mce/internal/service/favorite_items.go

package service

import (
	"fmt"

	"metazone.cc/metalab/internal/common"
	"metazone.cc/metalab/internal/model"

	"gorm.io/gorm"
)

// AddToFolder 将文章加入收藏夹（会先移除该文章在其他收藏夹的收藏）
func (s *FavoriteService) AddToFolder(userID, folderID, postID uint) error {
	// 检查收藏夹归属
	f, err := s.repo.FindFolderByID(folderID)
	if err != nil {
		return common.ErrPostNotFound
	}
	if f.UserID != userID {
		return common.ErrPermissionDenied
	}

	return s.db.Transaction(func(tx *gorm.DB) error {
		txRepo := s.repo.WithTx(tx)

		// 如果该文章已在其他收藏夹中，先移除
		existing, err := txRepo.FindItemByUserAndPost(userID, postID)
		if err == nil && existing.FolderID != folderID {
			if err := txRepo.DeleteItem(existing.FolderID, postID); err != nil {
				return fmt.Errorf("移除旧收藏: %w", err)
			}
			// 旧收藏夹没有增加计数，所以不需要减
		}

		// 检查是否已在目标收藏夹中
		if err == nil && existing.FolderID == folderID {
			return fmt.Errorf("文章已在此收藏夹中")
		}

		item := &model.FolderItem{
			FolderID: folderID,
			PostID:   postID,
			UserID:   userID,
		}
		if err := txRepo.CreateItem(item); err != nil {
			return fmt.Errorf("添加收藏: %w", err)
		}

		return txRepo.IncrPostFavoritesCount(postID, 1)
	})
}

// RemoveFromFolder 从收藏夹移除文章
func (s *FavoriteService) RemoveFromFolder(userID, folderID, postID uint) error {
	f, err := s.repo.FindFolderByID(folderID)
	if err != nil {
		return common.ErrPostNotFound
	}
	if f.UserID != userID {
		return common.ErrPermissionDenied
	}

	return s.db.Transaction(func(tx *gorm.DB) error {
		txRepo := s.repo.WithTx(tx)
		if err := txRepo.DeleteItem(folderID, postID); err != nil {
			return fmt.Errorf("移除收藏: %w", err)
		}
		return txRepo.IncrPostFavoritesCount(postID, -1)
	})
}

// AddFavorite 收藏文章（自动选择或创建默认收藏夹）
func (s *FavoriteService) AddFavorite(userID, postID uint, folderID *uint) error {
	var targetFolderID uint

	if folderID != nil && *folderID > 0 {
		targetFolderID = *folderID
	} else {
		// 使用或创建默认收藏夹
		f, err := s.ensureDefaultFolder(userID)
		if err != nil {
			return err
		}
		targetFolderID = f.ID
	}

	return s.AddToFolder(userID, targetFolderID, postID)
}

// RemoveFavorite 取消收藏文章
func (s *FavoriteService) RemoveFavorite(userID, postID uint) error {
	existing, err := s.repo.FindItemByUserAndPost(userID, postID)
	if err != nil {
		return fmt.Errorf("未收藏该文章")
	}
	return s.RemoveFromFolder(userID, existing.FolderID, postID)
}

// ListFolderItems 列收藏夹内的文章
func (s *FavoriteService) ListFolderItems(userID, folderID uint, page, pageSize int) (*FolderItemsResult, error) {
	f, err := s.repo.FindFolderByID(folderID)
	if err != nil {
		return nil, common.ErrPostNotFound
	}

	// 权限检查：非本人 + 非公开 → 拒绝
	if f.UserID != userID && !f.IsPublic {
		return nil, common.ErrPermissionDenied
	}

	p := common.Pagination{Page: page, PageSize: pageSize}
	p.DefaultPagination()

	items, total, err := s.repo.ListItemsByFolder(folderID, p.Offset(), p.PageSize)
	if err != nil {
		return nil, fmt.Errorf("查询收藏内容: %w", err)
	}
	if items == nil {
		items = []model.FolderItem{}
	}

	return &FolderItemsResult{
		Items:      items,
		Total:      total,
		Page:       p.Page,
		TotalPages: common.PageCount(total, p.PageSize),
	}, nil
}

// ToggleFavorite 切换收藏（有则取消，无则加入默认收藏夹）
func (s *FavoriteService) ToggleFavorite(userID, postID uint) (bool, error) {
	existing, err := s.repo.FindItemByUserAndPost(userID, postID)
	if err == nil {
		// 已收藏，取消
		if err := s.RemoveFromFolder(userID, existing.FolderID, postID); err != nil {
			return false, err
		}
		return false, nil
	}

	// 未收藏，加入默认
	if err := s.AddFavorite(userID, postID, nil); err != nil {
		return false, err
	}
	return true, nil
}