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<?php
namespace EasyRdf\Serialiser;
/**
* EasyRdf
*
* LICENSE
*
* Copyright (c) 2009-2020 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) 2009-2020 Nicholas J Humfrey
* @license https://www.opensource.org/licenses/bsd-license.php
*/
use EasyRdf\Exception;
use EasyRdf\Graph;
use EasyRdf\Serialiser;
use ML\JsonLD as LD;
/**
* Class to serialise an EasyRdf\Graph to JSON-LD
*
* @package EasyRdf
* @copyright Copyright (c) 2013 Alexey Zakhlestin
* @license https://www.opensource.org/licenses/bsd-license.php
*/
class JsonLd extends Serialiser
{
public function __construct()
{
if (!class_exists('\ML\JsonLD\JsonLD')) {
throw new \LogicException('Please install "ml/json-ld" dependency to use JSON-LD serialisation');
}
}
/**
* Serialise an EasyRdf\Graph into a JSON-LD document.
*
* @param Graph $graph An EasyRdf\Graph object.
* @param string $format The name of the format to convert to.
* @param array $options
*
* @return string The RDF in the new desired format.
* @throws Exception
*/
public function serialise(Graph $graph, $format, array $options = array())
{
parent::checkSerialiseParams($format);
if ($format != 'jsonld') {
throw new Exception(__CLASS__.' does not support: '.$format);
}
$ld_graph = new LD\Graph();
$nodes = array(); // cache for id-to-node association
foreach ($graph->toRdfPhp() as $resource => $properties) {
if (array_key_exists($resource, $nodes)) {
$node = $nodes[$resource];
} else {
$node = $ld_graph->createNode($resource);
$nodes[$resource] = $node;
}
foreach ($properties as $property => $values) {
foreach ($values as $value) {
if ($value['type'] == 'bnode' or $value['type'] == 'uri') {
if (array_key_exists($value['value'], $nodes)) {
$_value = $nodes[$value['value']];
} else {
$_value = $ld_graph->createNode($value['value']);
$nodes[$value['value']] = $_value;
}
} elseif ($value['type'] == 'literal') {
if (isset($value['lang'])) {
$_value = new LD\LanguageTaggedString($value['value'], $value['lang']);
} elseif (isset($value['datatype'])) {
$_value = new LD\TypedValue($value['value'], $value['datatype']);
} else {
$_value = $value['value'];
}
} else {
throw new Exception(
"Unable to serialise object to JSON-LD: ".$value['type']
);
}
if ($property == "http://www.w3.org/1999/02/22-rdf-syntax-ns#type") {
$node->addType($_value);
} else {
$node->addPropertyValue($property, $_value);
}
}
}
}
// OPTIONS
$use_native_types = !(isset($options['expand_native_types']) and $options['expand_native_types'] == true);
$should_compact = (isset($options['compact']) and $options['compact'] == true);
$should_frame = isset($options['frame']);
// expanded form
$data = $ld_graph->toJsonLd($use_native_types);
if ($should_frame) {
$data = LD\JsonLD::frame($data, $options['frame'], $options);
}
if ($should_compact) {
// compact form
$compact_context = isset($options['context']) ? $options['context'] : null;
$compact_options = array(
'useNativeTypes' => $use_native_types,
'base' => $graph->getUri()
);
$data = LD\JsonLD::compact($data, $compact_context, $compact_options);
}
return LD\JsonLD::toString($data);
}
}
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