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<?php |
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namespace mindplay\middleman; |
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use InvalidArgumentException; |
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use LogicException; |
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use mindplay\readable; |
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use Psr\Http\Message\ResponseInterface; |
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use Psr\Http\Message\ServerRequestInterface; |
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use Psr\Http\Server\MiddlewareInterface; |
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use Psr\Http\Server\RequestHandlerInterface; |
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/** |
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* PSR-7 / PSR-15 middleware dispatcher |
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*/ |
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class Dispatcher implements MiddlewareInterface, RequestHandlerInterface |
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{ |
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/** |
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* @var callable middleware resolver |
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*/ |
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private $resolver; |
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/** |
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* @var mixed[] unresolved middleware stack |
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*/ |
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private $stack; |
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/** |
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* @param (callable|MiddlewareInterface)[] $stack middleware stack (with at least one middleware component) |
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* @param callable|null $resolver optional middleware resolver: |
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* function (string $name): MiddlewareInterface |
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* |
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* @throws InvalidArgumentException if an empty middleware stack was given |
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*/ |
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public function __construct($stack, callable $resolver = null) |
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{ |
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if (count($stack) === 0) { |
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throw new InvalidArgumentException("an empty middleware stack was given"); |
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} |
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$this->stack = $stack; |
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$this->resolver = $resolver; |
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} |
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/** |
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* Dispatches the middleware stack and returns the resulting `ResponseInterface`. |
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* |
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* @param ServerRequestInterface $request |
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* |
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* @return ResponseInterface |
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* |
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* @throws LogicException on unexpected result from any middleware on the stack |
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*/ |
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public function handle(ServerRequestInterface $request): ResponseInterface |
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{ |
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$resolved = $this->resolve(0); |
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return $resolved->handle($request); |
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} |
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/** |
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* @inheritdoc |
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*/ |
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public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface |
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{ |
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$this->stack[] = function (ServerRequestInterface $request) use ($handler) { |
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return $handler->handle($request); |
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}; |
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$response = $this->handle($request); |
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array_pop($this->stack); |
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return $response; |
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} |
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/** |
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* @param int $index middleware stack index |
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* |
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* @return RequestHandlerInterface |
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*/ |
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private function resolve($index): RequestHandlerInterface |
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{ |
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if (isset($this->stack[$index])) { |
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return new Delegate(function (ServerRequestInterface $request) use ($index) { |
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$middleware = $this->resolver |
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? call_user_func($this->resolver, $this->stack[$index]) |
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: $this->stack[$index]; // as-is |
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if ($middleware instanceof MiddlewareInterface) { |
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$result = $middleware->process($request, $this->resolve($index + 1)); |
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} else if (is_callable($middleware)) { |
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$result = $middleware($request, $this->resolve($index + 1)); |
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} else { |
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$given = readable::callback($middleware); |
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throw new LogicException("unsupported middleware type: {$given}"); |
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} |
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if (! $result instanceof ResponseInterface) { |
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$given = readable::value($result); |
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$source = readable::callback($middleware); |
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throw new LogicException("unexpected middleware result: {$given} returned by: {$source}"); |
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} |
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return $result; |
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}); |
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} |
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return new Delegate(function () { |
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throw new LogicException("unresolved request: middleware stack exhausted with no result"); |
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}); |
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} |
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} |
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