chore: initial test with demo.backstage.io authentication

Signed-off-by: blam <ben@blam.sh>

packages/app/src/UrlPatternDiscovery.ts

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2020 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 { DiscoveryApi } from '@backstage/core-plugin-api';
+
+const ERROR_PREFIX = 'Invalid discovery URL pattern,';
+
+/**
+ * UrlPatternDiscovery is a lightweight DiscoveryApi implementation.
+ * It uses a single template string to construct URLs for each plugin.
+ *
+ * @public
+ */
+export class UrlPatternDiscovery implements DiscoveryApi {
+  /**
+   * Creates a new UrlPatternDiscovery given a template. The the only
+   * interpolation done for the template is to replace instances of `{{pluginId}}`
+   * with the ID of the plugin being requested.
+   *
+   * Example pattern: `http://localhost:7007/api/{{ pluginId }}`
+   */
+  static compile(pattern: string): UrlPatternDiscovery {
+    const parts = pattern.split(/\{\{\s*pluginId\s*\}\}/);
+    const urlStr = parts.join('pluginId');
+
+    let url;
+    try {
+      url = new URL(urlStr);
+    } catch {
+      throw new Error(`${ERROR_PREFIX} URL '${urlStr}' is invalid`);
+    }
+    if (url.hash) {
+      throw new Error(`${ERROR_PREFIX} URL must not have a hash`);
+    }
+    if (url.search) {
+      throw new Error(`${ERROR_PREFIX} URL must not have a query`);
+    }
+    if (urlStr.endsWith('/')) {
+      throw new Error(`${ERROR_PREFIX} URL must not end with a slash`);
+    }
+
+    return new UrlPatternDiscovery(parts);
+  }
+
+  private constructor(private readonly parts: string[]) {}
+
+  async getBaseUrl(pluginId: string): Promise<string> {
+    if (pluginId === 'auth') {
+      return 'https://demo.backstage.io/api/auth';
+    }
+
+    return this.parts.join(pluginId);
+  }
+}

packages/app/src/apis.ts

@@ -31,11 +31,21 @@ import {
   AnyApiFactory,
   configApiRef,
   createApiFactory,
+  discoveryApiRef,
   errorApiRef,
   githubAuthApiRef,
 } from '@backstage/core-plugin-api';
+import { UrlPatternDiscovery } from './UrlPatternDiscovery';
 
 export const apis: AnyApiFactory[] = [
+  createApiFactory({
+    api: discoveryApiRef,
+    deps: { configApi: configApiRef },
+    factory: ({ configApi }) =>
+      UrlPatternDiscovery.compile(
+        `${configApi.getString('backend.baseUrl')}/api/{{ pluginId }}`,
+      ),
+  }),
   createApiFactory({
     api: scmIntegrationsApiRef,
     deps: { configApi: configApiRef },