From 8f5779cd70796ac65022919bee4c502ccfeec9ba Mon Sep 17 00:00:00 2001
From: Emily Janzer <janzer@fb.com>
Date: Wed, 29 Jan 2020 11:43:22 -0800
Subject: [PATCH] Add in the optimization to check the first/least timer in the
 queue before iterating (#27841)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/27841

Follow up from https://github.com/facebook/react-native/pull/27539 - adding back in the optimization that Detox has in TimersIdlingResource to avoid iterating over the entire timers queue if the next timer is already within the specified range.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D19522346

fbshipit-source-id: 32609f434d1ca575a5a49ad630e288c43fa90864
---
 .../react/modules/core/JavaTimerManager.java     | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/modules/core/JavaTimerManager.java b/ReactAndroid/src/main/java/com/facebook/react/modules/core/JavaTimerManager.java
index 37548d4c46a..37fc90ff333 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/modules/core/JavaTimerManager.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/modules/core/JavaTimerManager.java
@@ -384,12 +384,26 @@ public class JavaTimerManager {
    */
   /* package */ boolean hasActiveTimersInRange(long rangeMs) {
     synchronized (mTimerGuard) {
+      Timer nextTimer = mTimers.peek();
+      if (nextTimer == null) {
+        // Timers queue is empty
+        return false;
+      }
+      if (isTimerInRange(nextTimer, rangeMs)) {
+        // First check the next timer, so we can avoid iterating over the entire queue if it's
+        // already within range.
+        return true;
+      }
       for (Timer timer : mTimers) {
-        if (!timer.mRepeat && timer.mInterval < rangeMs) {
+        if (isTimerInRange(timer, rangeMs)) {
           return true;
         }
       }
     }
     return false;
   }
+
+  private static boolean isTimerInRange(Timer timer, long rangeMs) {
+    return !timer.mRepeat && timer.mInterval < rangeMs;
+  }
 }