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<?php
namespace SMW\MediaWiki;
use RuntimeException;
use Title;
/**
* @license GNU GPL v2+
* @since 2.1
*
* @author mwjames
*/
class DeepRedirectTargetResolver {
/**
* @var PageCreator
*/
private $pageCreator = null;
/**
* Track titles to prevent circular references caused by double redirects
* on the same title
*
* @var array
*/
private $recursiveResolverTracker = [];
/**
* @since 2.1
*
* @param PageCreator $pageCreator
*/
public function __construct( PageCreator $pageCreator ) {
$this->pageCreator = $pageCreator;
}
/**
* @since 2.1
*
* @param Title $title
*
* @return Title|null
* @throws RuntimeException
*/
public function findRedirectTargetFor( Title $title ) {
return $this->doResolveRedirectTarget( $title );
}
protected function isValidRedirectTarget( $title ) {
return $title instanceof Title && $title->isValidRedirectTarget();
}
protected function isRedirect( $title ) {
return $title instanceof Title && $title->isRedirect();
}
private function doResolveRedirectTarget( Title $title ) {
$this->addToResolverTracker( $title );
if ( $this->isCircularByKnownRedirectTarget( $title ) ) {
throw new RuntimeException( "Circular redirect for {$title->getPrefixedDBkey()} detected." );
}
if ( $this->isRedirect( $title ) ) {
$title = $this->pageCreator->createPage( $title )->getRedirectTarget();
if ( $title instanceof Title ) {
$title = $this->doResolveRedirectTarget( $title );
}
}
if ( $this->isValidRedirectTarget( $title ) ) {
return $title;
}
throw new RuntimeException( "Redirect target is unresolvable" );
}
private function addToResolverTracker( $title ) {
if ( !isset( $this->recursiveResolverTracker[$title->getPrefixedDBkey()] ) ) {
$this->recursiveResolverTracker[$title->getPrefixedDBkey()] = 0;
}
return $this->recursiveResolverTracker[$title->getPrefixedDBkey()]++;
}
private function isCircularByKnownRedirectTarget( $title ) {
return isset( $this->recursiveResolverTracker[$title->getPrefixedDBkey()] ) && $this->recursiveResolverTracker[$title->getPrefixedDBkey()] > 1;
}
}
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