wikimedia/mediawiki-extensions-Wikibase

<?php

namespace Wikibase\Repo\Rdf;

use InvalidArgumentException;
use Wikibase\DataModel\Entity\EntityDocument;
use Wikibase\DataModel\Entity\EntityId;
use Wikibase\DataModel\Statement\Statement;
use Wikibase\DataModel\Statement\StatementList;
use Wikibase\DataModel\Statement\StatementListProvider;
use Wikimedia\Purtle\RdfWriter;

/**
 * "Truthy" RDF mapping for wikibase statements, directly mapping properties to "best" values
 * without modelling statements as identifiable objects. "Best" statements per property are
 * statements that have the best non-deprecated rank.
 *
 * This simple property to value mapping excludes deprecated and non-"best" statements, ranks,
 * qualifiers, and references. This allows for a much simpler, much easier to query RDF structure
 * that allows searching for values similar to what would have been shown in infoboxes via Lua.
 *
 * If more information is needed, use FullStatementRdfBuilder instead.
 *
 * @see FullStatementRdfBuilder
 *
 * @license GPL-2.0-or-later
 * @author Daniel Kinzler
 * @author Stas Malyshev
 */
class TruthyStatementRdfBuilder implements EntityRdfBuilder {

    /**
     * @var RdfVocabulary
     */
    private $vocabulary;

    /**
     * @var RdfWriter
     */
    private $writer;

    /**
     * @var SnakRdfBuilder
     */
    private $snakBuilder;

    public function __construct( RdfVocabulary $vocabulary, RdfWriter $writer, SnakRdfBuilder $snakBuilder ) {
        $this->vocabulary = $vocabulary;
        $this->writer = $writer;
        $this->snakBuilder = $snakBuilder;
    }

    /**
     * Adds Statements to the RDF graph.
     *
     * @param EntityId $entityId
     * @param StatementList $statementList
     */
    public function addStatements( EntityId $entityId, StatementList $statementList ) {
        // FIXME: getBestStatementPerProperty() uis expensive, share the result with FullStatementRdfBuilder!
        foreach ( $statementList->getPropertyIds() as $propertyId ) {
            foreach ( $statementList->getByPropertyId( $propertyId )->getBestStatements() as $statement ) {
                $this->addMainSnak( $entityId, $statement );
            }
        }
    }

    /**
     * Adds the given Statement's main Snak to the RDF graph.
     *
     * @todo share more of this code with FullStatementRdfBuilder
     *
     * @param EntityId $entityId
     * @param Statement $statement
     *
     * @throws InvalidArgumentException
     */
    private function addMainSnak( EntityId $entityId, Statement $statement ) {
        $snak = $statement->getMainSnak();

        $entityLName = $this->vocabulary->getEntityLName( $entityId );
        $entityRepoName = $this->vocabulary->getEntityRepositoryName( $entityId );

        $snakNamespace = $this->vocabulary->statementNamespaceNames[$entityRepoName][RdfVocabulary::NS_VALUE];

        $this->writer->about( $this->vocabulary->entityNamespaceNames[$entityRepoName], $entityLName );

        $propertyRepoName = $this->vocabulary->getEntityRepositoryName( $snak->getPropertyId() );
        $this->snakBuilder->addSnak(
            $this->writer,
            $snakNamespace,
            $snak,
            $this->vocabulary->propertyNamespaceNames[$propertyRepoName][RdfVocabulary::NSP_DIRECT_CLAIM],
            $this->vocabulary->getStatementLName( $statement )
        );
    }

    /**
     * Add truthy statements for the given entity to the RDF graph.
     *
     * @param EntityDocument $entity the entity to output.
     */
    public function addEntity( EntityDocument $entity ) {
        $entityId = $entity->getId();

        if ( $entity instanceof StatementListProvider ) {
            $this->addStatements( $entityId, $entity->getStatements() );
        }
    }

}