feat: add IIdempotentCommandHandler

src/Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency/Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency.csproj

@@ -5,5 +5,9 @@
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\Be.Vlaanderen.Basisregisters.CommandHandling\Be.Vlaanderen.Basisregisters.CommandHandling.csproj" />
+  </ItemGroup>
+
   <Import Project="..\..\.paket\Paket.Restore.targets" />
 </Project>

src/Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency/IIdempotentCommandHandler.cs

@@ -0,0 +1,16 @@
+namespace Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+    using System.Threading.Tasks;
+
+    public interface IIdempotentCommandHandler
+    {
+        Task<long> Dispatch(
+            Guid? commandId,
+            object command,
+            IDictionary<string, object> metadata,
+            CancellationToken cancellationToken);
+    }
+}

src/Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency/IdempotencyException.cs

@@ -0,0 +1,16 @@
+namespace Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency
+{
+    using System;
+    using System.Runtime.Serialization;
+
+    [Serializable]
+    public sealed class IdempotencyException : Exception
+    {
+        public IdempotencyException(string? message) : base(message)
+        { }
+
+        private IdempotencyException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        { }
+    }
+}

src/Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency/IdempotentCommandHandler.cs

@@ -0,0 +1,75 @@
+namespace Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Security.Cryptography;
+    using System.Text;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.EntityFrameworkCore;
+    using Utilities.HexByteConvertor;
+
+    public sealed class IdempotentCommandHandler : IIdempotentCommandHandler
+    {
+        private readonly ICommandHandlerResolver _bus;
+        private readonly IdempotencyContext _idempotencyContext;
+
+        public IdempotentCommandHandler(
+            ICommandHandlerResolver bus,
+            IdempotencyContext idempotencyContext)
+        {
+            _bus = bus;
+            _idempotencyContext = idempotencyContext;
+        }
+
+        public async Task<long> Dispatch(
+            Guid? commandId,
+            object command,
+            IDictionary<string, object> metadata,
+            CancellationToken cancellationToken)
+        {
+            ArgumentNullException.ThrowIfNull(commandId);
+            ArgumentNullException.ThrowIfNull(command);
+
+            // First check if the command id already has been processed
+            var possibleProcessedCommand = await _idempotencyContext
+                .ProcessedCommands
+                .Where(x => x.CommandId == commandId)
+                .ToDictionaryAsync(x => x.CommandContentHash, x => x, cancellationToken);
+
+            var contentHash = SHA512
+                .Create()
+                .ComputeHash(Encoding.UTF8.GetBytes(command.ToString()))
+                .ToHexString();
+
+            // It is possible we have a GUID collision, check the SHA-512 hash as well to see if it is really the same one.
+            // Do nothing if commandId with contenthash exists
+            if (possibleProcessedCommand.Any() && possibleProcessedCommand.ContainsKey(contentHash))
+            {
+                throw new IdempotencyException("Already processed");
+            }
+
+            var processedCommand = new ProcessedCommand(commandId.Value, contentHash);
+            try
+            {
+                // Store commandId in Command Store if it does not exist
+                await _idempotencyContext.ProcessedCommands.AddAsync(processedCommand, cancellationToken);
+                await _idempotencyContext.SaveChangesAsync(cancellationToken);
+
+                // Do work
+                return await _bus.Dispatch(commandId.Value,
+                    command,
+                    metadata,
+                    cancellationToken);
+            }
+            catch
+            {
+                // On exception, remove commandId from Command Store
+                _idempotencyContext.ProcessedCommands.Remove(processedCommand);
+                await _idempotencyContext.SaveChangesAsync(cancellationToken);
+                throw;
+            }
+        }
+    }
+}

src/Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency/paket.references

@@ -6,6 +6,7 @@ Microsoft.EntityFrameworkCore.SqlServer
 Newtonsoft.Json
 
 Be.Vlaanderen.Basisregisters.Converters.Timestamp
+Be.Vlaanderen.Basisregisters.Utilities.HexByteConvertor
 
 SourceLink.Embed.AllSourceFiles
 SourceLink.Copy.PdbFiles

src/Be.Vlaanderen.Basisregisters.CommandHandling.Idempotency/paket.template

@@ -16,7 +16,10 @@ description Lightweight infrastructure for doing command handling and eventsourc
 
 dependencies
   framework: net6.0
+    Be.Vlaanderen.Basisregisters.CommandHandling CURRENTVERSION
+
     Be.Vlaanderen.Basisregisters.Converters.Timestamp >= LOCKEDVERSION
+    Be.Vlaanderen.Basisregisters.Utilities.HexByteConvertor >= LOCKEDVERSION
 
     Microsoft.Data.SqlClient >= LOCKEDVERSION
     Microsoft.Extensions.Configuration >= LOCKEDVERSION