Add "topic based fair queue" option to delay node

nodes/core/core/89-delay.html

@@ -21,8 +21,9 @@
         <label for="node-input-pauseType"><i class="fa fa-tasks"></i> Action</label>
         <select id="node-input-pauseType" style="width:270px !important">
           <option value="delay">Delay message</option>
-          <option value="rate">Limit rate to</option>
           <option value="random">Random delay</option>
+          <option value="rate">Limit rate to</option>
+          <option value="queue">Topic based fair queue</option>
         </select>
     </div>
     <div id="delay-details" class="form-row">
@@ -38,9 +39,9 @@
     </div>
 
     <div id="rate-details" class="form-row">
-        <label for="node-input-rate"><i class="fa fa-clock-o"></i> To</label>
+        <label for="node-input-rate"><i class="fa fa-clock-o"></i> Rate</label>
         <input type="text" id="node-input-rate" placeholder="1" style="direction:rtl; width:30px !important">
-        <label for="node-input-reateUnits">msg(s) per</label>
+        <label for="node-input-rateUnits">msg(s) per</label>
         <select id="node-input-rateUnits" style="width:140px !important">
           <option value="second">Second</option>
           <option value="minute">Minute</option>
@@ -48,9 +49,10 @@
           <option value="day">Day</option>
         </select>
         <br/>
-        <input style="margin: 20px 0 20px 100px; width: 30px;" type="checkbox" id="node-input-drop"><label style="width: 250px;" for="node-input-drop">drop intermediate messages</label>
+        <div id="node-input-dr"><input style="margin: 20px 0 20px 100px; width: 30px;" type="checkbox" id="node-input-drop"><label style="width: 250px;" for="node-input-drop">drop intermediate messages</label></div>
     </div>
 
+
     <div id="random-details" class="form-row">
         <label for="node-input-randomFirst"><i class="fa fa-clock-o"></i> Between</label>
         <input type="text" id="node-input-randomFirst" placeholder="" style="directon:rtl; width:30px !important">
@@ -74,8 +76,13 @@
 
 <!-- Next, some simple help text is provided for the node.                   -->
 <script type="text/x-red" data-help-name="delay">
-    <p>Introduces a delay into a flow or rate limts messges</p>
+    <p>Introduces a delay into a flow or rate limits messages.</p>
-    <p>Default delay is 5 seconds and rate limit of 1 msg/second, but both can be configured</p>
+    <p>Default delay is 5 seconds and rate limit of 1 msg/second, but both can be configured.</p>
+    <p>If you select a rate limit you may optionally discard any intermediate messages that arrive.</p>
+    <p>The "topic based fair queue" adds messages to a release queue tagged by their <b>msg.topic</b> property.
+    At each "tick", derived from the rate, the next "topic" is released.
+    Any messages arriving on the same topic before release replace those in that position in the queue.
+    So each "topic" gets a turn - but the most recent value is always the one sent.</p>
 </script>
 
 <!-- Finally, the node type is registered along with all of its properties   -->
@@ -125,14 +132,22 @@
             $("#delay-details").show();
             $("#rate-details").hide();
             $("#random-details").hide();
+            $("#node-input-dr").hide();
           } else if (this.pauseType == "rate") {
             $("#delay-details").hide();
             $("#rate-details").show();
             $("#random-details").hide();
+            $("#node-input-dr").show();
           } else if (this.pauseType == "random") {
             $("#delay-details").hide();
             $("#rate-details").hide();
             $("#random-details").show();
+            $("#node-input-dr").hide();
+          } else if (this.pauseType == "queue") {
+            $("#delay-details").hide();
+            $("#rate-details").show();
+            $("#random-details").hide();
+            $("#node-input-dr").hide();
           }
 
           if (!this.timeoutUnits) {
@@ -152,14 +167,22 @@
               $("#delay-details").show();
               $("#rate-details").hide();
               $("#random-details").hide();
+              $("#node-input-dr").hide();
             } else if (this.value == "rate") {
               $("#delay-details").hide();
               $("#rate-details").show();
               $("#random-details").hide();
+              $("#node-input-dr").show();
               } else if (this.value == "random") {
               $("#delay-details").hide();
               $("#rate-details").hide();
               $("#random-details").show();
+              $("#node-input-dr").hide();
+            } else if (this.value == "queue") {
+              $("#delay-details").hide();
+              $("#rate-details").show();
+              $("#random-details").hide();
+              $("#node-input-dr").hide();
             }
           });
         }

nodes/core/core/89-delay.js

@@ -151,6 +151,34 @@ module.exports = function(RED) {
                 this.buffer = [];
             });
 
+        } else if (this.pauseType === "queue") {
+            this.intervalID = setInterval(function() {
+                if (node.buffer.length > 0) {
+                    node.send(node.buffer.shift()); // send the first on the queue
+                }
+                node.status({text:node.buffer.length});
+                //console.log(node.buffer);
+            },node.rate);
+
+            this.on("input", function(msg) {
+                if (!msg.hasOwnProperty("topic")) { msg.topic = "_none_"; }
+                var hit = false;
+                for (var b in node.buffer) { // check if already in queue
+                    if (msg.topic === node.buffer[b].topic) {
+                        node.buffer[b] = msg; // if so - replace existing entry
+                        hit = true;
+                    }
+                }
+                if (!hit) { node.buffer.push(msg); } // if not add to end of queue
+                node.status({text:node.buffer.length});
+            });
+
+            this.on("close", function() {
+                clearInterval(this.intervalID);
+                this.buffer = [];
+                node.status({text:node.buffer.length});
+            });
+
         } else if (this.pauseType === "random") {
             this.on("input",function(msg){
                 node.buffer.push(msg);