From 4caceedcffeb44d1e637fe64ce9a509e9a0db5b8 Mon Sep 17 00:00:00 2001
From: Jan Kassens <jkassens@meta.com>
Date: Mon, 17 Apr 2023 16:24:33 -0400
Subject: [PATCH] Revert "Clean up discrete event replaying (#26558)"

This reverts commit 9cfba0f6ecc15a342ef184552742c5db6c7f2d3e.
---
 .../src/events/ReactDOMEventListener.js       |  2 +-
 .../src/events/ReactDOMEventReplaying.js      | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/packages/react-dom-bindings/src/events/ReactDOMEventListener.js b/packages/react-dom-bindings/src/events/ReactDOMEventListener.js
index 70cec7fa0e608..eef07fddf39ee 100644
--- a/packages/react-dom-bindings/src/events/ReactDOMEventListener.js
+++ b/packages/react-dom-bindings/src/events/ReactDOMEventListener.js
@@ -57,7 +57,7 @@ import {isRootDehydrated} from 'react-reconciler/src/ReactFiberShellHydration';
 const {ReactCurrentBatchConfig} = ReactSharedInternals;
 
 // TODO: can we stop exporting these?
-let _enabled: boolean = true;
+export let _enabled: boolean = true;
 
 // This is exported in FB builds for use by legacy FB layer infra.
 // We'd like to remove this but it's not clear if this is safe.
diff --git a/packages/react-dom-bindings/src/events/ReactDOMEventReplaying.js b/packages/react-dom-bindings/src/events/ReactDOMEventReplaying.js
index 59fc3a8a61811..3e91e174c4fd5 100644
--- a/packages/react-dom-bindings/src/events/ReactDOMEventReplaying.js
+++ b/packages/react-dom-bindings/src/events/ReactDOMEventReplaying.js
@@ -60,6 +60,11 @@ type QueuedReplayableEvent = {
 
 let hasScheduledReplayAttempt = false;
 
+// The queue of discrete events to be replayed.
+const queuedDiscreteEvents: Array<QueuedReplayableEvent> = [];
+
+// Indicates if any continuous event targets are non-null for early bailout.
+const hasAnyQueuedContinuousEvents: boolean = false;
 // The last of each continuous event type. We only need to replay the last one
 // if the last target was dehydrated.
 let queuedFocus: null | QueuedReplayableEvent = null;
@@ -77,6 +82,14 @@ type QueuedHydrationTarget = {
 };
 const queuedExplicitHydrationTargets: Array<QueuedHydrationTarget> = [];
 
+export function hasQueuedDiscreteEvents(): boolean {
+  return queuedDiscreteEvents.length > 0;
+}
+
+export function hasQueuedContinuousEvents(): boolean {
+  return hasAnyQueuedContinuousEvents;
+}
+
 const discreteReplayableEvents: Array<DOMEventName> = [
   'mousedown',
   'mouseup',
@@ -433,6 +446,21 @@ function scheduleCallbackIfUnblocked(
 export function retryIfBlockedOn(
   unblocked: Container | SuspenseInstance,
 ): void {
+  // Mark anything that was blocked on this as no longer blocked
+  // and eligible for a replay.
+  if (queuedDiscreteEvents.length > 0) {
+    scheduleCallbackIfUnblocked(queuedDiscreteEvents[0], unblocked);
+    // This is a exponential search for each boundary that commits. I think it's
+    // worth it because we expect very few discrete events to queue up and once
+    // we are actually fully unblocked it will be fast to replay them.
+    for (let i = 1; i < queuedDiscreteEvents.length; i++) {
+      const queuedEvent = queuedDiscreteEvents[i];
+      if (queuedEvent.blockedOn === unblocked) {
+        queuedEvent.blockedOn = null;
+      }
+    }
+  }
+
   if (queuedFocus !== null) {
     scheduleCallbackIfUnblocked(queuedFocus, unblocked);
   }