feat: 完善库存锁定幂等与批次扣减策略

src/Application/TakeoutSaaS.Application/App/Inventory/Handlers/AdjustInventoryCommandHandler.cs

@@ -0,0 +1,85 @@
+using MediatR;
+using Microsoft.Extensions.Logging;
+using TakeoutSaaS.Application.App.Inventory.Commands;
+using TakeoutSaaS.Application.App.Inventory.Dto;
+using TakeoutSaaS.Domain.Inventory.Entities;
+using TakeoutSaaS.Domain.Inventory.Repositories;
+using TakeoutSaaS.Shared.Abstractions.Constants;
+using TakeoutSaaS.Shared.Abstractions.Exceptions;
+using TakeoutSaaS.Shared.Abstractions.Tenancy;
+
+namespace TakeoutSaaS.Application.App.Inventory.Handlers;
+
+/// <summary>
+/// 库存调整处理器。
+/// </summary>
+public sealed class AdjustInventoryCommandHandler(
+    IInventoryRepository inventoryRepository,
+    ITenantProvider tenantProvider,
+    ILogger<AdjustInventoryCommandHandler> logger)
+    : IRequestHandler<AdjustInventoryCommand, InventoryItemDto>
+{
+    /// <inheritdoc />
+    public async Task<InventoryItemDto> Handle(AdjustInventoryCommand request, CancellationToken cancellationToken)
+    {
+        // 1. 读取库存
+        var tenantId = tenantProvider.GetCurrentTenantId();
+        var item = await inventoryRepository.GetForUpdateAsync(tenantId, request.StoreId, request.ProductSkuId, cancellationToken);
+        // 2. 初始化或校验存在性
+        if (item is null)
+        {
+            if (request.QuantityDelta < 0)
+            {
+                throw new BusinessException(ErrorCodes.NotFound, "库存不存在，无法扣减");
+            }
+
+            // 初始化库存记录
+            item = new InventoryItem
+            {
+                TenantId = tenantId,
+                StoreId = request.StoreId,
+                ProductSkuId = request.ProductSkuId,
+                QuantityOnHand = request.QuantityDelta,
+                QuantityReserved = 0,
+                SafetyStock = request.SafetyStock,
+                IsSoldOut = false
+            };
+            await inventoryRepository.AddItemAsync(item, cancellationToken);
+        }
+
+        // 3. 应用调整
+        var newQuantity = item.QuantityOnHand + request.QuantityDelta;
+        if (newQuantity < 0)
+        {
+            throw new BusinessException(ErrorCodes.Conflict, "库存不足，无法扣减");
+        }
+
+        item.QuantityOnHand = newQuantity;
+        item.SafetyStock = request.SafetyStock ?? item.SafetyStock;
+        item.IsSoldOut = request.IsSoldOut ?? IsSoldOut(item);
+
+        // 4. 写入调整记录
+        var adjustment = new InventoryAdjustment
+        {
+            TenantId = tenantId,
+            InventoryItemId = item.Id,
+            AdjustmentType = request.AdjustmentType,
+            Quantity = request.QuantityDelta,
+            Reason = request.Reason,
+            OperatorId = null,
+            OccurredAt = DateTime.UtcNow
+        };
+        await inventoryRepository.AddAdjustmentAsync(adjustment, cancellationToken);
+        await inventoryRepository.SaveChangesAsync(cancellationToken);
+        logger.LogInformation("调整库存 SKU {ProductSkuId} 门店 {StoreId} 变更 {Delta}", request.ProductSkuId, request.StoreId, request.QuantityDelta);
+        return InventoryMapping.ToDto(item);
+    }
+
+    // 辅助：售罄判定
+    private static bool IsSoldOut(InventoryItem item)
+    {
+        var available = item.QuantityOnHand - item.QuantityReserved - item.PresaleLocked;
+        var safety = item.SafetyStock ?? 0;
+        return available <= safety || item.QuantityOnHand <= 0;
+    }
+}