package storage

import (
	"crypto/md5"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"mime/multipart"
	"os"
	"path/filepath"
	"time"

	"github.com/gofiber/fiber/v3"
)

type Uploader struct {
	tmpDir      string
	chunkPath   string
	fileName    string
	chunkNumber int
	totalChunks int
	fileMD5     string

	dst       string
	ext       string
	finalPath string
}

type UploadedFile struct {
	ID       int64  `json:"id"`
	Hash     string `json:"hash"`
	Name     string `json:"name"`
	Size     int64  `json:"size"`
	MimeType string `json:"type"`
	Path     string `json:"path"`
	Preview  string `json:"preview"`
}

func NewUploader(fileName string, chunkNumber, totalChunks int, fileMD5 string) (*Uploader, error) {
	// 使用MD5创建唯一的临时目录
	tempDir := filepath.Join(os.TempDir(), fileMD5)
	if err := os.MkdirAll(tempDir, 0o755); err != nil {
		return nil, err
	}

	return &Uploader{
		tmpDir:      filepath.Join(os.TempDir(), fileMD5),
		chunkPath:   filepath.Join(os.TempDir(), fileMD5, fmt.Sprintf("chunk_%d", chunkNumber)),
		fileName:    fileName,
		chunkNumber: chunkNumber,
		totalChunks: totalChunks,
		fileMD5:     fileMD5,
		ext:         filepath.Ext(fileName),
		finalPath:   filepath.Join(os.TempDir(), fileMD5+filepath.Ext(fileName)),
	}, nil
}

func (up *Uploader) Save(ctx fiber.Ctx, file *multipart.FileHeader) (*UploadedFile, error) {
	if up.chunkNumber != up.totalChunks-1 {
		return nil, ctx.SaveFile(file, up.chunkPath)
	}

	// 如果是最后一个分片
	// 生成唯一的文件存储路径
	storageDir := filepath.Join(up.dst, time.Now().Format("2006/01/02"))
	if err := os.MkdirAll(storageDir, 0o755); err != nil {
		os.RemoveAll(filepath.Join(os.TempDir(), up.fileMD5))
		return nil, err
	}

	// 计算所有分片的实际大小总和
	totalSize, err := calculateTotalSize(up.tmpDir, up.totalChunks)
	if err != nil {
		os.RemoveAll(up.tmpDir)
		return nil, fmt.Errorf("计算文件大小失败: %w", err)
	}

	// 合并文件
	if err := combineChunks(up.tmpDir, up.finalPath, up.totalChunks); err != nil {
		os.RemoveAll(up.tmpDir)
		return nil, fmt.Errorf("合并文件失败: %w", err)
	}

	// 验证MD5
	calculatedMD5, err := calculateFileMD5(up.finalPath)
	if err != nil || calculatedMD5 != up.fileMD5 {
		os.RemoveAll(up.tmpDir)
		os.Remove(up.finalPath)
		return nil, errors.New("文件MD5验证失败")
	}

	// 清理临时目录
	os.RemoveAll(up.tmpDir)

	return &UploadedFile{
		Hash:     calculatedMD5,
		Name:     up.fileName,
		Path:     up.finalPath,
		Size:     totalSize,
		MimeType: file.Header.Get("Content-Type"),
	}, nil
}

// 计算所有分片的实际大小总和
func calculateTotalSize(tempDir string, totalChunks int) (int64, error) {
	var totalSize int64
	for i := 0; i < totalChunks; i++ {
		chunkPath := filepath.Join(tempDir, fmt.Sprintf("chunk_%d", i))
		info, err := os.Stat(chunkPath)
		if err != nil {
			return 0, err
		}
		totalSize += info.Size()
	}
	return totalSize, nil
}

func combineChunks(tempDir, finalPath string, totalChunks int) error {
	finalFile, err := os.Create(finalPath)
	if err != nil {
		return err
	}
	defer finalFile.Close()

	for i := 0; i < totalChunks; i++ {
		chunkPath := fmt.Sprintf("%s/chunk_%d", tempDir, i)
		chunk, err := os.ReadFile(chunkPath)
		if err != nil {
			return err
		}
		if _, err := finalFile.Write(chunk); err != nil {
			return err
		}
	}

	return nil
}

func calculateFileMD5(filePath string) (string, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return "", err
	}
	defer file.Close()

	hash := md5.New()
	if _, err := io.Copy(hash, file); err != nil {
		return "", err
	}

	return hex.EncodeToString(hash.Sum(nil)), nil
}