refactor: add email notification delay to chat message notifications

src/notifications.js

@@ -1,5 +1,6 @@
 'use strict';
 
+
 const async = require('async');
 const winston = require('winston');
 const cron = require('cron').CronJob;
@@ -15,9 +16,17 @@ const batch = require('./batch');
 const plugins = require('./plugins');
 const utils = require('./utils');
 const emailer = require('./emailer');
+const ttlCache = require('./cache/ttl');
 
 const Notifications = module.exports;
 
+// ttlcache for email-only chat notifications
+const notificationCache = ttlCache({
+	ttl: (meta.config.notificationSendDelay || 60) * 1000,
+	noDisposeOnSet: true,
+	dispose: sendEmail,
+});
+
 Notifications.baseTypes = [
 	'notificationType_upvote',
 	'notificationType_new-topic',
@@ -192,36 +201,6 @@ async function pushToUids(uids, notification) {
 		}
 	}
 
-	async function sendEmail(uids) {
-		// Update CTA messaging (as not all notification types need custom text)
-		if (['new-reply', 'new-chat'].includes(notification.type)) {
-			notification['cta-type'] = notification.type;
-		}
-		let body = notification.bodyLong || '';
-		if (meta.config.removeEmailNotificationImages) {
-			body = body.replace(/<img[^>]*>/, '');
-		}
-		body = posts.relativeToAbsolute(body, posts.urlRegex);
-		body = posts.relativeToAbsolute(body, posts.imgRegex);
-		let errorLogged = false;
-		await async.eachLimit(uids, 3, async (uid) => {
-			await emailer.send('notification', uid, {
-				path: notification.path,
-				notification_url: notification.path.startsWith('http') ? notification.path : nconf.get('url') + notification.path,
-				subject: utils.stripHTMLTags(notification.subject || '[[notifications:new_notification]]'),
-				intro: utils.stripHTMLTags(notification.bodyShort),
-				body: body,
-				notification: notification,
-				showUnsubscribe: true,
-			}).catch((err) => {
-				if (!errorLogged) {
-					winston.error(`[emailer.send] ${err.stack}`);
-					errorLogged = true;
-				}
-			});
-		});
-	}
-
 	async function getUidsBySettings(uids) {
 		const uidsToNotify = [];
 		const uidsToEmail = [];
@@ -252,18 +231,62 @@ async function pushToUids(uids, notification) {
 	if (notification.type) {
 		results = await getUidsBySettings(data.uids);
 	}
-	await Promise.all([
+	await sendNotification(results.uidsToNotify);
-		sendNotification(results.uidsToNotify),
+	const delayNotificationTypes = ['new-chat', 'new-group-chat', 'new-public-chat'];
-		sendEmail(results.uidsToEmail),
+	if (delayNotificationTypes.includes(notification.type)) {
-	]);
+		const cacheKey = `${notification.mergeId}|${results.uidsToEmail.join(',')}`;
+		if (notificationCache.has(cacheKey)) {
+			const payload = notificationCache.get(cacheKey);
+			notification.bodyLong = [payload.notification.bodyLong, notification.bodyLong].join('\n');
+		}
+		notificationCache.set(cacheKey, { uids: results.uidsToEmail, notification });
+	} else {
+		await sendEmail({ uids: results.uidsToEmail, notification });
+	}
+
 	plugins.hooks.fire('action:notification.pushed', {
-		notification: notification,
+		notification,
 		uids: results.uidsToNotify,
 		uidsNotified: results.uidsToNotify,
 		uidsEmailed: results.uidsToEmail,
 	});
 }
 
+async function sendEmail({ uids, notification }, mergeId, reason) {
+	// Only act on cache item expiry
+	if (reason && reason !== 'stale') {
+		return;
+	}
+
+	// Update CTA messaging (as not all notification types need custom text)
+	if (['new-reply', 'new-chat'].includes(notification.type)) {
+		notification['cta-type'] = notification.type;
+	}
+	let body = notification.bodyLong || '';
+	if (meta.config.removeEmailNotificationImages) {
+		body = body.replace(/<img[^>]*>/, '');
+	}
+	body = posts.relativeToAbsolute(body, posts.urlRegex);
+	body = posts.relativeToAbsolute(body, posts.imgRegex);
+	let errorLogged = false;
+	await async.eachLimit(uids, 3, async (uid) => {
+		await emailer.send('notification', uid, {
+			path: notification.path,
+			notification_url: notification.path.startsWith('http') ? notification.path : nconf.get('url') + notification.path,
+			subject: utils.stripHTMLTags(notification.subject || '[[notifications:new_notification]]'),
+			intro: utils.stripHTMLTags(notification.bodyShort),
+			body: body,
+			notification: notification,
+			showUnsubscribe: true,
+		}).catch((err) => {
+			if (!errorLogged) {
+				winston.error(`[emailer.send] ${err.stack}`);
+				errorLogged = true;
+			}
+		});
+	});
+}
+
 Notifications.pushGroup = async function (notification, groupName) {
 	if (!notification) {
 		return;