package local

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

func (c *Client) resolveObjectPath(objectKey string) (string, error) {
	if strings.TrimSpace(objectKey) == "" || filepath.IsAbs(objectKey) || strings.Contains(objectKey, "\\") {
		return "", fmt.Errorf("对象键不是安全的相对路径")
	}
	for _, segment := range strings.Split(objectKey, "/") {
		if segment == "" || segment == "." || segment == ".." {
			return "", fmt.Errorf("对象键包含无效路径段")
		}
	}
	target := filepath.Join(c.objectsPath, filepath.FromSlash(objectKey))
	relative, err := filepath.Rel(c.objectsPath, target)
	if err != nil || relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
		return "", fmt.Errorf("对象路径超出存储目录")
	}
	if err := c.ensureNoSymlink(filepath.Dir(target), c.objectsPath); err != nil {
		return "", err
	}
	return target, nil
}

func (c *Client) ensureDirectory(directory string) error {
	if err := os.MkdirAll(directory, 0o750); err != nil {
		return fmt.Errorf("创建本地存储目录 %s: %w", directory, err)
	}
	if err := c.ensureNoSymlink(directory, c.rootPath); err != nil {
		return err
	}
	return os.Chmod(directory, 0o750)
}

func (c *Client) ensureNoSymlink(target, boundary string) error {
	target = filepath.Clean(target)
	boundary = filepath.Clean(boundary)
	relative, err := filepath.Rel(boundary, target)
	if err != nil || relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
		return fmt.Errorf("路径超出本地存储边界")
	}
	current := boundary
	if relative == "." {
		return rejectSymlink(current)
	}
	if err := rejectSymlink(current); err != nil {
		return err
	}
	for _, segment := range strings.Split(relative, string(filepath.Separator)) {
		current = filepath.Join(current, segment)
		info, statErr := os.Lstat(current)
		if os.IsNotExist(statErr) {
			continue
		}
		if statErr != nil {
			return fmt.Errorf("检查路径 %s: %w", current, statErr)
		}
		if info.Mode()&os.ModeSymlink != 0 {
			return fmt.Errorf("本地存储路径不允许符号链接: %s", current)
		}
	}
	return nil
}

func rejectSymlink(path string) error {
	info, err := os.Lstat(path)
	if err != nil {
		return err
	}
	if info.Mode()&os.ModeSymlink != 0 {
		return fmt.Errorf("本地存储路径不允许符号链接: %s", path)
	}
	return nil
}