move event files to yoga/events folder

Summary: Moved events files to yoga/events for better code structure

Reviewed By: davidaurelio

Differential Revision: D15198566

fbshipit-source-id: 74d451011841d59fae5a1c637f9c33a7d2d1f87e

yoga/event/event.cpp

@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the LICENSE
+ * file in the root directory of this source tree.
+ */
+#include "event.h"
+#include <memory>
+#include <stdexcept>
+
+#include <iostream>
+
+namespace facebook {
+namespace yoga {
+
+namespace {
+
+// For now, a single subscriber is enough.
+// This can be changed as soon as the need for more than one subscriber arises.
+std::function<Event::Subscriber>& globalEventSubscriber() {
+  static std::function<Event::Subscriber> subscriber = nullptr;
+  return subscriber;
+}
+
+} // namespace
+
+void Event::reset() {
+  globalEventSubscriber() = nullptr;
+}
+
+void Event::subscribe(std::function<Subscriber>&& subscriber) {
+  if (globalEventSubscriber() != nullptr) {
+    throw std::logic_error(
+        "Yoga currently supports only one global event subscriber");
+  }
+  globalEventSubscriber() = std::move(subscriber);
+}
+
+void Event::publish(const YGNode& node, Type eventType, const Data& eventData) {
+  auto& subscriber = globalEventSubscriber();
+  if (subscriber) {
+    subscriber(node, eventType, eventData);
+  }
+}
+
+} // namespace yoga
+} // namespace facebook