When incoming message should've been sealed sender, reply with profile key

ts/services/ourProfileKey.ts

@@ -0,0 +1,87 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from '../util/assert';
+import * as log from '../logging/log';
+
+// We define a stricter storage here that returns `unknown` instead of `any`.
+type Storage = {
+  get(key: string): unknown;
+  put(key: string, value: unknown): Promise<void>;
+  remove(key: string): Promise<void>;
+  onready: (callback: () => unknown) => void;
+};
+
+export class OurProfileKeyService {
+  private getPromise: undefined | Promise<undefined | ArrayBuffer>;
+
+  private promisesBlockingGet: Array<Promise<unknown>> = [];
+
+  private storage?: Storage;
+
+  initialize(storage: Storage): void {
+    log.info('Our profile key service: initializing');
+
+    const storageReadyPromise = new Promise<void>(resolve => {
+      storage.onready(() => {
+        resolve();
+      });
+    });
+    this.promisesBlockingGet = [storageReadyPromise];
+
+    this.storage = storage;
+  }
+
+  get(): Promise<undefined | ArrayBuffer> {
+    if (this.getPromise) {
+      log.info(
+        'Our profile key service: was already fetching. Piggybacking off of that'
+      );
+    } else {
+      log.info('Our profile key service: kicking off a new fetch');
+      this.getPromise = this.doGet();
+    }
+    return this.getPromise;
+  }
+
+  async set(newValue: undefined | ArrayBuffer): Promise<void> {
+    log.info('Our profile key service: updating profile key');
+    assert(this.storage, 'OurProfileKeyService was not initialized');
+    if (newValue) {
+      await this.storage.put('profileKey', newValue);
+    } else {
+      await this.storage.remove('profileKey');
+    }
+  }
+
+  blockGetWithPromise(promise: Promise<unknown>): void {
+    this.promisesBlockingGet.push(promise);
+  }
+
+  private async doGet(): Promise<undefined | ArrayBuffer> {
+    log.info(
+      `Our profile key service: waiting for ${this.promisesBlockingGet.length} promises before fetching`
+    );
+
+    await Promise.allSettled(this.promisesBlockingGet);
+    this.promisesBlockingGet = [];
+
+    delete this.getPromise;
+
+    assert(this.storage, 'OurProfileKeyService was not initialized');
+
+    log.info('Our profile key service: fetching profile key from storage');
+    const result = this.storage.get('profileKey');
+    if (result === undefined || result instanceof ArrayBuffer) {
+      return result;
+    }
+
+    assert(
+      false,
+      'Profile key in storage was defined, but not an ArrayBuffer. Returning undefined'
+    );
+    return undefined;
+  }
+}
+
+export const ourProfileKeyService = new OurProfileKeyService();