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<?php |
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namespace Butler\Graphql; |
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use Amp\Deferred; |
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use Amp\Loop; |
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use Closure; |
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use ReflectionFunction; |
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class DataLoader |
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{ |
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private $loaders = []; |
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/** |
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* @param callable|Closure $batchLoadFunction |
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*/ |
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public function __invoke($batchLoadFunction, $defaultResolveValue = null) |
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{ |
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if (! $batchLoadFunction instanceof Closure) { |
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$batchLoadFunction = Closure::fromCallable($batchLoadFunction); |
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} |
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$identifier = $this->identifierForClosure($batchLoadFunction); |
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return $this->loaders[$identifier] = $this->loaders[$identifier] |
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?? $this->makeLoader($batchLoadFunction, $defaultResolveValue); |
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} |
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private function identifierForClosure(Closure $closure) |
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{ |
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$reflection = new ReflectionFunction($closure); |
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return $reflection->getFileName() . '@' . |
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$reflection->getStartLine() . '-' . $reflection->getEndLine(); |
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} |
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private function makeLoader(Closure $batchLoadFunction, $defaultResolveValue) |
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{ |
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return new class ($batchLoadFunction, $defaultResolveValue) |
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{ |
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private $batchLoadFunction; |
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private $defaultResolveValue; |
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private $deferredPromises; |
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private $needsResolving; |
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public function __construct(Closure $batchLoadFunction, $defaultResolveValue = null) |
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{ |
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$this->batchLoadFunction = $batchLoadFunction; |
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$this->defaultResolveValue = $defaultResolveValue; |
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$this->deferredPromises = []; |
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$this->needsResolving = false; |
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} |
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public function load($key) |
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{ |
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$serializedKey = self::serializeKey($key); |
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[$deferred] = $this->deferredPromises[$serializedKey] |
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?? $this->deferredPromises[$serializedKey] = [new Deferred(), $key]; |
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$this->scheduleResolveIfNeeded(); |
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return $deferred->promise(); |
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} |
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private function scheduleResolveIfNeeded() |
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{ |
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if (! $this->needsResolving) { |
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Loop::defer(Closure::fromCallable([$this, 'resolve'])); |
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$this->needsResolving = true; |
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} |
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} |
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private function resolve() |
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{ |
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$indexedOriginalKeys = []; |
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foreach ($this->deferredPromises as [$_, $originalKey]) { |
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$indexedOriginalKeys[] = $originalKey; |
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} |
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$result = ($this->batchLoadFunction)($indexedOriginalKeys); |
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$currentIndex = 0; |
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foreach ($result as $key => $value) { |
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if ($key === $currentIndex) { |
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$key = $indexedOriginalKeys[$key] ?? $key; |
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} |
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$key = self::serializeKey($key); |
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if ([$deferred] = $this->deferredPromises[$key] ?? null) { |
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$deferred->resolve($value); |
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unset($this->deferredPromises[$key]); |
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} |
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++$currentIndex; |
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} |
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foreach ($this->deferredPromises as $key => [$deferredPromise]) { |
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$deferredPromise->resolve($this->defaultResolveValue); |
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} |
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$this->deferredPromises = []; |
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$this->needsResolving = false; |
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} |
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private static function serializeKey($key) |
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{ |
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if (is_object($key)) { |
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return spl_object_hash($key); |
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} elseif (is_array($key)) { |
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return md5(json_encode($key)); |
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} |
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return (string) $key; |
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} |
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}; |
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} |
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public function run(): void |
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{ |
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Loop::run(); |
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} |
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} |
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glesys /
butler-graphql
