only accept hal json

Author: thefringeninja

src/SqlStreamStore.HAL.Tests/AcceptHeaderTests.cs

@@ -0,0 +1,58 @@
+namespace SqlStreamStore.HAL.Tests
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Net;
+    using System.Net.Http;
+    using System.Net.Http.Headers;
+    using System.Threading.Tasks;
+    using Shouldly;
+    using Xunit;
+
+    public class AcceptHeaderTests : IDisposable
+    {
+        private readonly SqlStreamStoreHalMiddlewareFixture _fixture;
+
+        public AcceptHeaderTests()
+        {
+            _fixture = new SqlStreamStoreHalMiddlewareFixture();
+        }
+
+        public static IEnumerable<object[]> NotAcceptableCases()
+        {
+            var requestUris = new[] { "/stream", "/streams/a-stream", "/" };
+            var methods = new[]
+            {
+                HttpMethod.Get, 
+                HttpMethod.Head, 
+                HttpMethod.Options, 
+                HttpMethod.Post,
+                HttpMethod.Delete
+            };
+            var mediaTypes = new[] { "text/html", "application/hal", "application/hal+xml" };
+
+            return from requestUri in requestUris
+                from method in methods
+                from mediaType in mediaTypes
+                select new object[] { requestUri, method, new MediaTypeWithQualityHeaderValue(mediaType) };
+        }
+
+        [Theory, MemberData(nameof(NotAcceptableCases))]
+        public async Task accept_other_than_hal_json_are_not_acceptable(
+            string requestUri,
+            HttpMethod method,
+            MediaTypeWithQualityHeaderValue mediaType)
+        {
+            using(var response = await _fixture.HttpClient.SendAsync(new HttpRequestMessage(method, requestUri)
+            {
+                Headers = { Accept = { mediaType } }
+            }))
+            {
+                response.StatusCode.ShouldBe(HttpStatusCode.NotAcceptable);
+            }
+        }
+
+        public void Dispose() => _fixture.Dispose();
+    }
+}

src/SqlStreamStore.HAL/Constants.cs

@@ -14,6 +14,7 @@ public static class ContentTypes
             {
                 public const string Json = "application/json";
                 public const string HalJson = "application/hal+json";
+                public const string Any = "*/*";
             }
         }
 

src/SqlStreamStore.HAL/SqlStreamStoreHalMiddleware.cs

@@ -2,6 +2,7 @@
 {
     using System;
     using System.Linq;
+    using System.Net.Http.Headers;
     using System.Threading.Tasks;
     using Halcyon.HAL;
     using Microsoft.Owin;
@@ -49,6 +50,29 @@ public static class SqlStreamStoreHalMiddleware
             return next(env);
         };
 
+
+        private static MidFunc AcceptOnlyHalJson => next => env =>
+        {
+            var context = new OwinContext(env);
+
+            var accept = context.Request.Accept?.Split(',')
+                                 .Select(value => MediaTypeWithQualityHeaderValue.TryParse(value, out var header)
+                                     ? header.MediaType
+                                     : null)
+                             ?? Enumerable.Empty<string>();
+
+            return accept.Any(header => header == Constants.Headers.ContentTypes.HalJson
+                                        || header == Constants.Headers.ContentTypes.Any)
+                ? next(env)
+                : context.WriteHalResponse(new Response(new HALResponse(new
+                    {
+                        type = "Not Acceptable",
+                        title = "Not Acceptable",
+                        detail = $"The server only understands {Constants.Headers.ContentTypes.HalJson}."
+                    }),
+                    406));
+        };
+
         private static MidFunc Index => next => env =>
         {
             var context = new OwinContext(env);
@@ -72,6 +96,7 @@ public static MidFunc UseSqlStreamStoreHal(IStreamStore streamStore)
                 .Use(ExceptionHandlingMiddleware.HandleExceptions)
                 .Use(AccessControl)
                 .Use(AddReasonPhrase)
+                .Use(AcceptOnlyHalJson)
                 .Use(Index)
                 .Map("/stream", inner => inner
                     .Use(ReadAllStreamMiddleware.UseStreamStore(streamStore))