updated initial State creation

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 All notable changes to this project will be documented in this file.
 
+## [2021-01-14](https://github.com/mizrael/OpenSleigh/pull/16)
+### Added
+- Saga States can now be reconstructed from typed messages
+
 ## [2021-01-14](https://github.com/mizrael/OpenSleigh/pull/15)
 ### Added
 - possibility to configure exchange and queue names for each message

readme.md

@@ -81,8 +81,7 @@ Dependency injection can be used to reference services from Sagas.
 At this point all you have to do is register and configure the Saga:
 ```
 services.AddOpenSleigh(cfg =>{
-    cfg.AddSaga<MyAwesomeSaga, MyAwesomeSagaState>()
-        .UseStateFactory(msg => new MyAwesomeSagaState(msg.CorrelationId))
+    cfg.AddSaga<MyAwesomeSaga, MyAwesomeSagaState>()      
         .UseRabbitMQTransport(rabbitConfig);
 });
 ```
@@ -115,6 +114,17 @@ Each message has to expose an `Id` property and a `CorrelationId`. Those are use
 If a Saga is sending a message to itself (loopback), or spawning child Sagas, the `CorrelationId` has to be kept unchanged on all the messages. 
 Also, make sure the `Id` and the `CorrelationId` don't match!
 
+We also have to specify the starting message for a Saga when registering it on our DI container, by calling the `UseStateFactory()` method:
+
+```
+services.AddOpenSleigh(cfg =>{
+    cfg.AddSaga<MyAwesomeSaga, MyAwesomeSagaState>()
+        .UseStateFactory<StartMyAwesomeSaga>(msg => new MyAwesomeSagaState(msg.CorrelationId))
+        .UseRabbitMQTransport(rabbitConfig);
+});
+```
+This call will tell OpenSleigh how it can build the initial State for the current Saga when loading it for the first time.
+
 #### Handling messages
 
 In order to handle more message types, it is necessary to add and implement the [`IHandleMessage<>`](https://github.com/mizrael/OpenSleigh/blob/develop/src/OpenSleigh.Core/IHandleMessage.cs) interface:

samples/Sample1/OpenSleigh.Samples.Sample1.Console/Program.cs

@@ -42,7 +42,7 @@ static async Task Main(string[] args)
                             .UseInMemoryPersistence();
 
                         cfg.AddSaga<MySaga, MySagaState>()
-                            .UseStateFactory(msg => new MySagaState(msg.CorrelationId))
+                            .UseStateFactory<StartSaga>(msg => new MySagaState(msg.CorrelationId))
                             .UseInMemoryTransport();
                     });
             });

samples/Sample2/OpenSleigh.Samples.Sample2.Worker/Program.cs

@@ -54,15 +54,15 @@ static async Task Main(string[] args)
                             .UseMongoPersistence(mongoCfg);
 
                         cfg.AddSaga<SimpleSaga, SimpleSagaState>()
-                            .UseStateFactory(msg => new SimpleSagaState(msg.CorrelationId))
+                            .UseStateFactory<StartSimpleSaga>(msg => new SimpleSagaState(msg.CorrelationId))
                             .UseRabbitMQTransport();
 
                         cfg.AddSaga<ParentSaga, ParentSagaState>()
-                            .UseStateFactory(msg => new ParentSagaState(msg.CorrelationId))
+                            .UseStateFactory<StartParentSaga>(msg => new ParentSagaState(msg.CorrelationId))
                             .UseRabbitMQTransport();
 
                         cfg.AddSaga<ChildSaga, ChildSagaState>()
-                            .UseStateFactory(msg => new ChildSagaState(msg.CorrelationId))
+                            .UseStateFactory<StartChildSaga>(msg => new ChildSagaState(msg.CorrelationId))
                             .UseRabbitMQTransport();
                     });
             });

src/OpenSleigh.Core/DependencyInjection/BusConfigurator.cs

@@ -20,14 +20,15 @@ public BusConfigurator(IServiceCollection services, ISagaTypeResolver typeResolv
             _typeResolver = typeResolver ?? throw new ArgumentNullException(nameof(typeResolver));
         }
 
-        public ISagaConfigurator<TS, TD> AddSaga<TS, TD>() 
-            where TS : Saga<TD> where TD : SagaState
+        public ISagaConfigurator<TS, TD> AddSaga<TS, TD>()
+            where TD : SagaState
+            where TS : Saga<TD>
         {
+            bool hasMessages = false;
+
             var sagaType = typeof(TS);
             var sagaStateType = typeof(TD);
-
-            Services.AddScoped<TS>();
-
+
             var messageHandlerType = typeof(IHandleMessage<>).GetGenericTypeDefinition();
 
             var interfaces = sagaType.GetInterfaces();
@@ -54,16 +55,18 @@ public BusConfigurator(IServiceCollection services, ISagaTypeResolver typeResolv
                 _typeResolver.Register(messageType, (sagaType, sagaStateType));
 
                 Services.AddTransient(i, sagaType);
-            }
-
-            Services.AddSingleton(typeof(ISagaStateService<,>).MakeGenericType(sagaType, sagaStateType),
-                                 typeof(SagaStateService<,>).MakeGenericType(sagaType, sagaStateType));
 
-            Services.AddSingleton(typeof(ISagaRunner<,>).MakeGenericType(sagaType, sagaStateType),
-                                  typeof(SagaRunner<,>).MakeGenericType(sagaType, sagaStateType));
+                hasMessages = true;
+            }
 
-            Services.AddSingleton(typeof(ISagaFactory<,>).MakeGenericType(sagaType, sagaStateType),
-                                typeof(DefaultSagaFactory<,>).MakeGenericType(sagaType, sagaStateType));
+            if (hasMessages)
+            {
+                Services.AddScoped<TS>();
+                Services.AddSingleton<ISagaStateService<TS, TD>, SagaStateService<TS, TD>>();
+                Services.AddSingleton<ISagaRunner<TS, TD>, SagaRunner<TS, TD>>();
+                Services.AddSingleton<ISagaFactory<TS, TD>, DefaultSagaFactory<TS, TD>>();
+                Services.AddSingleton<ISagaStateFactory<TD>, DefaultSagaStateFactory<TD>>();
+            }
 
             return new SagaConfigurator<TS, TD>(Services);
         }

src/OpenSleigh.Core/DependencyInjection/ISagaConfigurator.cs

@@ -11,7 +11,8 @@ public interface ISagaConfigurator<TS, in TD>
         where TD : SagaState
     {
         IServiceCollection Services { get; }
-        ISagaConfigurator<TS, TD> UseStateFactory(Func<IMessage, TD> stateFactory);
+        ISagaConfigurator<TS, TD> UseStateFactory<TM>(Func<TM, TD> stateFactory)
+            where TM : IMessage;
     }
 
     [ExcludeFromCodeCoverage]
@@ -26,12 +27,16 @@ public SagaConfigurator(IServiceCollection services)
 
         public IServiceCollection Services { get; }
 
-        public ISagaConfigurator<TS, TD> UseStateFactory(Func<IMessage, TD> stateFactory)
+        public ISagaConfigurator<TS, TD> UseStateFactory<TM>(Func<TM, TD> stateFactory)
+            where TM : IMessage
         {
+            var messageType = typeof(TM);
             var stateType = typeof(TD);
-            var factory = new LambdaSagaStateFactory<TD>(stateFactory);
 
-            var descriptor = ServiceDescriptor.Singleton(typeof(ISagaStateFactory<>).MakeGenericType(stateType), factory);
+            var factoryInterfaceType = typeof(ISagaStateFactory<,>).MakeGenericType(messageType, stateType);
+            var factory = new LambdaSagaStateFactory<TM, TD>(stateFactory);
+
+            var descriptor = ServiceDescriptor.Singleton(factoryInterfaceType, factory);
             this.Services.Replace(descriptor);
 
             return this;

src/OpenSleigh.Core/Exceptions/StateCreationException.cs

@@ -8,6 +8,8 @@ namespace OpenSleigh.Core.Exceptions
     [ExcludeFromCodeCoverage]
     public class StateCreationException : Exception
     {
+        public StateCreationException(string message) : base(message) { }
+
         public StateCreationException(Type stateType, Guid correlationId) 
             : base($"unable to create State instance with type '{stateType.FullName}' for Saga '{correlationId}'")
         {

src/OpenSleigh.Core/ISagaStateFactory.cs

@@ -0,0 +1,47 @@
+using System;
+using OpenSleigh.Core.Exceptions;
+using OpenSleigh.Core.Messaging;
+
+namespace OpenSleigh.Core
+{
+    public interface ISagaStateFactory<in TM, out TD> : ISagaStateFactory<TD>
+        where TM : IMessage
+        where TD : SagaState
+    {
+        TD Create(TM message);
+    }
+
+    public interface ISagaStateFactory<out TD> where TD : SagaState
+    {
+        TD Create(IMessage message);
+    }
+
+    internal class DefaultSagaStateFactory<TD> : ISagaStateFactory<TD> 
+        where TD : SagaState
+    {
+        private readonly IServiceProvider _serviceProvider;
+
+        public DefaultSagaStateFactory(IServiceProvider serviceProvider)
+        {
+            _serviceProvider = serviceProvider ?? throw new ArgumentNullException(nameof(serviceProvider));
+        }
+
+        public TD Create(IMessage message)
+        {
+            if (message == null) 
+                throw new ArgumentNullException(nameof(message));
+
+            var messageType = message.GetType();
+            var stateType = typeof(TD);
+
+            var factoryInterfaceType = typeof(ISagaStateFactory<,>).MakeGenericType(messageType, stateType);
+            var factory = _serviceProvider.GetService(factoryInterfaceType) as ISagaStateFactory<TD>;
+            if (null == factory)
+                throw new StateCreationException(
+                    $"no state factory registered for message type '{message.GetType().FullName}'");
+
+            var state = factory.Create((dynamic) message);
+            return state;
+        }
+    }
+}

src/OpenSleigh.Core/LambdaSagaStateFactory.cs

@@ -0,0 +1,26 @@
+using System;
+using OpenSleigh.Core.Messaging;
+
+namespace OpenSleigh.Core
+{
+    internal class LambdaSagaStateFactory<TM, TD> : ISagaStateFactory<TM, TD>
+        where TM : IMessage
+        where TD : SagaState
+    {
+        private readonly Func<TM, TD> _factory;
+
+        public LambdaSagaStateFactory(Func<TM, TD> factory)
+        {
+            _factory = factory ?? throw new ArgumentNullException(nameof(factory));
+        }
+
+        public TD Create(TM message) => _factory(message);
+
+        public TD Create(IMessage message)
+        {
+            if (message is TM m)
+                return _factory(m);
+            return null;
+        } 
+    }
+}

src/OpenSleigh.Core/SagaStateService.cs

@@ -1,4 +1,3 @@
-using OpenSleigh.Core.DependencyInjection;
 using OpenSleigh.Core.Exceptions;
 using OpenSleigh.Core.Persistence;
 using System;
@@ -25,18 +24,21 @@ public SagaStateService(ISagaStateFactory<TD> sagaStateFactory, ISagaStateReposi
             CancellationToken cancellationToken = default) where TM : IMessage
         {
             var correlationId = messageContext.Message.CorrelationId;
-
-            var defaultState = _sagaStateFactory.Create(messageContext.Message);
-
-            var result = await _sagaStateRepository.LockAsync(correlationId, defaultState, cancellationToken);
+
+            var isStartMessage = (typeof(IStartedBy<TM>).IsAssignableFrom(typeof(TS)));
+            TD initialState = null;
+            if (isStartMessage)
+                initialState = _sagaStateFactory.Create(messageContext.Message);
+
+            var result = await _sagaStateRepository.LockAsync(correlationId, initialState, cancellationToken);
 
             if (null != result.state)
                 return result;
 
             // if state is null, we're probably starting a new saga.
             // We have to check if the current message can
             // actually start the specified saga or not
-            if (!typeof(IStartedBy<TM>).IsAssignableFrom(typeof(TS)))
+            if (!isStartMessage)
                 throw new MessageException($"Saga '{correlationId}' cannot be started by message '{typeof(TM).FullName}'");
 
             throw new StateCreationException(typeof(TD), correlationId);

src/OpenSleigh.Persistence.InMemory/InMemorySagaConfiguratorExtensions.cs

@@ -1,7 +1,6 @@
 using OpenSleigh.Core;
 using OpenSleigh.Core.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection;
-using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;

src/OpenSleigh.Persistence.InMemory/InMemorySagaStateRepository.cs

@@ -3,7 +3,6 @@
 using OpenSleigh.Core.Persistence;
 using System;
 using System.Collections.Concurrent;
-using System.Diagnostics.Contracts;
 using System.Threading;
 using System.Threading.Tasks;
 

src/OpenSleigh.Persistence.InMemory/Messaging/InMemorySubscriber.cs

@@ -2,28 +2,40 @@
 using System.Threading;
 using System.Threading.Channels;
 using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
 using OpenSleigh.Core;
 using OpenSleigh.Core.Messaging;
 
 namespace OpenSleigh.Persistence.InMemory.Messaging
 {
-    internal class InMemorySubscriber<TM> : ISubscriber
+    public class InMemorySubscriber<TM> : ISubscriber
         where TM : IMessage
     {
         private readonly IMessageProcessor _messageProcessor;
         private readonly ChannelReader<TM> _reader;
-
-        public InMemorySubscriber(IMessageProcessor messageProcessor, ChannelReader<TM> reader)
+        private readonly ILogger<InMemorySubscriber<TM>> _logger;
+
+        public InMemorySubscriber(IMessageProcessor messageProcessor, 
+            ChannelReader<TM> reader, 
+            ILogger<InMemorySubscriber<TM>> logger)
         {
             _messageProcessor = messageProcessor ?? throw new ArgumentNullException(nameof(messageProcessor));
             _reader = reader ?? throw new ArgumentNullException(nameof(reader));
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
         }
 
         public async Task StartAsync(CancellationToken cancellationToken = default)
         {
             await foreach (var message in _reader.ReadAllAsync(cancellationToken))
             {
-                await _messageProcessor.ProcessAsync(message, cancellationToken);
+                try
+                {
+                    await _messageProcessor.ProcessAsync(message, cancellationToken);
+                }
+                catch (Exception e)
+                {
+                    _logger.LogError(e, $"an exception has occurred while processing message '{message.Id}': {e.Message}");
+                }
             }
         }
 

src/OpenSleigh.Transport.RabbitMQ/QueueReferenceFactory.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Concurrent;
 using Microsoft.Extensions.DependencyInjection;
-using OpenSleigh.Core;
 using OpenSleigh.Core.Messaging;
 
 namespace OpenSleigh.Transport.RabbitMQ