package service

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"strings"
	"time"

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

// ShareService 分享业务服务
type ShareService struct {
	shareRepo *repository.ShareRepository
	fileRepo  *repository.FileRepository
}

// NewShareService 创建分享服务实例
func NewShareService() *ShareService {
	return &ShareService{
		shareRepo: repository.NewShareRepository(),
		fileRepo:  repository.NewFileRepository(),
	}
}

// Create 创建分享链接
func (s *ShareService) Create(req *dto.ShareCreateRequest, ownerID uint64) (*dto.ShareVO, error) {
	// 验证文件存在
	file, err := s.fileRepo.FindByID(req.FileID)
	if err != nil {
		return nil, errors.New("文件不存在")
	}
	if file.OwnerID != ownerID {
		return nil, errors.New("无权分享此文件")
	}

	// 生成分享码
	shareCode, err := generateShareCode()
	if err != nil {
		return nil, errors.New("生成分享码失败")
	}

	share := &model.Share{
		FileID:        req.FileID,
		OwnerID:       ownerID,
		ShareCode:     shareCode,
		AllowPreview:  1,
		AllowDownload: 1,
		Status:        1,
	}

	// 设置密码
	if req.Password != "" {
		hashed, _ := utils.HashPassword(req.Password)
		share.Password = hashed
	}

	// 设置过期时间
	if req.ExpireHours > 0 {
		expireAt := time.Now().Add(time.Duration(req.ExpireHours) * time.Hour)
		share.ExpireAt = &expireAt
	}

	share.MaxDownload = req.MaxDownload

	// 设置权限
	share.AllowPreview = int8(req.AllowPreview)
	share.AllowDownload = int8(req.AllowDownload)
	// 如果都是0(未传), 默认允许
	if share.AllowPreview == 0 && share.AllowDownload == 0 {
		share.AllowPreview = 1
		share.AllowDownload = 1
	}

	if err := s.shareRepo.Create(share); err != nil {
		return nil, errors.New("创建分享失败")
	}

	return s.toShareVO(share), nil
}

// GetByCode 通过分享码获取分享信息(公开访问)
func (s *ShareService) GetByCode(code string) (*dto.ShareFileVO, *model.Share, error) {
	share, err := s.shareRepo.FindByShareCode(code)
	if err != nil {
		return nil, nil, errors.New("分享链接不存在或已失效")
	}

	// 检查过期
	if share.ExpireAt != nil && share.ExpireAt.Before(time.Now()) {
		return nil, nil, errors.New("分享链接已过期")
	}

	// 检查下载次数
	if share.MaxDownload > 0 && share.DownloadCount >= share.MaxDownload {
		return nil, nil, errors.New("下载次数已达上限")
	}

	// 获取文件信息
	file, err := s.fileRepo.FindByID(share.FileID)
	if err != nil {
		return nil, nil, errors.New("文件不存在")
	}

	// 生成预览URL
	previewURL := ""
	if share.AllowPreview == 1 && file.StorageKey != "" {
		engine, err := storage.GetEngineByPolicyID(file.StoragePolicyID)
		if err == nil {
			if localEngine, ok := engine.(*storage.LocalEngine); ok {
				previewURL = localEngine.GetURL(file.StorageKey)
			} else if minioEngine, ok := engine.(*storage.MinIOEngine); ok {
				previewURL = minioEngine.GetPreviewURL(file.StorageKey)
			}
		}
	}

	fileVO := &dto.ShareFileVO{
		Name:          file.Name,
		Extension:     file.Extension,
		Size:          file.Size,
		MimeType:      file.MimeType,
		PreviewURL:    previewURL,
		AllowPreview:  share.AllowPreview == 1,
		AllowDownload: share.AllowDownload == 1,
		CreatedAt:     file.CreatedAt,
	}

	return fileVO, share, nil
}

// VerifyPassword 验证分享密码
func (s *ShareService) VerifyPassword(shareID uint64, password string) bool {
	share, err := s.shareRepo.FindByID(shareID)
	if err != nil {
		return false
	}
	return utils.CheckPassword(password, share.Password)
}

// ListByOwner 查询用户的分享列表
func (s *ShareService) ListByOwner(ownerID uint64) ([]dto.ShareVO, error) {
	shares, err := s.shareRepo.ListByOwner(ownerID)
	if err != nil {
		return nil, err
	}

	vos := make([]dto.ShareVO, 0, len(shares))
	for i := range shares {
		vos = append(vos, *s.toShareVO(&shares[i]))
	}
	return vos, nil
}

// Cancel 取消分享
func (s *ShareService) Cancel(id uint64, ownerID uint64) error {
	share, err := s.shareRepo.FindByID(id)
	if err != nil {
		return errors.New("分享不存在")
	}
	if share.OwnerID != ownerID {
		return errors.New("无权操作此分享")
	}
	return s.shareRepo.Cancel(id)
}

// toShareVO 转换为视图对象
func (s *ShareService) toShareVO(share *model.Share) *dto.ShareVO {
	// 生成完整分享链接
	publicURL := config.AppConfig.Server.PublicURL
	if publicURL == "" {
		publicURL = "http://localhost:8080"
	}
	publicURL = strings.TrimRight(publicURL, "/")

	return &dto.ShareVO{
		ID:            share.ID,
		ShareCode:     share.ShareCode,
		ShareURL:      publicURL + "/s/" + share.ShareCode,
		HasPassword:   share.Password != "",
		ExpireAt:      share.ExpireAt,
		MaxDownload:   share.MaxDownload,
		DownloadCount: share.DownloadCount,
		AllowPreview:  share.AllowPreview,
		AllowDownload: share.AllowDownload,
		CreatedAt:     share.CreatedAt,
	}
}

// generateShareCode 生成8字节随机分享码(16位十六进制字符串)
func generateShareCode() (string, error) {
	bytes := make([]byte, 8)
	if _, err := rand.Read(bytes); err != nil {
		return "", err
	}
	return hex.EncodeToString(bytes), nil
}