feat: 添加购买分组功能，替代跨分类购物选项

backend/internal/api/handlers/purchase_group.go

@@ -0,0 +1,105 @@
+package handlers
+
+import (
+	"net/http"
+	"strconv"
+
+	"sale/internal/models"
+	"sale/internal/schemas"
+	"sale/internal/utils"
+
+	"github.com/gin-gonic/gin"
+)
+
+type PurchaseGroupHandler struct{}
+
+func NewPurchaseGroupHandler() *PurchaseGroupHandler {
+	return &PurchaseGroupHandler{}
+}
+
+func (h *PurchaseGroupHandler) List(c *gin.Context) {
+	var groups []models.PurchaseGroup
+	utils.DB.Order("sort_order ASC, id ASC").Preload("Categories").Find(&groups)
+	c.JSON(http.StatusOK, gin.H{"data": groups})
+}
+
+func (h *PurchaseGroupHandler) Create(c *gin.Context) {
+	var req schemas.CreatePurchaseGroupRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	var existing models.PurchaseGroup
+	if err := utils.DB.Where("name = ?", req.Name).First(&existing).Error; err == nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "分组名称已存在"})
+		return
+	}
+
+	group := models.PurchaseGroup{
+		Name:        req.Name,
+		Description: req.Description,
+		SortOrder:   req.SortOrder,
+	}
+
+	if err := utils.DB.Create(&group).Error; err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create purchase group"})
+		return
+	}
+
+	c.JSON(http.StatusCreated, gin.H{"data": group})
+}
+
+func (h *PurchaseGroupHandler) Update(c *gin.Context) {
+	id, _ := strconv.Atoi(c.Param("id"))
+	var group models.PurchaseGroup
+	if err := utils.DB.First(&group, id).Error; err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Purchase group not found"})
+		return
+	}
+
+	var req schemas.UpdatePurchaseGroupRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	if req.Name != nil && *req.Name != group.Name {
+		var existing models.PurchaseGroup
+		if err := utils.DB.Where("name = ? AND id != ?", *req.Name, id).First(&existing).Error; err == nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "分组名称已存在"})
+			return
+		}
+	}
+
+	updates := make(map[string]interface{})
+	if req.Name != nil {
+		updates["name"] = *req.Name
+	}
+	if req.Description != nil {
+		updates["description"] = *req.Description
+	}
+	if req.SortOrder != nil {
+		updates["sort_order"] = *req.SortOrder
+	}
+
+	utils.DB.Model(&group).Updates(updates)
+	c.JSON(http.StatusOK, gin.H{"data": group})
+}
+
+func (h *PurchaseGroupHandler) Delete(c *gin.Context) {
+	id, _ := strconv.Atoi(c.Param("id"))
+
+	var categoryCount int64
+	utils.DB.Model(&models.Category{}).Where("purchase_group_id = ?", id).Count(&categoryCount)
+	if categoryCount > 0 {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "该分组下有分类，无法删除"})
+		return
+	}
+
+	if err := utils.DB.Delete(&models.PurchaseGroup{}, id).Error; err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to delete purchase group"})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"message": "Purchase group deleted successfully"})
+}