小程序导出账单接口

app/Services/BillDetailService.php

@@ -5,6 +5,7 @@ namespace App\Services;
 use App\Models\BillModel;
 use App\Models\ProductModel;
 use App\Models\StoreOrderItemModel;
+use Illuminate\Support\Collection;
 
 /**
  * 账单详情数据组装（后台门店账单页与小程序账单详情共用）
@@ -24,6 +25,35 @@ class BillDetailService
             ->orderBy('id')
             ->get();
 
+        return $this->aggregateItems($items);
+    }
+
+    /**
+     * 合并后的商品明细（跨账单口径）：按商品聚合多张账单的全部订单明细
+     * 用于账单合并导出，单价同为加权平均口径
+     *
+     * @param array<int, int> $billIds 账单ID列表
+     * @return array<int, array{product_id: int, product_name: string, product_spec: string, unit: string, price: string, quantity: int, weight: string, amount: string}>
+     */
+    public function mergedItemsOfBills(array $billIds): array
+    {
+        $items = StoreOrderItemModel::query()
+            ->whereIn('bill_id', $billIds)
+            ->orderBy('id')
+            ->get();
+
+        return $this->aggregateItems($items);
+    }
+
+    /**
+     * 按商品聚合订单明细：数量累加、重量/金额 bc 累加、单价加权平均，
+     * 按「分类sort → 商品sort」排序
+     *
+     * @param Collection<int, StoreOrderItemModel> $items
+     * @return array<int, array{product_id: int, product_name: string, product_spec: string, unit: string, price: string, quantity: int, weight: string, amount: string}>
+     */
+    private function aggregateItems(Collection $items): array
+    {
         // 排序键：分类 sort → 商品 sort（与采购单明细矩阵同序）
         $products = ProductModel::withTrashed()
             ->with('category:id,sort')