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<?php |
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namespace PSB\Core\Util\DependencyGraph; |
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use PSB\Core\Exception\DependencyGraphCycleException; |
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class DependencyGraph |
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{ |
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/** |
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* @var array |
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*/ |
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private $idToNode; |
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/** |
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* The actual graph maintained as an array of arrays (node id to successor ids). |
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* |
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* @var [][] |
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*/ |
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private $idDirectedGraph; |
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/** |
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* @var array |
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*/ |
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private $nodeMarks = []; |
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/** |
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* @var array |
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*/ |
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private $nodeTemporaryMarks = []; |
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/** |
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* @var array |
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*/ |
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private $sortedIdList = []; |
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/** |
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* @param array $idToNode The nodes indexed by id. |
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* @param array $idDirectedGraph The actual graph maintained as an array of arrays (node id to successor ids). |
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*/ |
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public function __construct(array $idToNode, array $idDirectedGraph) |
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{ |
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$this->idToNode = $idToNode; |
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$this->idDirectedGraph = $idDirectedGraph; |
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} |
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/** |
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* It uses Tarjan's algorithm for topological sorting. |
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* {@see https://en.wikipedia.org/wiki/Topological_sorting#Tarjan.27s_algorithm} |
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* |
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* @return array The sorted id to node list. |
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*/ |
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public function sort() |
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{ |
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foreach ($this->idDirectedGraph as $nodeId => $successorIds) { |
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if (!isset($this->nodeMarks[$nodeId])) { |
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$this->visit($nodeId); |
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} |
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} |
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$sortedIdList = array_reverse($this->sortedIdList); |
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$sortedNodeList = []; |
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foreach ($sortedIdList as $nodeId) { |
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$sortedNodeList[] = $this->idToNode[$nodeId]; |
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} |
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return $sortedNodeList; |
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} |
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/** |
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* @param string $nodeId |
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*/ |
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private function visit($nodeId) |
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{ |
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if (isset($this->nodeTemporaryMarks[$nodeId])) { |
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throw new DependencyGraphCycleException( |
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"Cyclic dependency detected in graph containing node with id '$nodeId'." |
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); |
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} |
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if (isset($this->nodeMarks[$nodeId])) { |
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return; |
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} |
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$this->nodeTemporaryMarks[$nodeId] = true; |
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foreach ($this->idDirectedGraph[$nodeId] as $successorId) { |
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$this->visit($successorId); |
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} |
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$this->nodeMarks[$nodeId] = true; |
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unset($this->nodeTemporaryMarks[$nodeId]); |
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$this->sortedIdList[] = $nodeId; |
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} |
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} |
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phpservicebus /
core
