adding last position in header if we're on the head link

Author: thefringeninja

src/SqlStreamStore.HAL.Tests/HeadersTests.cs

@@ -0,0 +1,44 @@
+namespace SqlStreamStore.HAL.Tests
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Net.Http;
+    using System.Threading.Tasks;
+    using Shouldly;
+    using Xunit;
+
+    public class HeadersTests : IDisposable
+    {
+        private const string StreamId = "a-stream";
+        private readonly SqlStreamStoreHalMiddlewareFixture _fixture;
+
+        public HeadersTests()
+        {
+            _fixture = new SqlStreamStoreHalMiddlewareFixture();
+        }
+
+        public void Dispose() => _fixture.Dispose();
+
+        public static IEnumerable<object[]> Methods()
+        {
+            yield return new object[] { HttpMethod.Head };
+            yield return new object[] { HttpMethod.Get };
+        }
+
+        [Theory, MemberData(nameof(Methods))]
+        public async Task all_stream_head_link(HttpMethod method)
+        {
+            await _fixture.WriteNMessages(StreamId, 10);
+
+            var position = await _fixture.StreamStore.ReadHeadPosition();
+
+            using(var response = await _fixture.HttpClient.SendAsync(new HttpRequestMessage(method, "/stream")))
+            {
+                response.IsSuccessStatusCode.ShouldBeTrue();
+
+                response.Headers.GetValues(Constants.Headers.HeadPosition)
+                    .ShouldBe(new[] { $"{position}" });
+            }
+        }
+    }
+}

src/SqlStreamStore.HAL/AllStreamResource.cs

@@ -35,7 +35,7 @@ public async Task<Response> GetPage(
                     : Task.FromResult<string>(null))
                 .ToArray());
 
-            return new Response(
+            var response = new Response(
                 new HALResponse(new object())
                     .AddLinks(Links.SelfFeed(options))
                     .AddLinks(Links.Navigation(page, options.Self))
@@ -54,6 +54,17 @@ public async Task<Response> GetPage(
                                 payload
                             }).AddLinks(
                                 Links.Self(message)))));
+
+            if(options.FromPositionInclusive == Position.End)
+            {
+                var headPosition = page.Messages.Length > 0
+                    ? page.Messages[0].Position
+                    : Position.End;
+                
+                response.Headers[Constants.Headers.HeadPosition] = new[] { $"{headPosition}" };
+            }
+            
+            return response;
         }
 
         public async Task<Response> GetMessage(

src/SqlStreamStore.HAL/Constants.cs

@@ -8,7 +8,8 @@ internal static class Constants
         public static class Headers
         {
             public const string ExpectedVersion = "SSS-ExpectedVersion";
-
+            public const string HeadPosition = "SSS-HeadPosition";
+            
             public static class ContentTypes
             {
                 public const string ProblemDetails = "application/problem+json";
@@ -27,5 +28,11 @@ public static class ContentTypes
                 [405] = "Method Not Allowed",
                 [409] = "Conflict"
             });
+
+        public static class ReadDirection
+        {
+            public const int Forwards = 1;
+            public const int Backwards = -1;
+        }
     }
 }

src/SqlStreamStore.HAL/ReadAllStreamOptions.cs

@@ -16,8 +16,8 @@ public ReadAllStreamOptions(IOwinRequest request)
             EmbedPayload = request.Query.Get("e") != null;
 
             ReadDirection = request.Query.Get("d") == "f"
-                ? 1
-                : -1;
+                ? Constants.ReadDirection.Forwards
+                : Constants.ReadDirection.Backwards;
 
             if(!long.TryParse(request.Query.Get("p"), out _fromPositionInclusive))
             {
@@ -35,12 +35,12 @@ public ReadAllStreamOptions(IOwinRequest request)
         public bool EmbedPayload { get; }
         public int ReadDirection { get; }
 
-        public string Self => ReadDirection > 0
+        public string Self => ReadDirection == Constants.ReadDirection.Forwards
             ? LinkFormatter.FormatForwardLink("stream", MaxCount, FromPositionInclusive)
             : LinkFormatter.FormatBackwardLink("stream", MaxCount, FromPositionInclusive);
 
         public Func<IReadonlyStreamStore, CancellationToken, Task<ReadAllPage>> GetReadOperation()
-            => (streamStore, ct) => ReadDirection > 0
+            => (streamStore, ct) => ReadDirection == Constants.ReadDirection.Forwards
                 ? streamStore.ReadAllForwards(_fromPositionInclusive, _maxCount, EmbedPayload, ct)
                 : streamStore.ReadAllBackwards(_fromPositionInclusive, _maxCount, EmbedPayload, ct);
     }

src/SqlStreamStore.HAL/ReadStreamOptions.cs

@@ -18,12 +18,14 @@ public ReadStreamOptions(IOwinRequest request)
             EmbedPayload = request.Query.Get("e") != null;
 
             ReadDirection = request.Query.Get("d") == "f"
-                ? 1
-                : -1;
+                ? Constants.ReadDirection.Forwards
+                : Constants.ReadDirection.Backwards;
 
             if(!int.TryParse(request.Query.Get("p"), out _fromVersionInclusive))
             {
-                _fromVersionInclusive = ReadDirection > 0 ? StreamVersion.Start : StreamVersion.End;
+                _fromVersionInclusive = ReadDirection == Constants.ReadDirection.Forwards 
+                    ? StreamVersion.Start 
+                    : StreamVersion.End;
             }
 
             if(!int.TryParse(request.Query.Get("m"), out _maxCount))
@@ -38,12 +40,12 @@ public ReadStreamOptions(IOwinRequest request)
         public int ReadDirection { get; }
         public string StreamId { get; }
 
-        public string Self => ReadDirection > 0
+        public string Self => ReadDirection == Constants.ReadDirection.Forwards
             ? LinkFormatter.FormatForwardLink(StreamId, MaxCount, FromVersionInclusive)
             : LinkFormatter.FormatBackwardLink(StreamId, MaxCount, FromVersionInclusive);
 
         public Func<IReadonlyStreamStore, CancellationToken, Task<ReadStreamPage>> GetReadOperation()
-            => (streamStore, ct) => ReadDirection > 0
+            => (streamStore, ct) => ReadDirection == Constants.ReadDirection.Forwards
                 ? streamStore.ReadStreamForwards(StreamId, _fromVersionInclusive, _maxCount, EmbedPayload, ct)
                 : streamStore.ReadStreamBackwards(StreamId, _fromVersionInclusive, _maxCount, EmbedPayload, ct);
     }