discounts überarbeitet

Webshop.Api/Controllers/Admin/AdminDiscountsController.cs

@@ -1,9 +1,10 @@
 // src/Webshop.Api/Controllers/Admin/AdminDiscountsController.cs
-using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Webshop.Application;
 using Webshop.Application.DTOs.Discounts;
 using Webshop.Application.Services.Admin.Interfaces;
 
@@ -58,11 +59,20 @@ namespace Webshop.Api.Controllers.Admin
         /// </remarks>
         /// <param name="discountDto">Das Datenobjekt des zu erstellenden Rabatts.</param>
         [HttpPost]
+        [ProducesResponseType(typeof(DiscountDto), StatusCodes.Status201Created)]
+        [ProducesResponseType(StatusCodes.Status400BadRequest)]
         public async Task<ActionResult<DiscountDto>> CreateDiscount([FromBody] DiscountDto discountDto)
         {
             if (!ModelState.IsValid) return BadRequest(ModelState);
-            var createdDiscount = await _adminDiscountService.CreateDiscountAsync(discountDto);
+
-            return CreatedAtAction(nameof(GetDiscountById), new { id = createdDiscount.Id }, createdDiscount);
+            var result = await _adminDiscountService.CreateDiscountAsync(discountDto);
+
+            if (result.Type == ServiceResultType.Success)
+            {
+                return CreatedAtAction(nameof(GetDiscountById), new { id = result.Value!.Id }, result.Value);
+            }
+
+            return BadRequest(new { Message = result.ErrorMessage });
         }
 
         /// <summary>
@@ -71,15 +81,23 @@ namespace Webshop.Api.Controllers.Admin
         /// <param name="id">Die ID des zu aktualisierenden Rabatts.</param>
         /// <param name="discountDto">Die neuen Daten f<>r den Rabatt.</param>
         [HttpPut("{id}")]
+        [ProducesResponseType(StatusCodes.Status204NoContent)]
+        [ProducesResponseType(StatusCodes.Status400BadRequest)]
+        [ProducesResponseType(StatusCodes.Status404NotFound)]
         public async Task<IActionResult> UpdateDiscount(Guid id, [FromBody] DiscountDto discountDto)
         {
-            if (id != discountDto.Id) return BadRequest();
+            if (id != discountDto.Id) return BadRequest("ID in URL und Body stimmen nicht <20>berein.");
             if (!ModelState.IsValid) return BadRequest(ModelState);
 
-            var success = await _adminDiscountService.UpdateDiscountAsync(discountDto);
+            var result = await _adminDiscountService.UpdateDiscountAsync(discountDto);
-            if (!success) return NotFound();
 
-            return NoContent();
+            return result.Type switch
+            {
+                ServiceResultType.Success => NoContent(),
+                ServiceResultType.NotFound => NotFound(new { Message = result.ErrorMessage }),
+                ServiceResultType.InvalidInput => BadRequest(new { Message = result.ErrorMessage }),
+                _ => StatusCode(StatusCodes.Status500InternalServerError, "Ein unerwarteter Fehler ist aufgetreten.")
+            };
         }
 
         /// <summary>
@@ -87,12 +105,18 @@ namespace Webshop.Api.Controllers.Admin
         /// </summary>
         /// <param name="id">Die ID des zu l<>schenden Rabatts.</param>
         [HttpDelete("{id}")]
+        [ProducesResponseType(StatusCodes.Status204NoContent)]
+        [ProducesResponseType(StatusCodes.Status404NotFound)]
         public async Task<IActionResult> DeleteDiscount(Guid id)
         {
-            var success = await _adminDiscountService.DeleteDiscountAsync(id);
+            var result = await _adminDiscountService.DeleteDiscountAsync(id);
-            if (!success) return NotFound();
 
-            return NoContent();
+            return result.Type switch
+            {
+                ServiceResultType.Success => NoContent(),
+                ServiceResultType.NotFound => NotFound(new { Message = result.ErrorMessage }),
+                _ => StatusCode(StatusCodes.Status500InternalServerError, "Ein unerwarteter Fehler ist aufgetreten.")
+            };
         }
     }
 }

Webshop.Application/DTOs/Orders/CreateOrderItemDto.cs

@@ -1,6 +1,7 @@
 // Auto-generiert von CreateWebshopFiles.ps1
 using System;
 using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
 using System.Threading.Tasks;
 
 
@@ -8,6 +9,7 @@ namespace Webshop.Application.DTOs.Orders
 {
     public class CreateOrderItemDto
     {
+        [Required]
         public Guid ProductId { get; set; }
         public Guid? ProductVariantId { get; set; }
         public int Quantity { get; set; }

Webshop.Application/Services/Admin/AdminDiscountService.cs

@@ -1,4 +1,5 @@
 // src/Webshop.Application/Services/Admin/AdminDiscountService.cs
+using Microsoft.EntityFrameworkCore;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -8,16 +9,19 @@ using Webshop.Application.Services.Admin.Interfaces;
 using Webshop.Domain.Entities;
 using Webshop.Domain.Enums;
 using Webshop.Domain.Interfaces;
+using Webshop.Infrastructure.Data;
 
 namespace Webshop.Application.Services.Admin
 {
     public class AdminDiscountService : IAdminDiscountService
     {
         private readonly IDiscountRepository _discountRepository;
+        private readonly ApplicationDbContext _context; // F<>r Unique-Pr<50>fungen
 
-        public AdminDiscountService(IDiscountRepository discountRepository)
+        public AdminDiscountService(IDiscountRepository discountRepository, ApplicationDbContext context)
         {
             _discountRepository = discountRepository;
+            _context = context;
         }
 
         public async Task<IEnumerable<DiscountDto>> GetAllDiscountsAsync()
@@ -32,19 +36,41 @@ namespace Webshop.Application.Services.Admin
             return discount != null ? MapToDto(discount) : null;
         }
 
-        public async Task<DiscountDto?> CreateDiscountAsync(DiscountDto discountDto)
+        public async Task<ServiceResult<DiscountDto>> CreateDiscountAsync(DiscountDto discountDto)
         {
+            // Validierung: Gutscheincode muss eindeutig sein, wenn er ben<65>tigt wird
+            if (discountDto.RequiresCouponCode && !string.IsNullOrEmpty(discountDto.CouponCode))
+            {
+                var existing = await _context.Discounts.FirstOrDefaultAsync(d => d.CouponCode == discountDto.CouponCode);
+                if (existing != null)
+                {
+                    return ServiceResult.Fail<DiscountDto>(ServiceResultType.InvalidInput, $"Der Gutscheincode '{discountDto.CouponCode}' existiert bereits.");
+                }
+            }
+
             var discount = MapToEntity(discountDto);
             discount.Id = Guid.NewGuid();
 
             await _discountRepository.AddAsync(discount);
-            return MapToDto(discount);
+            return ServiceResult.Ok(MapToDto(discount));
         }
 
-        public async Task<bool> UpdateDiscountAsync(DiscountDto discountDto)
+        public async Task<ServiceResult> UpdateDiscountAsync(DiscountDto discountDto)
         {
             var existingDiscount = await _discountRepository.GetByIdAsync(discountDto.Id);
-            if (existingDiscount == null) return false;
+            if (existingDiscount == null)
+            {
+                return ServiceResult.Fail(ServiceResultType.NotFound, "Rabatt nicht gefunden.");
+            }
+
+            if (discountDto.RequiresCouponCode && !string.IsNullOrEmpty(discountDto.CouponCode))
+            {
+                var existing = await _context.Discounts.FirstOrDefaultAsync(d => d.CouponCode == discountDto.CouponCode && d.Id != discountDto.Id);
+                if (existing != null)
+                {
+                    return ServiceResult.Fail(ServiceResultType.InvalidInput, $"Der Gutscheincode '{discountDto.CouponCode}' wird bereits von einem anderen Rabatt verwendet.");
+                }
+            }
 
             // Update simple properties
             existingDiscount.Name = discountDto.Name;
@@ -59,33 +85,39 @@ namespace Webshop.Application.Services.Admin
             existingDiscount.MinimumOrderAmount = discountDto.MinimumOrderAmount;
             existingDiscount.MaximumUsageCount = discountDto.MaximumUsageCount;
 
+            // << HIER IST DER WICHTIGE, WIEDERHERGESTELLTE TEIL >>
             // Sync assigned products
             existingDiscount.ProductDiscounts.Clear();
             foreach (var productId in discountDto.AssignedProductIds)
             {
-                existingDiscount.ProductDiscounts.Add(new ProductDiscount { ProductId = productId });
+                existingDiscount.ProductDiscounts.Add(new ProductDiscount { DiscountId = existingDiscount.Id, ProductId = productId });
             }
 
             // Sync assigned categories
             existingDiscount.categorieDiscounts.Clear();
             foreach (var categoryId in discountDto.AssignedCategoryIds)
             {
-                existingDiscount.categorieDiscounts.Add(new CategorieDiscount { categorieId = categoryId });
+                existingDiscount.categorieDiscounts.Add(new CategorieDiscount { DiscountId = existingDiscount.Id, categorieId = categoryId });
             }
+            // << ENDE DES WICHTIGEN TEILS >>
 
             await _discountRepository.UpdateAsync(existingDiscount);
-            return true;
+            return ServiceResult.Ok();
         }
 
-        public async Task<bool> DeleteDiscountAsync(Guid id)
+        public async Task<ServiceResult> DeleteDiscountAsync(Guid id)
         {
             var discount = await _discountRepository.GetByIdAsync(id);
-            if (discount == null) return false;
+            if (discount == null)
+            {
+                return ServiceResult.Fail(ServiceResultType.NotFound, "Rabatt nicht gefunden.");
+            }
 
             await _discountRepository.DeleteAsync(id);
-            return true;
+            return ServiceResult.Ok();
         }
 
+
         // Helper methods for mapping
         private DiscountDto MapToDto(Discount discount)
         {

Webshop.Application/Services/Admin/Interfaces/IAdminDiscountService.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
+using Webshop.Application; // << NEU: F<>r ServiceResult >>
 using Webshop.Application.DTOs.Discounts;
 
 namespace Webshop.Application.Services.Admin.Interfaces
@@ -10,8 +11,8 @@ namespace Webshop.Application.Services.Admin.Interfaces
     {
         Task<IEnumerable<DiscountDto>> GetAllDiscountsAsync();
         Task<DiscountDto?> GetDiscountByIdAsync(Guid id);
-        Task<DiscountDto?> CreateDiscountAsync(DiscountDto discountDto);
+        Task<ServiceResult<DiscountDto>> CreateDiscountAsync(DiscountDto discountDto);
-        Task<bool> UpdateDiscountAsync(DiscountDto discountDto);
+        Task<ServiceResult> UpdateDiscountAsync(DiscountDto discountDto);
-        Task<bool> DeleteDiscountAsync(Guid id);
+        Task<ServiceResult> DeleteDiscountAsync(Guid id);
     }
 }

Webshop.Application/Services/Customers/CheckoutService.cs

@@ -40,16 +40,33 @@ namespace Webshop.Application.Services.Customers
             _discountService = discountService;
         }
 
-        public async Task<(bool Success, OrderDetailDto? CreatedOrder, string? ErrorMessage)> CreateOrderAsync(CreateOrderDto orderDto, string userId)
+        public async Task<(bool Success, OrderDetailDto? CreatedOrder, string? ErrorMessage)> CreateOrderAsync(CreateOrderDto orderDto, string? userId)
         {
-            // Startet eine Datenbank-Transaktion. Entweder alles klappt, oder alles wird zurückgerollt.
             await using var transaction = await _context.Database.BeginTransactionAsync();
-
             try
             {
-                // --- 1. Validierung der Eingabedaten ---
+                // --- 1. Validierung von Kunde, Adressen und Methoden ---
-                var customer = await _customerRepository.GetByUserIdAsync(userId);
+                Customer? customer = null;
-                if (customer == null) return (false, null, "Kundenprofil nicht gefunden.");
+                if (!string.IsNullOrEmpty(userId))
+                {
+                    customer = await _customerRepository.GetByUserIdAsync(userId);
+                    if (customer == null) return (false, null, "Kundenprofil nicht gefunden.");
+
+                    // Validiere, dass die Adressen zum eingeloggten Kunden gehören
+                    if (!await _context.Addresses.AnyAsync(a => a.Id == orderDto.ShippingAddressId && a.CustomerId == customer.Id) ||
+                        !await _context.Addresses.AnyAsync(a => a.Id == orderDto.BillingAddressId && a.CustomerId == customer.Id))
+                    {
+                        return (false, null, "Ungültige oder nicht zugehörige Liefer- oder Rechnungsadresse.");
+                    }
+                }
+                else
+                {
+                    // Gast-Checkout: Validierung der Gast-Daten
+                    if (string.IsNullOrWhiteSpace(orderDto.GuestEmail))
+                        return (false, null, "Für Gastbestellungen ist eine E-Mail-Adresse erforderlich.");
+                    // Hinweis: Bei Gastbestellungen müssten die Adress-DTOs mitgesendet und hier neue Adressen erstellt werden.
+                    // Der Einfachheit halber nehmen wir an, die Adress-IDs sind gültig, aber nicht mit einem Kunden verknüpft.
+                }
 
                 var shippingMethod = await _shippingMethodRepository.GetByIdAsync(orderDto.ShippingMethodId);
                 if (shippingMethod == null || !shippingMethod.IsActive) return (false, null, "Ungültige oder inaktive Versandmethode.");
@@ -57,33 +74,27 @@ namespace Webshop.Application.Services.Customers
                 var paymentMethod = await _context.PaymentMethods.FindAsync(orderDto.PaymentMethodId);
                 if (paymentMethod == null || !paymentMethod.IsActive) return (false, null, "Ungültige oder inaktive Zahlungsmethode.");
 
-                if (!await _context.Addresses.AnyAsync(a => a.Id == orderDto.ShippingAddressId && a.CustomerId == customer.Id) ||
-                    !await _context.Addresses.AnyAsync(a => a.Id == orderDto.BillingAddressId && a.CustomerId == customer.Id))
-                {
-                    return (false, null, "Ungültige oder nicht zugehörige Liefer- oder Rechnungsadresse.");
-                }
-
                 // --- 2. Artikel verarbeiten und Lagerbestand prüfen ---
                 var orderItems = new List<OrderItem>();
+                var productIds = orderDto.Items.Select(i => i.ProductId).ToList();
+                var products = await _context.Products.Where(p => productIds.Contains(p.Id)).ToListAsync();
                 decimal itemsTotal = 0;
 
                 foreach (var itemDto in orderDto.Items)
                 {
-                    var product = await _context.Products.FindAsync(itemDto.ProductId);
+                    var product = products.FirstOrDefault(p => p.Id == itemDto.ProductId);
                     if (product == null || !product.IsActive)
                     {
                         await transaction.RollbackAsync();
-                        return (false, null, $"Produkt mit ID {itemDto.ProductId} ist nicht verfügbar.");
+                        return (false, null, $"Ein Produkt im Warenkorb ist nicht mehr verfügbar.");
                     }
-
                     if (product.StockQuantity < itemDto.Quantity)
                     {
                         await transaction.RollbackAsync();
-                        return (false, null, $"Nicht genügend Lagerbestand für '{product.Name}'. Verfügbar: {product.StockQuantity}.");
+                        return (false, null, $"Nicht genügend Lagerbestand für '{product.Name}'. Verfügbar: {product.StockQuantity}, benötigt: {itemDto.Quantity}.");
                     }
 
-                    // Lagerbestand reduzieren
+                    product.StockQuantity -= itemDto.Quantity; // Lagerbestand reduzieren
-                    product.StockQuantity -= itemDto.Quantity;
 
                     var orderItem = new OrderItem
                     {
@@ -95,13 +106,13 @@ namespace Webshop.Application.Services.Customers
                         UnitPrice = product.Price,
                         TotalPrice = product.Price * itemDto.Quantity
                     };
-
                     orderItems.Add(orderItem);
                     itemsTotal += orderItem.TotalPrice;
                 }
 
                 // --- 3. Preise, Rabatte, Steuern und Gesamtbetrag berechnen ---
-                decimal discountAmount = await _discountService.CalculateDiscountAsync(orderItems, orderDto.CouponCode);
+                var discountResult = await _discountService.CalculateDiscountAsync(orderItems, orderDto.CouponCode);
+                decimal discountAmount = discountResult.TotalDiscountAmount;
                 decimal shippingCost = shippingMethod.BaseCost;
                 decimal subTotal = itemsTotal + shippingCost - discountAmount;
                 if (subTotal < 0) subTotal = 0;
@@ -113,47 +124,53 @@ namespace Webshop.Application.Services.Customers
                 // --- 4. Bestellung erstellen ---
                 var newOrder = new Order
                 {
-                    CustomerId = customer.Id,
+                    CustomerId = customer?.Id,
+                    GuestEmail = customer == null ? orderDto.GuestEmail : null,
+                    GuestPhoneNumber = customer == null ? orderDto.GuestPhoneNumber : null,
                     OrderNumber = $"WS-{DateTime.UtcNow:yyyyMMdd}-{new Random().Next(1000, 9999)}",
                     OrderDate = DateTimeOffset.UtcNow,
                     OrderStatus = OrderStatus.Pending.ToString(),
-                    PaymentStatus = PaymentStatus.Pending.ToString(), // Wird später vom Zahlungsanbieter aktualisiert
+                    PaymentStatus = PaymentStatus.Pending.ToString(),
-
                     OrderTotal = orderTotal,
                     ShippingCost = shippingCost,
                     TaxAmount = taxAmount,
                     DiscountAmount = discountAmount,
-
                     PaymentMethod = paymentMethod.Name,
                     PaymentMethodId = paymentMethod.Id,
                     ShippingMethodId = shippingMethod.Id,
-
                     BillingAddressId = orderDto.BillingAddressId,
                     ShippingAddressId = orderDto.ShippingAddressId,
-
                     OrderItems = orderItems
                 };
+                await _orderRepository.AddAsync(newOrder);
 
-                await _orderRepository.AddAsync(newOrder); // Speichert die Bestellung und die Artikel
+                // --- 5. Rabattnutzung erhöhen ---
-                await _context.SaveChangesAsync(); // Speichert die Lagerbestandsänderungen
+                if (discountResult.AppliedDiscountIds.Any())
+                {
+                    var appliedDiscounts = await _context.Discounts
+                        .Where(d => discountResult.AppliedDiscountIds.Contains(d.Id))
+                        .ToListAsync();
+                    foreach (var discount in appliedDiscounts)
+                    {
+                        discount.CurrentUsageCount++;
+                    }
+                }
 
-                await transaction.CommitAsync(); // Transaktion erfolgreich abschließen
+                await _context.SaveChangesAsync(); // Speichert Lagerbestandsänderungen & Rabattnutzung
-
+                await transaction.CommitAsync();
-                // --- 5. Erfolgreiche Antwort erstellen ---
-                var createdOrder = await _orderRepository.GetByIdAsync(newOrder.Id); // Lade die erstellte Bestellung mit allen Details
-                var orderDetailDto = MapToOrderDetailDto(createdOrder!); // Mapping zum DTO
 
+                // --- 6. Erfolgreiche Antwort erstellen ---
+                var createdOrder = await _orderRepository.GetByIdAsync(newOrder.Id);
+                var orderDetailDto = MapToOrderDetailDto(createdOrder!);
                 return (true, orderDetailDto, null);
             }
             catch (Exception ex)
             {
                 await transaction.RollbackAsync();
-                // Hier Fehler loggen
                 return (false, null, $"Ein unerwarteter Fehler ist aufgetreten: {ex.Message}");
             }
         }
 
-        // Helper-Methode für das Mapping, um Code-Duplizierung zu vermeiden
         private OrderDetailDto MapToOrderDetailDto(Order order)
         {
             return new OrderDetailDto
@@ -164,10 +181,35 @@ namespace Webshop.Application.Services.Customers
                 CustomerId = order.CustomerId,
                 Status = Enum.Parse<OrderStatus>(order.OrderStatus),
                 TotalAmount = order.OrderTotal,
-                ShippingAddress = new AddressDto { /* Mapping */ },
+                ShippingAddress = new AddressDto
-                BillingAddress = new AddressDto { /* Mapping */ },
+                {
+                    Id = order.ShippingAddress.Id,
+                    FirstName = order.ShippingAddress.FirstName,
+                    LastName = order.ShippingAddress.LastName,
+                    Street = order.ShippingAddress.Street,
+                    HouseNumber = order.ShippingAddress.HouseNumber,
+                    City = order.ShippingAddress.City,
+                    PostalCode = order.ShippingAddress.PostalCode,
+                    Country = order.ShippingAddress.Country,
+                    Type = order.ShippingAddress.Type
+                },
+                BillingAddress = new AddressDto
+                {
+                    Id = order.BillingAddress.Id,
+                    FirstName = order.BillingAddress.FirstName,
+                    LastName = order.BillingAddress.LastName,
+                    Street = order.BillingAddress.Street,
+                    HouseNumber = order.BillingAddress.HouseNumber,
+                    City = order.BillingAddress.City,
+                    PostalCode = order.BillingAddress.PostalCode,
+                    Country = order.BillingAddress.Country,
+                    Type = order.BillingAddress.Type
+                },
                 PaymentMethod = order.PaymentMethod,
                 PaymentStatus = Enum.Parse<PaymentStatus>(order.PaymentStatus),
+                ShippingTrackingNumber = order.ShippingTrackingNumber,
+                ShippedDate = order.ShippedDate,
+                DeliveredDate = order.DeliveredDate,
                 OrderItems = order.OrderItems.Select(oi => new OrderItemDto
                 {
                     Id = oi.Id,

Webshop.Application/Services/Public/DiscountService.cs

@@ -6,85 +6,113 @@ using System.Linq;
 using System.Threading.Tasks;
 using Webshop.Application.Services.Public.Interfaces;
 using Webshop.Domain.Entities;
-using Webshop.Domain.Interfaces;
+using Webshop.Domain.Enums;
 using Webshop.Infrastructure.Data;
 
 namespace Webshop.Application.Services.Public
 {
     public class DiscountService : IDiscountService
     {
-        private readonly ApplicationDbContext _context; // Direkter Zugriff auf DbSets
+        private readonly ApplicationDbContext _context;
-        private readonly IDiscountRepository _discountRepository;
-        private readonly IProductRepository _productRepository;
 
-        public DiscountService(
+        public DiscountService(ApplicationDbContext context)
-            ApplicationDbContext context,
-            IDiscountRepository discountRepository,
-            IProductRepository productRepository)
         {
             _context = context;
-            _discountRepository = discountRepository;
-            _productRepository = productRepository;
         }
 
-        public async Task<decimal> CalculateDiscountAsync(List<OrderItem> orderItems, string? couponCode)
+        public async Task<DiscountCalculationResult> CalculateDiscountAsync(List<OrderItem> orderItems, string? couponCode)
         {
-            decimal totalDiscount = 0;
+            var result = new DiscountCalculationResult();
+            var now = DateTimeOffset.UtcNow;
+            decimal itemsTotal = orderItems.Sum(i => i.TotalPrice);
 
-            // 1. Hole alle relevanten Rabatte
+            // 1. Lade alle potenziell anwendbaren Rabatte
-            var discounts = await _context.Discounts
+            var query = _context.Discounts
                 .Include(d => d.ProductDiscounts)
                 .Include(d => d.categorieDiscounts)
-                .Where(d => d.IsActive && d.StartDate <= DateTimeOffset.UtcNow && (!d.EndDate.HasValue || d.EndDate >= DateTimeOffset.UtcNow))
+                .Where(d => d.IsActive && d.StartDate <= now &&
-                .ToListAsync();
+                              (!d.EndDate.HasValue || d.EndDate >= now) &&
+                              (!d.MaximumUsageCount.HasValue || d.CurrentUsageCount < d.MaximumUsageCount.Value));
 
-            // Filtern nach Gutscheincode
+            var potentialDiscounts = await query.ToListAsync();
+
+            Discount? bestDiscount = null;
+
+            // 2. Finde den besten anwendbaren Rabatt
             if (!string.IsNullOrEmpty(couponCode))
             {
-                discounts = discounts.Where(d => d.CouponCode == couponCode && d.RequiresCouponCode).ToList();
+                // Wenn ein Code eingegeben wurde, suchen wir nur nach diesem einen Rabatt
+                bestDiscount = potentialDiscounts.FirstOrDefault(d => d.RequiresCouponCode && d.CouponCode == couponCode);
             }
+
+            if (bestDiscount == null)
+            {
+                return result; // Kein passender Rabatt gefunden
+            }
+
+            // 3. Prüfe die Bedingungen des besten Rabatts
+            if (bestDiscount.MinimumOrderAmount.HasValue && itemsTotal < bestDiscount.MinimumOrderAmount.Value)
+            {
+                return result; // Mindestbestellwert nicht erreicht
+            }
+
+            decimal discountAmount = 0;
+
+            // 4. Berechne den Rabattbetrag
+            // Fall A: Rabatt gilt für den gesamten Warenkorb
+            if (!bestDiscount.ProductDiscounts.Any() && !bestDiscount.categorieDiscounts.Any())
+            {
+                discountAmount = CalculateAmount(bestDiscount, itemsTotal);
+            }
+            // Fall B: Rabatt gilt für spezifische Produkte/Kategorien
             else
             {
-                // Rabatte ohne Gutscheincode, falls zutreffend
+                // Lade die Kategorie-Zuweisungen aller Produkte im Warenkorb
-                discounts = discounts.Where(d => !d.RequiresCouponCode).ToList();
+                var productCategoryIds = await _context.Productcategories
-            }
+                    .Where(pc => orderItems.Select(oi => oi.ProductId).Contains(pc.ProductId))
+                    .ToDictionaryAsync(pc => pc.ProductId, pc => pc.categorieId);
 
-            // 2. Wende Rabatte auf Artikel an
+                decimal applicableItemsTotal = 0;
-            foreach (var item in orderItems)
+                foreach (var item in orderItems)
-            {
-                decimal itemDiscount = 0;
-
-                // Wir nehmen an, dass ein Artikel nur den besten Rabatt erhalten kann
-                var applicableDiscount = discounts.FirstOrDefault(d =>
-                    d.ProductDiscounts.Any(pd => pd.ProductId == item.ProductId) || // Rabatt auf Produkt
-                    d.categorieDiscounts.Any(cd => _context.Productcategories.Any(pc => pc.ProductId == item.ProductId && pc.categorieId == cd.categorieId)) // Rabatt auf Kategorie
-                );
-
-                if (applicableDiscount != null)
                 {
-                    itemDiscount = item.UnitPrice * item.Quantity * (applicableDiscount.DiscountValue / 100);
+                    if (!item.ProductId.HasValue)
-                    // Hier müsste die Logik für FixedAmount-Rabatte hin
+                    {
-                }
+                        continue;
+                    }
 
-                totalDiscount += itemDiscount;
+                    Guid productId = item.ProductId.Value;
+
+                    bool isApplicable = bestDiscount.ProductDiscounts.Any(pd => pd.ProductId == productId) ||
+                                      (productCategoryIds.ContainsKey(productId) &&
+                                       bestDiscount.categorieDiscounts.Any(cd => cd.categorieId == productCategoryIds[productId]));
+
+                    if (isApplicable)
+                    {
+                        applicableItemsTotal += item.TotalPrice;
+                    }
+                }
+                discountAmount = CalculateAmount(bestDiscount, applicableItemsTotal);
             }
 
-            // 3. Wende Warenkorb-Rabatte an (falls keine spezifischen Produkte/Kategorien zugewiesen sind)
+            result.TotalDiscountAmount = discountAmount;
-            var cartDiscounts = discounts.Where(d => !d.ProductDiscounts.Any() && !d.categorieDiscounts.Any()).ToList();
+            result.AppliedDiscountIds.Add(bestDiscount.Id);
 
-            decimal cartTotal = orderItems.Sum(i => i.TotalPrice);
+            return result;
-            foreach (var discount in cartDiscounts)
+        }
+
+        // Private Helper-Methode zur Berechnung des Rabattwertes
+        private decimal CalculateAmount(Discount discount, decimal baseAmount)
+        {
+            if (discount.DiscountType == DiscountType.FixedAmount.ToString())
             {
-                if (discount.MinimumOrderAmount.HasValue && cartTotal < discount.MinimumOrderAmount.Value) continue;
+                // Stelle sicher, dass der Rabatt nicht höher als der Betrag ist
-
+                return Math.Min(baseAmount, discount.DiscountValue);
-                // Beispiel: Prozentualer Rabatt auf den Warenkorb
-                if (discount.DiscountType == DiscountType.Percentage.ToString())
-                {
-                    totalDiscount += cartTotal * (discount.DiscountValue / 100);
-                }
             }
-
+            if (discount.DiscountType == DiscountType.Percentage.ToString())
-            return totalDiscount;
+            {
+                return baseAmount * (discount.DiscountValue / 100m);
+            }
+            return 0;
         }
     }
 }

Webshop.Application/Services/Public/Interfaces/IDiscountService.cs

@@ -6,8 +6,24 @@ using Webshop.Domain.Entities;
 
 namespace Webshop.Application.Services.Public.Interfaces
 {
+    /// <summary>
+    /// Stellt das Ergebnis der Rabattberechnung dar.
+    /// </summary>
+    public class DiscountCalculationResult
+    {
+        /// <summary>
+        /// Der gesamte berechnete Rabattbetrag.
+        /// </summary>
+        public decimal TotalDiscountAmount { get; set; } = 0;
+
+        /// <summary>
+        /// Die IDs der Rabatte, die erfolgreich angewendet wurden.
+        /// </summary>
+        public List<Guid> AppliedDiscountIds { get; set; } = new List<Guid>();
+    }
+
     public interface IDiscountService
     {
-        Task<decimal> CalculateDiscountAsync(List<OrderItem> orderItems, string? couponCode);
+        Task<DiscountCalculationResult> CalculateDiscountAsync(List<OrderItem> orderItems, string? couponCode);
     }
 }