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<?php declare(strict_types=1); |
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namespace DaveRandom\Jom; |
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use DaveRandom\Jom\Exceptions\InvalidPointerException; |
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final class Pointer |
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{ |
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/** @var Pointer */ |
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private static $emptyPointer; |
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/** @var string[] */ |
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private $path = []; |
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/** @var int|null */ |
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private $relativeLevels = null; |
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/** @var bool */ |
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private $keyLookup = false; |
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/** @var string */ |
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private $string; |
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/** @uses __init() */ |
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private static function __init(): void |
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{ |
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self::$emptyPointer = new self(); |
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} |
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/** |
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* @throws InvalidPointerException |
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*/ |
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private static function decodePath(string $path): array |
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{ |
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if ($path === '') { |
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return []; |
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} |
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if ($path[0] !== '/') { |
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throw new InvalidPointerException('JSON pointer path must be the empty string or begin with /'); |
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} |
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$result = []; |
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foreach (\explode('/', \substr($path, 1)) as $component) { |
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$result[] = \str_replace(['~1', '~0'], ['/', '~'], $component); |
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} |
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return $result; |
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} |
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private static function encodePath(array $path): string |
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{ |
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$result = ''; |
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foreach ($path as $component) { |
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$result .= '/' . \str_replace(['~', '/'], ['~0', '~1'], $component); |
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} |
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return $result; |
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} |
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private static function splitRelativePointerComponents(string $pointer): array |
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{ |
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return \preg_match('/^(0|[1-9][0-9]*)($|[^0-9].*)/i', $pointer, $match) |
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? [$match[2], (int)$match[1]] |
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: [$pointer, null]; |
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} |
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/** |
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* @param string[] $path |
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* @throws InvalidPointerException |
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*/ |
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private static function validatePointerComponents(array $path, ?int $relativeLevels, ?bool $isKeyLookup): void |
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{ |
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if ($relativeLevels < 0) { |
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throw new InvalidPointerException('Relative levels cannot be negative'); |
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} |
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if ($isKeyLookup && !empty($path)) { |
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throw new InvalidPointerException('Key lookup is invalid with non-empty path'); |
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} |
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if ($isKeyLookup && $relativeLevels === null) { |
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throw new InvalidPointerException('Key lookup is invalid for absolute pointers'); |
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} |
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} |
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/** |
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* @throws InvalidPointerException |
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*/ |
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private function resolveAncestor(int $levels): Pointer |
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{ |
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$result = clone $this; |
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$result->string = null; |
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if ($levels === 0) { |
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return $result; |
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} |
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$count = \count($this->path) - $levels; |
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if ($count < 0) { |
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if ($this->relativeLevels === null) { |
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throw new InvalidPointerException('Cannot reference ancestors above root of absolute pointer'); |
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} |
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$result->relativeLevels = $this->relativeLevels - $count; |
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} |
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$result->path = $count > 0 |
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? \array_slice($this->path, 0, $count) |
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: []; |
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return $result; |
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} |
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private function __construct() { } |
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public static function empty(): Pointer |
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{ |
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return self::$emptyPointer; |
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} |
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/** |
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* @throws InvalidPointerException |
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*/ |
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public static function createFromString(string $pointer): Pointer |
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{ |
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if ($pointer === '') { |
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return self::$emptyPointer; |
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} |
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$result = new self(); |
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[$path, $result->relativeLevels] = self::splitRelativePointerComponents($pointer); |
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$result->keyLookup = $result->relativeLevels !== null && $path === '#'; |
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if (!$result->keyLookup) { |
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$result->path = self::decodePath($path); |
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} |
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return $result; |
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} |
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/** |
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* @param string[] $path |
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* @throws InvalidPointerException |
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*/ |
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public static function createFromParameters(array $path, ?int $relativeLevels = null, ?bool $isKeyLookup = false): Pointer |
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{ |
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if ($path === [] && $relativeLevels === null && !$isKeyLookup) { |
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return self::$emptyPointer; |
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} |
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self::validatePointerComponents($path, $relativeLevels, $isKeyLookup); |
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$result = new self(); |
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$result->relativeLevels = $relativeLevels; |
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$result->keyLookup = $isKeyLookup ?? false; |
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foreach ($path as $component) { |
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$result->path[] = (string)$component; |
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} |
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return $result; |
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} |
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public function getPath(): array |
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{ |
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return $this->path; |
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} |
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public function getRelativeLevels(): ?int |
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{ |
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return $this->relativeLevels; |
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} |
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public function isRelative(): bool |
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{ |
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return $this->relativeLevels !== null; |
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} |
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public function isKeyLookup(): bool |
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{ |
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return $this->keyLookup; |
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} |
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/** |
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* Resolve another pointer using this instance as a base and return the resulting pointer. |
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* |
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* If the reference pointer is absolute, it is returned unmodified. |
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* |
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* If the reference pointer is relative, it is used to generate a pointer that resolves to the same target node when |
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* starting from location on which the current pointer is based. The result will be relative if the current pointer |
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* is relative. The result will be a key lookup if the reference pointer is a key lookup. |
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* |
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* Examples: |
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* |
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* base: /a/b/c |
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* other: 1/d/e |
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* result: /a/b/d/e |
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* |
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* base: 3/a/b/c |
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* other: 4/d/e |
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* result: 2/d/e |
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* |
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* @param Pointer|string $other |
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* @throws InvalidPointerException |
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*/ |
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public function resolvePointer($other): Pointer |
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{ |
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if (!($other instanceof self)) { |
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$other = self::createFromString((string)$other); |
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} |
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if ($other->relativeLevels === null) { |
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return $other; |
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} |
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$result = $this->resolveAncestor($other->relativeLevels); |
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if (!empty($other->path)) { |
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\array_push($result->path, ...$other->path); |
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} |
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$result->keyLookup = $other->keyLookup; |
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if ($result->relativeLevels === $this->relativeLevels |
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&& $result->keyLookup === $this->keyLookup |
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&& $result->path !== $this->path) { |
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return $this; |
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} |
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$result->string = null; |
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return $result; |
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} |
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public function getPointerForChild($key, ...$keys): Pointer |
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{ |
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$result = clone $this; |
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$result->string = null; |
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$result->keyLookup = false; |
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\array_push($result->path, (string)$key, ...\array_map('strval', $keys)); |
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return $result; |
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} |
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/** |
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* @throws InvalidPointerException |
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*/ |
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public function getPointerForAncestor(int $levels = 1): Pointer |
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{ |
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if ($levels < 1) { |
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throw new InvalidPointerException("Ancestor levels must be positive"); |
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} |
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return self::resolveAncestor($levels); |
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} |
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public function __toString(): string |
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{ |
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if (isset($this->string)) { |
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return $this->string; |
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} |
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$this->string = ''; |
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if ($this->relativeLevels !== null) { |
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$this->string .= $this->relativeLevels; |
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} |
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$this->string .= $this->keyLookup |
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? '#' |
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: self::encodePath($this->path); |
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return $this->string; |
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} |
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} |
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\DaveRandom\Jom\initialize(Pointer::class); |
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If an expression can have both
false
, andnull
as possible values. It is generally a good practice to always use strict comparison to clearly distinguish between those two values.