integration-react: initial ScmAuthMux implementation

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/integration-react/src/api/ScmAuthMux.ts

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2021 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 { OAuthApi } from '@backstage/core-plugin-api';
+import {
+  ScmAuthApi,
+  ScmAuthTokenOptions,
+  ScmAuthTokenResponse,
+} from './ScmAuthApi';
+
+type Provider = {
+  api: ScmAuthApi;
+  predicate: (url: URL) => boolean;
+};
+
+class OAuthApiWrapper {
+  constructor(
+    private readonly oauthApi: OAuthApi,
+    private readonly scopeMapping: {
+      [scope in keyof Required<ScmAuthTokenOptions['scope']>]: string[];
+    },
+  ) {}
+
+  async getCredentials(
+    options: ScmAuthTokenOptions,
+  ): Promise<ScmAuthTokenResponse> {
+    const scopes = Object.entries(options.scope).flatMap(
+      ([scope, requested]) => {
+        if (requested) {
+          return this.scopeMapping[scope as keyof ScmAuthTokenOptions['scope']];
+        }
+        return [];
+      },
+    );
+    const token = await this.oauthApi.getAccessToken(scopes, {
+      instantPopup: options.instantPopup,
+      optional: options.optional,
+    });
+    return {
+      token,
+      headers: {
+        Authorization: `Bearer ${token}`,
+      },
+    };
+  }
+}
+
+export class ScmAuthMux implements ScmAuthApi {
+  static fromProviders(providers: Provider[]): ScmAuthMux {
+    return new ScmAuthMux(providers);
+  }
+
+  static fromAuthApi(
+    authApi: OAuthApi,
+    options: {
+      scopeMapping: {
+        [scope in keyof Required<ScmAuthTokenOptions['scope']>]: string[];
+      };
+    },
+  ): ScmAuthApi {
+    return new OAuthApiWrapper(authApi, options.scopeMapping);
+  }
+
+  static providerForGithub(
+    githubAuthApi: OAuthApi,
+    options?: {
+      hostname?: string;
+    },
+  ): Provider {
+    const hostname = options?.hostname ?? 'github.com';
+    return {
+      api: this.fromAuthApi(githubAuthApi, {
+        scopeMapping: {
+          repoRead: ['repo'],
+          repoWrite: ['repo'],
+        },
+      }),
+      predicate: url => url.hostname === hostname,
+    };
+  }
+
+  private constructor(private readonly providers: Provider[]) {}
+
+  getCredentials(
+    options: ScmAuthTokenOptions,
+  ): Promise<ScmAuthTokenResponse | undefined> {
+    const url = new URL(options.url);
+    const provider = this.providers.find(p => p.predicate(url));
+    if (!provider) {
+      throw new Error(
+        `No authentication provider available for SCM access to '${options.url}'`,
+      );
+    }
+
+    return provider.api.getCredentials(options);
+  }
+}

packages/integration-react/src/api/index.ts

@@ -15,6 +15,7 @@
  */
 
 export { scmAuthApiRef } from './ScmAuthApi';
+export { ScmAuthMux } from './ScmAuthMux';
 export type {
   ScmAuthApi,
   ScmAuthTokenOptions,