[Fleet] Fix asset for template path filter (#240750)

## Summary

This PR fixes the filter that was selecting the asset for a given
`template_path`. When compiling the template for a given input, fleet
was selecting it through the asset map taking into account the rule
"path ends with X". This method opened the door to some bug behavour in
the following case:

- A template path `log.yml.hbs`
- An asset map with `log.yml.hbs` and `syslog.yml.hbs` 

Both assets where selected, the first one was chosen, but not necessary
the first was `log.yml.hbs` although both end with this string.

The change introduces a change when selecting the template path to get
the exact file, although a fallback to the old logic is kept as there
are cases where the endsWith logic makes sense. This is when a default
template path is used (`stream.yml.hbs`) and the asset is called
`filestream.yml.hbs`

Related change at package-spec
elastic/package-spec#1002
Original issue elastic/package-spec#703

### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/src/platform/packages/shared/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This was checked for breaking HTTP API changes, and any breaking
changes have been approved by the breaking-change committee. The
`release_note:breaking` label should be applied in these situations.
- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [ ] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [ ] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

## Release note

Fixes `template_path` asset selection for some cases of integration
packages

Author: teresaromero

x-pack/platform/plugins/shared/fleet/server/services/package_policy.test.ts

@@ -38,6 +38,7 @@ import type {
   PostPackagePolicyPostCreateCallback,
   PostPackagePolicyDeleteCallback,
   UpdatePackagePolicy,
+  AssetsMap,
 } from '../types';
 import { createPackagePolicyMock } from '../../common/mocks';
 
@@ -58,6 +59,7 @@ import type {
   DeletePackagePoliciesResponse,
   PackagePolicyAssetsMap,
   PreconfiguredInputs,
+  ArchiveEntry,
 } from '../../common/types';
 import { packageToPackagePolicy, packageToPackagePolicyInputs } from '../../common/services';
 
@@ -73,6 +75,7 @@ import {
   _compilePackagePolicyInputs,
   _validateRestrictedFieldsNotModifiedOrThrow,
   _normalizePackagePolicyKuery,
+  _getAssetForTemplatePath,
 } from './package_policy';
 import { appContextService } from '.';
 
@@ -8808,3 +8811,54 @@ describe('_normalizePackagePolicyKuery', () => {
     expect(res).toEqual('ingest-package-policies.attributes.name:test');
   });
 });
+
+describe('_getAssetForTemplatePath()', () => {
+  it('should return the asset for the given template path', () => {
+    const pkgInfo: PackageInfo = {
+      name: 'test_package',
+      version: '1.0.0',
+      type: 'integration',
+    } as any;
+    const datasetPath = 'test_data_stream';
+    const templatePath = 'log.yml.hbs';
+    const assetsMap: AssetsMap = new Map();
+    assetsMap.set(
+      `test_package-1.0.0/data_stream/${datasetPath}/agent/stream/syslog.yml.hbs`,
+      Buffer.from('wrong match asset')
+    );
+    assetsMap.set(
+      `test_package-1.0.0/data_stream/${datasetPath}/agent/stream/log.yml.hbs`,
+      Buffer.from('exact match asset')
+    );
+
+    const expectedAsset: ArchiveEntry = {
+      path: 'test_package-1.0.0/data_stream/test_data_stream/agent/stream/log.yml.hbs',
+      buffer: Buffer.from('exact match asset'),
+    };
+    const asset = _getAssetForTemplatePath(pkgInfo, assetsMap, datasetPath, templatePath);
+    expect(asset).toEqual(expectedAsset);
+  });
+  it('should return fallback asset it exact match is not found', () => {
+    // representing the scenario where the templatePath has the default value 'stream.yml.hbs'
+    // but the actual asset uses a prefixed name like 'filestream.yml.hbs'
+    const pkgInfo: PackageInfo = {
+      name: 'test_package',
+      version: '1.0.0',
+      type: 'integration',
+    } as any;
+    const datasetPath = 'test_data_stream';
+    const templatePath = 'stream.yml.hbs';
+    const assetsMap: AssetsMap = new Map();
+    assetsMap.set(
+      `test_package-1.0.0/data_stream/${datasetPath}/agent/stream/filestream.yml.hbs`,
+      Buffer.from('ends with match asset')
+    );
+
+    const expectedFallbackAsset: ArchiveEntry = {
+      path: 'test_package-1.0.0/data_stream/test_data_stream/agent/stream/filestream.yml.hbs',
+      buffer: Buffer.from('ends with match asset'),
+    };
+    const asset = _getAssetForTemplatePath(pkgInfo, assetsMap, datasetPath, templatePath);
+    expect(asset).toEqual(expectedFallbackAsset);
+  });
+});

x-pack/platform/plugins/shared/fleet/server/services/package_policy.ts

@@ -84,6 +84,7 @@ import type {
   CloudConnectorSecretVar,
   AwsCloudConnectorVars,
   PackagePolicyConfigRecord,
+  ArchiveEntry,
 } from '../../common/types';
 import {
   FleetError,
@@ -113,6 +114,7 @@ import type {
   PostPackagePolicyCreateCallback,
   PostPackagePolicyPostCreateCallback,
   PutPackagePolicyPostUpdateCallback,
+  AssetsMap,
 } from '../types';
 import type { ExternalCallback } from '..';
 
@@ -3287,6 +3289,32 @@ export function _applyIndexPrivileges(
   return streamOut;
 }
 
+export function _getAssetForTemplatePath(
+  pkgInfo: PackageInfo,
+  assetsMap: AssetsMap,
+  datasetPath: string,
+  templatePath: string
+): ArchiveEntry {
+  const assets = getAssetsDataFromAssetsMap(
+    pkgInfo,
+    assetsMap,
+    (path: string) => path.endsWith(`/agent/stream/${templatePath}`),
+    datasetPath
+  );
+  if (assets.length === 1) {
+    return assets[0];
+  }
+
+  // fallback to old path structure for backward compatibility
+  const [fallbackPkgStreamTemplate] = getAssetsDataFromAssetsMap(
+    pkgInfo,
+    assetsMap,
+    (path: string) => path.endsWith(templatePath),
+    datasetPath
+  );
+  return fallbackPkgStreamTemplate;
+}
+
 function _compilePackageStream(
   pkgInfo: PackageInfo,
   vars: PackagePolicy['vars'],
@@ -3334,11 +3362,11 @@ function _compilePackageStream(
 
   const datasetPath = packageDataStream.path;
 
-  const [pkgStreamTemplate] = getAssetsDataFromAssetsMap(
+  const pkgStreamTemplate = _getAssetForTemplatePath(
     pkgInfo,
     assetsMap,
-    (path: string) => path.endsWith(streamFromPkg.template_path),
-    datasetPath
+    datasetPath,
+    streamFromPkg.template_path
   );
 
   if (!pkgStreamTemplate || !pkgStreamTemplate.buffer) {