[App Search] Refactor empty engine polling to EngineLogic (elastic#10…

…3041)

* Set up isEngineEmpty and isEngineSchemaEmpty selectors

+ update selector tests with mock engines to just an `engine` var (I saw Jason do this down below for `searchKey` and liked it, so I copied it)
+ update Documents & Search UI pages to new selectors

* Update EngineOverview to use isEngineEmpty + remove polling

- Per Casey, polling is primarily only needed to dynamically update from empty state to non-empty state, which we're going to handle at the engine level in the next commit

* Add empty engine polling behavior

- Now that both Engines Overview, Documents, and Search UI views have empty states that are hooked up to EngineLogic, this poll will update all of the above pages automatically when a new document comes in!

* [Misc UI polish] Add (+) icon to Index documents button

- to match other create page header buttons

* [PR feedback] Test improvements

Co-authored-by: Jason Stoltzfus <jastoltz24@gmail.com>

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Jason Stoltzfus <jastoltz24@gmail.com>

x-pack/plugins/enterprise_search/public/applications/app_search/components/documents/components/document_creation_button.tsx

@@ -21,7 +21,7 @@ export const DocumentCreationButton: React.FC = () => {
     <>
       <EuiButton
         fill
-        color="primary"
+        iconType="plusInCircle"
         data-test-subj="IndexDocumentsButton"
         onClick={showCreationModes}
       >

x-pack/plugins/enterprise_search/public/applications/app_search/components/documents/documents.test.tsx

@@ -22,7 +22,6 @@ import { Documents } from '.';
 describe('Documents', () => {
   const values = {
     isMetaEngine: false,
-    engine: { document_count: 1 },
     myRole: { canManageEngineDocuments: true },
   };
 

x-pack/plugins/enterprise_search/public/applications/app_search/components/documents/documents.tsx

@@ -21,7 +21,7 @@ import { DOCUMENTS_TITLE } from './constants';
 import { SearchExperience } from './search_experience';
 
 export const Documents: React.FC = () => {
-  const { isMetaEngine, engine } = useValues(EngineLogic);
+  const { isMetaEngine, isEngineEmpty } = useValues(EngineLogic);
   const { myRole } = useValues(AppLogic);
 
   return (
@@ -32,7 +32,7 @@ export const Documents: React.FC = () => {
         rightSideItems:
           myRole.canManageEngineDocuments && !isMetaEngine ? [<DocumentCreationButton />] : [],
       }}
-      isEmptyState={!engine.document_count}
+      isEmptyState={isEngineEmpty}
       emptyState={<EmptyState />}
     >
       {isMetaEngine && (

x-pack/plugins/enterprise_search/public/applications/app_search/components/engine/constants.ts

@@ -0,0 +1,20 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { i18n } from '@kbn/i18n';
+
+export const POLLING_DURATION = 5000;
+
+export const POLLING_ERROR_TITLE = i18n.translate(
+  'xpack.enterpriseSearch.appSearch.engine.pollingErrorMessage',
+  { defaultMessage: 'Could not fetch engine data' }
+);
+
+export const POLLING_ERROR_TEXT = i18n.translate(
+  'xpack.enterpriseSearch.appSearch.engine.pollingErrorDescription',
+  { defaultMessage: 'Please check your connection or manually reload the page.' }
+);