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.

//

// 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/>.

/**

 * Represents an ordering question.

 *

 * @package    qtype_ordering

 * @copyright  2013 Gordon Bateson (gordon.bateson@gmail.com)

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

 */

class qtype_ordering_question extends question_graded_automatically {

    /** Select all answers */

    const SELECT_ALL = 0;

    /** Select random set of answers */

    const SELECT_RANDOM = 1;

    /** Select contiguous subset of answers */

    const SELECT_CONTIGUOUS = 2;

    /** Show answers in vertical list */

    const LAYOUT_VERTICAL = 0;

    /** Show answers in one horizontal line */

    const LAYOUT_HORIZONTAL = 1;

    /** The minimum number of items to create a subset */

    const MIN_SUBSET_ITEMS = 2;

    /** Default value for numberingstyle */

    const NUMBERING_STYLE_DEFAULT = 'none';

    /** @var int Zero grade on any error */

    const GRADING_ALL_OR_NOTHING = -1;

    /** @var int Counts items, placed into right absolute place */

    const GRADING_ABSOLUTE_POSITION = 0;

    /** @var int Every sequential pair in right order is graded (last pair is excluded) */

    const GRADING_RELATIVE_NEXT_EXCLUDE_LAST = 1;

    /** @var int Every sequential pair in right order is graded (last pair is included) */

    const GRADING_RELATIVE_NEXT_INCLUDE_LAST = 2;

    /** @var int Single answers that are placed before and after each answer is graded if in right order*/

    const GRADING_RELATIVE_ONE_PREVIOUS_AND_NEXT = 3;

    /** @var int All answers that are placed before and after each answer is graded if in right order*/

    const GRADING_RELATIVE_ALL_PREVIOUS_AND_NEXT = 4;

    /** @var int Only longest ordered subset is graded */

    const GRADING_LONGEST_ORDERED_SUBSET = 5;

    /** @var int Only longest ordered and contiguous subset is graded */

    const GRADING_LONGEST_CONTIGUOUS_SUBSET = 6;

    /** @var int Items are graded relative to their position in the correct answer */

    const GRADING_RELATIVE_TO_CORRECT = 7;

    /** @var int {@see LAYOUT_VERTICAL} or {@see LAYOUT_HORIZONTAL}. */

    public $layouttype;

    /** @var int {@see SELECT_ALL}, {@see SELECT_RANDOM} or {@see SELECT_CONTIGUOUS}. */

    public $selecttype;

    /** @var int if {@see $selecttype} is not SELECT_ALL, then the number to select. */

    public $selectcount;

    /** @var int Which grading strategy to use. One of the GRADING_... constants. */

    public $gradingtype;

    /** @var bool Should details of the grading calculation be shown to students. */

    public $showgrading;

    /** @var string How to number the items. A key from the array returned by {@see get_numbering_styles()}. */

    public $numberingstyle;

    // Fields from "qtype_ordering_options" table.

    /** @var string */

    public $correctfeedback;

    /** @var int */

    public $correctfeedbackformat;

    /** @var string */

    public $incorrectfeedback;

    /** @var int */

    public $incorrectfeedbackformat;

    /** @var string */

    public $partiallycorrectfeedback;

    /** @var int */

    public $partiallycorrectfeedbackformat;

    /** @var array Records from "question_answers" table */

    public $answers;

    /** @var array of answerids in correct order */

    public $correctresponse;

    /** @var array contatining current order of answerids */

    public $currentresponse;

    /** @var array of scored for every item */

    protected $itemscores = [];

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

        $countanswers = count($this->answers);

        // Sanitize "selecttype".

        $selecttype = $this->selecttype;

        $selecttype = max(0, $selecttype);

        $selecttype = min(2, $selecttype);

        // Sanitize "selectcount".

        $selectcount = $this->selectcount;

        $selectcount = max(self::MIN_SUBSET_ITEMS, $selectcount);

        $selectcount = min($countanswers, $selectcount);

        // Ensure consistency between "selecttype" and "selectcount".

        switch (true) {

            case ($selecttype == self::SELECT_ALL):

                $selectcount = $countanswers;

                break;

            case ($selectcount == $countanswers):

                $selecttype = self::SELECT_ALL;

                break;

        }

        // Extract answer ids.

        switch ($selecttype) {

            case self::SELECT_ALL:

                $answerids = array_keys($this->answers);

                break;

            case self::SELECT_RANDOM:

                $answerids = array_rand($this->answers, $selectcount);

                break;

            case self::SELECT_CONTIGUOUS:

                $answerids = array_keys($this->answers);

                $offset = mt_rand(0, $countanswers - $selectcount);

                $answerids = array_slice($answerids, $offset, $selectcount);

                break;

        }

        $this->correctresponse = $answerids;

        $step->set_qt_var('_correctresponse', implode(',', $this->correctresponse));

        shuffle($answerids);

        $this->currentresponse = $answerids;

        $step->set_qt_var('_currentresponse', implode(',', $this->currentresponse));

    }

    public function apply_attempt_state(question_attempt_step $step) {

        $this->currentresponse = array_filter(explode(',', $step->get_qt_var('_currentresponse')));

        $this->correctresponse = array_filter(explode(',', $step->get_qt_var('_correctresponse')));

    }

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

        $basemessage = parent::validate_can_regrade_with_other_version($otherversion);

        if ($basemessage) {

            return $basemessage;

        }

        if (count($this->answers) != count($otherversion->answers)) {

            return get_string('regradeissuenumitemschanged', 'qtype_ordering');

        }

        return null;

    }

    public function update_attempt_state_data_for_new_version(

            question_attempt_step $oldstep, question_definition $oldquestion) {

        parent::update_attempt_state_data_for_new_version($oldstep, $oldquestion);

        $mapping = array_combine(array_keys($oldquestion->answers), array_keys($this->answers));

        $oldorder = explode(',', $oldstep->get_qt_var('_currentresponse'));

        $neworder = [];

        foreach ($oldorder as $oldid) {

            $neworder[] = $mapping[$oldid] ?? $oldid;

        }

        $oldcorrect = explode(',', $oldstep->get_qt_var('_correctresponse'));

        $newcorrect = [];

        foreach ($oldcorrect as $oldid) {

            $newcorrect[] = $mapping[$oldid] ?? $oldid;

        }

        return [

            '_currentresponse' => implode(',', $neworder),

            '_correctresponse' => implode(',', $newcorrect),

        ];

    }

    public function get_expected_data() {

        $name = $this->get_response_fieldname();

        return [$name => PARAM_TEXT];

    }

    public function get_correct_response() {

        $correctresponse = $this->correctresponse;

        foreach ($correctresponse as $position => $answerid) {

            $answer = $this->answers[$answerid];

            $correctresponse[$position] = $answer->md5key;

        }

        $name = $this->get_response_fieldname();

        return [$name => implode(',', $correctresponse)];

    }

    public function summarise_response(array $response) {

        $name = $this->get_response_fieldname();

        $items = [];

        if (array_key_exists($name, $response)) {

            $items = explode(',', $response[$name]);

        }

        $answerids = [];

        foreach ($this->answers as $answer) {

            $answerids[$answer->md5key] = $answer->id;

        }

        foreach ($items as $i => $item) {

            if (array_key_exists($item, $answerids)) {

                $item = $this->answers[$answerids[$item]];

                $item = $this->html_to_text($item->answer, $item->answerformat);

                $item = shorten_text($item, 10, true); // Force truncate at 10 chars.

                $items[$i] = $item;

            } else {

                $items[$i] = ''; // Shouldn't happen!

            }

        }

        return implode('; ', array_filter($items));

    }

    public function classify_response(array $response) {

        $this->update_current_response($response);

        $fraction = 1 / count($this->correctresponse);

        $classifiedresponse = [];

        foreach ($this->correctresponse as $position => $answerid) {

            if (in_array($answerid, $this->currentresponse)) {

                $currentposition = array_search($answerid, $this->currentresponse);

            }

            $answer = $this->answers[$answerid];

            $subqid = question_utils::to_plain_text($answer->answer, $answer->answerformat);

            // Truncate responses longer than 100 bytes because they cannot be stored in the database.

            // CAUTION: This will mess up answers which are not unique within the first 100 chars!

            $maxbytes = 100;

            if (strlen($subqid) > $maxbytes) {

                // If the truncation point is in the middle of a multi-byte unicode char,

                // we remove the incomplete part with a preg_match() that is unicode aware.

                $subqid = substr($subqid, 0, $maxbytes);

                if (preg_match('/^(.|\n)*/u', '', $subqid, $match)) {

                    $subqid = $match[0];

                }

            }

            $classifiedresponse[$subqid] = new question_classified_response(

                $currentposition + 1,

                get_string('positionx', 'qtype_ordering', $currentposition + 1),

                ($currentposition == $position) * $fraction

            );

        }

        return $classifiedresponse;

    }

    public function is_complete_response(array $response) {

        return true;

    }

    public function is_gradable_response(array $response) {

        return true;

    }

    public function get_validation_error(array $response) {

        return '';

    }

    public function is_same_response(array $old, array $new) {

        $name = $this->get_response_fieldname();

        return (isset($old[$name]) && isset($new[$name]) && $old[$name] == $new[$name]);

    }

    public function grade_response(array $response) {

        $this->update_current_response($response);

        $countcorrect = 0;

        $countanswers = 0;

        $gradingtype = $this->gradingtype;

        switch ($gradingtype) {

            case self::GRADING_ALL_OR_NOTHING:

            case self::GRADING_ABSOLUTE_POSITION:

                $correctresponse = $this->correctresponse;

                $currentresponse = $this->currentresponse;

                foreach ($correctresponse as $position => $answerid) {

                    if (array_key_exists($position, $currentresponse)) {

                        if ($currentresponse[$position] == $answerid) {

                            $countcorrect++;

                        }

                    }

                    $countanswers++;

                }

                if ($gradingtype == self::GRADING_ALL_OR_NOTHING && $countcorrect < $countanswers) {

                    $countcorrect = 0;

                }

                break;

            case self::GRADING_RELATIVE_NEXT_EXCLUDE_LAST:

            case self::GRADING_RELATIVE_NEXT_INCLUDE_LAST:

                $lastitem = ($gradingtype == self::GRADING_RELATIVE_NEXT_INCLUDE_LAST);

                $currentresponse = $this->get_next_answerids($this->currentresponse, $lastitem);

                $correctresponse = $this->get_next_answerids($this->correctresponse, $lastitem);

                foreach ($correctresponse as $thisanswerid => $nextanswerid) {

                    if (array_key_exists($thisanswerid, $currentresponse)) {

                        if ($currentresponse[$thisanswerid] == $nextanswerid) {

                            $countcorrect++;

                        }

                    }

                    $countanswers++;

                }

                break;

            case self::GRADING_RELATIVE_ONE_PREVIOUS_AND_NEXT:

            case self::GRADING_RELATIVE_ALL_PREVIOUS_AND_NEXT:

                $all = ($gradingtype == self::GRADING_RELATIVE_ALL_PREVIOUS_AND_NEXT);

                $currentresponse = $this->get_previous_and_next_answerids($this->currentresponse, $all);

                $correctresponse = $this->get_previous_and_next_answerids($this->correctresponse, $all);

                foreach ($correctresponse as $thisanswerid => $answerids) {

                    if (array_key_exists($thisanswerid, $currentresponse)) {

                        $prev = $currentresponse[$thisanswerid]->prev;

                        $prev = array_intersect($prev, $answerids->prev);

                        $countcorrect += count($prev);

                        $next = $currentresponse[$thisanswerid]->next;

                        $next = array_intersect($next, $answerids->next);

                        $countcorrect += count($next);

                    }

                    $countanswers += count($answerids->prev);

                    $countanswers += count($answerids->next);

                }

                break;

            case self::GRADING_LONGEST_ORDERED_SUBSET:

            case self::GRADING_LONGEST_CONTIGUOUS_SUBSET:

                $contiguous = ($gradingtype == self::GRADING_LONGEST_CONTIGUOUS_SUBSET);

                $subset = $this->get_ordered_subset($contiguous);

                $countcorrect = count($subset);

                $countanswers = count($this->currentresponse);

                break;

            case self::GRADING_RELATIVE_TO_CORRECT:

                $correctresponse = $this->correctresponse;

                $currentresponse = $this->currentresponse;

                $count = (count($correctresponse) - 1);

                foreach ($correctresponse as $position => $answerid) {

                    if (in_array($answerid, $currentresponse)) {

                        $currentposition = array_search($answerid, $currentresponse);

                        $currentscore = ($count - abs($position - $currentposition));

                        if ($currentscore > 0) {

                            $countcorrect += $currentscore;

                        }

                    }

                    $countanswers += $count;

                }

                break;

        }

        if ($countanswers == 0) {

            $fraction = 0;

        } else {

            $fraction = ($countcorrect / $countanswers);

        }

        return [

            $fraction,

            question_state::graded_state_for_fraction($fraction),

        ];

    }

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

        if ($component == 'question') {

            if ($filearea == 'answer') {

                $answerid = reset($args); // Value of "itemid" is answer id.

                return array_key_exists($answerid, $this->answers);

            }

            if (in_array($filearea, ['correctfeedback', 'partiallycorrectfeedback', 'incorrectfeedback'])) {

                return $this->check_combined_feedback_file_access($qa, $options, $filearea, $args);

            }

            if ($filearea == 'hint') {

                return $this->check_hint_file_access($qa, $options, $args);

            }

        }

        return parent::check_file_access($qa, $options, $component, $filearea, $args, $forcedownload);

    }

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

        $state = $qa->get_state();

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

            $response = $qa->get_last_qt_data();

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

                return false;

            }

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

        }

        if ($state->get_feedback_class().'feedback' == $filearea) {

            return ($this->id == reset($args));

        } else {

            return false;

        }

    }

    // Custom methods.

    /**

     * Returns response mform field name

     *

     * @return string

     */

    public function get_response_fieldname(): string {

        return 'response_' . $this->id;

    }

    /**

     * Unpack the students' response into an array which updates the question currentresponse.

     *

     * @param array $response Form data

     */

    public function update_current_response(array $response) {

        $name = $this->get_response_fieldname();

        if (array_key_exists($name, $response)) {

            $ids = explode(',', $response[$name]);

            foreach ($ids as $i => $id) {

                foreach ($this->answers as $answer) {

                    if ($id == $answer->md5key) {

                        $ids[$i] = $answer->id;

                        break;

                    }

                }

            }

            // Note: TH mentions that this is a bit of a hack.

            $this->currentresponse = $ids;

        }

    }

    /**

     * Returns layoutclass

     *

     * @return string

     */

    public function get_ordering_layoutclass(): string {

        switch ($this->layouttype) {

            case self::LAYOUT_VERTICAL:

                return 'vertical';

            case self::LAYOUT_HORIZONTAL:

                return 'horizontal';

            default:

                return ''; // Shouldn't happen!

        }

    }

    /**

     * Returns array of next answers

     *

     * @param array $answerids array of answers id

     * @param bool $lastitem Include last item?

     * @return array of id of next answer

     */

    public function get_next_answerids(array $answerids, bool $lastitem = false): array {

        $nextanswerids = [];

        $imax = count($answerids);

        $imax--;

        if ($lastitem) {

            $nextanswerid = 0;

        } else {

            $nextanswerid = $answerids[$imax];

            $imax--;

        }

        for ($i = $imax; $i >= 0; $i--) {

            $thisanswerid = $answerids[$i];

            $nextanswerids[$thisanswerid] = $nextanswerid;

            $nextanswerid = $thisanswerid;

        }

        return $nextanswerids;

    }

    /**

     * Returns prev and next answers array

     *

     * @param array $answerids array of answers id

     * @param bool $all include all answers

     * @return array of array('prev' => previd, 'next' => nextid)

     */

    public function get_previous_and_next_answerids(array $answerids, bool $all = false): array {

        $prevnextanswerids = [];

        $next = $answerids;

        $prev = [];

        while ($answerid = array_shift($next)) {

            if ($all) {

                $prevnextanswerids[$answerid] = (object) [

                    'prev' => $prev,

                    'next' => $next,

                ];

            } else {

                $prevnextanswerids[$answerid] = (object) [

                    'prev' => [empty($prev) ? 0 : $prev[0]],

                    'next' => [empty($next) ? 0 : $next[0]],

                ];

            }

            array_unshift($prev, $answerid);

        }

        return $prevnextanswerids;

    }

    /**

     * Search for best ordered subset

     *

     * @param bool $contiguous A flag indicating whether only contiguous values should be considered for inclusion in the subset.

     * @return array

     */

    public function get_ordered_subset(bool $contiguous): array {

        $positions = $this->get_ordered_positions($this->correctresponse, $this->currentresponse);

        $subsets = $this->get_ordered_subsets($positions, $contiguous);

        // The best subset (longest and leftmost).

        $bestsubset = [];

        // The length of the best subset

        // initializing this to 1 means

        // we ignore single item subsets.

        $bestcount = 1;

        foreach ($subsets as $subset) {

            $count = count($subset);

            if ($count > $bestcount) {

                $bestcount = $count;

                $bestsubset = $subset;

            }

        }

        return $bestsubset;

    }

    /**

     * Get array of right answer positions for current response

     *

     * @param array $correctresponse

     * @param array $currentresponse

     * @return array

     */

    public function get_ordered_positions(array $correctresponse, array $currentresponse): array {

        $positions = [];

        foreach ($currentresponse as $answerid) {

            $positions[] = array_search($answerid, $correctresponse);

        }

        return $positions;

    }

    /**

     * Get all ordered subsets in the positions array

     *

     * @param array $positions maps an item's current position to its correct position

     * @param bool $contiguous TRUE if searching only for contiguous subsets; otherwise FALSE

     * @return array of ordered subsets from within the $positions array

     */

    public function get_ordered_subsets(array $positions, bool $contiguous): array {

        // Var $subsets is the collection of all subsets within $positions.

        $subsets = [];

        // Loop through the values at each position.

        foreach ($positions as $p => $value) {

            // Is $value a "new" value that cannot be added to any $subsets found so far?

            $isnew = true;

            // An array of new and saved subsets to be added to $subsets.

            $new = [];

            // Append the current value to any subsets to which it belongs

            // i.e. any subset whose end value is less than the current value.

            foreach ($subsets as $s => $subset) {

                // Get value at end of $subset.

                $end = $positions[end($subset)];

                switch (true) {

                    case ($value == ($end + 1)):

                        // For a contiguous value, we simply append $p to the subset.

                        $isnew = false;

                        $subsets[$s][] = $p;

                        break;

                    case $contiguous:

                        // If the $contiguous flag is set, we ignore non-contiguous values.

                        break;

                    case ($value > $end):

                        // For a non-contiguous value, we save the subset so far,

                        // because a value between $end and $value may be found later,

                        // and then append $p to the subset.

                        $isnew = false;

                        $new[] = $subset;

                        $subsets[$s][] = $p;

                        break;

                }

            }

            // If this is a "new" value, add it as a new subset.

            if ($isnew) {

                $new[] = [$p];

            }

            // Append any "new" subsets that were found during this iteration.

            if (count($new)) {

                $subsets = array_merge($subsets, $new);

            }

        }

        return $subsets;

    }

    /**

     * Helper function for get_select_types, get_layout_types, get_grading_types

     *

     * @param array $types

     * @param int $type

     * @return array|string array if $type is not specified and single string if $type is specified

     * @throws coding_exception

     * @codeCoverageIgnore

     */

    public static function get_types(array $types, $type): array|string {

        if ($type === null) {

            return $types; // Return all $types.

        }

        if (array_key_exists($type, $types)) {

            return $types[$type]; // One $type.

        }

        throw new coding_exception('Invalid type: ' . $type);

    }

    /**

     * Returns available values and descriptions for field "selecttype"

     *

     * @param int|null $type

     * @return array|string array if $type is not specified and single string if $type is specified

     * @codeCoverageIgnore

     */

    public static function get_select_types(?int $type = null): array|string {

        $plugin = 'qtype_ordering';

        $types = [

            self::SELECT_ALL => get_string('selectall', $plugin),

            self::SELECT_RANDOM => get_string('selectrandom', $plugin),

            self::SELECT_CONTIGUOUS => get_string('selectcontiguous', $plugin),

        ];

        return self::get_types($types, $type);

    }

    /**

     * Returns available values and descriptions for field "layouttype"

     *

     * @param int|null $type

     * @return array|string array if $type is not specified and single string if $type is specified

     * @codeCoverageIgnore

     */

    public static function get_layout_types(?int $type = null): array|string {

        $plugin = 'qtype_ordering';

        $types = [

            self::LAYOUT_VERTICAL   => get_string('vertical',   $plugin),

            self::LAYOUT_HORIZONTAL => get_string('horizontal', $plugin),

        ];

        return self::get_types($types, $type);

    }

    /**

     * Returns available values and descriptions for field "gradingtype"

     *

     * @param int|null $type

     * @return array|string array if $type is not specified and single string if $type is specified

     * @codeCoverageIgnore

     */

    public static function get_grading_types(?int $type = null): array|string {

        $plugin = 'qtype_ordering';

        $types = [

            self::GRADING_ALL_OR_NOTHING => get_string('allornothing', $plugin),

            self::GRADING_ABSOLUTE_POSITION => get_string('absoluteposition', $plugin),

            self::GRADING_RELATIVE_TO_CORRECT => get_string('relativetocorrect', $plugin),

            self::GRADING_RELATIVE_NEXT_EXCLUDE_LAST => get_string('relativenextexcludelast', $plugin),

            self::GRADING_RELATIVE_NEXT_INCLUDE_LAST => get_string('relativenextincludelast', $plugin),

            self::GRADING_RELATIVE_ONE_PREVIOUS_AND_NEXT => get_string('relativeonepreviousandnext', $plugin),

            self::GRADING_RELATIVE_ALL_PREVIOUS_AND_NEXT => get_string('relativeallpreviousandnext', $plugin),

            self::GRADING_LONGEST_ORDERED_SUBSET => get_string('longestorderedsubset', $plugin),

            self::GRADING_LONGEST_CONTIGUOUS_SUBSET => get_string('longestcontiguoussubset', $plugin),

        ];

        return self::get_types($types, $type);

    }

    /**

     * Get the numbering styles supported.

     *

     * For each style, there should be a corresponding lang string 'numberingstylexxx' in the qtype_ordering language file,

     * a case in the switch statement in number_in_style, and it should be listed in the definition of this column in install.xml.

     *

     * @param string|null $style The specific numbering style to retrieve.

     * @return array|string Numbering style(s).

     *                      The keys are style identifiers, and the values are the corresponding language strings.

     * @codeCoverageIgnore

     */

    public static function get_numbering_styles(?string $style = null): array|string {

        $plugin = 'qtype_ordering';

        $styles = [

            'none' => get_string('numberingstylenone', $plugin),

            'abc' => get_string('numberingstyleabc', $plugin),

            'ABCD' => get_string('numberingstyleABCD', $plugin),

            '123' => get_string('numberingstyle123', $plugin),

            'iii' => get_string('numberingstyleiii', $plugin),

            'IIII' => get_string('numberingstyleIIII', $plugin),

        ];

        return self::get_types($styles, $style);

    }

    /**

     * Return the number of subparts of this response that are correct|partial|incorrect.

     *

     * @param array $response A response.

     * @return array Array of three elements: the number of correct subparts,

     * the number of partial correct subparts and the number of incorrect subparts.

     */

    public function get_num_parts_right(array $response): array {

        $this->update_current_response($response);

        $gradingtype = $this->gradingtype;

        $numright = 0;

        $numpartial = 0;

        $numincorrect = 0;

        list($correctresponse, $currentresponse) = $this->get_response_depend_on_grading_type($gradingtype);

        foreach ($this->currentresponse as $position => $answerid) {

            [$fraction, $score, $maxscore] =

                $this->get_fraction_maxscore_score_of_item($position, $answerid, $correctresponse, $currentresponse);

            if (is_null($fraction)) {

                continue;

            }

            if ($fraction > 0.999999) {

                $numright++;

            } else if ($fraction < 0.000001) {

                $numincorrect++;

            } else {

                $numpartial++;

            }

        }

        return [$numright, $numpartial, $numincorrect];

    }

    /**

     * Returns the grade for one item, base on the fraction scale.

     *

     * @param int $position The position of the current response.

     * @param int $answerid The answerid of the current response.

     * @param array $correctresponse The correct response list base on grading type.

     * @param array $currentresponse The current response list base on grading type.

     * @return array.

     */

    protected function get_fraction_maxscore_score_of_item(

        int $position,

        int $answerid,

        array $correctresponse,

        array $currentresponse

    ): array {

        $gradingtype = $this->gradingtype;

        $score    = 0;

        $maxscore = null;

        switch ($gradingtype) {

            case self::GRADING_ALL_OR_NOTHING:

            case self::GRADING_ABSOLUTE_POSITION:

                if (isset($correctresponse[$position])) {

                    if ($correctresponse[$position] == $answerid) {

                        $score = 1;

                    }

                    $maxscore = 1;

                }

                break;

            case self::GRADING_RELATIVE_NEXT_EXCLUDE_LAST:

            case self::GRADING_RELATIVE_NEXT_INCLUDE_LAST:

                if (isset($correctresponse[$answerid])) {

                    if (isset($currentresponse[$answerid]) && $currentresponse[$answerid] == $correctresponse[$answerid]) {

                        $score = 1;

                    }

                    $maxscore = 1;

                }

                break;

            case self::GRADING_RELATIVE_ONE_PREVIOUS_AND_NEXT:

            case self::GRADING_RELATIVE_ALL_PREVIOUS_AND_NEXT:

                if (isset($correctresponse[$answerid])) {

                    $maxscore = 0;

                    $prev = $correctresponse[$answerid]->prev;

                    $maxscore += count($prev);

                    $prev = array_intersect($prev, $currentresponse[$answerid]->prev);

                    $score += count($prev);

                    $next = $correctresponse[$answerid]->next;

                    $maxscore += count($next);

                    $next = array_intersect($next, $currentresponse[$answerid]->next);

                    $score += count($next);

                }

                break;

            case self::GRADING_LONGEST_ORDERED_SUBSET:

            case self::GRADING_LONGEST_CONTIGUOUS_SUBSET:

                if (isset($correctresponse[$position])) {

                    if (isset($currentresponse[$position])) {

                        $score = $currentresponse[$position];

                    }

                    $maxscore = 1;

                }

                break;

            case self::GRADING_RELATIVE_TO_CORRECT:

                if (isset($correctresponse[$position])) {

                    $maxscore = (count($correctresponse) - 1);

                    $answerid = $currentresponse[$position];

                    $correctposition = array_search($answerid, $correctresponse);

                    $score = ($maxscore - abs($correctposition - $position));

                    if ($score < 0) {

                        $score = 0;

                    }

                }

                break;

        }

        $fraction = $maxscore ? $score / $maxscore : $maxscore;

        return [$fraction, $score, $maxscore];

    }

    /**

     * Get correcresponse and currentinfo depending on grading type.

     *

     * @param string $gradingtype The kind of grading.

     * @return array Correctresponse and currentresponsescore in one array.

     */

    protected function get_response_depend_on_grading_type(string $gradingtype): array {

        $correctresponse = [];

        $currentresponse = [];

        switch ($gradingtype) {

            case self::GRADING_ALL_OR_NOTHING:

            case self::GRADING_ABSOLUTE_POSITION:

            case self::GRADING_RELATIVE_TO_CORRECT:

                $correctresponse = $this->correctresponse;

                $currentresponse = $this->currentresponse;

                break;

            case self::GRADING_RELATIVE_NEXT_EXCLUDE_LAST:

            case self::GRADING_RELATIVE_NEXT_INCLUDE_LAST:

                $lastitem = ($gradingtype == self::GRADING_RELATIVE_NEXT_INCLUDE_LAST);

                $correctresponse = $this->get_next_answerids($this->correctresponse, $lastitem);

                $currentresponse = $this->get_next_answerids($this->currentresponse, $lastitem);

                break;

            case self::GRADING_RELATIVE_ONE_PREVIOUS_AND_NEXT:

            case self::GRADING_RELATIVE_ALL_PREVIOUS_AND_NEXT:

                $all = ($gradingtype == self::GRADING_RELATIVE_ALL_PREVIOUS_AND_NEXT);

                $correctresponse = $this->get_previous_and_next_answerids($this->correctresponse, $all);

                $currentresponse = $this->get_previous_and_next_answerids($this->currentresponse, $all);

                break;

            case self::GRADING_LONGEST_ORDERED_SUBSET:

            case self::GRADING_LONGEST_CONTIGUOUS_SUBSET:

                $correctresponse = $this->correctresponse;

                $currentresponse = $this->currentresponse;

                $contiguous = ($gradingtype == self::GRADING_LONGEST_CONTIGUOUS_SUBSET);

                $subset = $this->get_ordered_subset($contiguous);

                foreach ($currentresponse as $position => $answerid) {

                    if (array_search($position, $subset) === false) {

                        $currentresponse[$position] = 0;

                    } else {

                        $currentresponse[$position] = 1;

                    }

                }

                break;

        }

        return [$correctresponse, $currentresponse];

    }

    /**

     * Returns score for one item depending on correctness and question settings.

     *

     * @param question_definition $question question definition object

     * @param int $position The position of the current response.

     * @param int $answerid The answerid of the current response.

     * @return array (score, maxscore, fraction, percent, class)

     */

    public function get_ordering_item_score(question_definition $question, int $position, int $answerid): array {

        if (!isset($this->itemscores[$position])) {

            [$correctresponse, $currentresponse] = $this->get_response_depend_on_grading_type($this->gradingtype);

            $percent  = 0;    // 100 * $fraction.

            [$fraction, $score, $maxscore] =

                $this->get_fraction_maxscore_score_of_item($position, $answerid, $correctresponse, $currentresponse);

            if ($maxscore === null) {

                // An unscored item is either an illegal item

                // or last item of RELATIVE_NEXT_EXCLUDE_LAST

                // or an item in an incorrect ALL_OR_NOTHING

                // or an item from an unrecognized grading type.

                $class = 'unscored';

            } else {

                if ($maxscore > 0) {

                    $percent = round(100 * $fraction, 0);

                }

                $class = match (true) {

                    $fraction > 0.999999 => 'correct',

                    $fraction < 0.000001 => 'incorrect',

                    $fraction >= 0.66 => 'partial66',

                    $fraction >= 0.33 => 'partial33',

                    default => 'partial00',

                };

            }

            $itemscores = [

                'score' => $score,

                'maxscore' => $maxscore,

                'fraction' => $fraction,

                'percent' => $percent,

                'class' => $class,

            ];

            $this->itemscores[$position] = $itemscores;

        }

        return $this->itemscores[$position];

    }

}