feat(search): create search plugin implementation

Signed-off-by: Camila Belo <camilaibs@gmail.com>

plugins/search-backend/package.json

@@ -24,6 +24,7 @@
   },
   "dependencies": {
     "@backstage/backend-common": "workspace:^",
+    "@backstage/backend-plugin-api": "workspace:^",
     "@backstage/config": "workspace:^",
     "@backstage/errors": "workspace:^",
     "@backstage/plugin-auth-node": "workspace:^",

plugins/search-backend/src/index.ts

@@ -21,3 +21,6 @@
  */
 
 export * from './service/router';
+
+// TODO: export as alfa subpath
+export { searchPlugin } from './plugin';

plugins/search-backend/src/plugin.ts

@@ -1,43 +1,109 @@
+/*
+ * Copyright 2023 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 import {
   coreServices,
   createBackendPlugin,
 } from '@backstage/backend-plugin-api';
 import { loggerToWinstonLogger } from '@backstage/backend-common';
 import {
-  searchIndexBuilderRef,
-  searchEngineExtensionPoint,
-  searchIndexExtensionPoint,
+  searchIndexBuilderService,
+  searchIndexRegistryExtensionPoint,
+  SearchIndexRegistryExtensionPoint,
+  searchEngineRegistryExtensionPoint,
+  RegisterCollatorParameters,
+  RegisterDecoratorParameters,
+  SearchEngineRegistryExtensionPoint,
+  LunrSearchEngine,
 } from '@backstage/plugin-search-backend-node';
 
 import { createRouter } from './service/router';
+import { SearchEngine } from '@backstage/plugin-search-common';
+
+class SearchIndexRegistry implements SearchIndexRegistryExtensionPoint {
+  private collators: RegisterCollatorParameters[] = [];
+  private decorators: RegisterDecoratorParameters[] = [];
+
+  public addCollator(options: RegisterCollatorParameters): void {
+    this.collators.push(options);
+  }
+
+  public addDecorator(options: RegisterDecoratorParameters): void {
+    this.decorators.push(options);
+  }
+
+  public getCollators(): RegisterCollatorParameters[] {
+    return this.collators;
+  }
+
+  public getDecorators(): RegisterDecoratorParameters[] {
+    return this.decorators;
+  }
+}
+
+class SearchEngineRegistry implements SearchEngineRegistryExtensionPoint {
+  private searchEngine: SearchEngine | null = null;
+
+  public setSearchEngine(searchEngine: SearchEngine): void {
+    if (this.searchEngine) {
+      throw new Error('Multiple Search engines is not supported at this time');
+    }
+    this.searchEngine = searchEngine;
+  }
+
+  public getSearchEngine(): SearchEngine | null {
+    return this.searchEngine;
+  }
+}
 
 export const searchPlugin = createBackendPlugin({
   pluginId: 'search',
   register(env) {
+    const searchIndexRegistry = new SearchIndexRegistry();
+    env.registerExtensionPoint(
+      searchIndexRegistryExtensionPoint,
+      searchIndexRegistry,
+    );
+
+    const searchEngineRegistry = new SearchEngineRegistry();
+    env.registerExtensionPoint(
+      searchEngineRegistryExtensionPoint,
+      searchEngineRegistry,
+    );
+
     env.registerInit({
       deps: {
         logger: coreServices.logger,
         config: coreServices.config,
         permissions: coreServices.permissions,
         http: coreServices.httpRouter,
-        searchIndexBuilder: searchIndexBuilderRef,
-        searchEngineRegistry: searchEngineExtensionPoint,
-        searchIndexRegistry: searchIndexExtensionPoint,
+        searchIndexBuilder: searchIndexBuilderService,
       },
-      async init({
-        config,
-        logger,
-        permissions,
-        http,
-        searchEngineRegistry,
-        searchIndexRegistry,
-        searchIndexBuilder,
-      }) {
-        const searchEngine = searchEngineRegistry.getSearchEngine();
+      async init({ config, logger, permissions, http, searchIndexBuilder }) {
+        let searchEngine = searchEngineRegistry.getSearchEngine();
+        if (!searchEngine) {
+          searchEngine = new LunrSearchEngine({
+            logger: loggerToWinstonLogger(logger),
+          });
+        }
+
         const collators = searchIndexRegistry.getCollators();
         const decorators = searchIndexRegistry.getDecorators();
 
-        const { scheduler } = searchIndexBuilder.build({
+        const { scheduler } = await searchIndexBuilder.build({
           searchEngine,
           collators,
           decorators,