From 7e73abd5848cc391b12541e6948c06f1f538a16f Mon Sep 17 00:00:00 2001
From: Maxim Kholod <maxim.kholod@elastic.co>
Date: Thu, 21 Sep 2023 14:41:45 +0200
Subject: [PATCH] use agent version less then kibana version if the matching
 version is not released

---
 .../public/hooks/use_agent_version.test.ts    | 36 +++++++++++++++++++
 .../fleet/public/hooks/use_agent_version.ts   | 13 +++++--
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/x-pack/plugins/fleet/public/hooks/use_agent_version.test.ts b/x-pack/plugins/fleet/public/hooks/use_agent_version.test.ts
index 75a419f77fba9..6cb1c8ee42248 100644
--- a/x-pack/plugins/fleet/public/hooks/use_agent_version.test.ts
+++ b/x-pack/plugins/fleet/public/hooks/use_agent_version.test.ts
@@ -55,6 +55,24 @@ describe('useAgentVersion', () => {
     expect(result.current).toEqual('8.9.2');
   });
 
+  it('should return the agent version that is <= Kibana version if an agent version that matches Kibana version is not released', async () => {
+    const mockKibanaVersion = '8.8.3';
+    const mockAvailableVersions = ['8.8.0', '8.8.1', '8.8.2', '8.7.0', '8.9.2', '7.16.0'];
+
+    (useKibanaVersion as jest.Mock).mockReturnValue(mockKibanaVersion);
+    (sendGetAgentsAvailableVersions as jest.Mock).mockResolvedValue({
+      data: { items: mockAvailableVersions },
+    });
+
+    const { result, waitForNextUpdate } = renderHook(() => useAgentVersion());
+
+    expect(sendGetAgentsAvailableVersions).toHaveBeenCalled();
+
+    await waitForNextUpdate();
+
+    expect(result.current).toEqual('8.8.2');
+  });
+
   it('should return the latest availeble agent version if a snapshot version', async () => {
     const mockKibanaVersion = '8.10.0-SNAPSHOT';
     const mockAvailableVersions = ['8.8.0', '8.7.0', '8.9.2', '7.16.0'];
@@ -73,6 +91,24 @@ describe('useAgentVersion', () => {
     expect(result.current).toEqual('8.9.2');
   });
 
+  it('should return kibana version if no agent versions available', async () => {
+    const mockKibanaVersion = '8.11.0';
+    const mockAvailableVersions: string[] = [];
+
+    (useKibanaVersion as jest.Mock).mockReturnValue(mockKibanaVersion);
+    (sendGetAgentsAvailableVersions as jest.Mock).mockResolvedValue({
+      data: { items: mockAvailableVersions },
+    });
+
+    const { result, waitForNextUpdate } = renderHook(() => useAgentVersion());
+
+    expect(sendGetAgentsAvailableVersions).toHaveBeenCalled();
+
+    await waitForNextUpdate();
+
+    expect(result.current).toEqual('8.11.0');
+  });
+
   it('should return kibana version if the list of available agent versions is not available', async () => {
     const mockKibanaVersion = '8.11.0';
 
diff --git a/x-pack/plugins/fleet/public/hooks/use_agent_version.ts b/x-pack/plugins/fleet/public/hooks/use_agent_version.ts
index 9874d7e506b2c..7e9c732f8a8df 100644
--- a/x-pack/plugins/fleet/public/hooks/use_agent_version.ts
+++ b/x-pack/plugins/fleet/public/hooks/use_agent_version.ts
@@ -6,12 +6,13 @@
  */
 import { useEffect, useState } from 'react';
 import semverRcompare from 'semver/functions/rcompare';
+import semverLt from 'semver/functions/lt';
 
 import { useKibanaVersion } from './use_kibana_version';
 import { sendGetAgentsAvailableVersions } from './use_request';
 
 /**
- * @returns The most recent agent version available to install or upgrade to.
+ * @returns The most compatible agent version available to install or upgrade to.
  */
 export const useAgentVersion = (): string | undefined => {
   const kibanaVersion = useKibanaVersion();
@@ -22,6 +23,7 @@ export const useAgentVersion = (): string | undefined => {
       try {
         const res = await sendGetAgentsAvailableVersions();
         const availableVersions = res?.data?.items;
+        let agentVersionToUse = kibanaVersion;
 
         if (
           availableVersions &&
@@ -29,10 +31,15 @@ export const useAgentVersion = (): string | undefined => {
           availableVersions.indexOf(kibanaVersion) === -1
         ) {
           availableVersions.sort(semverRcompare);
-          setAgentVersion(availableVersions[0]);
+          agentVersionToUse =
+            availableVersions.find((version) => {
+              return semverLt(version, kibanaVersion);
+            }) || availableVersions[0];
         } else {
-          setAgentVersion(kibanaVersion);
+          agentVersionToUse = kibanaVersion;
         }
+
+        setAgentVersion(agentVersionToUse);
       } catch (err) {
         setAgentVersion(kibanaVersion);
       }