add async wrapper

src/Common/Api/Operator.php

@@ -4,6 +4,7 @@
 
 use function GuzzleHttp\uri_template;
 use GuzzleHttp\ClientInterface;
+use GuzzleHttp\Promise\Promise;
 use OpenStack\Common\Resource\ResourceInterface;
 use OpenStack\Common\Transport\RequestSerializer;
 use Psr\Http\Message\ResponseInterface;
@@ -126,4 +127,38 @@ protected function getHttpBaseUrl()
     {
         return $this->client->getConfig('base_url');
     }
+
+    /**
+     * Magic method which intercepts async calls, finds the sequential version, and wraps it in a
+     * {@see Promise} object. In order for this to happen, the called methods need to be in the
+     * following format: `createAsync`, where `create` is the sequential method being wrapped.
+     *
+     * @param $methodName The name of the method being invoked.
+     * @param $args       The arguments to be passed to the sequential method.
+     *
+     * @return Promise
+     */
+    public function __call($methodName, $args)
+    {
+        if (substr($methodName, -5) === 'Async') {
+            $realMethod = substr($methodName, 0, -5);
+            if (!method_exists($this, $realMethod)) {
+                throw new \InvalidArgumentException(sprintf(
+                    '%s is not a defined method on %s', $realMethod, get_class($this)
+                ));
+            }
+
+            $promise = new Promise(
+                function () use (&$promise, $realMethod, $args) {
+                    $value = call_user_func_array([$this, $realMethod], $args);
+                    $promise->resolve($value);
+                },
+                function ($e) use (&$promise) {
+                    $promise->reject($e);
+                }
+            );
+
+            return $promise;
+        }
+    }
 }

tests/unit/Common/Api/OperatorTest.php

@@ -3,6 +3,7 @@
 namespace OpenStack\Test\Common\Api;
 
 use GuzzleHttp\ClientInterface;
+use GuzzleHttp\Promise\Promise;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\Psr7\Response;
 use OpenStack\Common\Api\Operator;
@@ -62,8 +63,33 @@ public function test_it_populates_models_from_arrays()
         $data = ['flavor' => [], 'image' => []];
         $this->assertInstanceOf(ResourceInterface::class, $this->operator->model(Server::class, $data));
     }
+
+    public function test_it_wraps_sequential_ops_in_promise_when_async_is_appended_to_method_name()
+    {
+        $promise = $this->operator->createAsync('something');
+
+        $this->assertInstanceOf(Promise::class, $promise);
+
+        $promise->then(function ($val) {
+            $this->assertEquals('Created something', $val);
+        });
+
+        $promise->wait();
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     */
+    public function test_it_throws_exception_when_async_is_called_on_a_non_existent_method()
+    {
+        $this->operator->fooAsync();
+    }
 }
 
 class TestOperator extends Operator
 {
+    public function create($str)
+    {
+        return 'Created ' . $str;
+    }
 }