creating purchaseproduct's endpoint and fix error in dto

PyroFetes/Endpoints/PurchaseProduct/PatchPurchaseProductQuantityEndpoint.cs

@@ -1,6 +1,36 @@
+using FastEndpoints;
+using Microsoft.EntityFrameworkCore;
+using PyroFetes.DTO.PurchaseProduct.Request;
+using PyroFetes.DTO.PurchaseProduct.Response;
+
 namespace PyroFetes.Endpoints.PurchaseProduct;
 
-public class PatchPurchaseProductQuantityEndpoint
+public class PatchPurchaseProductQuantityEndpoint(PyroFetesDbContext database) : Endpoint<PatchPurchaseProductQuantityDto, GetPurchaseProductDto>
 {
-    
+    public override void Configure()
+    {
+        Patch("/api/purchaseOrders/{ProductId}/{PurchaseOrderId}/Quantity", x => new { x.ProductId, x.PurchaseOrderId });
+        AllowAnonymous();
+    }
+
+    public override async Task HandleAsync(PatchPurchaseProductQuantityDto req, CancellationToken ct)
+    {
+        var purchaseProduct = await database.PurchaseProducts.SingleOrDefaultAsync(po => po.ProductId == req.ProductId && po.PurchaseOrderId == req.PurchaseOrderId, ct);
+        if (purchaseProduct == null)
+        {
+            await Send.NotFoundAsync(ct);
+            return;
+        }
+        
+        purchaseProduct.Quantity = req.Quantity;
+        await database.SaveChangesAsync(ct);
+
+        GetPurchaseProductDto responseDto = new()
+        {
+            ProductId = purchaseProduct.ProductId,
+            PurchaseOrderId = purchaseProduct.PurchaseOrderId,
+            Quantity = purchaseProduct.Quantity
+        };
+        await Send.OkAsync(responseDto, ct);
+    }
 }