GraphStore.php

<?php

/**
 * EasyRdf
 *
 * LICENSE
 *
 * Copyright (c) 2009-2011 Nicholas J Humfrey.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author 'Nicholas J Humfrey" may be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * @package    EasyRdf
 * @copyright  Copyright (c) 2009-2011 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 * @version    $Id$
 */

/**
 * A class for fetching, saving and deleting graphs to a Graph Store.
 * Implementation of the SPARQL 1.1 Graph Store HTTP Protocol.
 *
 * @package    EasyRdf
 * @copyright  Copyright (c) 2009-2011 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 */
class EasyRdf_GraphStore {

  /** The address of the GraphStore endpoint */
  private $uri = null;
  private $parsedUri = null;

  /** Create a new SPARQL Graph Store client
   *
   * @param string $uri The address of the graph store endpoint
   */
  public function __construct($uri) {
    $this->uri = $uri;
    $this->parsedUri = new EasyRdf_ParsedUri($uri);
  }

  /** Get the URI of the graph store
   *
   * @return string The URI of the graph store
   */
  public function getUri() {
    return $this->uri;
  }

  /** Fetch a named graph from the graph store
   *
   * The URI can either be a full absolute URI or
   * a URI relative to the URI of the graph store.
   *
   * @param string $uriRef The URI of graph desired
   * @return object EasyRdf_Graph The graph requested
   */
  public function get($uriRef) {
    $graphUri = $this->parsedUri
      ->resolve($uriRef)
      ->toString();
    $dataUrl = $this
      ->urlForGraph($graphUri);
    $graph = new EasyRdf_Graph($graphUri);
    $graph
      ->load($dataUrl);
    return $graph;
  }

  /** Send some graph data to the graph store
   *
   * This method is used by insert() and replace()
   *
   * @ignore
   */
  protected function sendGraph($method, $graph, $uriRef, $format) {
    if (is_object($graph) and $graph instanceof EasyRdf_Graph) {
      if ($uriRef == null) {
        $uriRef = $graph
          ->getUri();
      }
      $data = $graph
        ->serialise($format);
    }
    else {
      $data = $graph;
    }
    $formatObj = EasyRdf_Format::getFormat($format);
    $mimeType = $formatObj
      ->getDefaultMimeType();
    $graphUri = $this->parsedUri
      ->resolve($uriRef)
      ->toString();
    $dataUrl = $this
      ->urlForGraph($graphUri);
    $client = EasyRdf_Http::getDefaultHttpClient();
    $client
      ->resetParameters(true);
    $client
      ->setUri($dataUrl);
    $client
      ->setMethod($method);
    $client
      ->setRawData($data);
    $client
      ->setHeaders('Content-Type', $mimeType);
    $client
      ->setHeaders('Content-Length', strlen($data));
    $response = $client
      ->request();
    if (!$response
      ->isSuccessful()) {
      throw new EasyRdf_Exception("HTTP request for {$dataUrl} failed: " . $response
        ->getMessage());
    }
    return $response;
  }

  /** Replace the contents of a graph in the graph store with new data
   *
   * The $graph parameter is the EasyRdf_Graph object to be sent to the
   * graph store. Alternatively it can be a string, already serialised.
   *
   * The URI can either be a full absolute URI or
   * a URI relative to the URI of the graph store.
   *
   * The $format parameter can be given to specify the serialisation
   * used to send the graph data to the graph store.
   *
   * @param object EasyRdfGraph $graph The URI of graph desired
   * @param string $uriRef The URI of graph to be replaced
   * @param string $format The format of the data to send to the graph store
   * @return object EasyRdf_Http_Response The response from the graph store
   */
  public function replace($graph, $uriRef = null, $format = 'ntriples') {
    return $this
      ->sendGraph('PUT', $graph, $uriRef, $format);
  }

  /** Add data to a graph in the graph store
   *
   * The $graph parameter is the EasyRdf_Graph object to be sent to the
   * graph store. Alternatively it can be a string, already serialised.
   *
   * The URI can either be a full absolute URI or
   * a URI relative to the URI of the graph store.
   *
   * The $format parameter can be given to specify the serialisation
   * used to send the graph data to the graph store.
   *
   * @param object EasyRdfGraph $graph The URI of graph desired
   * @param string $uriRef The URI of graph to be added to
   * @param string $format The format of the data to send to the graph store
   * @return object EasyRdf_Http_Response The response from the graph store
   */
  public function insert($graph, $uriRef = null, $format = 'ntriples') {
    return $this
      ->sendGraph('POST', $graph, $uriRef, $format);
  }

  /** Delete a graph from the graph store
   *
   * The URI can either be a full absolute URI or
   * a URI relative to the URI of the graph store.
   *
   * @param string $uriRef The URI of graph to be added to
   * @return object EasyRdf_Http_Response The response from the graph store
   */
  public function delete($uriRef) {
    $graphUri = $this->parsedUri
      ->resolve($uriRef)
      ->toString();
    $dataUrl = $this
      ->urlForGraph($graphUri);
    $client = EasyRdf_Http::getDefaultHttpClient();
    $client
      ->resetParameters(true);
    $client
      ->setUri($dataUrl);
    $client
      ->setMethod('DELETE');
    $response = $client
      ->request();
    if (!$response
      ->isSuccessful()) {
      throw new EasyRdf_Exception("HTTP request to delete {$dataUrl} failed: " . $response
        ->getMessage());
    }
    return $response;
  }

  /** Work out the full URL for a graph store request.
   *  by checking if if it is a direct or indirect request.
   *  @ignore
   */
  protected function urlForGraph($url) {
    if (strpos($url, $this->uri) === false) {
      $url = $this->uri . "?graph=" . urlencode($url);
    }
    return $url;
  }

  /** Magic method to return URI of the graph store when casted to string
   *
   * @return string The URI of the graph store
   */
  public function __toString() {
    return empty($this->uri) ? '' : $this->uri;
  }

}