tentative support for HEAD requests on streams

Author: thefringeninja

src/KestrelPureOwin/Properties/AssemblyInfo.cs

@@ -1,5 +1,4 @@
 using System.Reflection;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 // General Information about an assembly is controlled through the following

src/SqlStreamStore.HAL.DevServer/Program.cs

@@ -5,7 +5,6 @@
     using System.Threading;
     using System.Threading.Tasks;
     using KestrelPureOwin;
-    using Microsoft.AspNetCore.Server.Kestrel;
     using Microsoft.AspNetCore.Server.Kestrel.Core;
     using SqlStreamStore.Streams;
     using BuildFunc = System.Action<

src/SqlStreamStore.HAL/OwinContextExtensions.cs

@@ -1,12 +1,61 @@
 namespace SqlStreamStore.HAL
 {
+    using System;
     using System.IO;
+    using System.Threading;
     using System.Threading.Tasks;
     using Microsoft.IO;
     using Microsoft.Owin;
     using Newtonsoft.Json;
     using Newtonsoft.Json.Serialization;
     using SqlStreamStore.Streams;
+    
+    internal class OptionalHeadRequestWrapper : IDisposable
+    {
+        private readonly IOwinContext _context;
+        private readonly Stream _originalBody;
+
+        public OptionalHeadRequestWrapper(IOwinContext context)
+        {
+            _context = context;
+            _originalBody = _context.Response.Body;
+            if(context.Request.Method == "HEAD")
+            {
+                context.Response.Body = new HeadRequestStream();
+            }
+        }
+        
+        public void Dispose()
+        {
+            _context.Response.Body = _originalBody;
+        }
+
+        class HeadRequestStream : Stream
+        {
+            private long _length;
+
+            public override void Flush() => FlushAsync(CancellationToken.None).Wait();
+            public override int Read(byte[] buffer, int offset, int count) => throw new NotImplementedException();
+            public override long Seek(long offset, SeekOrigin origin) => throw new NotImplementedException();
+            public override void SetLength(long value) => throw new NotImplementedException();
+            public override void Write(byte[] buffer, int offset, int count) => throw new NotImplementedException();
+
+            public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+            {
+                _length += count;
+                Position += count;
+                return Task.CompletedTask;
+            }
+
+            public override Task FlushAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+
+            public override bool CanRead { get; } = false;
+            public override bool CanSeek { get; } = false;
+            public override bool CanWrite { get; } = true;
+            public override long Length => _length;
+            public override long Position { get; set; }
+        } 
+    }
 
     internal static class OwinContextExtensions
     {

src/SqlStreamStore.HAL/ReadAllStreamMiddleware.cs

@@ -41,18 +41,24 @@ private static MidFunc GetStream(AllStreamResource allStream) => next => async e
 
             var response = await allStream.GetPage(options, context.Request.CallCancelled);
 
-            await context.WriteHalResponse(response);
+            using(new OptionalHeadRequestWrapper(context))
+            {
+                await context.WriteHalResponse(response);
+            }
         };
 
         private static MidFunc GetStreamMessage(AllStreamResource allStream) => next => async env =>
         {
             var context = new OwinContext(env);
 
-            var resource = await allStream.GetMessage(
+            var response = await allStream.GetMessage(
                 new ReadAllStreamMessageOptions(context.Request),
                 context.Request.CallCancelled);
 
-            await context.WriteHalResponse(resource);
+            using(new OptionalHeadRequestWrapper(context))
+            {
+                await context.WriteHalResponse(response);
+            }
         };
     }
 }

src/SqlStreamStore.HAL/ReadStreamMiddleware.cs

@@ -42,7 +42,10 @@ private static MidFunc GetStream(StreamResource stream) => next => async env =>
 
             var response = await stream.GetPage(options, context.Request.CallCancelled);
 
-            await context.WriteHalResponse(response);
+            using(new OptionalHeadRequestWrapper(context))
+            {
+                await context.WriteHalResponse(response);
+            }
         };
 
         private static MidFunc GetStreamMessage(StreamResource stream) => next => async env =>
@@ -62,7 +65,10 @@ private static MidFunc GetStreamMessage(StreamResource stream) => next => async
                 return;
             }
 
-            await context.WriteHalResponse(response);
+            using(new OptionalHeadRequestWrapper(context))
+            {
+                await context.WriteHalResponse(response);
+            }
         };
     }
 }