package service

import (
	"errors"

	"fmt"

	"io"

	"mime/multipart"

	"os"

	"path/filepath"

	"sort"

	"strings"

	"time"

	"licserver/internal/model"

	"licserver/internal/utils"

	"github.com/google/uuid"

	"gorm.io/gorm"

	"crypto/sha256"

	"encoding/hex"
)

type UploadService struct {
	db *gorm.DB

	config *utils.Config
}

func NewUploadService(db *gorm.DB, config *utils.Config) *UploadService {

	return &UploadService{

		db: db,

		config: config,
	}

}

func (s *UploadService) UploadFile(file *multipart.FileHeader, userID uint, deviceUID, description string) (*model.FileUpload, error) {

	// 生成唯一文件名

	ext := filepath.Ext(file.Filename)

	uniqueID := uuid.New().String()

	fileName := fmt.Sprintf("%s%s", uniqueID, ext)

	filePath := filepath.Join(s.config.Upload.Path, fileName)

	// 确保上传目录存在

	if err := os.MkdirAll(s.config.Upload.Path, 0755); err != nil {

		return nil, err

	}

	// 保存文件

	src, err := file.Open()

	if err != nil {

		return nil, err

	}

	defer src.Close()

	dst, err := os.Create(filePath)

	if err != nil {

		return nil, err

	}

	defer dst.Close()

	if _, err = io.Copy(dst, src); err != nil {

		return nil, err

	}

	// 如果提供了设备UID，获取设备型号

	var deviceModel string

	if deviceUID != "" {

		var device model.Device

		if err := s.db.Where("uid = ?", deviceUID).First(&device).Error; err == nil {

			deviceModel = device.DeviceModel

		}

	}

	// 创建数据库记录

	upload := &model.FileUpload{

		FileName: file.Filename,

		FilePath: filePath,

		FileSize: file.Size,

		FileType: strings.ToLower(ext),

		UploadedBy: userID,

		DeviceUID: deviceUID,

		DeviceModel: deviceModel,

		Description: description,
	}

	if err := s.db.Create(upload).Error; err != nil {

		os.Remove(filePath)

		return nil, err

	}

	return upload, nil

}

func (s *UploadService) DownloadFile(id uint) (*model.FileUpload, error) {

	var file model.FileUpload

	if err := s.db.First(&file, id).Error; err != nil {

		return nil, err

	}

	return &file, nil

}

func (s *UploadService) DeleteFile(id uint, userID uint) error {

	var file model.FileUpload

	if err := s.db.First(&file, id).Error; err != nil {

		return err

	}

	if file.UploadedBy != userID {

		return errors.New("无权删除此文件")

	}

	if err := os.Remove(file.FilePath); err != nil && !os.IsNotExist(err) {

		return err

	}

	return s.db.Delete(&file).Error

}

func (s *UploadService) GetDeviceFiles(deviceUID string) ([]model.FileUpload, error) {

	var files []model.FileUpload

	err := s.db.Where("device_uid = ?", deviceUID).Find(&files).Error

	return files, err

}

func (s *UploadService) UploadChunk(

	file *multipart.FileHeader,

	fileHash string,

	chunkNumber int,

	totalChunks int,

	totalSize int64,

	filename string,

	userID uint,

	deviceUID string,

) error {

	// 创建分片存储目录

	chunkDir := filepath.Join(s.config.Upload.Path, "chunks", fileHash)

	if err := os.MkdirAll(chunkDir, 0755); err != nil {

		return err

	}

	// 保存分片文件

	chunkPath := filepath.Join(chunkDir, fmt.Sprintf("%d", chunkNumber))

	src, err := file.Open()

	if err != nil {

		return err

	}

	defer src.Close()

	dst, err := os.Create(chunkPath)

	if err != nil {

		return err

	}

	defer dst.Close()

	if _, err = io.Copy(dst, src); err != nil {

		return err

	}

	// 记录分片信息

	chunk := model.UploadChunk{

		FileHash: fileHash,

		ChunkNumber: chunkNumber,

		ChunkSize: file.Size,

		ChunkPath: chunkPath,

		TotalChunks: totalChunks,

		TotalSize: totalSize,

		Filename: filename,

		FileType: strings.ToLower(filepath.Ext(filename)),

		UploadedBy: userID,

		DeviceUID: deviceUID,
	}

	return s.db.Create(&chunk).Error

}

func (s *UploadService) CheckUploadStatus(fileHash string) (bool, error) {

	var chunks []model.UploadChunk

	if err := s.db.Where("file_hash = ?", fileHash).Find(&chunks).Error; err != nil {

		return false, err

	}

	if len(chunks) == 0 {

		return false, nil

	}

	totalChunks := chunks[0].TotalChunks

	return len(chunks) == totalChunks, nil

}

func (s *UploadService) MergeChunks(fileHash string) (*model.FileUpload, error) {

	var chunks []model.UploadChunk

	if err := s.db.Where("file_hash = ?", fileHash).Find(&chunks).Error; err != nil {

		return nil, err

	}

	if len(chunks) == 0 {

		return nil, errors.New("未找到文件分片")

	}

	if len(chunks) != chunks[0].TotalChunks {

		return nil, errors.New("文件分片不完整")

	}

	// 按分片序号排序

	sort.Slice(chunks, func(i, j int) bool {

		return chunks[i].ChunkNumber < chunks[j].ChunkNumber

	})

	// 创建最终文件

	finalPath := filepath.Join(s.config.Upload.Path, fmt.Sprintf("%s%s", uuid.New().String(), chunks[0].FileType))

	finalFile, err := os.Create(finalPath)

	if err != nil {

		return nil, err

	}

	defer finalFile.Close()

	// 合并分片

	hash := sha256.New()

	for _, chunk := range chunks {

		chunkFile, err := os.Open(chunk.ChunkPath)

		if err != nil {

			return nil, err

		}

		if _, err = io.Copy(finalFile, chunkFile); err != nil {

			chunkFile.Close()

			return nil, err

		}

		if _, err = io.Copy(hash, chunkFile); err != nil {

			chunkFile.Close()

			return nil, err

		}

		chunkFile.Close()

		os.Remove(chunk.ChunkPath) // 删除已合并的分片

	}

	// 验证文件哈希

	if hex.EncodeToString(hash.Sum(nil)) != fileHash {

		os.Remove(finalPath)

		return nil, errors.New("文件哈希验证失败")

	}

	// 创建文件记录

	upload := &model.FileUpload{

		FileName: chunks[0].Filename,

		FilePath: finalPath,

		FileSize: chunks[0].TotalSize,

		FileType: chunks[0].FileType,

		UploadedBy: chunks[0].UploadedBy,

		DeviceUID: chunks[0].DeviceUID,
	}

	if err := s.db.Create(upload).Error; err != nil {

		os.Remove(finalPath)

		return nil, err

	}

	// 清理分片记录

	s.db.Where("file_hash = ?", fileHash).Delete(&model.UploadChunk{})

	os.RemoveAll(filepath.Dir(chunks[0].ChunkPath))

	return upload, nil

}

func (s *UploadService) CleanupExpiredChunks() error {

	expireTime := time.Now().Add(-24 * time.Hour)

	var expiredChunks []model.UploadChunk

	if err := s.db.Where("completed = ? AND created_at < ?", false, expireTime).Find(&expiredChunks).Error; err != nil {

		return err

	}

	for _, chunk := range expiredChunks {

		os.Remove(chunk.ChunkPath)

		if len(chunk.ChunkPath) > 0 {

			chunkDir := filepath.Dir(chunk.ChunkPath)

			os.RemoveAll(chunkDir)

		}

	}

	return s.db.Unscoped().Where("completed = ? AND created_at < ?", false, expireTime).Delete(&model.UploadChunk{}).Error

}