🚧 introduce Yield promise

src/Adapter/Swoole/EventLoop.php

@@ -72,7 +72,6 @@ public function promiseRace(Promise ...$promises): Promise
      */
     public function promiseFulfilled($value): Promise
     {
-        new Pro
     }
 
     /**

src/Adapter/Swoole/Internal/YieldPromise.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace M6Web\Tornado\Adapter\Swoole\Internal;
+
+use M6Web\Tornado\Promise;
+use M6Web\Tornado\Deferred;
+use Swoole\Coroutine;
+
+final class YieldPromise implements Promise, Deferred
+{
+    private $cids = [];
+    private $isSettled = false;
+    private $value;
+
+    public function yield(): void
+    {
+        if($this->isSettled) {
+            return;
+        }
+
+        $this->cids[Coroutine::getCid()] = true;
+        Coroutine::yield();
+    }
+
+    public function value()
+    {
+        assert($this->isSettled, new \Error('Promise is not resolved.'));
+        return $this->value;
+    }
+
+    public function getPromise(): YieldPromise
+    {
+        return $this;
+    }
+
+    public function resolve($value): void
+    {
+        assert(false === $this->isSettled, new \Error('Promise is already resolved.'));
+        $this->isSettled = true;
+        $this->value = $value;
+        foreach ($this->cids as $cid => $dummy) {
+            Coroutine::resume($cid);
+        }
+        $this->cids = [];
+    }
+
+    public function reject(\Throwable $throwable): void
+    {
+
+    }
+}