wikimedia/mediawiki-core

<?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
 */

namespace MediaWiki\Sparql;

use MediaWiki\Http\HttpRequestFactory;
use Wikimedia\AtEase\AtEase;

/**
 * Simple SPARQL client
 *
 * @author Stas Malyshev
 */
class SparqlClient {

    /**
     * Limit on how long can be the query to be sent by GET.
     */
    public const MAX_GET_SIZE = 2048;

    /**
     * User agent for HTTP requests.
     */
    private string $userAgent;

    /**
     * Query timeout (seconds)
     */
    private int $timeout = 30;

    /**
     * SPARQL endpoint URL
     */
    private string $endpoint;

    /**
     * Client options
     */
    private array $options = [];

    private HttpRequestFactory $requestFactory;

    /**
     * @param string $url SPARQL Endpoint
     * @param HttpRequestFactory $requestFactory
     */
    public function __construct( string $url, HttpRequestFactory $requestFactory ) {
        $this->endpoint = $url;
        $this->requestFactory = $requestFactory;
        $this->userAgent = $requestFactory->getUserAgent() . " SparqlClient";
    }

    /**
     * Set query timeout (in seconds)
     * @param int $timeout
     * @return $this
     */
    public function setTimeout( int $timeout ): SparqlClient {
        if ( $timeout >= 0 ) {
            $this->timeout = $timeout;
        }
        return $this;
    }

    /**
     * @param array $options
     * @return $this
     */
    public function setClientOptions( array $options ): SparqlClient {
        $this->options = $options;
        return $this;
    }

    /**
     * Get current user agent.
     * @return string
     */
    public function getUserAgent(): string {
        return $this->userAgent;
    }

    /**
     * Mote it is not recommended to completely override user agent for
     * most applications.
     * @see appendUserAgent() for recommended way of specifying user agent.
     *
     * @param string $agent
     */
    public function setUserAgent( string $agent ) {
        $this->userAgent = $agent;
    }

    /**
     * Append specific string to user agent.
     *
     * This is the recommended way of specifying the user agent
     * for specific applications of the SparqlClient inside MediaWiki
     * and extension code.
     *
     * @param string $agent
     */
    public function appendUserAgent( string $agent ) {
        $this->userAgent .= ' ' . $agent;
    }

    /**
     * Query SPARQL endpoint
     *
     * @param string $sparql query
     * @param bool $rawData Whether to return only values or full data objects
     *
     * @return array[] List of results, one row per array element
     *               Each row will contain fields indexed by variable name.
     * @throws SparqlException
     */
    public function query( string $sparql, bool $rawData = false ): array {
        if ( !$this->endpoint ) {
            throw new SparqlException( 'Endpoint URL can not be empty' );
        }
        $queryData = [ "query" => $sparql, "format" => "json" ];
        $options = array_merge( [ 'method' => 'GET' ], $this->options );

        if ( empty( $options['userAgent'] ) ) {
            $options['userAgent'] = $this->userAgent;
        }

        if ( $this->timeout >= 0 ) {
            // Blazegraph setting, see https://wiki.blazegraph.com/wiki/index.php/REST_API
            $queryData['maxQueryTimeMillis'] = $this->timeout * 1000;
            $options['timeout'] = $this->timeout;
        }

        if ( strlen( $sparql ) > self::MAX_GET_SIZE ) {
            // big requests go to POST
            $options['method'] = 'POST';
            $options['postData'] = 'query=' . urlencode( $sparql );
            unset( $queryData['query'] );
        }

        $url = wfAppendQuery( $this->endpoint, $queryData );
        $request = $this->requestFactory->create( $url, $options, __METHOD__ );

        $status = $request->execute();

        if ( !$status->isOK() ) {
            throw new SparqlException( 'HTTP error: ' . $status->getWikiText( false, false, 'en' ) );
        }
        $result = $request->getContent();
        AtEase::suppressWarnings();
        $data = json_decode( $result, true );
        AtEase::restoreWarnings();
        if ( $data === null || $data === false ) {
            throw new SparqlException( "HTTP request failed, response:\n" .
                substr( $result, 1024 ) );
        }

        return $this->extractData( $data, $rawData );
    }

    /**
     * Extract data from SPARQL response format.
     * The response must be in format described in:
     * https://www.w3.org/TR/sparql11-results-json/
     *
     * @param array $data SPARQL result
     * @param bool $rawData Whether to return only values or full data objects
     *
     * @return array[] List of results, one row per element.
     */
    private function extractData( array $data, bool $rawData = false ): array {
        $result = [];
        if ( $data && !empty( $data['results'] ) ) {
            $vars = $data['head']['vars'];
            $resrow = [];
            foreach ( $data['results']['bindings'] as $row ) {
                foreach ( $vars as $var ) {
                    if ( !isset( $row[$var] ) ) {
                        $resrow[$var] = null;
                        continue;
                    }
                    if ( $rawData ) {
                        $resrow[$var] = $row[$var];
                    } else {
                        $resrow[$var] = $row[$var]['value'];
                    }
                }
                $result[] = $resrow;
            }
        }
        return $result;
    }

}