From 21b729b983e2ddbe1dd9cff31f996825a45ec4e0 Mon Sep 17 00:00:00 2001
From: Neal Beeken <neal.beeken@mongodb.com>
Date: Wed, 22 May 2024 16:17:22 -0400
Subject: [PATCH] fix(NODE-6165): useBigInt64 causes compareTopologyVersion to
 throw (#4109)

Co-authored-by: Bailey Pearson <bailey.pearson@mongodb.com>
---
 src/sdam/server_description.ts            | 17 +++++++++++++----
 test/unit/sdam/server_description.test.ts | 22 ++++++++++++++++++++++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/src/sdam/server_description.ts b/src/sdam/server_description.ts
index 5068931b6a..c95f7cc905 100644
--- a/src/sdam/server_description.ts
+++ b/src/sdam/server_description.ts
@@ -258,10 +258,19 @@ export function compareTopologyVersion(
   }
 
   // TODO(NODE-2674): Preserve int64 sent from MongoDB
-  const currentCounter = Long.isLong(currentTv.counter)
-    ? currentTv.counter
-    : Long.fromNumber(currentTv.counter);
-  const newCounter = Long.isLong(newTv.counter) ? newTv.counter : Long.fromNumber(newTv.counter);
+  const currentCounter =
+    typeof currentTv.counter === 'bigint'
+      ? Long.fromBigInt(currentTv.counter)
+      : Long.isLong(currentTv.counter)
+      ? currentTv.counter
+      : Long.fromNumber(currentTv.counter);
+
+  const newCounter =
+    typeof newTv.counter === 'bigint'
+      ? Long.fromBigInt(newTv.counter)
+      : Long.isLong(newTv.counter)
+      ? newTv.counter
+      : Long.fromNumber(newTv.counter);
 
   return currentCounter.compare(newCounter);
 }
diff --git a/test/unit/sdam/server_description.test.ts b/test/unit/sdam/server_description.test.ts
index e91a0863bd..14c3ae0dbd 100644
--- a/test/unit/sdam/server_description.test.ts
+++ b/test/unit/sdam/server_description.test.ts
@@ -130,6 +130,22 @@ describe('ServerDescription', function () {
         currentTv: { processId: processIdZero, counter: Long.fromNumber(2) },
         newTv: { processId: processIdZero, counter: Long.fromNumber(2) },
         out: 0
+      },
+      {
+        title: 'when process ids are equal and both counter values are zero bigints',
+        // @ts-expect-error: Testing that the function handles bigints
+        currentTv: { processId: processIdZero, counter: 0n },
+        // @ts-expect-error: Testing that the function handles bigints
+        newTv: { processId: processIdZero, counter: 0n },
+        out: 0
+      },
+      {
+        title: 'when process ids are equal and both counter values are non-zero bigints',
+        // @ts-expect-error: Testing that the function handles bigints
+        currentTv: { processId: processIdZero, counter: 2n },
+        // @ts-expect-error: Testing that the function handles bigints
+        newTv: { processId: processIdZero, counter: 2n },
+        out: 0
       }
     ];
     const compareTopologyVersionLessThanTests: CompareTopologyVersionTest[] = [
@@ -178,6 +194,12 @@ describe('ServerDescription', function () {
         currentTv: { processId: processIdZero, counter: Long.fromNumber(3) },
         newTv: { processId: processIdZero, counter: Long.fromNumber(2) },
         out: 1
+      },
+      {
+        title: 'when processIds are equal but new counter is less than current (bigint)',
+        currentTv: { processId: processIdZero, counter: 3n },
+        newTv: { processId: processIdZero, counter: 2n },
+        out: 1
       }
     ];