Remove unnecessary inheritance for HttpContent

Signed-off-by: Jon Skeet <jonskeet@google.com>

samples/HttpSend/Program.cs

@@ -41,7 +41,7 @@ namespace HttpSend
                 Data = JsonConvert.SerializeObject("hey there!")
             };
 
-            var content = new CloudEventHttpContent(cloudEvent, ContentMode.Structured, new JsonEventFormatter());
+            var content = cloudEvent.ToHttpContent(ContentMode.Structured, new JsonEventFormatter());
 
             var httpClient = new HttpClient();
             // your application remains in charge of adding any further headers or 

src/CloudNative.CloudEvents/Http/CloudEventHttpContent.cs

@@ -1,110 +0,0 @@
-// Copyright (c) Cloud Native Foundation.
-// Licensed under the Apache 2.0 license.
-// See LICENSE file in the project root for full license information.
-
-using System;
-using System.IO;
-using System.Net;
-using System.Net.Http;
-using System.Net.Mime;
-using System.Threading.Tasks;
-
-namespace CloudNative.CloudEvents.Http
-{
-    // TODO: Do we really need to have a subclass here? How about a static factory method instead?
-
-    /// <summary>
-    /// This class is for use with `HttpClient` and constructs content and headers for
-    /// a HTTP request from a CloudEvent.
-    /// </summary>
-    public class CloudEventHttpContent : HttpContent
-    {
-        private readonly InnerByteArrayContent inner;                      
-
-        /// <summary>
-        /// Constructor
-        /// </summary>
-        /// <param name="cloudEvent">CloudEvent</param>
-        /// <param name="contentMode">Content mode. Structured or binary.</param>
-        /// <param name="formatter">Event formatter</param>
-        public CloudEventHttpContent(CloudEvent cloudEvent, ContentMode contentMode, CloudEventFormatter formatter)
-        {
-            byte[] content;
-            ContentType contentType;
-            switch (contentMode)
-            {
-                case ContentMode.Structured:
-                    content = formatter.EncodeStructuredModeMessage(cloudEvent, out contentType);
-                    // This is optional in the specification, but can be useful.
-                    MapHeaders(cloudEvent, includeDataContentType: true);
-                    break;
-                case ContentMode.Binary:
-                    content = formatter.EncodeBinaryModeEventData(cloudEvent);
-                    contentType = MimeUtilities.CreateContentTypeOrNull(cloudEvent.DataContentType);
-                    MapHeaders(cloudEvent, includeDataContentType: false);
-                    break;
-                default:
-                    throw new ArgumentException($"Unsupported content mode: {contentMode}");
-
-            }
-            inner = new InnerByteArrayContent(content);
-            if (contentType is object)
-            {
-                Headers.ContentType = contentType.ToMediaTypeHeaderValue();
-            }
-            else if (content.Length != 0)
-            {
-                throw new ArgumentException(Strings.ErrorContentTypeUnspecified, nameof(cloudEvent));
-            }
-        }
-
-        protected override Task SerializeToStreamAsync(Stream stream, TransportContext context) =>
-            inner.InnerSerializeToStreamAsync(stream, context);
-
-        protected override bool TryComputeLength(out long length) =>
-            inner.InnerTryComputeLength(out length);
-
-        private void MapHeaders(CloudEvent cloudEvent, bool includeDataContentType)
-        {
-            Headers.Add(HttpUtilities.SpecVersionHttpHeader, HttpUtilities.EncodeHeaderValue(cloudEvent.SpecVersion.VersionId));
-            foreach (var attributeAndValue in cloudEvent.GetPopulatedAttributes())
-            {
-                CloudEventAttribute attribute = attributeAndValue.Key;
-                string headerName = HttpUtilities.HttpHeaderPrefix + attribute.Name;
-                object value = attributeAndValue.Value;
-
-                // Only map the data content type attribute to a header if we've been asked to
-                if (attribute == cloudEvent.SpecVersion.DataContentTypeAttribute && !includeDataContentType)
-                {
-                    continue;
-                }
-                else
-                {
-                    string headerValue = HttpUtilities.EncodeHeaderValue(attribute.Format(value));
-                    Headers.Add(headerName, headerValue);
-                }
-            }
-        }
-
-        /// <summary>
-        /// This inner class is required to get around the 'protected'-ness of the
-        /// override functions of HttpContent for enabling containment/delegation
-        /// </summary>
-        class InnerByteArrayContent : ByteArrayContent
-        {
-            public InnerByteArrayContent(byte[] content) : base(content)
-            {
-            }
-
-            public Task InnerSerializeToStreamAsync(Stream stream, TransportContext context)
-            {
-                return base.SerializeToStreamAsync(stream, context);
-            }
-
-            public bool InnerTryComputeLength(out long length)
-            {
-                return base.TryComputeLength(out length);
-            }
-        }
-    }
-}

src/CloudNative.CloudEvents/Http/HttpContentExtensions.cs

@@ -0,0 +1,73 @@
+// Copyright 2021 Cloud Native Foundation.
+// Licensed under the Apache 2.0 license.
+// See LICENSE file in the project root for full license information.
+
+using System;
+using System.Net.Http;
+using System.Net.Mime;
+
+namespace CloudNative.CloudEvents.Http
+{
+    /// <summary>
+    /// CloudEvent extension methods related to <see cref="HttpContent"/>.
+    /// </summary>
+    public static class HttpContentExtensions
+    {
+        /// <summary>
+        /// Converts a CloudEvent to <see cref="HttpContent"/>.
+        /// </summary>
+        /// <param name="cloudEvent">CloudEvent</param>
+        /// <param name="contentMode">Content mode. Structured or binary.</param>
+        /// <param name="formatter">Event formatter</param>
+        public static HttpContent ToHttpContent(this CloudEvent cloudEvent, ContentMode contentMode, CloudEventFormatter formatter)
+        {
+            byte[] content;
+            // The content type to include in the ContentType header - may be the data content type, or the formatter's content type.
+            ContentType contentType;
+            switch (contentMode)
+            {
+                case ContentMode.Structured:
+                    content = formatter.EncodeStructuredModeMessage(cloudEvent, out contentType);
+                    break;
+                case ContentMode.Binary:
+                    content = formatter.EncodeBinaryModeEventData(cloudEvent);
+                    contentType = MimeUtilities.CreateContentTypeOrNull(cloudEvent.DataContentType);
+                    break;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(contentMode), $"Unsupported content mode: {contentMode}");
+            }
+            var ret = new ByteArrayContent(content);
+            if (contentType is object)
+            {
+                ret.Headers.ContentType = contentType.ToMediaTypeHeaderValue();
+            }
+            else if (content.Length != 0)
+            {
+                throw new ArgumentException(Strings.ErrorContentTypeUnspecified, nameof(cloudEvent));
+            }
+
+            // Map headers in either mode.
+            // Including the headers in structured mode is optional in the spec (as they're already within the body) but
+            // can be useful.
+            ret.Headers.Add(HttpUtilities.SpecVersionHttpHeader, HttpUtilities.EncodeHeaderValue(cloudEvent.SpecVersion.VersionId));
+            foreach (var attributeAndValue in cloudEvent.GetPopulatedAttributes())
+            {
+                CloudEventAttribute attribute = attributeAndValue.Key;
+                string headerName = HttpUtilities.HttpHeaderPrefix + attribute.Name;
+                object value = attributeAndValue.Value;
+
+                // Skip the data content type attribute in binary mode, because it's already in the content type header.
+                if (attribute == cloudEvent.SpecVersion.DataContentTypeAttribute && contentMode == ContentMode.Binary)
+                {
+                    continue;
+                }
+                else
+                {
+                    string headerValue = HttpUtilities.EncodeHeaderValue(attribute.Format(value));
+                    ret.Headers.Add(headerName, headerValue);
+                }
+            }
+            return ret;
+        }
+    }
+}

test/CloudNative.CloudEvents.IntegrationTests/AspNetCore/CloudEventControllerTests.cs

@@ -40,7 +40,7 @@ namespace CloudNative.CloudEvents.IntegrationTests.AspNetCore
                 [expectedExtensionKey] = expectedExtensionValue
             };
 
-            var httpContent = new CloudEventHttpContent(cloudEvent, contentMode, new JsonEventFormatter());
+            var httpContent = cloudEvent.ToHttpContent(contentMode, new JsonEventFormatter());
 
             // Act
             var result = await _factory.CreateClient().PostAsync("/api/events/receive", httpContent);

test/CloudNative.CloudEvents.UnitTests/Http/HttpClientExtensionsTest.cs

@@ -95,7 +95,7 @@ namespace CloudNative.CloudEvents.Http.UnitTests
             };
 
             string ctx = Guid.NewGuid().ToString();
-            var content = new CloudEventHttpContent(cloudEvent, ContentMode.Binary, new JsonEventFormatter());
+            var content = cloudEvent.ToHttpContent(ContentMode.Binary, new JsonEventFormatter());
             content.Headers.Add(TestContextHeader, ctx);
 
             PendingRequests.TryAdd(ctx, context =>
@@ -215,7 +215,7 @@ namespace CloudNative.CloudEvents.Http.UnitTests
             };
 
             string ctx = Guid.NewGuid().ToString();
-            var content = new CloudEventHttpContent(cloudEvent, ContentMode.Structured, new JsonEventFormatter());
+            var content = cloudEvent.ToHttpContent(ContentMode.Structured, new JsonEventFormatter());
             content.Headers.Add(TestContextHeader, ctx);
 
             PendingRequests.TryAdd(ctx, context =>

test/CloudNative.CloudEvents.UnitTests/Http/HttpContentExtensionsTest.cs

@@ -6,17 +6,18 @@ using CloudNative.CloudEvents.NewtonsoftJson;
 using System;
 using System.Net.Http.Headers;
 using Xunit;
+using static CloudNative.CloudEvents.UnitTests.TestHelpers;
 
 namespace CloudNative.CloudEvents.Http.UnitTests
 {
-    public class CloudEventHttpContentTest
+    public class HttpContentExtensionsTest
     {
         [Fact]
         public void ContentType_FromCloudEvent_BinaryMode()
         {
-            var cloudEvent = CreateEmptyCloudEvent();
+            var cloudEvent = new CloudEvent().PopulateRequiredAttributes();
             cloudEvent.DataContentType = "text/plain";
-            var content = new CloudEventHttpContent(cloudEvent, ContentMode.Binary, new JsonEventFormatter());
+            var content = cloudEvent.ToHttpContent(ContentMode.Binary, new JsonEventFormatter());
             var expectedContentType = new MediaTypeHeaderValue("text/plain");
             Assert.Equal(expectedContentType, content.Headers.ContentType);
         }
@@ -27,26 +28,18 @@ namespace CloudNative.CloudEvents.Http.UnitTests
         [Fact]
         public void NoContentType_NoContent()
         {
-            var cloudEvent = CreateEmptyCloudEvent();
+            var cloudEvent = new CloudEvent().PopulateRequiredAttributes();
-            var content = new CloudEventHttpContent(cloudEvent, ContentMode.Binary, new JsonEventFormatter());
+            var content = cloudEvent.ToHttpContent(ContentMode.Binary, new JsonEventFormatter());
             Assert.Null(content.Headers.ContentType);
         }
 
         [Fact]
         public void NoContentType_WithContent()
         {
-            var cloudEvent = CreateEmptyCloudEvent();
+            var cloudEvent = new CloudEvent().PopulateRequiredAttributes();
             cloudEvent.Data = "Some text";
-            var exception = Assert.Throws<ArgumentException>(() => new CloudEventHttpContent(cloudEvent, ContentMode.Binary, new JsonEventFormatter()));
+            var exception = Assert.Throws<ArgumentException>(() => cloudEvent.ToHttpContent(ContentMode.Binary, new JsonEventFormatter()));
             Assert.StartsWith(Strings.ErrorContentTypeUnspecified, exception.Message);
         }
-
-        private static CloudEvent CreateEmptyCloudEvent() =>
-            new CloudEvent
-            { 
-                Type = "type",
-                Source = new Uri("https://source"),
-                Id = "id"
-            };
     }
 }