Added an example of closing and opening as one operation

Adjusted the closing the books sample to align with article content

Sample/ClosingTheBooks/PointOfSales.Api/Core/Marten/DocumentSessionExtensions.cs

@@ -1,30 +1,35 @@
 using Marten;
 
-namespace Helpdesk.Api.Core.Marten;
+namespace PointOfSales.Api.Core.Marten;
 
 public static class DocumentSessionExtensions
 {
     public static Task Add<T>(this IDocumentSession documentSession, string id, object[] events, CancellationToken ct)
+        where T : class =>
+        documentSession.Add<T, object>(id, events, ct);
+
+    public static Task Add<T, TEvent>(this IDocumentSession documentSession, string id, TEvent[] events,
+        CancellationToken ct)
         where T : class
     {
         if (events.Length == 0)
             return Task.CompletedTask;
 
-        documentSession.Events.StartStream<T>(id, events);
+        documentSession.Events.StartStream<T>(id, events.Cast<object>().ToArray());
         return documentSession.SaveChangesAsync(token: ct);
     }
 
-    public static Task GetAndUpdate<T>(
+    public static Task GetAndUpdate<T, TEvent>(
         this IDocumentSession documentSession,
         string id,
         int version,
-        Func<T, object[]> handle,
+        Func<T, TEvent[]> handle,
         CancellationToken ct
     ) where T : class =>
         documentSession.Events.WriteToAggregate<T>(id, version, stream =>
         {
             var result = handle(stream.Aggregate);
             if (result.Length != 0)
-                stream.AppendMany(result);
+                stream.AppendMany(result.Cast<object>().ToArray());
         }, ct);
 }

Sample/ClosingTheBooks/PointOfSales.Api/Program.cs

@@ -1,6 +1,5 @@
 using System.Text.Json.Serialization;
 using Helpdesk.Api.Core.Http.Middlewares.ExceptionHandling;
-using Helpdesk.Api.Core.Marten;
 using JasperFx.CodeGeneration;
 using Marten;
 using Marten.AspNetCore;
@@ -12,6 +11,7 @@
 using Marten.Services.Json;
 using Oakton;
 using PointOfSales.Api.Core;
+using PointOfSales.Api.Core.Marten;
 using PointOfSales.CashierShifts;
 using PointOfSales.CashRegister;
 using Weasel.Core;
@@ -22,6 +22,7 @@
 using static PointOfSales.CashierShifts.CashierShiftEvent;
 using static PointOfSales.Api.Core.ETagExtensions;
 using static System.DateTimeOffset;
+using static PointOfSales.CashierShifts.CloseAndOpenShift;
 using JsonOptions = Microsoft.AspNetCore.Http.Json.JsonOptions;
 
 var builder = WebApplication.CreateBuilder(args);
@@ -100,10 +101,12 @@ CancellationToken ct
         var lastClosedShift = await documentSession.GetLastCashierShift(cashRegisterId);
         var result = Decide(new OpenShift(cashRegisterId, body.CashierId, Now), lastClosedShift);
 
-        if (result.Length == 0 || result[0] is not ShiftOpened opened)
+        var opened = result.OfType<ShiftOpened>().SingleOrDefault();
+
+        if (opened == null)
             throw new InvalidOperationException("Cannot Open Shift");
 
-        await documentSession.Add<CashierShift>(opened.CashierShiftId, result, ct);
+        await documentSession.Add<CashierShift, CashierShiftEvent>(opened.CashierShiftId, result, ct);
 
         return Created(
             $"/api/cash-registers/{cashRegisterId}/cashier-shifts/{opened.CashierShiftId.ShiftNumber}",
@@ -125,7 +128,7 @@ CancellationToken ct
         var cashierShiftId = new CashierShiftId(cashRegisterId, shiftNumber);
         var transactionId = CombGuidIdGeneration.NewGuid().ToString();
 
-        return documentSession.GetAndUpdate<CashierShift>(cashierShiftId, ToExpectedVersion(eTag),
+        return documentSession.GetAndUpdate<CashierShift, CashierShiftEvent>(cashierShiftId, ToExpectedVersion(eTag),
             state => Decide(new RegisterTransaction(cashierShiftId, transactionId, body.Amount, Now), state), ct);
     }
 );
@@ -142,14 +145,43 @@ CancellationToken ct
     {
         var cashierShiftId = new CashierShiftId(cashRegisterId, shiftNumber);
 
-        return documentSession.GetAndUpdate<CashierShift>(cashierShiftId, ToExpectedVersion(eTag),
+        return documentSession.GetAndUpdate<CashierShift, CashierShiftEvent>(cashierShiftId, ToExpectedVersion(eTag),
             state => Decide(new CloseShift(cashierShiftId, body.DeclaredTender, Now), state), ct);
     }
 );
 
+
+// alternative showing how you could handle closing and opening in the same method
+// that require tho that shifts are continuous
+app.MapPost("/api/cash-registers/{cashRegisterId}/cashier-shifts/{shiftNumber:int}/close-and-open",
+    async (
+        IDocumentSession documentSession,
+        string cashRegisterId,
+        int shiftNumber,
+        CloseAndOpenShiftRequest body,
+        [FromIfMatchHeader] string eTag,
+        CancellationToken ct
+    ) =>
+    {
+        var command = new CloseAndOpenCommand(
+            new CashierShiftId(cashRegisterId, shiftNumber),
+            body.CashierId,
+            body.DeclaredTender,
+            Now
+        );
+
+        var openedCashierId = await documentSession.CloseAndOpenCashierShift(command, ToExpectedVersion(eTag), ct);
+
+        return Created(
+            $"/api/cash-registers/{cashRegisterId}/cashier-shifts/{openedCashierId.ShiftNumber}",
+            cashRegisterId
+        );
+    }
+);
+
 app.MapGet("/api/cash-registers/{cashRegisterId}/cashier-shifts/{shiftNumber:int}",
     (HttpContext context, IQuerySession querySession, string cashRegisterId, int shiftNumber) =>
-        querySession.Json.WriteById<CashierShiftDetails>(new CashierShiftId(cashRegisterId, shiftNumber), context)
+        querySession.Json.WriteById<CurrentCashierShift>(new CashierShiftId(cashRegisterId, shiftNumber), context)
 );
 
 
@@ -174,6 +206,11 @@ public record CloseShiftRequest(
     decimal DeclaredTender
 );
 
+public record CloseAndOpenShiftRequest(
+    decimal DeclaredTender,
+    string CashierId
+);
+
 
 public partial class Program
 {

Sample/ClosingTheBooks/PointOfSales/CashRegister/CashRegister.cs

@@ -1,11 +1,5 @@
 namespace PointOfSales.CashRegister;
 
-public static class CashRegisterId
-{
-    public static string From(string workstation) =>
-        $"urn:cash_register:{workstation}";
-}
-
 public record CashRegister(string Id)
 {
     public static CashRegister Create(CashRegisterInitialized @event) =>

Sample/ClosingTheBooks/PointOfSales/CashierShifts/CashierShift.cs

@@ -1,5 +1,3 @@
-using System.Text.Json.Serialization;
-
 namespace PointOfSales.CashierShifts;
 
 using System;
@@ -47,21 +45,21 @@ public record CashierShiftId(string CashRegisterId, int ShiftNumber)
     public override string ToString() => $"urn:cashier_shift:{CashRegisterId}:{ShiftNumber}";
 }
 
-public abstract record CashierShiftEvent(CashierShiftId CashierShiftId)
+public abstract record CashierShiftEvent
 {
     public record ShiftOpened(
         CashierShiftId CashierShiftId,
         string CashierId,
         decimal Float,
         DateTimeOffset StartedAt
-    ): CashierShiftEvent(CashierShiftId);
+    ): CashierShiftEvent;
 
     public record TransactionRegistered(
         CashierShiftId CashierShiftId,
         string TransactionId,
         decimal Amount,
         DateTimeOffset RegisteredAt
-    ): CashierShiftEvent(CashierShiftId);
+    ): CashierShiftEvent;
 
     public record ShiftClosed(
         CashierShiftId CashierShiftId,
@@ -70,5 +68,7 @@ public record ShiftClosed(
         decimal ShortageAmount,
         decimal FinalFloat,
         DateTimeOffset ClosedAt
-    ): CashierShiftEvent(CashierShiftId);
+    ): CashierShiftEvent;
+
+    private CashierShiftEvent(){}
 }

Sample/ClosingTheBooks/PointOfSales/CashierShifts/CashierShiftDecider.cs

@@ -24,32 +24,21 @@ public record CloseShift(
         decimal DeclaredTender,
         DateTimeOffset Now
     ): CashierShiftCommand;
+
+    private CashierShiftCommand() { }
 }
 
 public static class CashierShiftDecider
 {
-    public static object[] Decide(CashierShiftCommand command, CashierShift state) =>
+    public static CashierShiftEvent[] Decide(CashierShiftCommand command, CashierShift state) =>
         (command, state) switch
         {
             (OpenShift open, NonExisting) =>
-            [
-                new ShiftOpened(
-                    new CashierShiftId(open.CashRegisterId, 1),
-                    open.CashierId,
-                    0,
-                    open.Now
-                )
-            ],
+                [Open(open.CashierId, open.CashRegisterId, 1, 0, open.Now)],
 
             (OpenShift open, Closed closed) =>
             [
-
-                new ShiftOpened(
-                    new CashierShiftId(open.CashRegisterId, closed.ShiftId.ShiftNumber + 1),
-                    open.CashierId,
-                    closed.FinalFloat,
-                    open.Now
-                )
+                Open(open.CashierId, open.CashRegisterId, closed.ShiftId.ShiftNumber + 1, closed.FinalFloat, open.Now)
             ],
 
             (OpenShift, Opened) => [],
@@ -79,4 +68,20 @@ public static class CashierShiftDecider
 
             _ => throw new InvalidOperationException($"Cannot run {command.GetType().Name} on {state.GetType().Name}")
         };
+
+    private static ShiftOpened Open(
+        string cashierId,
+        string cashRegisterId,
+        int shiftNumber,
+        decimal @float,
+        DateTimeOffset now) =>
+        new(
+            new CashierShiftId(cashRegisterId, shiftNumber),
+            cashierId,
+            @float,
+            now
+        );
 }
+
+
+

Sample/ClosingTheBooks/PointOfSales/CashierShifts/CloseAndOpenShift.cs

@@ -0,0 +1,60 @@
+using Marten;
+
+namespace PointOfSales.CashierShifts;
+
+using static CashierShiftEvent;
+using static CashierShiftCommand;
+using static CashierShiftDecider;
+using CommandResult = (CashierShiftId StreamId, CashierShiftEvent[] Events);
+
+public record CloseAndOpenCommand(
+    CashierShiftId CashierShiftId,
+    string CashierId,
+    decimal DeclaredTender,
+    DateTimeOffset Now
+);
+
+public static class CloseAndOpenShift
+{
+    public static (CommandResult, CommandResult) Handle(CloseAndOpenCommand command, CashierShift currentShift)
+    {
+        var (currentShiftId, cashierId, declaredTender, now) = command;
+        var closingResult = Decide(new CloseShift(currentShiftId, declaredTender, now), currentShift);
+
+        currentShift = closingResult.Aggregate(currentShift, (current, @event) => current.Apply(@event));
+
+        var openResult = Decide(new OpenShift(currentShiftId, cashierId, now), currentShift);
+
+        // double check if it was actually
+        var opened = openResult.OfType<ShiftOpened>().SingleOrDefault();
+        if (opened == null)
+            throw new InvalidOperationException("Cannot open new shift!");
+
+        return ((currentShiftId, closingResult), (opened.CashierShiftId, openResult));
+    }
+
+    public static async Task<CashierShiftId> CloseAndOpenCashierShift(
+        this IDocumentSession documentSession,
+        CloseAndOpenCommand command,
+        int version,
+        CancellationToken ct
+    )
+    {
+        var currentShift =
+            await documentSession.Events.AggregateStreamAsync<CashierShift>(command.CashierShiftId, token: ct) ??
+            new CashierShift.NonExisting();
+
+        var (closingResult, openResult) = Handle(command, currentShift);
+
+        // Append Closing result to the old stream
+        if (closingResult.Events.Length > 0)
+            documentSession.Events.Append(closingResult.StreamId, version, closingResult.Events.AsEnumerable());
+
+        if (openResult.Events.Length > 0)
+            documentSession.Events.StartStream<CashierShift>(openResult.StreamId, openResult.Events.AsEnumerable());
+
+        await documentSession.SaveChangesAsync(ct);
+
+        return openResult.StreamId;
+    }
+}

Sample/ClosingTheBooks/PointOfSales/CashierShifts/CashierShiftDetails.cs → Sample/ClosingTheBooks/PointOfSales/CashierShifts/CurrentCashierShift.cs

@@ -4,7 +4,7 @@ namespace PointOfSales.CashierShifts;
 
 using static CashierShiftEvent;
 
-public record CashierShiftDetails(
+public record CurrentCashierShift(
     string Id,
     string CashierRegisterId,
     int ShiftNumber,
@@ -13,7 +13,10 @@ public record CashierShiftDetails(
     int TransactionsCount,
     DateTimeOffset StartedAt,
     ClosingDetails? ClosingDetails = null
-);
+)
+{
+    public int Version { get; set; }
+}
 
 public record ClosingDetails(
     decimal? DeclaredTender = null,
@@ -23,9 +26,9 @@ public record ClosingDetails(
     DateTimeOffset? ClosedAt = null
 );
 
-public class CashierShiftDetailsProjection: SingleStreamProjection<CashierShiftDetails>
+public class CurrentCashierShiftProjection: SingleStreamProjection<CurrentCashierShift>
 {
-    public static CashierShiftDetails Create(ShiftOpened @event) =>
+    public static CurrentCashierShift Create(ShiftOpened @event) =>
         new(
             @event.CashierShiftId,
             @event.CashierShiftId.CashRegisterId,
@@ -36,10 +39,10 @@ public class CashierShiftDetailsProjection: SingleStreamProjection<CashierShiftD
             @event.StartedAt
         );
 
-    public CashierShiftDetails Apply(TransactionRegistered @event, CashierShiftDetails details) =>
+    public CurrentCashierShift Apply(TransactionRegistered @event, CurrentCashierShift details) =>
         details with { Float = details.Float + @event.Amount, TransactionsCount = details.TransactionsCount + 1 };
 
-    public CashierShiftDetails Apply(ShiftClosed @event, CashierShiftDetails details) =>
+    public CurrentCashierShift Apply(ShiftClosed @event, CurrentCashierShift details) =>
         details with
         {
             ClosingDetails = new ClosingDetails(