etag on single message

Author: thefringeninja

src/SqlStreamStore.HAL.Tests/StreamMessageTests.cs

@@ -2,6 +2,7 @@
 {
     using System;
     using System.Net;
+    using System.Net.Http.Headers;
     using System.Threading.Tasks;
     using Shouldly;
     using Xunit;
@@ -20,12 +21,12 @@ public StreamMessageTests()
         [Fact]
         public async Task read_single_message_stream()
         {
-            // position of event in all stream would be helpful here
             var writeResult = await _fixture.WriteNMessages("a-stream", 1);
 
             using(var response = await _fixture.HttpClient.GetAsync("/streams/a-stream/0"))
             {
                 response.StatusCode.ShouldBe(HttpStatusCode.OK);
+                response.Headers.ETag.ShouldBe(new EntityTagHeaderValue($@"""{writeResult.CurrentVersion};{writeResult.CurrentPosition}"""));
 
                 var resource = await response.AsHal();
 
@@ -56,6 +57,7 @@ public async Task read_single_message_does_not_exist_stream()
             using(var response = await _fixture.HttpClient.GetAsync("/streams/a-stream/0"))
             {
                 response.StatusCode.ShouldBe(HttpStatusCode.NotFound);
+                response.Headers.ETag.ShouldBeNull();
 
                 var resource = await response.AsHal();
 
@@ -91,6 +93,7 @@ public async Task delete_single_message_by_version()
             using(var response = await _fixture.HttpClient.GetAsync("/streams/a-stream/0"))
             {
                 response.StatusCode.ShouldBe(HttpStatusCode.NotFound);
+                response.Headers.ETag.ShouldBeNull();
             }
         }
     }

src/SqlStreamStore.HAL/CaseSensitiveQueryCollection.cs

@@ -1,30 +1,10 @@
 namespace SqlStreamStore.HAL
 {
-    using System;
     using System.Collections;
     using System.Collections.Generic;
     using Microsoft.AspNetCore.Http;
-    using Microsoft.AspNetCore.Http.Features;
     using Microsoft.Extensions.Primitives;
 
-    internal class CaseSensitiveQueryFeature : IQueryFeature
-    {
-        private readonly IFeatureCollection _features;
-
-        public CaseSensitiveQueryFeature(IFeatureCollection features)
-        {
-            if(features == null)
-                throw new ArgumentNullException(nameof(features));
-            _features = features;
-        }
-
-        public IQueryCollection Query
-        {
-            get;
-            set;
-        }
-    }
-
     internal class CaseSensitiveQueryCollection : IQueryCollection
     {
         private readonly QueryString _queryString;

src/SqlStreamStore.HAL/Constants.cs

@@ -8,6 +8,7 @@ public static class Headers
             public const string HeadPosition = "SSS-HeadPosition";
             public const string MessageId = "SSS-MessageId";
             public const string Location = "Location";
+            public const string ETag = "ETag";
 
             public static class ContentTypes
             {

src/SqlStreamStore.HAL/Resources/StreamMessageResource.cs

@@ -79,7 +79,10 @@ public async Task<Response> Get(
                     .AddLinks(Links.Self(operation))
                     .AddLinks(Links.Navigation(operation, message))
                     .AddLinks(Links.Message(operation))
-                    .AddLinks(Links.Find()));
+                    .AddLinks(Links.Find()))
+            {
+                Headers = { [Constants.Headers.ETag] = new[] { $@"""{message.StreamVersion};{message.Position}""" } }
+            };
         }
 
         public async Task<Response> DeleteMessage(