class FiberBoundContextStorage

final class FiberBoundContextStorage implements ContextStorageInterface, ContextStorageHeadAware {
    
    /** @var WeakMap<object, ContextStorageHead> */
    private WeakMap $heads;
    public function __construct() {
        $this->heads = new WeakMap();
        $this->heads[$this] = new ContextStorageHead($this);
    }
    public function head() : ?ContextStorageHead {
        return $this->heads[Fiber::getCurrent() ?? $this] ?? null;
    }
    public function scope() : ?ContextStorageScopeInterface {
        $head = $this->heads[Fiber::getCurrent() ?? $this] ?? null;
        if (!$head?->node && Fiber::getCurrent()) {
            self::triggerNotInitializedFiberContextWarning();
            return null;
        }
        // Starts with empty head instead of cloned parent -> no need to check for head mismatch
        return $head->node;
    }
    public function current() : ContextInterface {
        $head = $this->heads[Fiber::getCurrent() ?? $this] ?? null;
        if (!$head?->node && Fiber::getCurrent()) {
            self::triggerNotInitializedFiberContextWarning();
            // Fallback to {main} to preserve BC
            $head = $this->heads[$this];
        }
        return $head->node->context ?? Context::getRoot();
    }
    public function attach(ContextInterface $context) : ContextStorageScopeInterface {
        $head = $this->heads[Fiber::getCurrent() ?? $this] ??= new ContextStorageHead($this);
        return $head->node = new ContextStorageNode($context, $head, $head->node);
    }
    private static function triggerNotInitializedFiberContextWarning() : void {
        $fiber = Fiber::getCurrent();
        assert($fiber !== null);
        trigger_error(sprintf('Access to not initialized OpenTelemetry context in fiber (id: %d), automatic forking not supported, must attach initial fiber context manually', spl_object_id($fiber)), E_USER_WARNING);
    }

}