feat: 添加用户购买作品数量统计功能

backend_v1/app/http/admin/users.go

@@ -7,22 +7,53 @@ import (
 	"quyun/v2/database/models"
 
 	"github.com/gofiber/fiber/v3"
+	"github.com/samber/lo"
 )
 
 // @provider
 type users struct{}
 
+type UserItem struct {
+	*models.User
+	BoughtCount int64 `json:"bought_count"` // 用户已购作品数量（统计 user_posts 记录数，含赠送/免费购买）
+}
+
 // List users
 //
 //	@Summary	用户列表
 //	@Tags		Admin Users
 //	@Produce	json
 //	@Param		query		query		UserListQuery						false	"筛选条件"
-//	@Success	200			{object}	requests.Pager{items=models.User}	"成功"
+//	@Success	200			{object}	requests.Pager{items=UserItem}	"成功"
 //	@Router		/admin/v1/users [get]
 //	@Bind		query query
 func (ctl *users) List(ctx fiber.Ctx, query *dto.UserListQuery) (*requests.Pager, error) {
-	return services.Users.List(ctx, query)
+	pager, err := services.Users.List(ctx, query)
+	if err != nil {
+		return nil, err
+	}
+
+	userIDs := lo.Map(pager.Items.([]*models.User), func(item *models.User, _ int) int64 {
+		return item.ID
+	})
+	if len(userIDs) == 0 {
+		return pager, nil
+	}
+
+	cntMap, err := services.Users.BoughtStatistics(ctx, userIDs)
+	if err != nil {
+		return pager, err
+	}
+
+	items := lo.Map(pager.Items.([]*models.User), func(item *models.User, _ int) UserItem {
+		cnt := int64(0)
+		if v, ok := cntMap[item.ID]; ok {
+			cnt = v
+		}
+		return UserItem{User: item, BoughtCount: cnt}
+	})
+	pager.Items = items
+	return pager, nil
 }
 
 // Show user

backend_v1/app/services/users.go

@@ -72,6 +72,37 @@ func (m *users) List(
 	}, nil
 }
 
+// BoughtStatistics 获取指定用户 ID 的购买作品数量（仅统计 user_posts 记录数）。
+func (m *users) BoughtStatistics(ctx context.Context, userIDs []int64) (map[int64]int64, error) {
+	if len(userIDs) == 0 {
+		return map[int64]int64{}, nil
+	}
+
+	// 管理端用户列表需要展示购买数量；这里用 group by 聚合，避免 N+1。
+	tbl, query := models.UserPostQuery.QueryContext(ctx)
+
+	var items []struct {
+		Count  int64
+		UserID int64
+	}
+	if err := query.
+		Select(
+			tbl.UserID.Count().As("count"),
+			tbl.UserID,
+		).
+		Where(tbl.UserID.In(userIDs...)).
+		Group(tbl.UserID).
+		Scan(&items); err != nil {
+		return nil, err
+	}
+
+	result := make(map[int64]int64, len(items))
+	for _, item := range items {
+		result[item.UserID] = item.Count
+	}
+	return result, nil
+}
+
 // PostList returns a paginated list of posts for a user
 func (m *users) PostList(ctx context.Context, userId int64, filter *dto.PostListQuery) (*requests.Pager, error) {
 	filter.Format()