From df161ce67204474a12434e1c1969007735d03747 Mon Sep 17 00:00:00 2001
From: Lars Oldiges <loldiges@spirit21.com>
Date: Wed, 22 Aug 2018 13:20:49 +0200
Subject: [PATCH] Allows MQTT Shared Subscriptions for MQTT-In core node

---
 nodes/core/io/10-mqtt.js | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/nodes/core/io/10-mqtt.js b/nodes/core/io/10-mqtt.js
index 509099aa4..d7cc027d3 100644
--- a/nodes/core/io/10-mqtt.js
+++ b/nodes/core/io/10-mqtt.js
@@ -24,6 +24,19 @@ module.exports = function(RED) {
         if (ts == "#") {
             return true;
         }
+        /* The following allows shared subscriptions (as in MQTT v5)
+           http://docs.oasis-open.org/mqtt/mqtt/v5.0/cs02/mqtt-v5.0-cs02.html#_Toc514345522
+           
+           4.8.2 describes shares like:
+           $share/{ShareName}/{filter}
+           $share is a literal string that marks the Topic Filter as being a Shared Subscription Topic Filter.
+           {ShareName} is a character string that does not include "/", "+" or "#"
+           {filter} The remainder of the string has the same syntax and semantics as a Topic Filter in a non-shared subscription. Refer to section 4.7.
+        */
+        else if(ts.startsWith("$share")){
+            ts = ts.replace(/^\$share\/[^#+/]+\/(.*)/g,"$1");
+            
+        }
         var re = new RegExp("^"+ts.replace(/([\[\]\?\(\)\\\\$\^\*\.|])/g,"\\$1").replace(/\+/g,"[^/]+").replace(/\/#$/,"(\/.*)?")+"$");
         return re.test(t);
     }