package tool

import (
	"crypto/md5"
	"fmt"
	"io"
	"os"
	"path/filepath"
)

// FileMD5 calculate file md5
//   - if file not exist, return ""
//   - if _path is dir, return ""
func FileMD5(_path string) string {
	// 检查文件是否存在
	fileInfo, err := os.Stat(_path)
	if err != nil {
		if os.IsNotExist(err) {
			return ""
		}
		// 其他错误也返回空字符串
		return ""
	}

	// 检查是否是目录
	if fileInfo.IsDir() {
		return ""
	}

	// 打开文件
	file, err := os.Open(_path)
	if err != nil {
		return ""
	}
	defer file.Close()

	// 创建MD5哈希计算器
	hash := md5.New()

	// 将文件内容复制到哈希计算器
	if _, err := io.Copy(hash, file); err != nil {
		return ""
	}

	// 计算并返回MD5哈希值（十六进制字符串）
	return fmt.Sprintf("%x", hash.Sum(nil))
}

// CopyFile copies a file from src to dst.
// Returns an error if source/destination are the same, source isn't a regular file,
// or any step in the copy process fails.
func CopyFile(src, dst string) error {
	// Open source file
	srcFile, err := os.Open(src)
	if err != nil {
		return fmt.Errorf("failed to open source: %w", err)
	}
	defer srcFile.Close()

	// Get source file metadata
	srcInfo, err := srcFile.Stat()
	if err != nil {
		return fmt.Errorf("failed to get source info: %w", err)
	}

	// Verify source is a regular file
	if !srcInfo.Mode().IsRegular() {
		return fmt.Errorf("source is not a regular file")
	}

	// Check if source and destination are the same file
	if same, err := sameFile(src, dst, srcInfo); same {
		return fmt.Errorf("source and destination are the same file")
	} else if err != nil {
		return err
	}

	// Create destination directory structure
	if err := os.MkdirAll(filepath.Dir(dst), 0755); err != nil {
		return fmt.Errorf("failed to create destination directory: %w", err)
	}

	// Create destination file with source permissions
	dstFile, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, srcInfo.Mode())
	if err != nil {
		return fmt.Errorf("failed to create destination: %w", err)
	}

	// Copy contents and handle destination close errors
	_, err = io.Copy(dstFile, srcFile)
	if closeErr := dstFile.Close(); closeErr != nil && err == nil {
		err = fmt.Errorf("failed to close destination: %w", closeErr)
	}
	if err != nil {
		return fmt.Errorf("copy failed: %w", err)
	}

	return nil
}

// sameFile checks if src and dst refer to the same file using device/inode numbers
func sameFile(src, dst string, srcInfo os.FileInfo) (bool, error) {
	dstInfo, err := os.Stat(dst)
	if os.IsNotExist(err) {
		return false, nil // Destination doesn't exist
	}
	if err != nil {
		return false, err // Other errors
	}
	return os.SameFile(srcInfo, dstInfo), nil
}

func CopyDir(src, dst string) error {
	// todo: copy src dir to dst dir recursively
	// if dst is not exist, create it
	// if file exist, overwrite it
	srcInfo, err := os.Stat(src)
	if err != nil {
		return fmt.Errorf("stat src dir failed: %w", err)
	}
	if !srcInfo.IsDir() {
		return fmt.Errorf("source is not a directory")
	}

	// Create destination directory if it does not exist
	if err := os.MkdirAll(dst, srcInfo.Mode()); err != nil {
		return fmt.Errorf("failed to create destination directory: %w", err)
	}

	entries, err := os.ReadDir(src)
	if err != nil {
		return fmt.Errorf("failed to read source directory: %w", err)
	}

	for _, entry := range entries {
		srcPath := filepath.Join(src, entry.Name())
		dstPath := filepath.Join(dst, entry.Name())

		info, err := entry.Info()
		if err != nil {
			return fmt.Errorf("failed to get info for %s: %w", srcPath, err)
		}

		if info.IsDir() {
			// Recursively copy subdirectory
			if err := CopyDir(srcPath, dstPath); err != nil {
				return err
			}
		} else {
			// Copy file, overwrite if exists
			if err := CopyFile(srcPath, dstPath); err != nil {
				return err
			}
		}
	}
	return nil
}