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120 lines
3.7 KiB
120 lines
3.7 KiB
<?php |
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namespace Sabre\Event; |
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use Generator; |
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use Exception; |
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/** |
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* Turn asynchronous promise-based code into something that looks synchronous |
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* again, through the use of generators. |
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* |
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* Example without coroutines: |
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* |
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* $promise = $httpClient->request('GET', '/foo'); |
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* $promise->then(function($value) { |
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* |
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* return $httpClient->request('DELETE','/foo'); |
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* |
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* })->then(function($value) { |
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* |
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* return $httpClient->request('PUT', '/foo'); |
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* |
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* })->error(function($reason) { |
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* |
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* echo "Failed because: $reason\n"; |
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* |
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* }); |
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* |
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* Example with coroutines: |
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* |
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* coroutine(function() { |
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* |
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* try { |
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* yield $httpClient->request('GET', '/foo'); |
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* yield $httpClient->request('DELETE', /foo'); |
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* yield $httpClient->request('PUT', '/foo'); |
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* } catch(\Exception $reason) { |
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* echo "Failed because: $reason\n"; |
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* } |
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* |
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* }); |
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* |
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* @copyright Copyright (C) 2013-2015 fruux GmbH. All rights reserved. |
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* @author Evert Pot (http://evertpot.com/) |
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* @license http://sabre.io/license/ Modified BSD License |
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*/ |
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function coroutine(callable $gen) { |
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$generator = $gen(); |
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if (!$generator instanceof Generator) { |
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throw new \InvalidArgumentException('You must pass a generator function'); |
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} |
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// This is the value we're returning. |
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$promise = new Promise(); |
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$lastYieldResult = null; |
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/** |
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* So tempted to use the mythical y-combinator here, but it's not needed in |
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* PHP. |
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*/ |
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$advanceGenerator = function() use (&$advanceGenerator, $generator, $promise, &$lastYieldResult) { |
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while ($generator->valid()) { |
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$yieldedValue = $generator->current(); |
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if ($yieldedValue instanceof Promise) { |
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$yieldedValue->then( |
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function($value) use ($generator, &$advanceGenerator, &$lastYieldResult) { |
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$lastYieldResult = $value; |
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$generator->send($value); |
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$advanceGenerator(); |
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}, |
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function($reason) use ($generator, $advanceGenerator) { |
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if ($reason instanceof Exception) { |
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$generator->throw($reason); |
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} elseif (is_scalar($reason)) { |
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$generator->throw(new Exception($reason)); |
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} else { |
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$type = is_object($reason) ? get_class($reason) : gettype($reason); |
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$generator->throw(new Exception('Promise was rejected with reason of type: ' . $type)); |
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} |
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$advanceGenerator(); |
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} |
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)->error(function($reason) use ($promise) { |
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// This error handler would be called, if something in the |
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// generator throws an exception, and it's not caught |
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// locally. |
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$promise->reject($reason); |
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}); |
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// We need to break out of the loop, because $advanceGenerator |
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// will be called asynchronously when the promise has a result. |
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break; |
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} else { |
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// If the value was not a promise, we'll just let it pass through. |
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$lastYieldResult = $yieldedValue; |
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$generator->send($yieldedValue); |
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} |
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} |
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// If the generator is at the end, and we didn't run into an exception, |
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// we can fullfill the promise with the last thing that was yielded to |
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// us. |
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if (!$generator->valid() && $promise->state === Promise::PENDING) { |
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$promise->fulfill($lastYieldResult); |
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} |
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}; |
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try { |
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$advanceGenerator(); |
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} catch (Exception $e) { |
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$promise->reject($e); |
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} |
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return $promise; |
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}
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