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/>.

/**

 * Book module local lib functions

 *

 * @package    mod_book

 * @copyright  2010-2011 Petr Skoda {@link http://skodak.org}

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

 */

defined('MOODLE_INTERNAL') || die;

require_once(__DIR__.'/lib.php');

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

/**

 * The following defines are used to define how the chapters and subchapters of a book should be displayed in that table of contents.

 * BOOK_NUM_NONE        No special styling will applied and the editor will be able to do what ever thay want in the title

 * BOOK_NUM_NUMBERS     Chapters and subchapters are numbered (1, 1.1, 1.2, 2, ...)

 * BOOK_NUM_BULLETS     Subchapters are indented and displayed with bullets

 * BOOK_NUM_INDENTED    Subchapters are indented

 */

define('BOOK_NUM_NONE',     '0');

define('BOOK_NUM_NUMBERS',  '1');

define('BOOK_NUM_BULLETS',  '2');

define('BOOK_NUM_INDENTED', '3');

/**

 * Preload book chapters and fix toc structure if necessary.

 *

 * Returns array of chapters with standard 'pagenum', 'id, pagenum, subchapter, title, content, contentformat, hidden'

 * and extra 'parent, number, subchapters, prev, next'.

 * Please note the content/text of chapters is not included.

 *

 * @param  stdClass $book

 * @return array of id=>chapter

 */

function book_preload_chapters($book) {

    global $DB;

    $chapters = $DB->get_records('book_chapters', array('bookid' => $book->id), 'pagenum', 'id, pagenum,

            subchapter, title, content, contentformat, hidden');

    if (!$chapters) {

        return array();

    }

    $prev = null;

    $prevsub = null;

    $first = true;

    $hidesub = true;

    $parent = null;

    $pagenum = 0; // chapter sort

    $i = 0;       // main chapter num

    $j = 0;       // subchapter num

    foreach ($chapters as $id => $ch) {

        $oldch = clone($ch);

        $pagenum++;

        $ch->pagenum = $pagenum;

        if ($first) {

            // book can not start with a subchapter

            $ch->subchapter = 0;

            $first = false;

        }

        if (!$ch->subchapter) {

            if ($ch->hidden) {

                if ($book->numbering == BOOK_NUM_NUMBERS) {

                    $ch->number = 'x';

                } else {

                    $ch->number = null;

                }

            } else {

                $i++;

                $ch->number = $i;

            }

            $j = 0;

            $prevsub = null;

            $hidesub = $ch->hidden;

            $parent = $ch->id;

            $ch->parent = null;

            $ch->subchapters = array();

        } else {

            $ch->parent = $parent;

            $ch->subchapters = null;

            $chapters[$parent]->subchapters[$ch->id] = $ch->id;

            if ($hidesub) {

                // all subchapters in hidden chapter must be hidden too

                $ch->hidden = 1;

            }

            if ($ch->hidden) {

                if ($book->numbering == BOOK_NUM_NUMBERS) {

                    $ch->number = 'x';

                } else {

                    $ch->number = null;

                }

            } else {

                $j++;

                $ch->number = $j;

            }

        }

        if ($oldch->subchapter != $ch->subchapter or $oldch->pagenum != $ch->pagenum or $oldch->hidden != $ch->hidden) {

            // update only if something changed

            $DB->update_record('book_chapters', $ch);

        }

        $chapters[$id] = $ch;

    }

    return $chapters;

}

/**

 * Returns the title for a given chapter

 *

 * @param int $chid

 * @param array $chapters

 * @param stdClass $book

 * @param context_module $context

 * @return string

 */

function book_get_chapter_title($chid, $chapters, $book, $context) {

    $ch = $chapters[$chid];

    $title = trim(format_string($ch->title, true, array('context'=>$context)));

    $numbers = array();

    if ($book->numbering == BOOK_NUM_NUMBERS) {

        if ($ch->parent and $chapters[$ch->parent]->number) {

            $numbers[] = $chapters[$ch->parent]->number;

        }

        if ($ch->number) {

            $numbers[] = $ch->number;

        }

    }

    if ($numbers) {

        $title = implode('.', $numbers) . '. ' . $title;

    }

    return $title;

}

/**

 * Add the book TOC sticky block to the default region.

 *

 * @param   array       $chapters   The Chapters in the book

 * @param   stdClass    $chapter    The current chapter

 * @param   stdClass    $book       The book

 * @param   stdClass    $cm         The course module

 * @param   bool|null   $edit       Whether the user is editing

 */

function book_add_fake_block($chapters, $chapter, $book, $cm, $edit = null) {

    global $PAGE, $USER;

    if ($edit === null) {

        if (has_capability('mod/book:edit', context_module::instance($cm->id))) {

            if (isset($USER->editing)) {

                $edit = $USER->editing;

            } else {

                $edit = 0;

            }

        } else {

            $edit = 0;

        }

    }

    $toc = book_get_toc($chapters, $chapter, $book, $cm, $edit);

    $bc = new block_contents();

    $bc->title = get_string('toc', 'mod_book');

    $bc->attributes['class'] = 'block block_book_toc';

    $bc->content = $toc;

    $defaultregion = $PAGE->blocks->get_default_region();

    $PAGE->blocks->add_fake_block($bc, $defaultregion);

}

/**

 * Generate toc structure

 *

 * @param array $chapters

 * @param stdClass $chapter

 * @param stdClass $book

 * @param stdClass $cm

 * @param bool $edit

 * @return string

 */

function book_get_toc($chapters, $chapter, $book, $cm, $edit) {

    global $USER, $OUTPUT;

    $toc = '';

    $nch = 0;   // Chapter number

    $ns = 0;    // Subchapter number

    $first = 1;

    $context = context_module::instance($cm->id);

    $viewhidden = has_capability('mod/book:viewhiddenchapters', $context);

    switch ($book->numbering) {

        case BOOK_NUM_NONE:

            $toc .= html_writer::start_tag('div', array('class' => 'book_toc book_toc_none clearfix'));

            break;

        case BOOK_NUM_NUMBERS:

            $toc .= html_writer::start_tag('div', array('class' => 'book_toc book_toc_numbered clearfix'));

            break;

        case BOOK_NUM_BULLETS:

            $toc .= html_writer::start_tag('div', array('class' => 'book_toc book_toc_bullets clearfix'));

            break;

        case BOOK_NUM_INDENTED:

            $toc .= html_writer::start_tag('div', array('class' => 'book_toc book_toc_indented clearfix'));

            break;

    }

    if ($edit) { // Editing on (Teacher's TOC).

        $toc .= html_writer::start_tag('ul');

        $i = 0;

        foreach ($chapters as $ch) {

            $i++;

            $title = trim(format_string($ch->title, true, array('context' => $context)));

            $titleunescaped = trim(format_string($ch->title, true, array('context' => $context, 'escape' => false)));

            $titleout = $title;

            if (!$ch->subchapter) {

                if ($first) {

                    $toc .= html_writer::start_tag('li');

                } else {

                    $toc .= html_writer::end_tag('ul');

                    $toc .= html_writer::end_tag('li');

                    $toc .= html_writer::start_tag('li');

                }

                if (!$ch->hidden) {

                    $nch++;

                    $ns = 0;

                    if ($book->numbering == BOOK_NUM_NUMBERS) {

                        $title = "$nch. $title";

                        $titleout = $title;

                    }

                } else {

                    if ($book->numbering == BOOK_NUM_NUMBERS) {

                        $title = "x. $title";

                    }

                    $titleout = html_writer::tag('span', $title, array('class' => 'dimmed_text'));

                }

            } else {

                if ($first) {

                    $toc .= html_writer::start_tag('li');

                    $toc .= html_writer::start_tag('ul');

                    $toc .= html_writer::start_tag('li');

                } else {

                    $toc .= html_writer::start_tag('li');

                }

                if (!$ch->hidden) {

                    $ns++;

                    if ($book->numbering == BOOK_NUM_NUMBERS) {

                        $title = "$nch.$ns. $title";

                        $titleout = $title;

                    }

                } else {

                    if ($book->numbering == BOOK_NUM_NUMBERS) {

                        if (empty($chapters[$ch->parent]->hidden)) {

                            $title = "$nch.x. $title";

                        } else {

                            $title = "x.x. $title";

                        }

                    }

                    $titleout = html_writer::tag('span', $title, array('class' => 'dimmed_text'));

                }

            }

            $toc .= html_writer::start_tag('div', array('class' => 'd-flex'));

            if ($ch->id == $chapter->id) {

                $toc .= html_writer::tag('strong', $titleout, array('class' => 'text-truncate'));

            } else {

                $toc .= html_writer::link(new moodle_url('view.php', array('id' => $cm->id, 'chapterid' => $ch->id)), $titleout,

                    array('title' => $titleunescaped, 'class' => 'text-truncate'));

            }

            $toc .= html_writer::start_tag('div', array('class' => 'action-list d-flex ml-auto'));

            if ($i != 1) {

                $toc .= html_writer::link(new moodle_url('move.php', array('id' => $cm->id, 'chapterid' => $ch->id, 'up' => '1', 'sesskey' => $USER->sesskey)),

                        $OUTPUT->pix_icon('t/up', get_string('movechapterup', 'mod_book', $title)),

                        array('title' => get_string('movechapterup', 'mod_book', $titleunescaped)));

            }

            if ($i != count($chapters)) {

                $toc .= html_writer::link(new moodle_url('move.php', array('id' => $cm->id, 'chapterid' => $ch->id, 'up' => '0', 'sesskey' => $USER->sesskey)),

                        $OUTPUT->pix_icon('t/down', get_string('movechapterdown', 'mod_book', $title)),

                        array('title' => get_string('movechapterdown', 'mod_book', $titleunescaped)));

            }

            $toc .= html_writer::link(new moodle_url('edit.php', array('cmid' => $cm->id, 'id' => $ch->id)),

                    $OUTPUT->pix_icon('t/edit', get_string('editchapter', 'mod_book', $title)),

                    array('title' => get_string('editchapter', 'mod_book', $titleunescaped)));

            $deleteaction = new confirm_action(get_string('deletechapter', 'mod_book', $titleunescaped));

            $toc .= $OUTPUT->action_icon(

                    new moodle_url('delete.php', [

                            'id'        => $cm->id,

                            'chapterid' => $ch->id,

                            'sesskey'   => sesskey(),

                            'confirm'   => 1,

                        ]),

                    new pix_icon('t/delete', get_string('deletechapter', 'mod_book', $title)),

                    $deleteaction,

                    ['title' => get_string('deletechapter', 'mod_book', $titleunescaped)]

                );

            if ($ch->hidden) {

                $toc .= html_writer::link(new moodle_url('show.php', array('id' => $cm->id, 'chapterid' => $ch->id, 'sesskey' => $USER->sesskey)),

                        $OUTPUT->pix_icon('t/show', get_string('showchapter', 'mod_book', $title)),

                        array('title' => get_string('showchapter', 'mod_book', $titleunescaped)));

            } else {

                $toc .= html_writer::link(new moodle_url('show.php', array('id' => $cm->id, 'chapterid' => $ch->id, 'sesskey' => $USER->sesskey)),

                        $OUTPUT->pix_icon('t/hide', get_string('hidechapter', 'mod_book', $title)),

                        array('title' => get_string('hidechapter', 'mod_book', $titleunescaped)));

            }

            $buttontitle = get_string('addafterchapter', 'mod_book', ['title' => $ch->title]);

            $toc .= html_writer::link(new moodle_url('edit.php', array('cmid' => $cm->id, 'pagenum' => $ch->pagenum, 'subchapter' => $ch->subchapter)),

                                            $OUTPUT->pix_icon('add', $buttontitle, 'mod_book'), array('title' => $buttontitle));

            $toc .= html_writer::end_tag('div');

            $toc .= html_writer::end_tag('div');

            if (!$ch->subchapter) {

                $toc .= html_writer::start_tag('ul');

            } else {

                $toc .= html_writer::end_tag('li');

            }

            $first = 0;

        }

        $toc .= html_writer::end_tag('ul');

        $toc .= html_writer::end_tag('li');

        $toc .= html_writer::end_tag('ul');

    } else { // Editing off. Normal students, teachers view.

        $toc .= html_writer::start_tag('ul');

        foreach ($chapters as $ch) {

            $title = trim(format_string($ch->title, true, array('context'=>$context)));

            $titleunescaped = trim(format_string($ch->title, true, array('context' => $context, 'escape' => false)));

            if (!$ch->hidden || ($ch->hidden && $viewhidden)) {

                if (!$ch->subchapter) {

                    $nch++;

                    $ns = 0;

                    if ($first) {

                        $toc .= html_writer::start_tag('li');

                    } else {

                        $toc .= html_writer::end_tag('ul');

                        $toc .= html_writer::end_tag('li');

                        $toc .= html_writer::start_tag('li');

                    }

                    if ($book->numbering == BOOK_NUM_NUMBERS) {

                          $title = "$nch. $title";

                    }

                } else {

                    $ns++;

                    if ($first) {

                        $toc .= html_writer::start_tag('li');

                        $toc .= html_writer::start_tag('ul');

                        $toc .= html_writer::start_tag('li');

                    } else {

                        $toc .= html_writer::start_tag('li');

                    }

                    if ($book->numbering == BOOK_NUM_NUMBERS) {

                          $title = "$nch.$ns. $title";

                    }

                }

                $cssclass = ($ch->hidden && $viewhidden) ? 'dimmed_text' : '';

                if ($ch->id == $chapter->id) {

                    $toc .= html_writer::tag('strong', $title, array('class' => $cssclass));

                } else {

                    $toc .= html_writer::link(new moodle_url('view.php',

                                              array('id' => $cm->id, 'chapterid' => $ch->id)),

                                              $title, array('title' => s($titleunescaped), 'class' => $cssclass));

                }

                if (!$ch->subchapter) {

                    $toc .= html_writer::start_tag('ul');

                } else {

                    $toc .= html_writer::end_tag('li');

                }

                $first = 0;

            }

        }

        $toc .= html_writer::end_tag('ul');

        $toc .= html_writer::end_tag('li');

        $toc .= html_writer::end_tag('ul');

    }

    $toc .= html_writer::end_tag('div');

    $toc = str_replace('<ul></ul>', '', $toc); // Cleanup of invalid structures.

    return $toc;

}

/**

 * Returns book chapters tagged with a specified tag.

 *

 * This is a callback used by the tag area mod_book/book_chapters to search for book chapters

 * tagged with a specific tag.

 *

 * @param core_tag_tag $tag

 * @param bool $exclusivemode if set to true it means that no other entities tagged with this tag

 *             are displayed on the page and the per-page limit may be bigger

 * @param int $fromctx context id where the link was displayed, may be used by callbacks

 *            to display items in the same context first

 * @param int $ctx context id where to search for records

 * @param bool $rec search in subcontexts as well

 * @param int $page 0-based number of page being displayed

 * @return \core_tag\output\tagindex

 */

function mod_book_get_tagged_chapters($tag, $exclusivemode = false, $fromctx = 0, $ctx = 0, $rec = true, $page = 0) {

    global $OUTPUT;

    $perpage = $exclusivemode ? 20 : 5;

    // Build the SQL query.

    $ctxselect = context_helper::get_preload_record_columns_sql('ctx');

    $query = "SELECT bc.id, bc.title, bc.bookid, bc.hidden,

                    cm.id AS cmid, c.id AS courseid, c.shortname, c.fullname, $ctxselect

                FROM {book_chapters} bc

                JOIN {book} b ON b.id = bc.bookid

                JOIN {modules} m ON m.name='book'

                JOIN {course_modules} cm ON cm.module = m.id AND cm.instance = b.id

                JOIN {tag_instance} tt ON bc.id = tt.itemid

                JOIN {course} c ON cm.course = c.id

                JOIN {context} ctx ON ctx.instanceid = cm.id AND ctx.contextlevel = :coursemodulecontextlevel

               WHERE tt.itemtype = :itemtype AND tt.tagid = :tagid AND tt.component = :component

                 AND cm.deletioninprogress = 0

                 AND bc.id %ITEMFILTER% AND c.id %COURSEFILTER%";

    $params = array('itemtype' => 'book_chapters', 'tagid' => $tag->id, 'component' => 'mod_book',

                    'coursemodulecontextlevel' => CONTEXT_MODULE);

    if ($ctx) {

        $context = $ctx ? context::instance_by_id($ctx) : context_system::instance();

        $query .= $rec ? ' AND (ctx.id = :contextid OR ctx.path LIKE :path)' : ' AND ctx.id = :contextid';

        $params['contextid'] = $context->id;

        $params['path'] = $context->path.'/%';

    }

    $query .= " ORDER BY ";

    if ($fromctx) {

        // In order-clause specify that modules from inside "fromctx" context should be returned first.

        $fromcontext = context::instance_by_id($fromctx);

        $query .= ' (CASE WHEN ctx.id = :fromcontextid OR ctx.path LIKE :frompath THEN 0 ELSE 1 END),';

        $params['fromcontextid'] = $fromcontext->id;

        $params['frompath'] = $fromcontext->path.'/%';

    }

    $query .= ' c.sortorder, cm.id, bc.id';

    $totalpages = $page + 1;

    // Use core_tag_index_builder to build and filter the list of items.

    $builder = new core_tag_index_builder('mod_book', 'book_chapters', $query, $params, $page * $perpage, $perpage + 1);

    while ($item = $builder->has_item_that_needs_access_check()) {

        context_helper::preload_from_record($item);

        $courseid = $item->courseid;

        if (!$builder->can_access_course($courseid)) {

            $builder->set_accessible($item, false);

            continue;

        }

        $modinfo = get_fast_modinfo($builder->get_course($courseid));

        // Set accessibility of this item and all other items in the same course.

        $builder->walk(function ($taggeditem) use ($courseid, $modinfo, $builder) {

            if ($taggeditem->courseid == $courseid) {

                $accessible = false;

                if (($cm = $modinfo->get_cm($taggeditem->cmid)) && $cm->uservisible) {

                    if (empty($taggeditem->hidden)) {

                        $accessible = true;

                    } else {

                        $accessible = has_capability('mod/book:viewhiddenchapters', context_module::instance($cm->id));

                    }

                }

                $builder->set_accessible($taggeditem, $accessible);

            }

        });

    }

    $items = $builder->get_items();

    if (count($items) > $perpage) {

        $totalpages = $page + 2; // We don't need exact page count, just indicate that the next page exists.

        array_pop($items);

    }

    // Build the display contents.

    if ($items) {

        $tagfeed = new core_tag\output\tagfeed();

        foreach ($items as $item) {

            context_helper::preload_from_record($item);

            $modinfo = get_fast_modinfo($item->courseid);

            $cm = $modinfo->get_cm($item->cmid);

            $pageurl = new moodle_url('/mod/book/view.php', array('chapterid' => $item->id, 'b' => $item->bookid));

            $pagename = format_string($item->title, true, array('context' => context_module::instance($item->cmid)));

            $pagename = html_writer::link($pageurl, $pagename);

            $courseurl = course_get_url($item->courseid, $cm->sectionnum);

            $cmname = html_writer::link($cm->url, $cm->get_formatted_name());

            $coursename = format_string($item->fullname, true, array('context' => context_course::instance($item->courseid)));

            $coursename = html_writer::link($courseurl, $coursename);

            $icon = html_writer::link($pageurl, html_writer::empty_tag('img', array('src' => $cm->get_icon_url())));

            $tagfeed->add($icon, $pagename, $cmname.'<br>'.$coursename);

        }

        $content = $OUTPUT->render_from_template('core_tag/tagfeed',

            $tagfeed->export_for_template($OUTPUT));

        return new core_tag\output\tagindex($tag, 'mod_book', 'book_chapters', $content,

            $exclusivemode, $fromctx, $ctx, $rec, $page, $totalpages);

    }

}

/**

 * File browsing support class

 *

 * @copyright  2010-2011 Petr Skoda {@link http://skodak.org}

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

 */

class book_file_info extends file_info {

    /** @var stdClass Course object */

    protected $course;

    /** @var stdClass Course module object */

    protected $cm;

    /** @var array Available file areas */

    protected $areas;

    /** @var string File area to browse */

    protected $filearea;

    /**

     * Constructor

     *

     * @param file_browser $browser file_browser instance

     * @param stdClass $course course object

     * @param stdClass $cm course module object

     * @param stdClass $context module context

     * @param array $areas available file areas

     * @param string $filearea file area to browse

     */

    public function __construct($browser, $course, $cm, $context, $areas, $filearea) {

        parent::__construct($browser, $context);

        $this->course   = $course;

        $this->cm       = $cm;

        $this->areas    = $areas;

        $this->filearea = $filearea;

    }

    /**

     * Returns list of standard virtual file/directory identification.

     * The difference from stored_file parameters is that null values

     * are allowed in all fields

     * @return array with keys contextid, filearea, itemid, filepath and filename

     */

    public function get_params() {

        return array('contextid'=>$this->context->id,

                     'component'=>'mod_book',

                     'filearea' =>$this->filearea,

                     'itemid'   =>null,

                     'filepath' =>null,

                     'filename' =>null);

    }

    /**

     * Returns localised visible name.

     * @return string

     */

    public function get_visible_name() {

        return $this->areas[$this->filearea];

    }

    /**

     * Can I add new files or directories?

     * @return bool

     */

    public function is_writable() {

        return false;

    }

    /**

     * Is directory?

     * @return bool

     */

    public function is_directory() {

        return true;

    }

    /**

     * Returns list of children.

     * @return array of file_info instances

     */

    public function get_children() {

        return $this->get_filtered_children('*', false, true);

    }

    /**

     * Help function to return files matching extensions or their count

     *

     * @param string|array $extensions, either '*' or array of lowercase extensions, i.e. array('.gif','.jpg')

     * @param bool|int $countonly if false returns the children, if an int returns just the

     *    count of children but stops counting when $countonly number of children is reached

     * @param bool $returnemptyfolders if true returns items that don't have matching files inside

     * @return array|int array of file_info instances or the count

     */

    private function get_filtered_children($extensions = '*', $countonly = false, $returnemptyfolders = false) {

        global $DB;

        $params = array('contextid' => $this->context->id,

            'component' => 'mod_book',

            'filearea' => $this->filearea,

            'bookid' => $this->cm->instance);

        $sql = 'SELECT DISTINCT bc.id, bc.pagenum

                    FROM {files} f, {book_chapters} bc

                    WHERE f.contextid = :contextid

                    AND f.component = :component

                    AND f.filearea = :filearea

                    AND bc.bookid = :bookid

                    AND bc.id = f.itemid';

        if (!$returnemptyfolders) {

            $sql .= ' AND filename <> :emptyfilename';

            $params['emptyfilename'] = '.';

        }

        list($sql2, $params2) = $this->build_search_files_sql($extensions, 'f');

        $sql .= ' '.$sql2;

        $params = array_merge($params, $params2);

        if ($countonly === false) {

            $sql .= ' ORDER BY bc.pagenum';

        }

        $rs = $DB->get_recordset_sql($sql, $params);

        $children = array();

        foreach ($rs as $record) {

            if ($child = $this->browser->get_file_info($this->context, 'mod_book', $this->filearea, $record->id)) {

                if ($returnemptyfolders || $child->count_non_empty_children($extensions)) {

                    $children[] = $child;

                }

            }

            if ($countonly !== false && count($children) >= $countonly) {

                break;

            }

        }

        $rs->close();

        if ($countonly !== false) {

            return count($children);

        }

        return $children;

    }

    /**

     * Returns list of children which are either files matching the specified extensions

     * or folders that contain at least one such file.

     *

     * @param string|array $extensions, either '*' or array of lowercase extensions, i.e. array('.gif','.jpg')

     * @return array of file_info instances

     */

    public function get_non_empty_children($extensions = '*') {

        return $this->get_filtered_children($extensions, false);

    }

    /**

     * Returns the number of children which are either files matching the specified extensions

     * or folders containing at least one such file.

     *

     * @param string|array $extensions, for example '*' or array('.gif','.jpg')

     * @param int $limit stop counting after at least $limit non-empty children are found

     * @return int

     */

    public function count_non_empty_children($extensions = '*', $limit = 1) {

        return $this->get_filtered_children($extensions, $limit);

    }

    /**

     * Returns parent file_info instance

     * @return file_info or null for root

     */

    public function get_parent() {

        return $this->browser->get_file_info($this->context);

    }

}