wikimedia/mediawiki-extensions-Wikibase

<?php

namespace Wikibase\Client\Usage;

use InvalidArgumentException;
use Wikibase\DataModel\Entity\EntityId;
use Wikibase\DataModel\Services\Lookup\LabelDescriptionLookupException;
use Wikibase\DataModel\Term\TermFallback;
use Wikibase\Lib\Store\FallbackLabelDescriptionLookup;
use Wikibase\Lib\TermLanguageFallbackChain;

/**
 * LanguageFallbackLabelDescriptionLookup decorator that records label usage in an UsageAccumulator.
 *
 * @see UsageAccumulator
 *
 * @license GPL-2.0-or-later
 * @author Marius Hoch
 */
class UsageTrackingLanguageFallbackLabelDescriptionLookup implements FallbackLabelDescriptionLookup {

    /**
     * @var FallbackLabelDescriptionLookup
     */
    private $labelDescriptionLookup;

    /**
     * @var UsageAccumulator
     */
    private $usageAccumulator;

    /**
     * @var TermLanguageFallbackChain
     */
    private $termLanguageFallbackChain;

    /**
     * @var bool
     */
    private $trackUsagesInAllLanguages;

    /**
     * @param FallbackLabelDescriptionLookup $labelDescriptionLookup
     * @param UsageAccumulator $usageAccumulator
     * @param TermLanguageFallbackChain $termLanguageFallbackChain
     * @param bool $trackUsagesInAllLanguages
     */
    public function __construct(
        FallbackLabelDescriptionLookup $labelDescriptionLookup,
        UsageAccumulator $usageAccumulator,
        TermLanguageFallbackChain $termLanguageFallbackChain,
        $trackUsagesInAllLanguages
    ) {
        if ( !is_bool( $trackUsagesInAllLanguages ) ) {
            throw new InvalidArgumentException( '$trackUsagesInAllLanguages must be a bool' );
        }

        $this->labelDescriptionLookup = $labelDescriptionLookup;
        $this->usageAccumulator = $usageAccumulator;
        $this->termLanguageFallbackChain = $termLanguageFallbackChain;
        $this->trackUsagesInAllLanguages = $trackUsagesInAllLanguages;
    }

    /**
     * @param EntityId $entityId
     *
     * @throws LabelDescriptionLookupException
     * @return TermFallback|null
     */
    public function getLabel( EntityId $entityId ) {
        $termFallback = $this->labelDescriptionLookup->getLabel( $entityId );

        foreach ( $this->getTouchedLanguages( $termFallback ) as $lang ) {
            $this->usageAccumulator->addLabelUsage( $entityId, $lang );
        }

        return $termFallback;
    }

    /**
     * @param EntityId $entityId
     *
     * @throws LabelDescriptionLookupException
     * @return TermFallback|null
     */
    public function getDescription( EntityId $entityId ) {
        $termFallback = $this->labelDescriptionLookup->getDescription( $entityId );

        foreach ( $this->getTouchedLanguages( $termFallback ) as $lang ) {
            $this->usageAccumulator->addDescriptionUsage( $entityId, $lang );
        }

        return $termFallback;
    }

    /**
     * Get the languages from the TermLanguageFallbackChain used to get a given TermFallback.
     *
     * @param TermFallback|null $termFallback
     *
     * @return string[]|null[]
     */
    private function getTouchedLanguages( TermFallback $termFallback = null ) {
        if ( $this->trackUsagesInAllLanguages ) {
            // On multi-lingual wikis where users can request pages in any language, we can not
            // optimize for one language fallback chain only. Since all possible language fallback
            // chains must cover all languages, we can simply track an "all languages" usage.
            return [ null ];
        }

        $fetchLanguages = $this->termLanguageFallbackChain->getFetchLanguageCodes();

        if ( $termFallback === null ) {
            // Nothing found: Record the full fallback chains as used.
            return $fetchLanguages;
        }

        // Found something: Find out which language it was originally in
        $languageUsed = $termFallback->getSourceLanguageCode();
        if ( !$languageUsed ) {
            $languageUsed = $termFallback->getActualLanguageCode();
        }

        // Record the relevant part of the fallback chain as used.
        return array_slice(
            $fetchLanguages,
            0,
            array_search( $languageUsed, $fetchLanguages ) + 1
        );
    }

}