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<?php |
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namespace JMGQ\AStar; |
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class AStar |
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{ |
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private DomainLogicInterface $domainLogic; |
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private NodeCollectionInterface $openList; |
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private NodeCollectionInterface $closedList; |
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public function __construct(DomainLogicInterface $domainLogic) |
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{ |
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$this->domainLogic = $domainLogic; |
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$this->openList = new NodeHashTable(); |
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$this->closedList = new NodeHashTable(); |
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} |
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/** |
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* @param mixed $start |
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* @param mixed $goal |
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* @return mixed[] |
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*/ |
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public function run(mixed $start, mixed $goal): iterable |
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{ |
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$startNode = new Node($start); |
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$goalNode = new Node($goal); |
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return $this->executeAlgorithm($startNode, $goalNode); |
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} |
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/** |
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* @param Node $start |
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* @param Node $goal |
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* @return mixed[] |
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*/ |
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private function executeAlgorithm(Node $start, Node $goal): iterable |
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{ |
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$path = []; |
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$this->clear(); |
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$start->setG(0); |
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$start->setH($this->calculateEstimatedCost($start, $goal)); |
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$this->openList->add($start); |
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while (!$this->openList->isEmpty()) { |
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/** @var Node $currentNode Cannot be null because the open list is not empty */ |
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$currentNode = $this->openList->extractBest(); |
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$this->closedList->add($currentNode); |
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if ($currentNode->getId() === $goal->getId()) { |
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$path = $this->generatePathFromStartNodeTo($currentNode); |
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break; |
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} |
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$successors = $this->getAdjacentNodesWithTentativeScore($currentNode, $goal); |
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foreach ($successors as $successor) { |
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if ($this->nodeAlreadyPresentInListWithBetterOrSameRealCost($successor, $this->openList)) { |
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continue; |
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} |
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if ($this->nodeAlreadyPresentInListWithBetterOrSameRealCost($successor, $this->closedList)) { |
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continue; |
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} |
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$successor->setParent($currentNode); |
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$this->closedList->remove($successor); |
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$this->openList->add($successor); |
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} |
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} |
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return $path; |
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} |
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/** |
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* Sets the algorithm to its initial state |
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*/ |
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private function clear(): void |
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{ |
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$this->openList->clear(); |
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$this->closedList->clear(); |
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} |
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/** |
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* @param Node $node |
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* @return Node[] |
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*/ |
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private function generateAdjacentNodes(Node $node): iterable |
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{ |
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$adjacentNodes = []; |
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$adjacentStates = $this->domainLogic->getAdjacentNodes($node->getState()); |
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foreach ($adjacentStates as $state) { |
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$adjacentNodes[] = new Node($state); |
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} |
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return $adjacentNodes; |
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} |
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private function calculateRealCost(Node $node, Node $adjacent): float | int |
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{ |
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$state = $node->getState(); |
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$adjacentState = $adjacent->getState(); |
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return $this->domainLogic->calculateRealCost($state, $adjacentState); |
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} |
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private function calculateEstimatedCost(Node $start, Node $end): float | int |
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{ |
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$startState = $start->getState(); |
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$endState = $end->getState(); |
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return $this->domainLogic->calculateEstimatedCost($startState, $endState); |
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} |
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/** |
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* @param Node $node |
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* @return mixed[] |
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*/ |
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private function generatePathFromStartNodeTo(Node $node): iterable |
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{ |
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$path = []; |
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$currentNode = $node; |
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while ($currentNode !== null) { |
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array_unshift($path, $currentNode->getState()); |
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$currentNode = $currentNode->getParent(); |
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} |
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return $path; |
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} |
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/** |
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* @param Node $node |
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* @param Node $goal |
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* @return Node[] |
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*/ |
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private function getAdjacentNodesWithTentativeScore(Node $node, Node $goal): iterable |
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{ |
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$nodes = $this->generateAdjacentNodes($node); |
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foreach ($nodes as $adjacentNode) { |
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$adjacentNode->setG($node->getG() + $this->calculateRealCost($node, $adjacentNode)); |
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$adjacentNode->setH($this->calculateEstimatedCost($adjacentNode, $goal)); |
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} |
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return $nodes; |
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} |
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private function nodeAlreadyPresentInListWithBetterOrSameRealCost( |
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Node $node, |
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NodeCollectionInterface $nodeList |
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): bool { |
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if ($nodeList->contains($node)) { |
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/** @var Node $nodeInList Cannot be null because the list contains it */ |
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$nodeInList = $nodeList->get($node->getId()); |
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if ($node->getG() >= $nodeInList->getG()) { |
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return true; |
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} |
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} |
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return false; |
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} |
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} |
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jmgq /
php-a-star
