package service

import (
	"errors"
	"fmt"

	"seeyon-filesystem/config"
	"seeyon-filesystem/dto"
	"seeyon-filesystem/model"
	"seeyon-filesystem/repository"
	"seeyon-filesystem/utils"
)

// FolderService 文件夹业务服务
type FolderService struct {
	folderRepo *repository.FolderRepository
	fileRepo   *repository.FileRepository
}

// NewFolderService 创建文件夹服务实例
func NewFolderService() *FolderService {
	return &FolderService{
		folderRepo: repository.NewFolderRepository(),
		fileRepo:   repository.NewFileRepository(),
	}
}

// Create 创建文件夹
func (s *FolderService) Create(req *dto.CreateFolderRequest, ownerID uint64) (*dto.FolderVO, error) {
	parentID := uint64(req.ParentID)

	// 构建物化路径
	parentPath := "/"
	if parentID > 0 {
		parent, err := s.folderRepo.FindByID(parentID)
		if err != nil {
			return nil, errors.New("父文件夹不存在")
		}
		if !s.canAccessFolder(parent.OwnerID, ownerID) {
			return nil, errors.New("无权访问父文件夹")
		}
		parentPath = parent.Path
	}

	// 检查同名文件夹
	existing, _ := s.folderRepo.FindByNameAndParent(req.Name, parentID, ownerID)
	if existing != nil {
		return nil, errors.New("同名文件夹已存在")
	}

	folderID := utils.GenID()
	folder := &model.Folder{
		ID:       folderID,
		BizID:    req.BizID,
		Name:     req.Name,
		ParentID: parentID,
		OwnerID:  ownerID,
		Path:     fmt.Sprintf("%s%d/", parentPath, folderID),
		Status:   1,
	}

	if err := s.folderRepo.Create(folder); err != nil {
		return nil, fmt.Errorf("创建文件夹失败: %w", err)
	}

	return s.toFolderVO(folder), nil
}

// GetByID 根据ID获取文件夹
func (s *FolderService) GetByID(id uint64, ownerID uint64) (*dto.FolderVO, error) {
	folder, err := s.folderRepo.FindByID(id)
	if err != nil {
		return nil, errors.New("文件夹不存在")
	}
	if !s.canAccessFolder(folder.OwnerID, ownerID) {
		return nil, errors.New("无权访问此文件夹")
	}
	return s.toFolderVO(folder), nil
}

// GetByBizID 根据业务ID获取文件夹
func (s *FolderService) GetByBizID(bizID string, ownerID uint64) (*dto.FolderVO, error) {
	folder, err := s.folderRepo.FindByBizID(bizID, ownerID)
	if err != nil {
		return nil, errors.New("文件夹不存在")
	}
	return s.toFolderVO(folder), nil
}

// ListChildren 获取文件夹的子项(文件+文件夹, 基于权限, 支持分页)
// 管理员看全部, 非管理员只看自己创建的 + 被授权的
func (s *FolderService) ListChildren(folderID uint64, userID uint64, page, pageSize int) (*dto.FileListVO, error) {
	roleIDs := s.getUserRoleIDs(userID)
	isAdmin := s.isAdmin(roleIDs)

	// 如果指定了文件夹ID, 验证访问权限
	if folderID > 0 {
		folder, err := s.folderRepo.FindByID(folderID)
		if err != nil {
			return nil, errors.New("文件夹不存在")
		}
		if !isAdmin && folder.OwnerID != userID {
			return nil, errors.New("无权访问此文件夹")
		}
	}

	// 查询子文件夹
	var folders []model.Folder
	var totalFolders int64
	if isAdmin {
		folders, _ = s.folderRepo.ListByParentAll(folderID)
		totalFolders, _ = s.folderRepo.CountByParentAll(folderID)
	} else {
		folders, _ = s.folderRepo.ListByParent(folderID, userID)
		totalFolders, _ = s.folderRepo.CountByParent(folderID, userID)
	}

	// 分页查询子文件
	var files []model.File
	var totalFiles int64
	var err error
	if pageSize > 0 {
		files, totalFiles, err = s.fileRepo.ListByFolderPaginated(folderID, userID, roleIDs, page, pageSize)
	} else {
		files, err = s.fileRepo.ListByFolder(folderID, userID, roleIDs)
		totalFiles = int64(len(files))
	}
	if err != nil {
		return nil, err
	}

	// 组装响应
	folderVOs := make([]dto.FolderVO, 0, len(folders))
	for _, f := range folders {
		folderVOs = append(folderVOs, *s.toFolderVO(&f))
	}

	fileVOs := make([]dto.FileVO, 0, len(files))
	for _, f := range files {
		fileVOs = append(fileVOs, *s.toFileVO(&f))
	}

	return &dto.FileListVO{
		Folders:      folderVOs,
		Files:        fileVOs,
		TotalFiles:   totalFiles,
		TotalFolders: totalFolders,
		Page:         page,
		PageSize:     pageSize,
	}, nil
}

// canAccessFolder 检查用户是否有权操作该文件夹(owner / admin)
func (s *FolderService) canAccessFolder(folderOwnerID, userID uint64) bool {
	if folderOwnerID == userID {
		return true
	}
	return s.isAdmin(s.getUserRoleIDs(userID))
}

// isAdmin 检查用户是否为管理员
func (s *FolderService) isAdmin(roleIDs []uint64) bool {
	if len(roleIDs) == 0 {
		return false
	}
	var count int64
	config.DB.Model(&model.Role{}).Where("id IN ? AND name = ?", roleIDs, "admin").Count(&count)
	return count > 0
}

// Rename 重命名文件夹(乐观锁)
func (s *FolderService) Rename(id uint64, newName string, ownerID uint64, version int) error {
	folder, err := s.folderRepo.FindByID(id)
	if err != nil {
		return errors.New("文件夹不存在")
	}
	if !s.canAccessFolder(folder.OwnerID, ownerID) {
		return errors.New("无权操作此文件夹")
	}

	// 乐观锁检查
	if version > 0 && folder.Version != version {
		return fmt.Errorf("文件夹已被其他人修改, 当前版本: %d, 请刷新后重试", folder.Version)
	}

	newVersion := folder.Version + 1
	result := config.DB.Model(&model.Folder{}).
		Where("id = ? AND version = ?", id, folder.Version).
		Updates(map[string]interface{}{
			"name":    newName,
			"version": newVersion,
		})

	if result.RowsAffected == 0 {
		return fmt.Errorf("文件夹已被其他人修改, 请刷新后重试")
	}
	return result.Error
}

// Delete 删除文件夹(移入回收站)
func (s *FolderService) Delete(id uint64, ownerID uint64) error {
	folder, err := s.folderRepo.FindByID(id)
	if err != nil {
		return errors.New("文件夹不存在")
	}
	if !s.canAccessFolder(folder.OwnerID, ownerID) {
		return errors.New("无权操作此文件夹")
	}

	return s.folderRepo.SoftDelete(id)
}

// toFolderVO 转换为视图对象
func (s *FolderService) toFolderVO(folder *model.Folder) *dto.FolderVO {
	return &dto.FolderVO{
		ID:        dto.StringID(folder.ID),
		BizID:     folder.BizID,
		Name:      folder.Name,
		ParentID:  dto.StringID(folder.ParentID),
		OwnerID:   dto.StringID(folder.OwnerID),
		OwnerName: s.getUserName(folder.OwnerID),
		Path:      folder.Path,
		Version:   folder.Version,
		CreatedAt: folder.CreatedAt,
		UpdatedAt: folder.UpdatedAt,
	}
}

// getUserName 根据用户ID获取显示名称
func (s *FolderService) getUserName(userID uint64) string {
	var user model.User
	if config.DB.Select("nickname", "username").First(&user, userID).Error != nil {
		return ""
	}
	if user.Nickname != "" {
		return user.Nickname
	}
	return user.Username
}

// getUserRoleIDs 获取用户的角色ID列表
func (s *FolderService) getUserRoleIDs(userID uint64) []uint64 {
	var userRoles []model.UserRole
	config.DB.Where("user_id = ?", userID).Find(&userRoles)
	roleIDs := make([]uint64, 0, len(userRoles))
	for _, ur := range userRoles {
		roleIDs = append(roleIDs, ur.RoleID)
	}
	return roleIDs
}

// toFileVO 转换为视图对象
func (s *FolderService) toFileVO(file *model.File) *dto.FileVO {
	vo := &dto.FileVO{
		ID:              dto.StringID(file.ID),
		Name:            file.Name,
		Extension:       file.Extension,
		FolderID:        dto.StringID(file.FolderID),
		OwnerID:         dto.StringID(file.OwnerID),
		OwnerName:       s.getUserName(file.OwnerID),
		Size:            file.Size,
		StorageKey:      file.StorageKey,
		StoragePolicyID: file.StoragePolicyID,
		MimeType:        file.MimeType,
		IsFavorite:      file.IsFavorite,
		DownloadCount:   file.DownloadCount,
		Version:         file.Version,
		CreatedAt:       file.CreatedAt,
		UpdatedAt:       file.UpdatedAt,
	}

	// 生成下载/预览链接
	if file.StorageKey != "" {
		downloadURL, _ := GenerateFileURL(file, "download")
		previewURL, _ := GenerateFileURL(file, "preview")
		vo.DownloadURL = downloadURL
		vo.PreviewURL = previewURL
	}

	return vo
}