidden element storing no of repeats in this form
     * @param string $addfieldsname name for button to add more fields
     * @param int $addfieldsno how many fields to add at a time
     * @param string $addstring name of button, {no} is replaced by no of blanks that will be added.
     * @param bool $addbuttoninside if true, don't call closeHeaderBefore($addfieldsname). Default false.
     * @param string $deletebuttonname if specified, treats the no-submit button with this name as a "delete element" button
     *         in each of the elements
     * @return int no of repeats of element in this page
     */
    public function repeat_elements($elementobjs, $repeats, $options, $repeathiddenname,
                                    $addfieldsname, $addfieldsno = 5, $addstring = null, $addbuttoninside = false,
                                    $deletebuttonname = '') {
        if ($addstring === null) {
            $addstring = get_string('addfields', 'form', $addfieldsno);
        } else {
            $addstring = str_ireplace('{no}', $addfieldsno, $addstring);
        }
        $repeats = $this->optional_param($repeathiddenname, $repeats, PARAM_INT);
        $addfields = $this->optional_param($addfieldsname, '', PARAM_TEXT);
        $oldrepeats = $repeats;
        if (!empty($addfields)){
            $repeats += $addfieldsno;
        }
        $mform =& $this->_form;
        $mform->registerNoSubmitButton($addfieldsname);
        $mform->addElement('hidden', $repeathiddenname, $repeats);
        $mform->setType($repeathiddenname, PARAM_INT);
        //value not to be overridden by submitted value
        $mform->setConstants(array($repeathiddenname=>$repeats));
        $namecloned = array();
        $no = 1;
        for ($i = 0; $i < $repeats; $i++) {
            if ($deletebuttonname) {
                $mform->registerNoSubmitButton($deletebuttonname . "[$i]");
                $isdeleted = $this->optional_param($deletebuttonname . "[$i]", false, PARAM_RAW) ||
                    $this->optional_param($deletebuttonname . "-hidden[$i]", false, PARAM_RAW);
                if ($isdeleted) {
                    $mform->addElement('hidden', $deletebuttonname . "-hidden[$i]", 1);
                    $mform->setType($deletebuttonname . "-hidden[$i]", PARAM_INT);
                    continue;
                }
            }
            foreach ($elementobjs as $elementobj){
                $elementclone = fullclone($elementobj);
                $this->repeat_elements_fix_clone($i, $elementclone, $namecloned);

                if ($elementclone instanceof HTML_QuickForm_group && !$elementclone->_appendName) {
                    foreach ($elementclone->getElements() as $el) {
                        $this->repeat_elements_fix_clone($i, $el, $namecloned);
                    }
                    $elementclone->setLabel(str_replace('{no}', $no, $elementclone->getLabel()));
                } else if ($elementobj instanceof \HTML_QuickForm_submit && $elementobj->getName() == $deletebuttonname) {
                    // Mark the "Delete" button as no-submit.
                    $onclick = $elementclone->getAttribute('onclick');
                    $skip = 'skipClientValidation = true;';
                    $onclick = ($onclick !== null) ? $skip . ' ' . $onclick : $skip;
                    $elementclone->updateAttributes(['data-skip-validation' => 1, 'data-no-submit' => 1, 'onclick' => $onclick]);
                }

                // Mark newly created elements, so they know not to look for any submitted data.
                if ($i >= $oldrepeats) {
                    $mform->note_new_repeat($elementclone->getName());
                }

                $mform->addElement($elementclone);
                $no++;
            }
        }
        for ($i=0; $i<$repeats; $i++) {
            foreach ($options as $elementname => $elementoptions){
                $pos=strpos($elementname, '[');
                if ($pos!==FALSE){
                    $realelementname = substr($elementname, 0, $pos)."[$i]";
                    $realelementname .= substr($elementname, $pos);
                }else {
                    $realelementname = $elementname."[$i]";
                }
                foreach ($elementoptions as  $option => $params){

                    switch ($option){
                        case 'default' :
                            $mform->setDefault($realelementname, str_replace('{no}', $i + 1, $params));
                            break;
                        case 'helpbutton' :
                            $params = array_merge(array($realelementname), $params);
                            call_user_func_array(array(&$mform, 'addHelpButton'), $params);
                            break;
                        case 'disabledif' :
                        case 'hideif' :
                            $pos = strpos($params[0], '[');
                            $ending = '';
                            if ($pos !== false) {
                                $ending = substr($params[0], $pos);
                                $params[0] = substr($params[0], 0, $pos);
                            }
                            foreach ($namecloned as $num => $name){
                                if ($params[0] == $name){
                                    $params[0] = $params[0] . "[$i]" . $ending;
                                    break;
                                }
                            }
                            $params = array_merge(array($realelementname), $params);
                            $function = ($option === 'disabledif') ? 'disabledIf' : 'hideIf';
                            call_user_func_array(array(&$mform, $function), $params);
                            break;
                        case 'rule' :
                            if (is_string($params)){
                                $params = array(null, $params, null, 'client');
                            }
                            $params = array_merge(array($realelementname), $params);
                            call_user_func_array(array(&$mform, 'addRule'), $params);
                            break;

                        case 'type':
             …

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