feat: 完成营销中心优惠券后端模块

src/Application/TakeoutSaaS.Application/App/Coupons/Handlers/GetCouponTemplateDetailQueryHandler.cs

@@ -0,0 +1,38 @@
+using MediatR;
+using TakeoutSaaS.Application.App.Coupons.Dto;
+using TakeoutSaaS.Application.App.Coupons.Queries;
+using TakeoutSaaS.Domain.Coupons.Repositories;
+using TakeoutSaaS.Shared.Abstractions.Constants;
+using TakeoutSaaS.Shared.Abstractions.Exceptions;
+using TakeoutSaaS.Shared.Abstractions.Tenancy;
+
+namespace TakeoutSaaS.Application.App.Coupons.Handlers;
+
+/// <summary>
+/// 优惠券模板详情查询处理器。
+/// </summary>
+public sealed class GetCouponTemplateDetailQueryHandler(
+    ICouponRepository couponRepository,
+    ITenantProvider tenantProvider)
+    : IRequestHandler<GetCouponTemplateDetailQuery, CouponTemplateDetailDto?>
+{
+    /// <inheritdoc />
+    public async Task<CouponTemplateDetailDto?> Handle(GetCouponTemplateDetailQuery request, CancellationToken cancellationToken)
+    {
+        var tenantId = tenantProvider.GetCurrentTenantId();
+        var template = await couponRepository.FindTemplateByIdAsync(request.TemplateId, tenantId, cancellationToken);
+        if (template is null)
+        {
+            return null;
+        }
+
+        var scope = CouponTemplateMapping.DeserializeStoreScope(template.StoreScopeJson, template.Id);
+        if (!scope.StoreIds.Contains(request.StoreId) && !string.Equals(scope.Mode, "all", StringComparison.Ordinal))
+        {
+            throw new BusinessException(ErrorCodes.NotFound, "优惠券不存在");
+        }
+
+        var channels = CouponTemplateMapping.DeserializeChannels(template.ChannelsJson, template.Id);
+        return CouponTemplateDtoFactory.ToDetailDto(template, scope, channels);
+    }
+}