LanguageConverter.php

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<?php
namespace MediaWiki\Language;
 
use InvalidArgumentException;
use MediaWiki\Context\RequestContext;
use MediaWiki\Debug\DeprecationHelper;
use MediaWiki\HookContainer\HookRunner;
use MediaWiki\Html\Html;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Page\PageIdentity;
use MediaWiki\Parser\Parser;
use MediaWiki\Parser\Sanitizer;
use MediaWiki\Revision\RevisionRecord;
use MediaWiki\Revision\SlotRecord;
use MediaWiki\StubObject\StubUserLang;
use MediaWiki\Title\Title;
use MediaWiki\User\User;
use RuntimeException;
use UnexpectedValueException;
use Wikimedia\ObjectCache\BagOStuff;
use Wikimedia\Parsoid\DOM\Document;
use Wikimedia\Parsoid\DOM\DocumentFragment;
use Wikimedia\Parsoid\Utils\DOMCompat;
use Wikimedia\ReplacementArray;
use Wikimedia\StringUtils\StringUtils;
 
abstract class LanguageConverter implements ILanguageConverter {
    use DeprecationHelper;
 
    public static $languagesWithVariants = [
        'ban',
        'crh',
        'en',
        'gan',
        'iu',
        'ku',
        'mni',
        'sh',
        'shi',
        'sr',
        'tg',
        'tly',
        'uz',
        'wuu',
        'zgh',
        'zh',
    ];
 
    public static $languagesWithStaticDefaultVariant = [
        'ban' => 'ban',
        'crh' => 'crh',
        'en' => 'en',
        'gan' => 'gan',
        'iu' => 'iu',
        'ku' => 'ku',
        'mni' => 'mni',
        'sh' => 'sh-latn',
        'shi' => 'shi',
        'sr' => 'sr',
        'tg' => 'tg',
        'tly' => 'tly',
        'uz' => 'uz',
        'wuu' => 'wuu',
        'zgh' => 'zgh',
        'zh' => 'zh',
    ];
 
    private $mTablesLoaded = false;
    protected $mTables = [];
    private $mLangObj;
 
    private string|DocumentFragment|false $mConvRuleTitle = false;
 
    private $mURLVariant;
    private $mUserVariant;
    private $mHeaderVariant;
    private $mMaxDepth = 10;
    private $mVarSeparatorPattern;
 
    private const CACHE_VERSION_KEY = 'VERSION 8';
 
    public function __construct( $langobj ) {
        $this->mLangObj = $langobj;
    }
 
    abstract public function getMainCode(): string;
 
    protected function getStaticDefaultVariant(): string {
        $code = $this->getMainCode();
        return self::$languagesWithStaticDefaultVariant[$code] ?? $code;
    }
 
    abstract protected function getLanguageVariants(): array;
 
    abstract public function getVariantsFallbacks(): array;
 
    final public function getFlags(): array {
        $defaultflags = [
            // 'S' show the converted text
            // '+' add rules for alltext
            // 'E' the flags have an error
            // these flags above are reserved for program
            'A' => 'A', // add rule for convert code (all text converted)
            '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
        ];
        $flags = array_merge( $defaultflags, $this->getAdditionalFlags() );
        foreach ( $this->getVariants() as $v ) {
            $flags[$v] = $v;
        }
        return $flags;
    }
 
    protected function getAdditionalFlags(): array {
        return [];
    }
 
    final public function getManualLevel() {
        $manualLevel  = $this->getAdditionalManualLevel();
        $result = [];
        foreach ( $this->getVariants() as $v ) {
            if ( array_key_exists( $v, $manualLevel ) ) {
                $result[$v] = $manualLevel[$v];
            } else {
                $result[$v] = 'bidirectional';
            }
        }
        return $result;
    }
 
    protected function getAdditionalManualLevel(): array {
        return [];
    }
 
    public function getDescCodeSeparator(): string {
        return ':';
    }
 
    public function getDescVarSeparator(): string {
        return ';';
    }
 
    public function getVariantNames(): array {
        return MediaWikiServices::getInstance()
            ->getLanguageNameUtils()
            ->getLanguageNames();
    }
 
    final public function getVariants() {
        $disabledVariants = MediaWikiServices::getInstance()->getMainConfig()->get(
            MainConfigNames::DisabledVariants );
        return array_diff( $this->getLanguageVariants(), $disabledVariants );
    }
 
    public function getVariantFallbacks( $variant ) {
        return $this->getVariantsFallbacks()[$variant] ?? $this->getStaticDefaultVariant();
    }
 
    public function getConvRuleTitle() {
        $title = $this->mConvRuleTitle;
        if ( $title instanceof DocumentFragment ) {
            return $title->textContent;
        }
        return $title;
    }
 
    public function getConvRuleTitleFragment( Document $ownerDocument ): ?DocumentFragment {
        $title = $this->mConvRuleTitle;
        if ( $title instanceof DocumentFragment || $title === false ) {
            return $title ?: null;
        }
        $df = $ownerDocument->createDocumentFragment();
        DOMCompat::replaceChildren( $df, $title );
        return $df;
    }
 
    public function getPreferredVariant() {
        $req = $this->getURLVariant();
 
        $services = MediaWikiServices::getInstance();
        ( new HookRunner( $services->getHookContainer() ) )->onGetLangPreferredVariant( $req );
 
        if ( !$req ) {
            $user = RequestContext::getMain()->getUser();
            // NOTE: For some calls there may not be a context user or session that is safe
            // to use, see (T235360)
            // Use case: During user autocreation, UserNameUtils::isUsable is called which uses interface
            // messages for reserved usernames.
            if ( $user->isSafeToLoad() && $user->isRegistered() ) {
                $req = $this->getUserVariant( $user );
            } else {
                $req = $this->getHeaderVariant();
            }
        }
 
        $defaultLanguageVariant = $services->getMainConfig()
            ->get( MainConfigNames::DefaultLanguageVariant );
        if ( !$req && $defaultLanguageVariant ) {
            $req = $defaultLanguageVariant;
        }
 
        $req = $this->validateVariant( $req );
 
        // 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.
        return $req ?? $this->getStaticDefaultVariant();
    }
 
    public function getDefaultVariant() {
        $defaultLanguageVariant = MediaWikiServices::getInstance()->getMainConfig()->get(
            MainConfigNames::DefaultLanguageVariant );
 
        $req = $this->getURLVariant() ?? $this->getHeaderVariant();
 
        if ( !$req && $defaultLanguageVariant ) {
            $req = $this->validateVariant( $defaultLanguageVariant );
        }
 
        return $req ?? $this->getStaticDefaultVariant();
    }
 
    public function validateVariant( $variant = null ) {
        if ( $variant === null ) {
            return null;
        }
        // Our internal variants are always lower-case; the variant we
        // are validating may have mixed cases.
        $variant = LanguageCode::replaceDeprecatedCodes( strtolower( $variant ) );
        if ( in_array( $variant, $this->getVariants() ) ) {
            return $variant;
        }
        // Browsers are supposed to use BCP 47 standard in the
        // Accept-Language header, but not all of our internal
        // mediawiki variant codes are BCP 47.  Map BCP 47 code
        // to our internal code.
        foreach ( $this->getVariants() as $v ) {
            // Case-insensitive match (BCP 47 is mixed-case)
            if ( strtolower( LanguageCode::bcp47( $v ) ) === $variant ) {
                return $v;
            }
        }
        return null;
    }
 
    public function getURLVariant() {
        if ( $this->mURLVariant ) {
            return $this->mURLVariant;
        }
 
        $request = RequestContext::getMain()->getRequest();
        // see if the preference is set in the request
        $ret = $request->getText( 'variant' );
 
        if ( !$ret ) {
            $ret = $request->getVal( 'uselang' );
        }
 
        $this->mURLVariant = $this->validateVariant( $ret );
        return $this->mURLVariant;
    }
 
    protected function getUserVariant( User $user ) {
        // This should only be called within the class after the user is known to be
        // safe to load and logged in, but check just in case.
        if ( !$user->isSafeToLoad() ) {
            return null;
        }
 
        if ( !$this->mUserVariant ) {
            $services = MediaWikiServices::getInstance();
            if ( $user->isRegistered() ) {
                // Get language variant preference from logged in users
                if (
                    $this->getMainCode() ===
                    $services->getContentLanguageCode()->toString()
                ) {
                    $optionName = 'variant';
                } else {
                    $optionName = 'variant-' . $this->getMainCode();
                }
            } else {
                // figure out user lang without constructing wgLang to avoid
                // infinite recursion
                $optionName = 'language';
            }
            $ret = $services->getUserOptionsLookup()->getOption( $user, $optionName );
 
            $this->mUserVariant = $this->validateVariant( $ret );
        }
 
        return $this->mUserVariant;
    }
 
    protected function getHeaderVariant() {
        if ( $this->mHeaderVariant ) {
            return $this->mHeaderVariant;
        }
 
        $request = RequestContext::getMain()->getRequest();
        // See if some supported language variant is set in the
        // HTTP header.
        $languages = array_keys( $request->getAcceptLang() );
        if ( !$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->getStaticDefaultVariant()
            ) {
                $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;
    }
 
    public function autoConvert( $text, $toVariant = false ) {
        $this->loadTables();
 
        if ( !$toVariant ) {
            $toVariant = $this->getPreferredVariant();
            if ( !$toVariant ) {
                return $text;
            }
        }
 
        if ( $this->guessVariant( $text, $toVariant ) ) {
            return $text;
        }
        static $reg;
        if ( $reg === null ) {
            $marker = '|' . Parser::MARKER_PREFIX . '[^\x7f]++\x7f';
 
            // this one is needed when the text is inside an HTML markup
            $htmlfix = '|<[^>\004]++(?=\004$)|^[^<>]*+>';
 
            // Optimize for the common case where these tags have
            // few or no children. Thus try and possessively get as much as
            // possible, and only engage in backtracking when we hit a '<'.
 
            // disable convert to variants between <code> tags
            $codefix = '<code>[^<]*+(?:(?:(?!<\/code>).)[^<]*+)*+<\/code>|';
            // disable conversion of <script> tags
            $scriptfix = '<script[^>]*+>[^<]*+(?:(?:(?!<\/script>).)[^<]*+)*+<\/script>|';
            // disable conversion of <pre> tags
            $prefix = '<pre[^>]*+>[^<]*+(?:(?:(?!<\/pre>).)[^<]*+)*+<\/pre>|';
            // disable conversion of <math> tags
            $mathfix = '<math[^>]*+>[^<]*+(?:(?:(?!<\/math>).)[^<]*+)*+<\/math>|';
            // disable conversion of <svg> tags
            $svgfix = '<svg[^>]*+>[^<]*+(?:(?:(?!<\/svg>).)[^<]*+)*+<\/svg>|';
            // The "|.*+)" at the end, is in case we missed some part of html syntax,
            // we will fail securely (hopefully) by matching the rest of the string.
            $htmlFullTag = '<(?:[^>=]*+(?>[^>=]*+=\s*+(?:"[^"]*"|\'[^\']*\'|[^\'">\s]*+))*+[^>=]*+>|.*+)|';
 
            $reg = '/' . $codefix . $scriptfix . $prefix . $mathfix . $svgfix .
                $htmlFullTag .
                '&[a-zA-Z#][a-z0-9]++;' . $marker . $htmlfix . '|\004$/s';
        }
        $startPos = 0;
        $sourceBlob = '';
        $literalBlob = '';
 
        // Guard against delimiter nulls in the input
        // (should never happen: see T159174)
        $text = str_replace( "\000", '', $text );
        $text = str_replace( "\004", '', $text );
 
        $markupMatches = null;
        $elementMatches = null;
 
        // We add a marker (\004) at the end of text, to ensure we always match the
        // entire text (Otherwise, pcre.backtrack_limit might cause silent failure)
        $textWithMarker = $text . "\004";
        while ( $startPos < strlen( $text ) ) {
            if ( preg_match( $reg, $textWithMarker, $markupMatches, PREG_OFFSET_CAPTURE, $startPos ) ) {
                $elementPos = $markupMatches[0][1];
                $element = $markupMatches[0][0];
                if ( $element === "\004" ) {
                    // We hit the end.
                    $elementPos = strlen( $text );
                    $element = '';
                } elseif ( substr( $element, -1 ) === "\004" ) {
                    // This can sometimes happen if we have
                    // unclosed html tags. For example,
                    // when converting a title attribute
                    // during a recursive call that contains
                    // a &lt; e.g. <div title="&lt;">.
                    $element = substr( $element, 0, -1 );
                }
            } else {
                // If we hit here, then Language Converter could be tricked
                // into doing an XSS, so we refuse to translate.
                // If expected input manages to reach this code path,
                // we should consider it a bug.
                $log = LoggerFactory::getInstance( 'languageconverter' );
                $log->error( "Hit pcre.backtrack_limit in " . __METHOD__
                    . ". Disabling language conversion for this page.",
                    [
                        "method" => __METHOD__,
                        "variant" => $toVariant,
                        "startOfText" => substr( $text, 0, 500 )
                    ]
                );
                return $text;
            }
            // 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 )
            ) {
                // FIXME, this decodes entities, so if you have something
                // like <div title="foo&lt;bar"> the bar won't get
                // translated since after entity decoding it looks like
                // unclosed html and we call this method recursively
                // on attributes.
                $attrs = Sanitizer::decodeTagAttributes( $elementMatches[2] );
                // Ensure self-closing tags stay self-closing.
                $close = substr( $elementMatches[2], -1 ) === '/' ? ' /' : '';
                $changed = false;
                foreach ( [ 'title', 'alt' ] as $attrName ) {
                    if ( !isset( $attrs[$attrName] ) ) {
                        continue;
                    }
                    $attr = $attrs[$attrName];
                    // Don't convert URLs
                    if ( !str_contains( $attr, '://' ) ) {
                        $attr = $this->recursiveConvertTopLevel( $attr, $toVariant );
                    }
 
                    if ( $attr !== $attrs[$attrName] ) {
                        $attrs[$attrName] = $attr;
                        $changed = true;
                    }
                }
                if ( $changed ) {
                    // @phan-suppress-next-line SecurityCheck-DoubleEscaped Explained above with decodeTagAttributes
                    $element = $elementMatches[1] . Html::expandAttributes( $attrs ) .
                        $close . $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;
    }
 
    public function translate( $text, $variant ) {
        // If $text is empty or only includes spaces, do nothing
        // Otherwise translate it
        if ( trim( $text ) ) {
            $this->loadTables();
            // (T337427) Debugging / note error state if mTables not initialised
            if ( !$this->mTables[$variant] ) {
                $log = LoggerFactory::getInstance( 'languageconverter' );
                $log->error( "Tables not initialised for variant in " . __METHOD__
                    . ". No language conversion made for this string.",
                    [
                        "method" => __METHOD__,
                        "variant" => $variant,
                        "startOfText" => substr( $text, 0, 500 )
                    ]
                );
                return $text;
            }
            $text = $this->mTables[$variant]->replace( $text );
        }
        return $text;
    }
 
    protected function translateWithoutRomanNumbers( $text, $variant ) {
        $breaks = '[^\w\x80-\xff]';
 
        // regexp for roman numbers
        // Lookahead assertion ensures $roman doesn't match the empty string
        $roman = '(?=[MDCLXVI])M{0,4}(C[DM]|D?C{0,3})(X[LC]|L?X{0,3})(I[VX]|V?I{0,3})';
 
        $reg = '/^' . $roman . '$|^' . $roman . $breaks . '|' . $breaks
            . $roman . '$|' . $breaks . $roman . $breaks . '/';
 
        $matches = preg_split( $reg, $text, -1, PREG_SPLIT_OFFSET_CAPTURE );
 
        $m = array_shift( $matches );
        $this->loadTables();
        if ( !isset( $this->mTables[$variant] ) ) {
            throw new RuntimeException( "Broken variant table: "
                . implode( ',', array_keys( $this->mTables ) ) );
        }
        $ret = $this->mTables[$variant]->replace( $m[0] );
        $mstart = (int)$m[1] + strlen( $m[0] );
        foreach ( $matches as $m ) {
            $ret .= substr( $text, $mstart, (int)$m[1] - $mstart );
            $ret .= $this->translate( $m[0], $variant );
            $mstart = (int)$m[1] + strlen( $m[0] );
        }
 
        return $ret;
    }
 
    public function autoConvertToAllVariants( $text ) {
        $this->loadTables();
 
        $ret = [];
        foreach ( $this->getVariants() as $variant ) {
            $ret[$variant] = $this->translate( $text, $variant );
        }
 
        return $ret;
    }
 
    public function applyManualConv( ConverterRule $convRule ) {
        // Use syntax -{T|zh-cn:TitleCN; zh-tw:TitleTw}- to custom
        // title conversion.
        // T26072: $mConvRuleTitle was overwritten by other manual
        // rule(s) not for title, this breaks the title conversion.
        $newConvRuleTitle = $convRule->getTitleValue();
        if ( $newConvRuleTitle !== null ) {
            // 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 ) {
            $v = $this->validateVariant( $variant );
            if ( !$v ) {
                continue;
            }
 
            if ( $action == 'add' ) {
                // More efficient than array_merge(), about 2.5 times.
                foreach ( $pair as $from => $to ) {
                    $this->mTables[$v]->setPair( $from, $to );
                }
            } elseif ( $action == 'remove' ) {
                $this->mTables[$v]->removeArray( $pair );
            }
        }
    }
 
    public function convertSplitTitle( $title, ?string $variant = null ) {
        $variant ??= $this->getPreferredVariant();
 
        $index = $title->getNamespace();
        $nsText = $this->convertNamespace( $index, $variant );
 
        $name = str_replace( '_', ' ', $title->getDBKey() );
        $mainText = $this->translate( $name, $variant );
 
        return [ $nsText, ':', $mainText ];
    }
 
    public function convertTitle( $title ) {
        [ $nsText, $nsSeparator, $mainText ] = $this->convertSplitTitle( $title );
        return $nsText !== '' ?
            $nsText . $nsSeparator . $mainText :
            $mainText;
    }
 
    public function convertNamespace( $index, $variant = null ) {
        if ( $index === NS_MAIN ) {
            return '';
        }
 
        $variant ??= $this->getPreferredVariant();
 
        $cache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
        $key = $cache->makeKey( 'languageconverter', 'namespace-text', $index, $variant );
        return $cache->getWithSetCallback(
            $key,
            BagOStuff::TTL_MINUTE,
            function () use ( $index, $variant ) {
                return $this->computeNsVariantText( $index, $variant );
            }
        );
    }
 
    private function computeNsVariantText( int $index, string $variant ): string {
        $nsVariantText = false;
 
        // Check if a message for this namespace exists. Note that this would follow
        // the fallback chain, and the site's content language as the last resort.
        $nsConvMsg = wfMessage( 'conversion-ns' . $index )->inLanguage( $variant );
        if ( $nsConvMsg->exists() ) {
            $nsVariantText = $nsConvMsg->plain();
        }
 
        if ( $nsVariantText === false ) {
            // No message exists, retrieve it from the target variant's namespace names.
            $langObj = MediaWikiServices::getInstance()
                ->getLanguageFactory()
                ->getLanguage( $variant );
            $nsVariantText = $langObj->getFormattedNsText( $index );
        }
        return $nsVariantText;
    }
 
    public function convert( $text ) {
        $variant = $this->getPreferredVariant();
        return $this->convertTo( $text, $variant );
    }
 
    public function convertTo( $text, $variant, bool $clearState = true ) {
        $languageConverterFactory = MediaWikiServices::getInstance()->getLanguageConverterFactory();
        if ( $languageConverterFactory->isConversionDisabled() ) {
            return $text;
        }
        // Reset converter state for a new converter run.
        if ( $clearState ) {
            $this->mConvRuleTitle = false;
        }
        return $this->recursiveConvertTopLevel( $text, $variant );
    }
 
    protected function recursiveConvertTopLevel( $text, $variant, $depth = 0 ) {
        $startPos = 0;
        $out = '';
        $length = strlen( $text );
        $shouldConvert = !$this->guessVariant( $text, $variant );
        if ( RequestContext::getMain()->getRequest()->getFuzzyBool( 'nolcguess', false ) ) {
            $shouldConvert = true;
        }
        $continue = true;
 
        $noScript = '<script.*?>.*?<\/script>(*SKIP)(*FAIL)';
        $noStyle = '<style.*?>.*?<\/style>(*SKIP)(*FAIL)';
        $noMath = '<math.*?>.*?<\/math>(*SKIP)(*FAIL)';
        $noSvg = '<svg.*?>.*?<\/svg>(*SKIP)(*FAIL)';
        // phpcs:ignore Generic.Files.LineLength
        $noHtml = '<(?:[^>=]*+(?>[^>=]*+=\s*+(?:"[^"]*"|\'[^\']*\'|[^\'">\s]*+))*+[^>=]*+>|.*+)(*SKIP)(*FAIL)';
        while ( $startPos < $length && $continue ) {
            $continue = preg_match(
                // Only match "-{" outside the html.
                "/$noScript|$noStyle|$noMath|$noSvg|$noHtml|-\{/",
                $text,
                $m,
                PREG_OFFSET_CAPTURE,
                $startPos
            );
 
            if ( !$continue ) {
                // No more markup, append final segment
                $fragment = substr( $text, $startPos );
                $out .= $shouldConvert ? $this->autoConvert( $fragment, $variant ) : $fragment;
                return $out;
            }
 
            // Offset of the match of the regex pattern.
            $pos = $m[0][1];
 
            // Append initial segment
            $fragment = substr( $text, $startPos, $pos - $startPos );
            $out .= $shouldConvert ? $this->autoConvert( $fragment, $variant ) : $fragment;
            // -{ marker found, not in attribute
            // Advance position up to -{ marker.
            $startPos = $pos;
            // Do recursive conversion
            // Note: This passes $startPos by reference, and advances it.
            $out .= $this->recursiveConvertRule( $text, $variant, $startPos, $depth + 1 );
        }
        return $out;
    }
 
    protected function recursiveConvertRule( $text, $variant, &$startPos, $depth = 0 ) {
        // Quick check (no function calls)
        if ( $text[$startPos] !== '-' || $text[$startPos + 1] !== '{' ) {
            throw new InvalidArgumentException( __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;
                        break;
                    }
                    // Recursively parse another rule
                    $inner .= $this->recursiveConvertRule( $text, $variant, $startPos, $depth + 1 );
                    break;
                case '}-':
                    // Apply the rule
                    $startPos += 2;
                    $rule = new ConverterRule( $this );
                    $rule->parse( $inner, $variant );
                    $this->applyManualConv( $rule );
                    return $rule->getDisplay();
                default:
                    throw new UnexpectedValueException( __METHOD__ . ': invalid regex match' );
            }
        }
 
        // Unclosed rule
        if ( $startPos < $length ) {
            $inner .= substr( $text, $startPos );
        }
        $startPos = $length;
        return '-{' . $this->autoConvert( $inner, $variant );
    }
 
    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 ( $nt instanceof LinkTarget ) {
            $nt = Title::castFromLinkTarget( $nt );
            if ( $nt->exists() ) {
                return;
            }
        }
 
        if ( $nt instanceof PageIdentity && $nt->exists() ) {
            return;
        }
 
        $request = RequestContext::getMain()->getRequest();
 
        $isredir = $request->getText( 'redirect', 'yes' );
        $action = $request->getText( 'action' );
        if ( $action == 'edit' && $request->getBool( 'redlink' ) ) {
            $action = 'view';
        }
        $linkconvert = $request->getText( 'linkconvert', 'yes' );
        $disableLinkConversion =
            MediaWikiServices::getInstance()->getLanguageConverterFactory()
            ->isLinkConversionDisabled();
        $linkBatchFactory = MediaWikiServices::getInstance()->getLinkBatchFactory();
        $linkBatch = $linkBatchFactory->newLinkBatch();
 
        $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 ( $varnt !== null ) {
                    $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;
            }
        }
    }
 
    public function getExtraHashOptions() {
        $variant = $this->getPreferredVariant();
 
        return '!' . $variant;
    }
 
    public function guessVariant( $text, $variant ) {
        return false;
    }
 
    abstract protected function loadDefaultTables(): array;
 
    protected function loadTables( $fromCache = true ) {
        $services = MediaWikiServices::getInstance();
        $languageConverterCacheType = $services
            ->getMainConfig()->get( MainConfigNames::LanguageConverterCacheType );
 
        if ( $this->mTablesLoaded ) {
            return;
        }
 
        $cache = $services->getObjectCacheFactory()->getInstance( $languageConverterCacheType );
        $cacheKey = $cache->makeKey(
            'conversiontables', $this->getMainCode(),
            md5( implode( ',', $this->getVariants() ) ), self::CACHE_VERSION_KEY
        );
        if ( !$fromCache ) {
            $cache->delete( $cacheKey );
        }
        $this->mTables = $cache->getWithSetCallback( $cacheKey, $cache::TTL_HOUR * 12, function () {
            // We will first load the default tables
            // then update them using things in MediaWiki:Conversiontable/*
            $tables = $this->loadDefaultTables();
            foreach ( $this->getVariants() as $var ) {
                $cached = $this->parseCachedTable( $var );
                $tables[$var]->mergeArray( $cached );
            }
 
            $this->postLoadTables( $tables );
            return $tables;
        } );
        $this->mTablesLoaded = true;
    }
 
    protected function postLoadTables( &$tables ) {
    }
 
    private function reloadTables() {
        if ( $this->mTables ) {
            $this->mTables = [];
        }
 
        $this->mTablesLoaded = false;
        $this->loadTables( false );
    }
 
    private 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 === '' ) {
            $messageCache = MediaWikiServices::getInstance()->getMessageCache();
            $txt = $messageCache->getMsgFromNamespace( $key, $code );
        } else {
            $txt = false;
            $title = Title::makeTitleSafe( NS_MEDIAWIKI, $key );
            if ( $title && $title->exists() ) {
                $revision = MediaWikiServices::getInstance()
                    ->getRevisionLookup()
                    ->getRevisionByTitle( $title );
                if ( $revision ) {
                    $model = $revision->getSlot(
                        SlotRecord::MAIN,
                        RevisionRecord::RAW
                    )->getModel();
                    if ( $model == CONTENT_MODEL_WIKITEXT ) {
                        // @phan-suppress-next-line PhanUndeclaredMethod
                        $txt = $revision->getContent(
                            SlotRecord::MAIN,
                            RevisionRecord::RAW
                        )->getText();
                    }
 
                    // @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 trailing 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;
            }
        }
        return $ret;
    }
 
    public function markNoConversion( $text, $noParse = false ) {
        # don't mark if already marked
        if ( str_contains( $text, '-{' ) || str_contains( $text, '}-' ) ) {
            return $text;
        }
 
        return "-{R|$text}-";
    }
 
    public function convertCategoryKey( $key ) {
        return $key;
    }
 
    public function updateConversionTable( PageIdentity $page ) {
        if ( $page->getNamespace() === NS_MEDIAWIKI ) {
            $t = explode( '/', $page->getDBkey(), 3 );
            $c = count( $t );
            if ( $c > 1 && $t[0] == 'Conversiontable' && $this->validateVariant( $t[1] ) ) {
                $this->reloadTables();
            }
        }
    }
 
    public function getVarSeparatorPattern() {
        if ( $this->mVarSeparatorPattern === null ) {
            // varsep_pattern for preg_split:
            // The text should be split by ";" only if a valid variant
            // name exists 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] => ''
            //  ]
            $expandedVariants = [];
            foreach ( $this->getVariants() as $variant ) {
                $expandedVariants[ $variant ] = 1;
                // Accept standard BCP 47 names for variants as well.
                $expandedVariants[ LanguageCode::bcp47( $variant ) ] = 1;
            }
            // Accept old deprecated names for variants
            foreach ( LanguageCode::getDeprecatedCodeMapping() as $old => $new ) {
                if ( isset( $expandedVariants[ $new ] ) ) {
                    $expandedVariants[ $old ] = 1;
                }
            }
            $expandedVariants = implode( '|', array_keys( $expandedVariants ) );
 
            $pat = '/;\s*(?=';
            // zh-hans:xxx;zh-hant:yyy
            $pat .= '(?:' . $expandedVariants . ')\s*:';
            // xxx=>zh-hans:yyy; xxx=>zh-hant:zzz
            $pat .= '|[^;]*?=>\s*(?:' . $expandedVariants . ')\s*:';
            $pat .= '|\s*$)/';
            $this->mVarSeparatorPattern = $pat;
        }
        return $this->mVarSeparatorPattern;
    }
 
    public function hasVariants() {
        return count( $this->getVariants() ) > 1;
    }
 
    public function hasVariant( $variant ) {
        return $variant && ( $variant === $this->validateVariant( $variant ) );
    }
 
    public function convertHtml( $text ) {
        // @phan-suppress-next-line SecurityCheck-DoubleEscaped convert() is documented to return html
        return htmlspecialchars( $this->convert( $text ) );
    }
}
 
class_alias( LanguageConverter::class, 'LanguageConverter' );