Emit persistentIds snapshots so consumers can persist correctly

package.json

@@ -1,14 +1,17 @@
 {
   "name": "@superhuman/push-receiver",
-  "version": "2.1.7",
-  "description": "A module to subscribe to GCM/FCM and receive notifications within a node process.",
+  "version": "2.1.8",
+  "description":
+    "A module to subscribe to GCM/FCM and receive notifications within a node process.",
   "main": "src/index.js",
   "scripts": {
     "start": "node scripts/listen",
     "register": "node scripts/register",
     "send": "node scripts/send",
-    "pretty": "prettier-eslint --single-quote --trailing-comma es5 --write \"**/*.js\" \"**/*.json\"",
-    "pretty:check": "prettier-eslint --single-quote --trailing-comma es5 --list-different --log-level silent \"**/*.js\" \"**/*.json\"",
+    "pretty":
+      "prettier-eslint --single-quote --trailing-comma es5 --write \"**/*.js\" \"**/*.json\"",
+    "pretty:check":
+      "prettier-eslint --single-quote --trailing-comma es5 --list-different --log-level silent \"**/*.js\" \"**/*.json\"",
     "lint": "eslint 'src/**/*.js'",
     "lint:fix": "eslint 'src/**/*.js' --fix",
     "test": "jest",
@@ -19,9 +22,7 @@
       "eslint --fix",
       "prettier-eslint --single-quote --trailing-comma es5 --write"
     ],
-    "*.json": [
-      "prettier-eslint --single-quote --trailing-comma es5 --write"
-    ]
+    "*.json": ["prettier-eslint --single-quote --trailing-comma es5 --write"]
   },
   "repository": {
     "type": "git",

src/client.js

@@ -174,14 +174,24 @@ module.exports = class Client extends EventEmitter {
 
   _onMessage({ tag, object }) {
     if (tag === kLoginResponseTag) {
-      // clear persistent ids, as we just sent them to the server while logging
-      // in
-      this._persistentIds = [];
+      // A LoginResponse with an error means the server did not process our
+      // receivedPersistentId list, so the ids are not acked yet.
+      if (!object.error) {
+        this._persistentIds = [];
+        this._emitPersistentIds();
+      }
+      this.emit('loginResponse', object);
     } else if (tag === kDataMessageStanzaTag) {
       this._onDataMessage(object);
     }
   }
 
+  // Emits a snapshot so consumers can mirror the list (e.g. to disk) without
+  // sharing the mutable array.
+  _emitPersistentIds() {
+    this.emit('persistentIds', this._persistentIds.slice());
+  }
+
   _onDataMessage(object) {
     if (this._persistentIds.includes(object.persistentId)) {
       return;
@@ -193,13 +203,17 @@ module.exports = class Client extends EventEmitter {
     } catch (error) {
       if (isReportableDecryptionError(error)) {
         this._persistentIds.push(object.persistentId);
+        this._emitPersistentIds();
       }
       this._emitError(error);
       return;
     }
 
     // Maintain persistentIds updated with the very last received value
     this._persistentIds.push(object.persistentId);
+    // Deliver the id before the notification so a consumer that persists ids
+    // never handles a message it has not recorded yet.
+    this._emitPersistentIds();
     // Send notification
     this.emit('ON_NOTIFICATION_RECEIVED', {
       notification : message,

test/client.test.js

@@ -1,6 +1,7 @@
 jest.mock('../src/utils/decrypt');
 
 const Client = require('../src/client');
+const { kLoginResponseTag } = require('../src/constants');
 const decrypt = require('../src/utils/decrypt');
 
 const KEYS = {
@@ -13,11 +14,11 @@ function createClient(persistentIds = []) {
 }
 
 describe('Client', () => {
-  describe('_onDataMessage', () => {
-    beforeEach(() => {
-      decrypt.mockReset();
-    });
+  beforeEach(() => {
+    decrypt.mockReset();
+  });
 
+  describe('_onDataMessage', () => {
     [
       'Unsupported state or unable to authenticate data',
       'crypto-key is missing',
@@ -81,4 +82,101 @@ describe('Client', () => {
       });
     });
   });
+
+  describe('persistentIds event', () => {
+    it('clears and emits on a successful login response', () => {
+      const client = createClient(['a', 'b']);
+      const onPersistentIds = jest.fn();
+      const onLoginResponse = jest.fn();
+      client.on('persistentIds', onPersistentIds);
+      client.on('loginResponse', onLoginResponse);
+
+      client._onMessage({ tag : kLoginResponseTag, object : {} });
+
+      expect(client._persistentIds).toEqual([]);
+      expect(onPersistentIds).toHaveBeenCalledWith([]);
+      expect(onLoginResponse).toHaveBeenCalledWith({});
+    });
+
+    it('does not clear on an errored login response', () => {
+      const client = createClient(['a', 'b']);
+      const onPersistentIds = jest.fn();
+      const onLoginResponse = jest.fn();
+      client.on('persistentIds', onPersistentIds);
+      client.on('loginResponse', onLoginResponse);
+      const object = { error : { code : 1 } };
+
+      client._onMessage({ tag : kLoginResponseTag, object });
+
+      expect(client._persistentIds).toEqual(['a', 'b']);
+      expect(onPersistentIds).not.toHaveBeenCalled();
+      expect(onLoginResponse).toHaveBeenCalledWith(object);
+    });
+
+    it('emits before the notification on a decrypted message', () => {
+      const client = createClient();
+      const order = [];
+      decrypt.mockReturnValue({ title : 'Hello' });
+      client.on('persistentIds', ids => order.push(['persistentIds', ids]));
+      client.on('ON_NOTIFICATION_RECEIVED', () => order.push(['notification']));
+
+      client._onDataMessage({ persistentId : 'persistent-id' });
+
+      expect(order).toEqual([
+        ['persistentIds', ['persistent-id']],
+        ['notification'],
+      ]);
+    });
+
+    it('emits after recording a reportable decryption error', () => {
+      const client = createClient();
+      const onPersistentIds = jest.fn();
+      client.on('persistentIds', onPersistentIds);
+      client.on('error', () => {});
+      decrypt.mockImplementation(() => {
+        throw new Error('salt is missing');
+      });
+
+      client._onDataMessage({ persistentId : 'persistent-id' });
+
+      expect(onPersistentIds).toHaveBeenCalledWith(['persistent-id']);
+    });
+
+    it('does not emit for an unreportable decryption error', () => {
+      const client = createClient();
+      const onPersistentIds = jest.fn();
+      client.on('persistentIds', onPersistentIds);
+      client.on('error', () => {});
+      decrypt.mockImplementation(() => {
+        throw new Error('unexpected decrypt failure');
+      });
+
+      client._onDataMessage({ persistentId : 'persistent-id' });
+
+      expect(onPersistentIds).not.toHaveBeenCalled();
+    });
+
+    it('does not emit for an already-recorded persistent id', () => {
+      const client = createClient(['persistent-id']);
+      const onPersistentIds = jest.fn();
+      client.on('persistentIds', onPersistentIds);
+
+      client._onDataMessage({ persistentId : 'persistent-id' });
+
+      expect(onPersistentIds).not.toHaveBeenCalled();
+    });
+
+    it('emits a snapshot copy of the full id list', () => {
+      const client = createClient();
+      const snapshots = [];
+      decrypt.mockReturnValue({ title : 'Hello' });
+      client.on('persistentIds', ids => snapshots.push(ids));
+
+      client._onDataMessage({ persistentId : 'a' });
+      snapshots[0].push('mutated');
+      client._onDataMessage({ persistentId : 'b' });
+
+      expect(snapshots[1]).toEqual(['a', 'b']);
+    });
+  });
 });