*/ private array $elementNodes; /** * @no-named-arguments */ public function __construct(ElementNode ... $elementNodes) { $this->elementNodes = $elementNodes; } /** * @throws InvalidArgumentException */ public function pop(): self { $this->calculateNonEmptyElementsCount(); $popped = $this->elementNodes; array_pop($popped); return new self(...$popped); } public function append(ElementNode $element): self { return new self(...[...$this->elementNodes, $element]); } /** * @throws InvalidArgumentException */ public function current(): ElementNode { return $this->elementNodes[$this->calculateNonEmptyElementsCount() -1]; } public function parent(): ?ElementNode { $count = count($this->elementNodes); if ($count <= 1) { return null; } return $this->elementNodes[$count - 2]; } /** * @return list */ public function sequence(): array { return $this->elementNodes; } public function count(): int { return \count($this->elementNodes); } /** * @param non-negative-int $start * @param non-negative-int|null $length */ public function slice(int $start, ?int $length = null): self { return new self(...slice($this->elementNodes, $start, $length)); } /** * Replays every step in the sequence * * @return Generator */ public function replay(): Generator { $step = new self(); foreach ($this->elementNodes as $index => $node) { $step = $step->append($node); yield $index => $step; } } /** * @throws InvalidArgumentException */ private function calculateNonEmptyElementsCount(): int { $count = count($this->elementNodes); Assert::true($count > 0, 'The node sequence is empty. Can not fetch current item!'); return $count; } }