spaces.php

aws/GuzzleHttp/Promise/Coroutine.php

@@ -0,0 +1,151 @@
+<?php
+namespace GuzzleHttp\Promise;
+
+use Exception;
+use Generator;
+use Throwable;
+
+/**
+ * Creates a promise that is resolved using a generator that yields values or
+ * promises (somewhat similar to C#'s async keyword).
+ *
+ * When called, the coroutine function will start an instance of the generator
+ * and returns a promise that is fulfilled with its final yielded value.
+ *
+ * Control is returned back to the generator when the yielded promise settles.
+ * This can lead to less verbose code when doing lots of sequential async calls
+ * with minimal processing in between.
+ *
+ *     use GuzzleHttp\Promise;
+ *
+ *     function createPromise($value) {
+ *         return new Promise\FulfilledPromise($value);
+ *     }
+ *
+ *     $promise = Promise\coroutine(function () {
+ *         $value = (yield createPromise('a'));
+ *         try {
+ *             $value = (yield createPromise($value . 'b'));
+ *         } catch (\Exception $e) {
+ *             // The promise was rejected.
+ *         }
+ *         yield $value . 'c';
+ *     });
+ *
+ *     // Outputs "abc"
+ *     $promise->then(function ($v) { echo $v; });
+ *
+ * @param callable $generatorFn Generator function to wrap into a promise.
+ *
+ * @return Promise
+ * @link https://github.com/petkaantonov/bluebird/blob/master/API.md#generators inspiration
+ */
+final class Coroutine implements PromiseInterface
+{
+    /**
+     * @var PromiseInterface|null
+     */
+    private $currentPromise;
+
+    /**
+     * @var Generator
+     */
+    private $generator;
+
+    /**
+     * @var Promise
+     */
+    private $result;
+
+    public function __construct(callable $generatorFn)
+    {
+        $this->generator = $generatorFn();
+        $this->result = new Promise(function () {
+            while (isset($this->currentPromise)) {
+                $this->currentPromise->wait();
+            }
+        });
+        $this->nextCoroutine($this->generator->current());
+    }
+
+    public function then(
+        callable $onFulfilled = null,
+        callable $onRejected = null
+    ) {
+        return $this->result->then($onFulfilled, $onRejected);
+    }
+
+    public function otherwise(callable $onRejected)
+    {
+        return $this->result->otherwise($onRejected);
+    }
+
+    public function wait($unwrap = true)
+    {
+        return $this->result->wait($unwrap);
+    }
+
+    public function getState()
+    {
+        return $this->result->getState();
+    }
+
+    public function resolve($value)
+    {
+        $this->result->resolve($value);
+    }
+
+    public function reject($reason)
+    {
+        $this->result->reject($reason);
+    }
+
+    public function cancel()
+    {
+        $this->currentPromise->cancel();
+        $this->result->cancel();
+    }
+
+    private function nextCoroutine($yielded)
+    {
+        $this->currentPromise = promise_for($yielded)
+            ->then([$this, '_handleSuccess'], [$this, '_handleFailure']);
+    }
+
+    /**
+     * @internal
+     */
+    public function _handleSuccess($value)
+    {
+        unset($this->currentPromise);
+        try {
+            $next = $this->generator->send($value);
+            if ($this->generator->valid()) {
+                $this->nextCoroutine($next);
+            } else {
+                $this->result->resolve($value);
+            }
+        } catch (Exception $exception) {
+            $this->result->reject($exception);
+        } catch (Throwable $throwable) {
+            $this->result->reject($throwable);
+        }
+    }
+
+    /**
+     * @internal
+     */
+    public function _handleFailure($reason)
+    {
+        unset($this->currentPromise);
+        try {
+            $nextYield = $this->generator->throw(exception_for($reason));
+            // The throw was caught, so keep iterating on the coroutine
+            $this->nextCoroutine($nextYield);
+        } catch (Exception $exception) {
+            $this->result->reject($exception);
+        } catch (Throwable $throwable) {
+            $this->result->reject($throwable);
+        }
+    }
+}