完成门店管理后端接口与任务

src/Application/TakeoutSaaS.Application/App/Stores/Handlers/GetStoreFeeQueryHandler.cs

@@ -0,0 +1,49 @@
+using MediatR;
+using TakeoutSaaS.Application.App.Stores.Dto;
+using TakeoutSaaS.Application.App.Stores.Queries;
+using TakeoutSaaS.Domain.Stores.Entities;
+using TakeoutSaaS.Domain.Stores.Repositories;
+using TakeoutSaaS.Shared.Abstractions.Constants;
+using TakeoutSaaS.Shared.Abstractions.Exceptions;
+using TakeoutSaaS.Shared.Abstractions.Tenancy;
+
+namespace TakeoutSaaS.Application.App.Stores.Handlers;
+
+/// <summary>
+/// 获取门店费用配置处理器。
+/// </summary>
+public sealed class GetStoreFeeQueryHandler(
+    IStoreRepository storeRepository,
+    ITenantProvider tenantProvider)
+    : IRequestHandler<GetStoreFeeQuery, StoreFeeDto?>
+{
+    /// <inheritdoc />
+    public async Task<StoreFeeDto?> Handle(GetStoreFeeQuery request, CancellationToken cancellationToken)
+    {
+        // 1. 校验门店存在
+        var tenantId = tenantProvider.GetCurrentTenantId();
+        var store = await storeRepository.FindByIdAsync(request.StoreId, tenantId, cancellationToken);
+        if (store is null)
+        {
+            throw new BusinessException(ErrorCodes.NotFound, "门店不存在");
+        }
+
+        // 2. (空行后) 查询费用配置
+        var fee = await storeRepository.GetStoreFeeAsync(request.StoreId, tenantId, cancellationToken);
+        if (fee is null)
+        {
+            var fallback = new StoreFee
+            {
+                StoreId = request.StoreId,
+                MinimumOrderAmount = 0m,
+                BaseDeliveryFee = 0m,
+                PackagingFeeMode = Domain.Stores.Enums.PackagingFeeMode.Fixed,
+                FixedPackagingFee = 0m
+            };
+            return StoreMapping.ToDto(fallback);
+        }
+
+        // 3. (空行后) 返回结果
+        return StoreMapping.ToDto(fee);
+    }
+}