Implementing FCM sendAll() API

package.json

@@ -55,6 +55,7 @@
     "@firebase/app": "^0.3.4",
     "@firebase/database": "^0.3.6",
     "@types/node": "^8.0.53",
+    "dicer": "^0.3.0",
     "jsonwebtoken": "8.1.0",
     "node-forge": "0.7.4"
   },
@@ -89,6 +90,7 @@
     "gulp-header": "^1.8.8",
     "gulp-replace": "^0.5.4",
     "gulp-typescript": "^3.2.4",
+    "http-message-parser": "^0.0.34",
     "lodash": "^4.17.5",
     "merge2": "^1.2.1",
     "minimist": "^1.2.0",

src/index.d.ts

@@ -586,10 +586,26 @@ declare namespace admin.messaging {
     errors: admin.FirebaseArrayIndexError[];
   };
 
+  type BatchResponse = {
+    responses: admin.messaging.SendResponse[];
+    successCount: number;
+    failureCount: number;
+  }
+
+  type SendResponse = {
+    success: boolean;
+    messageId?: string;
+    error?: admin.FirebaseError;
+  };
+
   interface Messaging {
     app: admin.app.App;
 
     send(message: admin.messaging.Message, dryRun?: boolean): Promise<string>;
+    sendAll(
+      messages: Array<admin.messaging.Message>,
+      dryRun?: boolean
+    ): Promise<admin.messaging.BatchResponse>;
     sendToDevice(
       registrationToken: string | string[],
       payload: admin.messaging.MessagingPayload,

src/messaging/batch-request.ts

@@ -0,0 +1,114 @@
+/*!
+ * Copyright 2019 Google Inc.
+ *
+ * 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 {
+  HttpClient, HttpRequestConfig, HttpResponse, parseHttpResponse,
+} from '../utils/api-request';
+
+const PART_DELIMITER: string = '__END_OF_PART__';
+const TEN_SECONDS_IN_MILLIS = 10000;
+
+/**
+ * An HTTP client that can be used to make batch requests. This client is not tied to any service
+ * (FCM or otherwise). Therefore it can be used to make batch requests to any service that allows
+ * it. If this requirement ever arises we can move this implementation to the utils module
+ * where it can be easily shared among other modules.
+ */
+export class BatchRequestClient {
+
+  /**
+   * @param {HttpClient} httpClient The client that will be used to make HTTP calls.
+   * @param {string} batchUrl The URL that accepts batch requests.
+   * @param {object=} commonHeaders Optional headers that will be included in all requests.
+   *
+   * @constructor
+   */
+  constructor(
+    private readonly httpClient: HttpClient,
+    private readonly batchUrl: string,
+    private readonly commonHeaders?: object) {
+  }
+
+  /**
+   * Sends the given array of sub requests as a single batch, and parses the results into an array
+   * of HttpResponse objects.
+   *
+   * @param {SubRequest[]} requests An array of sub requests to send.
+   * @return {Promise<HttpResponse[]>} A promise that resolves when the send operation is complete.
+   */
+  public send(requests: SubRequest[]): Promise<HttpResponse[]> {
+    const requestHeaders = {
+      'Content-Type': `multipart/mixed; boundary=${PART_DELIMITER}`,
+    };
+    const request: HttpRequestConfig = {
+      method: 'POST',
+      url: this.batchUrl,
+      data: this.getMultipartPayload(requests),
+      headers: Object.assign({}, this.commonHeaders, requestHeaders),
+      timeout: TEN_SECONDS_IN_MILLIS,
+    };
+    return this.httpClient.send(request).then((response) => {
+      return response.multipart.map((buff) => {
+        return parseHttpResponse(buff, request);
+      });
+    });
+  }
+
+  private getMultipartPayload(requests: SubRequest[]): Buffer {
+    let buffer: string = '';
+    requests.forEach((request: SubRequest, idx: number) => {
+      buffer += createPart(request, PART_DELIMITER, idx);
+    });
+    buffer += `--${PART_DELIMITER}--\r\n`;
+    return Buffer.from(buffer, 'utf-8');
+  }
+}
+
+/**
+ * Represents a request that can be sent as part of an HTTP batch request.
+ */
+export interface SubRequest {
+  url: string;
+  body: object;
+  headers?: {[key: string]: any};
+}
+
+function createPart(request: SubRequest, delim: string, idx: number): string {
+  const serializedRequest: string = serializeSubRequest(request);
+  let part: string = `--${delim}\r\n`;
+  part += `Content-Length: ${serializedRequest.length}\r\n`;
+  part += 'Content-Type: application/http\r\n';
+  part += `content-id: ${idx + 1}\r\n`;
+  part += 'content-transfer-encoding: binary\r\n';
+  part += '\r\n';
+  part += `${serializedRequest}\r\n`;
+  return part;
+}
+
+function serializeSubRequest(request: SubRequest): string {
+  const requestBody: string = JSON.stringify(request.body);
+  let messagePayload: string = `POST ${request.url} HTTP/1.1\r\n`;
+  messagePayload += `Content-Length: ${requestBody.length}\r\n`;
+  messagePayload += 'Content-Type: application/json; charset=UTF-8\r\n';
+  if (request.headers) {
+    Object.keys(request.headers).forEach((key) => {
+      messagePayload += `${key}: ${request.headers[key]}\r\n`;
+    });
+  }
+  messagePayload += '\r\n';
+  messagePayload += requestBody;
+  return messagePayload;
+}