LanguageFallback.php

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<?php
namespace MediaWiki\Languages;
 
use InvalidArgumentException;
use LocalisationCache;
use Wikimedia\Assert\Assert;
 
class LanguageFallback {
    public const MESSAGES = 0;
 
    public const STRICT = 1;
 
    private $siteLangCode;
 
    private $localisationCache;
 
    private $langNameUtils;
 
    private $fallbackCache = [];
 
    public function __construct(
        $siteLangCode,
        LocalisationCache $localisationCache,
        LanguageNameUtils $langNameUtils
    ) {
        $this->siteLangCode = $siteLangCode;
        $this->localisationCache = $localisationCache;
        $this->langNameUtils = $langNameUtils;
    }
 
    public function getFirst( $code ) {
        return $this->getAll( $code )[0] ?? null;
    }
 
    public function getAll( $code, $mode = self::MESSAGES ) {
        // XXX The LanguageNameUtils dependency is just because of this line, is it needed?
        // Especially because isValidBuiltInCode() is just a one-line regex anyway, maybe it should
        // actually be static?
        if ( $code === 'en' || !$this->langNameUtils->isValidBuiltInCode( $code ) ) {
            return [];
        }
        switch ( $mode ) {
            case self::MESSAGES:
                // For unknown languages, fallbackSequence returns an empty array. Hardcode fallback
                // to 'en' in that case, as English messages are always defined.
                $ret = $this->localisationCache->getItem( $code, 'fallbackSequence' ) ?: [ 'en' ];
                break;
 
            case self::STRICT:
                // Use this mode when you don't want to fall back to English unless explicitly
                // defined, for example when you have language-variant icons and an international
                // language-independent fallback.
                $ret = $this->localisationCache->getItem( $code, 'originalFallbackSequence' );
                break;
 
            default:
                throw new InvalidArgumentException( "Invalid fallback mode \"$mode\"" );
        }
 
        foreach ( $ret as $fallbackCode ) {
            Assert::postcondition( $this->langNameUtils->isValidBuiltInCode( $fallbackCode ),
                "Invalid fallback code '$fallbackCode' in fallback sequence for '$code'" );
        }
 
        return $ret;
    }
 
    public function getAllIncludingSiteLanguage( $code ) {
        // Usually, we will only store a tiny number of fallback chains, so we cache in a member.
        $cacheKey = "{$code}-{$this->siteLangCode}";
 
        if ( !array_key_exists( $cacheKey, $this->fallbackCache ) ) {
            $fallbacks = $this->getAll( $code );
 
            if ( $code === $this->siteLangCode ) {
                // Don't bother hitting the localisation cache a second time
                $siteFallbacks = [ $code ];
            } else {
                // Append the site's fallback chain, including the site language itself
                $siteFallbacks = $this->getAll( $this->siteLangCode );
                array_unshift( $siteFallbacks, $this->siteLangCode );
 
                // Eliminate any languages already included in the chain
                $siteFallbacks = array_diff( $siteFallbacks, $fallbacks );
            }
 
            $this->fallbackCache[$cacheKey] = [ $fallbacks, $siteFallbacks ];
        }
        return $this->fallbackCache[$cacheKey];
    }
}