From c218e38abccaf39951df73eed8d43cedb51924b8 Mon Sep 17 00:00:00 2001
From: Alexander Zinchuk <alx.zinchuk@gmail.com>
Date: Sun, 27 Jun 2021 19:09:18 +0300
Subject: [PATCH] Notifications: Group multiple push notifications (#1209)

---
 src/serviceWorker.ts                  |  1 -
 src/serviceWorker/pushNotification.ts | 62 +++++++++++++++++++++++----
 2 files changed, 53 insertions(+), 10 deletions(-)

diff --git a/src/serviceWorker.ts b/src/serviceWorker.ts
index 1127f99f5..80c4ba99d 100644
--- a/src/serviceWorker.ts
+++ b/src/serviceWorker.ts
@@ -45,7 +45,6 @@ self.addEventListener('fetch', (e: FetchEvent) => {
   })());
 });
 
-
 self.addEventListener('push', handlePush);
 self.addEventListener('notificationclick', handleNotificationClick);
 self.addEventListener('message', handleClientMessage);
diff --git a/src/serviceWorker/pushNotification.ts b/src/serviceWorker/pushNotification.ts
index 5780038dc..3bc984841 100644
--- a/src/serviceWorker/pushNotification.ts
+++ b/src/serviceWorker/pushNotification.ts
@@ -1,4 +1,5 @@
 import { APP_NAME, DEBUG } from '../config';
+import { debounce } from '../util/schedulers';
 
 declare const self: ServiceWorkerGlobalScope;
 
@@ -32,6 +33,7 @@ type NotificationData = {
 
 const clickBuffer: Record<string, NotificationData> = {};
 const shownNotifications = new Set();
+let pendingNotifications: Record<number, NotificationData[]> = {};
 
 function getPushData(e: PushEvent | Notification): PushData | undefined {
   try {
@@ -91,6 +93,55 @@ function showNotification({
   });
 }
 
+async function showNotifications(groupLimit: number = 1) {
+  const count = Object.keys(pendingNotifications).reduce<number>((result, groupId) => {
+    result += pendingNotifications[Number(groupId)].length;
+    return result;
+  }, 0);
+  // if we have more than groupLimit notification groups we send only one notification
+  if (Object.keys(pendingNotifications).length > groupLimit) {
+    await showNotification({
+      title: APP_NAME,
+      body: `You have ${count} new Telegram notifications`,
+    });
+  } else {
+    // Else we send a notification per group
+    await Promise.all(Object.keys(pendingNotifications)
+      // eslint-disable-next-line no-async-without-await/no-async-without-await
+      .map(async (groupId) => {
+        const group = pendingNotifications[Number(groupId)];
+        if (group.length > groupLimit) {
+          return showNotification({
+            title: APP_NAME,
+            body: `You have ${count} notifications from ${group[0].title}`,
+            chatId: Number(groupId),
+          });
+        }
+        return Promise.all(group.map(showNotification));
+      }));
+  }
+
+  // Clear all pending notifications
+  pendingNotifications = {};
+}
+
+const flushNotifications = debounce(showNotifications, 1000, false);
+
+async function handleNotification(notification: NotificationData, groupLimit?: number) {
+  // Dont show already triggered notification
+  if (shownNotifications.has(notification.messageId)) {
+    shownNotifications.delete(notification.messageId);
+    return;
+  }
+
+  const groupId = notification.chatId || 0;
+  if (!pendingNotifications[groupId]) {
+    pendingNotifications[groupId] = [];
+  }
+  pendingNotifications[groupId].push(notification);
+  await flushNotifications(groupLimit);
+}
+
 export function handlePush(e: PushEvent) {
   if (DEBUG) {
     // eslint-disable-next-line no-console
@@ -106,14 +157,7 @@ export function handlePush(e: PushEvent) {
   if (!data || data.mute === Boolean.True) return;
 
   const notification = getNotificationData(data);
-
-  // Dont show already triggered notification
-  if (shownNotifications.has(notification.messageId)) {
-    shownNotifications.delete(notification.messageId);
-    return;
-  }
-
-  e.waitUntil(showNotification(notification));
+  e.waitUntil(handleNotification(notification));
 }
 
 async function focusChatMessage(client: WindowClient, data: { chatId?: number; messageId?: number }) {
@@ -181,7 +225,7 @@ export function handleClientMessage(e: ExtendableMessageEvent) {
   if (e.data.type === 'newMessageNotification') {
     // store messageId for already shown notification
     const notification: NotificationData = e.data.payload;
-    e.waitUntil(showNotification(notification));
+    e.waitUntil(handleNotification(notification, 3));
     shownNotifications.add(notification.messageId);
   }
 }