Added RemotingServer events to allow method interception

CoreRemoting.Tests/RpcTests.cs

@@ -768,9 +768,72 @@ void AfterCall(object sender, ServerRpcContext e) =>
         }
 
         [Fact]
-        public void Authentication_is_taken_into_account()
+        public void BeginCall_event_handler_can_intercept_and_cancel_method_calls()
         {
+            var counter = 0;
+
+            void InterceptMethodCalls(object sender, ServerRpcContext e)
+            {
+                Interlocked.Increment(ref counter);
+
+                // swap Echo and Reverse methods
+                e.MethodCallMessage.MethodName = e.MethodCallMessage.MethodName switch
+                {
+                    "Echo" => "Reverse",
+                    "Reverse" => "Echo",
+                    var others => others
+                };
+
+                // disable IHobbitService
+                if (e.MethodCallMessage.ServiceName.Contains("IHobbitService"))
+                {
+                    e.Cancel = true;
+                }
+            }
+
+            _serverFixture.Server.BeginCall += InterceptMethodCalls;
+            try
+            {
+                using var client = new RemotingClient(new ClientConfig()
+                {
+                    ConnectionTimeout = 0,
+                    InvocationTimeout = 0,
+                    SendTimeout = 0,
+                    Channel = ClientChannel,
+                    MessageEncryption = false,
+                    ServerPort = _serverFixture.Server.Config.NetworkPort,
+                });
+
+                client.Connect();
+
+                // try swapped methods
+                var proxy = client.CreateProxy<ITestService>();
+                Assert.Equal("321", proxy.Echo("123"));
+                Assert.Equal("Hello", proxy.Reverse("Hello"));
+
+                // try disabled service
+                var hobbit = client.CreateProxy<IHobbitService>();
+                Assert.Throws<RemoteInvocationException>(() =>
+                    hobbit.QueryHobbits(h => h.LastName != ""));
+
+                // check interception counter
+                Assert.Equal(3, counter);
+            }
+            finally
+            {
+                _serverFixture.Server.BeginCall -= InterceptMethodCalls;
+            }
+        }
+
+        [Fact]
+        public void Authentication_is_taken_into_account_and_RejectCall_event_is_fired()
+        {
+            var rejectedMethod = string.Empty;
+            void RejectCall(object sender, ServerRpcContext e) =>
+                rejectedMethod = e.MethodCallMessage.MethodName;
+
             _serverFixture.Server.Config.AuthenticationRequired = true;
+            _serverFixture.Server.RejectCall += RejectCall;
             try
             {
                 using var client = new RemotingClient(new ClientConfig()
@@ -790,10 +853,14 @@ public void Authentication_is_taken_into_account()
 
                 // Session is not authenticated
                 Assert.Contains("authenticated", ex.Message);
+
+                // Method call was rejected
+                Assert.Equal("Hello", rejectedMethod);
             }
             finally
             {
                 _serverFixture.Server.Config.AuthenticationRequired = false;
+                _serverFixture.Server.RejectCall -= RejectCall;
             }
         }
     }

CoreRemoting.Tests/Tools/ITestService.cs

@@ -29,6 +29,8 @@ public interface ITestService : IBaseService
 
         string Echo(string text);
 
+        string Reverse(string text);
+
         void MethodWithOutParameter(out int counter);
 
         void Error(string text);

CoreRemoting.Tests/Tools/TestService.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Data;
+using System.Linq;
 using System.Threading.Tasks;
 using CoreRemoting.Tests.ExternalTypes;
 
@@ -54,6 +55,11 @@ public string Echo(string text)
             return text;
         }
 
+        public string Reverse(string text)
+        {
+            return new string(text.Reverse().ToArray());
+        }
+
         public void MethodWithOutParameter(out int counter)
         {
             _counter++;

CoreRemoting/IRemotingServer.cs

@@ -12,60 +12,70 @@ namespace CoreRemoting
     public interface IRemotingServer : IDisposable
     {
         /// <summary>
-        /// Event: Fires before an RPC call is invoked.
+        /// Event: Fires when an RPC call is prepared and can be canceled.
+        /// </summary>
+        event EventHandler<ServerRpcContext> BeginCall;
+
+        /// <summary>
+        /// Event: Fires just before an RPC call is invoked.
         /// </summary>
         event EventHandler<ServerRpcContext> BeforeCall;
-        
+
         /// <summary>
-        /// Event: Fires after an RPC call is invoked.
+        /// Event: Fires after an RPC call is invoked, both on success or failure.
         /// </summary>
         event EventHandler<ServerRpcContext> AfterCall;
 
         /// <summary>
         /// Event: Fires if an error occurs.
         /// </summary>
         event EventHandler<Exception> Error;
-
+
+        /// <summary>
+        /// Event: Fires when an RPC call is rejected before BeginCall event. .
+        /// </summary>
+        event EventHandler<ServerRpcContext> RejectCall;
+
         /// <summary>
         /// Gets the unique name of this server instance.
         /// </summary>
         string UniqueServerInstanceName { get; }
-        
+
         /// <summary>
         /// Gets the dependency injection container that is used a service registry.
         /// </summary>
         IDependencyInjectionContainer ServiceRegistry { get; }
-        
+
         /// <summary>
         /// Gets the configured serializer.
         /// </summary>
         ISerializerAdapter Serializer { get; }
-        
+
         /// <summary>
         /// Gets the component for easy building of method call messages.
         /// </summary>
         MethodCallMessageBuilder MethodCallMessageBuilder { get; }
-        
+
         /// <summary>
         /// Gets the component for encryption and decryption of messages.
         /// </summary>
         IMessageEncryptionManager MessageEncryptionManager { get; }
-        
+
         /// <summary>
         /// Gets the session repository to perform session management tasks.
         /// </summary>
         ISessionRepository SessionRepository { get; }
-        
+
         /// <summary>
         /// Gets the configuration settings.
         /// </summary>
         ServerConfig Config { get; }
-        
+
         /// <summary>
         /// Starts listening for client requests.
         /// </summary>
         void Start();
-        
+
         /// <summary>
         /// Stops listening for client requests and close all open client connections.
         /// </summary>

CoreRemoting/RemotingServer.cs

@@ -11,6 +11,7 @@
 using CoreRemoting.Serialization;
 using CoreRemoting.Serialization.Bson;
 using ServiceLifetime = CoreRemoting.DependencyInjection.ServiceLifetime;
+using System.Runtime.ExceptionServices;
 
 namespace CoreRemoting
 {
@@ -91,7 +92,17 @@ public RemotingServer(ServerConfig config = null)
         /// Event: Fires if an error occurs.
         /// </summary>
         public event EventHandler<Exception> Error;
-
+
+        /// <summary>
+        /// Event: Fires when an RPC call is rejected before BeforeCall event.
+        /// </summary>
+        public event EventHandler<ServerRpcContext> RejectCall;
+
+        /// <summary>
+        /// Event: Fires when an RPC call is prepared and can be canceled.
+        /// </summary>
+        public event EventHandler<ServerRpcContext> BeginCall;
+
         /// <summary>
         /// Gets the dependency injection container that is used a service registry.
         /// </summary>
@@ -134,7 +145,7 @@ public RemotingServer(ServerConfig config = null)
         public IServerChannel Channel { get; private set; }
 
         /// <summary>
-        /// Fires the OnBeforeCall event.
+        /// Fires the <see cref="BeforeCall"/> event.
         /// </summary>
         /// <param name="serverRpcContext">Server side RPC call context</param>
         internal void OnBeforeCall(ServerRpcContext serverRpcContext)
@@ -143,7 +154,7 @@ internal void OnBeforeCall(ServerRpcContext serverRpcContext)
         }
 
         /// <summary>
-        /// Fires the OnAfterCall event.
+        /// Fires the <see cref="AfterCall"/> event.
         /// </summary>
         /// <param name="serverRpcContext">Server side RPC call context</param>
         internal void OnAfterCall(ServerRpcContext serverRpcContext)
@@ -152,14 +163,43 @@ internal void OnAfterCall(ServerRpcContext serverRpcContext)
         }
 
         /// <summary>
-        /// Fires the OnError event.
+        /// Fires the <see cref="Error"/> event.
         /// </summary>
         /// <param name="ex">Exception that describes the occurred error</param>
         internal void OnError(Exception ex)
         {
             Error?.Invoke(this, ex);
         }
-
+
+        /// <summary>
+        /// Fires the <see cref="RejectCall"/> event.
+        /// </summary>
+        /// <param name="serverRpcContext">Server side RPC call context</param>
+        internal void OnRejectCall(ServerRpcContext serverRpcContext)
+        {
+            RejectCall?.Invoke(this, serverRpcContext);
+        }
+
+        /// <summary>
+        /// Fires the <see cref="BeginCall"/> event.
+        /// </summary>
+        /// <param name="serverRpcContext">Server side RPC call context</param>
+        internal void OnBeginCall(ServerRpcContext serverRpcContext)
+        {
+            BeginCall?.Invoke(this, serverRpcContext);
+
+            if (serverRpcContext.Cancel)
+            {
+                var cancelEx = serverRpcContext.Exception ??
+                    new RemoteInvocationException($"Invocation canceled: {
+                        serverRpcContext.MethodCallMessage.ServiceName}.{
+                        serverRpcContext.MethodCallMessage.MethodName}");
+
+                // rethrow the exception keeping the original stack trace
+                ExceptionDispatchInfo.Capture(cancelEx).Throw();
+            }
+        }
+
         /// <summary>
         /// Starts listening for client requests.
         /// </summary>