Special case opus mime detction

[mediawiki.git] / languages / LanguageConverter.php

<?php
/**
 * 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
 * @ingroup Language
 */
use MediaWiki\MediaWikiServices;

/**
 * Base class for language conversion.
 * @ingroup Language
 *
 * @author Zhengzhu Feng <zhengzhu@gmail.com>
 * @author fdcn <fdcn64@gmail.com>
 * @author shinjiman <shinjiman@gmail.com>
 * @author PhiLiP <philip.npc@gmail.com>
 */
class LanguageConverter {
        /**
         * languages supporting variants
         * @since 1.20
         * @var array
         */
        static public $languagesWithVariants = [
                'gan',
                'iu',
                'kk',
                'ku',
                'shi',
                'sr',
                'tg',
                'uz',
                'zh',
        ];

        public $mMainLanguageCode;
        public $mVariants;
        public $mVariantFallbacks;
        public $mVariantNames;
        public $mTablesLoaded = false;
        public $mTables;
        // 'bidirectional' 'unidirectional' 'disable' for each variant
        public $mManualLevel;

        /**
         * @var string Memcached key name
         */
        public $mCacheKey;

        public $mLangObj;
        public $mFlags;
        public $mDescCodeSep = ':', $mDescVarSep = ';';
        public $mUcfirst = false;
        public $mConvRuleTitle = false;
        public $mURLVariant;
        public $mUserVariant;
        public $mHeaderVariant;
        public $mMaxDepth = 10;
        public $mVarSeparatorPattern;

        const CACHE_VERSION_KEY = 'VERSION 7';

        /**
         * Constructor
         *
         * @param Language $langobj
         * @param string $maincode The main language code of this language
         * @param array $variants The supported variants of this language
         * @param array $variantfallbacks The fallback language of each variant
         * @param array $flags Defining the custom strings that maps to the flags
         * @param array $manualLevel Limit for supported variants
         */
        public function __construct( $langobj, $maincode, $variants = [],
                                                                $variantfallbacks = [], $flags = [],
                                                                $manualLevel = [] ) {
                global $wgDisabledVariants;
                $this->mLangObj = $langobj;
                $this->mMainLanguageCode = $maincode;
                $this->mVariants = array_diff( $variants, $wgDisabledVariants );
                $this->mVariantFallbacks = $variantfallbacks;
                $this->mVariantNames = Language::fetchLanguageNames();
                $this->mCacheKey = wfMemcKey( 'conversiontables', $maincode );
                $defaultflags = [
                        // 'S' show converted text
                        // '+' add rules for alltext
                        // 'E' the gave flags is error
                        // these flags above are reserved for program
                        'A' => 'A',       // add rule for convert code (all text convert)
                        'T' => 'T',       // title convert
                        'R' => 'R',       // raw content
                        'D' => 'D',       // convert description (subclass implement)
                        '-' => '-',       // remove convert (not implement)
                        'H' => 'H',       // add rule for convert code (but no display in placed code)
                        'N' => 'N'        // current variant name
                ];
                $this->mFlags = array_merge( $defaultflags, $flags );
                foreach ( $this->mVariants as $v ) {
                        if ( array_key_exists( $v, $manualLevel ) ) {
                                $this->mManualLevel[$v] = $manualLevel[$v];
                        } else {
                                $this->mManualLevel[$v] = 'bidirectional';
                        }
                        $this->mFlags[$v] = $v;
                }
        }

        /**
         * Get all valid variants.
         * Call this instead of using $this->mVariants directly.
         *
         * @return array Contains all valid variants
         */
        public function getVariants() {
                return $this->mVariants;
        }

        /**
         * In case some variant is not defined in the markup, we need
         * to have some fallback. For example, in zh, normally people
         * will define zh-hans and zh-hant, but less so for zh-sg or zh-hk.
         * when zh-sg is preferred but not defined, we will pick zh-hans
         * in this case. Right now this is only used by zh.
         *
         * @param string $variant The language code of the variant
         * @return string|array The code of the fallback language or the
         *   main code if there is no fallback
         */
        public function getVariantFallbacks( $variant ) {
                if ( isset( $this->mVariantFallbacks[$variant] ) ) {
                        return $this->mVariantFallbacks[$variant];
                }
                return $this->mMainLanguageCode;
        }

        /**
         * Get the title produced by the conversion rule.
         * @return string The converted title text
         */
        public function getConvRuleTitle() {
                return $this->mConvRuleTitle;
        }

        /**
         * Get preferred language variant.
         * @return string The preferred language code
         */
        public function getPreferredVariant() {
                global $wgDefaultLanguageVariant, $wgUser;

                $req = $this->getURLVariant();

                if ( $wgUser->isSafeToLoad() && $wgUser->isLoggedIn() && !$req ) {
                        $req = $this->getUserVariant();
                } elseif ( !$req ) {
                        $req = $this->getHeaderVariant();
                }

                if ( $wgDefaultLanguageVariant && !$req ) {
                        $req = $this->validateVariant( $wgDefaultLanguageVariant );
                }

                // This function, unlike the other get*Variant functions, is
                // not memoized (i.e. there return value is not cached) since
                // new information might appear during processing after this
                // is first called.
                if ( $this->validateVariant( $req ) ) {
                        return $req;
                }
                return $this->mMainLanguageCode;
        }

        /**
         * Get default variant.
         * This function would not be affected by user's settings
         * @return string The default variant code
         */
        public function getDefaultVariant() {
                global $wgDefaultLanguageVariant;

                $req = $this->getURLVariant();

                if ( !$req ) {
                        $req = $this->getHeaderVariant();
                }

                if ( $wgDefaultLanguageVariant && !$req ) {
                        $req = $this->validateVariant( $wgDefaultLanguageVariant );
                }

                if ( $req ) {
                        return $req;
                }
                return $this->mMainLanguageCode;
        }

        /**
         * Validate the variant
         * @param string $variant The variant to validate
         * @return mixed Returns the variant if it is valid, null otherwise
         */
        public function validateVariant( $variant = null ) {
                if ( $variant !== null && in_array( $variant, $this->mVariants ) ) {
                        return $variant;
                }
                return null;
        }

        /**
         * Get the variant specified in the URL
         *
         * @return mixed Variant if one found, false otherwise.
         */
        public function getURLVariant() {
                global $wgRequest;

                if ( $this->mURLVariant ) {
                        return $this->mURLVariant;
                }

                // see if the preference is set in the request
                $ret = $wgRequest->getText( 'variant' );

                if ( !$ret ) {
                        $ret = $wgRequest->getVal( 'uselang' );
                }

                $this->mURLVariant = $this->validateVariant( $ret );
                return $this->mURLVariant;
        }

        /**
         * Determine if the user has a variant set.
         *
         * @return mixed Variant if one found, false otherwise.
         */
        protected function getUserVariant() {
                global $wgUser, $wgContLang;

                // memoizing this function wreaks havoc on parserTest.php
                /*
                if ( $this->mUserVariant ) {
                        return $this->mUserVariant;
                }
                */

                // Get language variant preference from logged in users
                // Don't call this on stub objects because that causes infinite
                // recursion during initialisation
                if ( !$wgUser->isSafeToLoad() ) {
                        return false;
                }
                if ( $wgUser->isLoggedIn() ) {
                        if ( $this->mMainLanguageCode == $wgContLang->getCode() ) {
                                $ret = $wgUser->getOption( 'variant' );
                        } else {
                                $ret = $wgUser->getOption( 'variant-' . $this->mMainLanguageCode );
                        }
                } else {
                        // figure out user lang without constructing wgLang to avoid
                        // infinite recursion
                        $ret = $wgUser->getOption( 'language' );
                }

                $this->mUserVariant = $this->validateVariant( $ret );
                return $this->mUserVariant;
        }

        /**
         * Determine the language variant from the Accept-Language header.
         *
         * @return mixed Variant if one found, false otherwise.
         */
        protected function getHeaderVariant() {
                global $wgRequest;

                if ( $this->mHeaderVariant ) {
                        return $this->mHeaderVariant;
                }

                // see if some supported language variant is set in the
                // HTTP header.
                $languages = array_keys( $wgRequest->getAcceptLang() );
                if ( empty( $languages ) ) {
                        return null;
                }

                $fallbackLanguages = [];
                foreach ( $languages as $language ) {
                        $this->mHeaderVariant = $this->validateVariant( $language );
                        if ( $this->mHeaderVariant ) {
                                break;
                        }

                        // To see if there are fallbacks of current language.
                        // We record these fallback variants, and process
                        // them later.
                        $fallbacks = $this->getVariantFallbacks( $language );
                        if ( is_string( $fallbacks ) && $fallbacks !== $this->mMainLanguageCode ) {
                                $fallbackLanguages[] = $fallbacks;
                        } elseif ( is_array( $fallbacks ) ) {
                                $fallbackLanguages =
                                        array_merge( $fallbackLanguages, $fallbacks );
                        }
                }

                if ( !$this->mHeaderVariant ) {
                        // process fallback languages now
                        $fallback_languages = array_unique( $fallbackLanguages );
                        foreach ( $fallback_languages as $language ) {
                                $this->mHeaderVariant = $this->validateVariant( $language );
                                if ( $this->mHeaderVariant ) {
                                        break;
                                }
                        }
                }

                return $this->mHeaderVariant;
        }

        /**
         * Dictionary-based conversion.
         * This function would not parse the conversion rules.
         * If you want to parse rules, try to use convert() or
         * convertTo().
         *
         * @param string $text The text to be converted
         * @param bool|string $toVariant The target language code
         * @return string The converted text
         */
        public function autoConvert( $text, $toVariant = false ) {

                $this->loadTables();

                if ( !$toVariant ) {
                        $toVariant = $this->getPreferredVariant();
                        if ( !$toVariant ) {
                                return $text;
                        }
                }

                if ( $this->guessVariant( $text, $toVariant ) ) {
                        return $text;
                }

                /* we convert everything except:
                   1. HTML markups (anything between < and >)
                   2. HTML entities
                   3. placeholders created by the parser
                */
                $marker = '|' . Parser::MARKER_PREFIX . '[\-a-zA-Z0-9]+';

                // this one is needed when the text is inside an HTML markup
                $htmlfix = '|<[^>]+$|^[^<>]*>';

                // disable convert to variants between <code> tags
                $codefix = '<code>.+?<\/code>|';
                // disable conversion of <script> tags
                $scriptfix = '<script.*?>.*?<\/script>|';
                // disable conversion of <pre> tags
                $prefix = '<pre.*?>.*?<\/pre>|';

                $reg = '/' . $codefix . $scriptfix . $prefix .
                        '<[^>]+>|&[a-zA-Z#][a-z0-9]+;' . $marker . $htmlfix . '/s';
                $startPos = 0;
                $sourceBlob = '';
                $literalBlob = '';

                // Guard against delimiter nulls in the input
                $text = str_replace( "\000", '', $text );

                $markupMatches = null;
                $elementMatches = null;
                while ( $startPos < strlen( $text ) ) {
                        if ( preg_match( $reg, $text, $markupMatches, PREG_OFFSET_CAPTURE, $startPos ) ) {
                                $elementPos = $markupMatches[0][1];
                                $element = $markupMatches[0][0];
                        } else {
                                $elementPos = strlen( $text );
                                $element = '';
                        }

                        // Queue the part before the markup for translation in a batch
                        $sourceBlob .= substr( $text, $startPos, $elementPos - $startPos ) . "\000";

                        // Advance to the next position
                        $startPos = $elementPos + strlen( $element );

                        // Translate any alt or title attributes inside the matched element
                        if ( $element !== ''
                                && preg_match( '/^(<[^>\s]*)\s([^>]*)(.*)$/', $element, $elementMatches )
                        ) {
                                $attrs = Sanitizer::decodeTagAttributes( $elementMatches[2] );
                                $changed = false;
                                foreach ( [ 'title', 'alt' ] as $attrName ) {
                                        if ( !isset( $attrs[$attrName] ) ) {
                                                continue;
                                        }
                                        $attr = $attrs[$attrName];
                                        // Don't convert URLs
                                        if ( !strpos( $attr, '://' ) ) {
                                                $attr = $this->recursiveConvertTopLevel( $attr, $toVariant );
                                        }

                                        if ( $attr !== $attrs[$attrName] ) {
                                                $attrs[$attrName] = $attr;
                                                $changed = true;
                                        }
                                }
                                if ( $changed ) {
                                        $element = $elementMatches[1] . Html::expandAttributes( $attrs ) .
                                                $elementMatches[3];
                                }
                        }
                        $literalBlob .= $element . "\000";
                }

                // Do the main translation batch
                $translatedBlob = $this->translate( $sourceBlob, $toVariant );

                // Put the output back together
                $translatedIter = StringUtils::explode( "\000", $translatedBlob );
                $literalIter = StringUtils::explode( "\000", $literalBlob );
                $output = '';
                while ( $translatedIter->valid() && $literalIter->valid() ) {
                        $output .= $translatedIter->current();
                        $output .= $literalIter->current();
                        $translatedIter->next();
                        $literalIter->next();
                }

                return $output;
        }

        /**
         * Translate a string to a variant.
         * Doesn't parse rules or do any of that other stuff, for that use
         * convert() or convertTo().
         *
         * @param string $text Text to convert
         * @param string $variant Variant language code
         * @return string Translated text
         */
        public function translate( $text, $variant ) {
                // If $text is empty or only includes spaces, do nothing
                // Otherwise translate it
                if ( trim( $text ) ) {
                        $this->loadTables();
                        $text = $this->mTables[$variant]->replace( $text );
                }
                return $text;
        }

        /**
         * Call translate() to convert text to all valid variants.
         *
         * @param string $text The text to be converted
         * @return array Variant => converted text
         */
        public function autoConvertToAllVariants( $text ) {
                $this->loadTables();

                $ret = [];
                foreach ( $this->mVariants as $variant ) {
                        $ret[$variant] = $this->translate( $text, $variant );
                }

                return $ret;
        }

        /**
         * Apply manual conversion rules.
         *
         * @param ConverterRule $convRule
         */
        protected function applyManualConv( $convRule ) {
                // Use syntax -{T|zh-cn:TitleCN; zh-tw:TitleTw}- to custom
                // title conversion.
                // Bug 24072: $mConvRuleTitle was overwritten by other manual
                // rule(s) not for title, this breaks the title conversion.
                $newConvRuleTitle = $convRule->getTitle();
                if ( $newConvRuleTitle ) {
                        // So I add an empty check for getTitle()
                        $this->mConvRuleTitle = $newConvRuleTitle;
                }

                // merge/remove manual conversion rules to/from global table
                $convTable = $convRule->getConvTable();
                $action = $convRule->getRulesAction();
                foreach ( $convTable as $variant => $pair ) {
                        if ( !$this->validateVariant( $variant ) ) {
                                continue;
                        }

                        if ( $action == 'add' ) {
                                // More efficient than array_merge(), about 2.5 times.
                                foreach ( $pair as $from => $to ) {
                                        $this->mTables[$variant]->setPair( $from, $to );
                                }
                        } elseif ( $action == 'remove' ) {
                                $this->mTables[$variant]->removeArray( $pair );
                        }
                }
        }

        /**
         * Auto convert a Title object to a readable string in the
         * preferred variant.
         *
         * @param Title $title A object of Title
         * @return string Converted title text
         */
        public function convertTitle( $title ) {
                $variant = $this->getPreferredVariant();
                $index = $title->getNamespace();
                if ( $index !== NS_MAIN ) {
                        $text = $this->convertNamespace( $index, $variant ) . ':';
                } else {
                        $text = '';
                }
                $text .= $this->translate( $title->getText(), $variant );
                return $text;
        }

        /**
         * Get the namespace display name in the preferred variant.
         *
         * @param int $index Namespace id
         * @param string|null $variant Variant code or null for preferred variant
         * @return string Namespace name for display
         */
        public function convertNamespace( $index, $variant = null ) {
                if ( $index === NS_MAIN ) {
                        return '';
                }

                if ( $variant === null ) {
                        $variant = $this->getPreferredVariant();
                }

                $cache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
                $key = $cache->makeKey( 'languageconverter', 'namespace-text', $index, $variant );
                $nsVariantText = $cache->get( $key );
                if ( $nsVariantText !== false ) {
                        return $nsVariantText;
                }

                // First check if a message gives a converted name in the target variant.
                $nsConvMsg = wfMessage( 'conversion-ns' . $index )->inLanguage( $variant );
                if ( $nsConvMsg->exists() ) {
                        $nsVariantText = $nsConvMsg->plain();
                }

                // Then check if a message gives a converted name in content language
                // which needs extra translation to the target variant.
                if ( $nsVariantText === false ) {
                        $nsConvMsg = wfMessage( 'conversion-ns' . $index )->inContentLanguage();
                        if ( $nsConvMsg->exists() ) {
                                $nsVariantText = $this->translate( $nsConvMsg->plain(), $variant );
                        }
                }

                if ( $nsVariantText === false ) {
                        // No message exists, retrieve it from the target variant's namespace names.
                        $langObj = $this->mLangObj->factory( $variant );
                        $nsVariantText = $langObj->getFormattedNsText( $index );
                }

                $cache->set( $key, $nsVariantText, 60 );

                return $nsVariantText;
        }

        /**
         * Convert text to different variants of a language. The automatic
         * conversion is done in autoConvert(). Here we parse the text
         * marked with -{}-, which specifies special conversions of the
         * text that can not be accomplished in autoConvert().
         *
         * Syntax of the markup:
         * -{code1:text1;code2:text2;...}-  or
         * -{flags|code1:text1;code2:text2;...}-  or
         * -{text}- in which case no conversion should take place for text
         *
         * @param string $text Text to be converted
         * @return string Converted text
         */
        public function convert( $text ) {
                $variant = $this->getPreferredVariant();
                return $this->convertTo( $text, $variant );
        }

        /**
         * Same as convert() except a extra parameter to custom variant.
         *
         * @param string $text Text to be converted
         * @param string $variant The target variant code
         * @return string Converted text
         */
        public function convertTo( $text, $variant ) {
                global $wgDisableLangConversion;
                if ( $wgDisableLangConversion ) {
                        return $text;
                }
                // Reset converter state for a new converter run.
                $this->mConvRuleTitle = false;
                return $this->recursiveConvertTopLevel( $text, $variant );
        }

        /**
         * Recursively convert text on the outside. Allow to use nested
         * markups to custom rules.
         *
         * @param string $text Text to be converted
         * @param string $variant The target variant code
         * @param int $depth Depth of recursion
         * @return string Converted text
         */
        protected function recursiveConvertTopLevel( $text, $variant, $depth = 0 ) {
                $startPos = 0;
                $out = '';
                $length = strlen( $text );
                $shouldConvert = !$this->guessVariant( $text, $variant );

                while ( $startPos < $length ) {
                        $pos = strpos( $text, '-{', $startPos );

                        if ( $pos === false ) {
                                // No more markup, append final segment
                                $fragment = substr( $text, $startPos );
                                $out .= $shouldConvert ? $this->autoConvert( $fragment, $variant ) : $fragment;
                                return $out;
                        }

                        // Markup found
                        // Append initial segment
                        $fragment = substr( $text, $startPos, $pos - $startPos );
                        $out .= $shouldConvert ? $this->autoConvert( $fragment, $variant ) : $fragment;

                        // Advance position
                        $startPos = $pos;

                        // Do recursive conversion
                        $out .= $this->recursiveConvertRule( $text, $variant, $startPos, $depth + 1 );
                }

                return $out;
        }

        /**
         * Recursively convert text on the inside.
         *
         * @param string $text Text to be converted
         * @param string $variant The target variant code
         * @param int $startPos
         * @param int $depth Depth of recursion
         *
         * @throws MWException
         * @return string Converted text
         */
        protected function recursiveConvertRule( $text, $variant, &$startPos, $depth = 0 ) {
                // Quick sanity check (no function calls)
                if ( $text[$startPos] !== '-' || $text[$startPos + 1] !== '{' ) {
                        throw new MWException( __METHOD__ . ': invalid input string' );
                }

                $startPos += 2;
                $inner = '';
                $warningDone = false;
                $length = strlen( $text );

                while ( $startPos < $length ) {
                        $m = false;
                        preg_match( '/-\{|\}-/', $text, $m, PREG_OFFSET_CAPTURE, $startPos );
                        if ( !$m ) {
                                // Unclosed rule
                                break;
                        }

                        $token = $m[0][0];
                        $pos = $m[0][1];

                        // Markup found
                        // Append initial segment
                        $inner .= substr( $text, $startPos, $pos - $startPos );

                        // Advance position
                        $startPos = $pos;

                        switch ( $token ) {
                                case '-{':
                                        // Check max depth
                                        if ( $depth >= $this->mMaxDepth ) {
                                                $inner .= '-{';
                                                if ( !$warningDone ) {
                                                        $inner .= '<span class="error">' .
                                                                wfMessage( 'language-converter-depth-warning' )
                                                                        ->numParams( $this->mMaxDepth )->inContentLanguage()->text() .
                                                                '</span>';
                                                        $warningDone = true;
                                                }
                                                $startPos += 2;
                                                continue;
                                        }
                                        // Recursively parse another rule
                                        $inner .= $this->recursiveConvertRule( $text, $variant, $startPos, $depth + 1 );
                                        break;
                                case '}-':
                                        // Apply the rule
                                        $startPos += 2;
                                        $rule = new ConverterRule( $inner, $this );
                                        $rule->parse( $variant );
                                        $this->applyManualConv( $rule );
                                        return $rule->getDisplay();
                                default:
                                        throw new MWException( __METHOD__ . ': invalid regex match' );
                        }
                }

                // Unclosed rule
                if ( $startPos < $length ) {
                        $inner .= substr( $text, $startPos );
                }
                $startPos = $length;
                return '-{' . $this->autoConvert( $inner, $variant );
        }

        /**
         * If a language supports multiple variants, it is possible that
         * non-existing link in one variant actually exists in another variant.
         * This function tries to find it. See e.g. LanguageZh.php
         * The input parameters may be modified upon return
         *
         * @param string &$link The name of the link
         * @param Title &$nt The title object of the link
         * @param bool $ignoreOtherCond To disable other conditions when
         *   we need to transclude a template or update a category's link
         */
        public function findVariantLink( &$link, &$nt, $ignoreOtherCond = false ) {
                # If the article has already existed, there is no need to
                # check it again, otherwise it may cause a fault.
                if ( is_object( $nt ) && $nt->exists() ) {
                        return;
                }

                global $wgDisableLangConversion, $wgDisableTitleConversion, $wgRequest;
                $isredir = $wgRequest->getText( 'redirect', 'yes' );
                $action = $wgRequest->getText( 'action' );
                if ( $action == 'edit' && $wgRequest->getBool( 'redlink' ) ) {
                        $action = 'view';
                }
                $linkconvert = $wgRequest->getText( 'linkconvert', 'yes' );
                $disableLinkConversion = $wgDisableLangConversion
                        || $wgDisableTitleConversion;
                $linkBatch = new LinkBatch();

                $ns = NS_MAIN;

                if ( $disableLinkConversion ||
                        ( !$ignoreOtherCond &&
                                ( $isredir == 'no'
                                        || $action == 'edit'
                                        || $action == 'submit'
                                        || $linkconvert == 'no' ) ) ) {
                        return;
                }

                if ( is_object( $nt ) ) {
                        $ns = $nt->getNamespace();
                }

                $variants = $this->autoConvertToAllVariants( $link );
                if ( !$variants ) { // give up
                        return;
                }

                $titles = [];

                foreach ( $variants as $v ) {
                        if ( $v != $link ) {
                                $varnt = Title::newFromText( $v, $ns );
                                if ( !is_null( $varnt ) ) {
                                        $linkBatch->addObj( $varnt );
                                        $titles[] = $varnt;
                                }
                        }
                }

                // fetch all variants in single query
                $linkBatch->execute();

                foreach ( $titles as $varnt ) {
                        if ( $varnt->getArticleID() > 0 ) {
                                $nt = $varnt;
                                $link = $varnt->getText();
                                break;
                        }
                }
        }

        /**
         * Returns language specific hash options.
         *
         * @return string
         */
        public function getExtraHashOptions() {
                $variant = $this->getPreferredVariant();

                return '!' . $variant;
        }

        /**
         * Guess if a text is written in a variant. This should be implemented in subclasses.
         *
         * @param string $text The text to be checked
         * @param string $variant Language code of the variant to be checked for
         * @return bool True if $text appears to be written in $variant, false if not
         *
         * @author Nikola Smolenski <smolensk@eunet.rs>
         * @since 1.19
         */
        public function guessVariant( $text, $variant ) {
                return false;
        }

        /**
         * Load default conversion tables.
         * This method must be implemented in derived class.
         *
         * @private
         * @throws MWException
         */
        function loadDefaultTables() {
                $name = get_class( $this );

                throw new MWException( "Must implement loadDefaultTables() method in class $name" );
        }

        /**
         * Load conversion tables either from the cache or the disk.
         * @private
         * @param bool $fromCache Load from memcached? Defaults to true.
         */
        function loadTables( $fromCache = true ) {
                global $wgLanguageConverterCacheType;

                if ( $this->mTablesLoaded ) {
                        return;
                }

                $this->mTablesLoaded = true;
                $this->mTables = false;
                $cache = ObjectCache::getInstance( $wgLanguageConverterCacheType );
                if ( $fromCache ) {
                        wfProfileIn( __METHOD__ . '-cache' );
                        $this->mTables = $cache->get( $this->mCacheKey );
                        wfProfileOut( __METHOD__ . '-cache' );
                }
                if ( !$this->mTables || !array_key_exists( self::CACHE_VERSION_KEY, $this->mTables ) ) {
                        wfProfileIn( __METHOD__ . '-recache' );
                        // not in cache, or we need a fresh reload.
                        // We will first load the default tables
                        // then update them using things in MediaWiki:Conversiontable/*
                        $this->loadDefaultTables();
                        foreach ( $this->mVariants as $var ) {
                                $cached = $this->parseCachedTable( $var );
                                $this->mTables[$var]->mergeArray( $cached );
                        }

                        $this->postLoadTables();
                        $this->mTables[self::CACHE_VERSION_KEY] = true;

                        $cache->set( $this->mCacheKey, $this->mTables, 43200 );
                        wfProfileOut( __METHOD__ . '-recache' );
                }
        }

        /**
         * Hook for post processing after conversion tables are loaded.
         */
        function postLoadTables() {
        }

        /**
         * Reload the conversion tables.
         *
         * @private
         */
        function reloadTables() {
                if ( $this->mTables ) {
                        unset( $this->mTables );
                }

                $this->mTablesLoaded = false;
                $this->loadTables( false );
        }

        /**
         * Parse the conversion table stored in the cache.
         *
         * The tables should be in blocks of the following form:
         *              -{
         *                      word => word ;
         *                      word => word ;
         *                      ...
         *              }-
         *
         * To make the tables more manageable, subpages are allowed
         * and will be parsed recursively if $recursive == true.
         *
         * @param string $code Language code
         * @param string $subpage Subpage name
         * @param bool $recursive Parse subpages recursively? Defaults to true.
         *
         * @return array
         */
        function parseCachedTable( $code, $subpage = '', $recursive = true ) {
                static $parsed = [];

                $key = 'Conversiontable/' . $code;
                if ( $subpage ) {
                        $key .= '/' . $subpage;
                }
                if ( array_key_exists( $key, $parsed ) ) {
                        return [];
                }

                $parsed[$key] = true;

                if ( $subpage === '' ) {
                        $txt = MessageCache::singleton()->getMsgFromNamespace( $key, $code );
                } else {
                        $txt = false;
                        $title = Title::makeTitleSafe( NS_MEDIAWIKI, $key );
                        if ( $title && $title->exists() ) {
                                $revision = Revision::newFromTitle( $title );
                                if ( $revision ) {
                                        if ( $revision->getContentModel() == CONTENT_MODEL_WIKITEXT ) {
                                                $txt = $revision->getContent( Revision::RAW )->getNativeData();
                                        }

                                        // @todo in the future, use a specialized content model, perhaps based on json!
                                }
                        }
                }

                # Nothing to parse if there's no text
                if ( $txt === false || $txt === null || $txt === '' ) {
                        return [];
                }

                // get all subpage links of the form
                // [[MediaWiki:Conversiontable/zh-xx/...|...]]
                $linkhead = $this->mLangObj->getNsText( NS_MEDIAWIKI ) .
                        ':Conversiontable';
                $subs = StringUtils::explode( '[[', $txt );
                $sublinks = [];
                foreach ( $subs as $sub ) {
                        $link = explode( ']]', $sub, 2 );
                        if ( count( $link ) != 2 ) {
                                continue;
                        }
                        $b = explode( '|', $link[0], 2 );
                        $b = explode( '/', trim( $b[0] ), 3 );
                        if ( count( $b ) == 3 ) {
                                $sublink = $b[2];
                        } else {
                                $sublink = '';
                        }

                        if ( $b[0] == $linkhead && $b[1] == $code ) {
                                $sublinks[] = $sublink;
                        }
                }

                // parse the mappings in this page
                $blocks = StringUtils::explode( '-{', $txt );
                $ret = [];
                $first = true;
                foreach ( $blocks as $block ) {
                        if ( $first ) {
                                // Skip the part before the first -{
                                $first = false;
                                continue;
                        }
                        $mappings = explode( '}-', $block, 2 )[0];
                        $stripped = str_replace( [ "'", '"', '*', '#' ], '', $mappings );
                        $table = StringUtils::explode( ';', $stripped );
                        foreach ( $table as $t ) {
                                $m = explode( '=>', $t, 3 );
                                if ( count( $m ) != 2 ) {
                                        continue;
                                }
                                // trim any trailling comments starting with '//'
                                $tt = explode( '//', $m[1], 2 );
                                $ret[trim( $m[0] )] = trim( $tt[0] );
                        }
                }

                // recursively parse the subpages
                if ( $recursive ) {
                        foreach ( $sublinks as $link ) {
                                $s = $this->parseCachedTable( $code, $link, $recursive );
                                $ret = $s + $ret;
                        }
                }

                if ( $this->mUcfirst ) {
                        foreach ( $ret as $k => $v ) {
                                $ret[$this->mLangObj->ucfirst( $k )] = $this->mLangObj->ucfirst( $v );
                        }
                }
                return $ret;
        }

        /**
         * Enclose a string with the "no conversion" tag. This is used by
         * various functions in the Parser.
         *
         * @param string $text Text to be tagged for no conversion
         * @param bool $noParse Unused
         * @return string The tagged text
         */
        public function markNoConversion( $text, $noParse = false ) {
                # don't mark if already marked
                if ( strpos( $text, '-{' ) || strpos( $text, '}-' ) ) {
                        return $text;
                }

                $ret = "-{R|$text}-";
                return $ret;
        }

        /**
         * Convert the sorting key for category links. This should make different
         * keys that are variants of each other map to the same key.
         *
         * @param string $key
         *
         * @return string
         */
        function convertCategoryKey( $key ) {
                return $key;
        }

        /**
         * Refresh the cache of conversion tables when
         * MediaWiki:Conversiontable* is updated.
         *
         * @param Title $titleobj The Title of the page being updated
         */
        public function updateConversionTable( Title $titleobj ) {
                if ( $titleobj->getNamespace() == NS_MEDIAWIKI ) {
                        $title = $titleobj->getDBkey();
                        $t = explode( '/', $title, 3 );
                        $c = count( $t );
                        if ( $c > 1 && $t[0] == 'Conversiontable' ) {
                                if ( $this->validateVariant( $t[1] ) ) {
                                        $this->reloadTables();
                                }
                        }
                }
        }

        /**
         * Get the cached separator pattern for ConverterRule::parseRules()
         * @return string
         */
        function getVarSeparatorPattern() {
                if ( is_null( $this->mVarSeparatorPattern ) ) {
                        // varsep_pattern for preg_split:
                        // text should be splited by ";" only if a valid variant
                        // name exist after the markup, for example:
                        //  -{zh-hans:<span style="font-size:120%;">xxx</span>;zh-hant:\
                        //      <span style="font-size:120%;">yyy</span>;}-
                        // we should split it as:
                        //  [
                        //        [0] => 'zh-hans:<span style="font-size:120%;">xxx</span>'
                        //        [1] => 'zh-hant:<span style="font-size:120%;">yyy</span>'
                        //        [2] => ''
                        //  ]
                        $pat = '/;\s*(?=';
                        foreach ( $this->mVariants as $variant ) {
                                // zh-hans:xxx;zh-hant:yyy
                                $pat .= $variant . '\s*:|';
                                // xxx=>zh-hans:yyy; xxx=>zh-hant:zzz
                                $pat .= '[^;]*?=>\s*' . $variant . '\s*:|';
                        }
                        $pat .= '\s*$)/';
                        $this->mVarSeparatorPattern = $pat;
                }
                return $this->mVarSeparatorPattern;
        }
}