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<?php
namespace SMW\SPARQLStore\QueryEngine\DescriptionInterpreters;
use SMW\Query\Language\Conjunction;
use SMW\Query\Language\Description;
use SMW\SPARQLStore\QueryEngine\Condition\FalseCondition;
use SMW\SPARQLStore\QueryEngine\Condition\FilterCondition;
use SMW\SPARQLStore\QueryEngine\Condition\SingletonCondition;
use SMW\SPARQLStore\QueryEngine\Condition\TrueCondition;
use SMW\SPARQLStore\QueryEngine\Condition\WhereCondition;
use SMW\SPARQLStore\QueryEngine\ConditionBuilder;
use SMW\SPARQLStore\QueryEngine\DescriptionInterpreter;
use SMWExpElement as ExpElement;
use SMWExpNsResource as ExpNsResource;
use SMWExporter as Exporter;
use SMWTurtleSerializer as TurtleSerializer;
/**
* @license GNU GPL v2+
* @since 2.1
*
* @author Markus Krötzsch
* @author mwjames
*/
class ConjunctionInterpreter implements DescriptionInterpreter {
/**
* @var ConditionBuilder
*/
private $conditionBuilder;
/**
* @var Exporter
*/
private $exporter;
/**
* @since 2.1
*
* @param ConditionBuilder|null $conditionBuilder
*/
public function __construct( ConditionBuilder $conditionBuilder = null ) {
$this->conditionBuilder = $conditionBuilder;
$this->exporter = Exporter::getInstance();
}
/**
* @since 2.2
*
* {@inheritDoc}
*/
public function canInterpretDescription( Description $description ) {
return $description instanceof Conjunction;
}
/**
* @since 2.2
*
* {@inheritDoc}
*/
public function interpretDescription( Description $description ) {
$joinVariable = $this->conditionBuilder->getJoinVariable();
$orderByProperty = $this->conditionBuilder->getOrderByProperty();
$subDescriptions = $description->getDescriptions();
$result = $this->doPreliminarySubDescriptionCheck(
$subDescriptions,
$joinVariable,
$orderByProperty
);
if ( $result !== null ) {
return $result;
}
$subConditionElements = $this->doResolveSubDescriptionsRecursively(
$subDescriptions,
$joinVariable
);
if ( $subConditionElements instanceof FalseCondition ) {
return $subConditionElements;
}
$result = $this->createConditionFromSubConditionElements( $subConditionElements );
$result->weakConditions = $subConditionElements->weakConditions;
$result->orderVariables = $subConditionElements->orderVariables;
$this->conditionBuilder->addOrderByDataForProperty(
$result,
$joinVariable,
$orderByProperty
);
return $result;
}
private function doPreliminarySubDescriptionCheck( $subDescriptions, $joinVariable, $orderByProperty ) {
$count = count( $subDescriptions );
// empty conjunction: true
if ( $count == 0 ) {
return $this->conditionBuilder->newTrueCondition(
$joinVariable,
$orderByProperty
);
}
// conjunction with one element
if ( $count == 1 ) {
$this->conditionBuilder->setJoinVariable( $joinVariable );
$this->conditionBuilder->setOrderByProperty( $orderByProperty );
return $this->conditionBuilder->mapDescriptionToCondition(
reset( $subDescriptions )
);
}
return null;
}
private function doResolveSubDescriptionsRecursively( $subDescriptions, $joinVariable ) {
// Using a stdClass as data container for simpler handling in follow-up tasks
// and as the class is not exposed publicly we don't need to create
// an extra "real" class to manage its elements
$subConditionElements = new \stdClass;
$subConditionElements->condition = '';
$subConditionElements->filter = '';
$subConditionElements->singletonMatchElement = null;
$namespaces = $weakConditions = $orderVariables = [];
$singletonMatchElementName = '';
$hasSafeSubconditions = false;
foreach ( $subDescriptions as $subDescription ) {
$this->conditionBuilder->setJoinVariable( $joinVariable );
$this->conditionBuilder->setOrderByProperty( null );
$subCondition = $this->conditionBuilder->mapDescriptionToCondition(
$subDescription
);
if ( $subCondition instanceof FalseCondition ) {
return new FalseCondition();
} elseif ( $subCondition instanceof TrueCondition ) {
// ignore true conditions in a conjunction
} elseif ( $subCondition instanceof WhereCondition ) {
$subConditionElements->condition .= $subCondition->condition;
} elseif ( $subCondition instanceof FilterCondition ) {
$subConditionElements->filter .= ( $subConditionElements->filter ? ' && ' : '' ) . $subCondition->filter;
} elseif ( $subCondition instanceof SingletonCondition ) {
$matchElement = $subCondition->matchElement;
if ( $matchElement instanceof ExpElement ) {
$matchElementName = TurtleSerializer::getTurtleNameForExpElement( $matchElement );
} else {
$matchElementName = $matchElement;
}
if ( $matchElement instanceof ExpNsResource ) {
$namespaces[$matchElement->getNamespaceId()] = $matchElement->getNamespace();
}
if ( ( $subConditionElements->singletonMatchElement !== null ) &&
( $singletonMatchElementName !== $matchElementName ) ) {
return new FalseCondition();
}
$subConditionElements->condition .= $subCondition->condition;
$subConditionElements->singletonMatchElement = $subCondition->matchElement;
$singletonMatchElementName = $matchElementName;
}
$hasSafeSubconditions = $hasSafeSubconditions || $subCondition->isSafe();
$namespaces = array_merge( $namespaces, $subCondition->namespaces );
$weakConditions = array_merge( $weakConditions, $subCondition->weakConditions );
$orderVariables = array_merge( $orderVariables, $subCondition->orderVariables );
}
$subConditionElements->hasSafeSubconditions = $hasSafeSubconditions;
$subConditionElements->namespaces = $namespaces;
$subConditionElements->weakConditions = $weakConditions;
$subConditionElements->orderVariables = $orderVariables;
return $subConditionElements;
}
private function createConditionFromSubConditionElements( $subConditionElements ) {
if ( $subConditionElements->singletonMatchElement instanceof ExpElement ) {
return $this->createSingletonCondition( $subConditionElements );
}
if ( $subConditionElements->condition === '' ) {
return $this->createFilterCondition( $subConditionElements );
}
return $this->createWhereCondition( $subConditionElements );
}
private function createSingletonCondition( $subConditionElements ) {
if ( $subConditionElements->filter !== '' ) {
$subConditionElements->condition .= "FILTER( $subConditionElements->filter )";
}
$result = new SingletonCondition(
$subConditionElements->singletonMatchElement,
$subConditionElements->condition,
$subConditionElements->hasSafeSubconditions,
$subConditionElements->namespaces
);
return $result;
}
private function createFilterCondition( $subConditionElements ) {
return new FilterCondition(
$subConditionElements->filter,
$subConditionElements->namespaces
);
}
private function createWhereCondition( $subConditionElements ) {
if ( $subConditionElements->filter !== '' ) {
$subConditionElements->condition .= "FILTER( $subConditionElements->filter )";
}
$result = new WhereCondition(
$subConditionElements->condition,
$subConditionElements->hasSafeSubconditions,
$subConditionElements->namespaces
);
return $result;
}
}
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