From bfca97d9aff9b25155f1c511d3c51f0c0b6af6a7 Mon Sep 17 00:00:00 2001
From: Charles Solar <charlessolar@gmail.com>
Date: Wed, 3 Jan 2018 03:18:11 -0600
Subject: [PATCH] add different delivery modes for delayed messages - fix #27

---
 .../Internal/BulkInvokeHandlerTerminator.cs   | 19 +++++++++++++--
 .../Attributes/DelayedAttribute.cs            | 24 ++++++++++++++++++-
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/src/Aggregates.NET.NServiceBus/Internal/BulkInvokeHandlerTerminator.cs b/src/Aggregates.NET.NServiceBus/Internal/BulkInvokeHandlerTerminator.cs
index ea75114e..a51bf5ed 100644
--- a/src/Aggregates.NET.NServiceBus/Internal/BulkInvokeHandlerTerminator.cs
+++ b/src/Aggregates.NET.NServiceBus/Internal/BulkInvokeHandlerTerminator.cs
@@ -173,8 +173,23 @@ private async Task InvokeDelayedChannel(IDelayedChannel channel, string channelK
             
             using (var ctx = _metrics.Begin("Bulk Messages Time"))
             {
-                foreach (var idx in Enumerable.Range(0, messages.Length))
-                    await handler.Invoke(messages[idx].Message, context).ConfigureAwait(false);
+                switch (attr.Mode)
+                {
+                    case DeliveryMode.Single:
+                        foreach (var idx in Enumerable.Range(0, messages.Length))
+                            await handler.Invoke(messages[idx].Message, context).ConfigureAwait(false);
+                        break;
+                    case DeliveryMode.First:
+                        await handler.Invoke(messages[0].Message, context).ConfigureAwait(false);
+                        break;
+                    case DeliveryMode.Last:
+                        await handler.Invoke(messages[messages.Length-1].Message, context).ConfigureAwait(false);
+                        break;
+                    case DeliveryMode.FirstAndLast:
+                        await handler.Invoke(messages[0].Message, context).ConfigureAwait(false);
+                        await handler.Invoke(messages[messages.Length - 1].Message, context).ConfigureAwait(false);
+                        break;
+                }
                 
                 if(ctx.Elapsed > TimeSpan.FromSeconds(5))
                     SlowLogger.InfoEvent("Invoked", "{Count} messages channel [{Channel:l}] key [{Key:l}] took {Milliseconds} ms", count, channelKey, specificKey, ctx.Elapsed.TotalMilliseconds);
diff --git a/src/Aggregates.NET/Attributes/DelayedAttribute.cs b/src/Aggregates.NET/Attributes/DelayedAttribute.cs
index 99364d17..59edb8cc 100644
--- a/src/Aggregates.NET/Attributes/DelayedAttribute.cs
+++ b/src/Aggregates.NET/Attributes/DelayedAttribute.cs
@@ -5,16 +5,37 @@
 
 namespace Aggregates.Attributes
 {
+    public enum DeliveryMode
+    {
+        /// <summary>
+        /// Deliver each message as a single call to message handler
+        /// </summary>
+        Single,
+        /// <summary>
+        /// Deliver only the first message from a collection of waiting messages
+        /// </summary>
+        First,
+        /// <summary>
+        /// Deliver only the last message from a collection of waiting messages
+        /// </summary>
+        Last,
+        /// <summary>
+        /// Deliver both the first and last message from a collection of waiting messages
+        /// </summary>
+        FirstAndLast
+    }
+
     [AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = true)]
     public class DelayedAttribute : Attribute
     {
-        public DelayedAttribute(Type type, int count = -1, int delayMs = -1)
+        public DelayedAttribute(Type type, int count = -1, int delayMs = -1, DeliveryMode mode = DeliveryMode.Single)
         {
             this.Type = type;
             if(count != -1)
                 this.Count = count;
             if(delayMs != -1)
                 this.Delay = delayMs;
+            this.Mode = mode;
 
             if (Count > 200000)
                 throw new ArgumentException($"{nameof(Count)} too large - maximum is 200000");
@@ -36,6 +57,7 @@ public DelayedAttribute(Type type, int count = -1, int delayMs = -1)
         public Type Type { get; private set; }
         public int? Count { get; private set; }
         public int? Delay { get; private set; }
+        public DeliveryMode? Mode { get; private set; }
         public Func<object, string> KeyPropertyFunc { get; private set; }
     }