From d1b6acc57a4f04fcc320d395e3ad72dd13b4c54e Mon Sep 17 00:00:00 2001
From: Lee Stutzman <lstutzman@gmail.com>
Date: Fri, 3 Apr 2026 03:13:35 +0100
Subject: [PATCH] CODEBASE: Replace ipExists() linear scan with O(1) Map.has()
 (#2621)

---
 src/Server/AllServers.ts            |  7 +-----
 test/jest/Server/AllServers.test.ts | 35 +++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/src/Server/AllServers.ts b/src/Server/AllServers.ts
index a7a956171..24720489e 100644
--- a/src/Server/AllServers.ts
+++ b/src/Server/AllServers.ts
@@ -89,12 +89,7 @@ export const disconnectServers = (server1: BaseServer, server2: BaseServer) => {
 };
 
 export function ipExists(ip: string): boolean {
-  for (const server of AllServers.values()) {
-    if (server.ip === ip) {
-      return true;
-    }
-  }
-  return false;
+  return AllServers.has(ip);
 }
 
 export function createUniqueRandomIp(): IPAddress {
diff --git a/test/jest/Server/AllServers.test.ts b/test/jest/Server/AllServers.test.ts
index e93ee9d48..6d30d1a63 100644
--- a/test/jest/Server/AllServers.test.ts
+++ b/test/jest/Server/AllServers.test.ts
@@ -6,6 +6,7 @@ import {
   saveAllServers,
   renameServer,
   GetServer,
+  ipExists,
 } from "../../../src/Server/AllServers";
 import { Server } from "../../../src/Server/Server";
 import { IPAddress } from "../../../src/Types/strings";
@@ -38,6 +39,40 @@ describe("AllServers can be saved and loaded", () => {
   });
 });
 
+describe("ipExists", () => {
+  beforeEach(() => {
+    prestigeAllServers();
+  });
+
+  it("returns true for an IP that exists in AllServers", () => {
+    const server = new Server({ hostname: "test-server", ip: "10.20.30.40" as IPAddress });
+    AddToAllServers(server);
+    expect(ipExists("10.20.30.40")).toBe(true);
+  });
+
+  it("returns false for an IP that does not exist", () => {
+    expect(ipExists("99.99.99.99")).toBe(false);
+  });
+
+  it("does not use linear scan (performance: uses Map.has, not iteration)", () => {
+    // Add a server so the map is non-empty
+    const server = new Server({ hostname: "perf-test", ip: "1.1.1.1" as IPAddress });
+    AddToAllServers(server);
+
+    // Spy on Map.prototype.values to detect if ipExists iterates
+    const valuesSpy = jest.spyOn(Map.prototype, "values");
+
+    ipExists("1.1.1.1");
+    ipExists("2.2.2.2");
+
+    // With the fix (Map.has), values() should NOT be called by ipExists
+    // With the bug (for...of iteration), values() WOULD be called
+    expect(valuesSpy).not.toHaveBeenCalled();
+
+    valuesSpy.mockRestore();
+  });
+});
+
 describe("renameServer tests", () => {
   it("rename to self edge case", () => {
     prestigeAllServers();