//go:build windows

package selfupdate

import (
	"os"
	"path/filepath"
)

// swap replaces target with newPath. Windows cannot rename a file onto
// a running executable, but it can rename the running executable out of
// the way first: move target -> target.old, then move new -> target.
// target.old is removed best-effort; if Windows holds it open, the file
// remains and the caller should print a one-line hint.
func swap(newPath, target string) error {
	info, err := os.Stat(target)
	if err != nil {
		return err
	}
	dir := filepath.Dir(target)
	tmp, err := os.CreateTemp(dir, ".eeco-new-*")
	if err != nil {
		return err
	}
	tmpName := tmp.Name()
	if err := tmp.Close(); err != nil {
		os.Remove(tmpName)
		return err
	}
	if err := copyFile(newPath, tmpName); err != nil {
		os.Remove(tmpName)
		return err
	}
	if err := os.Chmod(tmpName, info.Mode()); err != nil {
		os.Remove(tmpName)
		return err
	}
	old := target + ".old"
	_ = os.Remove(old)
	if err := os.Rename(target, old); err != nil {
		os.Remove(tmpName)
		return err
	}
	if err := os.Rename(tmpName, target); err != nil {
		_ = os.Rename(old, target)
		os.Remove(tmpName)
		return err
	}
	_ = os.Remove(old)
	return nil
}