Add C# client-side interceptor machinery

src/csharp/Grpc.Core/ClientBase.cs

@@ -16,6 +16,8 @@
 
 #endregion
 
+using System;
+using Grpc.Core.Interceptors;
 using Grpc.Core.Internal;
 using Grpc.Core.Utils;
 
@@ -147,6 +149,64 @@ namespace Grpc.Core
         /// </summary>
         protected internal class ClientBaseConfiguration
         {
+            private class ClientHeaderInterceptor : Interceptor
+            {
+                readonly Func<IMethod, string, CallOptions, Tuple<string, CallOptions>> interceptor;
+
+                /// <summary>
+                /// Creates a new instance of ClientHeaderInterceptor given the specified header interceptor function.
+                /// </summary>
+                public ClientHeaderInterceptor(Func<IMethod, string, CallOptions, Tuple<string, CallOptions>> interceptor)
+                {
+                    this.interceptor = GrpcPreconditions.CheckNotNull(interceptor, "interceptor");
+                }
+
+                /// <summary>
+                /// Intercepts a blocking invocation of a simple remote call.
+                /// </summary>
+                public override TResponse BlockingUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, BlockingUnaryCallContinuation<TRequest, TResponse> continuation)
+                {
+                    var newHeaders = interceptor(context.Method, context.Host, context.Options);
+                    return continuation(request, new ClientInterceptorContext<TRequest, TResponse>(context.Method, newHeaders.Item1, newHeaders.Item2));
+                }
+
+                /// <summary>
+                /// Intercepts an asynchronous invocation of a simple remote call.
+                /// </summary>
+                public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
+                {
+                    var newHeaders = interceptor(context.Method, context.Host, context.Options);
+                    return continuation(request, new ClientInterceptorContext<TRequest, TResponse>(context.Method, newHeaders.Item1, newHeaders.Item2));
+                }
+
+                /// <summary>
+                /// Intercepts an asynchronous invocation of a streaming remote call.
+                /// </summary>
+                public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncServerStreamingCallContinuation<TRequest, TResponse> continuation)
+                {
+                    var newHeaders = interceptor(context.Method, context.Host, context.Options);
+                    return continuation(request, new ClientInterceptorContext<TRequest, TResponse>(context.Method, newHeaders.Item1, newHeaders.Item2));
+                }
+
+                /// <summary>
+                /// Intercepts an asynchronous invocation of a client streaming call.
+                /// </summary>
+                public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncClientStreamingCallContinuation<TRequest, TResponse> continuation)
+                {
+                    var newHeaders = interceptor(context.Method, context.Host, context.Options);
+                    return continuation(new ClientInterceptorContext<TRequest, TResponse>(context.Method, newHeaders.Item1, newHeaders.Item2));
+                }
+
+                /// <summary>
+                /// Intercepts an asynchronous invocation of a duplex streaming call.
+                /// </summary>
+                public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncDuplexStreamingCallContinuation<TRequest, TResponse> continuation)
+                {
+                    var newHeaders = interceptor(context.Method, context.Host, context.Options);
+                    return continuation(new ClientInterceptorContext<TRequest, TResponse>(context.Method, newHeaders.Item1, newHeaders.Item2));
+                }
+            }
+
             readonly CallInvoker undecoratedCallInvoker;
             readonly string host;
 
@@ -158,7 +218,7 @@ namespace Grpc.Core
 
             internal CallInvoker CreateDecoratedCallInvoker()
             {
-                return new InterceptingCallInvoker(undecoratedCallInvoker, hostInterceptor: (h) => host);
+                return undecoratedCallInvoker.Intercept(new ClientHeaderInterceptor((method, host, options) => Tuple.Create(this.host, options)));
             }
 
             internal ClientBaseConfiguration WithHost(string host)

src/csharp/Grpc.Core/Interceptors/CallInvokerExtensions.cs

@@ -0,0 +1,137 @@
+#region Copyright notice and license
+
+// Copyright 2018 gRPC 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.
+
+#endregion
+
+using System;
+using System.Linq;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core.Interceptors
+{
+    /// <summary>
+    /// Extends the CallInvoker class to provide the interceptor facility on the client side.
+    /// This is an EXPERIMENTAL API.
+    /// </summary>
+    public static class CallInvokerExtensions
+    {
+        /// <summary>
+        /// Decorates an underlying <see cref="Grpc.Core.CallInvoker" /> to
+        /// intercept calls through a given interceptor.
+        /// </summary>
+        private class InterceptingCallInvoker : CallInvoker
+        {
+            readonly CallInvoker invoker;
+            readonly Interceptor interceptor;
+
+            /// <summary>
+            /// Creates a new instance of <see cref="Grpc.Core.Interceptors.CallInvokerExtensions.InterceptingCallInvoker" />
+            /// with the given underlying invoker and interceptor instances.
+            /// </summary>
+            public InterceptingCallInvoker(CallInvoker invoker, Interceptor interceptor)
+            {
+                this.invoker = GrpcPreconditions.CheckNotNull(invoker, "invoker");
+                this.interceptor = GrpcPreconditions.CheckNotNull(interceptor, "interceptor");
+            }
+
+            /// <summary>
+            /// Intercepts a simple blocking call with the registered interceptor.
+            /// </summary>
+            public override TResponse BlockingUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+            {
+                return interceptor.BlockingUnaryCall(
+                    request,
+                    new ClientInterceptorContext<TRequest, TResponse>(method, host, options),
+                    (req, ctx) => invoker.BlockingUnaryCall(ctx.Method, ctx.Host, ctx.Options, req));
+            }
+
+            /// <summary>
+            /// Intercepts a simple asynchronous call with the registered interceptor.
+            /// </summary>
+            public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+            {
+                return interceptor.AsyncUnaryCall(
+                    request,
+                    new ClientInterceptorContext<TRequest, TResponse>(method, host, options),
+                    (req, ctx) => invoker.AsyncUnaryCall(ctx.Method, ctx.Host, ctx.Options, req));
+            }
+
+            /// <summary>
+            /// Intercepts an asynchronous server streaming call with the registered interceptor.
+            /// </summary>
+            public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
+            {
+                return interceptor.AsyncServerStreamingCall(
+                    request,
+                    new ClientInterceptorContext<TRequest, TResponse>(method, host, options),
+                    (req, ctx) => invoker.AsyncServerStreamingCall(ctx.Method, ctx.Host, ctx.Options, req));
+            }
+
+            /// <summary>
+            /// Intercepts an asynchronous client streaming call with the registered interceptor.
+            /// </summary>
+            public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+            {
+                return interceptor.AsyncClientStreamingCall(
+                    new ClientInterceptorContext<TRequest, TResponse>(method, host, options),
+                    ctx => invoker.AsyncClientStreamingCall(ctx.Method, ctx.Host, ctx.Options));
+            }
+
+            /// <summary>
+            /// Intercepts an asynchronous duplex streaming call with the registered interceptor.
+            /// </summary>
+            public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
+            {
+                return interceptor.AsyncDuplexStreamingCall(
+                    new ClientInterceptorContext<TRequest, TResponse>(method, host, options),
+                    ctx => invoker.AsyncDuplexStreamingCall(ctx.Method, ctx.Host, ctx.Options));
+            }
+        }
+
+        /// <summary>
+        /// Returns a <see cref="Grpc.Core.CallInvoker" /> instance that intercepts
+        /// the invoker with the given interceptor.
+        /// </summary>
+        /// <param name="invoker">The underlying invoker to intercept.</param>
+        /// <param name="interceptor">The interceptor to intercept calls to the invoker with.</param>
+        public static CallInvoker Intercept(this CallInvoker invoker, Interceptor interceptor)
+        {
+            return new InterceptingCallInvoker(invoker, interceptor);
+        }
+
+        /// <summary>
+        /// Returns a <see cref="Grpc.Core.CallInvoker" /> instance that intercepts
+        /// the invoker with the given interceptors.
+        /// </summary>
+        /// <param name="invoker">The channel to intercept.</param>
+        /// <param name="interceptors">
+        /// An array of interceptors to intercept the calls to the invoker with.
+        /// Control is passed to the interceptors in the order specified.
+        /// </param>
+        public static CallInvoker Intercept(this CallInvoker invoker, params Interceptor[] interceptors)
+        {
+            GrpcPreconditions.CheckNotNull(invoker, "invoker");
+            GrpcPreconditions.CheckNotNull(interceptors, "interceptors");
+
+            foreach (var interceptor in interceptors.Reverse())
+            {
+                invoker = Intercept(invoker, interceptor);
+            }
+
+            return invoker;
+        }
+    }
+}

src/csharp/Grpc.Core/Interceptors/ChannelExtensions.cs

@@ -0,0 +1,54 @@
+#region Copyright notice and license
+
+// Copyright 2018 gRPC 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.
+
+#endregion
+
+using System;
+
+namespace Grpc.Core.Interceptors
+{
+    /// <summary>
+    /// Provides extension methods to make it easy to register interceptors on Channel objects.
+    /// This is an EXPERIMENTAL API.
+    /// </summary>
+    public static class ChannelExtensions
+    {
+        /// <summary>
+        /// Returns a <see cref="Grpc.Core.CallInvoker" /> instance that intercepts
+        /// the channel with the given interceptor.
+        /// </summary>
+        /// <param name="channel">The channel to intercept.</param>
+        /// <param name="interceptor">The interceptor to intercept the channel with.</param>
+        public static CallInvoker Intercept(this Channel channel, Interceptor interceptor)
+        {
+            return new DefaultCallInvoker(channel).Intercept(interceptor);
+        }
+
+        /// <summary>
+        /// Returns a <see cref="Grpc.Core.CallInvoker" /> instance that intercepts
+        /// the channel with the given interceptors.
+        /// </summary>
+        /// <param name="channel">The channel to intercept.</param>
+        /// <param name="interceptors">
+        /// An array of interceptors to intercept the channel with.
+        /// Control is passed to the interceptors in the order specified.
+        /// </param>
+        public static CallInvoker Intercept(this Channel channel, params Interceptor[] interceptors)
+        {
+            return new DefaultCallInvoker(channel).Intercept(interceptors);
+        }
+    }
+}

src/csharp/Grpc.Core/Internal/InterceptingCallInvoker.cs

@@ -1,119 +0,0 @@
-#region Copyright notice and license
-
-// Copyright 2015-2016 gRPC 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.
-
-#endregion
-
-using System;
-using System.Threading.Tasks;
-using Grpc.Core;
-using Grpc.Core.Utils;
-
-namespace Grpc.Core.Internal
-{
-    /// <summary>
-    /// Decorates an underlying <c>CallInvoker</c> to intercept call invocations.
-    /// </summary>
-    internal class InterceptingCallInvoker : CallInvoker
-    {
-        readonly CallInvoker callInvoker;
-        readonly Func<string, string> hostInterceptor;
-        readonly Func<CallOptions, CallOptions> callOptionsInterceptor;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="Grpc.Core.Internal.InterceptingCallInvoker"/> class.
-        /// </summary>
-        public InterceptingCallInvoker(CallInvoker callInvoker,
-            Func<string, string> hostInterceptor = null,
-            Func<CallOptions, CallOptions> callOptionsInterceptor = null)
-        {
-            this.callInvoker = GrpcPreconditions.CheckNotNull(callInvoker);
-            this.hostInterceptor = hostInterceptor;
-            this.callOptionsInterceptor = callOptionsInterceptor;
-        }
-
-        /// <summary>
-        /// Intercepts a unary call.
-        /// </summary>
-        public override TResponse BlockingUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
-        {
-            host = InterceptHost(host);
-            options = InterceptCallOptions(options);
-            return callInvoker.BlockingUnaryCall(method, host, options, request);
-        }
-
-        /// <summary>
-        /// Invokes a simple remote call asynchronously.
-        /// </summary>
-        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
-        {
-            host = InterceptHost(host);
-            options = InterceptCallOptions(options);
-            return callInvoker.AsyncUnaryCall(method, host, options, request);
-        }
-
-        /// <summary>
-        /// Invokes a server streaming call asynchronously.
-        /// In server streaming scenario, client sends on request and server responds with a stream of responses.
-        /// </summary>
-        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
-        {
-            host = InterceptHost(host);
-            options = InterceptCallOptions(options);
-            return callInvoker.AsyncServerStreamingCall(method, host, options, request);
-        }
-
-        /// <summary>
-        /// Invokes a client streaming call asynchronously.
-        /// In client streaming scenario, client sends a stream of requests and server responds with a single response.
-        /// </summary>
-        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
-        {
-            host = InterceptHost(host);
-            options = InterceptCallOptions(options);
-            return callInvoker.AsyncClientStreamingCall(method, host, options);
-        }
-
-        /// <summary>
-        /// Invokes a duplex streaming call asynchronously.
-        /// In duplex streaming scenario, client sends a stream of requests and server responds with a stream of responses.
-        /// The response stream is completely independent and both side can be sending messages at the same time.
-        /// </summary>
-        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
-        {
-            host = InterceptHost(host);
-            options = InterceptCallOptions(options);
-            return callInvoker.AsyncDuplexStreamingCall(method, host, options);
-        }
-
-        private string InterceptHost(string host)
-        {
-            if (hostInterceptor == null)
-            {
-                return host;
-            }
-            return hostInterceptor(host);
-        }
-
-        private CallOptions InterceptCallOptions(CallOptions options)
-        {
-            if (callOptionsInterceptor == null)
-            {
-                return options;
-            }
-            return callOptionsInterceptor(options);
-        }
-    }
-}