feat: send notification to group owners when someone leaves

public/language/en-GB/groups.json

@@ -60,6 +60,7 @@
 	"membership.invitation-pending": "Invitation Pending",
 	"membership.join-group": "Join Group",
 	"membership.leave-group": "Leave Group",
+	"membership.leave.notification_title": "<strong>%1</strong> has left group <strong>%2</strong>",
 	"membership.reject": "Reject",
 
 	"new-group.group_name": "Group Name:",

src/groups/invite.js

@@ -45,9 +45,7 @@ module.exports = function (Groups) {
 			groupNames = [groupNames];
 		}
 		const sets = [];
-		groupNames.forEach(function (groupName) {
-			sets.push('group:' + groupName + ':pending', 'group:' + groupName + ':invited');
-		});
+		groupNames.forEach(groupName =>	sets.push('group:' + groupName + ':pending', 'group:' + groupName + ':invited'));
 		await db.setsRemove(sets, uid);
 	};
 

src/socket.io/groups.js

@@ -1,11 +1,13 @@
 'use strict';
 
+const validator = require('validator');
 const groups = require('../groups');
 const meta = require('../meta');
 const user = require('../user');
 const utils = require('../utils');
 const events = require('../events');
 const privileges = require('../privileges');
+const notifications = require('../notifications');
 
 const SocketGroups = module.exports;
 
@@ -74,6 +76,16 @@ SocketGroups.leave = async (socket, data) => {
 	}
 
 	await groups.leave(data.groupName, socket.uid);
+	const username = await user.getUserField(socket.uid, 'username');
+	const notification = await notifications.create({
+		type: 'group-leave',
+		bodyShort: '[[groups:membership.leave.notification_title, ' + username + ', ' + data.groupName + ']]',
+		nid: 'group:' + validator.escape(data.groupName) + ':uid:' + socket.uid + ':group-leave',
+		path: '/groups/' + utils.slugify(data.groupName),
+	});
+	const uids = await groups.getOwners(data.groupName);
+	await notifications.push(notification, uids);
+
 	logGroupEvent(socket, 'group-leave', {
 		groupName: data.groupName,
 	});