Update Codex from v1.20.0 to v1.20.1

[mediawiki.git] / includes / Category / CategoryViewer.php

<?php
/**
 * List and paging of category members.
 *
 * This program 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 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

namespace MediaWiki\Category;

use Collation;
use HtmlArmor;
use ImageGalleryBase;
use ImageGalleryClassNotFoundException;
use InvalidArgumentException;
use MediaWiki\Cache\LinkCache;
use MediaWiki\Context\ContextSource;
use MediaWiki\Context\IContextSource;
use MediaWiki\Debug\DeprecationHelper;
use MediaWiki\HookContainer\ProtectedHookAccessorTrait;
use MediaWiki\Html\Html;
use MediaWiki\Language\ILanguageConverter;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Page\PageIdentity;
use MediaWiki\Page\PageReference;
use MediaWiki\Title\Title;
use MediaWiki\Title\TitleValue;
use Wikimedia\Rdbms\SelectQueryBuilder;

class CategoryViewer extends ContextSource {
        use ProtectedHookAccessorTrait;
        use DeprecationHelper;

        /** @var int */
        public $limit;

        /** @var array */
        public $from;

        /** @var array */
        public $until;

        /** @var string[] */
        public $articles;

        /** @var array */
        public $articles_start_char;

        /** @var array */
        public $children;

        /** @var array */
        public $children_start_char;

        /** @var bool */
        public $showGallery;

        /** @var array */
        public $imgsNoGallery_start_char;

        /** @var array */
        public $imgsNoGallery;

        /** @var array */
        public $nextPage;

        /** @var array */
        protected $prevPage;

        /** @var array */
        public $flip;

        /** @var PageIdentity */
        protected $page;

        /** @var Collation */
        public $collation;

        /** @var ImageGalleryBase */
        public $gallery;

        /** @var Category Category object for this page. */
        private $cat;

        /** @var array The original query array, to be used in generating paging links. */
        private $query;

        /** @var ILanguageConverter */
        private $languageConverter;

        /**
         * @since 1.19 $context is a second, required parameter
         * @param PageIdentity $page
         * @param IContextSource $context
         * @param array $from An array with keys page, subcat,
         *        and file for offset of results of each section (since 1.17)
         * @param array $until An array with 3 keys for until of each section (since 1.17)
         * @param array $query
         */
        public function __construct( PageIdentity $page, IContextSource $context, array $from = [],
                array $until = [], array $query = []
        ) {
                $this->page = $page;

                $this->deprecatePublicPropertyFallback(
                        'title',
                        '1.37',
                        function (): Title {
                                return Title::newFromPageIdentity( $this->page );
                        },
                        function ( PageIdentity $page ) {
                                $this->page = $page;
                        }
                );

                $this->setContext( $context );
                $this->getOutput()->addModuleStyles( [
                        'mediawiki.action.styles',
                ] );
                $this->from = $from;
                $this->until = $until;
                $this->limit = $context->getConfig()->get( MainConfigNames::CategoryPagingLimit );
                $this->cat = Category::newFromTitle( $page );
                $this->query = $query;
                $this->collation = MediaWikiServices::getInstance()->getCollationFactory()->getCategoryCollation();
                $this->languageConverter = MediaWikiServices::getInstance()
                        ->getLanguageConverterFactory()->getLanguageConverter();
                unset( $this->query['title'] );
        }

        /**
         * Format the category data list.
         *
         * @return string HTML output
         */
        public function getHTML() {
                $this->showGallery = $this->getConfig()->get( MainConfigNames::CategoryMagicGallery )
                        && !$this->getOutput()->getNoGallery();

                $this->clearCategoryState();
                $this->doCategoryQuery();
                $this->finaliseCategoryState();

                $r = $this->getSubcategorySection() .
                        $this->getPagesSection() .
                        $this->getImageSection();

                if ( $r == '' ) {
                        // If there is no category content to display, only
                        // show the top part of the navigation links.
                        // @todo FIXME: Cannot be completely suppressed because it
                        //        is unknown if 'until' or 'from' makes this
                        //        give 0 results.
                        $r = $this->getCategoryTop();
                } else {
                        $r = $this->getCategoryTop() .
                                $r .
                                $this->getCategoryBottom();
                }

                // Give a proper message if category is empty
                if ( $r == '' ) {
                        $r = $this->msg( 'category-empty' )->parseAsBlock();
                }

                $lang = $this->getLanguage();
                $attribs = [
                        'class' => 'mw-category-generated',
                        'lang' => $lang->getHtmlCode(),
                        'dir' => $lang->getDir()
                ];
                # put a div around the headings which are in the user language
                $r = Html::rawElement( 'div', $attribs, $r );

                return $r;
        }

        protected function clearCategoryState() {
                $this->articles = [];
                $this->articles_start_char = [];
                $this->children = [];
                $this->children_start_char = [];
                if ( $this->showGallery ) {
                        // Note that null for mode is taken to mean use default.
                        $mode = $this->getRequest()->getVal( 'gallerymode', null );
                        try {
                                $this->gallery = ImageGalleryBase::factory( $mode, $this->getContext() );
                        } catch ( ImageGalleryClassNotFoundException $e ) {
                                // User specified something invalid, fallback to default.
                                $this->gallery = ImageGalleryBase::factory( false, $this->getContext() );
                        }

                        $this->gallery->setHideBadImages();
                } else {
                        $this->imgsNoGallery = [];
                        $this->imgsNoGallery_start_char = [];
                }
        }

        /**
         * Add a subcategory to the internal lists, using a Category object
         * @param Category $cat
         * @param string $sortkey
         * @param int $pageLength
         */
        public function addSubcategoryObject( Category $cat, $sortkey, $pageLength ) {
                $page = $cat->getPage();
                if ( !$page ) {
                        return;
                }

                // Subcategory; strip the 'Category' namespace from the link text.
                $pageRecord = MediaWikiServices::getInstance()->getPageStore()
                        ->getPageByReference( $page );
                if ( !$pageRecord ) {
                        return;
                }

                $this->children[] = $this->generateLink(
                        'subcat',
                        $pageRecord,
                        $pageRecord->isRedirect(),
                        htmlspecialchars( str_replace( '_', ' ', $pageRecord->getDBkey() ) )
                );

                $this->children_start_char[] =
                        $this->getSubcategorySortChar( $page, $sortkey );
        }

        /**
         * @param string $type
         * @param PageReference $page
         * @param bool $isRedirect
         * @param string|null $html
         * @return string
         * Annotations needed to tell taint about HtmlArmor,
         * due to the use of the hook it is not possible to avoid raw html handling here
         * @param-taint $html tainted
         * @return-taint escaped
         */
        private function generateLink(
                string $type, PageReference $page, bool $isRedirect, ?string $html = null
        ): string {
                $link = null;
                $legacyTitle = MediaWikiServices::getInstance()->getTitleFactory()
                        ->newFromPageReference( $page );
                // @phan-suppress-next-line PhanTypeMismatchArgument Type mismatch on pass-by-ref args
                $this->getHookRunner()->onCategoryViewer__generateLink( $type, $legacyTitle, $html, $link );
                if ( $link === null ) {
                        $linkRenderer = MediaWikiServices::getInstance()->getLinkRenderer();
                        if ( $html !== null ) {
                                $html = new HtmlArmor( $html );
                        }
                        $link = $linkRenderer->makeLink( $page, $html );
                }
                if ( $isRedirect ) {
                        $link = Html::rawElement(
                                'span',
                                [ 'class' => 'redirect-in-category' ],
                                $link
                        );
                }

                return $link;
        }

        /**
         * Get the character to be used for sorting subcategories.
         * If there's a link from Category:A to Category:B, the sortkey of the resulting
         * entry in the categorylinks table is Category:A, not A, which it SHOULD be.
         * Workaround: If sortkey == "Category:".$title, than use $title for sorting,
         * else use sortkey...
         *
         * @param PageIdentity $page
         * @param string $sortkey The human-readable sortkey (before transforming to icu or whatever).
         * @return string
         */
        public function getSubcategorySortChar( PageIdentity $page, string $sortkey ): string {
                $titleText = MediaWikiServices::getInstance()->getTitleFormatter()
                        ->getPrefixedText( $page );
                if ( $titleText === $sortkey ) {
                        $word = $page->getDBkey();
                } else {
                        $word = $sortkey;
                }

                $firstChar = $this->collation->getFirstLetter( $word );

                return $this->languageConverter->convert( $firstChar );
        }

        /**
         * Add a page in the image namespace
         * @param PageReference $page
         * @param string $sortkey
         * @param int $pageLength
         * @param bool $isRedirect
         */
        public function addImage(
                PageReference $page, string $sortkey, int $pageLength, bool $isRedirect = false
        ): void {
                $title = MediaWikiServices::getInstance()->getTitleFactory()
                        ->newFromPageReference( $page );
                if ( $this->showGallery ) {
                        $flip = $this->flip['file'];
                        if ( $flip ) {
                                $this->gallery->insert( $title, '', '', '', [], ImageGalleryBase::LOADING_LAZY );
                        } else {
                                $this->gallery->add( $title, '', '', '', [], ImageGalleryBase::LOADING_LAZY );
                        }
                } else {
                        $this->imgsNoGallery[] = $this->generateLink( 'image', $page, $isRedirect );

                        $this->imgsNoGallery_start_char[] =
                                $this->languageConverter->convert( $this->collation->getFirstLetter( $sortkey ) );
                }
        }

        /**
         * Add a miscellaneous page
         * @param PageReference $page
         * @param string $sortkey
         * @param int $pageLength
         * @param bool $isRedirect
         */
        public function addPage(
                PageReference $page,
                string $sortkey,
                int $pageLength,
                bool $isRedirect = false
        ): void {
                $this->articles[] = $this->generateLink( 'page', $page, $isRedirect );

                $this->articles_start_char[] =
                        $this->languageConverter->convert( $this->collation->getFirstLetter( $sortkey ) );
        }

        protected function finaliseCategoryState() {
                if ( $this->flip['subcat'] ) {
                        $this->children = array_reverse( $this->children );
                        $this->children_start_char = array_reverse( $this->children_start_char );
                }
                if ( $this->flip['page'] ) {
                        $this->articles = array_reverse( $this->articles );
                        $this->articles_start_char = array_reverse( $this->articles_start_char );
                }
                if ( !$this->showGallery && $this->flip['file'] ) {
                        $this->imgsNoGallery = array_reverse( $this->imgsNoGallery );
                        $this->imgsNoGallery_start_char = array_reverse( $this->imgsNoGallery_start_char );
                }
        }

        protected function doCategoryQuery() {
                $dbr = MediaWikiServices::getInstance()->getConnectionProvider()->getReplicaDatabase();

                $this->nextPage = [
                        'page' => null,
                        'subcat' => null,
                        'file' => null,
                ];
                $this->prevPage = [
                        'page' => null,
                        'subcat' => null,
                        'file' => null,
                ];

                $this->flip = [ 'page' => false, 'subcat' => false, 'file' => false ];

                foreach ( [ 'page', 'subcat', 'file' ] as $type ) {
                        # Get the sortkeys for start/end, if applicable.  Note that if
                        # the collation in the database differs from the one
                        # set in $wgCategoryCollation, pagination might go totally haywire.
                        $extraConds = [ 'cl_type' => $type ];
                        if ( isset( $this->from[$type] ) ) {
                                $extraConds[] = $dbr->expr(
                                        'cl_sortkey',
                                        '>=',
                                        $this->collation->getSortKey( $this->from[$type] )
                                );
                        } elseif ( isset( $this->until[$type] ) ) {
                                $extraConds[] = $dbr->expr(
                                        'cl_sortkey',
                                        '<',
                                        $this->collation->getSortKey( $this->until[$type] )
                                );
                                $this->flip[$type] = true;
                        }

                        $queryBuilder = $dbr->newSelectQueryBuilder();
                        $queryBuilder->select( array_merge(
                                        LinkCache::getSelectFields(),
                                        [
                                                'cl_sortkey',
                                                'cat_id',
                                                'cat_title',
                                                'cat_subcats',
                                                'cat_pages',
                                                'cat_files',
                                                'cl_sortkey_prefix',
                                                'cl_collation'
                                        ]
                                ) )
                                ->from( 'page' )
                                ->where( [ 'cl_to' => $this->page->getDBkey() ] )
                                ->andWhere( $extraConds )
                                ->useIndex( [ 'categorylinks' => 'cl_sortkey' ] );

                        if ( $this->flip[$type] ) {
                                $queryBuilder->orderBy( 'cl_sortkey', SelectQueryBuilder::SORT_DESC );
                        } else {
                                $queryBuilder->orderBy( 'cl_sortkey' );
                        }

                        $queryBuilder
                                ->join( 'categorylinks', null, [ 'cl_from = page_id' ] )
                                ->leftJoin( 'category', null, [
                                        'cat_title = page_title',
                                        'page_namespace' => NS_CATEGORY
                                ] )
                                ->limit( $this->limit + 1 )
                                ->caller( __METHOD__ );

                        $res = $queryBuilder->fetchResultSet();

                        $this->getHookRunner()->onCategoryViewer__doCategoryQuery( $type, $res );
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();

                        $count = 0;
                        foreach ( $res as $row ) {
                                $title = Title::newFromRow( $row );
                                $linkCache->addGoodLinkObjFromRow( $title, $row );

                                if ( $row->cl_collation === '' ) {
                                        // Hack to make sure that while updating from 1.16 schema
                                        // and db is inconsistent, that the sky doesn't fall.
                                        // See r83544. Could perhaps be removed in a couple decades...
                                        $humanSortkey = $row->cl_sortkey;
                                } else {
                                        $humanSortkey = $title->getCategorySortkey( $row->cl_sortkey_prefix );
                                }

                                if ( ++$count > $this->limit ) {
                                        # We've reached the one extra which shows that there
                                        # are additional pages to be had. Stop here...
                                        $this->nextPage[$type] = $humanSortkey;
                                        break;
                                }
                                if ( $count == $this->limit ) {
                                        $this->prevPage[$type] = $humanSortkey;
                                }

                                if ( $title->getNamespace() === NS_CATEGORY ) {
                                        $cat = Category::newFromRow( $row, $title );
                                        $this->addSubcategoryObject( $cat, $humanSortkey, $row->page_len );
                                } elseif ( $title->getNamespace() === NS_FILE ) {
                                        $this->addImage( $title, $humanSortkey, $row->page_len, $row->page_is_redirect );
                                } else {
                                        $this->addPage( $title, $humanSortkey, $row->page_len, $row->page_is_redirect );
                                }
                        }
                }
        }

        /**
         * @return string
         */
        protected function getCategoryTop() {
                $r = $this->getCategoryBottom();
                return $r === ''
                        ? $r
                        : "<br style=\"clear:both;\"/>\n" . $r;
        }

        /**
         * @return string
         */
        protected function getSubcategorySection() {
                # Don't show subcategories section if there are none.
                $r = '';
                $rescnt = count( $this->children );
                $dbcnt = $this->cat->getSubcatCount();
                // This function should be called even if the result isn't used, it has side-effects
                $countmsg = $this->getCountMessage( $rescnt, $dbcnt, 'subcat' );

                if ( $rescnt > 0 ) {
                        # Showing subcategories
                        $r .= Html::openElement( 'div', [ 'id' => 'mw-subcategories' ] ) . "\n";
                        $r .= Html::rawElement( 'h2', [], $this->msg( 'subcategories' )->parse() ) . "\n";
                        $r .= $countmsg;
                        $r .= $this->getSectionPagingLinks( 'subcat' );
                        $r .= $this->formatList( $this->children, $this->children_start_char );
                        $r .= $this->getSectionPagingLinks( 'subcat' );
                        $r .= "\n" . Html::closeElement( 'div' );
                }
                return $r;
        }

        /**
         * @return string
         */
        protected function getPagesSection() {
                $name = $this->getOutput()->getUnprefixedDisplayTitle();
                # Don't show articles section if there are none.
                $r = '';

                # @todo FIXME: Here and in the other two sections: we don't need to bother
                # with this rigmarole if the entire category contents fit on one page
                # and have already been retrieved.  We can just use $rescnt in that
                # case and save a query and some logic.
                $dbcnt = $this->cat->getPageCount( Category::COUNT_CONTENT_PAGES );
                $rescnt = count( $this->articles );
                // This function should be called even if the result isn't used, it has side-effects
                $countmsg = $this->getCountMessage( $rescnt, $dbcnt, 'article' );

                if ( $rescnt > 0 ) {
                        $r .= Html::openElement( 'div', [ 'id' => 'mw-pages' ] ) . "\n";
                        $r .= Html::rawElement(
                                'h2',
                                [],
                                $this->msg( 'category_header' )->rawParams( $name )->parse()
                        ) . "\n";
                        $r .= $countmsg;
                        $r .= $this->getSectionPagingLinks( 'page' );
                        $r .= $this->formatList( $this->articles, $this->articles_start_char );
                        $r .= $this->getSectionPagingLinks( 'page' );
                        $r .= "\n" . Html::closeElement( 'div' );
                }
                return $r;
        }

        /**
         * @return string
         */
        protected function getImageSection() {
                $name = $this->getOutput()->getUnprefixedDisplayTitle();
                $r = '';
                $rescnt = $this->showGallery ?
                        $this->gallery->count() :
                        count( $this->imgsNoGallery ?? [] );
                $dbcnt = $this->cat->getFileCount();
                // This function should be called even if the result isn't used, it has side-effects
                $countmsg = $this->getCountMessage( $rescnt, $dbcnt, 'file' );

                if ( $rescnt > 0 ) {
                        $r .= Html::openElement( 'div', [ 'id' => 'mw-category-media' ] ) . "\n";
                        $r .= Html::rawElement(
                                'h2',
                                [],
                                $this->msg( 'category-media-header' )->rawParams( $name )->parse()
                        ) . "\n";
                        $r .= $countmsg;
                        $r .= $this->getSectionPagingLinks( 'file' );
                        if ( $this->showGallery ) {
                                $r .= $this->gallery->toHTML();
                        } else {
                                $r .= $this->formatList( $this->imgsNoGallery, $this->imgsNoGallery_start_char );
                        }
                        $r .= $this->getSectionPagingLinks( 'file' );
                        $r .= "\n" . Html::closeElement( 'div' );
                }
                return $r;
        }

        /**
         * Get the paging links for a section (subcats/pages/files), to go at the top and bottom
         * of the output.
         *
         * @param string $type 'page', 'subcat', or 'file'
         * @return string HTML output, possibly empty if there are no other pages
         */
        private function getSectionPagingLinks( $type ) {
                if ( isset( $this->until[$type] ) ) {
                        // The new value for the until parameter should be pointing to the first
                        // result displayed on the page which is the second last result retrieved
                        // from the database.The next link should have a from parameter pointing
                        // to the until parameter of the current page.
                        if ( $this->nextPage[$type] !== null ) {
                                return $this->pagingLinks(
                                        $this->prevPage[$type] ?? '',
                                        $this->until[$type],
                                        $type
                                );
                        }

                        // If the nextPage variable is null, it means that we have reached the first page
                        // and therefore the previous link should be disabled.
                        return $this->pagingLinks(
                                '',
                                $this->until[$type],
                                $type
                        );
                } elseif ( $this->nextPage[$type] !== null || isset( $this->from[$type] ) ) {
                        return $this->pagingLinks(
                                $this->from[$type] ?? '',
                                $this->nextPage[$type],
                                $type
                        );
                }

                return '';
        }

        /**
         * @return string
         */
        protected function getCategoryBottom() {
                return '';
        }

        /**
         * Format a list of articles chunked by letter, either as a
         * bullet list or a columnar format, depending on the length.
         *
         * @param array $articles
         * @param array $articles_start_char
         * @param int $cutoff
         * @return string
         * @internal
         */
        private function formatList( $articles, $articles_start_char, $cutoff = 6 ) {
                $list = '';
                if ( count( $articles ) > $cutoff ) {
                        $list = self::columnList( $articles, $articles_start_char );
                } elseif ( count( $articles ) > 0 ) {
                        // for short lists of articles in categories.
                        $list = self::shortList( $articles, $articles_start_char );
                }

                $pageLang = MediaWikiServices::getInstance()->getTitleFactory()
                        ->newFromPageIdentity( $this->page )
                        ->getPageLanguage();
                $attribs = [ 'lang' => $pageLang->getHtmlCode(), 'dir' => $pageLang->getDir(),
                        'class' => 'mw-content-' . $pageLang->getDir() ];
                $list = Html::rawElement( 'div', $attribs, $list );

                return $list;
        }

        /**
         * Format a list of articles chunked by letter in a three-column list, ordered
         * vertically. This is used for categories with a significant number of pages.
         *
         * @param string[] $articles HTML links to each article
         * @param string[] $articles_start_char The header characters for each article
         * @param string $cssClasses CSS classes for the wrapper element
         * @return string HTML to output
         * @internal
         */
        public static function columnList(
                $articles,
                $articles_start_char,
                $cssClasses = 'mw-category mw-category-columns'
        ) {
                $columns = array_combine( $articles, $articles_start_char );

                $ret = Html::openElement( 'div', [ 'class' => $cssClasses ] );

                $colContents = [];

                # Kind of like array_flip() here, but we keep duplicates in an
                # array instead of dropping them.
                foreach ( $columns as $article => $char ) {
                        $colContents[$char][] = $article;
                }

                foreach ( $colContents as $char => $articles ) {
                        # Change space to non-breaking space to keep headers aligned
                        $h3char = $char === ' ' ? "\u{00A0}" : htmlspecialchars( $char );

                        $ret .= Html::openElement( 'div', [ 'class' => 'mw-category-group' ] );
                        $ret .= Html::rawElement( 'h3', [], $h3char ) . "\n";
                        $ret .= Html::openElement( 'ul' );
                        $ret .= implode(
                                "\n",
                                array_map(
                                        static function ( $article ) {
                                                return Html::rawElement( 'li', [], $article );
                                        },
                                        $articles
                                )
                        );
                        $ret .= Html::closeElement( 'ul' ) . Html::closeElement( 'div' );

                }

                $ret .= Html::closeElement( 'div' );
                return $ret;
        }

        /**
         * Format a list of articles chunked by letter in a bullet list. This is used
         * for categories with a small number of pages (when columns aren't needed).
         * @param string[] $articles HTML links to each article
         * @param string[] $articles_start_char The header characters for each article
         * @return string HTML to output
         * @internal
         */
        public static function shortList( $articles, $articles_start_char ) {
                return self::columnList( $articles, $articles_start_char, 'mw-category' );
        }

        /**
         * Create paging links, as a helper method to getSectionPagingLinks().
         *
         * @param string $first The 'until' parameter for the generated URL
         * @param string $last The 'from' parameter for the generated URL
         * @param string $type A prefix for parameters, 'page' or 'subcat' or
         *     'file'
         * @return string HTML
         */
        private function pagingLinks( $first, $last, $type = '' ) {
                $prevLink = $this->msg( 'prev-page' )->escaped();

                $linkRenderer = MediaWikiServices::getInstance()->getLinkRenderer();
                if ( $first != '' ) {
                        $prevQuery = $this->query;
                        $prevQuery["{$type}until"] = $first;
                        unset( $prevQuery["{$type}from"] );
                        $prevLink = $linkRenderer->makeKnownLink(
                                $this->addFragmentToTitle( $this->page, $type ),
                                new HtmlArmor( $prevLink ),
                                [],
                                $prevQuery
                        );
                }

                $nextLink = $this->msg( 'next-page' )->escaped();

                if ( $last != '' ) {
                        $lastQuery = $this->query;
                        $lastQuery["{$type}from"] = $last;
                        unset( $lastQuery["{$type}until"] );
                        $nextLink = $linkRenderer->makeKnownLink(
                                $this->addFragmentToTitle( $this->page, $type ),
                                new HtmlArmor( $nextLink ),
                                [],
                                $lastQuery
                        );
                }

                return $this->msg( 'categoryviewer-pagedlinks' )->rawParams( $prevLink, $nextLink )->escaped();
        }

        /**
         * Takes a title, and adds the fragment identifier that
         * corresponds to the correct segment of the category.
         *
         * @param PageReference $page The title (usually $this->title)
         * @param string $section Which section
         * @return LinkTarget
         */
        private function addFragmentToTitle( PageReference $page, string $section ): LinkTarget {
                switch ( $section ) {
                        case 'page':
                                $fragment = 'mw-pages';
                                break;
                        case 'subcat':
                                $fragment = 'mw-subcategories';
                                break;
                        case 'file':
                                $fragment = 'mw-category-media';
                                break;
                        default:
                                throw new InvalidArgumentException( __METHOD__ .
                                        " Invalid section $section." );
                }

                return new TitleValue( $page->getNamespace(),
                        $page->getDBkey(), $fragment );
        }

        /**
         * What to do if the category table conflicts with the number of results
         * returned?  This function says what. Each type is considered independently
         * of the other types.
         *
         * @param int $rescnt The number of items returned by our database query.
         * @param int $dbcnt The number of items according to the category table.
         * @param string $type 'subcat', 'article', or 'file'
         * @return string A message giving the number of items, to output to HTML.
         */
        private function getCountMessage( $rescnt, $dbcnt, $type ) {
                // There are three cases:
                //   1) The category table figure seems good.  It might be wrong, but
                //      we can't do anything about it if we don't recalculate it on ev-
                //      ery category view.
                //   2) The category table figure isn't good, like it's smaller than the
                //      number of actual results, *but* the number of results is less
                //      than $this->limit and there's no offset.  In this case we still
                //      know the right figure.
                //   3) We have no idea.

                // Check if there's a "from" or "until" for anything

                // This is a little ugly, but we seem to use different names
                // for the paging types then for the messages.
                if ( $type === 'article' ) {
                        $pagingType = 'page';
                } else {
                        $pagingType = $type;
                }

                $fromOrUntil = false;
                if ( isset( $this->from[$pagingType] ) || isset( $this->until[$pagingType] ) ) {
                        $fromOrUntil = true;
                }

                if ( $dbcnt == $rescnt ||
                        ( ( $rescnt == $this->limit || $fromOrUntil ) && $dbcnt > $rescnt )
                ) {
                        // Case 1: seems good.
                        $totalcnt = $dbcnt;
                } elseif ( $rescnt < $this->limit && !$fromOrUntil ) {
                        // Case 2: not good, but salvageable.  Use the number of results.
                        $totalcnt = $rescnt;
                } else {
                        // Case 3: hopeless.  Don't give a total count at all.
                        // Messages: category-subcat-count-limited, category-article-count-limited,
                        // category-file-count-limited
                        return $this->msg( "category-$type-count-limited" )->numParams( $rescnt )->parseAsBlock();
                }
                // Messages: category-subcat-count, category-article-count, category-file-count
                return $this->msg( "category-$type-count" )->numParams( $rescnt, $totalcnt )->parseAsBlock();
        }
}

/** @deprecated class alias since 1.40 */
class_alias( CategoryViewer::class, 'CategoryViewer' );