Adding instance-based CreateInvokableHttpClient

src/Dapr.Client/DaprClient.cs

@@ -58,7 +58,7 @@ public abstract class DaprClient : IDisposable
         /// The client will read the <see cref="HttpRequestMessage.RequestUri" /> property, and 
         /// interpret the hostname as the destination <c>app-id</c>. The <see cref="HttpRequestMessage.RequestUri" /> 
         /// property will be replaced with a new URI with the authority section replaced by <paramref name="daprEndpoint" />
-        /// and the path portion of the URI rewitten to follow the format of a Dapr service invocation request.
+        /// and the path portion of the URI rewritten to follow the format of a Dapr service invocation request.
         /// </para>
         /// </summary>
         /// <param name="appId">
@@ -448,6 +448,30 @@ public HttpRequestMessage CreateInvokeMethodRequest<TRequest>(string appId, stri
         /// <returns>A <see cref="Task{T}" /> that will return the value when the operation has completed.</returns>
         public abstract Task<HttpResponseMessage> InvokeMethodWithResponseAsync(HttpRequestMessage request, CancellationToken cancellationToken = default);
 
+#nullable enable
+        /// <summary>
+        /// <para>
+        /// Creates an <see cref="HttpClient"/> that can be used to perform Dapr service invocation using <see cref="HttpRequestMessage"/>
+        /// objects.
+        /// </para>
+        /// <para>
+        /// The client will read the <see cref="HttpRequestMessage.RequestUri" /> property, and 
+        /// interpret the hostname as the destination <c>app-id</c>. The <see cref="HttpRequestMessage.RequestUri" /> 
+        /// property will be replaced with a new URI with the authority section replaced by the HTTP endpoint value
+        /// and the path portion of the URI rewritten to follow the format of a Dapr service invocation request.
+        /// </para>
+        /// </summary>
+        /// <param name="appId">
+        ///     An optional <c>app-id</c>. If specified, the <c>app-id</c> will be configured as the value of 
+        ///     <see cref="HttpClient.BaseAddress" /> so that relative URIs can be used. It is mandatory to set this parameter if your app-id contains at least one upper letter.
+        ///     If some requests use absolute URL with an app-id which contains at least one upper letter, it will not work, the workaround is to create one HttpClient for each app-id with the app-ip parameter set.
+        /// </param>
+        /// <returns>An <see cref="HttpClient" /> that can be used to perform service invocation requests.</returns>
+        /// <remarks>
+        /// </remarks>
+        public abstract HttpClient CreateInvokableHttpClient(string? appId = null);
+#nullable disable
+
         /// <summary>
         /// Perform service invocation using the request provided by <paramref name="request" />. If the response has a non-success
         /// status an exception will be thrown.

src/Dapr.Client/DaprClientGrpc.cs

@@ -450,6 +450,66 @@ public override async Task<HttpResponseMessage> InvokeMethodWithResponseAsync(Ht
             }
         }
 
+        /// <summary>
+        /// <para>
+        /// Creates an <see cref="HttpClient"/> that can be used to perform Dapr service invocation using <see cref="HttpRequestMessage"/>
+        /// objects.
+        /// </para>
+        /// <para>
+        /// The client will read the <see cref="HttpRequestMessage.RequestUri" /> property, and 
+        /// interpret the hostname as the destination <c>app-id</c>. The <see cref="HttpRequestMessage.RequestUri" /> 
+        /// property will be replaced with a new URI with the authority section replaced by the instance's <see cref="httpEndpoint"/> value
+        /// and the path portion of the URI rewritten to follow the format of a Dapr service invocation request.
+        /// </para>
+        /// </summary>
+        /// <param name="appId">
+        ///     An optional <c>app-id</c>. If specified, the <c>app-id</c> will be configured as the value of 
+        ///     <see cref="HttpClient.BaseAddress" /> so that relative URIs can be used. It is mandatory to set this parameter if your app-id contains at least one upper letter.
+        ///     If some requests use absolute URL with an app-id which contains at least one upper letter, it will not work, the workaround is to create one HttpClient for each app-id with the app-ip parameter set.
+        /// </param>
+        /// <returns>An <see cref="HttpClient" /> that can be used to perform service invocation requests.</returns>
+        /// <remarks>
+        /// </remarks>
+        #nullable enable
+        public override HttpClient CreateInvokableHttpClient(string? appId = null)
+        {
+            var handler = new InvocationHandler
+            {
+                InnerHandler = new HttpClientHandler(),
+                DefaultAppId = appId
+            };
+
+            //Apply the Dapr API token if it's set on the client
+            if (this.apiTokenHeader.HasValue)
+            {
+                handler.DaprApiToken = this.apiTokenHeader.Value.Value;
+            }
+
+            if (this.httpEndpoint is not null)
+            {
+                //DaprEndpoint performs validation
+                handler.DaprEndpoint = this.httpEndpoint.AbsoluteUri;
+            }
+
+            var httpClient = new HttpClient(handler);
+            httpClient.DefaultRequestHeaders.UserAgent.Add(UserAgent());
+
+            if (appId is not null)
+            {
+                try
+                {
+                    httpClient.BaseAddress = new Uri($"http://{appId}");
+                }
+                catch (UriFormatException inner)
+                {
+                    throw new ArgumentException("The appId must be a valid hostname.", nameof(appId), inner);
+                }
+            }
+
+            return httpClient;
+        }
+        #nullable disable
+
         public async override Task InvokeMethodAsync(HttpRequestMessage request, CancellationToken cancellationToken = default)
         {
             ArgumentVerifier.ThrowIfNull(request, nameof(request));

test/Dapr.Client.Test/DaprClientTest.CreateInvokableHttpClientTest.cs

@@ -0,0 +1,52 @@
+// ------------------------------------------------------------------------
+// Copyright 2024 The Dapr Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//     http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// ------------------------------------------------------------------------
+
+using System;
+using Xunit;
+
+namespace Dapr.Client
+{
+    public partial class DaprClientTest
+    {
+        [Fact]
+        public void CreateInvokableHttpClient_WithAppId_FromDaprClient()
+        {
+            var daprClient = new MockClient().DaprClient;
+            var client = daprClient.CreateInvokableHttpClient(appId: "bank");
+            Assert.Equal("http://bank/", client.BaseAddress.AbsoluteUri);
+        }
+
+        [Fact]
+        public void CreateInvokableHttpClient_InvalidAppId_FromDaprClient()
+        {
+            var daprClient = new MockClient().DaprClient;
+            var ex = Assert.Throws<ArgumentException>(() =>
+            {
+                // The appId needs to be something that can be used as hostname in a URI.
+                _ = daprClient.CreateInvokableHttpClient(appId: "");
+            });
+
+            Assert.Contains("The appId must be a valid hostname.", ex.Message);
+            Assert.IsType<UriFormatException>(ex.InnerException);
+        }
+
+        [Fact]
+        public void CreateInvokableHttpClient_WithoutAppId_FromDaprClient()
+        {
+            var daprClient = new MockClient().DaprClient;
+
+            var client = daprClient.CreateInvokableHttpClient();
+            Assert.Null(client.BaseAddress);
+        }
+    }
+}