Upvote notification frequency selection (#6087)

Closes #5963

- Notify on every upvote
- Notify on every tenth upvote
- Notify logarithmically (on 10, 100, 1000...)
- Disable upvote notifications

src/socket.io/helpers.js

@@ -13,7 +13,7 @@ var notifications = require('../notifications');
 var plugins = require('../plugins');
 var utils = require('../utils');
 
-var SocketHelpers = {};
+var SocketHelpers = module.exports;
 
 SocketHelpers.notifyOnlineUsers = function (uid, result) {
 	winston.warn('[deprecated] SocketHelpers.notifyOnlineUsers, consider using socketHelpers.notifyNew(uid, \'newPost\', result);');
@@ -171,6 +171,51 @@ SocketHelpers.sendNotificationToTopicOwner = function (tid, fromuid, command, no
 	});
 };
 
+SocketHelpers.upvote = function (data, notification) {
+	if (!data || !data.post || !data.post.uid || !data.post.votes || !data.post.pid || !data.fromuid) {
+		return;
+	}
+
+	var votes = data.post.votes;
+	var touid = data.post.uid;
+	var fromuid = data.fromuid;
+	var pid = data.post.pid;
+
+	var shouldNotify = {
+		all: function () {
+			return votes > 0;
+		},
+		everyTen: function () {
+			return votes > 0 && votes % 10 === 0;
+		},
+		logarithmic: function () {
+			return votes > 1 && Math.log10(votes) % 1 === 0;
+		},
+		disabled: function () {
+			return false;
+		},
+	};
+
+	async.waterfall([
+		function (next) {
+			user.getSettings(touid, next);
+		},
+		function (settings, next) {
+			var should = shouldNotify[settings.upvoteNotifFreq] || shouldNotify.all;
+
+			if (should()) {
+				SocketHelpers.sendNotificationToPostOwner(pid, fromuid, 'upvote', notification);
+			}
+
+			next();
+		},
+	], function (err) {
+		if (err) {
+			winston.error(err);
+		}
+	});
+};
+
 SocketHelpers.rescindUpvoteNotification = function (pid, fromuid) {
 	var uid;
 	async.waterfall([
@@ -199,5 +244,3 @@ SocketHelpers.emitToTopicAndCategory = function (event, data) {
 	websockets.in('topic_' + data.tid).emit(event, data);
 	websockets.in('category_' + data.cid).emit(event, data);
 };
-
-module.exports = SocketHelpers;