helper.php

<?php

/**
 * @license    GPL 2 (http://www.gnu.org/licenses/gpl.html)
 * @author     Esther Brunner <wikidesign@gmail.com>
 * @author     Christopher Smith <chris@jalakai.co.uk>
 * @author     Gina Häußge, Michael Klier <dokuwiki@chimeric.de>
 * @author     Michael Hamann <michael@content-space.de>
 */

use dokuwiki\Extension\Plugin;
use dokuwiki\plugin\include\GenericResolver;
use dokuwiki\File\PageResolver;

/**
 * Helper functions for the include plugin and other plugins that want to include pages.
 */
class helper_plugin_include extends Plugin
{
    // DokuWiki_Helper_Plugin

    public $defaults = [];
    public $sec_close = true;
    /** @var helper_plugin_tag $taghelper */
    public $taghelper;
    public $includes = []; // deprecated - compatibility code for the blog plugin

    /**
     * Constructor loads default config settings once
     */
    public function __construct()
    {
        $this->defaults['noheader'] = $this->getConf('noheader');
        $this->defaults['firstsec'] = $this->getConf('firstseconly');
        $this->defaults['editbtn'] = $this->getConf('showeditbtn');
        $this->defaults['taglogos'] = $this->getConf('showtaglogos');
        $this->defaults['footer'] = $this->getConf('showfooter');
        $this->defaults['redirect'] = $this->getConf('doredirect');
        $this->defaults['date'] = $this->getConf('showdate');
        $this->defaults['mdate'] = $this->getConf('showmdate');
        $this->defaults['user'] = $this->getConf('showuser');
        $this->defaults['comments'] = $this->getConf('showcomments');
        $this->defaults['linkbacks'] = $this->getConf('showlinkbacks');
        $this->defaults['tags'] = $this->getConf('showtags');
        $this->defaults['link'] = $this->getConf('showlink');
        $this->defaults['permalink'] = $this->getConf('showpermalink');
        $this->defaults['indent'] = $this->getConf('doindent');
        $this->defaults['linkonly'] = $this->getConf('linkonly');
        $this->defaults['title'] = $this->getConf('title');
        $this->defaults['pageexists'] = $this->getConf('pageexists');
        $this->defaults['parlink'] = $this->getConf('parlink');
        $this->defaults['inline'] = false;
        $this->defaults['order'] = $this->getConf('order');
        $this->defaults['rsort'] = $this->getConf('rsort');
        $this->defaults['depth'] = $this->getConf('depth');
        $this->defaults['readmore'] = $this->getConf('readmore');
    }

    /**
     * Available methods for other plugins
     */
    public function getMethods()
    {
        return [
            [
                'name' => 'getFlags',
                'desc' => 'overrides standard values for showfooter and firstseconly settings',
                'params' => ['flags' => 'array']
            ]
        ];
    }

    /**
     * Magic method to handle deprecated method calls
     *
     * @param string $func The name of the method being called
     * @param array $args The arguments passed to the method
     * @return mixed
     */
    public function __call($func, $args)
    {
        switch ($func) {
            case 'get_flags':
                dbg_deprecated('getFlags()');
                return $this->getFlags($args[0]);
            case '_get_instructions':
                dbg_deprecated('getInstructions()');
                return $this->getInstructions(
                    $args[0], // page
                    $args[1], // sect
                    $args[2], // mode
                    $args[3], // lvl
                    $args[4], // flags
                    $args[5] ?? null, // root_id
                    $args[6] ?? [] // included_pages
                );
            case '_get_included_pages':
                dbg_deprecated('getIncludedPages()');
                return $this->getIncludedPages(
                    $args[0], // mode
                    $args[1], // page
                    $args[2], // sect
                    $args[3], // parent_id
                    $args[4]  // flags
                );
            default:
                throw new \BadMethodCallException("Method $func does not exist in " . __CLASS__);
        }
    }

    /**
     * Overrides standard values for showfooter and firstseconly settings
     */
    public function getFlags($setflags)
    {
        global $INPUT;

        // load defaults
        $flags = $this->defaults;
        foreach ($setflags as $flag) {
            $value = '';
            if (strpos($flag, '=') !== false) {
                [$flag, $value] = explode('=', $flag, 2);
            }
            switch ($flag) {
                case 'footer':
                    $flags['footer'] = 1;
                    break;
                case 'nofooter':
                    $flags['footer'] = 0;
                    break;
                case 'firstseconly':
                case 'firstsectiononly':
                    $flags['firstsec'] = 1;
                    break;
                case 'fullpage':
                    $flags['firstsec'] = 0;
                    break;
                case 'showheader':
                case 'header':
                    $flags['noheader'] = 0;
                    break;
                case 'noheader':
                    $flags['noheader'] = 1;
                    break;
                case 'editbtn':
                case 'editbutton':
                    $flags['editbtn'] = 1;
                    break;
                case 'noeditbtn':
                case 'noeditbutton':
                    $flags['editbtn'] = 0;
                    break;
                case 'permalink':
                    $flags['permalink'] = 1;
                    break;
                case 'nopermalink':
                    $flags['permalink'] = 0;
                    break;
                case 'redirect':
                    $flags['redirect'] = 1;
                    break;
                case 'noredirect':
                    $flags['redirect'] = 0;
                    break;
                case 'link':
                    $flags['link'] = 1;
                    break;
                case 'nolink':
                    $flags['link'] = 0;
                    break;
                case 'user':
                    $flags['user'] = 1;
                    break;
                case 'nouser':
                    $flags['user'] = 0;
                    break;
                case 'comments':
                    $flags['comments'] = 1;
                    break;
                case 'nocomments':
                    $flags['comments'] = 0;
                    break;
                case 'linkbacks':
                    $flags['linkbacks'] = 1;
                    break;
                case 'nolinkbacks':
                    $flags['linkbacks'] = 0;
                    break;
                case 'tags':
                    $flags['tags'] = 1;
                    break;
                case 'notags':
                    $flags['tags'] = 0;
                    break;
                case 'date':
                    $flags['date'] = 1;
                    break;
                case 'nodate':
                    $flags['date'] = 0;
                    break;
                case 'mdate':
                    $flags['mdate'] = 1;
                    break;
                case 'nomdate':
                    $flags['mdate'] = 0;
                    break;
                case 'indent':
                    $flags['indent'] = 1;
                    break;
                case 'noindent':
                    $flags['indent'] = 0;
                    break;
                case 'linkonly':
                    $flags['linkonly'] = 1;
                    break;
                case 'nolinkonly':
                case 'include_content':
                    $flags['linkonly'] = 0;
                    break;
                case 'inline':
                    $flags['inline'] = 1;
                    break;
                case 'title':
                    $flags['title'] = 1;
                    break;
                case 'notitle':
                    $flags['title'] = 0;
                    break;
                case 'pageexists':
                    $flags['pageexists'] = 1;
                    break;
                case 'nopageexists':
                    $flags['pageexists'] = 0;
                    break;
                case 'existlink':
                    $flags['pageexists'] = 1;
                    $flags['linkonly'] = 1;
                    break;
                case 'parlink':
                    $flags['parlink'] = 1;
                    break;
                case 'noparlink':
                    $flags['parlink'] = 0;
                    break;
                case 'order':
                    $flags['order'] = $value;
                    break;
                case 'sort':
                    $flags['rsort'] = 0;
                    break;
                case 'rsort':
                    $flags['rsort'] = 1;
                    break;
                case 'depth':
                    $flags['depth'] = max(intval($value), 0);
                    break;
                case 'beforeeach':
                    $flags['beforeeach'] = $value;
                    break;
                case 'aftereach':
                    $flags['aftereach'] = $value;
                    break;
                case 'readmore':
                    $flags['readmore'] = 1;
                    break;
                case 'noreadmore':
                    $flags['readmore'] = 0;
                    break;
                case 'exclude':
                    $flags['exclude'] = $value;
                    break;
            }
        }
        // the include_content URL parameter overrides flags
        if ($INPUT->has('include_content')) {
            $flags['linkonly'] = 0;
        }
        return $flags;
    }

    /**
     * Returns the converted instructions of a give page/section
     */
    public function getInstructions($page, $sect, $mode, $lvl, $flags, $root_id = null, $included_pages = [])
    {
        $key = ($sect) ? $page . '#' . $sect : $page;
        $this->includes[$key] = true; // legacy code for keeping compatibility with other plugins

        // keep compatibility with other plugins that don't know the $root_id parameter
        if (is_null($root_id)) {
            global $ID;
            $root_id = $ID;
        }

        if ($flags['linkonly']) {
            if (page_exists($page) || $flags['pageexists'] == 0) {
                $title = '';
                if ($flags['title'])
                    $title = p_get_first_heading($page);
                if ($flags['parlink']) {
                    $ins = [['p_open', []], ['internallink', [':' . $key, $title]], ['p_close', []]];
                } else {
                    $ins = [['internallink', [':' . $key, $title]]];
                }
            } else {
                $ins = [];
            }
        } else {
            if (page_exists($page)) {
                global $ID;
                // Change the global $ID as otherwise plugins like the discussion plugin will save data for wrong page
                $backupID = $ID;
                $ID = $page;
                $ins = p_cached_instructions(wikiFN($page), false, $page);
                $ID = $backupID;
            } else {
                $ins = [];
            }

            $this->convertInstructions($ins, $lvl, $page, $sect, $flags, $root_id, $included_pages);
        }
        return $ins;
    }

    /**
     * Converts instructions of the included page
     *
     * The function iterates over the given list of instructions and generates
     * an index of header and section indicies. It also removes document
     * start/end instructions, converts links, and removes unwanted
     * instructions like tags, comments, linkbacks.
     *
     * Later all header/section levels are converted to match the current
     * inclusion level.
     *
     * @author Michael Klier <chi@chimeric.de>
     */
    protected function convertInstructions(&$ins, $lvl, $page, $sect, $flags, $root_id, $included_pages = [])
    {
        global $conf;

        // filter instructions if needed
        if (!empty($sect)) {
            $this->getSection($ins, $sect);   // section required
        }

        if ($flags['firstsec']) {
            $this->getFirstSection($ins, $page, $flags);  // only first section
        }

        $num = count($ins);

        $conv_idx = []; // conversion index
        $lvl_max = false;   // max level
        $first_header = -1;
        $no_header = false;
        $sect_title = false;
        $endpos = null; // end position of the raw wiki text

        $this->adaptLinks($ins, $page, $included_pages);

        for ($i = 0; $i < $num; $i++) {
            switch ($ins[$i][0]) {
                case 'document_start':
                case 'document_end':
                case 'section_edit':
                    unset($ins[$i]);
                    break;
                case 'header':
                    // get section title of first section
                    if ($sect && !$sect_title) {
                        $sect_title = $ins[$i][1][0];
                    }
                    // check if we need to skip the first header
                    if ((!$no_header) && $flags['noheader']) {
                        $no_header = true;
                    }

                    $conv_idx[] = $i;
                    // get index of first header
                    if ($first_header == -1) $first_header = $i;
                    // get max level of this instructions set
                    if (!$lvl_max || ($ins[$i][1][1] < $lvl_max)) {
                        $lvl_max = $ins[$i][1][1];
                    }
                    break;
                case 'section_open':
                    if ($flags['inline'])
                        unset($ins[$i]);
                    else $conv_idx[] = $i;
                    break;
                case 'section_close':
                    if ($flags['inline'])
                        unset($ins[$i]);
                    break;
                case 'nest':
                    $this->adaptLinks($ins[$i][1][0], $page, $included_pages);
                    break;
                case 'plugin':
                    // FIXME skip other plugins?
                    switch ($ins[$i][1][0]) {
                        case 'tag_tag':                 // skip tags
                        case 'discussion_comments':     // skip comments
                        case 'linkback':                // skip linkbacks
                        case 'data_entry':              // skip data plugin
                        case 'meta':                    // skip meta plugin
                        case 'indexmenu_tag':           // skip indexmenu sort tag
                        case 'include_sorttag':         // skip include plugin sort tag
                            unset($ins[$i]);
                            break;
                        // adapt indentation level of nested includes
                        case 'include_include':
                            if (!$flags['inline'] && $flags['indent'])
                                $ins[$i][1][1][4] += $lvl;
                            break;
                        /*
                         * if there is already a closelastsecedit instruction (was added by one of the section
                         * functions), store its position but delete it as it can't be determined yet if it is needed,
                         * i.e. if there is a header which generates a section edit (depends on the levels, level
                         * adjustments, $no_header, ...)
                         */
                        case 'include_closelastsecedit':
                            $endpos = $ins[$i][1][1][0];
                            unset($ins[$i]);
                            break;
                    }
                    break;
                default:
                    break;
            }
        }

        // calculate difference between header/section level and include level
        $diff = 0;
        if (!isset($lvl_max)) $lvl_max = 0; // if no level found in target, set to 0
        $diff = $lvl - $lvl_max + 1;
        if ($no_header) $diff -= 1;  // push up one level if "noheader"

        // convert headers and set footer/permalink
        $hdr_deleted = false;
        $has_permalink = false;
        $footer_lvl = false;
        $contains_secedit = false;
        $section_close_at = false;
        foreach ($conv_idx as $idx) {
            if ($ins[$idx][0] == 'header') {
                if ($section_close_at === false && isset($ins[$idx + 1]) && $ins[$idx + 1][0] == 'section_open') {
                    // store the index of the first heading that is followed by a new section
                    // the wrap plugin creates sections without section_open so the section
                    // shouldn't be closed before them
                    $section_close_at = $idx;
                }

                if ($no_header && !$hdr_deleted) {
                    unset($ins[$idx]);
                    $hdr_deleted = true;
                    continue;
                }

                if ($flags['indent']) {
                    $lvl_new = (($ins[$idx][1][1] + $diff) > 5) ? 5 : ($ins[$idx][1][1] + $diff);
                    $ins[$idx][1][1] = $lvl_new;
                }

                if ($ins[$idx][1][1] <= $conf['maxseclevel'])
                    $contains_secedit = true;

                // set permalink
                if ($flags['link'] && !$has_permalink && ($idx == $first_header)) {
                    $ins[$idx] = $this->permalinkHeaderInstruction($ins[$idx], $page, $sect, $flags);
                    $has_permalink = true;
                }

                // set footer level
                if (!$footer_lvl && ($idx == $first_header) && !$no_header) {
                    if ($flags['indent'] && isset($lvl_new)) {
                        $footer_lvl = $lvl_new;
                    } else {
                        $footer_lvl = $lvl_max;
                    }
                }
            } else {
                // it's a section
                if ($flags['indent']) {
                    $lvl_new = (($ins[$idx][1][0] + $diff) > 5) ? 5 : ($ins[$idx][1][0] + $diff);
                    $ins[$idx][1][0] = $lvl_new;
                }

                // check if noheader is used and set the footer level to the first section
                if ($no_header && !$footer_lvl) {
                    if ($flags['indent'] && isset($lvl_new)) {
                        $footer_lvl = $lvl_new;
                    } else {
                        $footer_lvl = $lvl_max;
                    }
                }
            }
        }

        // close last open section of the included page if there is any
        if ($contains_secedit) {
            $ins[] = ['plugin', ['include_closelastsecedit', [$endpos]]];
        }

        $include_secid = ($flags['include_secid'] ?? null);

        // add edit button
        if ($flags['editbtn']) {
            $ins[] = $this->editButtonInstruction(
                $page,
                $sect,
                $sect_title,
                ($flags['redirect'] ? $root_id : false),
                $include_secid
            );
        }

        // add footer
        if ($flags['footer']) {
            $ins[] = $this->footerInstruction($page, $sect, $sect_title, $flags, $footer_lvl, $root_id);
        }

        // wrap content at the beginning of the include that is not in a section in a section
        if ($lvl > 0 && $section_close_at !== 0 && $flags['indent'] && !$flags['inline']) {
            if ($section_close_at === false) {
                $ins[] = ['section_close', []];
                array_unshift($ins, ['section_open', [$lvl]]);
            } else {
                $section_close_idx = array_search($section_close_at, array_keys($ins));
                if ($section_close_idx > 0) {
                    $before_ins = array_slice($ins, 0, $section_close_idx);
                    $after_ins = array_slice($ins, $section_close_idx);
                    $ins = array_merge($before_ins, [['section_close', []]], $after_ins);
                    array_unshift($ins, ['section_open', [$lvl]]);
                }
            }
        }

        // add instructions entry wrapper
        array_unshift($ins, ['plugin', ['include_wrap', ['open', $page, $flags['redirect'], $include_secid]]]);
        if (isset($flags['beforeeach']))
            array_unshift($ins, ['entity', [$flags['beforeeach']]]);
        $ins[] = ['plugin', ['include_wrap', ['close']]];
        if (isset($flags['aftereach']))
            $ins[] = ['entity', [$flags['aftereach']]];

        // close previous section if any and re-open after inclusion
        if ($lvl != 0 && $this->sec_close && !$flags['inline']) {
            array_unshift($ins, ['section_close', []]);
            $ins[] = ['section_open', [$lvl]];
        }
    }

    /**
     * Returns instruction item for the include plugin footer
     */
    protected function footerInstruction($page, $sect, $sect_title, $flags, $footer_lvl, $root_id)
    {
        return [
            0 => 'plugin',
            1 => [
                'include_footer',
                [
                    $page,
                    $sect,
                    $sect_title,
                    $flags,
                    $root_id,
                    $footer_lvl
                ]
            ]
        ];
    }

    /**
     * Returns instruction item for an edit button
     *
     * @author Michael Klier <chi@chimeric.de>
     */
    public function editButtonInstruction($page, $sect, $sect_title, $root_id, $hid = '')
    {
        $title = ($sect) ? $sect_title : $page;
        $editbtn = [];
        $editbtn[0] = 'plugin';
        $editbtn[1] = ['include_editbtn', [$title, $hid]];
        return $editbtn;
    }

    /**
     * Convert the given header into instruction item for a permalink header
     *
     * @author Michael Klier <chi@chimeric.de>
     */
    public function permalinkHeaderInstruction($originalHeader, $page, $sect, $flags)
    {
        return [
            0 => 'plugin',
            1 => [
                'include_header',
                [
                    $originalHeader[1][0],
                    $originalHeader[1][1],
                    $originalHeader[1][2],
                    $page,
                    $sect,
                    $flags
                ]
            ]
        ];
    }

    /**
     * Convert internal and local links depending on the included pages
     *
     * @param array $ins The instructions that shall be adapted
     * @param string $page The included page
     * @param array $included_pages The array of pages that are included
     */
    private function adaptLinks(&$ins, $page, $included_pages = null)
    {
        $num = count($ins);

        for ($i = 0; $i < $num; $i++) {
            // adjust links with image titles
            if (
                strpos($ins[$i][0], 'link') !== false &&
                isset($ins[$i][1][1]) &&
                is_array($ins[$i][1][1]) &&
                $ins[$i][1][1]['type'] == 'internalmedia'
            ) {
                // resolve relative ids, but without cleaning in order to preserve the name
                $media_id = (new GenericResolver($page))->resolveId($ins[$i][1][1]['src']);
                // make sure that after resolving the link again it will be the same link
                if ($media_id[0] != ':') $media_id = ':' . $media_id;
                $ins[$i][1][1]['src'] = $media_id;
            }

            switch ($ins[$i][0]) {
                case 'internallink':
                case 'internalmedia':
                    // make sure parameters aren't touched
                    $link_params = '';
                    $link_id = $ins[$i][1][0];
                    $link_parts = explode('?', $link_id, 2);
                    if (count($link_parts) === 2) {
                        $link_id = $link_parts[0];
                        $link_params = $link_parts[1];
                    }
                    // resolve the id without cleaning it
                    $link_id = (new GenericResolver($page))->resolveId($link_id);
                    // this id is internal (i.e. absolute) now, add ':' to make resolve_id work again
                    if ($link_id[0] != ':') $link_id = ':' . $link_id;
                    // restore parameters
                    $ins[$i][1][0] = ($link_params != '') ? $link_id . '?' . $link_params : $link_id;

                    if ($ins[$i][0] == 'internallink' && !empty($included_pages)) {
                        // change links to included pages into local links
                        // only adapt links without parameters
                        $link_id = $ins[$i][1][0];
                        $link_parts = explode('?', $link_id, 2);
                        if (count($link_parts) === 1) {
                            $link_id = (new PageResolver($page))->resolveId($link_id);

                            $link_parts = explode('#', $link_id, 2);
                            $hash = '';
                            if (count($link_parts) === 2) {
                                [$link_id, $hash] = $link_parts;
                            }
                            if (array_key_exists($link_id, $included_pages)) {
                                if ($hash) {
                                    // hopefully the hash is also unique in the including page
                                    // (otherwise this might be the wrong link target)
                                    $ins[$i][0] = 'locallink';
                                    $ins[$i][1][0] = $hash;
                                } else {
                                    // the include section ids are different from normal section ids
                                    // (so they won't conflict) but this
                                    // also means that the normal locallink function can't be used
                                    $ins[$i][0] = 'plugin';
                                    $ins[$i][1] = [
                                        'include_locallink',
                                        [
                                            $included_pages[$link_id]['hid'],
                                            $ins[$i][1][1],
                                            $ins[$i][1][0]
                                        ]
                                    ];
                                }
                            }
                        }
                    }
                    break;
                case 'locallink':
                    /* Convert local links to internal links if the page hasn't been fully included */
                    if ($included_pages == null || !array_key_exists($page, $included_pages)) {
                        $ins[$i][0] = 'internallink';
                        $ins[$i][1][0] = ':' . $page . '#' . $ins[$i][1][0];
                    }
                    break;
            }
        }
    }

    /**
     * Get a section including its subsections
     */
    protected function getSection(&$ins, $sect)
    {
        $num = count($ins);
        $offset = false;
        $lvl = false;
        $end = false;
        $endpos = null; // end position in the input text, needed for section edit buttons

        $check = []; // used for sectionID() in order to get the same ids as the xhtml renderer

        for ($i = 0; $i < $num; $i++) {
            if ($ins[$i][0] == 'header') {
                // found the right header
                if (sectionID($ins[$i][1][0], $check) == $sect) {
                    $offset = $i;
                    $lvl = $ins[$i][1][1];
                } elseif ($offset && $lvl && ($ins[$i][1][1] <= $lvl)) {
                    $end = $i - $offset;
                    // the position directly after the found section, needed for the section edit button:
                    $endpos = $ins[$i][1][2];
                    break;
                }
            }
        }
        $offset = $offset ?: 0;
        $end = $end ?: $num - 1;
        if (is_array($ins)) {
            $ins = array_slice($ins, $offset, $end);
            // store the end position in the include_closelastsecedit instruction so it can generate a matching button
            $ins[] = ['plugin', ['include_closelastsecedit', [$endpos]]];
        }
    }

    /**
     * Only display the first section of a page and a readmore link
     *
     * @author Michael Klier <chi@chimeric.de>
     */
    protected function getFirstSection(&$ins, $page, $flags)
    {
        $num = count($ins);
        $first_sect = false;
        $endpos = null; // end position in the input text
        for ($i = 0; $i < $num; $i++) {
            if ($ins[$i][0] == 'section_close') {
                $first_sect = $i;
            }
            if ($ins[$i][0] == 'header') {
                /*
                 * Store the position of the last header that is encountered. As section_close/open-instruction are
                 * always (unless some plugin modifies this) around a header instruction this means that the last
                 * position that is stored here is exactly the position of the section_close/open at which the content
                 * is truncated.
                 */
                $endpos = $ins[$i][1][2];
            }
            // only truncate the content and add the read more link when there is really
            // more than that first section
            if (($first_sect) && ($ins[$i][0] == 'section_open')) {
                $ins = array_slice($ins, 0, $first_sect);
                if ($flags['readmore']) {
                    $ins[] = ['plugin', ['include_readmore', [$page]]];
                }
                $ins[] = ['section_close', []];
                // store end position in the include_closelastsecedit instruction so it can generate a matching button
                $ins[] = ['plugin', ['include_closelastsecedit', [$endpos]]];
                return;
            }
        }
    }

    /**
     * Gives a list of pages for a given include statement
     */
    public function getIncludedPages($mode, $page, $sect, $parent_id, $flags)
    {
        global $conf;
        $pages = [];
        switch ($mode) {
            case 'namespace':
                $page = cleanID($page);
                $ns = utf8_encodeFN(str_replace(':', '/', $page));
                // depth is absolute depth, not relative depth, but 0 has a special meaning.
                $depth = $flags['depth'] ? $flags['depth'] + substr_count($page, ':') + ($page ? 1 : 0) : 0;
                search($pagearrays, $conf['datadir'], 'search_allpages', ['depth' => $depth, 'skipacl' => false], $ns);
                if (is_array($pagearrays)) {
                    foreach ($pagearrays as $pagearray) {
                        if (!isHiddenPage($pagearray['id'])) // skip hidden pages
                            $pages[] = $pagearray['id'];
                    }
                }
                break;
            case 'tagtopic':
                if (!$this->taghelper)
                    $this->taghelper = plugin_load('helper', 'tag');
                if (!$this->taghelper) {
                    msg('You have to install the tag plugin to use this functionality!', -1);
                    return [];
                }
                $tag = $page;
                $sect = '';
                $pagearrays = $this->taghelper->getTopic('', null, $tag);
                foreach ($pagearrays as $pagearray) {
                    $pages[] = $pagearray['id'];
                }
                break;
            default:
                $page = $this->applyMacro($page, $parent_id);
                // resolve shortcuts and clean ID
                $page = (new PageResolver($parent_id))->resolveId($page);
                if (auth_quickaclcheck($page) >= AUTH_READ)
                    $pages[] = $page;
        }

        if (isset($flags['exclude']))
            $pages = array_filter($pages, function ($page) use ($flags) {
                if (@preg_match($flags['exclude'], $page))
                    return false;
                return true;
            });

        if (count($pages) > 1) {
            if ($flags['order'] === 'id') {
                if ($flags['rsort']) {
                    usort($pages, [$this, 'reverseStrnatcasecmp']);
                } else {
                    natcasesort($pages);
                }
            } else {
                $ordered_pages = [];
                foreach ($pages as $page) {
                    $key = '';
                    switch ($flags['order']) {
                        case 'title':
                            $key = p_get_first_heading($page);
                            break;
                        case 'created':
                            $key = p_get_metadata($page, 'date created', METADATA_DONT_RENDER);
                            break;
                        case 'modified':
                            $key = p_get_metadata($page, 'date modified', METADATA_DONT_RENDER);
                            break;
                        case 'indexmenu':
                            $key = p_get_metadata($page, 'indexmenu_n', METADATA_RENDER_USING_SIMPLE_CACHE);
                            if ($key === null)
                                $key = '';
                            break;
                        case 'custom':
                            $key = p_get_metadata($page, 'include_n', METADATA_RENDER_USING_SIMPLE_CACHE);
                            if ($key === null)
                                $key = '';
                            break;
                    }
                    $key .= '_' . $page;
                    $ordered_pages[$key] = $page;
                }
                if ($flags['rsort']) {
                    uksort($ordered_pages, [$this, 'reverseStrnatcasecmp']);
                } else {
                    uksort($ordered_pages, 'strnatcasecmp');
                }
                $pages = $ordered_pages;
            }
        }

        $result = [];
        foreach ($pages as $page) {
            $exists = page_exists($page);
            $result[] = ['id' => $page, 'exists' => $exists, 'parent_id' => $parent_id];
        }
        return $result;
    }

    /**
     * String comparisons using a "natural order" algorithm in reverse order
     *
     * @link http://php.net/manual/en/function.strnatcmp.php
     * @param string $a First string
     * @param string $b Second string
     * @return int Similar to other string comparison functions, this one returns &lt; 0 if
     * str1 is greater than str2; &gt;
     * 0 if str1 is lesser than
     * str2, and 0 if they are equal.
     */
    public function reverseStrnatcasecmp($a, $b)
    {
        return strnatcasecmp($b, $a);
    }

    /**
     * This function generates the list of all included pages from a list of metadata
     * instructions.
     */
    public function getIncludedPagesFromMetaInstructions($instructions)
    {
        $pages = [];
        foreach ($instructions as $instruction) {
            $mode = $instruction['mode'];
            $page = $instruction['page'];
            $sect = $instruction['sect'];
            $parent_id = $instruction['parent_id'];
            $flags = $instruction['flags'];
            $pages = array_merge($pages, $this->getIncludedPages($mode, $page, $sect, $parent_id, $flags));
        }
        return $pages;
    }

    /**
     *  Get wiki language from "HTTP_ACCEPT_LANGUAGE"
     *  We allow the pattern e.g. "ja,en-US;q=0.7,en;q=0.3"
     */
    protected function getLanguageOfWiki($id, $parent_id)
    {
        global $conf;
        $result = $conf['lang'];
        if (strpos($id, '@BROWSER_LANG@') !== false) {
            $brlangp = "/([a-zA-Z]{1,8}(-[a-zA-Z]{1,8})*|\\*)(;q=(0(.\\d{0,3})?|1(.0{0,3})?))?/";
            if (
                preg_match_all(
                    $brlangp,
                    $_SERVER["HTTP_ACCEPT_LANGUAGE"],
                    $matches,
                    PREG_SET_ORDER
                )
            ) {
                $langs = [];
                foreach ($matches as $match) {
                    $langname = $match[1] == '*' ? $conf['lang'] : $match[1];
                    $qvalue = $match[4] == '' ? 1.0 : $match[4];
                    $langs[$langname] = $qvalue;
                }
                arsort($langs);
                foreach (array_keys($langs) as $lang) {
                    $testpage = $this->applyMacro(str_replace('@BROWSER_LANG@', $lang, $id), $parent_id);
                    $testpage = (new PageResolver($parent_id))->resolveId($testpage);
                    if (page_exists($testpage)) {
                        $result = $lang;
                        break;
                    }
                }
            }
        }
        return cleanID($result);
    }

    /**
     * Makes user or date dependent includes possible
     */
    protected function applyMacro($id, $parent_id)
    {
        global $USERINFO;
        /* @var Input $INPUT */
        global $INPUT;

        // The following is basicaly copied from basicinfo() because
        // this function can be called from within pageinfo() in
        // p_get_metadata and thus we cannot rely on $INFO being set
        if ($INPUT->server->has('REMOTE_USER')) {
            $user = $INPUT->server->str('REMOTE_USER');
        } else {
            // no registered user - use IP
            $user = clientIP(true);
        }

        // Take user's name if possible, login name otherwise
        if (!empty($USERINFO['name'])) {
            $name = $USERINFO['name'];
        } else {
            $name = $user;
        }

        // Take first group if possible
        if (!empty($USERINFO['grps'])) {
            $group = $USERINFO['grps'][0];
        } else {
            $group = 'ALL';
        }

        $time_stamp = time();
        if (preg_match('/@DATE(\w+)@/', $id, $matches)) {
            switch ($matches[1]) {
                case 'PMONTH':
                    $time_stamp = strtotime("-1 month");
                    break;
                case 'NMONTH':
                    $time_stamp = strtotime("+1 month");
                    break;
                case 'NWEEK':
                    $time_stamp = strtotime("+1 week");
                    break;
                case 'PWEEK':
                    $time_stamp = strtotime("-1 week");
                    break;
                case 'TOMORROW':
                    $time_stamp = strtotime("+1 day");
                    break;
                case 'YESTERDAY':
                    $time_stamp = strtotime("-1 day");
                    break;
                case 'NYEAR':
                    $time_stamp = strtotime("+1 year");
                    break;
                case 'PYEAR':
                    $time_stamp = strtotime("-1 year");
                    break;
            }
            $id = preg_replace('/@DATE(\w+)@/', '', $id);
        }

        $replace = [
            '@USER@' => cleanID($user),
            '@NAME@' => cleanID($name),
            '@GROUP@' => cleanID($group),
            '@BROWSER_LANG@' => $this->getLanguageOfWiki($id, $parent_id),
            '@YEAR@' => date('Y', $time_stamp),
            '@MONTH@' => date('m', $time_stamp),
            '@WEEK@' => date('W', $time_stamp),
            '@DAY@' => date('d', $time_stamp),
            '@YEARPMONTH@' => date('Ym', strtotime("-1 month")),
            '@PMONTH@' => date('m', strtotime("-1 month")),
            '@NMONTH@' => date('m', strtotime("+1 month")),
            '@YEARNMONTH@' => date('Ym', strtotime("+1 month")),
            '@YEARPWEEK@' => date('YW', strtotime("-1 week")),
            '@PWEEK@' => date('W', strtotime("-1 week")),
            '@NWEEK@' => date('W', strtotime("+1 week")),
            '@YEARNWEEK@' => date('YW', strtotime("+1 week"))
        ];
        return str_replace(array_keys($replace), array_values($replace), $id);
    }
}