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

wolverine/a-frame-architecture/FinancialApi.Application/Account.cs

@@ -0,0 +1,43 @@
+namespace FinancialApi.Application;
+
+public record Account(int Id, decimal Balance)
+{
+    public Account ApplyFee(decimal amount)
+    {
+        if (amount <= 0)
+        {
+            throw new ArgumentException("Fee must be positive.");
+        }
+            
+        if (Balance - amount < 0)
+        {
+            throw new InvalidOperationException("Insufficient funds.");
+        }
+
+        return this with { Balance = Balance - amount };
+    }
+    
+    public Account Debit(decimal amount)
+    {
+        if (amount <= 0)
+        {
+            throw new ArgumentException("Debit amount must be positive.");
+        }
+        if (Balance - amount < 0)
+        {
+            throw new InvalidOperationException("Insufficient funds.");
+        }
+        
+        return this with { Balance = Balance - amount };
+    }
+
+    public Account Credit(decimal amount)
+    {
+        if (amount <= 0)
+        {
+            throw new ArgumentException("Credit amount must be positive.");
+        }
+        
+        return this with { Balance = Balance + amount };
+    }
+}

wolverine/a-frame-architecture/FinancialApi.Application/Class1.cs

@@ -1,16 +0,0 @@
-namespace FinancialApi.Application;
-
-public record Account(int Id, decimal Balance)
-{
-    public Account ApplyFee(decimal amount)
-    {
-        if (amount <= 0) 
-            throw new ArgumentException("Fee must be positive.");
-            
-        if (Balance - amount < 0)
-            throw new InvalidOperationException("Insufficient funds.");
-
-        // Returns a brand new record with the updated balance
-        return this with { Balance = Balance - amount };
-    }
-}

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

@@ -3,12 +3,8 @@ using Microsoft.EntityFrameworkCore;
 
 namespace FinancialApi.Infrastructure;
 
-public class AccountDbContext : DbContext
+public class AccountDbContext(DbContextOptions<AccountDbContext> options) : DbContext(options)
 {
-    public AccountDbContext(DbContextOptions<AccountDbContext> options) : base(options)
-    {
-    }
-
     public DbSet<Account> Accounts => Set<Account>();
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)

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

@@ -1,10 +1,9 @@
 using FinancialApi.Application;
-using FinancialApi.Infrastructure;
 using Microsoft.EntityFrameworkCore;
 using Wolverine.Attributes;
 using Wolverine.Persistence;
 
-namespace FinancialApi;
+namespace FinancialApi.Infrastructure;
 
 public static class ApplyFeeHandler
 {

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);
+    }
+}

wolverine/a-frame-architecture/FinancialApi/FinancialApi.http

@@ -3,7 +3,7 @@
 GET {{FinancialApi_HostAddress}}/weatherforecast/
 Accept: application/json
 
-###
+### Apply Fee to an Account
 
 POST {{FinancialApi_HostAddress}}/accounts/apply-fee
 Accept: application/json
@@ -14,4 +14,13 @@ Content-Type: application/json
   "amount": 5.0
 }
 
-###
+### Transfer Between Accounts
+
+POST {{FinancialApi_HostAddress}}/accounts/transfer
+Content-Type: application/json
+
+{
+  "sourceAccountId": 1,
+  "destinationAccountId": 2,
+  "amount": 30.00
+}

wolverine/a-frame-architecture/FinancialApi/Program.cs

@@ -53,4 +53,10 @@ app.MapPost("/accounts/apply-fee", async (ApplyFeeCommand cmd, IMessageBus bus)
     return Results.Accepted();
 });
 
+app.MapPost("/accounts/transfer", async (TransferFundsCommand cmd, IMessageBus bus) =>
+{
+    await bus.InvokeAsync(cmd); 
+    return Results.Accepted();
+});
+
 app.Run();