Added a transfer funds handler using a-frame and wolverine.

wolverine/a-frame-architecture/FinancialApi.Infrastructure/TransferFundsHandler.cs

@@ -0,0 +1,43 @@
+using FinancialApi.Application;
+using Microsoft.EntityFrameworkCore;
+using Wolverine.Attributes;
+using Wolverine.Persistence;
+
+namespace FinancialApi.Infrastructure;
+
+public record TransferFundsCommand(int SourceAccountId, int DestinationAccountId, decimal Amount);
+
+public record FundsTransferredEvent(int SourceAccountId, int DestinationAccountId, decimal Amount);
+
+// A simple container to pass our loaded entities into the pure function
+public record TransferPair(Account Source, Account Destination);
+
+public static class TransferFundsHandler
+{
+    public static async Task<TransferPair?> LoadAsync(TransferFundsCommand cmd, AccountDbContext db)
+    {
+        var source = await db.Accounts.AsNoTracking().FirstOrDefaultAsync(x => x.Id == cmd.SourceAccountId);
+        var dest = await db.Accounts.AsNoTracking().FirstOrDefaultAsync(x => x.Id == cmd.DestinationAccountId);
+
+        if (source == null || dest == null) return null; // Wolverine drops into a 404/Problem if null
+
+        return new TransferPair(source, dest);
+    }
+
+    [Transactional]
+    public static (
+        IStorageAction<Account> SourceWrite,
+        IStorageAction<Account> DestWrite,
+        FundsTransferredEvent Event
+        ) Handle(TransferFundsCommand cmd, TransferPair pair)
+    {
+        var updatedSource = pair.Source.Debit(cmd.Amount);
+        var updatedDest = pair.Destination.Credit(cmd.Amount);
+
+        var sourcePersistence = Storage.Update(updatedSource);
+        var destPersistence = Storage.Update(updatedDest);
+        var @event = new FundsTransferredEvent(cmd.SourceAccountId, cmd.DestinationAccountId, cmd.Amount);
+
+        return (sourcePersistence, destPersistence, @event);
+    }
+}