Add GenericInterceptor to help writing client interceptors

1 files changed, 325 insertions, 0 deletions

diff --git a/src/csharp/Grpc.Core/Interceptors/GenericInterceptor.cs b/src/csharp/Grpc.Core/Interceptors/GenericInterceptor.cs
new file mode 100644
index 0000000000..b9fc5e0a19
--- /dev/null
+++ b/src/csharp/Grpc.Core/Interceptors/GenericInterceptor.cs
@@ -0,0 +1,325 @@
+#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.Threading;
+using System.Threading.Tasks;
+using Grpc.Core.Internal;
+
+namespace Grpc.Core.Interceptors
+{
+    /// <summary>
+    /// Provides a base class for generic interceptor implementations that raises
+    /// events and hooks to control the RPC lifecycle.
+    /// </summary>
+    public abstract class GenericInterceptor : Interceptor
+    {
+
+        /// <summary>
+        /// Provides hooks through which an invocation should be intercepted.
+        /// </summary>
+        public sealed class ClientCallArbitrator<TRequest, TResponse>
+            where TRequest : class
+            where TResponse : class
+        {
+            internal ClientCallArbitrator<TRequest, TResponse> Freeze()
+            {
+                return (ClientCallArbitrator<TRequest, TResponse>)MemberwiseClone();
+            }
+            /// <summary>
+            /// Override the context for the outgoing invocation.
+            /// </summary>
+            public ClientInterceptorContext<TRequest, TResponse> Context { get; set; }
+            /// <summary>
+            /// Override the request for the outgoing invocation for non-client-streaming invocations.
+            /// </summary>
+            public TRequest UnaryRequest { get; set; }
+            /// <summary>
+            /// Delegate that intercepts a response from a non-server-streaming invocation and optionally overrides it.
+            /// </summary>
+            public Func<TResponse, TResponse> OnUnaryResponse { get; set; }
+            /// <summary>
+            /// Delegate that intercepts each request message for a client-streaming invocation and optionally overrides each message.
+            /// </summary>
+            public Func<TRequest, TRequest> OnRequestMessage { get; set; }
+            /// <summary>
+            /// Delegate that intercepts each response message for a server-streaming invocation and optionally overrides each message.
+            /// </summary>
+            public Func<TResponse, TResponse> OnResponseMessage { get; set; }
+            /// <summary>
+            /// Callback that gets invoked when response stream is finished.
+            /// </summary>
+            public Action OnResponseStreamEnd { get; set; }
+            /// <summary>
+            /// Callback that gets invoked when request stream is finished.
+            /// </summary>
+            public Action OnRequestStreamEnd { get; set; }
+        }
+
+        /// <summary>
+        /// Intercepts an outgoing call from the client side.
+        /// Derived classes that intend to intercept outgoing invocations from the client side should
+        /// override this and return the appropriate hooks in the form of a ClientCallArbitrator instance.
+        /// </summary>
+        /// <param name="context">The context of the outgoing invocation.</param>
+        /// <param name="clientStreaming">True if the invocation is client-streaming.</param>
+        /// <param name="serverStreaming">True if the invocation is server-streaming.</param>
+        /// <param name="request">The request message for client-unary invocations, null otherwise.</param>
+        /// <typeparam name="TRequest">Request message type for the current invocation.</typeparam>
+        /// <typeparam name="TResponse">Response message type for the current invocation.</typeparam>
+        /// <returns>
+        /// The derived class should return an instance of ClientCallArbitrator to control the trajectory
+        /// as they see fit, or null if it does not intend to pursue the invocation any further.
+        /// </returns>
+        protected virtual ClientCallArbitrator<TRequest, TResponse> InterceptCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, bool clientStreaming, bool serverStreaming, TRequest request)
+            where TRequest : class
+            where TResponse : class
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Intercepts a blocking invocation of a simple remote call and dispatches the events accordingly.
+        /// </summary>
+        public override TResponse BlockingUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, BlockingUnaryCallContinuation<TRequest, TResponse> continuation)
+        {
+            var arbitrator = InterceptCall(context, false, false, request)?.Freeze();
+            context = arbitrator?.Context ?? context;
+            request = arbitrator?.UnaryRequest ?? request;
+            var response = continuation(request, context);
+            if (arbitrator?.OnUnaryResponse != null)
+            {
+                response = arbitrator.OnUnaryResponse(response);
+            }
+            return response;
+        }
+
+        /// <summary>
+        /// Intercepts an asynchronous invocation of a simple remote call and dispatches the events accordingly.
+        /// </summary>
+        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
+        {
+            var arbitrator = InterceptCall(context, false, false, request)?.Freeze();
+            context = arbitrator?.Context ?? context;
+            request = arbitrator?.UnaryRequest ?? request;
+            var response = continuation(request, context);
+            if (arbitrator?.OnUnaryResponse != null)
+            {
+                response = new AsyncUnaryCall<TResponse>(response.ResponseAsync.ContinueWith(unaryResponse => arbitrator.OnUnaryResponse(unaryResponse.Result)),
+                    response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
+            }
+            return response;
+        }
+
+        /// <summary>
+        /// Intercepts an asynchronous invocation of a streaming remote call and dispatches the events accordingly.
+        /// </summary>
+        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncServerStreamingCallContinuation<TRequest, TResponse> continuation)
+        {
+            var arbitrator = InterceptCall(context, false, true, request)?.Freeze();
+            context = arbitrator?.Context ?? context;
+            request = arbitrator?.UnaryRequest ?? request;
+            var response = continuation(request, context);
+            if (arbitrator?.OnResponseMessage != null || arbitrator?.OnResponseStreamEnd != null)
+            {
+                response = new AsyncServerStreamingCall<TResponse>(
+                    new WrappedClientStreamReader<TResponse>(response.ResponseStream, arbitrator.OnResponseMessage, arbitrator.OnResponseStreamEnd),
+                    response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
+            }
+            return response;
+        }
+
+        /// <summary>
+        /// Intercepts an asynchronous invocation of a client streaming call and dispatches the events accordingly.
+        /// </summary>
+        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncClientStreamingCallContinuation<TRequest, TResponse> continuation)
+        {
+            var arbitrator = InterceptCall(context, true, false, null)?.Freeze();
+            context = arbitrator?.Context ?? context;
+            var response = continuation(context);
+            if (arbitrator?.OnRequestMessage != null || arbitrator?.OnResponseStreamEnd != null || arbitrator?.OnUnaryResponse != null)
+            {
+                var requestStream = response.RequestStream;
+                if (arbitrator?.OnRequestMessage != null || arbitrator?.OnRequestStreamEnd != null)
+                {
+                    requestStream = new WrappedClientStreamWriter<TRequest>(response.RequestStream, arbitrator.OnRequestMessage, arbitrator.OnRequestStreamEnd);
+                }
+                var responseAsync = response.ResponseAsync;
+                if (arbitrator?.OnUnaryResponse != null)
+                {
+                    responseAsync = response.ResponseAsync.ContinueWith(unaryResponse => arbitrator.OnUnaryResponse(unaryResponse.Result));
+                }
+                response = new AsyncClientStreamingCall<TRequest, TResponse>(requestStream, responseAsync, response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
+            }
+            return response;
+        }
+
+        /// <summary>
+        /// Intercepts an asynchronous invocation of a duplex streaming call and dispatches the events accordingly.
+        /// </summary>
+        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncDuplexStreamingCallContinuation<TRequest, TResponse> continuation)
+        {
+            var arbitrator = InterceptCall(context, true, true, null)?.Freeze();
+            context = arbitrator?.Context ?? context;
+            var response = continuation(context);
+            if (arbitrator?.OnRequestMessage != null || arbitrator?.OnRequestStreamEnd != null || arbitrator?.OnResponseMessage != null || arbitrator?.OnResponseStreamEnd != null)
+            {
+                var requestStream = response.RequestStream;
+                if (arbitrator?.OnRequestMessage != null || arbitrator?.OnRequestStreamEnd != null)
+                {
+                    requestStream = new WrappedClientStreamWriter<TRequest>(response.RequestStream, arbitrator.OnRequestMessage, arbitrator.OnRequestStreamEnd);
+                }
+                var responseStream = response.ResponseStream;
+                if (arbitrator?.OnResponseMessage != null || arbitrator?.OnResponseStreamEnd != null)
+                {
+                    responseStream = new WrappedClientStreamReader<TResponse>(response.ResponseStream, arbitrator.OnResponseMessage, arbitrator.OnResponseStreamEnd);
+                }
+                response = new AsyncDuplexStreamingCall<TRequest, TResponse>(requestStream, responseStream, response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
+            }
+            return response;
+        }
+
+        /// <summary>
+        /// Server-side handler for intercepting unary calls.
+        /// </summary>
+        /// <typeparam name="TRequest">Request message type for this method.</typeparam>
+        /// <typeparam name="TResponse">Response message type for this method.</typeparam>
+        public override Task<TResponse> UnaryServerHandler<TRequest, TResponse>(TRequest request, ServerCallContext context, UnaryServerMethod<TRequest, TResponse> continuation)
+        {
+            return continuation(request, context);
+        }
+
+        /// <summary>
+        /// Server-side handler for intercepting client streaming call.
+        /// </summary>
+        /// <typeparam name="TRequest">Request message type for this method.</typeparam>
+        /// <typeparam name="TResponse">Response message type for this method.</typeparam>
+        public override Task<TResponse> ClientStreamingServerHandler<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream, ServerCallContext context, ClientStreamingServerMethod<TRequest, TResponse> continuation)
+        {
+            return continuation(requestStream, context);
+        }
+
+        /// <summary>
+        /// Server-side handler for intercepting server streaming calls.
+        /// </summary>
+        /// <typeparam name="TRequest">Request message type for this method.</typeparam>
+        /// <typeparam name="TResponse">Response message type for this method.</typeparam>
+        public override Task ServerStreamingServerHandler<TRequest, TResponse>(TRequest request, IServerStreamWriter<TResponse> responseStream, ServerCallContext context, ServerStreamingServerMethod<TRequest, TResponse> continuation)
+        {
+            return continuation(request, responseStream, context);
+        }
+
+        /// <summary>
+        /// Server-side handler for intercepting bidi streaming calls.
+        /// </summary>
+        /// <typeparam name="TRequest">Request message type for this method.</typeparam>
+        /// <typeparam name="TResponse">Response message type for this method.</typeparam>
+        public override Task DuplexStreamingServerHandler<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream, IServerStreamWriter<TResponse> responseStream, ServerCallContext context, DuplexStreamingServerMethod<TRequest, TResponse> continuation)
+        {
+            return continuation(requestStream, responseStream, context);
+        }
+
+        private class WrappedClientStreamReader<T> : IAsyncStreamReader<T>
+        {
+            readonly IAsyncStreamReader<T> reader;
+            readonly Func<T, T> onMessage;
+            readonly Action onStreamEnd;
+            public WrappedClientStreamReader(IAsyncStreamReader<T> reader, Func<T, T> onMessage, Action onStreamEnd)
+            {
+                this.reader = reader;
+                this.onMessage = onMessage;
+                this.onStreamEnd = onStreamEnd;
+            }
+
+            public void Dispose() => ((IDisposable)reader).Dispose();
+
+            private T current;
+            public T Current
+            {
+                get
+                {
+                    if (current == null)
+                    {
+                        throw new InvalidOperationException("No current element is available.");
+                    }
+                    return current;
+                }
+            }
+
+            public async Task<bool> MoveNext(CancellationToken token)
+            {
+                if (await reader.MoveNext(token))
+                {
+                    var current = reader.Current;
+                    if (onMessage != null)
+                    {
+                        var mappedValue = onMessage(current);
+                        if (mappedValue != null)
+                        {
+                            current = mappedValue;
+                        }
+                    }
+                    this.current = current;
+                    return true;
+                }
+                onStreamEnd?.Invoke();
+                return false;
+            }
+        }
+
+        private class WrappedClientStreamWriter<T> : IClientStreamWriter<T>
+        {
+            readonly IClientStreamWriter<T> writer;
+            readonly Func<T, T> onMessage;
+            readonly Action onResponseStreamEnd;
+            public WrappedClientStreamWriter(IClientStreamWriter<T> writer, Func<T, T> onMessage, Action onResponseStreamEnd)
+            {
+                this.writer = writer;
+                this.onMessage = onMessage;
+                this.onResponseStreamEnd = onResponseStreamEnd;
+            }
+            public Task CompleteAsync()
+            {
+                if (onResponseStreamEnd != null)
+                {
+                    return writer.CompleteAsync().ContinueWith(x => onResponseStreamEnd());
+                }
+                return writer.CompleteAsync();
+            }
+            public Task WriteAsync(T message)
+            {
+                if (onMessage != null)
+                {
+                    message = onMessage(message);
+                }
+                return writer.WriteAsync(message);
+            }
+            public WriteOptions WriteOptions
+            {
+                get
+                {
+                    return writer.WriteOptions;
+                }
+                set
+                {
+                    writer.WriteOptions = value;
+                }
+            }
+        }
+    }
+}