- Checkpoint: Refactor Event and Command Contract

Author: NinjaRocks

src/SourceFlow.ConsoleApp/Impl/InMemoryEventStore.cs

@@ -28,7 +28,7 @@ public Task<int> GetNextSequenceNo(int aggregateId)
         {
             if (_store.TryGetValue(aggregateId, out var events))
             {
-                return Task.FromResult(events.Max<ICommand, int>(c => c.SequenceNo) + 1);
+                return Task.FromResult(events.Max<ICommand, int>(c => ((IMetadata)c).Metadata.SequenceNo) + 1);
             }
             return Task.FromResult(1);
         }

src/SourceFlow.ConsoleApp/Sagas/AccountSaga.cs

@@ -2,7 +2,6 @@
 using SourceFlow.ConsoleApp.Aggregates;
 using SourceFlow.ConsoleApp.Commands;
 using SourceFlow.ConsoleApp.Events;
-using SourceFlow.Messaging;
 using SourceFlow.Saga;
 
 namespace SourceFlow.ConsoleApp.Sagas

src/SourceFlow.ConsoleApp/Services/IAccountService.cs

@@ -1,5 +1,3 @@
-using SourceFlow.ConsoleApp.Aggregates;
-
 namespace SourceFlow.ConsoleApp.Services
 {
     public interface IAccountService

src/SourceFlow/Aggregate/IAggregateFactory.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Threading.Tasks;
 
 namespace SourceFlow.Aggregate

src/SourceFlow/Aggregate/IEntity.cs

@@ -1,5 +1,3 @@
-using System;
-
 namespace SourceFlow.Aggregate
 {
     public interface IEntity

src/SourceFlow/IEventStore.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using SourceFlow.Messaging;

src/SourceFlow/Impl/CommandBus.cs

@@ -90,18 +90,18 @@ private async Task PublishToSagas<TCommand>(TCommand command) where TCommand : I
         private async Task SagaHandle<TCommand>(ISaga saga, TCommand command) where TCommand : ICommand
         {
             // 1. Set event sequence no.
-            if (!command.IsReplay)
-                command.SequenceNo = await eventStore.GetNextSequenceNo(command.Payload.Id);
+            if (!((IMetadata)command).Metadata.IsReplay)
+                ((IMetadata)command).Metadata.SequenceNo = await eventStore.GetNextSequenceNo(command.Payload.Id);
 
             // 4. Log event.
             logger?.LogInformation("Action=Command_Dispatched, Command={Command}, Payload={Payload}, SequenceNo={No}, Saga={Saga}",
-                command.GetType().Name, command.Payload.GetType().Name, command.SequenceNo, saga.GetType().Name);
+                command.GetType().Name, command.Payload.GetType().Name, ((IMetadata)command).Metadata.SequenceNo, saga.GetType().Name);
 
             // 2. handle event by Saga?
             await saga.Handle(command);
 
             // 3. When event is not replayed
-            if (!command.IsReplay)
+            if (!((IMetadata)command).Metadata.IsReplay)
                 // 3.1. Append event to event store.
                 await eventStore.Append(command);
         }
@@ -120,7 +120,7 @@ async Task ICommandBus.Replay(int aggregateId)
 
             foreach (var command in commands.ToList())
             {
-                command.IsReplay = true;
+                ((IMetadata)command).Metadata.IsReplay = true;
                 await PublishToSagas(command);
             }
         }

src/SourceFlow/Impl/CommandReplayer.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Threading.Tasks;
 using SourceFlow.Messaging.Bus;
 

src/SourceFlow/Messaging/BaseCommand.cs

@@ -1,11 +1,9 @@
-using System;
-
 namespace SourceFlow.Messaging
 {
     /// <summary>
     /// Base class for command in the command-driven architecture.
     /// </summary>
-    public class BaseCommand<TPayload> : ICommand<TPayload>
+    public class BaseCommand<TPayload> : ICommand
         where TPayload : class, IPayload, new()
     {
         /// <summary>
@@ -14,30 +12,20 @@ public class BaseCommand<TPayload> : ICommand<TPayload>
         /// <param name="payload"></param>
         public BaseCommand(TPayload payload)
         {
-            EventId = Guid.NewGuid();
-            OccurredOn = DateTime.UtcNow;
+            Metadata = new Metadata();
+            Name = GetType().Name;
             Payload = payload;
         }
 
         /// <summary>
-        /// Unique identifier for the command.
-        /// </summary>
-        public Guid EventId { get; }
-
-        /// <summary>
-        /// Indicates whether the command is a replay of an existing command.
-        /// </summary>
-        public DateTime OccurredOn { get; }
-
-        /// <summary>
-        /// Indicates whether the command is a replay of an existing command.
+        /// Metadata associated with the command, which includes information such as event ID, occurrence time, and sequence number.
         /// </summary>
-        bool ICommand.IsReplay { get; set; }
+        public Metadata Metadata { get; set; } = new Metadata();
 
         /// <summary>
-        /// Sequence number of the command within the aggregate's command stream.
+        /// Name of the command, typically the class name.
         /// </summary>
-        public int SequenceNo { get; set; }
+        public string Name { get; set; }
 
         /// <summary>
         /// Payload of the command, containing the data associated with the command.

src/SourceFlow/Messaging/BaseEvent.cs

@@ -9,6 +9,22 @@ namespace SourceFlow.Messaging
     public abstract class BaseEvent<TEntity> : IEvent
         where TEntity : IEntity
     {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="BaseEvent{TEntity}"/> class with a specified payload.
+        /// </summary>
+        /// <param name="payload"></param>
+        public BaseEvent(TEntity payload)
+        {
+            Metadata = new Metadata();
+            Name = GetType().Name;
+            Payload = payload;
+        }
+
+        /// <summary>
+        /// Metadata associated with the event, which includes information such as event ID, occurrence time, and sequence number.
+        /// </summary>
+        public Metadata Metadata { get; set; }
+
         /// <summary>
         /// Name of the event, typically the class name.
         /// </summary>
@@ -30,15 +46,5 @@ IEntity IEvent.Payload
                 Payload = (TEntity)value;
             }
         }
-
-        /// <summary>
-        /// Creates a new instance of the <see cref="BaseEvent{TEntity}"/> class with the specified payload.
-        /// </summary>
-        /// <param name="payload"></param>
-        public BaseEvent(TEntity payload)
-        {
-            Name = GetType().Name;
-            Payload = payload;
-        }
     }
 }