Add generic json mapper

src/Paramore.Brighter/GenericJsonMessageMapper.cs

@@ -0,0 +1,60 @@
+using System;
+using System.IO;
+using System.Text;
+using Newtonsoft.Json;
+
+namespace Paramore.Brighter
+{
+    public class GenericJsonMessageMapper<T> : IAmAMessageMapper<T> where T : class, IRequest
+    {
+        private readonly IRequestContext _requestContext;
+        private readonly Func<T, string> _routingAction;
+        private readonly RoutingKey _routingKey;
+        private readonly JsonSerializer _serializer = new JsonSerializer();
+
+        public GenericJsonMessageMapper(IRequestContext requestContext, RoutingKey routingKey = null,  Func<T, string> routingKeyFunc = null)
+        {
+            _requestContext = requestContext;
+            _routingKey = routingKey;
+            _routingAction = routingKeyFunc;
+        }
+
+        public Message MapToMessage(T request)
+        {
+            MessageType messageType;
+            if (request is Command)
+                messageType = MessageType.MT_COMMAND;
+            else if (request is Event)
+                messageType = MessageType.MT_EVENT;
+            else
+            {
+                throw new ArgumentException("This message mapper can only map Commands and Events", nameof(request));
+            }
+
+            var topic = _routingAction?.Invoke(request) ?? _routingKey ?? request.GetType().Name;
+
+            using (var memoryStream = new MemoryStream())
+            {
+                using (var streamWriter = new StreamWriter(memoryStream, new UTF8Encoding(false)))
+                using (var jsonTextWriter = new JsonTextWriter(streamWriter))
+                {
+                    _serializer.Serialize(jsonTextWriter, request, typeof(T));
+                }
+
+                return new Message(new MessageHeader(request.Id, topic, messageType, _requestContext.Header.CorrelationId, contentType: "application/json"), new MessageBody(memoryStream.ToArray(), "JSON"));
+            }
+        }
+
+        public T MapToRequest(Message message)
+        {
+            _requestContext.Header.CorrelationId = message.Header.CorrelationId;
+
+            using (var memoryStream = new MemoryStream(message.Body.Bytes))
+            using (var streamReader = new StreamReader(memoryStream, Encoding.UTF8))
+            using (JsonReader reader = new JsonTextReader(streamReader))
+            {
+                return _serializer.Deserialize<T>(reader);
+            }
+        }
+    }
+}

src/Paramore.Brighter/IRequestContext.cs

@@ -51,5 +51,7 @@ public interface IRequestContext
         /// Gets the Feature Switches
         /// </summary>
         IAmAFeatureSwitchRegistry FeatureSwitches { get; }
+
+        Header Header { get; }
     }
 }

src/Paramore.Brighter/RequestContext.cs

@@ -22,6 +22,7 @@ THE SOFTWARE. */
 
 #endregion
 
+using System;
 using System.Collections.Generic;
 using Paramore.Brighter.FeatureSwitch;
 using Polly.Registry;
@@ -58,5 +59,12 @@ public RequestContext()
         /// Gets the Feature Switches
         /// </summary>
         public IAmAFeatureSwitchRegistry FeatureSwitches { get; set; }
+
+        public Header Header { get; } = new Header();
+    }
+
+    public class Header
+    {
+        public Guid CorrelationId { get; set; }
     }
 }

tests/Paramore.Brighter.Core.Tests/MessageMapper/JsonMessageMapperTests.cs

@@ -0,0 +1,140 @@
+using System;
+using System.Text;
+using Xunit;
+
+namespace Paramore.Brighter.Tests.MessageMapper
+{
+    public class JsonMessageMapperTests
+    {
+        [Fact]
+        public void When_mapping_an_event_to_a_message_as_json()
+        {
+            var requestContext = new RequestContext();
+
+            var mapper = new GenericJsonMessageMapper<TestedEvent>(requestContext);
+
+            DateTime dateTime = DateTime.UtcNow;
+            TestedEvent testedEvent = new TestedEvent
+            {
+                Message = "This is a message",
+                Number = 999,
+                DateNow = dateTime
+            };
+
+            requestContext.Header.CorrelationId = Guid.NewGuid();
+
+            var message = mapper.MapToMessage(testedEvent);
+
+            // Message checks
+            Assert.Equal(testedEvent.Id, message.Id);
+
+           // Header checks
+            Assert.Equal("application/json", message.Header.ContentType);
+            Assert.Equal("TestedEvent", message.Header.Topic);
+            Assert.Equal(MessageType.MT_EVENT , message.Header.MessageType);
+            Assert.Equal( requestContext.Header.CorrelationId , message.Header.CorrelationId);
+
+            // Body checks
+            Assert.Equal("JSON", message.Body.BodyType);
+            Assert.Equal($"{{\"Message\":\"{testedEvent.Message}\",\"Number\":{testedEvent.Number},\"DateNow\":\"{dateTime:O}\",\"Id\":\"{testedEvent.Id}\"}}", message.Body.Value);
+        }
+
+
+        [Fact]
+        public void When_mapping_a_command_to_a_message_as_json()
+        {
+            var requestContext = new RequestContext();
+
+            var mapper = new GenericJsonMessageMapper<TestCommand>(requestContext);
+
+            DateTime dateTime = DateTime.UtcNow;
+            TestCommand testCommand = new TestCommand
+            {
+                Message = "This is a message",
+                Number = 999,
+                DateNow = dateTime
+            };
+
+            requestContext.Header.CorrelationId = Guid.NewGuid();
+
+            var message = mapper.MapToMessage(testCommand);
+
+            // Message checks
+            Assert.Equal(testCommand.Id, message.Id);
+
+            // Header checks
+            Assert.Equal("application/json", message.Header.ContentType);
+            Assert.Equal("TestCommand", message.Header.Topic);
+            Assert.Equal(MessageType.MT_COMMAND , message.Header.MessageType);
+            Assert.Equal( requestContext.Header.CorrelationId , message.Header.CorrelationId);
+
+            // Body checks
+            Assert.Equal("JSON", message.Body.BodyType);
+            Assert.Equal($"{{\"Message\":\"{testCommand.Message}\",\"Number\":{testCommand.Number},\"DateNow\":\"{dateTime:O}\",\"Id\":\"{testCommand.Id}\"}}", message.Body.Value);
+        }
+
+        [Fact]
+        public void When_mapping_with_custom_routing_key_to_a_message()
+        {
+            var mapper = new GenericJsonMessageMapper<TestCommand>(new RequestContext(), new RoutingKey("MyTestRoute"));
+
+            var testCommand = new TestCommand();
+
+            var message = mapper.MapToMessage(testCommand);
+
+            Assert.Equal("MyTestRoute", message.Header.Topic);
+        }
+
+        [Fact]
+        public void When_mapping_with_custom_routing_key_to_a_message2()
+        {
+            var mapper = new GenericJsonMessageMapper<TestCommand>(new RequestContext(), routingKeyFunc: request =>
+            {
+                string topic = "TestPreAmble.";
+
+                string name = request.GetType().Name;
+
+                if (name.EndsWith("Command", StringComparison.InvariantCultureIgnoreCase))
+                    topic = topic + name.Replace("Command", "", StringComparison.InvariantCultureIgnoreCase);
+                else if (name.EndsWith("Event", StringComparison.InvariantCultureIgnoreCase))
+                    topic = topic + name.Replace("Event", "", StringComparison.InvariantCultureIgnoreCase);
+                else
+                {
+                    topic = topic + name;
+                }
+
+                return topic;
+            } );
+
+            var testCommand = new TestCommand();
+
+            var message = mapper.MapToMessage(testCommand);
+
+            Assert.Equal("TestPreAmble.Test", message.Header.Topic);
+        }
+
+
+    }
+
+    public class TestCommand : Command
+    {
+        public TestCommand() : base(Guid.NewGuid())
+        {
+        }
+
+        public string Message { get; set; }
+        public int Number { get; set; }
+        public DateTime DateNow { get; set; }
+    }
+
+    public class TestedEvent : Event
+    {
+        public TestedEvent() : base(Guid.NewGuid())
+        {
+        }
+
+        public string Message { get; set; }
+        public int Number { get; set; }
+        public DateTime DateNow { get; set; }
+    }
+}